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Sample records for crystal elastomer ordering

  1. Thermomechanical modeling of the thermo-order-mechanical coupling behaviors in liquid crystal elastomers

    Science.gov (United States)

    Jin, Lihua; Zeng, Zhi; Huo, Yongzhong

    2010-11-01

    Liquid crystal elastomer is a kind of anisotropic polymeric material, with complicated micro-structures and thermo-order-mechanical coupling behaviors. In this paper, we propose a method to systematically model these coupling behaviors. We derive the constitutive model in full tensor structure according to the Clausius-Duhem inequality. Two of the constitutive equations represent the mechanical equilibrium and the other two represent the phase equilibrium. Choosing the total free energy as the combination of the neo-classical free energy and the Landau-de Gennes nematic free energy, we obtain the Cauchy stress-deformation gradient relation and the order-mechanical coupling equations. We find the analytical homogeneous solutions of the deformation for the typical mechanical loadings, such as uniaxial stretch, and simple shear in any directions. We also compare the compression behavior of prolate liquid crystal elastomers with the stretch behavior of oblate liquid crystal elastomers. As a result, the stress, strain, temperature, order parameter, biaxiality and the direction of the director of liquid crystal elastomers couple with each other. When the prolate liquid crystal elastomer sample is stretched in the direction parallel to its director, the deviatoric stress makes the mesogens more order and increase the transition temperature. When the sample is sheared or stretched in the direction non-parallel to the director, the director of the liquid crystal elastomer will rotate, and the biaxiality will be induced. Because of the order-mechanical coupling, under infinitesimal deformation, liquid crystal elastomer has anisotropic Young's modulus and zero shear modulus in the direction parallel or perpendicular to the director. While for the oblate liquid crystal elastomers, the stretch parallel to the director will cause the rotation of the director and induce the biaxiality.

  2. Liquid-crystal order during synthesis affects main-chain liquid-crystal elastomer behavior.

    Science.gov (United States)

    Traugutt, N A; Volpe, R H; Bollinger, M S; Saed, M O; Torbati, A H; Yu, K; Dadivanyan, Natalia; Yakacki, C M

    2017-10-11

    This study presents the first direct comparison of the influence of liquid-crystal order during synthesis on the thermo-mechanical behaviors of main-chain liquid-crystal elastomers (LCEs) in thiol-acrylate networks. Six polydomain nematic elastomer (PNE) chemistries were compared directly by synthesizing with the mesogens in either an isotropic state (i-PNE) or a nematic state (n-PNE). The i-PNE networks were created in the presence of solvent, which disrupted any liquid-crystal order during network formation. Conversely, the n-PNE networks were created without the presence of solvent below the isotropic transition (TNI). Differential scanning calorimetry (DSC) was first performed, and it showed that i-PNE networks experienced a clearly defined nematic-to-isotropic transition upon heating, whereas the transition in n-PNE networks was unable to be identified, which may be the result of a nematic-to-paranematic phase transition. Dynamic mechanical analysis (DMA) tests revealed that while both networks maintained elevated loss tangent in the nematic region, only i-PNE networks prominently displayed dynamic soft elasticity behavior. The two-way shape switching behaviors of LCE networks were examined using actuation tests under a 100 kPa bias stress. It showed that the strain amplitude strongly depends on synthesis history; it ranges from 66% to 126% in i-PNE samples and 3% to 61% in n-PNE samples. To help interpret the different actuation strain behaviors between i-PNEs and n-PNEs, wide-angle X-ray scattering (WAXS) was then performed where the LCE samples were strained to 40%. The results showed that order parameter (S) in n-PNE samples (ranging from 0.37 to 0.50) is lower than that in i-PNE samples (0.54 for all cases), and the parameter decreased as the cross-linking density increased. The stress-strain behaviors of the LCE networks measured from uniaxial tension tests revealed that all i-PNE samples had a lower soft-elasticity plateau during loading compared to the

  3. Carbon nanotubes dispersed in liquid crystal elastomers

    Science.gov (United States)

    Yang, Yang; Ji, Yan

    Liquid crystal elastomers (LCEs), as the name indicates, unite the anisotropic order of liquid crystals and rubber elasticity of elastomers into polymer networks. One of the most notable features of LCEs is that properly aligned LCEs exhibit dramatic and reversible shape deformation (e.g. elongation-contraction) in response to various stimuli. In recent years, carbon nanotubes (CNTs) were introduced into LCEs. Besides enabling remote and spatial control of the actuation via light and electronic field, CNTs are also utilized to align mesogens as well as to improve the mechanical and electronic property of the composites. Some potential applications of CNT-LCE nanocomposites have been demonstrated. This chapter describes the preparation of CNT dispersed LCEs, new physical properties resulted from CNTs, their actuation and their proposed applications.

  4. Polymer-dispersed liquid crystal elastomers

    OpenAIRE

    Resetic, A; Milavec, J; B Zupancic; Domenici, V; Zalar, B.

    2016-01-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically siz...

  5. Polymer-dispersed liquid crystal elastomers

    Science.gov (United States)

    Rešetič, Andraž; Milavec, Jerneja; Zupančič, Blaž; Domenici, Valentina; Zalar, Boštjan

    2016-10-01

    The need for mechanical manipulation during the curing of conventional liquid crystal elastomers diminishes their applicability in the field of shape-programmable soft materials and future applications in additive manufacturing. Here we report on polymer-dispersed liquid crystal elastomers, novel composite materials that eliminate this difficulty. Their thermal shape memory anisotropy is imprinted by curing in external magnetic field, providing for conventional moulding of macroscopically sized soft, thermomechanically active elastic objects of general shapes. The binary soft-soft composition of isotropic elastomer matrix, filled with freeze-fracture-fabricated, oriented liquid crystal elastomer microparticles as colloidal inclusions, allows for fine-tuning of thermal morphing behaviour. This is accomplished by adjusting the concentration, spatial distribution and orientation of microparticles or using blends of microparticles with different thermomechanical characteristics. We demonstrate that any Gaussian thermomechanical deformation mode (bend, cup, saddle, left and right twist) of a planar sample, as well as beat-like actuation, is attainable with bilayer microparticle configurations.

  6. Molecular Models of Liquid Crystal Elastomers

    Science.gov (United States)

    Rajshekhar

    Liquid crystal elastomers combine the elastic properties of conventional rubbers with the optical properties of liquid crystals. This dual nature gives rise to unusual physical properties, including the stress induced transition from a polydomain state, consisting of multiple nematic regions with independent orientations, to a monodomain state consisting of a single nematic region with a uniform director. We propose several molecular-scale coarse-grained models of liquid crystal elastomers with varying degrees of resolution. The models employ the Gay-Berne soft potential, and exhibit the chain connectivity of a diamond network. Simulation results show that these models are able to capture the polydomain state exhibited by liquid crystal elastomers in the absence of any external stress. When subjected to uniaxial stress, our models exhibit a polydomain to monodomain transition. We explain that the polydomain state occurs through the aggregation of liquid crystal molecules assisted by crosslinking sites, and conclude that the transition mechanism to the monodomain state is based on the reorientation of nematic domains along the direction of applied stress. Our modeling efforts are primarily focused on three models. The first two models consider the effects of rigid and flexible crosslinkers in liquid crystal elastomers with a diamond topology for chain connectivity. The third model deviates from the diamond network topology and adopts a random network topology.

  7. Beam steering by liquid crystal elastomer fibres.

    Science.gov (United States)

    Nocentini, S; Martella, D; Wiersma, D S; Parmeggiani, C

    2017-11-22

    The problem of utilizing a laser beam as an information vehicle and dividing it into different channels is an open problem in the telecommunication field. The switching of a signal into different ports has been demonstrated, to date, by employing complex devices and mechanisms such as the electro optic effect, microelectromechanical system (MEMS) mirrors, or liquid crystal-based spatial light modulators (SLMs). We present here a simple device, namely a mirror held by a liquid crystal elastomer (LCE) fibre, as an optically and remotely driven beam steerer. In fact, a considered signal (laser beam) can be addressed in every in-plane direction by controlling the fibre and mirror rotation, i.e., the deflected probe beam angle. Such movement is possible due to the preparation of LCE fibres able to rotate and contract under a selective light stimulus. By adjusting the irradiation stimulus power, elastic fibres are able to rotate with a specific angle, performing more than one complete revolution around their axis. The described movement is perfectly reversible as soon as the stimulus is removed.

  8. Artificial muscles based on liquid crystal elastomers.

    Science.gov (United States)

    Li, Min-Hui; Keller, Patrick

    2006-10-15

    This paper presents our results on liquid crystal (LC) elastomers as artificial muscle, based on the ideas proposed by de Gennes. In the theoretical model, the material consists of a repeated series of main-chain nematic LC polymer blocks, N, and conventional rubber blocks, R, based on the lamellar phase of a triblock copolymer RNR. The motor for the contraction is the reversible macromolecular shape change of the chain, from stretched to spherical, that occurs at the nematic-to-isotropic phase transition in the main-chain nematic LC polymers. We first developed a new kind of muscle-like material based on a network of side-on nematic LC homopolymers. Side-on LC polymers were used instead of main-chain LC polymers for synthetic reasons. The first example of these materials was thermo-responsive, with a typical contraction of around 35-45% and a generated force of around 210 kPa. Subsequently, a photo-responsive material was developed, with a fast photochemically induced contraction of around 20%, triggered by UV light. We then succeeded in preparing a thermo-responsive artificial muscle, RNR, with lamellar structure, using a side-on nematic LC polymer as N block.Micrometre-sized artificial muscles were also prepared. This paper illustrates the bottom-up design of stimuli-responsive materials, in which the overall material response reflects the individual macromolecular response, using LC polymer as building block.

  9. Dynamic self-stiffening in liquid crystal elastomers

    Science.gov (United States)

    Agrawal, Aditya; Chipara, Alin C.; Shamoo, Yousif; Patra, Prabir K.; Carey, Brent J.; Ajayan, Pulickel M.; Chapman, Walter G.; Verduzco, Rafael

    2013-04-01

    Biological tissues have the remarkable ability to remodel and repair in response to disease, injury and mechanical stresses. Synthetic materials lack the complexity of biological tissues, and man-made materials that respond to external stresses through a permanent increase in stiffness are uncommon. Here we report that polydomain nematic liquid crystal elastomers increase in stiffness by up to 90% when subjected to a low-amplitude (5%), repetitive (dynamic) compression. Elastomer stiffening is influenced by liquid crystal content, the presence of a nematic liquid crystal phase and the use of a dynamic as opposed to static deformation. Through rheological and X-ray diffraction measurements, stiffening can be attributed to a mobile nematic director, which rotates in response to dynamic compression. Stiffening under dynamic compression has not been previously observed in liquid crystal elastomers and may be useful for the development of self-healing materials or for the development of biocompatible, adaptive materials for tissue replacement.

  10. Self-assembly of nematic liquid crystal elastomer filaments

    Science.gov (United States)

    Wei, Wei-Shao; Xia, Yu; Yang, Shu; Yodh, A. G.

    In this work we investigate the self-assembly of nematic liquid crystal polymer (NLCP) filaments and their corresponding cross-linked elastomer structures. Specifically, by fine-tuning surfactant concentration, prepolymer chain length, and temperature within a background aqueous phase we can generate filaments composed of oligomerized LC monomers. Filaments with narrowly dispersed diameters ranging from one hundred nanometers to a few micrometers can be obtained. Using polarization optical microscopy, we show that the nematic LCs within the filaments have an escaped radial structure. After photo-cross-linking, nematic liquid crystal elastomer filaments are obtained with well-maintained directors and smooth surface structure. Since these materials are elastomers, the size and mechanical and optical response of the filaments can be ''tuned'' near the nematic to isotropic phase transition temperature. This work is supported by NSF DMR16-07378, PENN MRSEC Grant DMR11-20901, and NASA Grant NNX08AO0G.

  11. Liquid Crystal Elastomer Actuators from Anisotropic Porous Polymer Template.

    Science.gov (United States)

    Wang, Qian; Yu, Li; Yu, Meina; Zhao, Dongyu; Song, Ping; Chi, Hun; Guo, Lin; Yang, Huai

    2017-08-01

    Controlling self-assembly behaviors of liquid crystals is a fundamental issue for designing them as intelligent actuators. Here, anisotropic porous polyvinylidene fluoride film is utilized as a template to induce homogeneous alignment of liquid crystals. The mechanism of liquid crystal alignment induced by anisotropic porous polyvinylidene fluoride film is illustrated based on the relationship between the alignment behavior of liquid crystals and surface microstructure of anisotropic polyvinylidene fluoride film. Liquid crystal elastomer actuators with fast responsiveness, large strain change, and reversible actuation behaviors are achieved by the photopolymerization of liquid crystal monomer in liquid crystal cells coated with anisotropic porous films. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Thermal tuning of a silicon photonic crystal cavity infilled with an elastomer

    NARCIS (Netherlands)

    Erdamar, A.K.; Van Leest, M.M.; Picken, S.J.; Caro, J.

    2011-01-01

    Thermal tuning of the transmission of an elastomer infilled photonic crystal cavity is studied. An elastomer has a thermal expansion-induced negative thermo-optic coefficient that leads to a strong decrease of the refractive index upon heating. This property makes elastomer highly suitable for

  13. Localized soft elasticity in liquid crystal elastomers (POSTPRINT)

    Science.gov (United States)

    2016-02-23

    AFRL-RX-WP-JA-2016-0280 LOCALIZED SOFT ELASTICITY IN LIQUID CRYSTAL ELASTOMER (POSTPRINT) Taylor H. Ware, Andreas F. Shick, and...should be aware that notwithstanding any other provision of law , no person shall be subject to any penalty for failing to comply with a collection of...MM-YY) 2. REPORT TYPE 3. DATES COVERED (From - To) 11 August 2015 Interim 31 January 2014 – 11 July 2015 4. TITLE AND SUBTITLE LOCALIZED SOFT

  14. Band structures in the nematic elastomers phononic crystals

    Science.gov (United States)

    Yang, Shuai; Liu, Ying; Liang, Tianshu

    2017-02-01

    As one kind of new intelligent materials, nematic elastomers (NEs) represent an exciting physical system that combines the local orientational symmetry breaking and the entropic rubber elasticity, producing a number of unique physical phenomena. In this paper, the potential application of NEs in the band tuning is explored. The band structures in two kinds of NE phononic crystals (PCs) are investigated. Through changing NE intrinsic parameters, the influence of the porosity, director rotation and relaxation on the band structures in NE PCs are analyzed. This work is a meaningful try for application of NEs in acoustic field and proposes a new intelligent strategy in band turning.

  15. Numerical study of liquid crystal elastomers by a mixed finite element method

    KAUST Repository

    LUO, C.

    2011-08-22

    Liquid crystal elastomers present features not found in ordinary elastic materials, such as semi-soft elasticity and the related stripe domain phenomenon. In this paper, the two-dimensional Bladon-Terentjev-Warner model and the one-constant Oseen-Frank energy expression are combined to study the liquid crystal elastomer. We also impose two material constraints, the incompressibility of the elastomer and the unit director norm of the liquid crystal. We prove existence of minimiser of the energy for the proposed model. Next we formulate the discrete model, and also prove that it possesses a minimiser of the energy. The inf-sup values of the discrete linearised system are then related to the smallest singular values of certain matrices. Next the existence and uniqueness of the Lagrange multipliers associated with the two material constraints are proved under the assumption that the inf-sup conditions hold. Finally numerical simulations of the clamped-pulling experiment are presented for elastomer samples with aspect ratio 1 or 3. The semi-soft elasticity is successfully recovered in both cases. The stripe domain phenomenon, however, is not observed, which might be due to the relative coarse mesh employed in the numerical experiment. Possible improvements are discussed that might lead to the recovery of the stripe domain phenomenon. © Copyright Cambridge University Press 2011.

  16. Flexoelectricity of a Calamitic Liquid Crystal Elastomer Swollen with a Bent-core Liquid Crystal

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, M.; Verduzco, R; Gleeson, J; Sprunt, S; Jakli, A

    2009-01-01

    We have measured the electric current induced by mechanical distortion of a calamitic liquid crystal elastomer (LCE) swollen with a low molecular weight bent-core nematic (BCN) liquid crystal, and have determined, for the first time, the bend flexoelectric coefficient e{sub 3} of such a BCN-LCE composite. In one method, we utilize air-pressure to induce a mechanical bend deformation and flexoelectric polarization in a BCN-LCE film, and then measure the polarization current as a function of time. An alternative technique uses a rotary-motor driven scotch yoke to periodically flex the BCN-LCE; in this case, the magnitude and phase of the induced current are recorded via a lock-in amplifier. The flexoelectric coefficient, e{sub 3}, was found to be {approx}20 nC/cm{sup 2}, and is stable in magnitude from room temperature to {approx}65 C. It is about one third the value measured in samples of the pure BCN; this fraction corresponds closely to the molar concentration of BCN in the LCE. The flexoelectric current increases linearly with the magnitude of the bend deformation and decays with frequency. These observations indicate a promising way forward towards producing very low-cost, self-standing, rugged electromechanical energy conversion devices.

  17. Topology optimization for the design of folding liquid crystal elastomer actuators.

    Science.gov (United States)

    Fuchi, Kazuko; Ware, Taylor H; Buskohl, Philip R; Reich, Gregory W; Vaia, Richard A; White, Timothy J; Joo, James J

    2015-10-07

    Aligned liquid crystal elastomers (LCEs) are capable of undergoing large reversible shape change in response to thermal stimuli and may act as actuators for many potential applications such as self-assembly and deployment of micro devices. Recent advances in LCE patterning tools have demonstrated sub-millimetre control of director orientation, enabling the preparation of materials with arbitrarily complex director fields. However, without design tools to connect the 2D director pattern with the activated 3D shape, LCE design relies on intuition and trial and error. Here we present a design methodology to generate reliable folding in monolithic LCEs designed with topology optimization. The distributions of order/disorder and director orientations are optimized so that the remotely actuated deformation closely matches a target deformation for origami folding. The optimal design exhibits a strategy to counteract the mechanical frustration that may lead to an undesirable deformation, such as anti-clastic bending. Multi-hinge networks were developed using insights from the optimal hinge designs and were demonstrated through the fabrication and reversible actuation of a self-folding box. Topology optimization provides an important step towards leveraging the opportunities afforded by LCE patterning into functional designs.

  18. Modeling Defects, Shape Evolution, and Programmed Auto-origami in Liquid Crystal Elastomers

    Directory of Open Access Journals (Sweden)

    Andrew eKonya

    2016-06-01

    Full Text Available Liquid crystal elastomers represent a novel class of programmable shape-transforming materials whose shape change trajectory is encoded in the material’s nematic director field. Using three-dimensional nonlinear finite element elastodynamics simulation, we model a variety of different actuation geometries and device designs: thin films containing topological defects, patterns that induce formation of folds and twists, and a bas-relief structure. The inclusion of finite bending energy in the simulation model reveals features of actuation trajectory that may be absent when bending energy is neglected. We examine geometries with a director pattern uniform through the film thickness encoding multiple regions of positive Gaussian curvature. Simulations indicate that heating such a system uniformly produces a disordered state with curved regions emerging randomly in both directions due to the film’s up/down symmetry. By contrast, applying a thermal gradient by heating the material first on one side breaks up/down symmetry and results in a deterministic trajectory producing a more ordered final shape. We demonstrate that a folding zone design containing cut-out areas accommodates transverse displacements without warping or buckling; and demonstrate that bas-relief and more complex bent/twisted structures can be assembled by combining simple design motifs.

  19. Nanotube liquid crystal elastomers: photomechanical response and flexible energy conversion of layered polymer composites.

    Science.gov (United States)

    Fan, Xiaoming; King, Benjamin C; Loomis, James; Campo, Eva M; Hegseth, John; Cohn, Robert W; Terentjev, Eugene; Panchapakesan, Balaji

    2014-09-05

    Elastomeric composites based on nanotube liquid crystals (LCs) that preserve the internal orientation of nanotubes could lead to anisotropic physical properties and flexible energy conversion. Using a simple vacuum filtration technique of fabricating nanotube LC films and utilizing a transfer process to poly (dimethyl) siloxane wherein the LC arrangement is preserved, here we demonstrate unique and reversible photomechanical response of this layered composite to excitation by near infra-red (NIR) light at ultra-low nanotube mass fractions. On excitation by NIR photons, with application of small or large pre-strains, significant expansion or contraction of the sample occurs, respectively, that is continuously reversible and three orders of magnitude larger than in pristine polymer. Schlieren textures were noted in these LC composites confirming long range macroscopic nematic order of nanotubes within the composites. Order parameters of LC films ranged from S(optical) = 0.51-0.58 from dichroic measurements. Film concentrations, elastic modulus and photomechanical stress were all seen to be related to the nematic order parameter. For the same nanotube concentration, the photomechanical stress was almost three times larger for the self-assembled LC nanotube actuator compared to actuator based on randomly oriented carbon nanotubes. Investigation into the kinetics of photomechanical actuation showed variation in stretching exponent β with pre-strains, concentration and orientation of nanotubes. Maximum photomechanical stress of ∼ 0.5 MPa W(-1) and energy conversion of ∼ 0.0045% was achieved for these layered composites. The combination of properties, namely, optical anisotropy, reversible mechanical response to NIR excitation and flexible energy conversion all in one system accompanied with low cost makes nanotube LC elastomers important for soft photochromic actuation, energy conversion and photo-origami applications.

  20. Synthesis of Biocompatible Liquid Crystal Elastomer Foams as Cell Scaffolds for 3D Spatial Cell Cultures.

    Science.gov (United States)

    Prévôt, Marianne E; Ustunel, Senay; Bergquist, Leah E; Cukelj, Richard; Gao, Yunxiang; Mori, Taizo; Pauline, Lindsay; Clements, Robert J; Hegmann, Elda

    2017-04-11

    Here, we present a step-by-step preparation of a 3D, biodegradable, foam-like cell scaffold. These scaffolds were prepared by cross-linking star block co-polymers featuring cholesterol units as side-chain pendant groups, resulting in smectic-A (SmA) liquid crystal elastomers (LCEs). Foam-like scaffolds, prepared using metal templates, feature interconnected microchannels, making them suitable as 3D cell culture scaffolds. The combined properties of the regular structure of the metal foam and of the elastomer result in a 3D cell scaffold that promotes not only higher cell proliferation compared to conventional porous templated films, but also better management of mass transport (i.e., nutrients, gases, waste, etc.). The nature of the metal template allows for the easy manipulation of foam shapes (i.e., rolls or films) and for the preparation of scaffolds of different pore sizes for different cell studies while preserving the interconnected porous nature of the template. The etching process does not affect the chemistry of the elastomers, preserving their biocompatible and biodegradable nature. We show that these smectic LCEs, when grown for extensive time periods, enable the study of clinically relevant and complex tissue constructs while promoting the growth and proliferation of cells.

  1. Investigations on an integrated conducting nanoparticle-liquid crystal elastomer layer

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, Martin [J Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Zalar, Bostjan [J Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Remskar, Maja [J Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Kovac, Janez [J Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Finkelmann, Heino [Institute for Macromolecular Chemistry, University of Freiburg, Hermann-Staudinger-Haus, Stefan-Meier-Strasse 31, 79104, Freiburg (Germany); Zumer, Slobodan [J Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia)

    2007-10-17

    A process is outlined in which an existing liquid crystal elastomer (LCE) can be reprocessed from an insulating network to create an effectively conducting network. This is performed through the LCE volume expansion in a suitable solution containing conducting nanoparticles. Subsequent volume compression results in the formation of a conducting layer at the LCE surfaces. The swelling behaviour of the LCE is illustrated. Elemental composition analysis and electron imagining techniques show that the conducting layer is composed of conducting nanoparticles and LCE material. It was found that the integrated layer thickness and resistivity can be controlled through the LCE surface expansion ratio and conducting nanoparticle concentration, respectively.

  2. Control of Mechanical Properties of Thermoplastic Polyurethane Elastomers by Restriction of Crystallization of Soft Segment

    Directory of Open Access Journals (Sweden)

    Sadaharu Nakamura

    2010-12-01

    Full Text Available Mechanical properties of thermoplastic polyurethane elastomers based on either polyether or polycarbonate (PC-glycols, 4,4’-dipheylmethane diisocyanate (1,1’-methylenebis(4-isocyanatobenzene, 1,4-butanediol, were controlled by restriction of crystallization of polymer glycols. For the polyether glycol based-polyurethane elastomers (PUEs, poly(oxytetramethylene glycol (PTMG, and PTMG incorporating dimethyl groups (PTG-X and methyl side groups (PTG-L were employed as a polymer glycol. For the PC-glycol, the randomly copolymerized PC-glycols with hexamethylene (C6 and tetramethylene (C4 units between carbonate groups with various composition ratios (C4/C6 = 0/100, 50/50, 70/30 and 90/10 were employed. The degree of microphase separation and mechanical properties of both the PUEs were investigated using differential scanning calorimetry, dynamic viscoelastic property measurements and tensile testing. Mechanical properties could be controlled by changing the molar ratio of two different monomer components.

  3. Order, Disorder and Stretching of a Smectic Elastomer with ‘side-on’ Mesogenic Side Groups

    Energy Technology Data Exchange (ETDEWEB)

    de Jeu, W.; Komp, A; Obraztsov, E; Ostrovskii, B; Finkelmann, H

    2009-01-01

    We report an X-ray study of the order in a 'side-on' smectic-A elastomer in which both the polymer backbone and the mesogenic side groups are, on average, parallel to the smectic layer normal. The present system shows in all phases locally correlated structures as evidenced by systematic diffuse scattering at small angles, attributed to the fluorinated end groups of the mesogens. The elastomer shows order of the smectic layers over a limited range in spite of the relatively low crosslink concentration (4%). Upon stretching along the layer normal we find a linear increase of the smectic layer period for small loading (elastic regime). These changes parallel the stress variation for the elastic part of the macroscopic stress-strain curve and saturate at larger strains. The attendant increase in the width of the X-ray peaks indicates a decrease of the average domain dimensions. In the plastic regime no distortion of the smectic monodomain structure or layer rotation is observed. Instead the stress is relieved by 'melting' of the layer structure giving rise to a nematic-like state with short-range layer correlations: at the final stage about four smectic layers.

  4. Liquid crystal elastomer foams with elastic properties specifically engineered as biodegradable brain tissue scaffolds.

    Science.gov (United States)

    Prévôt, M E; Andro, H; Alexander, S L M; Ustunel, S; Zhu, C; Nikolov, Z; Rafferty, S T; Brannum, M T; Kinsel, B; Korley, L T J; Freeman, E J; McDonough, J A; Clements, R J; Hegmann, E

    2017-12-13

    Tissue regeneration requires 3-dimensional (3D) smart materials as scaffolds to promote transport of nutrients. To mimic mechanical properties of extracellular matrices, biocompatible polymers have been widely studied and a diverse range of 3D scaffolds have been produced. We propose the use of responsive polymeric materials to create dynamic substrates for cell culture, which goes beyond designing only a physical static 3D scaffold. Here, we demonstrated that lactone- and lactide-based star block-copolymers (SBCs), where a liquid crystal (LC) moiety has been attached as a side-group, can be crosslinked to obtain Liquid Crystal Elastomers (LCEs) with a porous architecture using a salt-leaching method to promote cell infiltration. The obtained SmA LCE-based fully interconnected-porous foams exhibit a Young modulus of 0.23 ± 0.07 MPa and a biodegradability rate of around 20% after 15 weeks both of which are optimized to mimic native environments. We present cell culture results showing growth and proliferation of neurons on the scaffold after four weeks. This research provides a new platform to analyse LCE scaffold-cell interactions where the presence of liquid crystal moieties promotes cell alignment paving the way for a stimulated brain-like tissue.

  5. Elastomer Change Out - Justification for minimizing the removal of elastomers in order to prevent cross contamination in a multiproduct facility.

    Science.gov (United States)

    Parks, Michael; O'Dwyer, Niamh; Bollinger, Jeremy; Johnson, Alan; Goss, Brian; Wyman, Ned; Arroyo, Adeyma; Wood, Joseph; Willison-Parry, Derek

    2017-09-19

    The primary objective of any Biopharmaceutical Product Changeover (PCO) program is to employ control strategies before, during, and after the manufacturing process, as well as from the beginning of the lifecycle approach for the equipment and validation, which will minimize the opportunity for cross- contamination when switching between products. Evaluation of the need for an Elastomer Change Out (ECO) should be considered as a segment of an overall changeover assessment. Lifecycle systems (e.g. Preventive Maintenance (PM), Cleanability Coupon Testing, Good Engineering Practices, etc.) and procedures should be in place and data should be generated demonstrating the soft parts do not harbor residues from the previous product campaign(s). The determination of whether or not to replace elastomers/soft parts should be made in the context of all of these systems along with the proper assessment of Risk. By understanding the actual value of ECO in terms of the overall PCO program, and the other systems and procedures that are in place that protect against cross contamination, the need for ECO for every product changeover is not necessary. The purpose of this paper is to review the practice of ECO at product changeover, evaluate the need for an ECO using a risk based approach, and provide rationale for justifying the reduction or elimination of ECO at product changeover. Copyright © 2017, Parenteral Drug Association.

  6. Polar Liquid Crystal Elastomers Cross Linked Far from Thermodynamic Phase Transitions: Dislocation Loops in Smectic Clusters

    Directory of Open Access Journals (Sweden)

    Yusril Yusuf

    2013-01-01

    Full Text Available Nematic networks with three different concentrations of polar and nonpolar mesogens and the same concentration of a novel cross-linking agent give rise to unusual liquid single crystal elastomers (LSCEs that are transparent monodomain nematic networks with smectic clusters. The largest spontaneous length change is observed in the sample with 70 mol% of the polar mesogen which also has the highest glass transition temperature and smectic clusters with a slowly increasing but nearly constant layer spacing on cooling from 90°C to 25°C. X-ray scattering intensity from smectic clusters with layer spacings that monotonically increase on cooling first increases to a maximum at T*~60∘C corresponding to clusters of about 30 layers. Below T∗, the scattering intensity decreases as the number of layers in a cluster decreases. To account for this surprising nonlinear behavior that correlates with nonlinear features of the networks’ macroscopic spontaneous shape change and birefringence, a model is proposed where dislocations form in the layers at T∗. Below T∗, more dislocations form to break down the layer structure. The possibility of dislocation formation at T∗ independent of mesogenic concentrations is attributed to a conformational change in the crosslinker which is present at the same concentration in the three LSCEs.

  7. Refractive and focusing behaviours of tunable sonic crystals with dielectric elastomer cylindrical actuators

    Energy Technology Data Exchange (ETDEWEB)

    Yang Wenpei; Wu Liangyu; Chen Lienwen [Department of Mechanical Engineering, National Cheng Kung University, Tainan 70101, Taiwan (China)], E-mail: chenlw@mail.ncku.edu.tw

    2008-07-07

    The refractive and focusing behaviours of a tunable sonic crystal (SC) consisting of air and dielectric elastomer (DE) cylindrical actuators are investigated. The refractive direction of the acoustic wave in SCs is predicted from the equivalent frequency surface obtained by the plane-wave expansion method. The inner and outer radii of the cylindrical actuators are increased with the electric field which is applied between the electrodes on the internal and external lateral surfaces. Therefore, the dispersion relation is varied with the geometric adjustment of the DE tubes and the refractions of acoustic wave in SCs are changed from positive to negative with the increase in the applied electric field. Based on the geometry adjustment of the cylindrical actuator, a tunable acoustic superlens could be proposed by a SC slab with DE tubes. The distance from the surface of the slab to the centre of the image spot can be changed with different electric fields. Thus, extensive applications of such a phenomenon to acoustic devices are anticipated.

  8. Self-Regulating Iris Based on Light-Actuated Liquid Crystal Elastomer.

    Science.gov (United States)

    Zeng, Hao; Wani, Owies M; Wasylczyk, Piotr; Kaczmarek, Radosław; Priimagi, Arri

    2017-08-01

    The iris, found in many animal species, is a biological tissue that can change the aperture (pupil) size to regulate light transmission into the eye in response to varying illumination conditions. The self-regulation of the eye lies behind its autofocusing ability and large dynamic range, rendering it the ultimate "imaging device" and a continuous source of inspiration in science. In optical imaging devices, adjustable apertures play a vital role as they control the light exposure, the depth of field, and optical aberrations of the systems. Tunable irises demonstrated to date require external control through mechanical actuation, and are not capable of autonomous action in response to changing light intensity without control circuitry. A self-regulating artificial iris would offer new opportunities for device automation and stabilization. Here, this paper reports the first iris-like, liquid crystal elastomer device that can perform automatic shape-adjustment by reacting to the incident light power density. Similar to natural iris, the device closes under increasing light intensity, and upon reaching the minimum pupil size, reduces the light transmission by a factor of seven. The light-responsive materials design, together with photoalignment-based control over the molecular orientation, provides a new approach to automatic, self-regulating optical systems based on soft smart materials. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Reprogrammable, Reprocessible, and Self-Healable Liquid Crystal Elastomer with Exchangeable Disulfide Bonds.

    Science.gov (United States)

    Wang, Zhijian; Tian, Hongmiao; He, Qiguang; Cai, Shengqiang

    2017-09-27

    A liquid crystal elastomer (LCE) can be regarded as an integration of mesogenic molecules into a polymer network. The LCE can generate large mechanical actuation when subjected to various external stimuli. Recently, it has been extensively explored to make artificial muscle and multifunctional devices. However, in the commonly adopted two-step crosslinking method for synthesizing monodomain LCEs, the LCE needs to be well-cross-linked in the first step before stretching, which increases the disorder of mesogenic molecules in the final state of the LCE and makes it very challenging to fabricate the LCE of complex shapes. In this article, we developed a new LCE with disulfide bonds, which can be reprogrammed from the polydomain state to the monodomain state either through heating or UV illumination, owing to the rearrangement of the polymer network induced by the metathesis reaction of disulfide bonds. In addition, the newly developed LCE can be easily reprocessed and self-healed by heating. Because of the excellent reprogrammability as well as reprocessability of the LCE, we further fabricated LCE-based active micropillar arrays through robust imprint lithography, which can be hardly achieved using the LCE prepared previously. Finally, we showed an excellent long-term durability of the newly developed LCE.

  10. Shear ordering in polymer photonic crystals.

    Science.gov (United States)

    Snoswell, D R E; Kontogeorgos, A; Baumberg, J J; Lord, T D; Mackley, M R; Spahn, P; Hellmann, G P

    2010-02-01

    Optical scattering spectra are recorded in situ on flowing colloidal polymeric nanocomposites which are sheared into photonic crystals at 150 degrees C using a high-pressure quartz-cell multipass rheometer. Broadband spectroscopy of the resonant Bragg scattering peak allows the direct observation of crystal formation and melting of monodisperse core-shell particles. A range of flow conditions of this solventless, highly viscous melt reveals four distinct regimes of crystal growth and decay which match a simple rheological model. Extraction of crystal thickness, order and lattice spacing are validated by one-dimensional electromagnetic simulations.

  11. Piezoresistivity and electro-thermomechanical degradation of a conducting layer of nanoparticles integrated at the liquid crystal elastomer surface

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, Martin; Zalar, Bostjan; Remskar, Maja; Zumer, Slobodan [J Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Finkelmann, Heino [Institute for Macromolecular Chemistry, University of Freiburg, D-79104 Freiburg (Germany)], E-mail: Martin.Chambers@ijs.si

    2008-04-16

    When a liquid crystal elastomer (LCE) is reprocessed with conducting nanosized particles a conducting layer can be formed at the LCE surfaces. Here, two different LCE materials and two different conducting carbon particles were used. These four reprocessed LCEs were investigated when subject to a thermal phase transition and mechanical extension. Here it is shown that the resistance change with strain ('piezoresistivity') for these reprocessed LCEs can be described through lattice percolation and geometrical changes in the LCE shape. The mechanisms and rate of degradation are also described for the conducting layer as a function of the number of electro-thermomechanical strain cycles performed.

  12. Phase-field-crystal model for ordered crystals.

    Science.gov (United States)

    Alster, Eli; Elder, K R; Hoyt, Jeffrey J; Voorhees, Peter W

    2017-02-01

    We describe a general method to model multicomponent ordered crystals using the phase-field-crystal (PFC) formalism. As a test case, a generic B2 compound is investigated. We are able to produce a line of either first-order or second-order order-disorder phase transitions, features that have not been incorporated in existing PFC approaches. Further, it is found that the only elastic constant for B2 that depends on ordering is C_{11}. This B2 model is then used to study antiphase boundaries (APBs). The APBs are shown to reproduce classical mean-field results. Dynamical simulations of ordering across small-angle grain boundaries predict that dislocation cores pin the evolution of APBs.

  13. New developments in 3D liquid crystal elastomers scaffolds for tissue engineering: from physical template to responsive substrate

    Science.gov (United States)

    Prévôt, Marianne E.; Bergquist, Leah E.; Sharma, Anshul; Mori, Taizo; Gao, Yungxiang; Bera, Tanmay; Zhu, Chenhui; Leslie, Michelle T.; Cukelj, Richard; Korley, LaShanda T. J.; Freeman, Ernest J.; McDonough, Jennifer A.; Clements, Robert J.; Hegmann, Elda

    2017-08-01

    We report here on cell growth and proliferation within a 3D architecture created using smectic liquid crystal elastomers (LCEs) leading to a responsive scaffold for tissue engineering. The investigated LCE scaffolds exhibit biocompatibility, controlled degradability, with mechanical properties and morphologies that can match development of the extracellular matrix. Moreover, the synthetic pathway and scaffold design offer a versatility of processing, allowing modifications of the surface such as adjusting the hydrophilic/hydrophobic balance and the mobility of the LC moieties to enhance the biomaterial performance. First, we succeeded in generating LCEs whose mechanical properties mimic muscle tissue. In films, our LCEs showed cell adhesion, proliferation, and alignment. We also achieved creating 3D LCE structures using either metallic template or microsphere scaffolds. Finally, we recorded a four times higher cell proliferation capability in comparison to conventional porous films and, most importantly, anisotropic cell growth that highlights the tremendous effect of liquid crystal moieties within LCEs on the cell environment.

  14. Optimizing the network topology of block copolymer liquid crystal elastomers for enhanced extensibility and toughness

    Science.gov (United States)

    Nowak, Christian; Escobedo, Fernando A.

    2017-08-01

    Molecular simulations are used to study the effect of synthesis conditions on the tensile response of liquid-crystalline elastomers formed by block copolymer chains. Remarkably, it is found that despite the significant presence of trapped entanglements, these networks can exhibit the sawtooth tensile response previously predicted for ideal unentangled networks. It is also found that the monomer concentration during crosslinking can be tuned to limit the extent of entanglements and inhomogeneities while also maximizing network extensibility. It is predicted that networks synthesized at a "critical" concentration will have the greatest toughness.

  15. Elastomers Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — Primary capabilities include: elastomer compounding in various sizes (micro, 3x5, 8x12, 8x15 rubber mills); elastomer curing and post curing (two 50-ton presses, one...

  16. Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers.

    Science.gov (United States)

    Xia, Yu; Lee, Elaine; Hu, Hao; Gharbi, Mohamed Amine; Beller, Daniel A; Fleischmann, Eva-Kristina; Kamien, Randall D; Zentel, Rudolf; Yang, Shu

    2016-05-18

    Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). Here, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau-de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. After curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (∼30%) when heated above the nematic to isotropic transition temperature.

  17. Ordering of crystal structure by ionizing radiation

    Science.gov (United States)

    Chernov, I. P.; Momontov, A. P.; Cherdantsev, P. A.; Chakhlov, B. V.

    1994-12-01

    We have studied the action of ionizing radiation on defect-containing semiconductor crystals, metals, and alloys. Using modern methods for investigation of solids, Rutherford back scattering of channeled charged particles, x-ray diffraction, electron microscopy, and also calorimetric methods, we have established: a) irradiation (by x-ray beams, gamma rays, and electrons) of metals and alloys with an equivalent radiation dose less than 105 J/kg and of semiconductor crystals with a dose less than 103 J/kg does not lead to additional accumulation of defects but conversely leads to elimination of defects and transition of the crystal to a more equilibrium state; b) ionization processes play a determining role in rearrangment of defects in crystals exhibiting both semiconductor and metallic conductivity. We show that rearrangment of the crystal occurs as a result of stored energy in the crystal which is liberated due to chain reactions of annihilation of defects, initiated by ionization. Transition of the crystal to the equilibrium state is accompanied by improvement of its physical properties.

  18. Precision-Trimming 2D Inverse-Opal Lattice on Elastomer to Ordered Nanostructures with Variable Size and Morphology.

    Science.gov (United States)

    Zhan, Haoran; Chen, Yanqiu; Liu, Yu; Lau, Woonming; Bao, Chao; Li, Minggan; Lu, Yunlong; Mei, Jun; Hui, David

    2017-05-23

    A low-cost and scalable method is developed for producing large-area elastomer surfaces having ordered nanostructures with a variety of lattice features controllable to nanometer precision. The method adopts the known technique of molding a PDMS precursor film with a close-packed monolayer of monodisperse submicron polystyrene beads on water to form an inverse-opal dimple lattice with the dimple size controlled by the bead selection and the dimple depth by the molding condition. The subsequent novel precision engineering of the inverse-opal lattice comprises trimming the PDMS precursor by a combination of polymer curing temperature/time and polymer dissolution parameters. The resultant ordered surface nanostructures, fabricated with an increasing degree of trimming, include (a) submicron hemispherical dimples with nanothin interdimple rims and walls; (b) nanocones with variable degrees of tip-sharpness by trimming off the top part of the nanothin interdimple walls; and (c) soup-plate-like submicron shallow dimples with interdimple rims and walls by anisotropically trimming off the nanocones and forming close-packed shallow dimples. As exemplars of industrial relevance of these lattice features, tunable Young's modulus and wettability are demonstrated.

  19. Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jin Hong [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; School of Chemical and Biological Engineering and Institute of Chemical Process, Seoul National University, 599 Gwanak-ro Gwanak-gu Seoul 151-742 South Korea; Han, Kee Sung [Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland WA 99354 USA; Lee, Je Seung [Department of Chemistry, Kyung Hee University, 26 Kyungheedae-ro Dongdaemun-gu Seoul 02447 South Korea; Lee, Albert S. [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; Park, Seo Kyung [Department of Chemistry, Kyung Hee University, 26 Kyungheedae-ro Dongdaemun-gu Seoul 02447 South Korea; Hong, Sung Yun [Department of Chemistry, Kyung Hee University, 26 Kyungheedae-ro Dongdaemun-gu Seoul 02447 South Korea; Lee, Jong-Chan [School of Chemical and Biological Engineering and Institute of Chemical Process, Seoul National University, 599 Gwanak-ro Gwanak-gu Seoul 151-742 South Korea; Mueller, Karl T. [Department of Chemistry, Pennsylvania State University, University Park PA 16802 USA; Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland WA 99352 USA; Hong, Soon Man [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; Nanomaterials Science and Engineering, University of Science and Technology, Gajeong-ro Yuseong-gu Daejeon 305-350 South Korea; Koo, Chong Min [Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil 5 Seongbuk-gu Seoul 136-791 South Korea; Nanomaterials Science and Engineering, University of Science and Technology, Gajeong-ro Yuseong-gu Daejeon 305-350 South Korea

    2016-09-08

    We investigated a novel ionic mixture of an imidazolium-based room temperature IL containing ethylene oxide functionalized phosphite anion and a lithium salt that self-assembles into a smectic-ordered IL crystal. The two key features in this work are the unique origin of the smectic order of the ionic mixtures and the facilitated ion transport behavior in the smectic ordered IL crystal. In fact, the IL crystals are self-assembled through Coulombic interactions between ion species, not through the hydrophilic-phobic interactions between charged ion heads and hydrophobic long alkyl pendants or the steric interaction between mesogenic moieties. Furthermore, the smectic order in the IL crystal ionogel facilitates exceptional and remarkable ionic transport. Large ionic conductivity, viscoelastic robustness, and additional electrochemical stability of the IL crystal ionogels provide promising opportunities for future electrochemical applications.

  20. Isothermal Cold Crystallization, Heat Resistance, and Tensile Performance of Polylactide/Thermoplastic Polyester Elastomer (PLA/TPEE Blends: Effects of Annealing and Reactive Compatibilizer

    Directory of Open Access Journals (Sweden)

    Sisi Wang

    2016-12-01

    Full Text Available The combined influences of crystallinity and reactive compatibilizer—a multifunctional epoxide (ADR—on morphology, tensile performance, and heat resistance of polylactide/thermoplastic polyester elastomer (PLA/TPEE (80/20 blends were investigated. Annealing involved an isothermal cold crystallization of PLA matrix was performed to increase crystallinity of the samples. First, isothermal cold crystallization kinetics were investigated using differential scanning calorimetry measurement. It was found that the addition of ADR decreased the crystallization rate of the samples. The maximum crystallinity of the annealed samples also decreased from 40% to 34% while ADR loading increased from zero to 1.0 phr. Furthermore, influence of crystallinity on mechanical performances of the PLA/TPEE sample was researched. The heat resistance of the sample showed a significant enhancement while increasing its crystallinity. Meanwhile, the tensile ductility of the crystallized PLA/TPEE sample became very poor due to the embrittlement with increased crystallinity and the incompatibility between PLA and TPEE. However, the annealed PLA/TPEE/ADR samples with high crystallinity kept a higher tensile ductility because ADR greatly improved the interfacial compatibility. Differences in tensile fracture behaviors of the quenched and annealed PLA/TPEE samples with and without ADR were discussed in detail. At last, crystallized PLA/TPEE/ADR blends with excellent heat resistance and high tensile ductility were obtained by annealing and reactive compatibilization.

  1. Spontaneous thermal expansion of nematic elastomers

    Science.gov (United States)

    Tajbakhsh, A. R.; Terentjev, E. M.

    2001-10-01

    We study the monodomain (single-crystal) nematic elastomer materials, all side-chain siloxane polymers with the same mesogenic groups and crosslinking density, but differing in the type of crosslinking. Increasing the proportion of long di-functional segments of main-chain nematic polymer, acting as network crosslinking, results in dramatic changes in the uniaxial equilibrium thermal expansion on cooling from the isotropic phase. At higher concentration of main chains their behaviour dominates the elastomer properties. At low concentration of main-chain material, we detect two distinct transitions at different temperatures, one attributed to the main-chain, the other to the side-chain component. The effective uniaxial anisotropy of nematic rubber, r(T)=ell_{allel}/ell_{bot} proportional to the effective nematic order parameter Q(T), is given by an average of the two components and thus reflects the two-transition nature of thermal expansion. The experimental data is compared with the theoretical model of ideal nematic elastomers; applications in high-amplitude thermal actuators are discussed in the end.

  2. A homeotropic main-chain tolane-type liquid crystal elastomer film exhibiting high anisotropic thermal conductivity.

    Science.gov (United States)

    Ge, Si-Jia; Zhao, Ti-Peng; Wang, Meng; Deng, Lin-Lin; Lin, Bao-Ping; Zhang, Xue-Qin; Sun, Ying; Yang, Hong; Chen, Er-Qiang

    2017-08-16

    The development of pure polymeric films with anisotropic thermal conductivities for electronic device packaging applications has attracted intense scientific attention. In order to enhance the polymeric film's normal-direction thermal conductivity, homeotropic alignment of macromolecular chains is the primary concern. One of the promising preparation strategies is to perform in situ photopolymerization of homeotropic-oriented liquid crystal monomers. In this work, we design and synthesize a novel tolane-core thiol-ene-tailed liquid crystal monomer. Benefitting from the conjugated and extended tolane π-system of the mesogenic core and length extension of the terminal aliphatic tails, the normal-to-plane thermal conductivity value and the thermal conductivity anisotropy value of the corresponding cross-linked main-chain end-on liquid crystal polymer (xMELCP) film reach 3.56 W m-1 K-1 and 15.0, respectively. Compared with the data of a previously reported ester-type thiol-ene xMELCP film, the two primary values of this novel tolane-type thiol-ene xMELCP material are increased dramatically by 46% and 29%, respectively.

  3. The Future of Swelling Elastomers: An Elastomer Manufacturer's View of Swelling Elastomer Developments and Market Trends

    Directory of Open Access Journals (Sweden)

    R Seyger

    2013-06-01

    Full Text Available Swelling elastomers have gained acceptance as very effective products for creating sealing in various industries, including those creating energy from fossil fuels and geothermal resources. This paper outlines the research and development work being conducted not only in the application of these elastomers but also in the development work required to create new generations of elastomers. It touches on fundamental research into the mechanics of swelling with the intent to create a better and more predictable sealing as well as more advanced elastomers. It lifts the veil on the direction of work being done on new elastomers being developed in order to enable a better control of swelling. By doing so, the research is opening up field of applications for new equipment designs and mechanical possibilities in the future. Additionally, it addresses the need for a better and more in-depth dialogue between both chemical and mechanical engineers, and the elastomer companies and their customers on the potential that both swelling and non-swelling elastomers can offer to the industry as a whole.

  4. Ordered macro-microporous metal-organic framework single crystals

    Science.gov (United States)

    Shen, Kui; Zhang, Lei; Chen, Xiaodong; Liu, Lingmei; Zhang, Daliang; Han, Yu; Chen, Junying; Long, Jilan; Luque, Rafael; Li, Yingwei; Chen, Banglin

    2018-01-01

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional–ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent–induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  5. Ordered macro-microporous metal-organic framework single crystals

    KAUST Repository

    Shen, Kui

    2018-01-16

    We constructed highly oriented and ordered macropores within metal-organic framework (MOF) single crystals, opening up the area of three-dimensional-ordered macro-microporous materials (that is, materials containing both macro- and micropores) in single-crystalline form. Our methodology relies on the strong shaping effects of a polystyrene nanosphere monolith template and a double-solvent-induced heterogeneous nucleation approach. This process synergistically enabled the in situ growth of MOFs within ordered voids, rendering a single crystal with oriented and ordered macro-microporous structure. The improved mass diffusion properties of such hierarchical frameworks, together with their robust single-crystalline nature, endow them with superior catalytic activity and recyclability for bulky-molecule reactions, as compared with conventional, polycrystalline hollow, and disordered macroporous ZIF-8.

  6. Ordering in nematic liquid crystals from NMR cross-polarization ...

    Indian Academy of Sciences (India)

    2015-11-27

    Nov 27, 2015 ... The measurement of dipolar couplings between nuclei is a convenient way of obtatining directly liquid crystalline ordering through NMR since the coupling is dependent on the average orientation of the dipolar vector in the magnetic field which also aligns the liquid crystal. However, measurement of the ...

  7. Ordering in nematic liquid crystals from NMR cross-polarization ...

    Indian Academy of Sciences (India)

    Abstract. The measurement of dipolar couplings between nuclei is a convenient way of obtatining directly liquid crystalline ordering through NMR since the coupling is dependent on the average orientation of the dipolar vector in the magnetic field which also aligns the liquid crystal. However, measurement of the dipolar ...

  8. Crystal chemistry of ordered rocksalt-type Ca2NF

    Science.gov (United States)

    Al-Azzawi, Mohanad; Zeller, Matthias; Li, Dingqiang; Wagner, Timothy R.

    2017-10-01

    Ordered rocksalt-type Ca2NF has a cubic unit cell that is doubled along [100] relative to the rocksalt-type polymorph due to N/F ordering. Crystals for the present study were prepared from a pure, dry KCuF3 precursor by reaction with Ca metal under nitrogen, and analyzed via high resolution single crystal X-ray diffraction. From this analysis, as well as qualitative compositional analysis using energy dispersive spectroscopy, it was determined that interstitial fluoride ions previously interpreted as Frenkel defects are actually due to a non-stoichiometric defect. The refined composition is Ca2N0.925F1.23, and the ordered cubic phase has space group Fd 3 bar m (No. 227) with a = 10.0301(5) Å and Z = 16.

  9. Isotactic polypropylene carbon nanotube composites -- crystallization and ordering behavior

    Science.gov (United States)

    Georgiev, Georgi; Judith, Robert; Gombos, Erin; McIntyre, Michael; Schoen, Scott; Cebe, Peggy; Mattera, Michael

    2010-03-01

    The field of Polymer Nanocomposites (PNCs) is growing steadily in recent years. We use carbon nanotubes (CNTs) to affect the crystallization behavior of the polymers. Isotactic Polypropylene (iPP) is very widely used and is a good model system to understand the physics of other similar polymers. iPP/CNT PNCs form α, β, and γ crystallographic phases under a variety of crystallization conditions: non-isothermal and isothermal melt crystallization, shear, stress, fiber extrusion, etc. The crystal growth is altered from spherulitic to α-fibrillar upon the nucleation effect of CNTs. We are studying the effect of different temperature treatment schemes and different isothermal crystallization conditions. We found also that the smectic ordering in iPP is improved by the introduction of CNTs. We use Differential Scanning Calorimetry, Wide Angle X-ray scattering, Microscopic Transmission Ellipsometry and Avrami analysis. Research supported by: Assumption College Faculty Development Grant, funding for students' stipends, instrumentation and supplies, the NSF Polymers Program of the DMR, grant (DMR-0602473) and NASA grant (NAG8-1167).

  10. Phase-field-crystal model for fcc ordering

    Science.gov (United States)

    Wu, Kuo-An; Adland, Ari; Karma, Alain

    2010-06-01

    We develop and analyze a two-mode phase-field-crystal model to describe fcc ordering. The model is formulated by coupling two different sets of crystal density waves corresponding to ⟨111⟩ and ⟨200⟩ reciprocal lattice vectors, which are chosen to form triads so as to produce a simple free-energy landscape with coexistence of crystal and liquid phases. The feasibility of the approach is demonstrated with numerical examples of polycrystalline and (111) twin growth. We use a two-mode amplitude expansion to characterize analytically the free-energy landscape of the model, identifying parameter ranges where fcc is stable or metastable with respect to bcc. In addition, we derive analytical expressions for the elastic constants for both fcc and bcc. Those expressions show that a nonvanishing amplitude of [200] density waves is essential to obtain mechanically stable fcc crystals with a nonvanishing tetragonal shear modulus (C11-C12)/2 . We determine the model parameters for specific materials by fitting the peak liquid structure factor properties and solid-density wave amplitudes following the approach developed for bcc [K.-A. Wu and A. Karma, Phys. Rev. B 76, 184107 (2007)]. This procedure yields reasonable predictions of elastic constants for both bcc Fe and fcc Ni using input parameters from molecular dynamics simulations. The application of the model to two-dimensional square lattices is also briefly examined.

  11. Synthesis of ordered carbonaceous frameworks from organic crystals.

    Science.gov (United States)

    Nishihara, Hirotomo; Hirota, Tetsuya; Matsuura, Kenta; Ohwada, Mao; Hoshino, Norihisa; Akutagawa, Tomoyuki; Higuchi, Takeshi; Jinnai, Hiroshi; Koseki, Yoshitaka; Kasai, Hitoshi; Matsuo, Yoshiaki; Maruyama, Jun; Hayasaka, Yuichiro; Konaka, Hisashi; Yamada, Yasuhiro; Yamaguchi, Shingi; Kamiya, Kazuhide; Kamimura, Takuya; Nobukuni, Hirofumi; Tani, Fumito

    2017-07-24

    Despite recent advances in the carbonization of organic crystalline solids like metal-organic frameworks or supramolecular frameworks, it has been challenging to convert crystalline organic solids into ordered carbonaceous frameworks. Herein, we report a route to attaining such ordered frameworks via the carbonization of an organic crystal of a Ni-containing cyclic porphyrin dimer (Ni2-CPDPy). This dimer comprises two Ni-porphyrins linked by two butadiyne (diacetylene) moieties through phenyl groups. The Ni2-CPDPy crystal is thermally converted into a crystalline covalent-organic framework at 581 K and is further converted into ordered carbonaceous frameworks equipped with electrical conductivity by subsequent carbonization at 873-1073 K. In addition, the porphyrin's Ni-N4 unit is also well retained and embedded in the final framework. The resulting ordered carbonaceous frameworks exhibit an intermediate structure, between organic-based frameworks and carbon materials, with advantageous electrocatalysis. This principle enables the chemical molecular-level structural design of three-dimensional carbonaceous frameworks.Carbon-based materials are promising alternatives to noble metal catalysts, but their structures are typically disordered and difficult to control. Here, the authors obtain ordered carbonaceous frameworks with advantageous electrocatalytic properties via the carbonization of nickel-containing porphyrin dimer networks.

  12. Kinetically driven ordered phase formation in binary colloidal crystals

    Science.gov (United States)

    Bochicchio, D.; Videcoq, A.; Ferrando, R.

    2013-02-01

    The aggregation of binary colloids of the same size and balanced charges is studied by Brownian dynamics simulations for dilute suspensions. It is shown that, under appropriate conditions, the formation of colloidal crystals is dominated by kinetic effects leading to the growth of well-ordered crystallites of the sodium-chloride (NaCl) bulk phase. These crystallites form with very high probability even when the cesium-chloride (CsCl) phase is more stable thermodynamically. Global optimization searches show that this result is not related to the most favorable structures of small clusters, which are either amorphous or of the CsCl structure. The formation of the NaCl phase is related to the specific kinetics of the crystallization process, which takes place by a two-step mechanism. In this mechanism, dense fluid aggregates form at first and then crystallization follows. It is shown that the type of short-range order in these dense fluid aggregates determines which phase is finally formed in the crystallites. The role of hydrodynamic effects in the aggregation process is analyzed by stochastic rotation dynamics - molecular dynamics simulations, and we find that these effects do not play a major role in the formation of the crystallites.

  13. Local structural ordering in surface-confined liquid crystals

    Science.gov (United States)

    Śliwa, I.; Jeżewski, W.; Zakharov, A. V.

    2017-06-01

    The effect of the interplay between attractive nonlocal surface interactions and attractive pair long-range intermolecular couplings on molecular structures of liquid crystals confined in thin cells with flat solid surfaces has been studied. Extending the McMillan mean field theory to include finite systems, it has been shown that confining surfaces can induce complex orientational and translational ordering of molecules. Typically, local smectic A, nematic, and isotropic phases have been shown to coexist in certain temperature ranges, provided that confining cells are sufficiently thick, albeit finite. Due to the nonlocality of surface interactions, the spatial arrangement of these local phases can display, in general, an unexpected complexity along the surface normal direction. In particular, molecules located in the vicinity of surfaces can still be organized in smectic layers, even though nematic and/or isotropic order can simultaneously appear in the interior of cells. The resulting surface freezing of smectic layers has been confirmed to occur even for rather weak surface interactions. The surface interactions cannot, however, prevent smectic layers from melting relatively close to system boundaries, even when molecules are still arranged in layers within the central region of the system. The internal interfaces, separating individual liquid-crystal phases, are demonstrated here to form fronts of local finite-size transitions that move across cells under temperature changes. Although the complex molecular ordering in surface confined liquid-crystal systems can essentially be controlled by temperature variations, specific thermal properties of these systems, especially the nature of the local transitions, are argued to be strongly conditioned to the degree of molecular packing.

  14. Antipolar ordering of topological defects in active liquid crystals

    Science.gov (United States)

    Oza, Anand U.; Dunkel, Jörn

    2016-09-01

    ATP-driven microtubule-kinesin bundles can self-assemble into two-dimensional active liquid crystals (ALCs) that exhibit a rich creation and annihilation dynamics of topological defects, reminiscent of particle-pair production processes in quantum systems. This recent discovery has sparked considerable interest but a quantitative theoretical description is still lacking. We present and validate a minimal continuum theory for this new class of active matter systems by generalizing the classical Landau-de Gennes free-energy to account for the experimentally observed spontaneous buckling of motor-driven extensile microtubule bundles. The resulting model agrees with recently published data and predicts a regime of antipolar order. Our analysis implies that ALCs are governed by the same generic ordering principles that determine the non-equilibrium dynamics of dense bacterial suspensions and elastic bilayer materials. Moreover, the theory manifests an energetic analogy with strongly interacting quantum gases. Generally, our results suggest that complex nonequilibrium pattern-formation phenomena might be predictable from a few fundamental symmetry-breaking and scale-selection principles.

  15. The Electrical Breakdown of Thin Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Morshuis, Peter H. F.; Yahia, Benslimane Mohamed

    2014-01-01

    Dielectric elastomers are being developed for use in actuators, sensors and generators to be used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. In order to obtain maximum efficiency, the devices are operated at high electrical fields....... This increases the likelihood for electrical breakdown significantly. Hence, for many applications the performance of the dielectric elastomers is limited by this risk of failure, which is triggered by several factors. Amongst others thermal effects may strongly influence the electrical breakdown strength....... In this study, we model the electrothermal breakdown in thin PDMS based dielectric elastomers in order to evaluate the thermal mechanisms behind the electrical failures. The objective is to predict the operation range of PDMS based dielectric elastomers with respect to the temperature at given electric field...

  16. Controlling order with light and light with order in liquid crystals: Two case studies (Conference Presentation)

    Science.gov (United States)

    Priimagi, Arri

    2016-09-01

    This presentation comprises two topics, both relating to the interplay of light and order in liquid-crystalline (LC) materials. Firstly, we will present a novel series of azobenzene-based, halogen-bonded supramolecular LCs, with rich photochemical phenomena and exhibiting both reversible photochemical crystal-to-isotropic and LC-to-isotropic phase transitions. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to conclude that less than 4 % of the mesogenic units in the cis-form suffices to trigger the LC-to-isotropic phase transition. To the best of our knowledge, this is the first quantitative analysis of the phase transition process in supramolecular liquid crystals, demonstrating the versatility of these materials as functional liquid-crystalline assemblies and pinpointing their potential towards building supramolecular actuators. Secondly, we propose a conceptually novel approach to enhance the orientational optical nonlinearity of dye-doped LCs, based on polymer stabilization. Compared to azobenzene-triggered photochemical systems, photophysical systems, where the alignment change is caused by light-induced torques due to absorbing moieties, may provide some benefits, allowing for molecular reorientation only above certain threshold intensity, and reducing reorientation instabilities and fluctuations in the photostationary state. In addition to decreasing the light intensity at which self-phase modulation takes place, the polymer stabilization approach may open up a pathway towards all-optical realization of temporally stable photonic elements and guided-wave structures based on LC systems.

  17. Toxicity of Pyrolysis Gases from Elastomers

    Science.gov (United States)

    Hilado, Carlos J.; Kosola, Kay L.; Solis, Alida N.; Kourtides, Demetrius A.; Parker, John A.

    1977-01-01

    The toxicity of the pyrolysis gases from six elastomers was investigated. The elastomers were polyisoprene (natural rubber), styrene-butadiene rubber (SBR), ethylene propylene diene terpolymer (EPDM), acrylonitrile rubber, chlorosulfonated polyethylene rubber, and polychloroprene. The rising temperature and fixed temperature programs produced exactly the same rank order of materials based on time to death. Acryltonitrile rubber exhibited the greatest toxicity under these test conditions; carbon monoxide was not found in sufficient concentrations to be the primary cause of death.

  18. Model FORC diagrams for hybrid magnetic elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Vaganov, M.V., E-mail: mikhail.vaganov.sci@gmail.com.ru [Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm, 614013 (Russian Federation); Linke, J.; Odenbach, S. [Technische Universität Dresden, Dresden, 01062 Germany (Germany); Raikher, Yu.L. [Institute of Continuous Media Mechanics, Russian Academy of Sciences, Ural Branch, Perm, 614013 (Russian Federation); Ural Federal University, Ekaterinburg, 620083 (Russian Federation)

    2017-06-01

    We propose a model of hybrid magnetic elastomers filled with a mixture of magnetically soft and magnetically hard microparticles. The magnetically hard particles are described by the Stoner–Wohlfarth model, the magnetically soft phase obeys the Fröhlich–Kennelly equation. The interaction between the two types of particles is described by the mean-field approach. First-order reversal curve (FORC) diagrams were calculated for different values of the elastomer matrix elasticity. We demonstrate that the diagrams display specific new features, which identify the presence of both a deformable matrix and the two types of magnetic particles. - Highlights: • A model of hybrid magnetic elastomers is proposed. • The magnetically hard particles are described by the Stoner–Wohlfarth model. • The magnetically soft phase obeys the Fröhlich–Kennelly equation. The interaction between the phases is described by the mean-field approach. • FORC diagrams are calculated for different values of the elastomer matrix elasticity.

  19. Bimodal condensation silicone elastomers as dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    elastomers were prepared by mixing different mass ratios (9:1, 8:2, 7:3, 6:4, 5:5, 4:6) between long polydimethylsiloxane (PDMS) chains and short PDMS chains. The resulting elastomers were investigated with respect to their rheology, dielectric properties, tensile strength, electrical breakdown, as well...... as well as high electrical and mechanical breakdown strengths. [1] Most model elastomers are prepared by an end-linking process using a crosslinker with a certain functionality ƒ and a linear polymer with functional groups in both ends, and the resulting networks are so-called unimodal networks where...... as thermal stability. The bimodal elastomers reinforce themselves at large strain and the high electrical breakdown strength is obtained due both to the low extensibility of the short chains that attach strongly the long chains and to the extensibility of the last ones that retards the rupture process...

  20. Entirely soft dielectric elastomer robots

    Science.gov (United States)

    Henke, E.-F. Markus; Wilson, Katherine E.; Anderson, Iain A.

    2017-04-01

    Multifunctional Dielectric Elastomer (DE) devices are well established as actuators, sensors and energy har- vesters. Since the invention of the Dielectric Elastomer Switch (DES), a piezoresistive electrode that can directly switch charge on and off, it has become possible to expand the wide functionality of DE structures even more. We show the application of fully soft DE subcomponents in biomimetic robotic structures. It is now possible to couple arrays of actuator/switch units together so that they switch charge between them- selves on and off. One can then build DE devices that operate as self-controlled oscillators. With an oscillator one can produce a periodic signal that controls a soft DE robot - a DE device with its own DE nervous system. DESs were fabricated using a special electrode mixture, and imprinting technology at an exact pre-strain. We have demonstrated six orders of magnitude change in conductivity within the DES over 50% strain. The control signal can either be a mechanical deformation from another DE or an electrical input to a connected dielectric elastomer actuator (DEA). We have demonstrated a variety of fully soft multifunctional subcomponents that enable the design of autonomous soft robots without conventional electronics. The combination of digital logic structures for basic signal processing, data storage in dielectric elastomer flip-flops and digital and analogue clocks with adjustable frequencies, made of dielectric elastomer oscillators (DEOs), enables fully soft, self-controlled and electronics-free robotic structures. DE robotic structures to date include stiff frames to maintain necessary pre-strains enabling sufficient actuation of DEAs. Here we present a design and production technology for a first robotic structure consisting only of soft silicones and carbon black.

  1. Second-order polarization-mode dispersion in photonic crystal fibers

    DEFF Research Database (Denmark)

    Larsen, T; Bjarklev, Anders Overgaard; Peterson, A

    2003-01-01

    We report the first experimental measurements of second-order polarization-mode dispersion in two successive 900 meter pulls of a silica photonic crystal fiber.......We report the first experimental measurements of second-order polarization-mode dispersion in two successive 900 meter pulls of a silica photonic crystal fiber....

  2. Crystal growth and characterization of third order nonlinear optical piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) single crystal

    Science.gov (United States)

    Pichan, Karuppasamy; Muthu, Senthil Pandian; Perumalsamy, Ramasamy

    2017-09-01

    The organic single crystal of piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) was grown by slow evaporation solution technique (SEST) at room temperature. The lattice parameters of the grown crystal were confirmed by single crystal X-ray diffraction analysis. Functional groups of P4HBS crystal were confirmed by FTIR spectrum analysis. The optical quality of the grown crystal was identified by the UV-Vis NIR spectrum analysis. The grown crystal has good optical transmittance in the range of 410-1100 nm. In photoluminescence spectrum, sharp emission peaks are observed, which indicates the ultraviolet (UV) emission. The photoconductivity study reveals that the grown crystal has negative photoconductive nature. The thermal behaviour of the P4HBS crystal was investigated by thermogravimetric and differential thermal analysis (TG-DTA). The mechanical stability of grown crystal was analyzed and the indentation size effect (ISE) was explained by Hays-Kendall's (HK) approach and proportional specimen resistance model (PSRM). Chemical etching study was carried out and the etch pit density (EPD) was calculated. The dielectric constant (ε‧) and dielectric loss (tan δ) as a function of frequency were measured for the grown crystal. The solid state parameters such as valence electron, plasma energy, Penn gap and Fermi energy were evaluated theoretically for the P4HBS using the empirical relation. The estimated values are used to calculate the electronic polarizability. The third-order nonlinear optical properties such as nonlinear refractive index (n2), absorption co-efficient (β) and susceptibility (χ(3)) were studied by Z-scan technique at 632.8 nm using He-Ne laser.

  3. Molecular dynamics calculations of melting rates with a novel order parameter. The diatomic Pa3 crystal.

    NARCIS (Netherlands)

    Tepper, H.L.; Scheinhardt-Engels, S.M.; Briels, Willem J.

    2003-01-01

    A method is presented to design order parameters that can be used as discriminator in two-phase crystal-liquid molecular dynamics simulations. The proposed methodology is an extension to molecular crystal structures of a previously introduced discriminator for the atomic fcc environment [Phys. Rev.

  4. Utilizing liquid crystal phases to obtain highly ordered thin films for organic electronics

    Science.gov (United States)

    Springer, Mike T.

    Organic electronic materials offer several advantages when compared to inorganic materials, but they suffer from low charge carrier mobility. Two major factors hindering effective charge transport in organic materials are: 1) effective wavefunction overlap in organic crystals and 2) the domain morphology of thin films. Charge transport in organic materials occurs via a hopping mechanism along the conjugated pi system. Often, rigid, aromatic organic materials crystallize in a herringbone, edge-to-face orientation, limiting pi-pi stacking and decreasing charge carrier mobility. Face-to-face orientation of aromatic rings decreases intermolecular pi-pi distances and increases wavefunction overlap. Control of the crystal structure can be achieved to some extent by tuning structural features of the molecule, like increasing the ratio of carbon atoms to hydrogen atoms in the aromatic rings; this is often achieved by introducing heteroatoms like sulfur and oxygen into the aromatic ring structure. Thin films of organic materials often contain many unaligned domains; this is caused by rapid crystallization. Control of the domain morphology of thin films has been shown to increase charge carrier mobility by 6 orders of magnitude for thin films of the same material. Liquid crystal phases allow a slow process of crystallization, whereby the molecules in a thin film can be slowly aligned into a monodomain before crystallization. The crystal-smectic phases, like smectic E, are particularly attractive for this strategy due to their high degree of intermolecular order. This project describes the synthesis and characterization of organic semiconductors designed to exhibit short pi-pi distances and highly ordered crystal-smectic phases to obtain thin films with high charge carrier mobility. The n,2-OBTTT series contains 15 newly designed and synthesized mesogens. The liquid crystal and solid crystal structures of these mesogens are examined and deposition conditions are optimized for

  5. Silicone elastomers with aromatic voltage stabilizers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    elastomers with high relative permittivity and low Young’s modulus in order to increase the actuation performance at a given voltage, but the optimised elastomers often possess relatively low electrical breakdown strength. On the other hand, increasing the electrical breakdown strength of DEs allows...... modifications. In order to increase the electrical breakdown strength of polymers for e.g. the cable industry, additives like aromatic voltage stabilizers are used. Earlier works on using voltage stabilizers in polymers have mainly focused on polyethylene with the purpose of reducing power loss for high voltage...... insulation cables.3–5 As an alternative to utilise additives as voltage stabilizers, grafting aromatic compounds to silicone backbones may overcome the common problem of insolubility of the aromatic voltage stabilizer in the silicone elastomers due to phase separation. Preventing phase separation during...

  6. X-ray third-order nonlinear dynamical diffraction in a crystal

    Energy Technology Data Exchange (ETDEWEB)

    Balyan, M. K., E-mail: mbalyan@ysu.am [Yerevan State University, Faculty of Physics (Armenia)

    2015-12-15

    The dynamic diffraction of an X-ray wave in a crystal with a third-order nonlinear response to external field strength has been theoretically investigated. General equations for the wave propagation in crystal and nonlinear Takagi equations for both ideal and deformed crystals are derived. Integrals of motion are determined for the nonlinear problem of dynamic diffraction. The results of the numerical calculations of reflectivity in the symmetric Laue geometry for an incident plane wave and the intensity distributions on the output crystal surface for a point source are reported as an example.

  7. The second order phase transition in Sn2P2S6 crystals: anharmonic oscillator model

    Directory of Open Access Journals (Sweden)

    Yu.M. Vysochanskii

    2008-09-01

    Full Text Available Statistical theory for ferroelectrics based on triple well anharmonic potential was used for the case of structural second order phase transition in Sn2P2S6 crystals. Parameters of effective Hamiltonian of the model were estimated using available experimental data. These findings confirm the assumption that the phase transition in these crystals is located in crossover region between order-disorder and displacive type, and very closely to tricritical point.

  8. Self-assembled ordered structures in thin films of HAT5 discotic liquid crystal

    Directory of Open Access Journals (Sweden)

    Piero Morales

    2010-05-01

    Full Text Available Thin films of the discotic liquid crystal hexapentyloxytriphenylene (HAT5, prepared from solution via casting or spin-coating, were investigated by atomic force microscopy and polarizing optical microscopy, revealing large-scale ordered structures substantially different from those typically observed in standard samples of the same material. Thin and very long fibrils of planar-aligned liquid crystal were found, possibly formed as a result of an intermediate lyotropic nematic state arising during the solvent evaporation process. Moreover, in sufficiently thin films the crystallization seems to be suppressed, extending the uniform order of the liquid crystal phase down to room temperature. This should be compared to the bulk situation, where the same material crystallizes into a polymorphic structure at 68 °C.

  9. Elastomer genome: Reverse tissue engineering.

    Science.gov (United States)

    Sheiko, Sergei S.

    Soft elastic materials enable the creation of implants, substrates, and haptic robotic digits with mechanical properties matching those of biological tissues. Currently, polymer gels are the only viable class of synthetic materials with a Young's modulus below 100 kPa. However, the liquid fraction in the gels causes practical troubles including phase separation and solvent leakage on deformation. Herein, we have created bottlebrush and comb-like networks that are superelastic (λ = 1-12) and ultrasoft (G =102 - 105 Pa), even in the absence of solvent. The brush-like architecture causes an increase in the diameter of individual polymer molecules, but unlike typical filaments, the molecules remain flexible. This enables a significant decrease in the entanglement density, which reduces the limit of stiffness in dry polymer materials by 1000 times and has opened up new applications not available to stiffer materials or materials with liquid fractions. The comb-like architecture offers three independently controlled parameters - side-chain length, grafting density, and crosslink density - that allow for combinatorial variations of elastomer mechanical properties impossible for conventional linear chain elastomers, e.g. simultaneously increasing rigidity and elasticity. Based on this materials design platform, we have prepared elastomers that closely match the mechanical behaviour of biological tissue. Furthermore, this architecture affords many chain-ends that are amendable for chemical modifications and enhance molecular mobility, which directly affects vital physical properties ranging from glass transition and crystallization temperatures to adhesion and permeability. This work has been supported by the National Science Foundation (DMR-1407645 and DMR-1436201).

  10. Acrylic interpenetrating polymer network dielectric elastomers for energy harvesting

    Science.gov (United States)

    Brochu, Paul; Niu, Xiaofan; Pei, Qibing

    2011-04-01

    Dielectric elastomer energy harvesters are an emerging technology that promise high power density, low cost, scalability, and the capability of fitting niche markets that have yet to be exploited. To date, materials issues that limit their overall performance have hampered the full potential of these devices. In order to supplant existing technologies, even in niche markets, dielectric elastomer generators must increase their reliability and energy density. Previous work has indicated that stiffer elastomers should be capable of higher energy densities; the increased stiffness of the elastomer films should results in lower Maxwell pressure induced strains, and thus allow the elastomer to relax further, resulting in a larger swing in capacitance and larger energy gains. In this paper we examine the use of VHB-based acrylic interpenetrating polymer network dielectric elastomers with a trimethylolpropane trimethacrylate additive network for energy harvesting purposes. We test films with varying additive content and compare their performance with highly prestrained VHB acrylic elastomers. We show that by increasing additive content, Maxwell induced strains can be suppressed and larger energy gains can be achieved at higher bias fields. Moreover, the introduction of the additive network stabilizes the highly prestrained acrylic elastomers mechanically, thereby increasing their mechanical robustness. However, the interpenetrating polymer network films suffer from an increase in viscoelastic behavior that hinders their overall performance.

  11. Energy conversion in magneto-rheological elastomers.

    Science.gov (United States)

    Sebald, Gael; Nakano, Masami; Lallart, Mickaël; Tian, Tongfei; Diguet, Gildas; Cavaille, Jean-Yves

    2017-01-01

    Magneto-rheological (MR) elastomers contain micro-/nano-sized ferromagnetic particles dispersed in a soft elastomer matrix, and their rheological properties (storage and loss moduli) exhibit a significant dependence on the application of a magnetic field (namely MR effect). Conversely, it is reported in this work that this multiphysics coupling is associated with an inverse effect (i.e. the dependence of the magnetic properties on mechanical strain), denoted as the pseudo-Villari effect. MR elastomers based on soft and hard silicone rubber matrices and carbonyl iron particles were fabricated and characterized. The pseudo-Villari effect was experimentally quantified: a shear strain of 50 % induces magnetic induction field variations up to 10 mT on anisotropic MR elastomer samples, when placed in a 0.2 T applied field, which might theoretically lead to potential energy conversion density in the mJ cm -3 order of magnitude. In case of anisotropic MR elastomers, the absolute variation of stiffness as a function of applied magnetic field is rather independent of matrix properties. Similarly, the pseudo-Villari effect is found to be independent to the stiffness, thus broadening the adaptability of the materials to sensing and energy harvesting target applications. The potential of the pseudo-Villari effect for energy harvesting applications is finally briefly discussed.

  12. Synthesis, crystal structure, growth, optical and third order nonlinear optical studies of 8HQ2C5N single crystal - An efficient third-order nonlinear optical material

    Energy Technology Data Exchange (ETDEWEB)

    Divya Bharathi, M.; Ahila, G.; Mohana, J. [Department of Physics, Presidency College, Chennai 600005 (India); Chakkaravarthi, G. [Department of Physics, CPCL Polytechnic College, Chennai 600068 (India); Anbalagan, G., E-mail: anbu24663@yahoo.co.in [Department of Nuclear Physics, University of Madras, Chennai 600025 (India)

    2017-05-01

    A neoteric organic third order nonlinear optical material 8-hydroxyquinolinium 2-chloro-5-nitrobenzoate dihydrate (8HQ2C5N) was grown by slow cooling technique using ethanol: water (1:1) mixed solvent. The calculated low value of average etch pit solidity (4.12 × 10{sup 3} cm{sup −2}) indicated that the title crystal contain less defects. From the single crystal X-ray diffraction data, it was endowed that 8HQ2C5N crystal belongs to the monoclinic system with centrosymmetric space group P2{sub 1}/c and the cell parameters values, a = 9.6546 (4) Ǻ, b = 7.1637(3) Ǻ, c = 24.3606 (12) Ǻ, α = γ = 90°, β = 92.458(2)° and volume = 1683.29(13) Ǻ{sup 3}. The FT-IR and FT-Raman spectrum were used to affirm the functional group of the title compound. The chemical structure of 8HQ2C5N was scrutinized by {sup 13}C and {sup 1}H NMR spectral analysis and thermal stability through the differential scanning calorimetry study. Using optical studies the lower cut-off wavelength and optical band gap of 8HQ2C5N were found to be 364 nm and 3.17 eV respectively. Using the single oscillator model suggested by Wemple – Didomenico, the oscillator energy (E{sub o}), the dispersion energy (E{sub d}) and static dielectric constant (ε{sub o}) were estimated. The third-order susceptibility were determined as Im χ{sup (3)} = 2.51 × 10{sup −5} esu and Re χ{sup (3)} = 4.46 × 10{sup −7} esu. The theoretical third-order nonlinear optical susceptibility χ{sup (3)} was calculated and the results were compared with experimental value. Photoluminescence spectrum of 8HQ2C5N crystal showed the yellow emission. The crystal had the single shot laser damage threshold of 5.562 GW/cm{sup 2}. Microhardness measurement showed that 8HQ2C5N belongs to a soft material category. - Highlights: • A new organic single crystals were grown and the crystal structure was reported. • Crystal possess, good transmittance, thermal and mechanical stability. • Single shot LDT value is found to be

  13. High Temperature Hybrid Elastomers

    Science.gov (United States)

    Drake, Kerry Anthony

    Conventional high temperature elastomers are produced by chain polymerization of olefinic or fluorinated olefinic monomers. Ultimate thermal stabilities are limited by backbone bond strengths, lower thermal stability of cross-link sites relative to backbone bonds, and depolymerization or "unzipping" at high temperatures. In order to develop elastomers with enhanced thermal stability, hybrid thermally cross-linkable polymers that consisted only of organic-inorganic and aromatic bonds were synthesized and evaluated. The addition of phenylethynyl or phenylacetylinic functional groups to these polymers resulted in conversion of the polymers into high temperature elastomers when cross-linked by thermal curing. Polyphenyoxydiphenylsilanes were synthesized via several different condensation reactions. Results of these synthetic reactions, which utilized both hydroquinone and biphenol as monomers, were systematically evaluated to determine the optimal synthetic conditions for subsequent endcapping reactions. It was determined that dichlorodiphenylsilane condensations with biphenol in toluene or THF were best suited for this work. Use of excess dichlorodiphenylsilane yielded polymers of appropriate molecular weights with terminal reactive chlorosilane groups that could be utilized for coupling with phenylethynyl reagents in a subsequent reaction. Two new synthetic routes were developed to endcap biphenoxysilanes with ethynyl containing substituents, to yield polymers with cross-linkable end groups. Endcapping by lithiumphenylacetylide and 4[(4-fluorophenylethynyl))phenol yielded two new polymers that could be thermally cross-linked on heating above 300 °C. Successful endcapping was verified chemically by 13C NMR, FTIR and Raman analysis. Exothermic peaks consistent with ethynyl curing reactions were observed in endcapped polymers by DSC. A new diacetylinic polymer was prepared through reaction of 4,4'-buta-1,3-diyne-1,4-diyldiphenol and dichlorodiphenylsilane. This

  14. Direct sun-driven artificial heliotropism for solar energy harvesting based on a photo-thermomechanical liquid-crystal elastomer nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chensha; Liu, Ye; Huang, Xuezhen [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI, 53706 (United States); Jiang, Hongrui [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI, 53706 (United States); Materials Science Program, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI, 53706 (United States)

    2012-12-19

    Inspired by heliotropism in nature, artificial heliotropic devices that can follow the sun for increased light interception are realized. The mechanism of the artificial heliotropism is realized via direct actuation by the sunlight, eliminating the need for additional mechatronic components and resultant energy consumption. For this purpose, a novel reversible photo-thermomechanical liquid crystalline elastomer (LCE) nanocomposite is developed that can be directly driven by natural sunlight and possesses strong actuation capability. Using the LCE nanocomposite actuators, the artificial heliotropic devices show full-range heliotropism in both laboratory and in-field tests. As a result, significant increase in the photocurrent output from the solar cells in the artificial heliotropic devices is observed. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Well-ordered polymer nano-fibers with self-cleaning property by disturbing crystallization process

    National Research Council Canada - National Science Library

    Yang, Qin; Luo, Zhuangzhu; Tan, Sheng; Luo, Yimin; Wang, Yunjiao; Zhang, Zhaozhu; Liu, Weimin

    2014-01-01

    Bionic self-cleaning surfaces with well-ordered polymer nano-fibers are firstly fabricated by disturbing crystallization during one-step coating-curing process. Orderly thin (100 nm) and long (5–10 μm...

  16. A finite deformation theory of higher-order gradient crystal plasticity

    DEFF Research Database (Denmark)

    Kuroda, Mitsutoshi; Tvergaard, Viggo

    2008-01-01

    For higher-order gradient crystal plasticity, a finite deformation formulation is presented. The theory does not deviate much from the conventional crystal plasticity theory. Only a back stress effect and additional differential equations for evolution of the geometrically necessary dislocation (...... for the small deformation theory. As in a previous formulation for small deformation, the present formulation applies to the context of multiple and three-dimensional slip deformations. (C) 2008 Elsevier Ltd. All rights reserved....

  17. Observation of Algebraic Decay of Positional Order in a Smectic Liquid Crystal

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Litster, J. D.; Birgeneau, R. J.

    1980-01-01

    A smectic-A liquid crystal in three dimensions has been predicted to exhibit algebraic decay of the layer correlations rather than true long-range order. As a consequence, the smectic Bragg peaks are expected to be power-law singularities of the form q∥-2+η and q⊥-4+2η, where ∥(⊥) is along...... (perpendicular to) the smectic density wave vector direction, rather than δ function peaks. Observation of these phenomena requires very high instrumental resolution together with a resolution function with wings which drop off much more rapidly than q∥-2(q⊥-4). We show that these requirements may be met...... by using a three crystal x-ray spectrometer with multiple-reflection channel cut crystals as monochromator and analyzer. We find that the smectic-A Bragg peaks observed in the liquid-crystal octyloxy-cyanobiphenyl are indeed consistent with the predicted power-law singularity form. Furthermore...

  18. Smectic elastomer membranes

    OpenAIRE

    Stenull, Olaf

    2007-01-01

    We present a model for smectic elastomer membranes which includes elastic and liquid crystalline degrees of freedom. Based on our model, we determined the qualitative phase diagram of a smectic elastomer membrane using mean-field theory. This phase diagram is found to comprise five phases, viz. smectic-A--flat, smectic-A--crumpled, smectic-C--flat, smectic-C--crumpled and smectic-C--tubule, where in the latter phase, the membrane is flat in the direction of mesogenic tilt and crumpled in the ...

  19. Deuteron NMR study of molecular ordering in a holographic-polymer-dispersed liquid crystal.

    Science.gov (United States)

    Vilfan, Marija; Zalar, Bostjan; Fontecchio, Adam K; Vilfan, Mojca; Escuti, Michael J; Crawford, Gregory P; Zumer, Slobodan

    2002-08-01

    Using deuteron nuclear magnetic resonance (NMR) and dynamic light scattering, we study the orientational order and dynamics of a BL038-5CB liquid-crystal mixture in a holographic polymer dispersed liquid-crystal material (HPDLC) as used for switchable diffractive optical elements. At high temperatures, where the liquid crystal is predominantly in the isotropic phase, the HPDLC deuteron NMR linewidth and transverse spin-relaxation rate T-12 are two orders of magnitude larger than in the bulk. The analysis shows that the surface-induced order parameter in HPDLC is significantly larger than in similar confining systems and that translational diffusion of molecules in the surface layer is at least two orders of magnitude slower than in the rest of the cavity. The unusual temperature dependence of T-12 upon cooling suggests the possibility of a partial separation of the 5CB component in the liquid-crystal mixture. The onset of the nematic phase in HPDLC occurs at considerably lower temperature than in the bulk and takes place gradually due to different sizes and different content of non-liquid-crystalline ingredients in droplets. Parts of the droplets are found isotropic even at room temperature and the structure of the nematic director field in the droplets is only slightly anisotropic. We point out the capability of NMR to detect the actual state of liquid-crystalline order in HPDLCs and to contribute in this way to the improvement of the switching efficiency of diffraction gratings.

  20. Role of bond orientational order in the crystallization of hard spheres

    Science.gov (United States)

    Russo, John; Tanaka, Hajime

    2013-02-01

    With computer simulations of the hard sphere model, we examine in detail the microscopic pathway connecting the metastable melt to the emergence of crystalline clusters. In particular we will show that the nucleation of the solid phase does not follow a two-step mechanism, where crystals form inside dense precursor regions. On the contrary, we will show that nucleation is driven by fluctuations of orientational order, and not by the density fluctuations. By considering the development of the pair-excess entropy inside crystalline nuclei, we confirm that orientational order precedes positional order. These results are at odd with the idea of a two-step nucleation mechanism for fluids without a metastable liquid-liquid phase separation. Our study suggests the pivotal role of bond orientational ordering in triggering crystal nucleation.

  1. Surface-induced orientational order in stretched nanoscale-sized polymer dispersed liquid-crystal droplets.

    Science.gov (United States)

    Amimori, Ichiro; Eakin, James N; Qi, Jun; Skacej, Gregor; Zumer, Slobodan; Crawford, Gregory P

    2005-03-01

    We investigate orientational ordering in stretched polymer-dispersed liquid-crystal (PDLC) droplets using deuterium nuclear magnetic resonance, in the nematic and isotropic phases. In the latter case, we estimate the surface order parameter S(0) and the thickness of the interfacial layer from the temperature-independent surface ordering model for an elliptical cavity with a varying aspect ratio. A simple phenomenological model well describes the quadrupole splitting frequency of NMR spectra in the isotropic phase. The strain dependence of S(0) suggests that stretching-induced changes in the orientation of polymer chains in the PDLC matrix noticeably affect liquid-crystal surface anchoring. Experimental results are supported by simulated NMR spectra obtained as output from Monte Carlo simulations of paranematic ordering in ellipsoidal droplets based on the Lebwohl-Lasher lattice model.

  2. Elastomer-Modified Polyimides

    Science.gov (United States)

    Fohlen, G. M.; Parker, J.; Varma, I. K.

    1984-01-01

    New resins yield laminates with improved mechanical properties. Ingredients of Modified Polymer include bisimide of formula 1 and amine-terminated elastomer. Cure effected by heating to temperature suited to particular ingredients used, generally in range of 200 degrees to 300 degrees C. Solution of solvent and reactants used for fabricating fiber-reinforced structures or as adhesive.

  3. Spiro-OMeTAD single crystals: Remarkably enhanced charge-carrier transport via mesoscale ordering

    KAUST Repository

    Shi, Dong

    2016-04-15

    We report the crystal structure and hole-transport mechanism in spiro-OMeTAD [2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene], the dominant hole-transporting material in perovskite and solid-state dye-sensitized solar cells. Despite spiro-OMeTAD’s paramount role in such devices, its crystal structure was unknown because of highly disordered solution-processed films; the hole-transport pathways remained ill-defined and the charge carrier mobilities were low, posing a major bottleneck for advancing cell efficiencies. We devised an antisolvent crystallization strategy to grow single crystals of spiro-OMeTAD, which allowed us to experimentally elucidate its molecular packing and transport properties. Electronic structure calculations enabled us to map spiro-OMeTAD’s intermolecular charge-hopping pathways. Promisingly, single-crystal mobilities were found to exceed their thin-film counterparts by three orders of magnitude. Our findings underscore mesoscale ordering as a key strategy to achieving breakthroughs in hole-transport material engineering of solar cells.

  4. Compatibility analysis of Nylon 6 and poly(ethylene-n-butyl acrylate-maleic anhydride) elastomer blends using isothermal crystallization kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Biber, Erkan, E-mail: ebiber@cankaya.edu.tr [Middle East Technical University, Polymer Science and Technology Department, Ankara (Turkey); Cankaya University, Industrial Engineering Department, Ankara (Turkey); Guenduez, Guengoer [Middle East Technical University, Polymer Science and Technology Department, Ankara (Turkey); Middle East Technical University, Chemical Engineering Department, Ankara (Turkey); Mavis, Bora [Hacettepe University, Mechanical Engineering Department, Ankara (Turkey); Colak, Uner [Hacettepe University, Nuclear Energy Engineering Department, Ankara (Turkey)

    2010-07-01

    Nylon 6 is a widely used engineering polymer, and has relatively poor impact strength. Ethylene, n-Butyl acrylate, maleic anhydride (E-nBA-MAH) terpolymer is blended with Nylon 6 to enhance its impact strength. Mixture should be compatible to be used in applications. The bare interaction energy between Nylon 6 and E-nBA-MAH terpolymer is calculated according to melting point depression approach using both Flory-Huggins (FH) Theory and Sanchez-Lacombe Equation of State (SL EOS). It demonstrates that blends are thermodynamically favorable to any arrangements. Yet, isothermal crystallization kinetics and WAXS crystallization peaks of blends reveal that mixtures of various compositions have different crystallization behaviors and require alternating crystallization energy due to crystalline structures of individual polymers. Also, SEM images support that after 5% addition of elastomeric terpolymer, interaction loosens due to strong crystalline structure of Nylon 6.

  5. X-ray plane-wave diffraction effects in a crystal with third-order nonlinearity

    Energy Technology Data Exchange (ETDEWEB)

    Balyan, M. K., E-mail: mbalyan@ysu.am [Yerevan State University, Faculty of Physics (Armenia)

    2016-12-15

    The two-wave dynamical diffraction in the Laue geometry has been theoretically considered for a plane X-ray wave in a crystal with a third-order nonlinear response to the external field. An analytical solution to the problem stated is found for certain diffraction conditions. A nonlinear pendulum effect is analyzed. The nonlinear extinction length is found to depend on the incident-wave intensity. A pendulum effect of a new type is revealed: the intensities of the transmitted and diffracted waves periodically depend on the incidentwave intensity at a fixed crystal thickness. The rocking curves and Borrmann nonlinear effect are numerically calculated.

  6. Silica photonic crystal fiber structure in order to simplify the process of making them

    Directory of Open Access Journals (Sweden)

    Ashkan Ghanbari

    2014-04-01

    Full Text Available In this research, a new structure of photonic crystal fibers(PCFs will be proposed,in which instead of using the aire- holes in the cladding region, the flourine(2% doped solid silica rods in order to reduce the problems associated with deformities of air-holes in the cladding region will be used.Also, in the following, a few of the propagation charactristics of the proposed Photonic Crystal Fiber with a conventional silica Photonic Crystal Fiber such as, Normalized frequency,effective refractive index,total dispersion and higher order dispersions ( Group velocity dispersion and Third Order Dispersion will be analyzed and compared. Finally it will be observed that, the proposed PCF structure is much simpler than the conventional one in the fabrication process. But they are not suitable for femtosecond solitons propagation .Also, it will be shown that, the situation of the conventional Photonic Crystal Fiber is much better than the proposed structure in the femtosecond optical solitons propagation.

  7. Growth and PhysioChemical Properties of Second-Order Nonlinear Optical L-Threonine Single Crystals

    Directory of Open Access Journals (Sweden)

    G. Ramesh Kumar

    2009-01-01

    Full Text Available The present aim of the paper is to grow and to study the various properties of L-threonine amino acid single crystal in various aspects. Crystal growth of L-threonine single crystals has been carried out with the help of crystallization kinetics. pH and deuteration effects on the properties of the grown crystals have been studied and the results presented in a lucid manner. The various second-order NLO parameters were evaluated using anharmonic oscillator model. Particle and ion irradiation effects on structural, optical, and surface properties of the crystals have also been studied in detail.

  8. Asymmetric Dielectric Elastomer Composite Material

    Science.gov (United States)

    Stewart, Brian K. (Inventor)

    2014-01-01

    Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

  9. Modal theory of slow light enhanced third-order nonlinear effects in photonic crystal waveguides.

    Science.gov (United States)

    Chen, Tao; Sun, Junqiang; Li, Linsen

    2012-08-27

    In this paper, we derive the couple-mode equations for third-order nonlinear effects in photonic crystal waveguides by employing the modal theory. These nonlinear interactions include self-phase modulation, cross-phase modulation and degenerate four-wave mixing. The equations similar to that in nonlinear fiber optics could be expanded and applied for third-order nonlinear processes in other periodic waveguides. Based on the equations, we systematically analyze the group-velocity dispersion, optical propagation loss, effective interaction area, slow light enhanced factor and phase mismatch for a slow light engineered silicon photonic crystal waveguide. Considering the two-photon and free-carrier absorptions, the wavelength conversion efficiencies in two low-dispersion regions are numerically simulated by utilizing finite difference method. Finally, we investigate the influence of slow light enhanced multiple four-wave-mixing process on the conversion efficiency.

  10. Spontaneous Ferroelectric Order in a Bent-Core Smectic Liquid Crystal of Fluid Orthorhombic Layers

    Energy Technology Data Exchange (ETDEWEB)

    R Reddy; C Zhu; R Shao; E Korblova; T Gong; Y Shen; M Glaser; J Maclennan; D Walba; N Clark

    2011-12-31

    Macroscopic polarization density, characteristic of ferroelectric phases, is stabilized by dipolar intermolecular interactions. These are weakened as materials become more fluid and of higher symmetry, limiting ferroelectricity to crystals and to smectic liquid crystal stackings of fluid layers. We report the SmAP{sub F}, the smectic of fluid polar orthorhombic layers that order into a three-dimensional ferroelectric state, the highest-symmetry layered ferroelectric possible and the highest-symmetry ferroelectric material found to date. Its bent-core molecular design employs a single flexible tail that stabilizes layers with untilted molecules and in-plane polar ordering, evident in monolayer-thick freely suspended films. Electro-optic response reveals the three-dimensional orthorhombic ferroelectric structure, stabilized by silane molecular terminations that promote parallel alignment of the molecular dipoles in adjacent layers.

  11. Nanoparticle-Liquid Crystalline Elastomer Composites

    OpenAIRE

    Yan Ji; Terentjev, Eugene M.; Marshall, Jean E.

    2012-01-01

    Liquid crystalline elastomers (LCEs) exhibit a number of remarkable physical effects, including a uniquely high-stroke reversible mechanical actuation triggered by external stimuli. Fundamentally, all such stimuli affect the degree of liquid crystalline order in the polymer chains cross-linked into an elastic network. Heat and the resulting thermal actuation act by promoting entropic disorder, as does the addition of solvents. Photo-isomerization is another mechanism of actuation, reducing th...

  12. PROTON ORDERING MODEL OF PHASE TRANSITIONS IN HYDROGEN BONDED FERRIELECTRIC TYPE SYSTEMS: THE GPI CRYSTAL

    Directory of Open Access Journals (Sweden)

    I.Stasyuk

    2003-01-01

    Full Text Available A microscopic model based on the consideration of the proton ordering is proposed for describing the H-bonded ferroelectric crystalline systems with a complex structure of the hydrogen bond network. The model has been used for the investigation of thermodynamics and dielectric properties of the GPI crystal. The symmetry analysis of the order parameters responsible for the mixed (ferro- and antiferroelectric nature of ordering is performed within the model. The phase transition into the ferroelectric state is described. Changes in the dielectric susceptibility of the crystal are studied in the presence of the transverse external electric field acting along the c-axis. The results of measurements of temperature and field dependences of dielectric permittivity εc' in the paraelectric phase are presented. The microscopic mechanism of the observed effects is discussed based on the comparison of theoretical results and experimental data. A conclusion is made about the significant role of the ionic groups connected by hydrogen bonds in the charge transfer. So they make an important contribution into the polarizability of the GPI crystal along the direction of H-bonded chains.

  13. A Local Order Parameter-Based Method for Simulation of Free Energy Barriers in Crystal Nucleation.

    Science.gov (United States)

    Eslami, Hossein; Khanjari, Neda; Müller-Plathe, Florian

    2017-03-14

    While global order parameters have been widely used as reaction coordinates in nucleation and crystallization studies, their use in nucleation studies is claimed to have a serious drawback. In this work, a local order parameter is introduced as a local reaction coordinate to drive the simulation from the liquid phase to the solid phase and vice versa. This local order parameter holds information regarding the order in the first- and second-shell neighbors of a particle and has different well-defined values for local crystallites and disordered neighborhoods but is insensitive to the type of the crystal structure. The order parameter is employed in metadynamics simulations to calculate the solid-liquid phase equilibria and free energy barrier to nucleation. Our results for repulsive soft spheres and the Lennard-Jones potential, LJ(12-6), reveal better-resolved solid and liquid basins compared with the case in which a global order parameter is used. It is also shown that the configuration space is sampled more efficiently in the present method, allowing a more accurate calculation of the free energy barrier and the solid-liquid interfacial free energy. Another feature of the present local order parameter-based method is that it is possible to apply the bias potential to regions of interest in the order parameter space, for example, on the largest nucleus in the case of nucleation studies. In the present scheme for metadynamics simulation of the nucleation in supercooled LJ(12-6) particles, unlike the cases in which global order parameters are employed, there is no need to have an estimate of the size of the critical nucleus and to refine the results with the results of umbrella sampling simulations. The barrier heights and the nucleation pathway obtained from this method agree very well with the results of former umbrella sampling simulations.

  14. Effective second-order nonlinearity in acentric optical crystals with low symmetry.

    Science.gov (United States)

    Tzankov, Pancho; Petrov, Valentin

    2005-11-10

    We derive explicit expressions in the frame of the optical indicatrix for the second-order effective nonlinearity in biaxial crystals with point groups 2, m, and 1, governing the conversion efficiency in three-wave nonlinear optical interactions. The tabulated expressions for the monoclinic symmetry classes 2 and m are valid for all possible orientations of the optical indicatrix relative to the crystallographic frame and for propagation along an arbitrary direction outside the principal planes. They can be used for direct estimation of the effective nonlinearity in the same frame where the phase-matching loci are calculated. The relevant properties and conventions used for the newly emerging acentric monoclinic crystals belonging to the borate family are summarized and tabulated. The derivations are expected to help establish adherence to uniform nomenclature and conventions for these novel inorganic nonlinear crystals, and to eliminate ambiguity and increasing confusion in the literature and in the industrial specifications. The general expressions for the effective nonlinearity are reduced for triclinic crystals of point group 1 to simplified forms in the principal planes.

  15. Silica Fillers for elastomer Reinforement

    Energy Technology Data Exchange (ETDEWEB)

    Kohls, D.J.; Schaefer, D.W. (UCIN)

    2012-09-10

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  16. Silica Fillers for elastomer Reinforement

    Energy Technology Data Exchange (ETDEWEB)

    Kohls, D.J.; Schaefer, D.W. (UCIN)

    2009-08-26

    This article summarizes recent work on the structure of precipitated silica used in the reinforcement of elastomers. Silica has a unique morphology, consisting of multiple structural levels that can be controlled through processing. The ability to control and characterize the multiple structures of precipitated silica is an example of morphological engineering for reinforcement applications. In this summary of some recent research efforts using precipitated silica, small-angle scattering techniques are described and their usefulness for determining the morphology of silica in terms of primary particles, aggregates, and agglomerates are discussed. The structure of several different precipitated silica powders is shown as well as the mechanical properties of elastomers reinforced with these silica particles. The study of the mechanical properties of filled elastomer systems is a challenging and exciting topic for both fundamental science and industrial application. It is known that the addition of hard particulates to a soft elastomer matrix results in properties that do not follow a straightforward rule of mixtures. Research efforts in this area have shown that the properties of filled elastomers are influenced by the nature of both the filler and the matrix, as well as the interactions between them. Several articles have reviewed the influence of fillers like silica and carbon black on the reinforcement of elastomers. In general, the structure-property relationships developed for filled elastomers have evolved into the following major areas: Filler structure, hydrodynamic reinforcement, and interactions between fillers and elastomers.

  17. Photoluminescence polarization anisotropy for studying long-range structural ordering within semiconductor multi-atomic alloys and organic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Prutskij, T.; Percino, J. [Instituto de Ciencias, BUAP, Privada 17 Norte, No 3417, col. San Miguel Huyeotlipan, 72050, Puebla, Pue. (Mexico); Orlova, T. [Department of Chemical and Biochemical Engineering, University of Notre Dame, Notre Dame, IN (United States); Vavilova, L. [Ioffe Physical-Technical Institute, 26 Polytekhnicheskaya, St Petersburg 194021, Russian Federation (Russian Federation)

    2013-12-04

    Long-range structural ordering within multi-component semiconductor alloys and organic crystals leads to significant optical anisotropy and, in particular, to anisotropy of the photoluminescence (PL) emission. The PL emission of ternary and quaternary semiconductor alloys is polarized if there is some amount of the atomic ordering within the crystal structure. We analyze the polarization of the PL emission from the quaternary GaInAsP semiconductor alloy grown by Liquid Phase Epitaxy (LPE) and conclude that it could be caused by low degree atomic ordering within the crystal structure together with the thermal biaxial strain due to difference between the thermal expansion coefficients of the layer and the substrate. We also study the state of polarization of the PL from organic crystals in order to identify different features of the crystal PL spectrum.

  18. Second-order phase transition at high-pressure in GeS crystal

    Science.gov (United States)

    Hashimzade, F. M.; Huseinova, D. A.; Jahangirli, Z. A.; Mehdiyev, B. H.

    2014-12-01

    In this paper we give a theoretical proof of the existence of a second-order structural phase transition in the GeS at a pressure of 35.4 GPa. We use the plane-wave pseudopotential approach to the density functional theory in the local density approximation. The evidence of the phase transition is the abrupt change in the bulk modulus as the volume of the unit cell of the crystal changes continuously. We show that the phase transition is caused by the softening of the low-frequency fully symmetric interlayer mode with increasing pressure. As a result, phase transition of a displacement type takes place with the change of translational symmetry of the crystal from the simple orthorhombic to the base-centered orthorhombic (Pbnm(D2h16)→Cmcm(D2h17)).

  19. Organic holographic polymer dispersed liquid crystal distributed feedback laser from different diffraction orders

    Science.gov (United States)

    Liu, Minghuan; Liu, Yonggang; Zhang, Guiyang; Peng, Zenghui; Li, Dayu; Ma, Ji; Xuan, Li

    2016-11-01

    Holographic polymer dispersed liquid crystal (HPDLC) based distributed feedback (DFB) lasers were prepared with poly (-methoxy-5-(2‧-ethyl-hexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) film as the active medium layer. The HPDLC grating film was fabricated via holographic induced photopolymerization. The pure film spectra of MEH-PPV and the amplified spontaneous emission (ASE) spectrum were investigated. The laser device was single-longitudinal mode operation. The tunability of the HPDLC DFB laser was achieved by selecting different grating periods. The lasing performances were also characterized and compared from different diffraction orders. The lasing threshold increased with the diffraction order and the third order laser possessed the largest conversion efficiency in this device. The experimental results were in good agreement with the theoretical calculations.

  20. Tailor-Made Dispersion and Distribution of Stereocomplex Crystallites in Poly(l-lactide)/Elastomer Blends toward Largely Enhanced Crystallization Rate and Impact Toughness.

    Science.gov (United States)

    Luo, Yuanlin; Ju, Yilong; Bai, Hongwei; Liu, Zhenwei; Zhang, Qin; Fu, Qiang

    2017-06-29

    Stereocomplex (SC) crystallites, formed between poly(l-lactide) (PLLA) and poly(d-lactide), exhibit great potential to substantially enhance crystallization rate of PLLA-based materials as an eco-friendly nucleating agent. However, the nucleation efficiency of the SC crystallites is still far below an expected level, mostly on account of their strong aggregation tendency in PLLA/PDLA melts. Herein, taking PLLA/poly(ethylene-methyl acrylate-glycidyl methacrylate) (E-MA-GMA) blends as an example, we report a unique and facile strategy to control the dispersion and distribution of SC crystallites within the PLLA matrix by using elastomeric E-MA-GMA as carrier for the incorporation of PDLA. To do this, PDLA was first blended with E-MA-GMA or chemically grafted onto the E-MA-GMA. During subsequent melt-blending of PLLA and the E-MA-GMA/PDLA master batch, the PDLA chain clusters predispersed in the E-MA-GMA phase can gradually migrate into PLLA matrix and then collaborate with the matrix chains to form large amounts of tiny and well-dispersed SC crystallites. Compared with the SC-crystallite agglomerates formed by the direct melt-blending of PLLA and PDLA components, such tiny SC crystallites are much more effective in accelerating PLLA matrix crystallization. More interestingly, when PDLA chains are grafted onto the EMA-GMA, the formed SC crystallites tend to preferentially distribute at the blend interface and thus induce not only optimal nucleation efficiency but also superior impact toughness because these interface-localized SC crystallites can also serve as bridges to enhance interface adhesion. This work could open a new avenue in designing heat-resistant and supertough PLLA blends via controllable construction of SC crystallites.

  1. Natural gels: crystal-chemistry of short range ordered components in Al, Fe, and Si systems

    Energy Technology Data Exchange (ETDEWEB)

    Ildefonse, Ph.; Calas, G. [Paris-6 et 7 Univ. and IPGP, Lab. de Mineralogie-Cristallographie, UA CNRS 09, 75 (France)

    1997-07-01

    In this review, the most important inorganic natural gels are presented: opal, aluminosilicate (allophanes) and hydrous iron oxides and silicates. It is demonstrated that natural gels are ordered at the atomic scale. In allophanes, Al is distributed between octahedral and tetrahedral sites. The amount of Al increases as Al/Si ratio decreases. Si-rich allophane have a local structure around Al and Si very different of that is known in kaolinite or halloysite. Transformation of Si-rich allophanes to crystallized minerals implies dissolution-recrystallization processes. On the contrary, in iron silicate with Fe/Si = 0.72, Si and Fe environments are close to those found in nontronite. The gel transformation to Fe-smectite may occur by long range ordering during ageing. In ferric silicate gels, the similarity of local structure around Fe in poorly ordered precursors and what is known in crystallized minerals suggests a solid transformation during ageing. This difference between iron and aluminium is mainly due to the ability of Al to enter both tetrahedral and octahedral sites, while the affinity of iron for octahedral sites is higher at low temperature.

  2. High temperature sensing using higher-order-mode rejected sapphire-crystal fiber gratings

    Science.gov (United States)

    Zhan, Chun; Kim, Jae Hun; Lee, Jon; Yin, Stuart; Ruffin, Paul; Luo, Claire

    2007-09-01

    In this paper, we report the fabrication of higher-order-mode rejected fiber Bragg gratings (FBGs) in sapphire crystal fiber using infrared (IR) femtosecond laser illumination. The grating is tested in high temperature furnace up to 1600 degree Celsius. As sapphire fiber is only available as highly multimode fiber, a scheme to filter out higher order modes in favor for the fundamental mode is theoretically evaluated and experimentally demonstrated. The approach is to use an ultra thin sapphire crystal fiber (60 micron in diameter) to decrease the number of modes. The small diameter fiber also enables bending the fiber to certain radius which is carefully chosen to provide low loss for the fundamental mode LP01 and high loss for the other high-order modes. After bending, less-than-2-nm resonant peak bandwidth is achieved. The grating spectrum is improved, and higher resolution sensing measurement can be achieved. This mode filtering method is very easy to implement. Furthermore, the sapphire fiber is sealed with hi-purity alumina ceramic cement inside a flexible high temperature titanium tube, and the highly flexible titanium tube offers a robust packaging to sapphire fiber. Our high temperature sapphire grating sensor is very promising in extremely high temperature sensing application.

  3. Multimodal nonlinear optical polarizing microscopy of long-range molecular order in liquid crystals.

    Science.gov (United States)

    Lee, Taewoo; Trivedi, Rahul P; Smalyukh, Ivan I

    2010-10-15

    We demonstrate orientation-sensitive multimodal nonlinear optical polarizing microscopy capable of probing orientational, polar, and biaxial features of mesomorphic ordering in soft matter. This technique achieves simultaneous imaging in broadband coherent anti-Stokes Raman scattering, multiphoton excitation fluorescence, and multiharmonic generation polarizing microscopy modes and is based on the use of a single femtosecond laser and a photonic crystal fiber as sources of the probing light. We show the viability of this technique for mapping of three-dimensional patterns of molecular orientations and show that images obtained in different microscopy modes are consistent with each other.

  4. On the formulations of higher-order strain gradient crystal plasticity models

    DEFF Research Database (Denmark)

    Kuroda, M.; Tvergaard, Viggo

    2008-01-01

    Recently, several higher-order extensions to the crystal plasticity theory have been proposed to incorporate effects of material length scales that were missing links in the conventional continuum mechanics. The extended theories are classified into work-conjugate and non-work-conjugate types...... quantities do not appear explicitly. Instead, rates of crystallographic slip are influenced by back stresses that arise in response to spatial gradients of the geometrically necessary dislocation densities. The work-conjugate type and the non-work-conjugate type of theories have different theoretical...

  5. A Molecular View of Liquid Crystalline Elastomers and Gels

    Science.gov (United States)

    de Pablo, Juan

    2011-03-01

    A combination of Monte Carlo and molecular dynamics simulations is used to examine the order-disorder transitions that arise in model liquid crystalline elastomers and colloidal gels as a function of concentration and strain, respectively. Two models are considered. In the first, a lattice model is used to represent a colloidal gel of nematogens and nanoparticles. In the second, a cross-linked elastomer of Gay-Berne mesogens is adopted to examine the order-disroder transition that arises as a function of strain. The results of simulations are compared to those of recent experiments for these two classes of systems.

  6. Sustainable Elastomers from Renewable Biomass.

    Science.gov (United States)

    Wang, Zhongkai; Yuan, Liang; Tang, Chuanbing

    2017-07-18

    Sustainable elastomers have undergone explosive growth in recent years, partly due to the resurgence of biobased materials prepared from renewable natural resources. However, mounting challenges still prevail: How can the chemical compositions and macromolecular architectures of sustainable polymers be controlled and broadened? How can their processability and recyclability be enabled? How can they compete with petroleum-based counterparts in both cost and performance? Molecular-biomass-derived polymers, such as polymyrcene, polymenthide, and poly(ε-decalactone), have been employed for constructing thermoplastic elastomers (TPEs). Plant oils are widely used for fabricating thermoset elastomers. We use abundant biomass, such as plant oils, cellulose, rosin acids, and lignin, to develop elastomers covering a wide range of structure-property relationships in the hope of delivering better performance. In this Account, recent progress in preparing monomers and TPEs from biomass is first reviewed. ABA triblock copolymer TPEs were obtained with a soft middle block containing a soybean-oil-based monomer and hard outer blocks containing styrene. In addition, a combination of biobased monomers from rosin acids and soybean oil was formulated to prepare triblock copolymer TPEs. Together with the above-mentioned approaches based on block copolymers, multigraft copolymers with a soft backbone and rigid side chains are recognized as the first-generation and second-generation TPEs, respectively. It has been recently demonstrated that multigraft copolymers with a rigid backbone and elastic side chains can also be used as a novel architecture of TPEs. Natural polymers, such as cellulose and lignin, are utilized as a stiff, macromolecular backbone. Cellulose/lignin graft copolymers with side chains containing a copolymer of methyl methacrylate and butyl acrylate exhibited excellent elastic properties. Cellulose graft copolymers with biomass-derived polymers as side chains were

  7. Modeling surface segregation phenomena in the (111) surface of ordered Pt3Ti crystal.

    Science.gov (United States)

    Duan, Zhiyao; Zhong, Jun; Wang, Guofeng

    2010-09-21

    We investigated the surface segregation phenomena in the (111) surface of ordered Pt(3)Ti crystal using density functional theory (DFT) calculation (with no configuration sampling) and Monte Carlo (MC) simulation method (employing modified embedded atom method potentials and with extensive configuration sampling). Our DFT study suggested that the off-stoichiometric effect (specifically, a Pt concentration higher than 75 at. %) accounted for the experimentally observed Pt segregation to the outermost layer of the Pt(3)Ti (111). Our MC simulations predicted that in a Pt(3)Ti (111) sample with a Pt concentration slightly above 75 at. %, Pt atoms would segregate to the surface to form a pure Pt outermost layer, while the ordered Pt(3)Ti crystal structure would be maintained in the second layer and below. Moreover, our DFT calculations revealed that the d-band center of the Pt-segregated Pt(3)Ti (111) surface would downshift by 0.21 eV as compared to that of a pure Pt (111) surface. As a result, O adsorption energy on the Pt-segregated Pt(3)Ti (111) surface was found to be at least 0.16 eV weaker than that on the pure Pt (111) surface. Thus, we theoretically modeled the geometric and electronic structures of the Pt-segregated Pt(3)Ti (111) surface and further suggested that the Pt surface segregation could lead to enhanced catalytic activity for oxygen reduction reactions on Pt(3)Ti alloy catalysts.

  8. Studies of Second Order Optical Nonlinearities of 4-Aminobenzophenone (ABP) Single Crystal Films

    Science.gov (United States)

    Bhowmik, Achintya; Thakur, Mrinal

    1998-03-01

    Specific organic materials exhibit very high second order optical susceptibilities. Growth of single crystal films of these materials and characterization of nonlinear optical properties are necessary for implementation of device applications. We have grown large-area films ( 1 cm^2 area, 4 μm thick) of ABP by a modification of the shear method. Single crystal nature of the films was confirmed by polarized optical microscopy. X-ray diffraction analysis showed a [100] surface orientation. The absorption spectra revealed transparency from 390 nm to 1940 nm. Significant elements of the second order optical susceptibility tensor were measured by detailed SHG experiments using a Nd:YAG laser (1064 nm, 100 ps, 82 MHz). Second-harmonic power was measured using lock-in detection with carefully selected polarization conditions while the film was rotated about the propagation direction. Using LiNbØas the reference, d-coefficients of ABP were found to be d_23=7.2 pm/V and d_22=0.7 pm/V. Type-I and type-II phase-matching directions were identified on the film by analyzing the optical indicatrix surfaces at fundamental and second-harmonic frequencies.

  9. Self-healing elastomer system

    Science.gov (United States)

    Keller, Michael W. (Inventor); Sottos, Nancy R. (Inventor); White, Scott R. (Inventor)

    2009-01-01

    A composite material includes an elastomer matrix, a set of first capsules containing a polymerizer, and a set of second capsules containing a corresponding activator for the polymerizer. The polymerizer may be a polymerizer for an elastomer. The composite material may be prepared by combining a first set of capsules containing a polymerizer, a second set of capsules containing a corresponding activator for the polymerizer, and a matrix precursor, and then solidifying the matrix precursor to form an elastomeric matrix.

  10. Ion implanted dielectric elastomer circuits

    OpenAIRE

    O’Brien, Benjamin M.; Rosset, Samuel; Anderson, Iain A.; Shea, Herbert R.

    2013-01-01

    Starfish and octopuses control their infinite degree of- freedom arms with panache—capabilities typical of nature where the distribution of reflex-like intelligence throughout soft muscular networks greatly outperforms anything hard, heavy, and man-made. Dielectric elastomer actuators show great promise for soft artificial muscle networks. One way to make them smart is with piezo-resistive Dielectric Elastomer Switches (DES) that can be combined with artificial muscles to create arbitrary dig...

  11. Voltage-stabilised elastomers with increased relative permittivity and high electrical breakdown strength by means of phase separating binary copolymer blends of silicone elastomers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Yu, Liyun; Skov, Anne Ladegaard

    2017-01-01

    Increased electrical breakdown strength and increased dielectric permittivity of silicone-based dielectric elastomers are achieved by means of the addition of so-called voltage-stabilisers prepared from PDMS–PPMS copolymers as well as PDMS–PEG copolymers in order to compensate for the negative...... effect of softness on electrical stability of silicone elastomers. The voltage-stabilised elastomer, incorporating a high-permittivity PDMS–PEG copolymer, possesses increased relative permittivity, high electrical breakdown strength, excellent network integrity and low dielectric loss and paves the way...

  12. Crystal growth and characterization of semi-organic 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals for third-order nonlinear optical (NLO) applications

    Science.gov (United States)

    Vediyappan, Sivasubramani; Arumugam, Raja; Pichan, Karuppasamy; Kasthuri, Ramachandran; Muthu, Senthil Pandian; Perumal, Ramasamy

    2017-12-01

    Semi-organic nonlinear optical (NLO) 2-amino-5-nitropyridinium bromide (2A5NPBr) single crystals have been grown by slow evaporation solution technique (SEST) with the growth period of 60 days. The single-crystal XRD analysis confirms the unit cell parameters of the grown crystal. The crystallinity of grown 2A5NPBr was analyzed by powder X-ray diffraction (PXRD) measurement. The presence of functional groups of 2A5NPBr crystal was confirmed by Fourier transform infrared (FTIR) spectrum analysis. The optical transmittance of the grown crystal was analyzed by UV-Vis-NIR analysis. It shows good transparency in the visible and NIR region and it is favorable for nonlinear optical (NLO) device applications. The chemical etching study was carried out and it reveals that the grown crystal has less dislocation density. The photoconductivity study reveals that the grown crystal possesses positive photoconductive nature. The thermal stability of the crystal has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA). The dielectric constant and dielectric loss as a function of frequency were measured. The electronic polarizability (α) of 2A5NPBr molecule has been calculated theoretically by different ways such as Penn analysis, Clausius-Mossotti relation, Lorentz-Lorenz equation, optical bandgap, and coupled dipole method (CDM). The obtained values of electronic polarizability (α) are in good agreement with each other. Laser damage threshold (LDT) of 2A5NPBr crystal has been measured using Nd:YAG laser with the wavelength of 1064 nm. Third-order nonlinear optical property of the grown crystal was studied by Z-scan technique using He-Ne laser of wavelength 632.8 nm.

  13. Indentation of a stretched elastomer

    Science.gov (United States)

    Zheng, Yue; Crosby, Alfred J.; Cai, Shengqiang

    2017-10-01

    Indentation has been intensively used to characterize mechanical properties of soft materials such as elastomers, gels, and soft biological tissues. In most indentation measurements, residual stress or stretch which can be commonly found in soft materials is ignored. In this article, we aim to quantitatively understand the effects of prestretches of an elastomer on its indentation measurement. Based on surface Green's function, we analytically derive the relationship between indentation force and indentation depth for a prestretched Neo-Hookean solid with a flat-ended cylindrical indenter as well as a spherical indenter. In addition, for a non-equal biaxially stretched elastomer, we obtain the equation determining the eccentricity of the elliptical contacting area between a spherical indenter and the elastomer. Our results clearly demonstrate that the effects of prestretches of an elastomer on its indentation measurement can be significant. To validate our analytical results, we further conduct correspondent finite element simulations of indentation of prestretched elastomers. The numerical results agree well with our analytical predictions.

  14. Molecular mechanism of melting of a helical polymer crystal: Role of conformational order, packing and mobility of polymers

    Science.gov (United States)

    Cheerla, Ramesh; Krishnan, Marimuthu

    2018-03-01

    The molecular mechanism of melting of a superheated helical polymer crystal has been investigated using isothermal-isobaric molecular dynamics simulation that allows anisotropic deformation of the crystal lattice. A detailed microscopic analysis of the onset and progression of melting and accompanying changes in the polymer conformational order, translational, and orientation order of the solid along the melting pathway is presented. Upon gradual heating from room temperature to beyond the melting point at ambient pressure, the crystal exhibits signatures of premelting well below the solid-to-liquid melting transition at the melting point. The melting transition is manifested by abrupt changes in the crystal volume, lattice energy, polymer conformation, and dynamical properties. In the premelting stage, the crystal lattice structure and backbone orientation of the polymer chains are retained but with the onset of weakening of long-range helical order and interchain packing of polymers perpendicular to the fibre axis of the crystal. The premelting also marks the onset of conformational defects and anisotropic solid-state diffusion of polymers along the fibre axis. The present study underscores the importance of the interplay between intermolecular packing, interactions, and conformational dynamics at the atomic level in determining the macroscopic melting behavior of polymer crystals.

  15. Study Of The Mechanical Behavior Of Elastomer Protective Materials

    Directory of Open Access Journals (Sweden)

    Lotfi Harrabi

    2017-07-01

    Full Text Available In order to study the mechanical behaviour of elastomers at large deformations a theoretical description was developed for the loading-unloading hysteresis loop at large deformations and as a function of the strain rate. Bergstrm and Boyces proposition that the elastomer behaviour is controlled by two contributions the first one corresponding to the equilibrium state and the second one to a non-linear rate-dependent deviation from that equilibrium state and their use of Zeners rheological model were applied to an uniaxial tension configuration. A validation of the description was performed with nitrile rubber. A good agreement of the theoretical description with experimental results was obtained. This simple description of the hysteresis behaviour of elastomers as a function of the strain rate provides a useful tool for estimating the mechanical behaviour at various strain rates with potential application in the design of protective gloves.

  16. Lyotropic liquid crystal engineering-ordered nanostructured small molecule amphiphile self-assembly materials by design.

    Science.gov (United States)

    Fong, Celesta; Le, Tu; Drummond, Calum J

    2012-02-07

    Future nanoscale soft matter design will be guided to a large extent by the teachings of amphiphile (lipid or surfactant) self-assembly. Ordered nanostructured lyotropic liquid crystalline mesophases may form in select mixtures of amphiphile and solvent. To reproducibly engineer the low energy amphiphile self-assembly of materials for the future, we must first learn the design principles. In this critical review we discuss the evolution of these design rules and in particular discuss recent key findings regarding (i) what drives amphiphile self-assembly, (ii) what governs the self-assembly structures that are formed, and (iii) how can amphiphile self-assembly materials be used to enhance product formulations, including drug delivery vehicles, medical imaging contrast agents, and integral membrane protein crystallisation media. We focus upon the generation of 'dilutable' lyotropic liquid crystal phases with two- and three-dimensional geometries from amphiphilic small molecules (225 references). This journal is © The Royal Society of Chemistry 2012

  17. Electro-osmosis of nematic liquid crystals under weak anchoring and second-order surface effects

    Science.gov (United States)

    Poddar, Antarip; Dhar, Jayabrata; Chakraborty, Suman

    2017-07-01

    Advent of nematic liquid crystal flows has attracted renewed attention in view of microfluidic transport phenomena. Among various transport processes, electro-osmosis stands as one of the efficient flow actuation mechanisms through narrow confinements. In the present study, we explore the electrically actuated flow of an ordered nematic fluid with ionic inclusions, taking into account the influences from surface-induced elasticity and electrical double layer (EDL) phenomena. Toward this, we devise the coupled flow governing equations from fundamental free-energy analysis, considering the contributions from first- and second-order elastic, dielectric, flexoelectric, charged surface polarization, ionic and entropic energies. The present study focuses on the influence of surface charge and elasticity effects in the resulting linear electro-osmosis through a slit-type microchannel whose surfaces are chemically treated to display a homeotropic-type weak anchoring state. An optical periodic stripe configuration of the nematic director has been observed, especially for higher electric fields, wherein the Ericksen number for the dynamic study is restricted to the order of unity. Contrary to the isotropic electrolytes, the EDL potential in this case was found to be dependent on the external field strength. Through a systematic investigation, we brought out the fact that the wavelength of the oscillating patterns is dictated mainly by the external field, while the amplitude depends on most of the physical variables ranging from the anchoring strength and the flexoelectric coefficients to the surface charge density and electrical double layer thickness.

  18. NMR studies of a D/sub 2/ single crystal in the ordered phase

    Energy Technology Data Exchange (ETDEWEB)

    Banke, R.; Li, X.; Clarkson, D.; Meyer, H.

    1988-07-01

    The authors report the first experimental study of the NMR lineshape anisotropy in the orientationally ordered cubic phase of a D/sub 2/ single crystal. The para-D/sub 2/ concentration covered the range 0.72 < X < 0.82. The observed line shapes were obtained by means of Fourier transform techniques from the solid echoes recorded with a pulsed NMR spectrometer operating at 5.9 MHz. Theoretical line shapes and their second moments for p-D/sub 2/ (with angular momentum J = 1 and spin I = 1) and for o-D/sub 2/ (with J = 0, I = 2) were calculated as a function of the applied field direction from the theory by A.B. Harris. Good agreement was obtained for all directions, provided that, just as for solid H/sub 2/ a Gaussian function for the distribution of molecular axial alignment was assumed with an rms spreading angle of approx. 6 deg for X = 0.77. No change in the anisotropy of the second moment in the disordered phase was detected between the initial (hcp) crystal and after repeated thermal cyclings through the martensitic transition. This result implies no change in the orientation of the plane for the sliding nets during repeated passages through the transition. Furthermore, they report measurements of the longitudinal relaxation time for both p-D/sub 2/ and o-H/sub 2/ versus T over the temperature range 0.5 < T < 3.5 K. The complex behavior reported previously for both H/sub 2/ and D/sub 2/ was confirmed. Measurements of the relaxation times as a function of the applied field direction in the ordered phase at 1.2 K showed no anisotropy within experimental error, and this result is discussed in the light of predictions by Hardy and Berlinsky. Finally, the polarization of the J = 0 molecules is studied as a function of the concentration X of the J = 1 molecules and their state of orientational order over a wide range of X and T in the ordered and disordered states.

  19. Bond orientational order in liquids: Towards a unified description of water-like anomalies, liquid-liquid transition, glass transition, and crystallization: Bond orientational order in liquids.

    Science.gov (United States)

    Tanaka, Hajime

    2012-10-01

    There are at least three fundamental states of matter, depending upon temperature and pressure: gas, liquid, and solid (crystal). These states are separated by first-order phase transitions between them. In both gas and liquid phases a complete translational and rotational symmetry exist, whereas in a solid phase both symmetries are broken. In intermediate phases between liquid and solid, which include liquid crystal and plastic crystal phases, only one of the two symmetries is preserved. Among the fundamental states of matter, the liquid state is the most poorly understood. We argue that it is crucial for a better understanding of liquids to recognize that a liquid generally has the tendency to have a local structural order and its presence is intrinsic and universal to any liquid. Such structural ordering is a consequence of many-body correlations, more specifically, bond angle correlations, which we believe are crucial for the description of the liquid state. We show that this physical picture may naturally explain difficult unsolved problems associated with the liquid state, such as anomalies of water-type liquids (water, Si, Ge, ...), liquid-liquid transition, liquid-glass transition, crystallization and quasicrystal formation, in a unified manner. In other words, we need a new order parameter representing a low local free-energy configuration, which is a bond orientational order parameter in many cases, in addition to a density order parameter for the physical description of these phenomena. Here we review our two-order-parameter model of liquid and consider how transient local structural ordering is linked to all of the above-mentioned phenomena. The relationship between these phenomena is also discussed.

  20. Anchoring behavior, orientational order, and reorientation dynamics of nematic liquid crystal droplets dispersed in cross-linked polymer networks.

    Science.gov (United States)

    Roussel, Frédérick; Fung, Bing M

    2003-04-01

    The orientational ordering and the electro-optical properties of nematic liquid crystal (LC) droplets confined to cross-linked polymer networks are investigated as a function of the anchoring conditions at the polymer-liquid crystal interface. Normal alignment (homeotropic) or parallel alignment (planar) inside LC droplets was controlled by using acrylate polymers with appropriate side chains. Drastic changes in the reorientation dynamics of the confined nematic liquid crystal phase are observed, as well as in the orientational ordering of the phase-separated LC which was investigated by 13C-NMR (nuclear magnetic resonance) spectroscopy. The cross-link density of the polymer network also affects the orientational ordering and the electro-optical properties of the confined LC phase. Faster switching times and higher-order parameters were found for samples with LC droplets exhibiting planar anchoring.

  1. Ultrafast all-optical order-to-chaos transition in silicon photonic crystal chips

    KAUST Repository

    Bruck, Roman

    2016-06-08

    The interaction of light with nanostructured materials provides exciting new opportunities for investigating classical wave analogies of quantum phenomena. A topic of particular interest forms the interplay between wave physics and chaos in systems where a small perturbation can drive the behavior from the classical to chaotic regime. Here, we report an all-optical laser-driven transition from order to chaos in integrated chips on a silicon photonics platform. A square photonic crystal microcavity at telecom wavelengths is tuned from an ordered into a chaotic regime through a perturbation induced by ultrafast laser pulses in the ultraviolet range. The chaotic dynamics of weak probe pulses in the near infrared is characterized for different pump-probe delay times and at various positions in the cavity, with high spatial accuracy. Our experimental analysis, confirmed by numerical modelling based on random matrices, demonstrates that nonlinear optics can be used to control reversibly the chaotic behavior of light in optical resonators. (Figure presented.) . © 2016 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  2. Liquid crystal ordering of DNA and RNA oligomers with partially overlapping sequences

    Energy Technology Data Exchange (ETDEWEB)

    Zanchetta, G; Buscaglia, M; Bellini, T [Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Universita di Milano, Milano (Italy); Nakata, M; Clark, N A [Department of Physics and Liquid Crystal Materials Research Center, University of Colorado, Boulder, CO 80309-0390 (United States)], E-mail: noel.clark@colorado.edu, E-mail: tommaso.bellini@unimi.it

    2008-12-10

    We have recently shown that solutions of very short double-stranded B-DNA and A-RNA, down to six base pairs in length, can self-organize into chiral nematic and columnar liquid crystal (LC) phases. These observations were made on fully complementary sequences forming duplexes with blunt ends, where the LC ordering is due to base stacking forces promoting end-to-end aggregation of duplexes into living-polymer-type structures. Here we report LC formation in solutions of DNA and RNA 14mers forming double helices having single-stranded dangling ends that are 'sticky', i.e., mutually complementary with similar ends on other duplexes. This finding widens the conditions for spontaneous long range ordering in oligomeric nucleic acids, thus strengthening the notion that nucleic acids have remarkable self-assembly capability. Quantitative analysis of the phase diagram enables the extraction, within a nearest-neighbor interaction approximation, of the free energy associated with the pairing and stacking of nucleobases.

  3. Influence of Simple Electrolytes on the Orientational Ordering of Thermotropic Liquid Crystals at Aqueous Interfaces

    Science.gov (United States)

    Carlton, Rebecca J.; Gupta, Jugal K.; Swift, Candice L.; Abbott, Nicholas L.

    2011-01-01

    We report orientational anchoring transitions at aqueous interfaces of a water-immiscible, thermotropic liquid crystal (LC; nematic phase of 4′-pentyl-4-cyanobiphenyl) that are induced by changes in pH of the aqueous solution and the addition of simple electrolytes (NaCl) to the aqueous phase. Whereas measurements of the zeta potential on the aqueous side of the interface of LC-in-water emulsions prepared with 5CB confirm pH-dependent formation of an electrical double layer extending into the aqueous phase, quantification of the orientational ordering of the LC leads to the proposition that an electrical double layer is also formed on the LC-side of the interface with an internal electric field that drives the LC anchoring transition. Further support for this conclusion is obtained from measurements of the dependence of LC ordering on pH and ionic strength, as well as a simple model based on the Poisson-Boltzmann equation from which we calculate the contribution of an electrical double layer to the orientational anchoring energy of the LC. Overall, the results presented herein provide new fundamental insights into ionic phenomena at LC-aqueous interfaces, and expand the range of solutes known to cause orientational anchoring transitions at LC-aqueous interfaces beyond previously examined amphiphilic adsorbates. PMID:22106820

  4. Well-ordered polymer nano-fibers with self-cleaning property by disturbing crystallization process

    Science.gov (United States)

    Yang, Qin; Luo, Zhuangzhu; Tan, Sheng; Luo, Yimin; Wang, Yunjiao; Zhang, Zhaozhu; Liu, Weimin

    2014-07-01

    Bionic self-cleaning surfaces with well-ordered polymer nano-fibers are firstly fabricated by disturbing crystallization during one-step coating-curing process. Orderly thin (100 nm) and long (5-10 μm) polymer nano-fibers with a certain direction are fabricated by external macroscopic force ( F blow) interference introduced by H2 gas flow, leading to superior superhydrophobicity with a water contact angle (WCA) of 170° and a water sliding angle (WSA) of 0-1°. In contrast, nano-wires and nano-bridges (1-8 μm in length/10-80 nm in width) are generated by "spinning/stretching" under internal microscopic force ( F T) interference due to significant temperature difference in the non-uniform cooling medium. The findings provide a novel theoretical basis for controllable polymer "bionic lotus" surface and will further promote practical application in many engineering fields such as drag-reduction and anti-icing.

  5. Photoisomerisation of azobenzene crystals in aqueous dispersions examined by higher order derivative spectra.

    Science.gov (United States)

    Ichimura, Kunihiro

    2015-01-28

    Photo-induced UV-Vis spectral changes of azobenzene (Az) in solution and aqueous crystalline dispersions were analysed by means predominantly of fourth order derivatives. Weak bands due to vibration level transitions (VLT) of E-isomers in solution were well-resolved in derivatives to estimate conversion of photoisomerisation by tracing extrema of a VLT sub-peak. The photo-induced derivative-spectral changes of Az crystals dispersed in aqueous PVA solutions generated many common crossing points to indicate that Az dissolves partially in a PVA solution to lead to photoisomerisation in a homogeneous phase and the reversible alteration of particle size. The solid-state photoisomerisation of Az was investigated by the preparation of PVA-free aqueous dispersions of powdery nanohybrids comprised of Az and silica nanoparticles. The fourth order derivatives of spectral changes revealed that the photochemical process involves three kinds of species including non-aggregated and aggregated E-isomers as well as Z-isomers.

  6. Trajectory analysis of high-order-harmonic generation from periodic crystals

    Science.gov (United States)

    Ikemachi, Takuya; Shinohara, Yasushi; Sato, Takeshi; Yumoto, Junji; Kuwata-Gonokami, Makoto; Ishikawa, Kenichi L.

    2017-04-01

    We theoretically study high-order-harmonic generation (HHG) from solids driven by intense laser pulses using a one-dimensional model periodic crystal. By numerically solving the time-dependent Schrödinger equation directly on a real-space grid, we successfully reproduce experimentally observed unique features of solid-state HHG such as the linear cutoff-energy scaling and the sudden transition from a single- to multiple-plateau structure. Based on the simulation results, we propose a simple model that incorporates vector-potential-induced intraband displacement, interband tunneling, and recombination with the valence-band hole. One key parameter is the peak-to-valley amplitude of the pulse vector potential, which determines the crystal momentum displacement during the half cycle. When the maximum peak-to-valley amplitude Apeak reaches the half width π/a of the Brillouin zone with a being the lattice constant, the HHG spectrum exhibits a transition from a single- to multiple-plateau structure, and even further plateaus appear at Apeak=2/π a ,3/π a ,⋯ . The multiple cutoff positions are given as functions of Apeak and the second maximum Apeak', in terms of the energy difference between different bands. Using our recipe, one can draw electron trajectories in the momentum space, from which one can deduce, for example, the time-frequency structure of HHG without elaborate quantum-mechanical calculations. Finally, we reveal that the cutoff positions depend on not only the intensity and wavelength of the pulse, but also its duration, in marked contrast to the gas-phase case. Our model can be viewed as a solid-state and momentum-space counterpart of the familiar three-step model, highly successful for gas-phase HHG, and provide a unified basis to understand HHG from solid-state materials and gaseous media.

  7. Silicone-based Dielectric Elastomers

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard

    energy efficient solutions are highly sought. These properties allow for interesting products ranging very broadly, e.g. from eye implants over artificial skins over soft robotics to huge wave energy harvesting plants. All these products utilize the inherent softness and compliance of the dielectric...... investigated but rarely discussed in the context of mechani-cal integrity and thus product reliability. Focus here is on long-term reliability of the dielectric elastomers and how to achieve this by means of careful elastomer design. This thesis presents methods and results of analyses acquired in the cross......-disciplinary, collaborative effort on dielectric elastomers funded by Innovationsfonden Denmark (formerly Advanced Technology Foundation) with the materials workgroup headed by the author. Main contributors to the work have been research scientists at Danfoss PolyPower, colleagues from the Danish Polymer Centre, as well as 7...

  8. Growth, structural and characterization of a novel third order nonlinear optical Benzimidazolium Maleate single crystal

    Science.gov (United States)

    Amudha, M.; Muthu, S.; Gunasekaran, B.; Praveen Kumar, P.

    2017-10-01

    Good optical quality single crystals of Benzimidazolium Maleate (BML), a new organic charge transfer molecular complex salt, were grown successfully by the slow evaporation solution growth technique using deionised water as solvent at room temperature. The grown crystals of BML were characterised by single crystal X-ray diffraction (XRD) and powder XRD which confirm that the crystal belongs to monoclinic system with the centrosymmetric space group P21/n. The presence of functional groups in the grown crystal was confirmed by Fourier transform infrared spectral analysis. The BML crystal is thermally stable up to 147.7 °C and it is found by TG-DTA analysis. The transparency of the crystal was identified using UV-Vis spectrophotometer. Vickers microhardness analysis shows the mechanical stability of the grown crystal. The dependence of dielectric properties with frequency and temperature were also studied. Nonlinear optical absorption coefficient determined from open aperture Z-scan analysis revealed that the BML crystal can serve as a promising candidate for optical limiting applications.

  9. Studies on structure, growth and characterization of third order nonlinear optical 2-amino-5-chloropyridinium-4-amino benzoate single crystal

    Directory of Open Access Journals (Sweden)

    Krishnakumar M.

    2017-07-01

    Full Text Available Optically transparent single crystals of 2-amino-5-chloropyridinium-4-amino benzoate (2A5CP4AB were grown at room temperature using solution growth technique. The structure was solved with a support of single crystal XRD, which revealed that the title compound belongs to the monoclinic crystal system having centrosymmetric space group P21/n. The UV-Vis spectrum and photoluminescence properties of the title compound showed the optical transmittance and emission behavior of the compound. The optical band gap was evaluated using the Tauc plot and it was found to be about 3.53 eV. The third order nonlinear optical behavior of the crystal was determined using Z-scan technique. Mechanical properties of the title compound were studied using Vickers microhardness study.

  10. Self-assembly, Condensation, and Order in Aqueous Lyotropic Chromonic Liquid Crystals Crowded with Additives

    Energy Technology Data Exchange (ETDEWEB)

    Tortora, L.; Park, H; Kang, S; Savaryn, V; Hong, S; Kaznatcheev, K; Finotello, D; Sprunt, S; Kumar, S; Lavrentovich, O

    2010-01-01

    Dense multicomponent systems with macromolecules and small solutes attract a broad research interest as they mimic the molecularly crowded cellular interiors. The additives can condense and align the macromolecules, but they do not change the degree of covalent polymerization. We chose a lyotropic chromonic liquid crystal with reversibly and non-covalently assembled aggregates as a much softer system, reminiscent of 'living polymers', to demonstrate that small neutral and charged additives cause condensation of aggregates with ensuing orientational and positional ordering and nontrivial morphologies of phase separation, such as tactoids and toroids of the nematic and hexagonal columnar phase coexisting with the isotropic melt. Scanning transmission X-ray microscopy (STXM) with near edge X-ray absorption fine structure (NEXAFS) analysis as well as fluorescent microscopy demonstrates segregation of the components. The observations suggest that self-assembly of chromonic aggregates in the presence of additives is controlled by both entropy effects and by specific molecular interactions and provide a new route to the regulated reversible assembly of soft materials formed by low-molecular weight components.

  11. Self-assembly, condensation, and order in aqueous lyotropic chromonic liquid crystals crowded with additives

    Energy Technology Data Exchange (ETDEWEB)

    Tortora, Luana; Park, Heung-Shik; Kang, Shin-Woong; Savaryn, Victoria; Hong, Seung-Ho; Kaznatcheev, Konstantine; Finotello, Daniele; Sprunt, Samuel; Kumar, Satyendra; Lavrentovich, Oleg D. (Chonbuk); (Kent); (BNL)

    2012-09-06

    Dense multicomponent systems with macromolecules and small solutes attract a broad research interest as they mimic the molecularly crowded cellular interiors. The additives can condense and align the macromolecules, but they do not change the degree of covalent polymerization. We chose a lyotropic chromonic liquid crystal with reversibly and non-covalently assembled aggregates as a much softer system, reminiscent of 'living polymers', to demonstrate that small neutral and charged additives cause condensation of aggregates with ensuing orientational and positional ordering and nontrivial morphologies of phase separation, such as tactoids and toroids of the nematic and hexagonal columnar phase coexisting with the isotropic melt. Scanning transmission X-ray microscopy (STXM) with near edge X-ray absorption fine structure (NEXAFS) analysis as well as fluorescent microscopy demonstrates segregation of the components. The observations suggest that self-assembly of chromonic aggregates in the presence of additives is controlled by both entropy effects and by specific molecular interactions and provide a new route to the regulated reversible assembly of soft materials formed by low-molecular weight components.

  12. Elastomer Spacers in Fire Conditions

    Directory of Open Access Journals (Sweden)

    Roszkowski Paweł

    2017-09-01

    Full Text Available In the paper, fire resistance of linear joints seal made of elastomer spacers under standard fire conditions, and thermal degradation range of EPDM elastomeric spacers are investigated. The geometry of elastomer spacer joints is important not only for their load capacity under normal conditions - thickness, width, and cavity depth can also influence fire resistance performance. Linear joints of different thicknesses and widths have been tested. The fire insulation and fire integrity were verified for various arrangements. Relatively low thermal degradation rates have been measured, given that EPDM is a combustible material.

  13. Elastomer Spacers in Fire Conditions

    Science.gov (United States)

    Roszkowski, Paweł; Sędłak, Bartłomiej; Sulik, Paweł

    2017-09-01

    In the paper, fire resistance of linear joints seal made of elastomer spacers under standard fire conditions, and thermal degradation range of EPDM elastomeric spacers are investigated. The geometry of elastomer spacer joints is important not only for their load capacity under normal conditions - thickness, width, and cavity depth can also influence fire resistance performance. Linear joints of different thicknesses and widths have been tested. The fire insulation and fire integrity were verified for various arrangements. Relatively low thermal degradation rates have been measured, given that EPDM is a combustible material.

  14. Fracture studies of poly(propylene)/elastomer blend with {beta}-form nucleating agent

    Energy Technology Data Exchange (ETDEWEB)

    Bai Hongwei [Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Wang Yong, E-mail: yongwang1976@163.com [Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Zhang Danli; Xiao Chengquan; Song Bo; Li Yanli; Han Liang [Key Laboratory of Advanced Technologies of Materials (Ministry of Education), School of Materials Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2009-07-15

    Poly(propylene)/elastomer blends with {beta}-form nucleating agent ({beta}-NA) aryl amides compound (TMB-5) were prepared. The effects of {beta}-NA on crystallization, melting behaviors and elastomer morphologies of PP/elastomer blends were studied through polarization optical microscope (POM), differential scanning calorimetry (DSC) and scanning electronic microscope (SEM). The fracture behaviors, including notched Izod impact fracture and single-edge notched tensile (SENT) fracture, were comparatively studied to establish the role of NA in improving the fracture toughness of PP/elastomer blends. Our results showed that the presence of {beta}-NA leads to determinable {beta}-PP formation in the blends, and as a consequence the fracture toughness of the blend is improved dramatically. Compared with notched Izod impact testing, which can efficiently characterize the fracture toughness of the blends only at lower elastomer content, SENT testing provides more detail of fracture behavior in all the compositions. Furthermore, SENT test shows that the significant improvement in fracture toughness of PP/elastomer/{beta}-NA is contributed to the simultaneous enhancement of crack initiation energy and crack propagation energy, but largely dominated by crack propagation stage.

  15. How does static stretching decrease the dielectric constant of VHB 4910 elastomer?

    Science.gov (United States)

    Vu-Cong, T.; Nguyen-Thi, N.; Jean-Mistral, C.; Sylvestre, A.

    2014-03-01

    Subject to a voltage, dielectric elastomers deform by the effect of Maxwell stress which is depended directly on the dielectric constant of the material. The combination of large strain, soft elastic response and good dielectric properties has established VHB 4910 elastomer as the most used material for dielectric elastomer actuators. However, the effect of stretch on the dielectric constant for this elastomer is much debated topic while controversy results are demonstrated in the literature. The dielectric constant of this material is studied and demonstrated that it decreases slightly or hugely among the stretch but any pertinent response and any physic explications are validated by the scientific community. In this paper, we presented a detail study about dielectric behavior of VHB 4910 elastomer versus a broadband of stretch and temperature. We found that the dielectric constant of this material depends strongly on the stretch following a polynomial law. Among all the explanations of stretch dependence of the dielectric constant of VHB 4910 in the literature: the crystallization, the change of glass transition temperature, the decrease of dipole orientation, the electrostriction effect under stress; and based on our experimental result, we conclude that the decrease of dipole orientation seems the main reason to the drop of dielectric constant of VHB 4910 elastomer versus the stretch. We proposed also an accurate model describing the dielectric constant of this material for a large range of stretch and temperature.

  16. Actuation of Thin Nematic Elastomer Sheets with Controlled Heterogeneity

    Science.gov (United States)

    Plucinsky, Paul; Lemm, Marius; Bhattacharya, Kaushik

    2017-09-01

    Nematic elastomers and glasses deform spontaneously when subjected to temperature changes. This property can be exploited in the design of heterogeneously patterned thin sheets that deform into a non-trivial shape when heated or cooled. In this paper, we start from a variational formulation for the entropic elastic energy of liquid crystal elastomers and we derive an effective two-dimensional metric constraint, which links the deformation and the heterogeneous director field. Our main results show that satisfying the metric constraint is both necessary and sufficient for the deformation to be an approximate minimizer of the energy. We include several examples which show that the class of deformations satisfying the metric constraint is quite rich.

  17. Improvements in the order, isotropy and electron density of glypican-1 crystals by controlled dehydration

    Energy Technology Data Exchange (ETDEWEB)

    Awad, Wael [Lund University, Box 124, 221 00 Lund (Sweden); Cairo University, Cairo (Egypt); Svensson Birkedal, Gabriel [Lund University, Biomedical Center A13, 221 84 Lund (Sweden); Thunnissen, Marjolein M. G. M. [Lund University, Box 124, 221 00 Lund (Sweden); Lund University, Box 188, 221 00 Lund (Sweden); Mani, Katrin [Lund University, Biomedical Center A13, 221 84 Lund (Sweden); Logan, Derek T., E-mail: derek.logan@biochemistry.lu.se [Lund University, Box 124, 221 00 Lund (Sweden)

    2013-12-01

    The anisotropy of crystals of glypican-1 was significantly reduced by controlled dehydration using the HC1 device, allowing the building of previously disordered parts of the structure. The use of controlled dehydration for improvement of protein crystal diffraction quality is increasing in popularity, although there are still relatively few documented examples of success. A study has been carried out to establish whether controlled dehydration could be used to improve the anisotropy of crystals of the core protein of the human proteoglycan glypican-1. Crystals were subjected to controlled dehydration using the HC1 device. The optimal protocol for dehydration was developed by careful investigation of the following parameters: dehydration rate, final relative humidity and total incubation time T{sub inc}. Of these, the most important was shown to be T{sub inc}. After dehydration using the optimal protocol the crystals showed significantly reduced anisotropy and improved electron density, allowing the building of previously disordered parts of the structure.

  18. Synthesis of antibacterial amphiphilic elastomer based on polystyrene-block-polyisoprene-block-polystyrene via thiol-ene addition

    Energy Technology Data Exchange (ETDEWEB)

    Keleş, Elif, E-mail: elifkelesh@hotmail.com [Department of Chemistry, Bülent Ecevit University, Zonguldak 67100 (Turkey); Hazer, Baki, E-mail: bhazer2@yahoo.com [Department of Chemistry, Bülent Ecevit University, Zonguldak 67100 (Turkey); Cömert, Füsun B. [Department of Microbiology, Faculty of Medicine, Bülent Ecevit University, 67600 Zonguldak (Turkey)

    2013-04-01

    A new type of amphiphilic antibacterial elastomer has been described. Thermoplastic elastomer, polystyrene–block-polyisoprene–block-polystyrene (PS–b-PI–b-PS) triblock copolymer was functionalized in toluene solution by free radical mercaptan addition in order to obtain an amphiphilic antibacterial elastomer. Thiol terminated PEG was grafted through the double bonds of PS–b-PI–b-PS via free radical thiol-ene coupling reaction. The antibacterial properties of the amphiphilic graft copolymers were observed. The original and the modified polymers were used to create microfibers in an electro-spinning process. Topology of the electrospun micro/nanofibers were studied by using scanning electron microscopy (SEM). The chemical structures of the amphiphilic comb type graft copolymers were elucidated by the combination of elemental analysis, {sup 1}H NMR, {sup 13}C NMR, GPC and FTIR. - Graphical abstract: Double bonds of polyisoprene units in polystyrene–block-polyisoprene–block-polystyrene triblock copolymer were partially capped with PEG containing mercapto end group via thiol-ene addition in order to obtain antibacterial amphiphilic elastomer. Nano fibers from amphiphilic graft polymers solution were produced by electrospinning. The PEG grafted copolymer inhibits very effectively bacterial growth. Highlights: ► A commercial synthetic elastomer was grafted with PEG to obtain amphiphilic elastomer. ► Amphiphilic elastomer shows antibacterial properties. ► Electrospun micro fibers of the amphiphilic elastomer tend to globular formation.

  19. Effects Of Radiation On Elastomers

    Science.gov (United States)

    Bouquet, Frank L.

    1988-01-01

    Report provides data on effects of radiation on elastomers. Quantifies effects by giving minimum radiation levels to induce changes of 1 percent and 25 percent in given properties. Electrical, mechanical, and chemical properties included in data. Combined effects of heat and radiation briefly considered. Data summarized in graphic form useful to designers.

  20. Elastomer Reinforced with Carbon Nanotubes

    Science.gov (United States)

    Hudson, Jared L.; Krishnamoorti, Ramanan

    2009-01-01

    Elastomers are reinforced with functionalized, single-walled carbon nanotubes (SWNTs) giving them high-breaking strain levels and low densities. Cross-linked elastomers are prepared using amine-terminated, poly(dimethylsiloxane) (PDMS), with an average molecular weight of 5,000 daltons, and a functionalized SWNT. Cross-link densities, estimated on the basis of swelling data in toluene (a dispersing solvent) indicated that the polymer underwent cross-linking at the ends of the chains. This thermally initiated cross-linking was found to occur only in the presence of the aryl alcohol functionalized SWNTs. The cross-link could have been via a hydrogen-bonding mechanism between the amine and the free hydroxyl group, or via attack of the amine on the ester linage to form an amide. Tensile properties examined at room temperature indicate a three-fold increase in the tensile modulus of the elastomer, with rupture and failure of the elastomer occurring at a strain of 6.5.

  1. Optimisation of Silicone-based Dielectric Elastomer Transducers by Means of Block Copolymers - Synthesis and Compounding

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam

    have been studied. Their actuation occurs when Maxwell stress exceeds elastic stress in the presence of an electrical field, resulting in contraction in thickness and planar expansion in the area. As well as an actuator, dielectric elastomers can be used as generators and sensors. As a dielectric...... through the use of a multi-walled carbon nanotube (MWCNT) in a PDMS-PEG matrix as a compliant electrode of dielectric elastomers. The conductive PDMS-PEG copolymer was incorporated with surface-treated MWCNT, in order to obtain highly conductive elastomer. The prepared sample with 4 parts per hundred...... rubber (phr) MWCNT was soft and the resulting conductivity of the cross-linked PDMS-PEG copolymer with the addition of MWCNT was high, at 10-2 S cm-1, nearly equivalent to a commonly used commercial conducting polymer. In this thesis, the elastomer and electrode system is referred to as a ‘dielectric...

  2. Applications of pressure-sensitive dielectric elastomer sensors

    Science.gov (United States)

    Böse, Holger; Ocak, Deniz; Ehrlich, Johannes

    2016-04-01

    Dielectric elastomer sensors for the measurement of compression loads with high sensitivity are described. The basic design of the sensors exhibits two profiled surfaces between which an elastomer film is confined. All components of the sensor were prepared with silicone whose stiffness can be varied in a wide range. Depending on details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression and electrode layers on the elastomer profiles and in the elastomer film approach each other. Different designs of the pressure sensor give rise to very different sensor characteristics in terms of the dependence of electric capacitance on compression force. Due to their inherent flexibility, the pressure sensors can be used on compliant substrates such as seats or beds or on the human body. This gives rise to numerous possible applications. The contribution describes also some examples of possible sensor applications. A glove was equipped with various sensors positioned at the finger tips. When grabbing an object with the glove, the sensors can detect the gripping forces of the individual fingers with high sensitivity. In a demonstrator of the glove equipped with seven sensors, the capacitances representing the gripping forces are recorded on a display. In another application example, a lower limb prosthesis was equipped with a pressure sensor to detect the load on the remaining part of the leg and the load is displayed in terms of the measured capacitance. The benefit of such sensors is to detect an eventual overload in order to prevent possible pressure sores. A third example introduces a seat load sensor system based on four extended pressure sensor mats. The sensor system detects the load distribution of a person on the seat. The examples emphasize the high performance of the new pressure sensor technology.

  3. Growth of single crystals of organic salts with large second-order optical nonlinearities by solution processes for devices

    Science.gov (United States)

    Leslie, Thomas M.

    1995-01-01

    Data obtained from the electric field induced second harmonic generation (EFISH) and Kurtz Powder Methods will be provided to MSFC for further refinement of their method. A theoretical model for predicting the second-order nonlinearities of organic salts is being worked on. Another task is the synthesis of a number of salts with various counterions. Several salts with promising SHG activities and new salts will be tested for the presence of two crystalline forms. The materials will be recrystallized from dry and wet solvents and compared for SHG efficiency. Salts that have a high SHG efficiency and no tendency to form hydrates will be documented. The synthesis of these materials are included in this report. A third task involves method to aid in the growth of large, high quality single crystals by solution processes. These crystals will be characterized for their applicability in the fabrication of devices that will be incorporated into optical computers in future programs. Single crystals of optimum quality may be obtained by crystal growth in low-gravity. The final task is the design of a temperature lowering single crystal growth apparatus for ground based work. At least one prototype will be built.

  4. Novel silicone elastomer formulations for DEAPs

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard; Vudayagiri, Sindhu; Benslimane, Mohamed

    2013-01-01

    We demonstrate that the force output and work density of polydimethylsiloxane (PDMS) based dielectric elastomer transducers can be significantly enhanced by the addition of high permittivity titanium dioxide nanoparticles which was also shown by Stoyanov et al[1] for pre-stretched elastomers...... and by Carpi et al for RTV silicones[2]. Furthermore the elastomer matrix is optimized to give very high breakdown strengths. We obtain an increase in the dielectric permittivity of a factor of approximately 2 with a loading of 12% TiO2 particles compared to the pure modified silicone elastomer with breakdown...

  5. Cross-Linked Liquid Crystalline Systems From Rigid Polymer Networks to Elastomers

    CERN Document Server

    Broer, Dirk

    2011-01-01

    With rapidly expanding interest in liquid crystalline polymers and elastomers among the liquid crystal community, researchers are currently exploring the wide range of possible application areas for these unique materials, including optical elements on displays, tunable lasers, strain gauges, micro-structures, and artificial muscles. Written by respected scientists from academia and industry around the world, who are not only active in the field but also well-known in more traditional areas of research, "Cross-Linked Liquid Crystalline Systems: From Rigid Polymer Networks to Elastomers&qu

  6. Electrical Breakdown and Mechanical Ageing in Dielectric Elastomers

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin

    Dielectric elastomers (DE) are used in various applications, such as artificial eye lids, pressure sensors and human motion energy generators. For many applications, one of the major factors that limits the DE performance is premature electrical breakdown. There are many approaches that have been...... their long-term mechanical reliability as they are susceptible to Mullins effects as the results of pre-stretching. Therefore, two strategies are developed in this thesis in order to produce DEs with high electrical performance and long-term electromechanical reliability. The first strategy is to study...... the mechanisms behind the electrical breakdown of DEs and the second strategy is to investigate the long-term electromechanical reliability of DEs. In the first strategy, the electrothermal breakdown in polydimethylsiloxane (PDMS) elastomers was modelled in order to evaluate the thermal mechanisms behind...

  7. Optimization of large-scale fabrication of dielectric elastomer transducers

    DEFF Research Database (Denmark)

    Hassouneh, Suzan Sager

    as conductive adhesives were rejected. Dielectric properties below the percolation threshold were subsequently investigated, in order to conclude the study. In order to avoid destroying the network structure, carbon nanotubes (CNTs) were used as fillers during the preparation of the conductive elastomers......Dielectric elastomers (DEs) have gained substantial ground in many different applications, such as wave energy harvesting, valves and loudspeakers. For DE technology to be commercially viable, it is necessary that any large-scale production operation is nondestructive, efficient and cheap. Danfoss...... grafted covalently to the CNT surface with poly(methacryloyl polydimethylsiloxane), resulting in the obtained conductivities being comparable to commercially available Elastosil LR3162, even at low functionalisation. The optimized methods allow new processes for the production of DE film with corrugations...

  8. Magnetic ordering in single crystals of PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta

    CERN Document Server

    Uma, S; Gmelin, E; Rangarajan, G; Skanthakumar, S; Lynn, J W; Walter, R; Lorenz, T; Büchner, B; Walker, E; Erb, A

    1998-01-01

    Heat capacity measurements on pure but twinned single crystals of PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta reveal a sharp peak at T sub N sup P sup sub T =16.6 K, which according to thermal expansion, neutron diffraction, and magnetic susceptibility measurements originates from an antiferromagnetic ordering of the Pr-ion moments. A modest coupling to the Cu(2) spin system is observed. Below T sub N sup P sup sub T a first-order transition in the magnetic structure of the Pr spin system (at 13.4 K in warming; approx. 11 K in cooling) is found. Field-dependent heat capacity data show anisotropic temperature dependences of the c sub p -peaks and recover a Schottky-like anomaly due to the crystal-field-split ground state of the Pr sup 3 sup +. (author). Letter-to-the-editor

  9. Generation and propagation of high-order Bessel vortices in linear and non-linear crystals

    CSIR Research Space (South Africa)

    Belyi, VN

    2009-08-01

    Full Text Available of crystals was studied. Particularly, a nonlinear frequency doubling of Bessel vortices in the conditions of new type synchronism (full conical phase-matching) is considered. This scheme of three-wave interactions of BLBs based on that the spatial frequency...

  10. Significance of Al doping for antiferromagnetic AFII ordering in YBa2Cu3-xAlxO6+#delta# materials: A single-crystal neutron-diffraction study

    DEFF Research Database (Denmark)

    Brecht, E.; Schmahl, W.W.; Fuess, H.

    1995-01-01

    the antiferromagnetic ordering pattern is different for the AFI and AFII phase, the ordered moments on the Cu sites are within the experimental error ([S](Cu(2)) approximate to 0.56 mu(B), [S](Cu(1)) approximate to 0 mu(B)) identical in the two phases. Comparison of Al-doped crystals with pure crystals of the same...

  11. Dielectric Elastomer Actuators for Microfluidics

    OpenAIRE

    Maffli, Luc; Rosset, Samuel; Shea, Herbert

    2012-01-01

    One of the goals of microfluidics is to bring a whole laboratory processing chain on a few square centimeters, Lab-On-Chips (LOC). But current LOCs require many heavy and power-consuming off-chip controls like pneumatics, pumps and valves, which keep the small chip bound to the lab. Miniaturized Dielectric Elastomer Actuators (DEA) are excellent candidates to make LOC truly portable, since they combine electrical actuation, large stroke volumes and high output forces. We report on the use of ...

  12. Higher-order mode suppression in rod-type photonic crystal fibers with sectioned doping and enlarged core

    DEFF Research Database (Denmark)

    Poli, F.; Coscelli, E.; Passaro, D.

    2010-01-01

    Yb-doped rod-type photonic crystal fibers are double-cladding large-mode-area fibers with the outer dimension of few millimeters. The higher-order mode suppression through gain filtering has been demonstrated in these fibers, by enlarging the core radius from 30 μm to 40 μm, while keeping fixed...... analyzed with a spatial and spectral amplifier model, showing the positive effect of the gain filtering in improving the fundamental mode amplification, to the detriment of the higher-order mode one. Comparisons have been made with the properties of rod-type fibers with 30 μm core radius, both with uniform...

  13. Dielectric Elastomers for Actuation and Energy Harvesting

    Science.gov (United States)

    Brochu, Paul A.

    The first part of this work focuses on free-standing linear soft silicone actuators as this configuration is the most relevant for real applications. A particular soft silicone has been isolated a good candidate and was extensively tested in a free-standing linear actuator configuration to determine the effects of pre-stretch and the application of mechanical loads on its actuation performance. It is shown that when the mechanical loads are properly applied, large linear actuation strains of 120% and work density of 0.5 J/cm3 can be obtained. Furthermore, we demonstrate that when coupled with single wall carbon nanotube (SWNT) compliant electrodes, fault-tolerance is introduced via self-clearing leading to significantly improved operational reliability. Driven at moderate electric fields, the actuators display relatively high linear actuation strain (25%) without degradation of the electromechanical performance even after 85,000 cycles. The high performance of the aforementioned soft silicone actuators requires the application of rather large levels of prestrain. In order to eliminate this requirement a novel all-silicone prestrain-locked interpenetrating polymer network (S-IPN) elastomer was developed. The elastomer is fabricated using a combination of two silicones: a soft room temperature vulcanizing silicone that serves as the host elastomer matrix, and a more rigid high temperature vulcanizing silicone that acts to preserve the prestrain in the host network. The free-standing prestrain-locked silicones show a more than twofold performance improvement over standard free-standing silicone films, with a linear strain of 25% and an area strain of 45% when tested in a diaphragm configuration. The S-IPN procedure was leveraged to improve electrode adhesion and stability as well as improve the interlayer adhesion in multilayer actuators. It is demonstrated that strongly bonded SWNT electrodes are capable of fault tolerance through self-clearing, even in multilayer

  14. Generation of octave-spanning mid-infrared pulses from cascaded second-order nonlinear processes in a single crystal.

    Science.gov (United States)

    Yin, Yanchun; Ren, Xiaoming; Chew, Andrew; Li, Jie; Wang, Yang; Zhuang, Fengjiang; Wu, Yi; Chang, Zenghu

    2017-09-11

    We report on experimental generation of a 6.8 μJ laser pulse spanning from 1.8 to 4.2 μm from cascaded second-order nonlinear processes in a 0.4-mm BiB3O6 (BIBO) crystal. The nonlinear processes are initiated by intra-pulse difference frequency generation (DFG) using spectrally broadened Ti:Sapphire spectrum, followed by optical parametric amplification (OPA) of the DFG pulse. The highest energy, 12.6 μJ, is achieved in a 0.8-mm BIBO crystal with a spectrum spanning from 1.8 to 3.5 μm. Such cascaded nonlinear processes are enabled by the broadband pump and the coincident phase matching angle of DFG and OPA. The spectrum is initiated from the DFG process and is thus expected to have passive stable carrier-envelope phase, which can be used to seed either a chirped pulse amplifier (CPA) or an optical parametric chirped pulse amplifier (OPCPA) for achieving high-energy few-cycle mid-infrared pulses. Such cascaded second-order nonlinear processes can be found in many other crystals such as KTA, which can extend wavelengths further into mid-infrared. We achieved a 0.8 μJ laser pulse spanning from 2.2 to 5.0 μm in KTA.

  15. The Current State of Silicone-Based Dielectric Elastomer Transducers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    2016-01-01

    Silicone elastomers are promising materials for dielectric elastomer transducers (DETs) due to their superior properties such as high efficiency, reliability and fast response times. DETs consist of thin elastomer films sandwiched between compliant electrodes, and they consti- tute an interesting...... driving voltages. In this review, the current state of sili- cone elastomers for DETs is summarised and critically discussed, including commercial elastomers, composites, polymer blends, grafted elastomers and complex network structures. For future developments in the field it is essential that all aspects...... of the elastomer are taken into account, namely dielectric losses, life- time and the very often ignored polymer network integrity and stability....

  16. Foam injection molding of elastomers with iron microparticles

    Science.gov (United States)

    Volpe, Valentina; D'Auria, Marco; Sorrentino, Luigi; Davino, Daniele; Pantani, Roberto

    2015-12-01

    In this work, a preliminary study of foam injection molding of a thermoplastic elastomer, Engage 8445, and its microcomposite loaded with iron particles was carried out, in order to evaluate the effect of the iron microparticles on the foaming process. In particular, reinforced samples have been prepared by using nanoparticles at 2% by volume. Nitrogen has been used as physical blowing agent. Foamed specimens consisting of neat and filled elastomer were characterized by density measurements and morphological analysis. While neat Engage has shown a well developed cellular morphology far from the injection point, the addition of iron microparticles considerably increased the homogeneity of the cellular morphology. Engage/iron foamed samples exhibited a reduction in density greater than 32%, with a good and homogeneous cellular morphology, both in the transition and in the core zones, starting from small distances from the injection point.

  17. Dynamic performance of dielectric elastomers utilized as acoustic actuators

    Science.gov (United States)

    Hochradel, K.; Rupitsch, S. J.; Sutor, A.; Lerch, R.; Vu, D. K.; Steinmann, P.

    2012-06-01

    We report on the frequency dependent behavior of dielectric elastomer actuators (DEA). The introduced smart material actuators consist of 3M™'s elastomer VHB™4905 (9469) and a compliant, sputtered copper electrode on each side. The presented experiments on these compounds contain the active tuning of their resonance frequency and their application as acoustic actuators. We are able to decrease the membranes' eigenfrequency by 30% with an electrical offset potential. Alternatively, if an alternating signal is applied, sound pressure levels up to 130 dB in an enclosed volume of 28 ccm are achieved. In order to verify the results, a numerical simulation is introduced incorporating the two physical fields involved: electrical and mechanical.

  18. Bond orientational order in the blue phases of chiral liquid crystals

    OpenAIRE

    Longa, Lech; Trebin, Hans-Rainer

    1993-01-01

    It is proposed to describe blue phases by two order parameters: the standard alignment tensor field Q αβ(r) and a bond orientational tensor order parameter of octahedral point group symmetry scrO(432). The yet mysterious blue fog then emerges as a liquid of purely cubic bond orientational order. In the transition from the cubic blue phases to the blue fog the cubic space group symmetry is being reduced to its octahedral factor group. Because of the new order parameter the scrO 5(scr...

  19. Crystal Structure and Magnetic Anisotropy in the Magnetic Ordered Phases of PrB6

    Science.gov (United States)

    Sera, Masafumi; Kim, Moo-Sung; Tou, Hideki; Kunii, Satoru

    2004-12-01

    We have studied the magnetization and the thermal expansion of PrB6 in both C and IC phases. In the IC phase, the crystal is found to be nearly cubic. This is because the magnitude of av is different from site to site in the IC phase. In the C phase, the crystal is easily deformed into the diamond shaped one by a small external field such as a magnetic field or a uniaxial stress along the two-fold axis. This indicates the small AFQ interaction in PrB6. The magnetization exhibits the anisotropy, M>M>M in the IC phase and M>M>M in the C phase. The former is explained by a difference of the domain distribution for three field directions, i.e., the larger the population of the χ\\bot configuration, the larger the magnitude of M. In the C phase, the planer type Kxy domain state and the χ\\bot configuration are realized for three magnetic field directions. For H\\parallel and , the 1-k collinear magnetic structure is realized and the moment is rotated in the xy plane, while for H\\parallel, the moment is canted towards z axis from the xy plane. Altough in both cases, χ\\bot is associated with the Zeeman energy gain, χ\\bot in the former is smaller than that in the latter. This difference makes the anisotropy of M in the C phase as M>M>M.

  20. Controlled synthesis of SBR elastomers

    Science.gov (United States)

    Zhou, Jin-Ping

    The first objective of this research was to prepare styrene-butadiene copolymers (SBRs) with low vinyl and non blocky styrene contents for hysteresis reduction. The effect of added alkali metal alkoxides on the alkyllithium initiated copolymerization of butadiene and styrene was investigated. It was found that the amount of block styrene passes through a minimum as the molar ratio of alkali metal alkoxide (Na+ or K+) to lithium varies from 0 to 0.5. The optimal amount of alkoxides varied with the alkali metal (Na+ vs. K+) and depended on the level of lithium alkoxide present. The best system found for this purpose was sodium 2,3-dimethyl-3-pentoxide under inert atmosphere conditions; the optimal amount of 0.2. However, optimization for polymerization under high vacuum conditions required a shift of [NaODP]/[RLi] to the range of about 0.05 to 0.1. Pre-addition of lithium 2,3-dimethyl 3-pentoxide under high vacuum conditions shifted the optimal amount of NaODP to a higher level, which indicated that differences for the two systems were caused by different levels of the impurities presented. Further investigation of other styrene-diene copolymerizations verified that the amount of added sodium alkoxide needed to be optimized in order to produce copolymers with the least blocky styrene. Determination of the monomer reactivity ratios of styrene and butadiene for NaDDP revealed that the amount of block styrene was not minimized by "random" copolymerization, but by systems with a tendency toward alternation. Computer simulation revealed that the highest percentage of isolated styrene unit (the least block styrene contents) not only required a very low value of the styrene monomer reactivity ratio to eliminate the short block styrene sequences but also a compatible value of the butadiene monomer reactivity ratio in order not to produce a long terminal styrene block. Glass transition temperatures (Tg) showed dependency not only on total styrene and vinyl contents, but also

  1. Propagation of high-order circularly polarized Bessel beams and vortex generation in uniaxial crystals

    CSIR Research Space (South Africa)

    Belyi, VN

    2011-05-01

    Full Text Available and TH waves at the entrance face of the crystal (z = 0) are of the following form: �Eo = i? 2 {Jm?1(qr )�e+ exp [i(m ? 1)?] + �e ? Jm+1(qr ) exp [i(m + 1)?]}, (1) �Ee = inez? 2no {Jm?1(qr )�e+ exp [i(m ? 1)?] ? �e ? Jm+1(qr ) exp [i(m + 1...)?]}, (2) �Bo = noz? 2 {Jm?1(qr )�e+ exp [i(m ? 1)?] ? �e ? Jm+1(qr ) exp [i(m + 1)?]}, (3) �Be = no? 2 {Jm?1(qr )�e+ exp [i(m ? 1)?] + �e ? Jm+1(qr ) exp [i(m + 1)?]}, (4) where q = k0nr is the conicity parameter or radial wave number...

  2. Geometric triangular chiral hexagon crystal-like complexes organization in pathological tissues biological collision order.

    Directory of Open Access Journals (Sweden)

    Jairo A Díaz

    Full Text Available The present study describes and documents self-assembly of geometric triangular chiral hexagon crystal like complex organizations (GTCHC in human pathological tissues. The authors have found this architectural geometric expression at macroscopic and microscopic levels mainly in cancer processes. This study is based essentially on macroscopic and histopathologic analyses of 3000 surgical specimens: 2600 inflammatory lesions and 400 malignant tumours. Geometric complexes identified photographically at macroscopic level were located in the gross surgical specimen, and these areas were carefully dissected. Samples were taken to carry out histologic analysis. Based on the hypothesis of a collision genesis mechanism and because it is difficult to carry out an appropriate methodological observation in biological systems, the authors designed a model base on other dynamic systems to obtain indirect information in which a strong white flash wave light discharge, generated by an electronic device, hits over the lines of electrical conductance structured in helicoidal pattern. In their experimental model, the authors were able to reproduce and to predict polarity, chirality, helicoid geometry, triangular and hexagonal clusters through electromagnetic sequential collisions. They determined that similar events among constituents of extracelular matrix which drive and produce piezoelectric activity are responsible for the genesis of GTCHC complexes in pathological tissues. This research suggests that molecular crystals represented by triangular chiral hexagons derived from a collision-attraction event against collagen type I fibrils emerge at microscopic and macroscopic scales presenting a lateral assembly of each side of hypertrophy helicoid fibers, that represent energy flow in cooperative hierarchically chiral electromagnetic interaction in pathological tissues and arises as a geometry of the equilibrium in perturbed biological systems. Further

  3. Measurements of residual strains in ceramic-elastomer composites with diffuse scattering of polarized neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Zajac, Wojciech [H. Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Krakow (Poland)], E-mail: Wojciech.Zajac@ifj.edu.pl; Boczkowska, Anna; Babski, Kamil; Kurzydlowski, Krzysztof J. [Warsaw University of Technology, Faculty of Materials Science and Engineering, Woloska 141, 02-507 Warsaw (Poland); Deen, Pascale P. [Institute Laue-Langevin, 6 rue Jules Horowitz, 38000 Grenoble (France)

    2008-12-15

    An experiment of diffuse scattering (also referred to as wide-angle neutron scattering) of polarized neutrons with polarization analysis was performed in order to detect residual strains in ceramic-elastomer composites of porous SiO{sub 2} and poly(urea-urethane) elastomers. Two ceramics, with pore sizes of 20 and 70 {mu}m, and two elastomers, with hard/soft segments molar ratios of H/S = 0.25 and 1.5, were selected for composite fabrication. The use of polarization analysis made it possible to detect and study very weak coherent scattering peaks from the elastomer synthesized inside SiO{sub 2} ceramics. Residual strains were detected and measured based on interatomic distances in the SiO{sub 2}+ H/S = 1.5 composite but not in the SiO{sub 2}+ H/S = 0.25. The reason is sought in soft domains being ordered in the H/S = 0.25 elastomer as opposed to the H/S = 1.5 one.

  4. Double epitaxy as a paradigm for templated growth of highly ordered three-dimensional mesophase crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Yongsoon; Tao, Jinhui; Arey, Bruce W.; Wang, Chongmin; Exarhos, Gregory J.; De Yoreo, James J.; Sushko, Maria L.; Liu, Jun

    2016-08-30

    Molecular templating and self-assembly are fundamental mechanisms for controlling the morphology of biominerals, while in synthetic two-dimensional layered materials similar levels of control over materials structure can be achieved through the epitaxial relationship with the substrate. In this study these two concepts are combined to provide an approach for the nucleation and growth of three-dimensional ordered mesophases on solid surfaces. A combined experimental and theoretical study revealed how atomic ordering of the substrate controls the structure of surfactant template and the orientation and morphology of the epitaxially grown inorganic material. Such dual epitaxial relationship between the substrate, surfactant template and inorganic mesophase gives rise to a highly ordered porous mesophase with a well-defined cubic lattice of pores. The level of control over material’s three-dimensional architecture achieved in this one-step synthesis is reminiscent to that in biomineralization.

  5. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Mateiu, Ramona Valentina; Skov, Anne Ladegaard

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we focus on the chloro propyl functionalized silicone elastomers prepared in Madsen et al[2] and we investigate the electrical...... breakdown patterns of two similar chloro propyl functionalized silicone elastomers which break down electrically in a rather different way as well as we compare them to a silicone based reference. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) are used to evaluate...... the elastomers after electrical breakdown....

  6. Modeling of a Dielectric Elastomer Bender Actuator

    Directory of Open Access Journals (Sweden)

    Paul White

    2014-07-01

    Full Text Available The current smallest self-contained modular robot uses a shape memory alloy, which is inherently inefficient, slow and difficult to control. We present the design, fabrication and demonstration of a module based on dielectric elastomer actuation. The module uses a pair of bowtie dielectric elastomer actuators in an agonist-antagonist configuration and is seven times smaller than previously demonstrated. In addition, we present an intuitive model for the bowtie configuration that predicts the performance with experimental verification. Based on this model and the experimental analysis, we address the theoretical limitations and advantages of this antagonistic bender design relative to other dielectric elastomer actuators.

  7. Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures.

    Science.gov (United States)

    Biedermannová, Lada; Schneider, Bohdan

    2015-11-01

    Crystallography provides unique information about the arrangement of water molecules near protein surfaces. Using a nonredundant set of 2818 protein crystal structures with a resolution of better than 1.8 Å, the extent and structure of the hydration shell of all 20 standard amino-acid residues were analyzed as function of the residue conformation, secondary structure and solvent accessibility. The results show how hydration depends on the amino-acid conformation and the environment in which it occurs. After conformational clustering of individual residues, the density distribution of water molecules was compiled and the preferred hydration sites were determined as maxima in the pseudo-electron-density representation of water distributions. Many hydration sites interact with both main-chain and side-chain amino-acid atoms, and several occurrences of hydration sites with less canonical contacts, such as carbon-donor hydrogen bonds, OH-π interactions and off-plane interactions with aromatic heteroatoms, are also reported. Information about the location and relative importance of the empirically determined preferred hydration sites in proteins has applications in improving the current methods of hydration-site prediction in molecular replacement, ab initio protein structure prediction and the set-up of molecular-dynamics simulations.

  8. Structure of the ordered hydration of amino acids in proteins: analysis of crystal structures

    Science.gov (United States)

    Biedermannová, Lada; Schneider, Bohdan

    2015-01-01

    Crystallography provides unique information about the arrangement of water molecules near protein surfaces. Using a nonredundant set of 2818 protein crystal structures with a resolution of better than 1.8 Å, the extent and structure of the hydration shell of all 20 standard amino-acid residues were analyzed as function of the residue conformation, secondary structure and solvent accessibility. The results show how hydration depends on the amino-acid conformation and the environment in which it occurs. After conformational clustering of individual residues, the density distribution of water molecules was compiled and the preferred hydration sites were determined as maxima in the pseudo-electron-density representation of water distributions. Many hydration sites interact with both main-chain and side-chain amino-acid atoms, and several occurrences of hydration sites with less canonical contacts, such as carbon–donor hydrogen bonds, OH–π interactions and off-plane interactions with aromatic heteroatoms, are also reported. Information about the location and relative importance of the empirically determined preferred hydration sites in proteins has applications in improving the current methods of hydration-site prediction in molecular replacement, ab initio protein structure prediction and the set-up of molecular-dynamics simulations. PMID:26527137

  9. Enhanced Femtosecond Optical Pulses Compression Induced by Negative Third-Order Dispersion in Solid-Core Photonic Crystal Fibers

    Directory of Open Access Journals (Sweden)

    Ashkan Ghanbari

    2014-05-01

    Full Text Available In this paper, the chirped- free optical pulses compression through propagating in silica - index guiding photonic crystal fibers will be studied. The results show that the Raman Effect can enhances the quality of compressed pulses and also the positive third-order dispersion (TOD can be considered as the main reason in limiting the optical pulses compression. We will show that, the combined effects of the Raman scattering and negative TODs can causes generating much further compressed pulses in comparison with applying the only Raman effect or combination of that with the positive TODs. In this paper, We also numerically present a novel technique to solve the wave propagation equation, which is known as the concrete algorithms of split-step fourier method and fourth order Runge-Kutta (RK4 method. This method has a higher accuracy, although the computational time is longer because the number of calculation steps is chosen very large.

  10. Anharmonic correlated Debye model high-order expanded interatomic effective potential and Debye-Waller factors of bcc crystals

    Energy Technology Data Exchange (ETDEWEB)

    Van Hung, Nguyen, E-mail: hungnv@vnu.edu.vn [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Hue, Trinh Thi [Department of Physics, Hanoi University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi (Viet Nam); Khoa, Ha Dang [School of Engineering Physics, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi (Viet Nam); Vuong, Dinh Quoc [Quang Ninh Education & Training Department, Nguyen Van Cu, Ha Long, Quang Ninh (Viet Nam)

    2016-12-15

    High-order expanded interatomic effective potential and Debye-Waller factors (DWFs) for local vibrational amplitudes in X-ray absorption fine structure (XAFS) of bcc crystals have been studied based on the anharmonic correlated Debye model. DWFs are presented in terms of cumulant expansion up to the fourth order and the many-body effects are taken into account in the present one-dimensional model based on the first shell near neighbor contribution approach used in the derivations of the anharmonic effective potential and XAFS cumulants where Morse potential is assumed to describe the single-pair atomic interaction. Analytical expressions for the dispersion relation, correlated Debye frequency and temperature and four first temperature-dependent XAFS cumulants have been derived based on the many-body perturbation approach. Thermodynamic properties and anharmonic effects in XAFS of bcc crystals described by the obtained cumulants have been in detail discussed. The advantage and efficiency of the present theory are illustrated by good agreement of the numerical results for Mo, Fe and W with experiment.

  11. Development of Polar Order by Liquid-Crystal Self-Assembly of Weakly Bent Molecules.

    Science.gov (United States)

    Alaasar, Mohamed; Prehm, Marko; Poppe, Silvio; Tschierske, Carsten

    2017-04-24

    Organic ferroelectrics are of growing importance for multifunctional materials. Here we provide an understanding of the distinct stages of the development of sterically induced polar order in liquid-crystalline (LC) soft matter. Three series of weakly bent molecules derived from 4-cyanoresorcinol as the bent core unit with laterally fluorinated azobenzene wings have been synthesized, and the effects of the position of fluorine substitution, alkyl-chain length, and temperature on the LC self-assembly and polar order were studied. In the LC phases a paraelectric-ferroelectric transition took place as the size of the polar domains gradually increased, thereby crossing a permittivity maximum, similar to inorganic solid-state ferroelectrics. An increase in polar coherence length simultaneously led to a transition from synpolar to antipolar domain correlation in the high-permittivity paraelectric range. Associated with the emergence of polar order was the development of a tilted organization of the molecules and a growing coherence of tilt. This led to a transition from non-tilted via tilt-randomized uniaxial to long-range-tilted biaxial smectic phases, and to surface-stabilized symmetry breaking with the formation of chiral conglomerates and field-induced tilt. Moreover, there is a remarkably strong effect of the position of fluorination; polar order is favored by peripheral core substitution and is suppressed by inside-directed fluorination. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Effect of dislocations on the structural order parameter in a crystal upon torsional strain

    Science.gov (United States)

    Zavorotnev, Yu. D.; Zakharov, A. Yu.; Metlov, L. S.

    2017-11-01

    The interaction of the structural subsystem with dislocations upon applying an elastic torsional strain has been studied. The consideration is performed in the terms of the Landau phenomenological theory with the refusal from the approximation that the irreducible vector magnitudes are constant. It is shown that additional spatial amplitude and frequency oscillations related to the change in the magnitudes of the structural order parameter and the dislocation density appear.

  13. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Mateiu, Ramona Valentina; Skov, Anne Ladegaard

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we focus on the chloro propyl functionalized silicone elastomers prepared in Madsen et al[2] and we investigate the electrical...... breakdown patterns of two similar chloro propyl functionalized silicone elastomers which break down electrically in a rather different way as well as we compare them to a silicone based reference. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) are used to evaluate the elastomers...... before and after electrical breakdown. It was shown the chemically very similar silicone elastomers broke down electrically in very different ways. These observations emphasize that the modification of the silicone backbone may open up for completely new possibilities for stabilizing the silicone...

  14. Space-Qualifiable Cyanate Ester Elastomer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In Phase 1, CRG demonstrated the feasibility of a novel approach to prepare cyanate ester based elastomers. This approach polymerizes in-situ siloxane within a...

  15. Space-Qualifiable Cyanate Ester Elastomer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Cornerstone Research Group, Inc. (CRG) proposes to design and develop a space-qualifiable cyanate ester elastomer for application in self-deployable space structures...

  16. High-strain actuator materials based on dielectric elastomers

    DEFF Research Database (Denmark)

    Pelrine, R.; Kornbluh, R.; Kofod, G.

    2000-01-01

    Dielectric elastomers are a new class of actuator materials that exhibit excellent performance. The principle of operation, as well as methods to fabricate and test these elastomers, is summarized here. The Figure is a sketch of an elastomer film (light gray) stretched on a frame (black) and patt......Dielectric elastomers are a new class of actuator materials that exhibit excellent performance. The principle of operation, as well as methods to fabricate and test these elastomers, is summarized here. The Figure is a sketch of an elastomer film (light gray) stretched on a frame (black...

  17. Nanoparticle-Liquid Crystalline Elastomer Composites

    Directory of Open Access Journals (Sweden)

    Yan Ji

    2012-01-01

    Full Text Available Liquid crystalline elastomers (LCEs exhibit a number of remarkable physical effects, including a uniquely high-stroke reversible mechanical actuation triggered by external stimuli. Fundamentally, all such stimuli affect the degree of liquid crystalline order in the polymer chains cross-linked into an elastic network. Heat and the resulting thermal actuation act by promoting entropic disorder, as does the addition of solvents. Photo-isomerization is another mechanism of actuation, reducing the orientational order by diminishing the fraction of active rod-like mesogenic units, mostly studied for azobenzene derivatives incorporated into the LCE composition. Embedding nanoparticles provides a new, promising strategy to add functionality to LCEs and ultimately enhance their performance as sensors and actuators. The motivation for the combination of nanoparticles with LCEs is to provide better-controlled actuation stimuli, such as electric and magnetic fields, and broad-spectrum light, by selecting and configuring the appropriate nanoparticles in the LCE matrix. Here we give an overview of recent advances in this area with a focus on preparation, physical properties and actuation performance of the resultant nanocomposites.

  18. Electrical resistivity mechanism in magnetorheological elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Kchit, N; Bossis, G [LPMC UMR-CNRS 6622, University of Nice Sophia Antipolis, 06108 Nice cedex 2 (France)], E-mail: bossis@unice.fr

    2009-05-21

    Magnetorheological elastomers (MREs) are smart materials made by aligning magnetic microparticles inside a liquid polymer. Once the polymer is cured, this anisotropic structure is kept, giving to the composite new properties such as a large change in electrical resistivity with applied pressure. In order to understand the conduction mechanism in such composites, the influence of pressure on the electrical resistivity of metal powders without polymer was first investigated. It was found that the initial resistivity of metal powder at zero pressure is about 10{sup 8} {omega} cm for pure nickel powder and 10{sup 6} {omega} cm for silver coated nickel particles. The piezoresistivity of the powders follows a power law with a coefficient close to (-1) at high compression, which allows the thickness of the oxide layer to be determined. The change in resistance with pressure was found to be an order of magnitude larger for a MRE composite than for the same volume fraction of fillers dispersed randomly in the polymer. The filler particles have a high surface roughness, and when particles are brought into contact under pressure, the electric current takes place via microcontacts between asperities. The model of tunnel resistance developed in this study includes the roughness parameters and the thickness of the oxide layer found with the powder and introduces the thickness of the polymer layer as a new parameter. This model well reproduces experimental curves for piezoresistivity of composites allowing the thickness of the insulating polymer layer strongly adsorbed on the surface of particles to be determined.

  19. Dielectric elastomer pump for artificial organisms

    Science.gov (United States)

    Bowers, Amy E.; Rossiter, Jonathan M.; Walters, Peter J.; Ieropoulos, Ioannis A.

    2011-04-01

    This paper presents a bio-inspired, dielectric elastomer (DE) based tubular pumping unit, developed for eventual use as a component of an artificial digestive tract onboard a microbial fuel cell powered robot (EcoBot). The pump effects fluid displacement by direct actuation of the tube wall as opposed to excitation by an external body. The actuator consists of a DE tube moulded from silicone, held in a negative pressure chamber, which is used for prestraining the tube. The pump is coupled with custom designed polymeric check valves in order to rectify the fluid flow and assess the performance of the unit. The valves exhibited the necessary low opening pressures required for use with the actuator. The tube's actuation characteristics were measured both with and without liquid in the system. Based on these data the optimal operating conditions for the pump are discussed. The pump and valve system has achieved flowrates in excess of 40μl/s. This radially contracting/expanding actuator element is the fundamental component of a peristaltic pump. This 'soft pump' concept is suitable for biomimetic robotic systems, or for the medical or food industries where hard contact with the delivered substrate may be undesirable. Future work will look at connecting multiple tubes in series in order to achieve peristalsis.

  20. Finite element analysis and validation of dielectric elastomer actuators used for active origami

    Science.gov (United States)

    McGough, Kevin; Ahmed, Saad; Frecker, Mary; Ounaies, Zoubeida

    2014-09-01

    The field of active origami explores the incorporation of active materials into origami-inspired structures in order to serve as a means of actuation. Active origami-inspired structures capable of folding into complex three-dimensional (3D) shapes have the potential to be lightweight and versatile compared to traditional methods of actuation. This paper details the finite element analysis and experimental validation of unimorph actuators. Actuators are fabricated by adhering layers of electroded dielectric elastomer (3M VHB F9473PC) onto a passive substrate layer (3M Magic Scotch Tape). Finite element analysis of the actuators simulates the electromechanical coupling of the dielectric elastomer under an applied voltage by applying pressures to the surfaces of the dielectric elastomer where the compliant electrode (conductive carbon grease) is present. 3D finite element analysis of the bending actuators shows that applying contact boundary conditions to the electroded region of the active and passive layers provides better agreement to experimental data compared to modeling the entire actuator as continuous. To improve the applicability of dielectric elastomer-based actuators for active origami-inspired structures, folding actuators are developed by taking advantage of localized deformation caused by a passive layer with non-uniform thickness. Two-dimensional analysis of the folding actuators shows that agreement to experimental data diminishes as localized deformation increases. Limitations of using pressures to approximate the electromechanical coupling of the dielectric elastomer under an applied electric field and additional modeling considerations are also discussed.

  1. Operation tools with dielectric elastomer pressure sensors

    Science.gov (United States)

    Böse, Holger; Müller, Dominik; Ehrlich, Johannes

    2017-04-01

    New sensors based on dielectric elastomers have recently been shown to exhibit high sensitivity for compression loads. The basic design of these sensors exhibits two profiled surfaces coated with electrode layers between which an elastomer film with the counter-electrode is confined. All components of the sensor are prepared with silicone whose stiffness can be varied in a wide range. Depending on the details of the sensor design, various effects contribute to the enhancement of the capacitance. The intermediate elastomer film is stretched upon compression, the elastomer profiles are deformed and the electrode layers on the elastomer profiles and in the elastomer film approach each other. Beside the detection of pressure, such sensors can also be used for operation tools in human-machine interfaces. To demonstrate this potential, a touch pad with six pressure-sensitive fields is presented. The corresponding sensors integrated in the touch fields detect the exerted forces of the finger, show them on a display and control the brightness of some LEDs. As a second example, the integration of sensor-based control fields on an automotive steering wheel is shown. Finally, the sensors can also be used in fabrics to control arbitrary functions of wearable electronic devices.

  2. Lyotropic liquid crystal engineering moving beyond binary compositional space - ordered nanostructured amphiphile self-assembly materials by design.

    Science.gov (United States)

    van 't Hag, Leonie; Gras, Sally L; Conn, Charlotte E; Drummond, Calum J

    2017-05-22

    Ordered amphiphile self-assembly materials with a tunable three-dimensional (3D) nanostructure are of fundamental interest, and crucial for progressing several biological and biomedical applications, including in meso membrane protein crystallization, as drug and medical contrast agent delivery vehicles, and as biosensors and biofuel cells. In binary systems consisting of an amphiphile and a solvent, the ability to tune the 3D cubic phase nanostructure, lipid bilayer properties and the lipid mesophase is limited. A move beyond the binary compositional space is therefore required for efficient engineering of the required material properties. In this critical review, the phase transitions upon encapsulation of more than 130 amphiphilic and soluble additives into the bicontinuous lipidic cubic phase under excess hydration are summarized. The data are interpreted using geometric considerations, interfacial curvature, electrostatic interactions, partition coefficients and miscibility of the alkyl chains. The obtained lyotropic liquid crystal engineering design rules can be used to enhance the formulation of self-assembly materials and provides a large library of these materials for use in biomedical applications (242 references).

  3. Fracture of elastomers by cavitation

    KAUST Repository

    Hamdi, Adel

    2014-01-01

    Cavitation phenomenon is studied in rubber-like materials by combining experimental, theoretical and numerical approaches. Specific tests are carried out on a Styrene Butadiene Rubber to point out main characteristics of cavitation phenomenon. Hydrostatic depression is numerically modelled using finite element method. Numerical results are compared to Ball\\'s and Hou & Abeyaratne\\'s models with regard to cavity nucleation in the material. Both models well fit experimental observations suggesting that the cavitation nucleation in elastomers depends on the confinement degree of the specimen. Finally, critical hydrostatic pressure and critical global deformation are proved to govern cavitation nucleation in the studied material. Critical loadings are identified by comparing experimental and numerical load-displacement curves. © 2013 Elsevier Ltd.

  4. The order-disorder potential of the crystal structure of monohydrocalcite, CaCO3·H2O

    Science.gov (United States)

    Makovicky, Emil

    2017-06-01

    Monohydrocalcite, CaCO3·H2O, forms a P31 structure composed of composite rods in which a spiral arrangement of Ca ions is accompanied by spiral arrangements of CO3 groups and of H2O molecules. The atom arrangement on the surface of the rods has rod symmetry P3121 whereas in the rod interior the atoms and atom groups have symmetry P31, which allows for two opposite orientations of a composite rod in respect to the [00.1] direction, connected with minimal change in the inter-rod bonding scheme. The ordered crystal structure contains both rod orientations in a complicated periodic arrangement but various degrees of disorder should occur, generating only small energy penalty.

  5. Reduction of the Adhesive Friction of Elastomers through Laser Texturing of Injection Molds

    Directory of Open Access Journals (Sweden)

    Joel Voyer

    2017-11-01

    Full Text Available It is well known that elastomers usually possess poor dry sliding friction properties due to their highly adhesive character. In order to overcome this problematic behavior in industrial applications, interfacial materials such as oils, greases, coatings, or lacks are normally used in order to separate or to functionalize the contact surfaces of elastomers. Alternatively, the high adhesion tendency of elastomers may be explicitly reduced by modifying the elastomer composition itself or by enabling a reduction of its effective contact area through, for example, surface laser texturing. This second approach, i.e., the reduction of the adhesive character of elastomers through laser structuring, will be the main topic of the present study. For this purpose, different micro-sized grooved structures were produced on flat injection molds using an ultra-short pulsed laser. The micro-structured molds were then used to produce injection molded micro-ridged Liquid Silicone Rubber (LSR sample pads. The investigations consisted firstly of determining the degree of replication of the mold micro-structures onto the surface of the LSR pads and secondly, to ascertain the degree of reduction of the friction force (or coefficient of friction of these micro-ridged LSR pads in comparison to the benchmark (unstructured LSR pads when tested under dry conditions against Aluminum alloy (Al-6082 or PA6.6-GF30 plates. For this second part of the investigation, the normal force (or contact pressure dependency of the coefficient of friction was determined through stepwise load increasing friction tests. The results of these investigations have shown that the production of micro-ridged surfaces on LSR pads through laser structuring of the injection molds could be successfully achieved and that it enables a significant reduction of the friction force for low normal forces (or contact pressures, where the component of adhesion friction is playing an important and determining

  6. Continuum vibration analysis of dielectric elastomer membranes

    Science.gov (United States)

    Nalbach, S.; Rizzello, G.; Seelecke, S.

    2017-04-01

    Dielectric Elastomer (DE) transducers are well known for the possibility of responding to an applied voltage with relatively large actuation strains, often larger than 100%, and for their relatively high actuation bandwidth (order of several kHz). However, up to date there are relatively few applications which use the dynamic behavior of DEs. Some relevant examples include loudspeakers and fluid dispensers. Motivated by the potentialities of DEs in high-frequency applications, the aim of this work is the investigation of the continuous vibrations observed when DE membranes are actuated electrically. The system under analysis consists of a circular DE membrane pre-loaded with a spring. While exciting the DE membrane actuator with high-voltage, high-frequency signals, the motion of the membrane is detected with a 3D laser vibrometer which uses Doppler effect to reconstruct the system spectrum and vibration modes. An extensive experimental investigation is performed to study the influence of system parameters, such as membrane geometry and pre-stress, on the membrane frequency spectrum and vibrational modes.

  7. Constitutive modelling of elastomer/graphene platelet nanocomposites

    Science.gov (United States)

    Abdelsalam, Amir A.; Araby, Sherif; Hassan, M. A.; El-Moneim, A. A.

    2017-09-01

    Elastomers are used in a wide variety of structural and engineering applications. They exhibit a nonlinear elastic stress-strain behaviour known as hyperelasticity which is generally described by hyperelastic strain energy functions. The question raised in the current study was; which model can accurately describe and predict the actual behaviour of the elastomer nanocomposites. The tensile data were used to fit the various elastomeric material models available in MSC.MARC finite element analysis package. The relative percentage error was calculated to determine the goodness of fit in order to select the best model. Numerical results showed that the third order deformation model was the best among the various material models since giving a maximum relative error of fit was 2.7% at small and large strains. To verify the effectiveness of third order deformation model, FE simulations for tensile test was carried out. The results showed that the third order model is sufficiently enough to regenerate the experimental data for uniaxial test and efficiently capture the hyperelastic behavior as good as the experiments.

  8. Plasma polymerization surface modification of Carbon black and its effect in elastomers

    NARCIS (Netherlands)

    Mathew, T.; Datta, Rabin; Dierkes, Wilma K.; Talma, Auke; Ooij, W.J.; Noordermeer, Jacobus W.M.

    2011-01-01

    Surface modification of carbon black by plasma polymerization was aimed to reduce its surface energy in order to compatibilize the filler with various elastomers. A fullerenic carbon black was used for the modification process. Thermogravimetric analysis, wetting behavior with liquids of known

  9. Preparation and electro-response of chitosan-g-poly (acrylic acid) hydrogel elastomers with interpenetrating network

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jianli [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi' an, 710062 (China); School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, 710062 (China); Gao, Ling-xiang, E-mail: gaolx@snnu.edu.cn [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi' an, 710062 (China); School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, 710062 (China); Han, Xuewu; Chen, Tao; Luo, Jue; Liu, Kaiqiang; Gao, Ziwei; Zhang, Weiqiang [Key Laboratory of Applied Surface and Colloid Chemistry (Shaanxi Normal University), Ministry of Education, Xi' an, 710062 (China); School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi' an, 710062 (China)

    2016-02-01

    In this article, novel chitosan-g-poly (acrylic acid) hydrogel elastomers were successfully sythesised by grafting chitosan (CTS) onto poly acrylic acid (PAA) through radical polymerization in the presence/absence of direct current electric field. Their structure and electro-response were evaluated through scanning electron microscopy (SEM), infrared spectroscopy (IR), and dynamic mechanical analyser (DMA), respectively. Stress-strain test showed that the toughness of the chitosan-g-PAA elastomer is higher than the PAA gel. The result demonstrates the elastomers obtained in the presence/absence of electric field with similar chemical composition possess different microstructure. The positive electro responsive effect appeared on the elastomers, and both of storage modulus increment and increment sensitivity yielded maximum value at the AA concentration of 14.09 wt% under the applied electric field of 1.5 kV/mm. Thermo gravimetry and differential scanning calorimetry (TG-DSC) showed the elastomers cured under an applied electric field have stronger intramolecular bonding and higher cross-linking density. - Highlights: • The chitosan-g-poly (acrylic acid) hydrogel elastomers have been prepared. • They have ordered structure and positive electro-response under an electric field. • The maximum electro-response occurs near or at the AA wt% of 14.09 under 1.5 kV/mm.

  10. Role of catalysis in sustainable production of synthetic elastomers

    Indian Academy of Sciences (India)

    Elastomer business plays a significant role in the transportation industry. In fact, elastomers make the world move. ... productions, the impact of synthetic elastomer business cannot be overlooked. The need of synthetic elas- ...... Major global producers of 1,4-cis-polybutadiene rubber. Manufacturer. Country. JSR. Japan.

  11. Thermoplastic elastomers containing 2D nanofillers: montmorillonite, graphene nanoplatelets and oxidized graphene platelets

    Directory of Open Access Journals (Sweden)

    Paszkiewicz Sandra

    2015-12-01

    Full Text Available This paper presents a comparative study on which type of platelets nanofiller, organic or inorganic, will affect the properties of thermoplastic elastomer matrix in the stronger manner. Therefore, poly(trimethylene terephthalate-block-poly(tetramethylene oxide copolymer (PTT-PTMO based nanocomposites with 0.5 wt.% of clay (MMT, graphene nanoplatelets (GNP and graphene oxide (GO have been prepared by in situ polymerization. The structure of the nanocomposites was characterized by transmission electron microscopy (TEM in order to present good dispersion without large aggregates. It was indicated that PTT-PTMO/GNP composite shows the highest crystallization temperature. Unlike the addition of GNP and GO, the introduction of MMT does not have great effect on the glass transition temperature of PTMO-rich soft phase. An addition of all three types of nanoplatelets in the nanocomposites caused the enhancement in tensile modulus and yield stress. Additionally, the cyclic tensile tests showed that prepared nanocomposites have values of permanent set slightly higher than neat PTT-PTMO.

  12. A modelling approach for the heterogeneous oxidation of elastomers

    Science.gov (United States)

    Herzig, A.; Sekerakova, L.; Johlitz, M.; Lion, A.

    2017-09-01

    The influence of oxygen on elastomers, known as oxidation, is one of the most important ageing processes and becomes more and more important for nowadays applications. The interaction with thermal effects as well as antioxidants makes oxidation of polymers a complex process. Based on the polymer chosen and environmental conditions, the ageing processes may behave completely different. In a lot of cases the influence of oxygen is limited to the surface layer of the samples, commonly referred to as diffusion-limited oxidation. For the lifetime prediction of elastomer components, it is essential to have detailed knowledge about the absorption and diffusion behaviour of oxygen molecules during thermo-oxidative ageing and how they react with the elastomer. Experimental investigations on industrially used elastomeric materials are executed in order to develop and fit models, which shall be capable of predicting the permeation and consumption of oxygen as well as changes in the mechanical properties. The latter are of prime importance for technical applications of rubber components. Oxidation does not occur homogeneously over the entire elastomeric component. Hence, material models which include ageing effects have to be amplified in order to consider heterogeneous ageing, which highly depends on the ageing temperature. The influence of elevated temperatures upon accelerated ageing has to be critically analysed, and influences on the permeation and diffusion coefficient have to be taken into account. This work presents phenomenological models which describe the oxygen uptake and the diffusion into elastomers based on an improved understanding of ongoing chemical processes and diffusion limiting modifications. On the one side, oxygen uptake is modelled by means of Henry's law in which solubility is a function of the temperature as well as the ageing progress. The latter is an irreversible process and described by an inner differential evolution equation. On the other side

  13. Magnetostrictive effect of magnetorheological elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Guan Xinchun [School of Civil Engineering, Harbin Institute of Technology, Harbin 150090 (China)], E-mail: guanxch@hit.edu.cn; Dong Xufeng [School of Civil Engineering, Harbin Institute of Technology, Harbin 150090 (China); Ou Jinping [School of Civil Engineering, Harbin Institute of Technology, Harbin 150090 (China); School of Civil Engineering, Dalian University of Technology, Dalian 116024 (China)

    2008-02-15

    Magnetorheological elastomer (MRE) has been known for its magnetic field-dependent stiffness, but only a few works study its magnetostrictive property. The aim of this paper is to present results of studies on magnetostriction of the MRE consisting of carbonyl iron particles displaced in the matrix made of a silicone rubber. The MRE samples were placed in the magnetic field that varied from 0 to 636 kA/m, which was produced by the PEM-1022LS magnetic system. The longitudinal magnetostriction of the samples was measured by strain gauge. Three different tests were performed: (1) increased and decreased magnetic fields on four different volume fraction MREs with particles randomly dispersed, namely, 0%, 15%, 20% and 27%, (2) increased and decreased magnetic fields on three different MREs, with the same volume fraction of particles but varied orientation, namely, randomly, vertically and parallelly; (3) increased and decreased magnetic field three times continuously on the MRE with particles randomly oriented. Results indicated that (1) magnetostrictive effect increases with increase in volume fraction of particles and magnetostriction generally increases with increasing magnetic field, (2) orientation of particles influences the magnetostrictive performance significantly, (3) with increase of times of tests, saturation strain decayed and some remnant magnetostriction existed after switching off the magnetic field in each cycle. The mechanism of magnetostrictive effect of the composite was proposed to explain the phenomenon.

  14. Growth and characterization of DL-Mandelic acid (C6H5CH(OH)CO2H) single crystal for third-order nonlinear optical applications

    Science.gov (United States)

    Jayaprakash, P.; Sangeetha, P.; Peer Mohamed, M.; Vinitha, G.; Muthu, S.; Prakash, M.; Lydia Caroline, M.

    2017-11-01

    An organic conjugated chromophore DL-mandelic acid (DLMA) single crystal was synthesized and grown-up by means of slow evaporation technique. Single crystal X-ray diffraction study proclaimed that the DLMA crystal crystallized in monoclinic system with centrosymmetric space group P21/c. The various characteristic fundamental vibration frequencies were identified by FTIR spectroscopic studies. UV-visible spectral analysis concluded that the lower cut-off wavelength and calculated direct optical band gap of DLMA as 257 nm and 5.40 eV respectively. Thermal property of DL-mandelic acid was established through thermogravimetric and differential scanning calorimetric technique. The electric field response of DLMA crystal was investigated from the dielectric studies at a few selected temperatures and frequencies. The quantum chemical assessments such as HOMO-LUMO, molecular electrostatic potential and NLO activity were calculated and presented. In order to determine mechanical strength of DLMA crystal for various loads using Vickers microhardness tester. The real and imaginary parts of the third-order susceptibility (χ3) were evaluated with the Z-scan technique using closed and open signatures respectively and was found to be Re (χ3) = 4.15 × 10-6 esu and Im (χ3) = 0.47 × 10-6 esu.

  15. Transverse vibration of nematic elastomer Timoshenko beams.

    Science.gov (United States)

    Zhao, Dong; Liu, Ying; Liu, Chuang

    2017-01-01

    Being a rubber-like liquid crystalline elastomer, a nematic elastomer (NE) is anisotropic viscoelastic, and displays dynamic soft elasticity. In this paper, the transverse vibration of a NE Timoshenko beam is studied based on the linear viscoelasticity theory of nematic elastomers. The governing equation of motion for the transverse vibration of a NE Timoshenko beam is derived. A complex modal analysis method is used to obtain the natural frequencies and decrement coefficients of NE beams. The influences of the nematic director rotation, the rubber relaxation time, and the director rotation time on the vibration characteristic of NE Timoshenko beams are discussed in detail. The sensitivity of the dynamic performance of NE beams to director initial angle and relaxation times provides a possibility of intelligent controlling of their dynamic performance.

  16. Deformation and instabilities in dielectric elastomer composites

    Science.gov (United States)

    Li, Wenyuan; Landis, Chad M.

    2012-09-01

    The deformation behavior in dielectric elastomer composites due to applied mechanical and electrical loadings is investigated using finite element methods. The composite structure consists of a dielectric elastomer matrix with a regular square array of cylindrical holes or rigid conducting inclusions. The dielectric elastomer material is represented with either a compressible Neo-Hookean model for the elasticity or a compressible Gent model. Following previous work, the dielectric constant relating the true electric displacement to the true electric field is taken to be independent of the deformation. The finite element method is used to analyze the electromechanical behavior of representative unit cells of the composite material structure. Results are presented for the stress-strain, electric field-electric displacement and coupled electromechanical responses of the different composite types.

  17. The application of second-order approximation of Taylor series in thickness shear vibration analysis of quartz crystal microbalances.

    Science.gov (United States)

    Li, Peng; Jin, Feng; Sun, Qing; Ma, Jianxun

    2015-04-01

    The inertia force caused by an additional mass layer is usually adopted to simulate the effective mechanical boundary condition in a quartz crystal microbalance (QCM), which may yield incorrect results when the upper layer becomes relative thicker. Thus, a detail analysis of the thickness shear vibration in a QCM for detecting the characteristics of the upper isotropic layer is proceeded based on a second-order approximation of Taylor series. The result calculated by this method has a higher accuracy than that of inertial-force approximation. According to these outcomes, the free and forced vibration has been illustrated, as well as transient effects during the switching on/off processes or under a sudden fluctuation of the driving-voltage amplitude or frequency. It has been revealed by numerical simulation that the additional mass layer has a great influence on the mechanical performance of QCM, including the resonance frequency, amplitudes of displacement and admittance, response time of the transient processes, and so on. These findings can prove effective guidance for physical phenomenon explanations and experimental measurement in mass sensor devices. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Conformational specificity of non-canonical base pairs and higher order structures in nucleic acids: crystal structure database analysis

    Science.gov (United States)

    Mukherjee, Shayantani; Bansal, Manju; Bhattacharyya, Dhananjay

    2006-10-01

    Non-canonical base pairs contribute immensely to the structural and functional variability of RNA, which calls for a detailed characterization of their spatial conformation. Intra-base pair parameters, namely propeller, buckle, open-angle, stagger, shear and stretch describe structure of base pairs indicating planarity and proximity of association between the two bases. In order to study the conformational specificities of non-canonical base pairs occurring in RNA crystal structures, we have upgraded NUPARM software to calculate these intra-base pair parameters using a new base pairing edge specific axis system. Analysis of base pairs and base triples with the new edge specific axis system indicate the presence of specific structural signatures for different classes of non-canonical pairs and triples. Differentiating features could be identified for pairs in cis or trans orientation, as well as those involving sugar edges or C-H-mediated hydrogen bonds. It was seen that propeller for all types of base pairs in cis orientation are generally negative, while those for trans base pairs do not have any preference. Formation of a base triple is seen to reduce propeller of the associated base pair along with reduction of overall flexibility of the pairs. We noticed that base pairs involving sugar edge are generally more non-planar, with large propeller or buckle values, presumably to avoid steric clash between the bulky sugar moieties. These specific conformational signatures often provide an insight into their role in the structural and functional context of RNA.

  19. Numerical study and topology optimization of 1D periodic bimaterial phononic crystal plates for bandgaps of low order Lamb waves.

    Science.gov (United States)

    Hedayatrasa, Saeid; Abhary, Kazem; Uddin, Mohammad

    2015-03-01

    The optimum topology of bimaterial phononic crystal (PhCr) plates with one-dimensional (1D) periodicity to attain maximum relative bandgap width of low order Lamb waves is computationally investigated. The evolution of optimized topology with respect to filling fraction of constituents, alternatively stiff scattering inclusion, is explored. The underlying idea is to develop PhCr plate structures with high specific bandgap efficiency at particular filling fraction, or further with multiscale functionality through gradient of optimized PhCr unitcell all over the lattice array. Multiobjective genetic algorithm (GA) is employed in this research in conjunction with finite element method (FEM) for topology optimization of silicon-tungsten PhCr plate unitcells. A specialized FEM model is developed and verified for dispersion analysis of plate waves and calculation of modal response. Modal band structure of regular PhCr plate unitcells with centric scattering layer is studied as a function of aspect ratio and filling fraction. Topology optimization is then carried out for a few aspect ratios, with and without prescribed symmetry, over various filling fractions. The efficiency of obtained solutions is verified as compared to corresponding regular centric PhCr plate unitcells. Moreover, being inspired by the obtained optimum topologies, definite and easy to produce topologies are proposed with enhanced bandgap efficiency as compared to centric unitcells. Finally a few cases are introduced to evaluate the frequency response of finite PhCr plate structures produced by achieved topologies and also to confirm the reliability of calculated modal band structures. Cases made by consecutive unitcells of different filling fraction are examined in order to attest the bandgap efficiency and multiscale functionality of such graded PhCr plate structures. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  20. Single crystal growth and structural evolution across the 1st order valence transition in (Pr1-yYy)1-xCaxCoO3-δ

    Science.gov (United States)

    Schreiber, N. J.; Zhang, Junjie; Zheng, Hong; Freeland, J. W.; Chen, Yu-Sheng; Mitchell, J. F.; Phelan, D.

    2017-10-01

    Praseodymium-containing cobalt perovskites, such as (Pr1-yYy)1-xCaxCoO3-δ, have been argued to undergo a first-order charge shift between Pr and hybridized Co-O orbitals that leads to a metal-insulator transition at a temperature, TVT. Magnetization and x-ray absorption spectroscopy measurements on single crystals of (Pr0.85Y0.15)0.7Ca0.3CoO3-δ grown in an IR image furnace under 40-60 bar of oxygen confirm the presence of this valence transition. Single crystal x-ray synchrotron diffraction measurements are consistent with an isomorphic phase transition at TVT. No evidence of charge ordering was revealed by the single crystal diffraction. Dissimilar to analytical transmission electron microscopy measurements performed on a grain from a polycrystalline sample that revealed an oxygen vacancy order-disorder transition at TVT, the present single-crystal measurements did not evidence such a transition, likely reflecting a lower density of oxygen vacancies in the high-pO2 grown single crystals.

  1. Magnetically Responsive Elastomer-Silicon Hybrid Surfaces for Fluid and Light Manipulation.

    Science.gov (United States)

    Yang, Zining; Park, Jun Kyu; Kim, Seok

    2017-11-24

    Stimuli-responsive surfaces with tunable fluidic and optical properties utilizing switchable surface topography are of significant interest for both scientific and engineering research. This work presents a surface involving silicon scales on a magnetically responsive elastomer micropillar array, which enables fluid and light manipulation. To integrate microfabricated silicon scales with ferromagnetic elastomer micropillars, transfer printing-based deterministic assembly is adopted. The functional properties of the surface are completely dictated by the scales with optimized lithographic patterns while the micropillar array is magnetically actuated with large-range, instantaneous, and reversible deformation. Multiple functions, such as tunable wetting, droplet manipulation, tunable optical transmission, and structural coloration, are designed, characterized, and analyzed by incorporating a wide range of scales (e.g., bare silicon, black silicon, photonic crystal scales) in both in-plane and out-of-plane configurations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Single-crystal neutron diffraction study of Nd magnetic ordering in NdFeO{sub 3} at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Bartolome, J.; Palacios, E.; Kuzmin, M.D.; Bartolome, F. [Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, 50009 Zaragoza (Spain); Sosnowska, I.; Przenioslo, R. [Institute of Experimental Physics, Warsaw University, PL-00 681 Warsaw (Poland); Sonntag, R. [Hahn-Meitner-Institut, D-14109 Berlin (Germany); Lukina, M.M. [Department of Physics, Moscow State University, Leninskie Gory, 119899 Moscow (Russia)

    1997-05-01

    The temperature variation of the (100) and (010) neutron diffraction peak intensities, related only to the Nd magnetic moments, have been measured on a NdFeO{sub 3} single crystal, at temperatures down to 70 mK. The (100) peak becomes noticeable below 25 K while the (010) peak only gives an appreciable contribution below 1 K. Above T{sub N2}{approx}1K the (100) peak intensity is accounted for by the electronic magnetic moments polarized by the Nd-Fe exchange field. Near T{sub N2} a change of slope is observed in the temperature dependence of the (100) reflection intensity, demonstrating the crossover from the above polarization of Nd under the Nd-Fe exchange to proper long-range ordering due to Nd-Nd interaction. Below {approximately}0.4K another mechanism, polarization of Nd nuclear moments by hyperfine field, contributes to the intensity of the (100) and (010) peaks. A simple mean-field model explains consistently the observed temperature dependence of the diffraction intensities as well as earlier specific-heat data. The main feature of this model is allowance for Van Vleck susceptibility, which appears to play an important role in the overall polarization of Nd. The values of the hyperfine field at the Nd nuclei H{sub hf}=1.0{plus_minus}0.15MOe and of the Nd electronic magnetic moment {mu}{sub Nd}=0.9{mu}{sub B} are deduced, the ratio H{sub hf}/{mu}{sub Nd} being the same as in other Nd compounds. {copyright} {ital 1997} {ital The American Physical Society}

  3. Behavior of magnetorheological elastomers with coated particles

    Science.gov (United States)

    Behrooz, Majid; Sutrisno, Joko; Zhang, Lingyue; Fuchs, Alan; Gordaninejad, Faramarz

    2015-03-01

    Iron particle coating can improve the behavior of magnetorheological elastomers (MREs) by inhibiting iron particle rusting; however, such a process can change physical properties of MREs such as oxidation resistance, shear modulus, and stiffness change due to an applied magnetic field. In this study, MRE samples are fabricated with regular and polymerized iron particles. To investigate the possibility and extent of these changes, polymerized particle MRE samples are made using a combination of reversible addition fragmentation chain transfer and click chemistry. Shear test sample MREs with pure elastomer and 50 wt% MRE with and without polymerization are fabricated. To observe the effect of oxidation on shear properties of MREs, pure elastomer and 50 wt% coated and non-coated samples are oxidized using accelerated oxidation procedure. Experimental results show that oxidation significantly reduces the shear modulus of the elastomer matrix. The coating process of iron particles does not significantly change the shear modulus of resulting MREs but reduces the loss of shear modulus due to oxidation.

  4. Use of elastomers in regenerative braking systems

    Science.gov (United States)

    The storage of potential energy as strain energy in elastomers was investigated. The evolution of the preferred stressing scheme is described, and test results on full-size elastomeric energy storage units sized for an automotive regenerative braking system application are presented. The need for elastomeric material improvements is also discussed.

  5. Actuation response of polyacrylate dielectric elastomers

    DEFF Research Database (Denmark)

    Kofod, G.; Kornbluh, R.; Pelrine, R.

    2001-01-01

    Polyacrylate dielectric elastomers have yielded extremely large strain and elastic energy density suggesting that they are useful for many actuator applications. A thorough understanding of the physics underlying the mechanism of the observed response to an electric field can help develop improve...

  6. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Mateiu, Ramona Valentina; Yu, Liyun; Skov, Anne Ladegaard

    2017-01-01

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we investigate the electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers. Two types...

  7. Rheological properties of olefinic thermoplastic elastomer blends

    NARCIS (Netherlands)

    Sengers, W.G.F.

    2005-01-01

    Thermoplastic Elastomers (TPE) are a class of materials that have rubber-like properties and can be processed like thermoplastic polymers. In this thesis, the rheological properties of two TPE blends are correlated to their morphology. The thermoplastic vulcanisates (TPV) consist of micron-sized,

  8. Conductive elastomers by a new latex process

    Science.gov (United States)

    Electrically conductive polymers such as polyaniline can be used to in production of light-emitting diodes, printed circuit board components, antistatic materials, etc. Highly filled elastomers, such as those filled with metallic powders, can also conduct electricity. However, limitations due to co...

  9. Toward a predictive model for the failure of elastomer seals.

    Science.gov (United States)

    Molinari, Nicola; Khawaja, Musab; Sutton, Adrian; Mostofi, Arash; Baker Hughes Collaboration

    Nitrile butadiene rubber (NBR) and hydrogenated-NBR (HNBR) are widely used elastomers, especially as seals in oil and gas industry. During exposure to the extreme temperatures and pressures typical of well-hole conditions, ingress of gases causes degradation of performance, including mechanical failure. Using computer simulations, we investigate this problem at two different length- and time-scales. First, starting with our model of NBR based on the OPLS all-atom force-field, we develop a chemically-inspired description of HNBR, where C=C double bonds are saturated with either hydrogen or intramolecular cross-links, mimicking the hydrogenation of NBR to form HNBR. We validate against trends for the mass density and glass transition temperature for HNBR as a function of cross-link density, and for NBR as a function of the fraction of acrylonitrile in the copolymer. Second, a coarse-grained approach is taken in order to study mechanical behaviour and to overcome the length- and time-scale limitations inherent to the all-atom model. The effect of nanoparticle fillers added to the elastomer matrix is investigated. Our initial focus is on understanding the mechanical properties at the elevated temperatures and pressures experienced in well-hole conditions. Baker Hughes.

  10. Effects of plasticization of a soft silicone for dielectric elastomer actuation

    Science.gov (United States)

    Galantini, Fabia; Carpi, Federico; Gallone, Giuseppe

    2013-10-01

    Dielectric elastomer (DE) actuators exploit electrically induced deformations of insulating rubbery materials, as a means to transduce electrical energy into mechanical work. To enable large deformations, recent studies have demonstrated the advantage of either using elastomers that suppress pull-in electromechanical instability or driving the actuator at the verge of instability while still preventing it. Whenever these strategies are not applicable, softening the material remains the mechanical approach of choice to enable large deformations at relatively low electric fields. As the most common approach to lower the elastic modulus of an elastomer is the use of plasticizers, understanding their effects also on other properties of the elastomer is important, especially to actuator designers. Aimed at gaining insights in this respect, this paper presents an extensive chemical-physical, dielectric, mechanical and electromechanical characterization, for different amounts of a plasticizer, of one of the softest commercial silicones demonstrated for DE actuation (elastic modulus of the order of 100 kPa). The results showed the interplaying effects of a variable addition of the plasticizer, elucidating key features that could thus serve as a guide to the design of actuators for specific needs.

  11. Step Cycle Deformation Processing of Elastomers and Gels Based on Semicrystalline Polyolefin-based Block Copolymers

    Science.gov (United States)

    Deplace, Fanny; Wang, Zhigang; Lynd, Nathaniel A.; Hotta, Atsushi; Fredrickson, Glenn H.; Kramer, Edward J.; Rose, Jeffrey M.; Cherian, Anna E.; Coates, Geoffrey W.; Ohtaki, Hisashi; Hirokane, K.; Yamada, F.; Shin, Yong-Woo; Shimizu, Fumihiko

    2009-03-01

    Recent catalysts have enabled the synthesis of block copolymers with semicrystalline syndiotactic and isotactic polypropylene endblocks and amorphous ethylene-r-propylene midblocks. In these copolymers, the crystals play the role of physical crosslinks which can deform plastically under stretching. Neat elastomers, gels in mineral oil and gels from which mineral oil has been extracted have been subjected to step cycle tensile tests. The incremental plastic deformation of the crystals has dramatic effects on the true stress versus extension ratio curves. Moreover, small and wide angle X-ray scattering experiments during step cyclic tests revealed the evolution of the microstructure of the crystalline blocks: crystal fibrils and crystals in the fibrils are oriented parallel to the tensile direction at large strains and once the stress has decreased to zero, the fibrils return to being randomly oriented again.

  12. Dielectric Elastomers for Fluidic and Biomedical Applications

    Science.gov (United States)

    McCoul, David James

    Dielectric elastomers have demonstrated tremendous potential as high-strain electromechanical transducers for a myriad of novel applications across all engineering disciplines. Because their soft, viscoelastic mechanical properties are similar to those of living tissues, dielectric elastomers have garnered a strong foothold in a plethora of biomedical and biomimetic applications. Dielectric elastomers consist of a sheet of stretched rubber, or elastomer, coated on both sides with compliant electrode materials; application of a voltage generates an electrostatic pressure that deforms the elastomer. They can function as soft generators, sensors, or actuators, and this last function is the focus of this dissertation. Many design configurations are possible, such as stacks, minimum energy structures, interpenetrating polymer networks, shape memory dielectric elastomers, and others; dielectric elastomers are already being applied to many fields of biomedicine. The first part of the original research presented in this dissertation details a PDMS microfluidic system paired with a dielectric elastomer stack actuator of anisotropically prestrained VHB(TM) 4910 (3M(TM)) and single-walled carbon nanotubes. These electroactive microfluidic devices demonstrated active increases in microchannel width when 3 and 4 kV were applied. Fluorescence microscopy also indicated an accompanying increase in channel depth with actuation. The cross-sectional area strains at 3 and 4 kV were approximately 2.9% and 7.4%, respectively. The device was then interfaced with a syringe pump, and the pressure was measured upstream. Linear pressure-flow plots were developed, which showed decreasing fluidic resistance with actuation, from 0.192 psi/(microL/min) at 0 kV, to 0.160 and 0.157 psi/(microL/min) at 3 and 4 kV, respectively. This corresponds to an ~18% drop in fluidic resistance at 4 kV. Active de-clogging was tested in situ with the device by introducing ~50 microm diameter PDMS microbeads and

  13. Temperature-induced reversible first-order single crystal to single crystal phase transition in Boc-γ(4)(R)Val-Val-OH: interplay of enthalpy and entropy.

    Science.gov (United States)

    Pal, Rumpa; Reddy, M B Madhusudana; Dinesh, Bhimareddy; Balaram, Padmanabhan; Guru Row, Tayur N

    2014-10-09

    Crystals of Boc-γ(4)(R)Val-Val-OH undergo a reversible first-order single crystal to single crystal phase transition at Tc ≈ 205 K from the orthorhombic space group P22121 (Z' = 1) to the monoclinic space group P21 (Z' = 2) with a hysteresis of ∼2.1 K. The low-temperature monoclinic form is best described as a nonmerohedral twin with ∼50% contributions from its two components. The thermal behavior of the dipeptide crystals was characterized by differential scanning calorimetry experiments. Visual changes in birefringence of the sample during heating and cooling cycles on a hot-stage microscope with polarized light supported the phase transition. Variable-temperature unit cell check measurements from 300 to 100 K showed discontinuity in the volume and cell parameters near the transition temperature, supporting the first-order behavior. A detailed comparison of the room-temperature orthorhombic form with the low-temperature (100 K) monoclinic form revealed that the strong hydrogen-bonding motif is retained in both crystal systems, whereas the non-covalent interactions involving side chains of the dipeptide differ significantly, leading to a small change in molecular conformation in the monoclinic form as well as a small reorientation of the molecules along the ac plane. A rigid-body thermal motion analysis (translation, libration, screw; correlation of translation and libration) was performed to study the crystal entropy. The reversible nature of the phase transition is probably the result of an interplay between enthalpy and entropy: the low-temperature monoclinic form is enthalpically favored, whereas the room-temperature orthorhombic form is entropically favored.

  14. Anomalous multi-order Raman scattering in LaMnO_3: a signature of a quantum lattice effect in a Jahn-Teller crystal

    OpenAIRE

    Kovaleva, N. N.; Kusmartseva, O. E.; Kugel, K. I.; Maksimov, A. A.; Nuzhnyy, D.; Balbashov, A. M.; Demikhov, E. I.; Dejneka, A.; Trepakov, V. A.; Kusmartsev, F. V.; Stoneham, A. M.

    2014-01-01

    The multi-order Raman scattering is studied up to a fourth order for a detwinned LaMnO_3 crystal. Based on a comprehensive data analysis of the polarisation-dependent Raman spectra, we show that the anomalous features in the multi-order scattering could be the sidebands on the low-energy mode at about 25 cm-1. We suggest that this low-energy mode stems from the tunneling transition between the potential energy minima arising near the Jahn-Teller Mn3+ ion due to the lattice anharmonicity, and ...

  15. Elastomers in mud motors for oil field applications

    Energy Technology Data Exchange (ETDEWEB)

    Hendrik, J. [Baker Hughes INTEQ GmbH, Celle (Germany)

    1997-08-01

    Mud motors, the most frequently used downhole drilling motors in modern drilling systems, are described in their application and function. The elastomeric liner in a mud motor acts as a huge continuous seal. Important properties of elastomers such as chemical resistance, fatigue resistance, mechanical strength, abrasion resistance, bonding to steel and processability are discussed. Advantages and disadvantages of NBR, HNBR, FKM, TFEP, and EPDM elastomers for mud motor applications are briefly described. The importance of drilling fluids and their physical and chemical impact on motor elastomers are described. Drilling fluids are categorized in: oil based-, synthetic-, and water based. Results of compatibility tests in the different drilling muds of the presented categories demonstrate the complexity of elastomer development. Elastomers with an equally good performance in all drilling muds are not available. Future developments and improvements are directed towards higher chemical resistance at higher service temperatures. This will be possible only with improved elastomer-to-metal bonding, increased mechanical and better dynamic properties.

  16. Types and properties of elastomer materials used in CANDU reactor

    Energy Technology Data Exchange (ETDEWEB)

    You, Ho Sik; Jeong, Jin Kon [Korea Atomic Energy Research Institute, Daeduk (Korea, Republic of)

    1996-05-01

    Properties and kinds of elastomer materials used in a CANDU power plant have been described. The elastomer materials have been used as a sealing material in the components f nuclear power plant since they have many excellent properties that can not be seen in other materials. It is very important to select proper elastomer materials used in the nuclear power plant are required to have resistance to temperature as well as radiation. According to the experimental results performed at some laboratories including the Chalk River Laboratory of AECL, elastomer materials with high resistance to temperature and radiation are Nitrile, Ethylene, Propylene and Butyl. These materials have been used in a lot of components of Wolsong unit 1 and Wolsong 2, 3 and 4 which are under elastomer material. Therefore, the studies on the standardization are currently under way to limit about 10 different kinds of elastomer materials to be used in the plant. 16 tabs., 1 fig., 12 refs. (Author) .new.

  17. Sectioned Core Doping Effect on Higher-Order Mode Amplification in Yb-Doped Rod-Type Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Poli, F.; Lægsgaard, Jesper; Passaro, D.

    2009-01-01

    The amplification properties of guided modes in Yb-doped rod-type photonic crystal fibers with sectioned core doping have been investigated, evaluating the doped-area radius which provides the effective suppression of both LP 11- and LP02-like modes.......The amplification properties of guided modes in Yb-doped rod-type photonic crystal fibers with sectioned core doping have been investigated, evaluating the doped-area radius which provides the effective suppression of both LP 11- and LP02-like modes....

  18. Effect of temperature on electromechanical instability of dielectric elastomers

    Science.gov (United States)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Wang, Yongquan; Qiang, Junhua

    2012-04-01

    The electromechanical behavior of dielectric elastomer is strongly affected by the temperature. Very few models accounting for the effects of temperature exist in the literature. A recent experiment showed that the variation of dielectric constant of the most widely used dielectric elastomer (VHB 4910, 3M) according to temperature is relatively significant. In this paper, we develop a thermodynamic model to study the influence of temperature on the instability in dielectric elastomer by involving deformation and temperature-dependent dielectric constant. The results indicate that the increase of temperature could improve the actuation stress and the electromechanical instability of the elastomer.

  19. Spontaneous piezoelectric effect as order parameter in (NH{sub 4}){sub 2}CuBr{sub 4}·2H{sub 2}O crystal

    Energy Technology Data Exchange (ETDEWEB)

    Tylczyński, Z., E-mail: zbigtyl@amu.edu.pl; Wiesner, M.; Trzaskowska, A.

    2016-11-01

    Temperature change of piezoelectric properties of (NH{sub 4}){sub 2}CuBr{sub 4}·2H{sub 2}O crystal in the low-temperature ferroelastoelectric phase is studied. The macroscopic order parameter is proved to be the h{sub 36} component of the spontaneous piezoelectric tensor. The critical exponent related with the phase transition is α=0.60±0.05.

  20. Geometry of Thin Nematic Elastomer Sheets

    Science.gov (United States)

    Aharoni, Hillel; Sharon, Eran; Kupferman, Raz

    2014-12-01

    A thin sheet of nematic elastomer attains 3D configurations depending on the nematic director field upon heating. In this Letter, we describe the intrinsic geometry of such a sheet and derive an expression for the metric induced by general nematic director fields. Furthermore, we investigate the reverse problem of constructing a director field that induces a specified 2D geometry. We provide an explicit recipe for how to construct any surface of revolution using this method. Finally, we show that by inscribing a director field gradient across the sheet's thickness, one can obtain a nontrivial hyperbolic reference curvature tensor, which together with the prescription of a reference metric allows dictation of actual configurations for a thin sheet of nematic elastomer.

  1. Structural phase transitions in isotropic magnetic elastomers

    Science.gov (United States)

    Meilikhov, E. Z.; Farzetdinova, R. M.

    2016-06-01

    Magnetic elastomers represent a new type of materials that are "soft" matrices with "hard" magnetic granules embedded in them. The elastic forces of the matrix and the magnetic forces acting between granules are comparable in magnitude even under small deformations. As a result, these materials acquire a number of new properties; in particular, their mechanical and/or magnetic characteristics can depend strongly on the polymer matrix filling with magnetic particles and can change under the action of an external magnetic field, pressure, and temperature. To describe the properties of elastomers, we use a model in which the interaction of magnetic granules randomly arranged in space with one another is described in the dipole approximation by the distribution function of dipole fields, while their interaction with the matrix is described phenomenologically. A multitude of deformation, magnetic-field, and temperature effects that are described in this paper and are quite accessible to experimental observation arise within this model.

  2. A Coating-Free Nonfouling Polymeric Elastomer.

    Science.gov (United States)

    Hung, Hsiang-Chieh; Jain, Priyesh; Zhang, Peng; Sun, Fang; Sinclair, Andrew; Bai, Tao; Li, Bowen; Wu, Kan; Tsao, Caroline; Liu, Erik J; Sundaram, Harihara S; Lin, Xiaojie; Farahani, Payam; Fujihara, Timothy; Jiang, Shaoyi

    2017-08-01

    Medical devices face nonspecific biofouling from proteins, cells, and microorganisms, which significantly contributes to complications and device failure. Imparting these devices with nonfouling capabilities remains a major challenge, particularly for those made from elastomeric polymers. Current strategies, including surface coating and copolymerization/physical blending, necessitate compromise among nonfouling properties, durability, and mechanical strength. Here, a new strategy is reported to achieve both high bulk mechanical strength and excellent surface nonfouling properties, which are typically contradictory, in one material. This is realized through a nonfouling polymeric elastomer based on zwitterionic polycarboxybetaine derivatives. By hiding both charged moieties of the zwitterionic compounds with hydrocarbon ester and tertiary amine groups, the bulk polymer itself is elastomeric and hydrophobic while its superhydrophilic surface properties are restored upon hydrolysis. This coating-free nonfouling elastomer is a highly promising biomaterial for biomedical and engineering applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Novel electrode-elastomer combinations for improved performance and application of dielectric elastomers

    Science.gov (United States)

    Yuan, Wei

    Dielectric elastomers are the most promising technology for mimicking human muscles in terms of strain, stress, and work density, etc. Actuators have been fabricated based on different design concepts and configurations for applications in robotics, prosthetic devices, medical implants, pumps, and valves. However, to date these actuators have experienced high rates of failure caused by electrical shorting of the compliant electrodes through the elastomer film during electrical breakdown, which has prevented their practical application. In this thesis, single walled carbon nanotube (SWNT) thin films were employed as compliant electrodes for dielectric elastomers to reduce the rate of failure. Thanks to the high aspect ratio of the SWNTs, the electrodes maintain substantial conductance at high biaxial strains. 3M VHB acrylics can be actuated up to 200% area strain with SWNT electrodes, this matches the performance of actuators with carbon grease electrodes. During uni-directional stretching, SWNT electrodes can maintain surface conductivity up to 700% linear strain. SWNT electrodes can experience a self-clearing process under high voltage discharging and electrically isolate the electrodes around the breakdown sites when breakdown events happen. With conventional dielectric elastomer electrode materials such as carbon grease and carbon black, a single breakdown event results in a permanent loss in the actuator's functionality. In contrast, for SWNT electrodes, the SWNTs around the breakdown site will be degraded and become non-conductive. The non-conductive area expands outward until the high voltage discharging stops. As such, the opposing electrodes are prevented from coming into contact with each other and forming an electrical short and the breakdown site is electrically isolated from the remainder of the active area. Despite the existence of the breakdown sites, the dielectric elastomer will resume its functionality and avoid permanent failure. Thus, dielectric

  4. Toughening elastomers using mussel-inspired iron-catechol complexes

    Science.gov (United States)

    Filippidi, Emmanouela; Cristiani, Thomas R.; Eisenbach, Claus D.; Waite, J. Herbert; Israelachvili, Jacob N.; Ahn, B. Kollbe; Valentine, Megan T.

    2017-10-01

    Materials often exhibit a trade-off between stiffness and extensibility; for example, strengthening elastomers by increasing their cross-link density leads to embrittlement and decreased toughness. Inspired by cuticles of marine mussel byssi, we circumvent this inherent trade-off by incorporating sacrificial, reversible iron-catechol cross-links into a dry, loosely cross-linked epoxy network. The iron-containing network exhibits two to three orders of magnitude increases in stiffness, tensile strength, and tensile toughness compared to its iron-free precursor while gaining recoverable hysteretic energy dissipation and maintaining its original extensibility. Compared to previous realizations of this chemistry in hydrogels, the dry nature of the network enables larger property enhancement owing to the cooperative effects of both the increased cross-link density given by the reversible iron-catecholate complexes and the chain-restricting ionomeric nanodomains that they form.

  5. Dielectric elastomer generators that stack up

    Science.gov (United States)

    McKay, T. G.; Rosset, S.; Anderson, I. A.; Shea, H.

    2015-01-01

    This paper reports the design, fabrication, and testing of a soft dielectric elastomer power generator with a volume of less than 1 cm3. The generator is well suited to harvest energy from ambient and from human body motion as it can harvest from low frequency (sub-Hz) motions, and is compact and lightweight. Dielectric elastomers are highly stretchable variable capacitors. Electrical energy is produced when the deformation of a stretched, charged dielectric elastomer is relaxed; like-charges are compressed together and opposite-charges are pushed apart, resulting in an increased voltage. This technology provides an opportunity to produce soft, high energy density generators with unparalleled robustness. Two major issues block this goal: current configurations require rigid frames that maintain the dielectric elastomer in a prestretched state, and high energy densities have come at the expense of short lifetime. This paper presents a self-supporting stacked generator configuration which does not require rigid frames. The generator consists of 48 generator films stacked on top of each other, resulting in a structure that fits within an 11 mm diameter footprint while containing enough active material to produce useful power. To ensure sustainable power production, we also present a mathematical model for designing the electronic control of the generator which optimizes energy production while limiting the electrical stress on the generator below failure limits. When cyclically compressed at 1.6 Hz, our generator produced 1.8 mW of power, which is sufficient for many low-power wireless sensor nodes. This performance compares favorably with similarly scaled electromagnetic, piezoelectric, and electrostatic generators. The generator’s small form factor and ability to harvest useful energy from low frequency motions such as tree swaying or shoe impact provides an opportunity to deliver power to remote wireless sensor nodes or to distributed points in the human body

  6. Temperature tunable optical gratings in nematic elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sungur, Emel; Mager, Loic; Boeglin, Alex; Dorkenoo, Kokou D. [IPCMS-CNRS UMR 7504, 23 rue du Loess, BP 43, Strasbourg Cedex 2 (France); Li, Min-Hui; Keller, Patrick [Institut Curie, CNRS 168, Paris Cedex 5 (France)

    2010-01-15

    We have investigated the behaviour of temperature dependent periodic-index gratings fabricated in a nematic elastomer. The gratings have been obtained by photopolymerisation under a microscopy apparatus. Contraction properties, as well as diffraction properties, have been studied as a function of temperature. Unidirectional contraction has been demonstrated by means of circular figure deformation and the polarisation dependency of the diffraction by the gratings has been determined. (orig.)

  7. Dielectric Elastomer Based "Grippers" for Soft Robotics.

    Science.gov (United States)

    Shian, Samuel; Bertoldi, Katia; Clarke, David R

    2015-11-18

    The use of few stiff fibers to control the deformation of dielectric elastomer actuators, in particular to break the symmetry of equi-biaxial lateral strain in the absence of prestretch, is demonstrated. Actuators with patterned fibers are shown to evolve into unique shapes upon electrical actuation, enabling novel designs of gripping actuators for soft robotics. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Toward a predictive model for elastomer seals

    Science.gov (United States)

    Molinari, Nicola; Khawaja, Musab; Sutton, Adrian; Mostofi, Arash

    Nitrile butadiene rubber (NBR) and hydrogenated-NBR (HNBR) are widely used elastomers, especially as seals in oil and gas applications. During exposure to well-hole conditions, ingress of gases causes degradation of performance, including mechanical failure. We use computer simulations to investigate this problem at two different length and time-scales. First, we study the solubility of gases in the elastomer using a chemically-inspired description of HNBR based on the OPLS all-atom force-field. Starting with a model of NBR, C=C double bonds are saturated with either hydrogen or intramolecular cross-links, mimicking the hydrogenation of NBR to form HNBR. We validate against trends for the mass density and glass transition temperature for HNBR as a function of cross-link density, and for NBR as a function of the fraction of acrylonitrile in the copolymer. Second, we study mechanical behaviour using a coarse-grained model that overcomes some of the length and time-scale limitations of an all-atom approach. Nanoparticle fillers added to the elastomer matrix to enhance mechanical response are also included. Our initial focus is on understanding the mechanical properties at the elevated temperatures and pressures experienced in well-hole conditions.

  9. Analytical and experimental analysis of magnetorheological elastomers

    Science.gov (United States)

    Trabia, Sarah

    Many engineering applications ranging from robotic joints to shock and vibration mitigation can benefit by incorporating components with variable stiffness. In addition, variable stiffness structures can provide haptic feedback (the sense of touch) to the user. In this work, it is proposed to study Magnetorheological Elastomers (MRE), where iron particles within the elastomer compound develop a dipole interaction energy, to be used in a device for haptic feedback. A novel feature of this MRE device is to introduce a field-induced variable shear modulus bias via a permanent magnet and using a current input to the electromagnetic control coil to change the modulus of the elastomer in both directions (softer or harder). In this preliminary work, both computational and experimental results of the proposed MRE design are presented. The design is created in COMSOL to verify that the magnetic field is in the desired direction. MRE was fabricated and characterized using a Bose Dynamic Mechanical Analyzer for the shear modulus. Using this information, it is possible to know how the MRE will react in magnetic fields within the haptic feedback device. Additionally, a model for an MRE is developed in a multi-physics COMSOL program that is linked to a MATLAB function that predicts the shear modulus and incorporates it into the material properties to best simulate the MRE's ability to change shear modulus.

  10. Low temperature time resolved photoluminescence in ordered and disordered Cu{sub 2}ZnSnS{sub 4} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Raadik, Taavi, E-mail: taavi.raadik@ttu.ee [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Krustok, Jüri; Kauk-Kuusik, M.; Timmo, K.; Grossberg, M. [Department of Materials Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn (Estonia); Ernits, K. [crystalsol OÜ, Akadeemia tee 15a, 12618 Tallinn (Estonia); Bleuse, J. [CEA-CNRS-UGA group “Nanophysique et Semiconducteurs”, Univ. Grenoble Alpes, INAC-PHELIQS, CEA, INAC-PHELIQS, CNRS, PLUM, F-38000 Grenoble (France)

    2017-03-01

    In this work we performed time-resolved micro-photoluminescence (TRPL) studies of Cu{sub 2}ZnSnS{sub 4} (CZTS) single crystals grown in molten KI salt. The order/disorder degree of CZTS was varied by the thermal post treatment temperature. Photoluminescence spectra measured at T=8 K showed an asymmetric band with a peak position of 1.33 eV and 1.27 eV for partially ordered and disordered structures, respectively. Thermal activation energies were found to be E{sub T} {sub (PO)} =65±9 meV for partially ordered and E{sub T(PD)} =27±4 meV for partially disordered. These low activation energy values indicating to the defect cluster recombination model for both partially ordered and disordered structures. TRPL was measured for both crystals and their decay curves were fitted with a stretched exponential function, in order to describe the charge carriers’ recombination dynamics at low temperature.

  11. Role of catalysis in sustainable production of synthetic elastomers

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 2 ... Due to limited availability of natural rubber, synthetic elastomers bridge the gap between demand and supply in today's growing tyre and automobile industry. ... The need of synthetic elastomers for tyre and automobile industries is stringently specific.

  12. Stretchable Conductive Elastomers for Soldier Biosensing Applications: Final Report

    Science.gov (United States)

    2016-03-01

    interfacing to the human body to collect brain electroencephalographic (EEG) signals. We present a carbon-nanofiber-filled polydimethylsiloxane...Research Initiative (DRI), stretchable conductors, conductive elastomers, biosensing, electroencephalography, human- machine interface 16. SECURITY...collection system with integrated conductive elastomer electrodes as the human-computer bioelectronic interface . We have engineered a comfortable

  13. An evaluation of Fluorescent elastomer for marking killifish ...

    African Journals Online (AJOL)

    We evaluated the subdermal injection of fluorescent elastomer for tagging two sympatric aplocheilids, Epiplatys bifasciatus and E. spilargyreius, in pond and stream conditions. The smallest size that could be injected without mortality was 28 mm TL. The Visible Implant Elastomer (VIE) tag did not affect the growth or survival ...

  14. Silicone elastomers with covalently incorporated aromatic voltage stabilisers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Skov, Anne Ladegaard

    2017-01-01

    When optimising dielectric elastomers (DEs) a conflict exists, namely that for large achievable actuationstrains softness is required, but with increased softness electrical breakdown strength decreases. Herein,soft dielectric silicone elastomers with increased electrical breakdown strength, due...... forhomogeneity. Concentrations of the voltage stabiliser were varied by changing the molecular weights ofthe PPMS in the copolymer. The developed elastomers were inherently soft with enhanced electricalbreakdown strengths, due to delocalisedp-electrons of the aromatic constituent. An optimumconcentration...... was found for the voltage stabilisation effect. The relative permittivities of thePDMS–PPMS elastomers varied from 3.4 to 3.9 and therefore were also improved from pure PDMSelastomers. The elastomers were furthermore non-conductive and possessed low dielectric losses.These properties are evaluated...

  15. Dielectric elastomer actuators used for pneumatic valve technology

    Science.gov (United States)

    Giousouf, Metin; Kovacs, Gabor

    2013-10-01

    Dielectric elastomer actuators have been investigated for applications in the field of pneumatic automation technology. We have developed different valve designs with stacked dielectric elastomer actuators and with integrated high voltage converters. The actuators were made using VHB-4910 material and a stacker machine for automated fabrication of the cylindrical actuators. Typical characteristics of pneumatic valves such as flow rate, power consumption and dynamic behaviour are presented. For valve construction the force and stroke parameters of the dielectric elastomer actuator have been measured. Further, benefits for valve applications using dielectric elastomers are shown as well as their potential operational area. Finally, challenges are discussed that are relevant for the use of elastomer actuators in valves for industrial applications.

  16. Grain orientation distribution and development of grain line in highly ordered Bi4Si3O12 micro-crystals

    OpenAIRE

    Zhang Z.G.; Wang X.F.; Tian Q.Q.

    2010-01-01

    Bismuth silicate (Bi4Si3O12) micro-crystals with a grain line structure were grown by a sintering method under atmosphere pressure. The as-grown products were studied using Xray diffraction (XRD) and Environmental scanning electron microscopy (ESEM). The grain orientation law was tested by the One-Sample Kolmogorov-Smirnov (K-S) test. The result shows Bi4Si3O12 grains are always distributed in pairs on both sides of a stable line. On one side of a line, the angle between grain orientation and...

  17. Highly flexible and transparent dielectric elastomer actuators using silver nanowire and carbon nanotube hybrid electrodes.

    Science.gov (United States)

    Lee, Ye Rim; Kwon, Hyungho; Lee, Do Hoon; Lee, Byung Yang

    2017-09-27

    We demonstrate a dielectric elastomer actuator (DEA) with a high areal strain value of 146% using hybrid electrodes of silver nanowires (AgNWs) and single-walled carbon nanotubes (SWCNTs). The addition of a very small amount of SWCNTs (∼35 ng mm-2) to a highly resistive AgNW network resulted in a remarkable reduction of the electrode sheet resistance by three orders, increasing the breakdown field by 183% and maximum strain, while maintaining the reduction of optical transmittance within 11%. The DEA based on our transparent and stretchable hybrid electrodes can be easily fabricated by a simple vacuum filtration and transfer process of the electrode film on a pre-strained dielectric elastomer membrane. We expect that our approach will be useful in the future for fabricating stretchable and transparent electrodes in various soft electronic devices.

  18. Tensor order parameters for magnetic-structural phase transitions in crystals with strong spin-lattice coupling

    Science.gov (United States)

    Birman, Joseph L.; Izyumov, Yuri A.

    1980-02-01

    We formulate the thermodynamic theory of phase transitions in magnetically ordered systems in terms of a tensor, or coupled, order parameter. This basis is constructed by coupling atomic spin and lattice displacement. Symmetry lowering is predicted at the second-order phase transition point (tricritical points are not considered here). Lower-symmetry phases should in general be classified according to the Shubnikov symmetry space group Sh, which will reveal the total broken symmetry due to the coupled order parameter. In case the apparatus is "blind" to one portion of the order parameter: either spin or displacement, the apparent symmetry group will not be Sh, but a related space group, which will reveal "partial information." Comparing this formulation and the usual (uncoupled) theory, new results are obtained here: for example "pseudoscalar order parameters" can arise and different "symmetry-broken" groups. An illustration is given by applying the formulation to the spinel-structure space group: O7h-Fd3m. It is conjectured that for TbNi2 the tensor order parameter Γ1- may be relevant, so that the phase transition which has been identified as O7h-->Sh101166 may actually be O7h-->Sh132227, caused by a pseudoscalar.

  19. Monitoring diver kinematics with dielectric elastomer sensors

    Science.gov (United States)

    Walker, Christopher R.; Anderson, Iain A.

    2017-04-01

    Diving, initially motivated for food purposes, is crucial to the oil and gas industry, search and rescue, and is even done recreationally by millions of people. There is a growing need however, to monitor the health and activity of divers. The Divers Alert Network has reported on average 90 fatalities per year since 1980. Furthermore an estimated 1000 divers require recompression treatment for dive-related injuries every year. One means of monitoring diver activity is to integrate strain sensors into a wetsuit. This would provide kinematic information on the diver potentially improving buoyancy control assessment, providing a platform for gesture communication, detecting panic attacks and monitoring diver fatigue. To explore diver kinematic monitoring we have coupled dielectric elastomer sensors to a wetsuit worn by the pilot of a human-powered wet submarine. This provided a unique platform to test the performance and accuracy of dielectric elastomer strain sensors in an underwater application. The aim of this study was to assess the ability of strain sensors to monitor the kinematics of a diver. This study was in collaboration with the University of Auckland's human-powered submarine team, Team Taniwha. The pilot, completely encapsulated in a hull, pedals to propel the submarine forward. Therefore this study focused on leg motion as that is the primary motion of the submarine pilot. Four carbon-filled silicone dielectric elastomer sensors were fabricated and coupled to the pilot's wetsuit. The first two sensors were attached over the knee joints, with the remaining two attached between the pelvis and thigh. The goal was to accurately measure leg joint angles thereby determining the position of each leg relative to the hip. A floating data acquisition unit monitored the sensors and transmitted data packets to a nearby computer for real-time processing. A GoPro Hero 4 silver edition was used to capture the experiments and provide a means of post-validation. The

  20. Ir-192 Plesiocurietherapy using silicone elastomer plates

    Energy Technology Data Exchange (ETDEWEB)

    Michel-Langlet, P.; Housset, M.; Alapetite, C.; Boisserie, G.; Dessard-Diana, B.; Baillet, F.

    1989-01-01

    Corrective treatment of certain superficial lesions (permeation nodules, budding or ulcerated tumor recurrences, etc.) is sometimes difficult and may, in certain cases, benefit from plesiocurietherapy. A device intended for this purpose which is easy to handle, easy to use and inexpensive is presented: it consists of silicone elastomer plates in which are inserted vector plastic tubes which, like any type of curietherapy, can be used with estimated dosimetry and delayed loading (Ir 192). These flexible plates can be adapted to all anatomical variations and very accurately inserted.

  1. Modeling of dielectric elastomer as electromechanical resonator

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bo, E-mail: liboxjtu@mail.xjtu.edu.cn; Liu, Lei; Chen, Hualing; Jia, Shuhai [School of Mechanical Engineering, Xi' an Jiaotong University, 28 Xianning West Road, Xi' an 710049 (China); State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, 28 Xianning West Road, Xi' an 710049 (China); Zhang, Junshi [State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an Jiaotong University, 28 Xianning West Road, Xi' an 710049 (China); School of Aerospace Engineering, Xi' an Jiaotong University, 28 Xianning West Road, Xi' an 710049 (China); Li, Dichen [School of Mechanical Engineering, Xi' an Jiaotong University, 28 Xianning West Road, Xi' an 710049 (China)

    2014-09-28

    Dielectric elastomers (DEs) feature nonlinear dynamics resulting from an electromechanical coupling. Under alternating voltage, the DE resonates with tunable performances. We present an analysis of the nonlinear dynamics of a DE as electromechanical resonator (DEER) configured as a pure shear actuator. A theoretical model is developed to characterize the complex performance under different boundary conditions. Physical mechanisms are presented and discussed. Chaotic behavior is also predicted, illustrating instabilities in the dynamics. The results provide a guide to the design and application of DEER in haptic devices.

  2. Preparation and Characterization of Thermally Reversible Self-healing Polyurethane Elastomer

    Directory of Open Access Journals (Sweden)

    YANG Yi-lin

    2017-08-01

    Full Text Available In order to investigate the structure and property relationships of intrinsic self-healing polyurethane and balance the seemly contradictory forces between its self-healing efficiency and mechanical strength, the reversible disulfide bonds were introduced into polyester-polyurethane by taking hexamethylene diisocyanate (HDI trimers as the cross-linker and 4,4-diamino diphenyl disulfide as the chain-extender. The results show that the optimal self-healing elastomer exhibits a tensile strength of 7.7MPa and a maximum self-healing efficiency of 97.4% at 60℃after 24 hours, whereas the common elastomer synthesized without disulfide bonds (via H-bonding interactions only exhibits a tensile strength of 9.3MPa and a maximum self-healing efficiency of 58.0% under the same condition, indicating that the existence of disulfide bonds helps to increase the self-healing efficiency by 67.9%. The prepared elastomer is found to have multi time self-healing capabilities and the second time self-healing efficiency is 62.3%.

  3. Crystal structure of a small heat-shock protein from Xylella fastidiosa reveals a distinct high-order structure.

    Science.gov (United States)

    Fonseca, Emanuella Maria Barreto; Scorsato, Valéria; Dos Santos, Marcelo Leite; Júnior, Atilio Tomazini; Tada, Susely Ferraz Siqueira; Dos Santos, Clelton Aparecido; de Toledo, Marcelo Augusto Szymanski; de Souza, Anete Pereira; Polikarpov, Igor; Aparicio, Ricardo

    2017-04-01

    Citrus variegated chlorosis is a disease that attacks economically important citrus plantations and is caused by the plant-pathogenic bacterium Xylella fastidiosa. In this work, the structure of a small heat-shock protein from X. fastidiosa (XfsHSP17.9) is reported. The high-order structures of small heat-shock proteins from other organisms are arranged in the forms of double-disc, hollow-sphere or spherical assemblies. Unexpectedly, the structure reported here reveals a high-order architecture forming a nearly square cavity.

  4. Orientational order of near D(3h) solutes in nematic liquid crystals. II. Description via Gay-Berne model with embedded quadrupoles.

    Science.gov (United States)

    Sokolovskii, R O; Burnell, E Elliott

    2009-04-21

    We perform Monte Carlo simulations of a mixture of soft ellipsoids with embedded quadrupoles as a model of various chloro- and methyl-substituted benzenes dissolved in nematic liquid crystals. We find that oblate Gay-Berne ellipsoids with multiple embedded quadrupoles qualitatively reproduce the trend in the order parameter asymmetry experimentally observed in NMR spectra. The trend is opposite to what is expected on the basis of the interaction of the solute's quadrupole with the solvent's average electric field gradient "felt" by dissolved dihydrogen molecules. We identify the specific minimum of the solute-solvent interaction energy landscape that may produce the unexpected sign of the order parameter asymmetry that is seen in the experiment and the simulation.

  5. Flux Synthesis, Crystal Structures, and Magnetic Ordering of the Rare-Earth Chromium(II) Oxyselenides RE2CrSe2O2 (RE = La-Nd).

    Science.gov (United States)

    Peschke, Simon; Weippert, Valentin; Senyshyn, Anatoliy; Mühlbauer, Martin Johann; Janka, Oliver; Pöttgen, Rainer; Holenstein, Stefan; Luetkens, Hubertus; Johrendt, Dirk

    2017-02-20

    The rare-earth chromium(II) oxyselenides RE2CrSe2O2 (RE = La-Nd) were synthesized in eutectic NaI/KI fluxes, and their crystal structures were determined by single-crystal and powder X-ray diffraction (Pb2HgCl2O2-type, C2/m, Z = 2). The magnetic structure of La2CrSe2O2 was solved and refined from neutron powder diffraction data. Main building blocks are chains of edge-sharing CrSe4O2 octahedra linked together by two edge-sharing ORE3Cr tetrahedra forming infinite ribbons. The Jahn-Teller instability of divalent Cr(2+) (d(4)) leads to structural phase transitions at 200 and 130 K in La2CrSe2O2 and Ce2CrSe2O2, respectively. RE2CrSe2O2 are Curie-Weiss paramagnetic above TN ≈ 14-17 K. Neutron powder diffraction reveals anti-ferromagnetic ordering of the Cr(2+) moments in La2CrSe2O2 below TN = 12.7(3) K with an average ordered moment of 3.40(4) μB/Cr(2+) at 4 K, which was confirmed by muon spin rotation experiments.

  6. Non Linear Viscoelastic Constitutive Relation of Elastomers for Hysteresis Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Sairom; Kim, Dooman [Korea Aerospace Univ., Goyang (Korea, Republic of); Ju, Jaehyung [Univ. of North Texas, Houston (United States); Choi, Seok-Ju [R and Center, Hnakook Tire Co. Ltd., Daejeon (Korea, Republic of)

    2016-04-15

    An accurate hysteresis model of an elastomer is important for quantifying viscoelastic energy loss. We suggest a highly nonlinear hyper-viscoelastic constitutive model of elastomers. The model captures a nonlinear viscoelastic characteristic by combining Yeoh's hyperelastic model and Hoofatt's hysteresis model used Neo-Hookean hyperelastic model. Analytical and numerical models were generated from uniaxial cyclic tests of an elastomer under a sinusoidal load with a mean strain of 150%, amplitudes of 20-80%, and frequencies of 0.02-0.2Hz. The viscoelastic model can highly capture the viscoelastic energy loss up to a strain of 230%.

  7. Active vibration isolation platform on base of magnetorheological elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailov, Valery P., E-mail: mikhailov@bmstu.ru; Bazinenkov, Alexey M.

    2017-06-01

    The article describes the active vibration isolation platform on base of magnetorheological (MR) elastomers. An active damper based on the MR elastomers can be used as an actuator of micro- or nanopositioning for a vibroinsulated object. The MR elastomers give such advantages for active control of vibration as large range of displacements (up to 1 mm), more efficient absorption of the vibration energy, possibility of active control of amplitude-frequency characteristics and positioning with millisecond response speed and nanometer running accuracy. The article presents the results of experimental studies of the most important active damper parameters. Those are starting current, transient time for stepping, transmission coefficient of the vibration displacement amplitude.

  8. Self-Healing, High-Permittivity Silicone Dielectric Elastomer

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Skov, Anne Ladegaard

    2016-01-01

    Currently used dielectric elastomers do not have the ability to self-heal after detrimental events such as tearing or electrical breakdown, which are critical issues in relation to product reliability and lifetime. In this paper, we present a self-healing dielectric elastomer that additionally...... possesses high dielectric permittivity and consists of an interpenetrating polymer network of silicone elastomer and ionic silicone species that are cross-linked through proton exchange between amines and acids. The ionically cross-linked silicone provides self-healing properties after electrical breakdown...

  9. The dielectric breakdown limit of silicone dielectric elastomer actuators

    Science.gov (United States)

    Gatti, Davide; Haus, Henry; Matysek, Marc; Frohnapfel, Bettina; Tropea, Cameron; Schlaak, Helmut F.

    2014-02-01

    Soft silicone elastomers are used in a generation of dielectric elastomer actuators (DEAs) with improved actuation speed and durability compared to the commonly used, highly viscoelastic polyacrylate 3M VHB™ films. The maximum voltage-induced stretch of DEAs is ultimately limited by their dielectric breakdown field strength. We measure the dependence of dielectric breakdown field strength on thickness and stretch for a silicone elastomer, when voltage-induced deformation is prevented. The experimental results are combined with an analytic model of equi-biaxial actuation to show that accounting for variable dielectric field strength results in different values of optimal pre-stretch and thickness that maximize the DEA actuation.

  10. Suppression of electromechanical instability in fiber-reinforced dielectric elastomers

    Directory of Open Access Journals (Sweden)

    Rui Xiao

    2016-03-01

    Full Text Available The electromechanical instability of dielectric elastomers has been a major challenge for the application of this class of active materials. In this work, we demonstrate that dielectric elastomers filled with soft fiber can suppress the electromechanical instability and achieve large deformation. Specifically, we developed a constitutive model to describe the dielectric and mechanical behaviors of fiber-reinforced elastomers. The model was applied to study the influence of stiffness, nonlinearity properties and the distribution of fiber on the instability of dielectric membrane under an electric field. The results show that there exists an optimal fiber distribution condition to achieve the maximum deformation before failure.

  11. Lifetime of dielectric elastomer stack actuators

    Science.gov (United States)

    Lotz, Peter; Matysek, Marc; Schlaak, Helmut F.

    2011-04-01

    Dielectric elastomer stack actuators (DESA) are well suited for the use in mobile devices, fluidic applications and small electromechanical systems. Despite many improvements during the last years the long term behavior of dielectric elastomer actuators in general is not known or has not been published. The first goal of the study is to characterize the overall lifetime under laboratory conditions and to identify potential factors influencing lifetime. For this we have designed a test setup to examine 16 actuators at once. The actuators are subdivided into 4 groups each with a separate power supply and driving signal. To monitor the performance of the actuators driving voltage and current are measured continuously and additionally, the amplitude of the deformations of each actuator is measured sequentially. From our first results we conclude that lifetime of these actuators is mainly influenced by the contact material between feeding line and multilayer electrodes. So far, actuators themselves are not affected by long term actuation. With the best contact material actuators can be driven for more than 2700 h at 200 Hz with an electrical field strength of 20 V/μm. This results in more than 3 billion cycles. Actually, there are further actuators driven at 10 Hz for more than 4000 hours and still working.

  12. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  13. Stress measurements of planar dielectric elastomer actuators

    Energy Technology Data Exchange (ETDEWEB)

    Osmani, Bekim; Aeby, Elise A.; Müller, Bert [Biomaterials Science Center, University of Basel, Gewerbestrasse 14, 4123 Allschwil (Switzerland)

    2016-05-15

    Dielectric elastomer actuator (DEA) micro- and nano-structures are referred to artificial muscles because of their specific continuous power and adequate time response. The bending measurement of an asymmetric, planar DEA is described. The asymmetric cantilevers consist of 1 or 5 μm-thin DEAs deposited on polyethylene naphthalate (PEN) substrates 16, 25, 38, or 50 μm thick. The application of a voltage to the DEA electrodes generates an electrostatic pressure in the sandwiched silicone elastomer layer, which causes the underlying PEN substrate to bend. Optical beam deflection enables the detection of the bending angle vs. applied voltage. Bending radii as large as 850 m were reproducibly detected. DEA tests with electric fields of up to 80 V/μm showed limitations in electrode’s conductivity and structure failures. The actuation measurement is essential for the quantitative characterization of nanometer-thin, low-voltage, single- and multi-layer DEAs, as foreseen for artificial sphincters to efficiently treat severe urinary and fecal incontinence.

  14. Soft Dielectric Elastomer Oscillators Driving Bioinspired Robots.

    Science.gov (United States)

    Henke, E-F Markus; Schlatter, Samuel; Anderson, Iain A

    2017-12-01

    Entirely soft robots with animal-like behavior and integrated artificial nervous systems will open up totally new perspectives and applications. To produce them, we must integrate control and actuation in the same soft structure. Soft actuators (e.g., pneumatic and hydraulic) exist but electronics are hard and stiff and remotely located. We present novel soft, electronics-free dielectric elastomer oscillators, which are able to drive bioinspired robots. As a demonstrator, we present a robot that mimics the crawling motion of the caterpillar, with an integrated artificial nervous system, soft actuators and without any conventional stiff electronic parts. Supplied with an external DC voltage, the robot autonomously generates all signals that are necessary to drive its dielectric elastomer actuators, and it translates an in-plane electromechanical oscillation into a crawling locomotion movement. Therefore, all functional and supporting parts are made of polymer materials and carbon. Besides the basic design of this first electronic-free, biomimetic robot, we present prospects to control the general behavior of such robots. The absence of conventional stiff electronics and the exclusive use of polymeric materials will provide a large step toward real animal-like robots, compliant human machine interfaces, and a new class of distributed, neuron-like internal control for robotic systems.

  15. Designing amphotropic smectic liquid crystals based on phosphonium salts for partial ordering of solutes as monitored by NMR spectroscopy.

    Science.gov (United States)

    Shahkhatuni, Astghik A; Ma, Kefeng; Weiss, Richard G

    2009-04-02

    The ordering parameters of selected solutes from NMR spectroscopic measurements have been assessed in the thermotropic and amphotropic smectic liquid-crystalline phases of a wide structural range of phosphonium salts with three equivalent long n-alkyl chains, one shorter chain, and various anions. The nature of the added liquids that convert the salts to amphotropic phasesalcohols and other small organic moleculesand their concentrations have been determined. These factors are correlated with the NMR-derived parameters in order to understand how the phases can be optimized to maximize information about the solutes. The various salts cover a range of liquid crystallinity from -40 to 100 degrees C. The phosphonium salts are easily aligned in the strong magnetic fields of the spectrometers. In several of the systems, a coexistence of isotropic and anisotropic phases is observed over a wide range of temperatures. The order parameters of the amphotropic liquid-crystalline phases vary from high to very low values, and some of the systems provide good spectral resolution for the solute molecules. Also, structural and orientational parameters of a model molecule, (13)C-enriched acetonitrile, have been calculated in various systems in order to evaluate more precisely the applicability of the host systems for determining solute structures by NMR. The results, in toto, indicate that several of the phosphonium salts are very promising as hosts to determine solute structures.

  16. Synthesis and Characterization of Magnetic Elastomer based PEG-Coated Fe3O4 from Natural Iron Sand

    Science.gov (United States)

    Kurniawan, C.; Eko, A. S.; Ayu, Y. S.; Sihite, P. T. A.; Ginting, M.; Simamora, P.; Sebayang, P.

    2017-05-01

    Magnetic elastomer nanocomposite based PEG-coated Fe3O4 with silicone rubber binder have been prepared from natural iron-sand by using coprecipitation method. The samples were characterized by using X-ray Diffractometer, X-ray Fluorescence, Fourier Transform Infra-Red, tensile strength test, and Vibrating Sample Magnetometer to analyze the physical and magnetic properties. We observed that all samples were formed by single phase cubic spinel magnetite (Fe3O4) crystalline structure. The atomic bonding analysis by FTIR showed that the C-O-C and C-H ordering were understood as the PEG - Fe3O4 bonding characteristics. We have observed that the Young modulus of elastomer based PEG-coated Fe3O4 slightly decreased compared to the natural iron-sand based elastomer. The magnetic properties of PEG-coated Fe3O4 were known to be magnetically softer with the lowest coercivity without losing its magnetization saturation value. We propose that the PEG-coated Fe3O4 is a promising candidate to be applied as magnetorheological elastomer due to a good mechanical and magnetic characteristic and also promising as microwave absorbing materials.

  17. Doping effect of L-cystine on structural, UV-visible, SHG efficiency, third order nonlinear optical, laser damage threshold and surface properties of cadmium thiourea acetate single crystal

    Science.gov (United States)

    Azhar, S. M.; Anis, Mohd; Hussaini, S. S.; Kalainathan, S.; Shirsat, M. D.; Rabbani, G.

    2017-01-01

    The present article is focused to investigate the influence of L-cystine (LC) on linear-non-linear optical and laser damage threshold of cadmium thiourea acetate (CTA) crystal. The structural parameters of pure and LC doped CTA crystals have been determined using the single crystal X-ray diffraction technique. The functional groups of grown crystals have been identified by means of fourier transform infrared (FT-IR) analysis. The UV-visible spectral analysis has been done in the range of 200-900 nm to ascertain the uplifting influence of LC on optical properties of CTA crystal. The second harmonic generation (SHG) efficiency of LC doped CTA crystal is found to be higher than CTA and KDP crystal. The Z-scan technique has been employed to determine the third order nonlinear optical (TONLO) nature of LC doped CTA crystal at 632.8 nm. The self focusing tendency confirmed the strong kerr lensing ability of LC doped CTA crystal. The TONLO susceptibility (χ3), refraction (n2) and absorption coefficient (β) has been calculated using the Z-scan data. The laser damage threshold of pure and LC doped CTA crystals has been measured using the Q-switched Nd:YAG laser and its is found to be in range of GW/cm2. The surface analysis has been done by means of etching studies.

  18. Synthesis, crystal structure, and properties of the ordered double perovskite Sr{sub 2}CoOsO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Kumar Paul, Avijit [Max-Planck-Institut fuer Festkoerperforschung, 70569 Stuttgart (Germany); Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany); Reehuis, Manfred [Helmholtz-Zentrum fuer Materialien und Energie, 14109 Berlin (Germany); Felser, Claudia [Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany); Abdala, Paula M. [SNBL, ESRF, BP 220, 38042 Grenoble Cedex 9 (France); Jansen, Martin [Max-Planck-Institut fuer Festkoerperforschung, 70569 Stuttgart (Germany)

    2013-07-01

    Sr{sub 2}CoOsO{sub 6}, a new osmium based ordered semiconductor double perovskite was prepared by solid state synthesis from the respective binary oxides. Room temperature PXRD analysis shows the compound to be tetragonal [I4/m; a = 5.5503(1) Aa and c = 7.9320(1) Aa], whereas low temperature synchrotron data refinement has revealed a second monoclinic polymorph [I2/m; a = 5.4969(2) Aa, b = 5.4979(2) Aa, c = 8.0090(1) Aa and γ = 90.527(1) ] with a fully ordered rocksalt arrangement of cobalt and osmium atoms over the perovskite B-sites. Heat capacity and magnetic measurements indicate that Sr{sub 2}CoOsO{sub 6} shows antiferromagnetic ordering below T{sub N} = 108 K followed by a second magnetic transition at T{sub 2} = 65 K. It was shown that the change from the tetragonal to the monoclinic phase occurs at T{sub N}. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Magnetochemistry of the tetrahaloferrate (III) ions: Crystal structure and magnetic ordering in [(4-chloropyridinium)FeCl4]2ṡ4-chloropyridinium chloride and related salts (abstract)

    Science.gov (United States)

    Lowe, C. B.; Shum, D. P.; Carlin, Richard L.

    1990-05-01

    The yellow compound of stoichiometry (4-chloropyridinium)3Fe2Cl9 belongs to the space group P21/n with four formula units in the unit cell. Structural analysis shows that the iron is present as the FeX4- ion. Magnetic measurements on single crystals show that the material orders as a canted antiferromagnet at 2.725 K. Replacement of the 4-chloro cation by the 4-bromo analog yields an isomorphous material and shifts the transition temperature to 2.34 K. The phase diagrams of both salts have also been determined. For [(4-chloropyridinium)FeCl4]2ṡ4-chloropyridinium chloride, the bicritical point is at 2.40 K and 7 kOe, and HSF(0)=5.5 kOe. With Hc(0)=56 kOe, α=HA/HE=1.9×10-2. In the case of [(4-bromopyridinium)FeCl4]2ṡ4-bromopyridinium chloride, HSF(0)=3 kOe, Hc(0)=42 kOe, α=1.0×10-2, and the bicritical point is at 2.24 K and 4.2 kOe. Crystallographic investigations at 25 K are reported on the isomorphous (4-chloropyridinium)3Fe2Br9 and on (4-bromopyridinium)3Fe2Cl1.3Br7.7. Magnetic measurements on single crystals show that (4-bromopyridinium)3Fe2Cl1.3Br7.7 orders as a canted antiferromagnet at 5.67 K, while (4-chloropyridinium)3Fe2Br9 orders similarly at 7.96 K. These compounds behave approximately as S=5/2, three-dimensional Heisenberg antiferromagnets.

  20. Functional silicone elastomers via novel siloxane copolymers and chain extenders

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    Functional silicone polymers and elastomers with altered/improved bulk and/or surface properties are highly desired to expand the application range even further. Novel functional silicone polymers and elastomers were prepared via two different methods. One method was through the synthesis......, as several parameters can be varied during the preparation phase. As an example, the space between the functional groups can be varied, by using different dimethylsiloxane spacer units between the functional molecules. Furthermore, the degree of functionalisation of the copolymers can be varied accurately...... by changing the feed of functional molecules. As a result, a completely tuneable elastomer system, with respect to functionalisation, is achieved. The second method of functionalising silicone elastomers involves the synthesis of a so-called ‘chain extender’ that allows for chemical modifications such as Cu...

  1. Mechanical modeling of interpenetrating polymer network reinforced acrylic elastomer

    Science.gov (United States)

    Schmidt, Arne; Bergamini, Andrea; Kovacs, Gabor; Mazza, Edoardo

    2010-04-01

    Interpenetrating polymer network reinforced acrylic elastomers (IPN) offer outstanding performance in free-standing contractile dielectric elastomer actuators. This work presents the verification of a recently proposed material model for a VHB 4910 based IPN [1]. The 3D large strain material model was determined from extensive data of multiaxial mechanical experiments and allows to account for the variations in material composition of IPN-membranes. We employed inflation tests to membranes of different material composition to study the materials response in a stress state different from the one that was used to extract the material parameters. By applying the material model to finite element models we successfully validated the material model in a range of material compositions typically used for dielectric elastomer actuator applications. In combination with a characterization of electro-mechanical coupling, this 3D large strain model can be used to model IPN-based dielectric elastomer actuators.

  2. Molecular recognition in poly(epsilon-caprolactone)-based thermoplastic elastomers

    NARCIS (Netherlands)

    Wisse, Eva; Spiering, A. J. H.; van Leeuwen, Ellen N. M.; Renken, Raymond A. E.; Dankers, Patricia Y. W.; Brouwer, Linda A.; van Luyn, Marja J. A.; Harmsen, Martin C.; Sommerdijk, Nico A. J. M.; Meijer, E. W.

    2006-01-01

    The molecular recognition properties of the hydrogen bonding segments in biodegradable thermoplastic elastomers were explored, aiming at the further functionalization of these potentially interesting biomaterials. A poly(epsilon-caprolactone)-based poly(urea) 2 was synthesized and characterized in

  3. 21 CFR 177.2400 - Perfluorocarbon cured elastomers.

    Science.gov (United States)

    2010-04-01

    ... components of articles intended for repeated use in contact with nonacid food (pH above 5.0), subject to the..._locations.html. (2) Thermogravimetry. Perfluorocarbon cured elastomers have a major decomposition peak...

  4. Atomic scale studies of La/Sr ordering in La2-2xSr1+2xMn2O7 single crystals

    KAUST Repository

    Roldan, Manuel

    2016-12-21

    Many fascinating properties of materials depend strongly on the local chemical environment. This is the case for many complex oxides, such as materials with colossal magnetoresistance, where small variations of composition at the atomic scale can affect drastically the macroscopic properties. The main objective of the present work is to analyze the local chemical composition with atomic resolution and to find out if any underlying chemical order is in any way connected to the magnetic properties of double perovskite La2-2xSr1+2xMn2O7 (LSMO) manganite oxides. For these compounds, charge and orbital ordering are observed for some doping values near x = 0.50 [1, 2]. For this purpose, we have use aberration corrected scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) measurements and also theoretical simulations. We have compared different compositions within three distinct magnetic regions of the phase diagram: a ferromagnetic metallic sample with x=0.36, an insulating, antiferromagnetic (AF) x=0.56 and an additional AF x=0.50 sample which also exhibits charge ordering. High angle annular dark-field (HAADF) images, also known as Z-contrast, confirm that our single crystals exhibit high crystal quality. No secondary phases or defects are observed. Figure 1 displays an atomic resolution image obtained with the c-axis perpendicular to the electron beam of a x=0.50 sample. The perovskite (P)-like planes and the rock salt (R)-like planes are clearly observed, highlighted in green and red, respectively, on the image. The P-like planes exhibit a slightly high contrast, suggesting a possible La enrichment. EELS atomic resolution maps (inset) support a high degree of La segregation on those planes, while R-like planes are Sr rich. However, due to dechanneling of the beam, detailed image simulations are essential to accurately quantify the local chemical composition in an atomic column-by-atomic column fashion. For all our

  5. Frictional behaviour of some sealing elastomers in lubricated sliding

    OpenAIRE

    M Mofidi; Prakash, Braham

    2012-01-01

    Frictional behaviour of four sealing elastomers, including an acrylonitrile butadienerubber (NBR), a hydrogenated acrylonitrile butadiene rubber (HNBR), an acrylate rubber(ACM) and a fluoroelastomer (FKM), sliding against a steel surface under unidirectionallubricated conditions have been studied. The lubricant used in this study was paraffinic oilwith no additive and the experiments were conducted under a block-on-ring testconfiguration. The friction coefficients of the elastomers have been ...

  6. Silicone elastomers with superior softness and dielectric properties

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin

    ’s modulus and increasing the dielectric permittivity of silicone elastomers. One such prominent method of modifying the properties is by adding suitable additives.[1] The major drawbacks for adding solid fillers are agglomeration and increasing stiffness which is often accompanied by the decrease...... were determined by NMR and morphology structures were investigated by optical microscopy. The resulting elastomers were evaluated with respect to their dielectric permittivity, viscoelasticity and tensile strengths, as well as electrical breakdown....

  7. 4-N, N-bis(4-methoxylphenyl) aniline substituted anthraquinone: X-ray crystal structures, theoretical calculations and third-order nonlinear optical properties

    Science.gov (United States)

    Xu, Liang; Zhang, Dingfeng; Zhou, Yecheng; Zheng, Yusen; Cao, Liu; Jiang, Xiao-Fang; Lu, Fushen

    2017-08-01

    In this paper, mono- and di-4-N,N-bis(4-methoxylphenyl)aniline-substituted anthraquinone have been designed and synthesized through Suzuki reaction. For mono-4-N,N-bis(4-methoxylphenyl)aniline-substituted anthraquinone, polymorphous crystal structures have been obtained in different crystallization conditions. Electrochemical characterization combined with theoretical calculation suggests that the addition of a second triphenylamine unit causes a larger band gap with higher lying LUMO (Lowest Unoccupied Molecular Orbital) and HOMO (Highest Occupied Molecular Orbital). The linear optical property shows that the introduction of a second triphenylamine unit bring about a significant hyperchromic effect with the extinction coefficients increasing from 11199 M-1 cm-1 to 22136 M-1 cm-1. The third-order nonlinear optical properties indicate that the introduction of a second triphenylamine unit lead to a much larger nonlinear absorption coefficient and two-photon absorption cross section, with the relevant value increasing from 2.04 × 10-12 cm W-1 to 3.91 × 10-12 cm W-1, and from 148 GM to 286 GM, respectively.

  8. First Order Temperature Dependent Phase Transition in a Monoclinic Polymorph Crystal of 1,6-Hexanedioic Acid: An Interpretation Based on the Landau Theory Approach

    Directory of Open Access Journals (Sweden)

    Hoong-Kun Fun

    2014-07-01

    Full Text Available Crystals of 1,6-hexanedioic acid (I undergo a temperature-dependent reversible phase transition from monoclinic P21/c at a temperature higher than the critical temperature (Tc 130 K to another monoclinic P21/c at temperature lower than Tc. The phase transition is of first order, involving a discontinuity and a tripling of the b-axis at Tc whereas the other unit cell parameters vary continuously. The transition is described by the phenomenological Landau theory. The crystal structure analyses for data collected at 297(2 K and 120.0(1 K show that there is half of a molecule of (I in the asymmetric unit at 297(2 K whereas there are one and a half molecules of (I in the asymmetric unit at 120.0(1 K. At both temperatures, 297(2 and 120.0(1 K, intermolecular O-H···O hydrogen bonds link the molecules of I into infinite 1D chains along [101] direction. However there are significantly more O-H···O hydrogen bonds presented in the 120.0(1 K polymorph, thereby indicating this phase transition is negotiated via hydrogen bonds. The relationship of the conformational changes and hydrogen bonding for these two polymorphs are explained in detail.

  9. Treatment to Control Adhesion of Silicone-Based Elastomers

    Science.gov (United States)

    deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

    2013-01-01

    Seals are used to facilitate the joining of two items, usually temporarily. At some point in the future, it is expected that the items will need to be separated. This innovation enables control of the adhesive properties of silicone-based elastomers. The innovation may also be effective on elastomers other than the silicone-based ones. A technique has been discovered that decreases the level of adhesion of silicone- based elastomers to negligible levels. The new technique causes less damage to the material compared to alternative adhesion mitigation techniques. Silicone-based elastomers are the only class of rubber-like materials that currently meet NASA s needs for various seal applications. However, silicone-based elastomers have natural inherent adhesive properties. This stickiness can be helpful, but it can frequently cause problems as well, such as when trying to get items apart. In the past, seal adhesion was not always adequately addressed, and has caused in-flight failures where seals were actually pulled from their grooves, preventing subsequent spacecraft docking until the seal was physically removed from the flange via an extravehicular activity (EVA). The primary method used in the past to lower elastomer seal adhesion has been the application of some type of lubricant or grease to the surface of the seal. A newer method uses ultraviolet (UV) radiation a mixture of UV wavelengths in the range of near ultraviolet (NUV) and vacuum ultraviolet (VUV) wavelengths.

  10. Mechanical and morphological characterization of polypropylene toughened with olefinic elastomer

    Directory of Open Access Journals (Sweden)

    Lotti Cybele

    2000-01-01

    Full Text Available The effect of incorporating (C2-C8 ethylene-octene elastomer on the mechanical properties and morphology of polypropylene copolymers has been investigated employing two types of PP copolymer, with and without nucleating agent. The results were compared to the ones presented by a commercial PP heterophase (reactor impact modified PP/EPR. The addition of the elastomer increases the toughness of the blends but reduces their stiffness. PP blends in the low elastomer content region (< 20% show low values of the Izod impact strength and both, elastomer content and impact strength, are directly proportional to the area under the beta damping peak or its maximum intensity of the elastomer. The morphology is a continuous pattern of segregate elastomeric particles with average particle size in the range of 0.27 mum to 0.39 mum. The average particle size and particle size distribution plotted in log-normal distribution curves, increases slightly with the increase in the elastomer content. The reactor modified PP heterophase has a broader particle size distribution and an average particle size of 0.56 mum, at the lower limit but inside the range for good impact performance, as observed.

  11. Arrayed Force Sensors Made of Paper, Elastomer, and Hydrogel Particles

    Directory of Open Access Journals (Sweden)

    Xiyue Zou

    2017-12-01

    Full Text Available This article presents a sensor for detecting the distribution of forces on a surface. The device with nine buttons consisted of an elastomer-based layer as a touch interface resting on a substrate of patterned metallized paper. The elastomer-based layer included a three-by-three array of deformable, hemispherical elements/reliefs, facing down toward an array of interdigitated capacitive sensing units on patterned metallized paper. Each hemispherical element is 20 mm in diameter and 8 mm in height. When a user applied pressure to the elastomer-based layer, the contact area between the hemispherical elements and the interdigitated capacitive sensing units increased with the deformation of the hemispherical elements. To enhance the sensitivity of the sensors, embedded particles of hydrogel in the elastomer-based layer increased the measured electrical responses. The measured capacitance increased because the effective dielectric permittivity of the hydrogel was greater than that of air. Electromechanical characterization verified that the hydrogel-filled elastomer was more sensitive to force at a low range of loads (23.4 pF/N than elastomer alone without embedded hydrogel (3.4 pF/N, as the hydrogel reduced the effective elastic modulus of the composite material by a factor of seven. A simple demonstration suggests that the force-sensing array has the potential to contribute to wearable and soft robotic devices.

  12. Polyurethane elastomers from morphology to mechanical aspects

    CERN Document Server

    Prisacariu, Cristina

    2011-01-01

    A comprehensive account of the physical / mechanical behaviour of polyurethanes (PU´s) elastomers, films and blends of variable crystallinity. Aspects covered include the elasticity and inelasticity of amorphous to crystalline PUs, in relation to their sensitivity to chemical and physical structure. A study is made of how aspects of the constitutive responses of PUs vary with composition: the polyaddition procedure, the hard segment, soft segment and chain extender (diols and diamines) are varied systematically in a large number of systems of model and novel crosslinked andthermoplastic PUs. Results will be related to: microstructural changes, on the basis of evidence from x-ray scattering (SAXS and WAXS), and also dynamic mechanical analyses (DMA), differential scanning calorimetry (DSC) and IR dichroism. Inelastic effects will be investigated also by including quantitative correlations between the magnitude of the Mullins effect and the fractional energy dissipation by hysteresis under cyclic straining, g...

  13. Microfabrication of stacked dielectric elastomer actuator fibers

    Science.gov (United States)

    Corbaci, Mert; Walter, Wayne; Lamkin-Kennard, Kathleen

    2016-04-01

    Dielectric elastomer actuators (DEA) are one of the best candidate materials for next generation of robotic actuators, soft sensors and artificial muscles due to their fast response, mechanical robustness and compliance. However, high voltage requirements of DEAs have impeded their potential to become widely used in such applications. In this study, we propose a method for fabrication of silicon based multilayer DEA fibers composed of microlevel dielectric layers to improve the actuation ratios of DEAs at lower voltages. A multi-walled carbon nanotube - polydimethylsiloxane (MWCNT/PDMS) composite was used to fabricate mechanically compliant, conductive parallel plates and electrode connections for the DEA actuators. Active surface area and layer thickness were varied to study the effects of these parameters on actuation ratio as a function of applied voltage. Different structures were fabricated to assess the flexibility of the fabrication method for specific user-end applications.

  14. A Recipe for Soft Fluidic Elastomer Robots

    Science.gov (United States)

    Marchese, Andrew D.; Katzschmann, Robert K.

    2015-01-01

    Abstract This work provides approaches to designing and fabricating soft fluidic elastomer robots. That is, three viable actuator morphologies composed entirely from soft silicone rubber are explored, and these morphologies are differentiated by their internal channel structure, namely, ribbed, cylindrical, and pleated. Additionally, three distinct casting-based fabrication processes are explored: lamination-based casting, retractable-pin-based casting, and lost-wax-based casting. Furthermore, two ways of fabricating a multiple DOF robot are explored: casting the complete robot as a whole and casting single degree of freedom (DOF) segments with subsequent concatenation. We experimentally validate each soft actuator morphology and fabrication process by creating multiple physical soft robot prototypes. PMID:27625913

  15. Tactile display with dielectric multilayer elastomer actuatorsq

    Science.gov (United States)

    Matysek, Marc; Lotz, Peter; Schlaak, Helmut F.

    2009-03-01

    Tactile perception is the human sensation of surface textures through the vibrations generated by stroking a finger over the surface. The skin responds to several distributed physical quantities. Perhaps the most important are high-frequency vibrations, pressure distributions (static shape) and thermal properties. The integration of tactile displays in man-machine interfaces promises a more intuitive handling. For this reason many tactile displays are developed using different technologies. We present several state-of-the-art tactile displays based on different types of dielectric elastomer actuators to clarify the advantages of our matrix display based on multilayer technology. Using this technology perpendicular and hexagonal arrays of actuator elements (tactile stimulators) can be integrated into a PDMS substrate. Element diameters down to 1 mm allow stimuli at the range of the human two-point-discrimination threshold. Driving the elements by column and row addressing enables various stimulation patterns with a reduced number of feeding lines. The transient analysis determines charging times of the capacitive actuators depending on actuator geometry and material parameters. This is very important to ensure an adequate dynamic characteristic of the actuators to stimulate the human skin by vibrations. The suitability of multilayer dielectric elastomer actuators for actuation in tactile displays has been determined. Beside the realization of a static tactile display - where multilayer DEA are integrated as drives for movable contact pins - we focus on the direct use of DEA as a vibrotactile display. Finally, we present the scenario and achieved results of a recognition threshold test. Even relative low voltages in the range of 800 V generate vibrations with 100% recognition ratio within the group of participants. Furthermore, the frequency dependent characteristic of the determined recognition threshold confirms with established literature.

  16. Synthesis, crystal structure and magnetic properties of a new B-site ordered double perovskite Sr{sub 2}CuIrO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Vasala, Sami; Yamauchi, Hisao; Karppinen, Maarit, E-mail: maarit.karppinen@aalto.fi

    2014-12-15

    Here we synthesize and characterize a new double-perovskite oxide Sr{sub 2}CuIrO{sub 6}. The synthesis requires the use of high oxygen pressure to stabilize the VI oxidation state of iridium. The compound has a tetragonally-distorted crystal structure due to the Jahn–Teller active Cu{sup II} ion, and a high degree of B-site cation order. Magnetic transition is apparent at 15 K, but the zero-field-cooled and field-cooled susceptibilities diverge below this temperature. The high degree of cation order would exclude the possibility of a typical spin-glass, indicating that the divergence is probably due to a frustration of the magnetic interactions between Cu and Ir, with a high frustration factor of f≈25. - Graphical abstract: A new member of the A{sub 2}B′B″O{sub 6} double-perovskite family with JT-active Cu{sup II} at the B′ site and Ir{sup VI} at the B″ site is synthesized through high pressure synthesis and characterized for the structural and magnetic properties. - Highlights: • New member of the A{sub 2}CuB″O{sub 6} double-perovskite family is synthesized with B″=Ir. • Stabilization of Ir{sup VI} requires the use of high oxygen pressure synthesis. • Crystal structure is tetragonally distorted due to JT-active Cu{sup II}. • Divergence of ZFC and FC curves is seen below the T{sub N} of 15 K. • This is presumably due to a frustration effect.

  17. Orientational order parameters of a de Vries-type ferroelectric liquid crystal obtained by polarized Raman spectroscopy and x-ray diffraction.

    Science.gov (United States)

    Sanchez-Castillo, A; Osipov, M A; Jagiella, S; Nguyen, Z H; Kašpar, M; Hamplovă, V; Maclennan, J; Giesselmann, F

    2012-06-01

    The orientational order parameters (P{2}) and (P{4}) of the ferroelectric, de Vries-type liquid crystal 9HL have been determined in the SmA and SmC phases by means of polarized Raman spectroscopy, and in the SmA phase using x-ray diffraction. Quantum density functional theory predicts Raman spectra for 9HL that are in good agreement with the observations and indicates that the strong Raman band probed in the experiment corresponds to the uniaxial, coupled vibration of the three phenyl rings along the molecular long axis. The magnitudes of the orientational order parameters obtained in the Raman and x-ray experiments differ dramatically from each other, a discrepancy that is resolved by considering that the two techniques probe the orientational distributions of different molecular axes. We have developed a systematic procedure in which we calculate the angle between these axes and rescale the orientational order parameters obtained from x-ray scattering with results that are then in good agreement with the Raman data. At least in the case of 9HL, the results obtained by both techniques support a "sugar loaf" orientational distribution in the SmA phase with no qualitative difference to conventional smectics A. The role of individual molecular fragments in promoting de Vries-type behavior is considered.

  18. Skin-inspired hydrogel–elastomer hybrids with robust interfaces and functional microstructures

    Science.gov (United States)

    Yuk, Hyunwoo; Zhang, Teng; Parada, German Alberto; Liu, Xinyue; Zhao, Xuanhe

    2016-01-01

    Inspired by mammalian skins, soft hybrids integrating the merits of elastomers and hydrogels have potential applications in diverse areas including stretchable and bio-integrated electronics, microfluidics, tissue engineering, soft robotics and biomedical devices. However, existing hydrogel–elastomer hybrids have limitations such as weak interfacial bonding, low robustness and difficulties in patterning microstructures. Here, we report a simple yet versatile method to assemble hydrogels and elastomers into hybrids with extremely robust interfaces (interfacial toughness over 1,000 Jm−2) and functional microstructures such as microfluidic channels and electrical circuits. The proposed method is generally applicable to various types of tough hydrogels and diverse commonly used elastomers including polydimethylsiloxane Sylgard 184, polyurethane, latex, VHB and Ecoflex. We further demonstrate applications enabled by the robust and microstructured hydrogel–elastomer hybrids including anti-dehydration hydrogel–elastomer hybrids, stretchable and reactive hydrogel–elastomer microfluidics, and stretchable hydrogel circuit boards patterned on elastomer. PMID:27345380

  19. Dielectric elastomer stack actuator-based autofocus fluid lens.

    Science.gov (United States)

    Rasti, Pejman; Hous, Henry; Schlaak, Helmut F; Kiefer, Rudolf; Anbarjafari, Gholamreza

    2015-11-20

    Extremely small cameras and many cell phones simply do not have enough room to allow users to move a rigid lens the distance required for a varying range of focal lengths. An adaptive liquid lens, however, enables small cameras to focus without needing extra room. An autofocus liquid lens provides several advantages over a traditional lens in terms of efficiency, cost, compactness, and flexibility. But one of the main challenges in these lenses is a high driving voltage requirement of around at least 1.8 kV. In this paper, we propose a new design of a liquid lens based on a dielectric elastomer stack actuator (DESA), which significantly overcomes the aforementioned existing problem. The lens consists of a frame (a thin DESA membrane with a hole in the middle), silicon oil, and water. A voltage range is applied on the membrane in order to change the hole dimension. Due to change of hole dimension, a change in meniscus occurs that changes the focal length of the lens. In this research work, various experimental results are achieved by configuring two DESA with different active areas. Depending on the active area of the membrane, the length of the laser beam on the plane varies from 6 to 35 mm, and the driving voltage is in the range of 50-750 V.

  20. Tunable actuation of dielectric elastomer by electromechanical loading rates

    Science.gov (United States)

    Li, Guorui; Zhang, Mingqi; Chen, Xiangping; Yang, Xuxu; Wong, Tuck-Whye; Li, Tiefeng; Huang, Zhilong

    2017-10-01

    Dielectric elastomer (DE) membranes are able to self-deform with the application of an electric field through the thickness direction. In comparison to conventional rigid counterparts, soft actuators using DE provide a variety of advantages such as high compliance, low noise, and light weight. As one of the challenges in the development of DE actuating devices, tuning the electromechanical actuating behavior is crucial in order to achieve demanded loading paths and to avoid electromechanical failures. In this paper, our experimental results show that the electromechanical loading conditions affect the actuating behaviors of the DE. The electrical actuating force can be tuned by 29.4% with the control of the electrical charging rate. In addition, controllable actuations have been investigated by the mechanical model in manipulating the electromechanical loading rate. The calculated results agree well with the experimental data. Lastly, it is believed that the mechanisms of controlling the electromechanical loading rate may serve as a guide for the design of DE devices and high performance soft robots in the near future.

  1. Toughening elastomers using mussel-inspired iron-catechol complexes.

    Science.gov (United States)

    Filippidi, Emmanouela; Cristiani, Thomas R; Eisenbach, Claus D; Waite, J Herbert; Israelachvili, Jacob N; Ahn, B Kollbe; Valentine, Megan T

    2017-10-27

    Materials often exhibit a trade-off between stiffness and extensibility; for example, strengthening elastomers by increasing their cross-link density leads to embrittlement and decreased toughness. Inspired by cuticles of marine mussel byssi, we circumvent this inherent trade-off by incorporating sacrificial, reversible iron-catechol cross-links into a dry, loosely cross-linked epoxy network. The iron-containing network exhibits two to three orders of magnitude increases in stiffness, tensile strength, and tensile toughness compared to its iron-free precursor while gaining recoverable hysteretic energy dissipation and maintaining its original extensibility. Compared to previous realizations of this chemistry in hydrogels, the dry nature of the network enables larger property enhancement owing to the cooperative effects of both the increased cross-link density given by the reversible iron-catecholate complexes and the chain-restricting ionomeric nanodomains that they form. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  2. Fuzzy Semiactive Vibration Control of Structures Using Magnetorheological Elastomer

    Directory of Open Access Journals (Sweden)

    Xuan Bao Nguyen

    2017-01-01

    Full Text Available In this research, a novel variable stiffness vibration isolator that uses magnetorheological elastomers (MREs accompanied with a fuzzy semiactive vibration control was developed. Firstly, the viscoelastic characteristics of MREs in shear mode were clarified systematically in order to achieve a mathematical basis for the controller development. Secondly, the fuzzy semiactive vibration control with a strategy based on the Lyapunov theory and dynamic characteristic of MREs was proposed for minimizing the movement of the isolator. In the conventional semiactive algorithm, the command applied current of MRE-based isolator is set at either minimum or maximum value which causes high acceleration and jerk peaks periodically, thus leading to the degeneration of the overall system quality. However, the fuzzy semiactive algorithm presented here is able to produce the sufficient applied current and thus viscoelastic force is desirably produced. The effectiveness of the developed isolator was evaluated numerically by MATLAB simulation and experimentally in comparison with the performances of a passive system and a system with on-off type semiactive controller. The results showed that the developed controller was successful in overcoming the disadvantages of conventional on-off semiactive control.

  3. Evaluation of the performance of three elastomers for non-lethal projectile applications

    OpenAIRE

    Thota N.; Epaarachchi J.; Lau K.T.

    2015-01-01

    Less lethal kinetic ammunitions with soft noses such as eXact iMpact 1006, National Sports Spartan and B&T have been commonly used by military and law enforcement officers in the situations where lethal force is not warranted. In order to explore new materials to be used as nose in such ammunitions, a scholastic study using finite element simulations has been carried out to evaluate the effectiveness of two rubber like elastomers and a polyolefinic foam (low density, highly compressible, stif...

  4. Mechanically compliant electrodes and dielectric elastomers from PEG-PDMS copolymers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    2016-01-01

    Soft conducting elastomers have been prepared from polydimethylsiloxane-polyethyleneglycol (PDMS-PEG) copolymer and surfactant-stabilized multi-walled carbon nanotubes (MWCNTs). The copolymer was chain-extended with PDMS of molecular weight 17.2 kg mol-1 in order to obtain a crosslinkable PDMS...... showed high conductivity combined with inherent softness. The high conductivity and softness, PDMS-PEG copolymers with incorporated MWCNTs hold great promises as compliant and highly stretchable electrodes for stretchable devices such as electro-mechanical transducers....

  5. Protein Crystallization

    Science.gov (United States)

    Chernov, Alexander A.

    2005-01-01

    Nucleation, growth and perfection of protein crystals will be overviewed along with crystal mechanical properties. The knowledge is based on experiments using optical and force crystals behave similar to inorganic crystals, though with a difference in orders of magnitude in growing parameters. For example, the low incorporation rate of large biomolecules requires up to 100 times larger supersaturation to grow protein, rather than inorganic crystals. Nucleation is often poorly reproducible, partly because of turbulence accompanying the mixing of precipitant with protein solution. Light scattering reveals fluctuations of molecular cluster size, its growth, surface energies and increased clustering as protein ages. Growth most often occurs layer-by-layer resulting in faceted crystals. New molecular layer on crystal face is terminated by a step where molecular incorporation occurs. Quantitative data on the incorporation rate will be discussed. Rounded crystals with molecularly disordered interfaces will be explained. Defects in crystals compromise the x-ray diffraction resolution crucially needed to find the 3D atomic structure of biomolecules. The defects are immobile so that birth defects stay forever. All lattice defects known for inorganics are revealed in protein crystals. Contribution of molecular conformations to lattice disorder is important, but not studied. This contribution may be enhanced by stress field from other defects. Homologous impurities (e.g., dimers, acetylated molecules) are trapped more willingly by a growing crystal than foreign protein impurities. The trapped impurities induce internal stress eliminated in crystals exceeding a critical size (part of mni for ferritin, lysozyme). Lesser impurities are trapped from stagnant, as compared to the flowing, solution. Freezing may induce much more defects unless quickly amorphysizing intracrystalline water.

  6. Lanthanum-rich fluorbritholite-(Ce) from young alkaline volcanic rock of Eifel (Germany) and its crystal structure. Cation ordering in britholites

    Science.gov (United States)

    Zubkova, N. V.; Chukanov, N. V.; Pekov, I. V.; Schäfer, C.; Yapaskurt, V. O.; Pushcharovsky, D. Yu.

    2015-09-01

    Structure (R=0.0213) of lanthanum-rich fluorbritholite (Ce) [(Ce2.47La2.31Nd0.22Pr0.13Y0.07)5.20Ca4.20Th0.27Mn0.19Sr0.09]9.95(Si5.37P0.63)6O24.16F1.95 from sanidinite in Laacher See, Eifel, Germany was studied on a monocrystal. The structure [space group P63/m, a = 9.58949 (13), c = 7.0289 (11) Å, V = 559.770 (14)Å3] is identical to structures of members of apatite supergroup. Relationships of major cations in polyhedra M(1)O9 = (Ca0.6 REE 0.4), and in polyhedral M(2)O6F = ( REE 0.7Ca0.3). Substantial structural order M(1) and M(2) is defined, simplified structural formula: (Ca, LREE)2( LREE,Ca)3(SiO4)3F. Analysis of data on crystal chemistry of britholite was carried out. It was demonstrated that distribution of cations on M(1)and M(2)-positions is always characteristic of partial structural order. Clear tendency of LREE concentration in M(2) position was noted.

  7. Bottlebrush elastomers: a promising molecular engineering route to tunable, prestrain-free dielectric elastomers (Conference Presentation)

    Science.gov (United States)

    Vatankhah-Varnosfaderani, Mohammad; Daniel, William F. M.; Zhushma, Alexandr P.; Li, Qiaoxi; Morgan, Benjamin J.; Matyjaszewski, Krzysztof; Armstrong, Daniel P.; Dobrynin, Andrey V.; Sheyko, Sergei S.; Spontak, Richard J.

    2017-04-01

    Electroactive polymers (EAPs) refer to a broad range of relatively soft materials that change size and/or shape upon application of an electrical stimulus. Of these, dielectric elastomers (DEs) generated from either chemically- or physically-crosslinked polymer networks afford the highest levels of electroactuation strain, thereby making this class of EAPs the leading technology for artificial-muscle applications. While mechanically prestraining elastic networks remarkably enhances DEs electroactuation, external prestrain protocols severely limit both actuator performance and device implementation due to gradual DE stress relaxation and the presence of a cumbersome load frame. These drawbacks have persisted with surprisingly minimal advances in the actuation of single-component elastomers since the dawn of the "pre-strain era" introduced by Pelrine et al. (Science, 2000). In this work, we present a bottom-up, molecular-based strategy for the design of prestrain-free (freestanding) DEs derived from covalently-crosslinked bottlebrush polymers. This architecture, wherein design factors such as crosslink density, graft density and graft length can all be independently controlled, yields inherently strained polymer networks that can be readily adapted to a variety of chemistries. To validate the use of these molecularly-tunable materials as DEs, we have synthesized a series of bottlebrush silicone elastomers in as-cast shapes. Examination of these materials reveals that they undergo giant electroactuation strains (>300%) at relatively low fields (technologies (e.g., robotics). The molecular design approach to controlling (electro)mechanical developed here is independent of chemistry and permits access to an unprecedented range of actuation properties from elastomeric materials with traditionally modest electroactuation performance (e.g., polydimethylsiloxane, PDMS). Experimental results obtained here compare favorably with theoretical predictions and demonstrate that

  8. A stretchable polysiloxane elastomer with self-healing capacity at room temperature and solvatochromic properties.

    Science.gov (United States)

    Liu, Lili; Liang, Shuai; Huang, Yawen; Hu, Chengyao; Yang, Junxiao

    2017-11-07

    A stretchable silicon elastomer comprising cobalt ions in pyridine pendant polydimethylsiloxane (PDMS) was prepared. Different from previously reported cobalt-coordinated elastomers, these elastomers are self-healable at room temperature with a high healing efficiency of over 90%. Besides, they exhibit tailored solvatochromic properties over a wide range without sacrificing its self-healing ability at room-temperature.

  9. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on tunable functionalized copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2015-01-01

    High driving voltages currently limit the commercial potential of dielectric elastomers (DEs). One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric permittivity was prepared through the synthesis...

  10. Deformation-Induced Crystallization In Rubber-Like Materials

    OpenAIRE

    Saidan, Motasem

    2005-01-01

    Deformation induced crystallization is crucial for determining the final mechanical properties of elastomers-rubber. Elastomeric networks show high upturn in the stress-strain curves with a significant hysteresis, this is attributed to the deformation induced crystallization phenomenon. Thermodynamics of rubber-like high polymers have been studied, and uniaxial extension with some approximations is discussed to obtain an overview of the proposed thermodynamic constitutive theory. A thermodyna...

  11. Surfactant-Induced Ordering and Wetting Transitions of Droplets of Thermotropic Liquid Crystals “Caged” Inside Partially Filled Polymeric Capsules

    Science.gov (United States)

    2015-01-01

    We report a study of the wetting and ordering of thermotropic liquid crystal (LC) droplets that are trapped (or “caged”) within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40% of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of “free” LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurational transitions when LC droplets were caged within polymeric capsules. Specifically, upon addition of SDS to the aqueous phase, we observed the contact angles (θ) of caged LC on the interior surface of the capsule to decrease, resulting in a progression of complex droplet shapes, including lenses (θ ≈ 130 ± 10°), hemispheres (θ ≈ 89 ± 5°), and concave hemispheres (θ designs of LC-droplet-based responsive soft matter that cannot be realized in dispersions of free droplets. PMID:24911044

  12. Thermal Degradation Studies of Polyurethane/POSS Nanohybrid Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J P; Pielichowski, K; TremblotDeLaCroix, P; Janowski, B; Todd, D; Liggat, J J

    2010-03-05

    Reported here is the synthesis of a series of Polyurethane/POSS nanohybrid elastomers, the characterization of their thermal stability and degradation behavior at elevated temperatures using a combination of Thermal Gravimetric Analysis (TGA) and Thermal Volatilization Analysis (TVA). A series of PU elastomers systems have been formulated incorporating varying levels of 1,2-propanediol-heptaisobutyl-POSS (PHIPOSS) as a chain extender unit, replacing butane diol. The bulk thermal stability of the nanohybrid systems has been characterized using TGA. Results indicate that covalent incorporation of POSS into the PU elastomer network increase the non-oxidative thermal stability of the systems. TVA analysis of the thermal degradation of the POSS/PU hybrid elastomers have demonstrated that the hybrid systems are indeed more thermally stable when compared to the unmodified PU matrix; evolving significantly reduced levels of volatile degradation products and exhibiting a {approx}30 C increase in onset degradation temperature. Furthermore, characterization of the distribution of degradation products from both unmodified and hybrid systems indicate that the inclusion of POSS in the PU network is directly influencing the degradation pathways of both the soft and hard block components of the elastomers: The POSS/PU hybrid systems show reduced levels of CO, CO2, water and increased levels of THF as products of thermal degradation.

  13. Synergistic effects in the processes of crosslinking of elastomers

    Science.gov (United States)

    Głuszewski, Wojciech; Zagórski, Zbigniew P.; Rajkiewicz, Maria

    2014-01-01

    Radiation crosslinking of elastomers is an example of the modification of polymers by ionizing radiation. In practice, often parallel both traditional crosslinking (with peroxide) and radiation treatment is applied (Bik et al., 2003, 2004). Elastomers can be irradiated both before and/or after vulcanization products. The aim of this study was to investigate the system of the mixed radiation/peroxide and peroxide/radiation crosslinking of selected elastomers (Engage 8200, HNBR). In particular, attention was directed to the influence of the protective effects of aromatic additives in elastomers (peroxides, thermal- and light stabilizers) on the phenomenon of crosslinking and postradiation oxidation. Aromatic peroxides may undergo modifications during the preirradiation, which affect the subsequent processes of vulcanization. In this way the method of gas chromatography (GC) was applied for determination of hydrogen and oxidation effects, never described before for Engage 8200. Using that approach, radiation efficiency of hydrogen evolution and oxygen absorption efficiency of the polymers has been identified. To describe the phenomena of postradiation oxidation of elastomers, the method of Diffuse Reflection Spectrophotometry (DRS) was also applied.

  14. Ageing by UV radiation of an elastomer modified bitumen

    Energy Technology Data Exchange (ETDEWEB)

    Virginie Mouillet; Fabienne Farcas; Stanislas Besson [CETE Mediterranee Pole d' activite, Aix-en-Provence (France). Laboratoire Regional des Ponts et Chaussees d' Aix-en-Provence

    2008-09-15

    Laboratory methods to simulate the short- and long-term ageing occurring during the service life of pure and polymer modified bitumens in a pavement are standardized but none of them takes into account the influence of UV radiations. If the impact of thermal ageing on the degradation of SBS elastomers in bitumens has been extensively studied, there is not study dealing with the photo-oxidation of these copolymers in a bituminous matrix. So, the aim of our study was to investigate, by FTIR spectrometry and SEC chromatography, whether the architecture of elastomers (linear or radial) might have any influence on their ageing by UV radiation in a bituminous matrix. The results show that the elastomers oxidation kinetic, unlike the disappearance kinetic of trans-butadiene double bond, does not depend on their architecture. But, when putted into the same base bitumen, the two copolymers show exactly the same oxidation kinetic and the same decreasing kinetic of trans-butadiene double bond. So, this study has revealed that inside the bituminous matrix, on the one hand, the elastomers architecture does not influence on its degradation when submitted to UV radiation and, on the other hand, there is a 'protection' of the elastomers by the studied bitumen towards UV radiation. 46 refs., 13 figs., 2 tabs.

  15. Micromechanical properties of biomedical hydrogel for application as microchannel elastomer.

    Science.gov (United States)

    Ige, Ebenezer O; Raj, M Kiran; Dare, Ademola A; Chakraborty, Suman

    2018-01-01

    Polymers are believed to be the building blocks for the creation of the next generation of materials and devices in practically all areas of biomedical research. There are a number of polymers that are being employed in varied applications in microfluidic platform due to the tremendous possibilities for soft matter based elastomers especially in biomedical applications. Polymeric hydrogels have been used as building block in micro-confinements and for specified function such as flow control. The need exists to suitably determine the mechanical characteristics of gel-based materials for possible use as a microchannel elastomer. In this investigation, we describe synthesis procedure, morphological, wettability characterization of hydrogel elastomer synthesized by free-radical polymerization crosslinked over varying acrylamide composition for 10% w/v: 25% w/w, 15% w/v: 25% w/w, 20% w/v: 25% w/w and 25% w/v: 25% w/w respectively. Micromechanical properties such as surface morphology, wettability, and micro-rheological behaviour of hydrogel elastomer using standard protocols was undertaken to determine roughness, contact angle, loss modulus and storage modulus over varied cross-linking of the constituent monomers. The impact of these parameters on flow transport and microchannel structural stability is well delineated in this report. We established that polymeric hydrogel could be a candidate for whole microchannel elastomer with suitable application in areas of tissues and biomedical engineering to mimic native biological transport conduits. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Environment-friendly, flame retardant thermoplastic elastomer-magnesium hydroxide composites

    Science.gov (United States)

    Tang, Hao; Chen, Kunfeng; Li, Xiaonan; Ao, Man; Guo, Xinwen; Xue, Dongfeng

    Halogen-free and environment-friendly magnesium hydroxide (Mg(OH)2) was synthesized to enhance the flame retardant properties of thermoplastic elastomer (TPE). When the Mg(OH)2 content was optimized to 35wt.%, the TPE-Mg(OH)2 composites exhibited the best flame retardant properties. The results showed that there was a delay of ignition time of the samples containing Mg(OH)2; compared with the samples without Mg(OH)2, the heat release rate and total heat release decrease by 31.4% and 35.6%, while total smoke production and mass loss rate reduce by 56% and 34.2%, respectively. This work opens a door to manufacture fire-resistant polymer-based composites with environmental-friendly flame retardant additives by controllable crystallization and chemical strategies.

  17. Identification and characterization of the out-of-plane resonance in a dielectric elastomer to drive an agile robotic cube

    Science.gov (United States)

    Tang, Chao; Li, Bo; Sun, Wenjie; Li, Zhiqiang; Chen, Hualing

    2017-10-01

    A dielectric elastomer (DE) vibrates and resonates mechanically under an alternating voltage and the vibrations undergo a transition from the in-plane to the out-of-plane state. In this study, a phase diagram was established experimentally to illustrate this transition and an electromechanical model was proposed to predict the transition using the boundary conditions. The resonance frequencies were calculated and were shown to be consistent with the experimentally obtained values. A novel vibration-driven robotic cube was then designed and powered by the dielectric elastomer at the 1st order out-of-plane resonance. The agile robotic cube is ultralight and demonstrated a speedy response of 125 mm/s (1.8 body length/s), which is superior to the locomotive dynamics of the existing DE-based robotic devices.

  18. Interpenetrated polymer networks based on commercial silicone elastomers and ionic networks with high dielectric permittivity and self-healing properties

    DEFF Research Database (Denmark)

    Ogliani, Elisa; Yu, Liyun; Skov, Anne Ladegaard

    the applicability. One method used to avoid this limitation is to increase the dielectric permittivity of the material in order to improve the actuation response at a given field. Recently, interpenetrating polymer networks (IPNs) based on covalently cross-linked commercial silicone elastomers and ionic networks...... from amino- and carboxylic acid- functional silicones have been designed[2] (Figure 1). This novel system provides both the mechanical stability and the high breakdown strength given by the silicone part of the IPNs and the high permittivity and the softening effect of the ionic network. Thus...... these improved properties are achieved without consequently increased Young’s moduli and decreased breakdown strength compared, for example, with other silicone elastomers containing fillers. In particular, the interpenetrating systems show dielectric permittivity ε’ from 6,7 to 2 x 103 at low frequencies (0...

  19. Inkjet 3D printing of UV and thermal cure silicone elastomers for dielectric elastomer actuators

    Science.gov (United States)

    McCoul, David; Rosset, Samuel; Schlatter, Samuel; Shea, Herbert

    2017-12-01

    Dielectric elastomer actuators (DEAs) are an attractive form of electromechanical transducer, possessing high energy densities, an efficient design, mechanical compliance, high speed, and noiseless operation. They have been incorporated into a wide variety of devices, such as microfluidic systems, cell bioreactors, tunable optics, haptic displays, and actuators for soft robotics. Fabrication of DEA devices is complex, and the majority are inefficiently made by hand. 3D printing offers an automated and flexible manufacturing alternative that can fabricate complex, multi-material, integrated devices consistently and in high resolution. We present a novel additive manufacturing approach to DEA devices in which five commercially available, thermal and UV-cure DEA silicone rubber materials have been 3D printed with a drop-on-demand, piezoelectric inkjet system. Using this process, 3D structures and high-quality silicone dielectric elastomer membranes as thin as 2 μm have been printed that exhibit mechanical and actuation performance at least as good as conventionally blade-cast membranes. Printed silicone membranes exhibited maximum tensile strains of up to 727%, and DEAs with printed silicone dielectrics were actuated up to 6.1% area strain at a breakdown strength of 84 V μm‑1 and also up to 130 V μm‑1 at 2.4% strain. This approach holds great potential to manufacture reliable, high-performance DEA devices with high throughput.

  20. Partial discharge analysis of prestretched and unstretched acrylic elastomers for Dielectric Elastomer Actuators (DEA)

    Science.gov (United States)

    Muffoletto, Daniel P.; Burke, Kevin M.; Zirnheld, Jennifer L.

    2012-04-01

    Partial discharges (PD) occur in solid insulating materials when the insulating material is partially bridged by an electrical discharge in response to an applied voltage stress. PDs typically occur at localized points of high field stresses or at voids and other inhomogeneities within the insulator. The applied field's effect on the frequency of occurrence and intensity of PDs can be used to assess the electrical breakdown strength and aging characteristics of insulating materials. PD testing is therefore a promising characterization method to understand the insulating properties of the elastomers and geometries commonly used in DEAs. Prestretched (~100% and ~230% biaxial) and unstretched acrylic elastomers (3M VHB tapes) with solid metal electrodes have been tested. We have found the number and intensity of PDs increase with applied field, and that a significant number of PDs are detected before any actuation was visibly observed, implying that the fields required for actuation will cause material aging and degradation over time. Most interestingly, the number of PDs steadily increase as the applied voltage increases up to a sufficiently high voltage, where the PDs suddenly cease. Since internal voids can cause PDs, this may indicate that the Maxwell stress minimized the thickness of or eliminated these voids, which could explain how prestretching improves performance.

  1. The Thickness And Stretch Dependence Of The Electrical Breakdown Strength Of An Acrylic Dielectric Elastomer

    Science.gov (United States)

    Huang, Jiangshui; Suo, Zhigang; Clarke, David

    2013-03-01

    The performance of dielectric elastomer actuators is limited by electrical breakdown. Attempts to measure this are confounded by the voltage-induced thinning of the elastomer. A test configuration is introduced that avoids this problem: A thin sheet of elastomer is stretched, crossed-wire electrodes attached, and then embedded in a stiff polymer. The applied electric field at breakdown EB is found to depend on both the deformed thickness, h, and the stretch applied, λ. For the acrylic elastomer investigated, the breakdown field scales as EB = 51h - 0 . 25λ 0 . 63 . The test configuration allows multiple individual tests to be made on the same sheet of elastomer.

  2. An integrated dielectric elastomer generator model

    Science.gov (United States)

    McKay, Thomas; O'Brien, Benjamin; Calius, Emilio; Anderson, Iain

    2010-04-01

    Dielectric Elastomer Generator(s) (DEG), are essentially variable capacitor power generators formed by hyper-elastic dielectric materials sandwiched between flexible electrodes. Electrical energy can be produced from a stretched, charged DEG by relaxing the mechanical deformation whilst maintaining the amount of charge on its electrodes. This increases the distance between opposite charges and packs likecharges more densely, increasing the amount of electrical energy. DEG show promise for harvesting energy from environmental sources such as wind and ocean waves. DEG can undergo large inhomogeneous deformations and electric fields during operation, meaning it can be difficult to experimentally determine optimal designs. Also, the circuit that is used for harnessing DEG energy influences the DEG output by controlling the amount of charge on the DEG. In this paper an integrated DEG model was developed where an ABAQUS finite element model is used to model the DEG and data from this model is input to a system level LT-Spice circuit simulation. As a case-study, the model was used as a design tool for analysing a diaphragm DEG connected to a self-priming circuit. That is, a circuit capable of overcoming electrical losses by using some of the DEG energy to boost the charge in the system. Our ABAQUS model was experimentally validated to predict the varying capacitance of a diaphragm DEG deformed inhomogeneously to within 6% error.

  3. Realizing the potential of dielectric elastomer generators

    Science.gov (United States)

    McKay, Thomas; O'Brien, Benjamin; Calius, Emilio; Anderson, Iain

    2011-04-01

    The global demand for renewable energy is growing, and ocean waves and wind are renewable energy sources that can provide large amounts of power. A class of variable capacitor power generators called Dielectric Elastomer Generators (DEG), show considerable promise for harvesting this energy because they can be directly coupled to large broadband motions without gearing while maintaining a high energy density, have few moving parts, and are highly flexible. At the system level DEG cannot currently realize their full potential for flexibility, simplicity and low mass because they require rigid and bulky external circuitry. This is because a typical generation cycle requires high voltage charge to be supplied or drained from the DEG as it is mechanically deformed. Recently we presented the double Integrated Self-Priming Circuit (ISPC) generator that minimized external circuitry. This was done by using the inherent capacitance of DEG to store excess energy. The DEG were electrically configured to form a pair of charge pumps. When the DEG were cyclically deformed, the charge pumps produced energy and converted it to a higher charge form. In this paper we present the single ISPC generator that contains just one charge pump. The ability of the new generator to increase its voltage through the accumulation of generated energy did not compare favourably with that of the double ISPC generator. However the single ISPC generator can operate in a wider range of operating conditions and the mass of its external circuitry is 50% that of the double ISPC generator.

  4. Inorganic particle analysis of dental impression elastomers.

    Science.gov (United States)

    Carlo, Hugo Lemes; Fonseca, Rodrigo Borges; Soares, Carlos José; Correr, Américo Bortolazzo; Correr-Sobrinho, Lourenço; Sinhoreti, Mário Alexandre Coelho

    2010-01-01

    The aim of this study was to determine quantitatively and qualitatively the inorganic particle fraction of commercially available dental elastomers. The inorganic volumetric fraction of two addition silicones (Reprosil Putty/Fluid and Flexitime Easy Putty/Fluid), three condensation silicones (Clonage Putty/Fluid, Optosil Confort/Xantopren VL and Silon APS Putty/Fluid), one polyether (Impregum Soft Light Body) and one polysulfide (Permlastic Light Body) was accessed by weighing a previously determined mass of each material in water before and after burning samples at 600 ºC, during 3 h. Unsettled material samples were soaked in acetone and chloroform for removal of the organic portion. The remaining filler particles were sputter-coated with gold evaluation of their morphology and size, under scanning electron microscopy (SEM). Flexitime Easy Putty was the material with the highest results for volumetric particle fraction, while Impregum Soft had the lowest values. Silon 2 APS Fluid presented the lowest mean filler size values, while Clonage Putty had the highest values. SEM micrographs of the inorganic particles showed several morphologies - lathe-cut, spherical, spherical-like, sticks, and sticks mixed to lathe-cut powder. The results of this study revealed differences in particle characteristics among the elastometic materials that could lead to different results when testing mechanical properties.

  5. Numerical analysis of helical dielectric elastomer actuator

    Science.gov (United States)

    Park, Jang Ho; Nair, Saurabh; Kim, Daewon

    2017-04-01

    Dielectric elastomer actuators (DEA) are known for its capability of experiencing extreme strains, as it can expand and contract based on specific actuation voltage applied. On contrary, helical DEA (HDEA) with its unique configuration does not only provide the contractile and extendable capabilities, but also can aid in attaining results for bending and torsion. The concept of HDEA embraces many new techniques and can be applied in multiple disciplines. Thus, this paper focuses on the simulation of HDEA with helical compliant electrodes that is a major factor prior to its application. The attributes of the material used to build the structure plays a vital role in the behavior of the system. For numerical analysis of HDEA, the material characteristics are input into a commercial grade software, and then the appropriate analysis is performed to retrieve its outcome. Applying the material characteristics into numerical analysis modeling, the functionality of HDEA for various activations can be achieved, which is used to test and comply with the fabricated final product.

  6. Hysteretic behavior of soft magnetic elastomer composites

    Energy Technology Data Exchange (ETDEWEB)

    Krautz, Maria; Werner, David [Institute for Complex Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Schrödner, Mario [Thuringian Institute of Textile and Plastics Research e.V., Breitscheidstraße 97, D-07407 Rudolstadt (Germany); Funk, Alexander [Institute for Complex Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Jantz, Alexander; Popp, Jana [Thuringian Institute of Textile and Plastics Research e.V., Breitscheidstraße 97, D-07407 Rudolstadt (Germany); Eckert, Jürgen [Institute for Complex Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstraße 12, A-8700 Leoben (Austria); Department of Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben (Austria); Waske, Anja [Institute for Complex Materials, IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany)

    2017-03-15

    Composites of polymer and micron-sized particles of carbonyl-iron were investigated in terms of their magnetization behavior. Thermoplastic elastomers with varying Young's modulus (E{sub Polymer}=0.14–14.6 MPa) were used as matrix material. Field dependent magnetization curves reveal that the hysteretic behavior of the composites strongly depends on both the particle fraction (7, 10, 14, 21, 31 vol%) and on the mechanical properties of the polymer. It is shown that hysteresis only appears above a certain fraction of magnetic particles which can be accounted to the magnetic exchange between the particles. However, hysteresis is suppressed in the composite with largest Young's modulus of the polymer matrix, even at largest particle fraction. - Highlights: • Composites with soft magnetic Iron Particles show hysteretic magnetization behavior. • Origin of the hysteresis is the alignment of particles along field direction. • Hysteresis depends on both, mechanical properties of matrix and particle fraction.

  7. Shear Stress Sensing using Elastomer Micropillar Arrays

    Science.gov (United States)

    Wohl, Christopher J.; Palmieri, Frank L.; Lin, Yi; Jackson, Allen M.; Cissoto, Alexxandra; Sheplak, Mark; Connell, John W.

    2013-01-01

    The measurement of shear stress developed as a fluid moves around a solid body is difficult to measure. Stresses at the fluid-solid interface are very small and the nature of the fluid flow is easily disturbed by introducing sensor components to the interface. To address these challenges, an array of direct and indirect techniques have been investigated with various advantages and challenges. Hot wire sensors and other indirect sensors all protrude significantly into the fluid flow. Microelectromechanical systems (MEMS) devices, although facilitating very accurate measurements, are not durable, are prone to contamination, and are difficult to implement into existing model geometries. One promising approach is the use of engineered surfaces that interact with fluid flow in a detectable manner. To this end, standard lithographic techniques have been utilized to generate elastomeric micropillar arrays of various lengths and diameters. Micropillars of controlled length and width were generated in polydimethylsiloxane (PDMS) elastomer using a soft-lithography technique. The 3D mold for micropillar replication was fabricated using laser ablative micromachining and contact lithography. Micropillar dimensions and mechanical properties were characterized and compared to shear sensing requirements. The results of this characterization as well as shear stress detection techniques will be discussed.

  8. Optimization of electrode placement in electromyographic control of dielectric elastomers

    Science.gov (United States)

    Walbran, Scott H.; Calius, Emilio P.; Dunlop, G. Reg; Anderson, Iain A.

    2009-03-01

    Human intention recognition is becoming a key part of powered prosthetics research. With the advent of smart materials, the usefulness of powered prosthetics has increased. Correspondingly, there is a greater need for control technology. Electromyography (EMG) has previously been used to control myoelectric hands; however the approach to electrode placement has been speculative at best. Carpi, Raspopovic and De Rossi have shown that dielectric elastomer actuators (DEAs) can be controlled by a variety of human electrophysiological signals, including EMG. To control a DEA device with multiple degrees of freedom using EMG, multiple electrode sites are required. This paper presents an approach to control an array of DEAs using a series of electrodes and an optimized electrode data filtering scheme to maximize classification accuracy when differentiating between hand grasps. A silicon mould of a human forearm was created with an array of electrodes embedded within it. Data from each electrode site was recorded using the Universal Electrophysiological Mapping (UnEmap) system developed at the University of Auckland Bioengineering Institute for the amplification and filtering of multiple biopotential signals. The recorded data was then processed off-line, in order to calculate spatial gradients; this would determine which electrode sites would give the best bipolar readings. The spatial gradients were then compared to each other in order to find the optimal electrode sites. Several points in the extensor compartment of the forearm were found to be useful in recognizing grasping, while several points in the flexor compartment of the forearm were found to be useful in differentiating between grasps.

  9. Exploring dielectric elastomers as actuators for hand tremor suppression

    Science.gov (United States)

    Kelley, Christopher R.; Kauffman, Jeffrey L.

    2017-04-01

    Pathological tremor results in undesired motion of body parts, with the greatest effect typically occurring in the hands. Since common treatment methods are ineffective in some patients or have risks associated with surgery or side effects, researchers are investigating mechanical means of tremor suppression. This work explores the viability of dielectric elastomers as the actuators in a tremor suppression control system. Dielectric elastomers have many properties similar to human muscle, making them a natural fit for integration into the human biomechanical system. This investigation develops a model of the integrated wrist-actuator system to determine actuator parameters that produce the necessary control authority without significantly affecting voluntary motion. Furthermore, this paper develops a control law for the actuator voltage to increase the effective viscous damping of the system. Simulations show excellent theoretical tremor suppression, demonstrating the potential for dielectric elastomers to suppress tremor while maximizing compatibility between the actuator and the human body.

  10. Fracture Behavior of Dielectric Elastomer under Pure Shear Loading

    Science.gov (United States)

    Ahmad, D.; Patra, K.

    2017-09-01

    Dielectric elastomer has become a very important material for many emerging applications areas like optics, micro fluidics, sensors, actuators and energy harvesting. However, these elastomer components are prone to fracture or catastrophic failure because of defects likes notches, flaws, and fatigue crack, impurities which occur during production or during service. To make better use of this material, it is important to investigate fracture characteristics under different operating conditions. This study experimentally investigated the effects of notch length and strain rate on the fracture toughness, failure stretch and failure stress of acrylic elastomer under pure shear deformation mode. It is observed that failure stretch depends on notch length and independent of strain rate, but failure stress decreases with increasing notch length and increases with increasing strain rate. It is also found that fracture toughness is independent of notch lengths. However, fracture toughness is found to increase with strain rate.

  11. Functional silicone copolymers and elastomers with high dielectric permittivity

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    , thereby forming a capacitor [1]. Silicone elastomers are one of the most used materials for DEs due to their high efficiency, fast response times and low viscous losses. The major disadvantage of silicone elastomers is that they possess relatively low dielectric permittivity, which means that a high......(pentafluorophenyl)borane catalysed Piers-Rubinsztajn reaction [3] and have a high degree of chemical freedom, as several parameters can be varied during the preparation phase. Thus, the space between the functional groups can be varied, by using different dimethylsiloxane spacer units between the high dielectric permittivity...... molecules. Furthermore, the degree of functionalization of the copolymers can be varied accurately by changing the feed of the high dielectric permittivity molecules. As a result, a completely tuneable elastomer system, with respect to functionalization, is achieved....

  12. Ankle-foot orthosis using elastomer-embedded flexible joint.

    Science.gov (United States)

    Abe, Isao; Ishiya, Kohei; Oshimoto, Taiki; Kikuchi, Takehito; Tanida, Sosuke; Yasuda, Takashi

    2017-07-01

    We proposed a new ankle-foot orthosis using elastomer-embedded flexible joints (EEFJ), composed of C-shaped springs and 3D-printed circular elastomer. This orthosis was designed to reduce burden on the tibialis anterior muscle (TA) and to achieve clearance between the tip of the toe and the ground. Strength testing, and gait analysis were conducted for the orthosis. According to the results of strength testing, the combination of the C-spring with 0.3 mm and 0.5 mm thickness and the elastomer with 30% and 60% filling density performs a supporting torque of 0.7-2.3 Nm to plantarflexion. In contrast, torques in the other directions were relatively small. According to the results of gait experiments in seven healthy young subjects, the proposed orthosis successfully reduced the TA activation on initial contact and in the swing phase, and range of motion on initial contact.

  13. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei [Xi' an Jiaotong University, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an (China); Xi' an Jiaotong University, School of Mechanical Engineering, Xi' an (China)

    2013-02-15

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers. (orig.)

  14. Novel ankle orthosis with elastomer-embedded flexible joint.

    Science.gov (United States)

    Kikuchi, Takehito; Ishiya, Kohei; Abe, Isao; Tanida, Sosuke; Yasuda, Takashi

    2017-07-01

    In this study, we propose a new ankle orthosis with elastomer-embedded flexible joints (EEFJ), composed of C-shaped springs and 3D-printed circular elastomer. This orthosis was designed to reduce burden on the tibialis anterior muscle (TA) and to achieve clearance between the tip of the toe and the ground. Fabrication method, strength testing, and gait analysis were conducted. According to the results of strength testing, the combination of the C-spring with 0.3 mm and 0.5 mm thickness and the elastomer with 30% and 60% filling density performs a supporting torque of 0.7-2.3 Nm to plantarflexion. In contrast, torques in the other directions were relatively small. According to the results of gait experiments in seven healthy young subjects, the proposed orthosis successfully reduced activation of TA on initial contact and in the swing phase, and range of motion on initial contact.

  15. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Science.gov (United States)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei

    2013-02-01

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers.

  16. Effect of environmental stress on Sylgard 170 silicone elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Buckalew, W.H.; Wyant, F.J.

    1985-05-01

    Dow Corning Sylgard 170 Silicone Elastomer has been investigated to characterize its response to accelerated thermal aging, radiation exposure, and its behavior under applied compressive forces. Sylgard 170 response to accelerated thermal aging suggests the material properties are not particularly age dependent. Radiation exposures, however, produce significant, monotonic changes in both elongation and hardness with increasing absorbed radiation dose. Elastomer response to an applied compressive force was strongly dependent on environment temperature and degree of material confinement. Variations in temperature produced large changes in compressive forces applied to confined samples. Attempts to mitigate force fluctuations by means of pressure relief paths resulted in total loss of the applied compressive force. Thus, seal applications employing this elastomer in Class 1E equipment required to function during or following an accident should consider the potential loss of compressive force from long-term aging and potential LOCA-temperature transient conditions.

  17. Magnetochemistry of the tetrahaloferrate (III) ions. 7. Crystal structure and magnetic ordering in (pyridinium){sub 3}Fe{sub 2}Br{sub 9}

    Energy Technology Data Exchange (ETDEWEB)

    Lowe, C.B.; Shaviv, R.; Carlin, R.L. [Univ. of Illinois, Chicago, IL (United States)] [and others

    1994-07-06

    A monoclinic crystal structure was found by X-ray diffraction for bis [pyridinium tetrabromferrate(III)]-pyridinium bromide. The double salt contains two slightly distorted [FeBr{sub 4}]{sup -} tetrahedra, three pyridinium rings, and an uncoordinated halide in each asymmetric unit, as is characteristic of the A{sub 3}Fe{sub 2}X{sub 9} series of compounds. Unit cell parameters, monoclinic space group P2{sub 1}, are a = 7.656(3) {angstrom}, b = 14.237(5) {angstrom}, c = 13.725(5) {angstrom}, {beta} = 93.42(3){degrees}, and V = 1493(1) {angstrom}{sup 3}, using Mo K{alpha} radiation {lambda} = 0.710 69 {angstrom}, {rho}{sub calc} = 2.38 g cm{sup -3}, and Z = 2. The tetrahedra are aligned with their 3-fold axes parallel to the crystallographic c axis. Bond lengths (Fe-Br) range from 2.271(9) {angstrom} to 2.379(9) {angstrom} for the two different slightly distorted tetrahedral units. Magnetic susceptibility studies show that the material orders three-dimensionally at 7.4 {+-} 0.2 K. The data are compared to a HTS expansion of 1/{sub {chi}} for the S = 5/2 three-dimensional Heisenberg model antiferromagnet for a sc lattice with g = 1.98 and J/k{sub B} = -0.43 K. The specific heat measurements indicate two odd-shaped {lambda} features, at 7.3 and 8 K.

  18. Crystal fields, disorder, and antiferromagnetic short-range order in (Yb{sub 0.24}Sn{sub 0.76})Ru

    Energy Technology Data Exchange (ETDEWEB)

    Klimczuk, T; Wang, C H; Lawrence, J M; Xu, Q; Durakiewicz, T; Ronning, F; Llobet, A; Trouw, F; Kurita, N; Tokiwa, Y; Lee, Han-oh; Booth, C H; Gardner, J S; Bauer, E D; Joyce, J J; Zandbergen, H W; Movshovich, R; Cava, R J; Thompson, J D

    2011-07-18

    We report extensive measurements on a new compound (Yb{sub 0.24}Sn{sub 0.76})Ru that crystallizes in the cubic CsCl structure. Valence band photoemission and L{sub 3} x-ray absorption show no divalent component in the 4f configuration of Yb. Inelastic neutron scattering (INS) indicates that the eight-fold degenerate J-multiplet of Yb{sup 3+} is split by the crystalline electric field (CEF) into a Γ{sub 7} doublet ground state and a Γ{sub 8} quartet at an excitation energy 20 meV. The magnetic susceptibility can be fit very well by this CEF scheme under the assumption that a Γ{sub 6} excited state resides at 32 meV; however, the Γ{sub 8}/Γ{sub 6} transition expected at 12 meV was not observed in the INS. The resistivity follows a Bloch-Grüneisen law shunted by a parallel resistor, as is typical of systems subject to phonon scattering with no apparent magnetic scattering. All of these properties can be understood as representing simple local moment behavior of the trivalent Yb ion. At 1 K, there is a peak in specific heat that is too broad to represent a magnetic phase transition, consistent with absence of magnetic reflections in neutron diffraction. On the other hand, this peak also is too narrow to represent the Kondo effect in the Γ{sub 7} ground state doublet. On the basis of the field-dependence of the specific heat, we argue that antiferromagnetic shortrange order (possibly co-existing with Kondo physics) occurs at low temperatures. The long-range magnetic order is suppressed because the Yb site occupancy is below the percolation threshold for this disordered compound.

  19. Optimization Techniques for Improving the Performance of Silicone-Based Dielectric Elastomers

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard; Yu, Liyun

    2017-01-01

    Dielectric elastomers are possible candidates for realizing products that are in high demand by society, such as soft robotics and prosthetics, tactile displays, and smart wearables. Diverse and advanced products based on dielectric elastomers are available; however, no elastomer has proven ideal...... the electro-mechanical performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are investigated and discussed, with special emphasis placed on the promise each method holds. The compositing and blending of elastomers are shown to be simple, versatile...... that there is not a single optimization technique that will lead to the universal optimization of dielectric elastomer films, though each method may lead to elastomers with certain features, and thus certain potentials....

  20. Hemispherical breathing mode speaker using a dielectric elastomer actuator.

    Science.gov (United States)

    Hosoya, Naoki; Baba, Shun; Maeda, Shingo

    2015-10-01

    Although indoor acoustic characteristics should ideally be assessed by measuring the reverberation time using a point sound source, a regular polyhedron loudspeaker, which has multiple loudspeakers on a chassis, is typically used. However, such a configuration is not a point sound source if the size of the loudspeaker is large relative to the target sound field. This study investigates a small lightweight loudspeaker using a dielectric elastomer actuator vibrating in the breathing mode (the pulsating mode such as the expansion and contraction of a balloon). Acoustic testing with regard to repeatability, sound pressure, vibration mode profiles, and acoustic radiation patterns indicate that dielectric elastomer loudspeakers may be feasible.

  1. Synthetic Strategies for High Dielectric Constant Silicone Elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt

    -linker for silicone polymer networks. The silicone compatible cross-linker allowed for copper-catalysed azide-alkyne cycloadditions (CuAAC) and thereby the attachment of functional groups to the network crosslinking point. The functional groups were very well-distributed in the silicone elastomer matrix, and various...... extender’ that allowed for chemical modifications such as Cu- AAC. This route was promising for one-pot elastomer preparation and as a high dielectric constant additive to commercial silicone systems. The second approach used the borane-catalysed Piers-Rubinsztajn reaction to form spatially well...

  2. Development of dielectric elastomer nanocomposites as stretchable actuating materials

    Science.gov (United States)

    Wang, Yu; Sun, L. Z.

    2017-10-01

    Dielectric elastomer nanocomposites (DENCs) filled with multi-walled carbon nanotubes are developed. The electromechanical responses of DENCs to applied electric fields are investigated through laser Doppler vibrometry. It is found that a small amount of carbon nanotube fillers can effectively enhance the electromechanical performance of DENCs. The enhanced electromechanical properties have shown not only that the desired thickness strain can be achieved with reduced required electric fields but also that significantly large thickness strain can be obtained with any electric fields compared to pristine dielectric elastomers.

  3. Research Update: Platinum-elastomer mesocomposite as neural electrode coating

    Directory of Open Access Journals (Sweden)

    Ivan R. Minev

    2015-01-01

    Full Text Available Platinum is electrochemically stable and biocompatible, and remains the preferred material for the fabrication of implantable neural electrodes. In a foil or film format, platinum is mechanically stiff compared to interfaced biological tissue. We report a soft, highly stable platinum-elastomer composite that offers both mechanical compliance and the electrochemical properties of platinum. We demonstrate the high-performance of the novel mesocomposite printed on stretchable microelectrodes both in vitro and in vivo. The platinum-elastomer composite is a new promising coating for chronic neural interfaces.

  4. Improved electromechanical behavior in castable dielectric elastomer actuators

    Science.gov (United States)

    Akbari, Samin; Rosset, Samuel; Shea, Herbert R.

    2013-02-01

    Non-viscoelastic castable elastomers are replacing the polyacrylate VHB films in the new generations of dielectric elastomer actuators (DEAs) to achieve fast and reliable actuation. We introduce the optimum prestretch conditions to enhance the electromechanical behavior of the castable DEAs resulting in large actuation strain. For castable actuator in which the thickness is selected independent of the prestretch, uniaxial prestretch mode offers the highest actuation strain in the transverse direction compared to biaxial and pure shear. We experimentally demonstrate that miniaturization hinders the loss of tension and up to 85% linear actuation strain is generated with a 300 × 300 μm2 polydimethylsiloxanes-based DEA.

  5. Antiferromagnetic ordering states of oxygen-deficient NdBa2Cu3O6+x and Nd1+yBa2-yCu3O6+x single crystals

    DEFF Research Database (Denmark)

    Brecht, E.; Schweiss, P.; Wolf, T.

    1999-01-01

    The paper describes a study of the antiferromagnetic ordering of oxygen-deficient Nd1 + yBa2 - yCu3O6 + x single crystals. In pure, stoichiometric samples, y = 0, with different oxygen contents x in the Cu(1) plane (0.02

  6. Microstructure property relationships of urethane magnetorheological elastomers

    Science.gov (United States)

    Boczkowska, Anna; Awietjan, Stefan F.; Wroblewski, Rafal

    2007-10-01

    Studies on the structure of urethane magnetorheological elastomers (MREs), with respect to their magnetic and mechanical properties, are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. Samples with different numbers of particles (1.5, 11.5 and 33 vol%) were produced. The microstructure and magnetic properties of the obtained MREs were studied. Also, the displacement of the samples in an external magnetic field was examined using a specially designed experimental set-up. The influences of the number of ferromagnetic particles and their arrangement in relation to the external magnetic field were investigated. It was found that the microstructure of the MREs depends on the number of ferrous particles and the fabrication conditions. The orientation of the iron particles into aligned chains is possible for a lower volume content of the ferromagnetic fillers. The high carbonyl-iron volume content in the matrix leads to the formation of more complex microstructures, similar to three-dimensional lattices. The magnetic measurements also confirmed the existence of the microstructure anisotropy for the MREs with 1.5 and 11.5 vol% of iron particles. The structural and magnetic anisotropy has not been found in the MREs with 33 vol% of Fe. To evaluate the effect of the external magnetic field on the magnetorheological properties, the displacement under magnetic field, the compressive strength, and the rheological properties were measured. The experiments showed that both the particle content and the field strength used during curing have a significant effect on the microstructure of the MREs and, in consequence, on their properties.

  7. Printing low-voltage dielectric elastomer actuators

    Science.gov (United States)

    Poulin, Alexandre; Rosset, Samuel; Shea, Herbert R.

    2015-12-01

    We demonstrate the fabrication of fully printed thin dielectric elastomer actuators (DEAs), reducing the operation voltage below 300 V while keeping good actuation strain. DEAs are soft actuators capable of strains greater than 100% and response times below 1 ms, but they require driving voltage in the kV range, limiting the possible applications. One way to reduce the driving voltage of DEAs is to decrease the dielectric membrane thickness, which is typically in the 20-100 μm range, as reliable fabrication becomes challenging below this thickness. We report here the use of pad-printing to produce μm thick silicone membranes, on which we pad-print μm thick compliant electrodes to create DEAs. We achieve a lateral actuation strain of 7.5% at only 245 V on a 3 μm thick pad-printed membrane. This corresponds to a ratio of 125%/kV2, by far the highest reported value for DEAs. To quantify the increasing stiffening impact of the electrodes on DEA performance as the membrane thickness decreases, we compare two circular actuators, one with 3 μm- and one with 30 μm-thick membranes. Our experimental measurements show that the strain uniformity of the 3 μm-DEA is indeed affected by the mechanical impact of the electrodes. We developed a simple DEA model that includes realistic electrodes of finite stiffness, rather than assuming zero stiffness electrodes as is commonly done. The simulation results confirm that the stiffening impact of the electrodes is an important parameter that should not be neglected in the design of thin-DEAs. This work presents a practical approach towards low-voltage DEAs, a critical step for the development of real world applications.

  8. Soft segmented inchworm robot with dielectric elastomer muscles

    Science.gov (United States)

    Conn, Andrew T.; Hinitt, Andrew D.; Wang, Pengchuan

    2014-03-01

    Robotic devices typically utilize rigid components in order to produce precise and robust operation. Rigidity becomes a significant impediment, however, when navigating confined or constricted environments e.g. search-and-rescue, industrial pipe inspection. In such cases adaptively conformable soft structures become optimal. Dielectric elastomers (DEs) are well suited for developing such soft robots since they are inherently compliant and can produce large musclelike actuation strains. In this paper, a soft segmented inchworm robot is presented that utilizes pneumatically-coupled DE membranes to produce inchworm-like locomotion. The robot is constructed from repeated body segments, each with a simple control architecture, so that the total length can be readily adapted by adding or removing segments. Each segment consists of a soft inflatable shell (internal pressure in range of 1.0-15.9 mBar) and a pair of antagonistic DE membranes (VHB 4905). Experimental testing of a single body segment is presented and the relationship between drive voltage, pneumatic pressure and active displacement is characterized. This demonstrates that pneumatic coupling of DE membranes induces complex non-linear electro-mechanical behaviour as drive voltage and pneumatic pressure are altered. Locomotion of a two-segment inchworm robot prototype with a passive length of 80 mm is presented. Artificial setae are included on the body shell to generate anisotropic friction for locomotion. A maximum locomotion speed of 4.1 mm/s was recorded at a drive frequency of 1.5 Hz, which compares favourably to biological counterparts. Future development of the soft inchworm robot are discussed including reflexive low-level control of individual segments.

  9. Electrical breakdown detection system for dielectric elastomer actuators

    Science.gov (United States)

    Ghilardi, Michele; Busfield, James J. C.; Carpi, Federico

    2017-04-01

    Electrical breakdown of dielectric elastomer actuators (DEAs) is an issue that has to be carefully addressed when designing systems based on this novel technology. Indeed, in some systems electrical breakdown might have serious consequences, not only in terms of interruption of the desired function but also in terms of safety of the overall system (e.g. overheating and even burning). The risk for electrical breakdown often cannot be completely avoided by simply reducing the driving voltages, either because completely safe voltages might not generate sufficient actuation or because internal or external factors might change some properties of the actuator whilst in operation (for example the aging or fatigue of the material, or an externally imposed deformation decreasing the distance between the compliant electrodes). So, there is the clear need for reliable, simple and cost-effective detection systems that are able to acknowledge the occurrence of a breakdown event, making DEA-based devices able to monitor their status and become safer and "selfaware". Here a simple solution for a portable detection system is reported that is based on a voltage-divider configuration that detects the voltage drop at the DEA terminals and assesses the occurrence of breakdown via a microcontroller (Beaglebone Black single-board computer) combined with a real-time, ultra-low-latency processing unit (Bela cape an open-source embedded platform developed at Queen Mary University of London). The system was used to both generate the control signal that drives the actuator and constantly monitor the functionality of the actuator, detecting any breakdown event and discontinuing the supplied voltage accordingly, so as to obtain a safer controlled actuation. This paper presents preliminary tests of the detection system in different scenarios in order to assess its reliability.

  10. First X-ray crystal structure and internal reference diffusion-ordered NMR spectroscopy study of the prototypical Posner reagent, MeCu(SPh)Li(THF)3.

    Science.gov (United States)

    Bertz, Steven H; Hardin, Richard A; Heavey, Thomas J; Jones, Daniel S; Monroe, T Blake; Murphy, Michael D; Ogle, Craig A; Whaley, Tara N

    2013-07-29

    Grow slow: The usual direct treatment of MeLi and CuSPh did not yield X-ray quality crystals of MeCu(SPh)Li. An indirect method starting from Me2CuLi⋅LiSPh and chalcone afforded the desired crystals by the slow reaction of the intermediate π-complex (see scheme). This strategy produced the first X-ray crystal structure of a Posner cuprate. A complementary NMR study showed that the contact ion pair was also the main species in solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Bioinspired actuated adhesive patterns of liquid crystalline elastomers.

    Science.gov (United States)

    Cui, Jiaxi; Drotlef, Dirk-Michael; Larraza, Iñigo; Fernández-Blázquez, Juan P; Boesel, Luciano F; Ohm, Christian; Mezger, Markus; Zentel, Rudolf; del Campo, Aránzazu

    2012-09-04

    Gecko-inspired arrays of micropillars made of a liquid crystalline elastomer display thermoswitchable adhesive behavior as a consequence of elongation changes caused by reorientation of the mesogens at the nematic-isotropic (N-I) phase transition. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Silicone elastomers with superior softness and dielectric properties

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin

    Dielectric elastomers (DEs) change their shape and size under a high voltage or reversibly generate a high voltage when deformed. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young’s ...

  13. Key value propositions in applications for dielectric elastomer actuators

    DEFF Research Database (Denmark)

    Lautrop, Asger; Elena, Maria; Poole, Alan

    2015-01-01

    This work identifies and clarifies tendencies in the performance metrics of dielectric elastomer actuators with respect to different application requirements. The study is based on real proposed applications and therefore not only highlights the properties in which DEA provides value, but also...

  14. Reversible large amplitude planar extension of soft elastomers

    DEFF Research Database (Denmark)

    Jensen, Mette Krog; Skov, Anne Ladegaard; Rasmussen, Henrik K.

    The newly developed planar elongation fixture, designed as an add-on to the filament stretch rheometer, is used to measure reversible large amplitude planar elongation on soft elastomers. The concept of the new fixture is to elongate an annulus by keeping the perimeter constant. The deformation...

  15. Use of VUV Radiation to Control Elastomer Seal Adhesion

    Science.gov (United States)

    deGroh, Henry C., III; Puleo, Bernadette J.; Waters, Deborah L.

    2013-01-01

    Due to their wide operating temperatures and low leakage rates, silicone elastomers are the only class of flight qualified elastomer materials that currently meet NASA's needs for various seal applications, which include docking and hatch seals for future space exploration vehicles. However, silicone elastomers are naturally sticky and exhibit sizeable adhesion when mated against metals and other silicone surfaces. This undesirable adhesion can make undocking spacecraft or opening a hatch problematic. Two approaches that can be used to reduce seal adhesion include use of grease or, application of low doses of atomic oxygen (AO). This paper investigates a third approach: the application of light doses of vacuum ultraviolet (VUV) radiation. Presented are the adhesion and leakage characteristics of S0383-70 silicone elastomer exposed to various VUV doses in the 115 to 200 nm wavelength range. The data indicate that adhesion is expected to be less than the target threshold maximum of 2 lb/in(exp2) after about 1 J/cm(exp2) of VUV exposure for seal-to-metal configurations and after 2 J/cm(exp2) for seal-to-seal configurations with no significant damage, or increase in seal leakage. This paper shows that VUV, without AO or grease, can be an effective means to reduce adhesion to the desired levels necessary for space seals with minimal change in seal leak rates.

  16. Silicone elastomer sling for rectal prolapse in cats

    Science.gov (United States)

    Corgozinho, Katia Barão; Belchior, Cristiane; de Souza, Heloisa Justen Moreira; Ferreira, Ana Maria; Resende, Carolina; Damico, Brandão; Cunha, Simone

    2010-01-01

    This study reports 2 cases of recurrent rectal prolapse secondary to anal abnormality in cats. In both cases the anus was wide, leading to a rectal mucosal prolapse during defecation. A silicone elastomer sling was introduced around the anus, and the rectal prolapse was definitively resolved. PMID:20676293

  17. Diffraction from relief gratings on a biomimetic elastomer cast

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero, Raphael A., E-mail: rguerrero@admu.edu.ph [Department of Physics, Ateneo de Manila University, Loyola Heights, Quezon City (Philippines); Aranas, Erika B. [Department of Physics, Ateneo de Manila University, Loyola Heights, Quezon City (Philippines)

    2010-10-12

    Biomimetic optical elements combine the optimized designs of nature with the versatility of materials engineering. We employ a beetle carapace as the template for fabricating relief gratings on an elastomer substrate. Biological surface features are successfully replicated by a direct casting procedure. Far-field diffraction effects are discussed in terms of the Fraunhofer approximation in Fourier space.

  18. Conductive Elastomers for Stretchable Electronics, Sensors and Energy Harvesters

    Directory of Open Access Journals (Sweden)

    Jin-Seo Noh

    2016-04-01

    Full Text Available There have been a wide variety of efforts to develop conductive elastomers that satisfy both mechanical stretchability and electrical conductivity, as a response to growing demands on stretchable and wearable devices. This article reviews the important progress in conductive elastomers made in three application fields of stretchable technology: stretchable electronics, stretchable sensors, and stretchable energy harvesters. Diverse combinations of insulating elastomers and non-stretchable conductive materials have been studied to realize optimal conductive elastomers. It is noted that similar material combinations and similar structures have often been employed in different fields of application. In terms of stretchability, cyclic operation, and overall performance, fields such as stretchable conductors and stretchable strain/pressure sensors have achieved great advancement, whereas other fields like stretchable memories and stretchable thermoelectric energy harvesting are in their infancy. It is worth mentioning that there are still obstacles to overcome for the further progress of stretchable technology in the respective fields, which include the simplification of material combination and device structure, securement of reproducibility and reliability, and the establishment of easy fabrication techniques. Through this review article, both the progress and obstacles associated with the respective stretchable technologies will be understood more clearly.

  19. Centrifugal forming and mechanical properties of silicone-based elastomers for soft robotic actuators

    Science.gov (United States)

    Kulkarni, Parth

    This thesis describes the centrifugal forming and resulting mechanical properties of silicone-based elastomers for the manufacture of soft robotic actuators. This process is effective at removing bubbles that get entrapped within 3D-printed, enclosed molds. Conventional methods for rapid prototyping of soft robotic actuators to remove entrapped bubbles typically involve degassing under vacuum, with open-faced molds that limit the layout of formed parts to raised 2D geometries. As the functionality and complexity of soft robots increase, there is a need to mold complete 3D structures with controlled thicknesses or curvatures on multiples surfaces. In addition, characterization of the mechanical properties of common elastomers for these soft robots has lagged the development of new designs. As such, relationships between resulting material properties and processing parameters are virtually non-existent. One of the goals of this thesis is to provide guidelines and physical insights to relate the design, processing conditions, and resulting properties of soft robotic components to each other. Centrifugal forming with accelerations on the order of 100 g's is capable of forming bubble-free, true 3D components for soft robotic actuators, and resulting demonstrations in this work include an aquatic locomotor, soft gripper, and an actuator that straightens when pressurized. Finally, this work shows that the measured mechanical properties of 3D geometries fabricated within enclosed molds through centrifugal forming possess comparable mechanical properties to vacuumed materials formed from open-faced molds with raised 2D features.

  20. Evaluation of the performance of three elastomers for non-lethal projectile applications

    Directory of Open Access Journals (Sweden)

    Thota N.

    2015-01-01

    Full Text Available Less lethal kinetic ammunitions with soft noses such as eXact iMpact 1006, National Sports Spartan and B&T have been commonly used by military and law enforcement officers in the situations where lethal force is not warranted. In order to explore new materials to be used as nose in such ammunitions, a scholastic study using finite element simulations has been carried out to evaluate the effectiveness of two rubber like elastomers and a polyolefinic foam (low density, highly compressible, stiff and closed cell type of thermos plastic elastomer. State-of-the art thorax surrogate MTHOTA has been employed for the evaluation of blunt thoracic trauma. Force-rigid wall method was employed for the evaluation of head damage curves for each material. XM 1006 has been used as the benchmark projectile for the purpose of comparison. Both blunt thoracic trauma and head damage criterion point of view, both rubbers (R1 and R2 have yielded high values of VCmax and peak impact force. Polyolefinic foam (F1 considered in the study has yielded very promising VCmax values and very less peak impact force when compared with those of bench mark projectile XM 1006.

  1. Zinc chelates as new activators for sulphur vulcanization of acrylonitrile-butadiene elastomer

    Directory of Open Access Journals (Sweden)

    2009-04-01

    Full Text Available The goal of this work was to apply several zinc chelates as activators for sulphur vulcanization of acrylonitrilebutadiene elastomer (NBR, in order to find alternatives for the conventionally used zinc oxide. In this article, we discuss the effects of different zinc complexes on the cure characteristics, crosslinks distribution in the elastomer network and mechanical properties of acrylonitrile-butadiene rubber. Zinc chelates seem to be good substitutes for zinc oxide as activators for sulphur vulcanization of NBR rubber, without detrimental effects on the crosslinking process and physical properties of the obtained vulcanizates. Moreover, application of zinc complexes allows to reduce the amount of zinc ions in rubber compounds by 40% compared to conventionally crosslinked vulcanizates with zinc oxide. It is a very important ecological goal since zinc oxide is classified as toxic to aquatic species and its amount in rubber products must be reduced below 2.5% at least. From a technological point of view it is a very important challenge.

  2. Evaluation of the performance of three elastomers for non-lethal projectile applications

    Science.gov (United States)

    Thota, N.; Epaarachchi, J.; Lau, K. T.

    2015-09-01

    Less lethal kinetic ammunitions with soft noses such as eXact iMpact 1006, National Sports Spartan and B&T have been commonly used by military and law enforcement officers in the situations where lethal force is not warranted. In order to explore new materials to be used as nose in such ammunitions, a scholastic study using finite element simulations has been carried out to evaluate the effectiveness of two rubber like elastomers and a polyolefinic foam (low density, highly compressible, stiff and closed cell type of thermos plastic elastomer). State-of-the art thorax surrogate MTHOTA has been employed for the evaluation of blunt thoracic trauma. Force-rigid wall method was employed for the evaluation of head damage curves for each material. XM 1006 has been used as the benchmark projectile for the purpose of comparison. Both blunt thoracic trauma and head damage criterion point of view, both rubbers (R1 and R2) have yielded high values of VCmax and peak impact force. Polyolefinic foam (F1) considered in the study has yielded very promising VCmax values and very less peak impact force when compared with those of bench mark projectile XM 1006.

  3. Preparation, crystal structure, spectrographic characterization, thermal and third-order nonlinear optical properties of benzyltriethylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) for all-optical switching applications

    Science.gov (United States)

    Wang, X. Q.; Ren, Q.; Chen, J. W.; Yu, W. T.; Fang, H. L.; Li, T. B.; Cong, H. J.; Liu, X. T.; Zhu, L. Y.; Zhang, G. H.; Xu, D.

    2011-05-01

    The preparation and crystal structure of a novel nonlinear optical organometallic crystal, benzyltriethylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) (BTEAADT), are described. The crystal was characterized by elemental analyses, infrared and X-ray powder diffraction spectroscopy, thermal analysis and optical absorption. A typical highly optical quality single crystal with dimensions of about 30 × 3 × 3 mm 3 has been grown from an acetone solution by the solvent evaporation method. The specific heat of the crystal was measured to be 692.0 J mol -1 K -1 at 300 K. The thin film of BTEAADT doped into poly(methyl methacrylate) (PMMA) with a concentration of 1 wt% was prepared using spin-coating method. The linear properties of the thin film were investigated by a prism coupler. The third-order nonlinear optical properties of BTEAADT doped PMMA film was investigated by using the laser Z-scan technique with 20 ps pulses at 1064 nm. A large negative nonlinear refraction and no nonlinear absorption have been observed. The refractive index and the thickness of the film are 1.4682 and 1.15 μm, respectively. The nonlinear refractive index is calculated to be -3.978 × 10 -15m 2/W for the film. At the same time, the nonlinear absorption coefficient is 0. Two figures of merit, W and T of the film, were calculated to be |W| = 1.07 > 1, |T| = 0 optical switching.

  4. ASSESSMENT OF THE INFLUENCE OF RADIATION AND DEFORMATION ON THE ELASTOMER DETERIORATION BY USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Jasminka Bonato

    2017-01-01

    Full Text Available Elastomers belong to the group of polymer materials and they have an important role as technical material in the shipbuilding industry. The radiation crosslinking of elastomers shows significant advantages over chemical crosslinking. It can improve mechanical strength, resistance to chemicals and insulation properties of elastomers. An undesirable side reaction, which can occur during radiation, is the degradation process. This results in cracks breaking, chemical disintegration and reduction of mechanical properties of elastomers. In this paper fuzzy logic is used to estimate the influence of radiation and deformation on the behavior of elastomer samples. A Gaussian model is created according to both the experts' experience and the measuring data. The results of the model are calculated by using the Normalized Roth Mean Square Error (NRMSE and the Roth Mean Square Error (RMSE. The so developed model gives new conceptions, which offer a possibility to improve the application of elastomer materials.

  5. Stretch dependence of the electrical breakdown strength and dielectric constant of dielectric elastomers

    Science.gov (United States)

    Tröls, Andreas; Kogler, Alexander; Baumgartner, Richard; Kaltseis, Rainer; Keplinger, Christoph; Schwödiauer, Reinhard; Graz, Ingrid; Bauer, Siegfried

    2013-10-01

    Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910™ from 3M™, and of the natural rubber ZruElast™ A1040™ from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting.

  6. Silicone elastomers with high dielectric permittivity and high dielectric breakdown strength based on dipolar copolymers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Daugaard, Anders Egede

    2014-01-01

    Dielectric elastomers (DES) are a promising new transducer technology, but high driving voltages limit their current commercial potential. One method used to lower driving voltage is to increase dielectric permittivity of the elastomer. A novel silicone elastomer system with high dielectric......-4-nitrobenzene. Here, a high increase in dielectric permittivity (similar to 70%) was obtained without compromising other favourable DE properties such as elastic modulus, gel fraction, dielectric loss and electrical breakdown strength. © 2014 Elsevier Ltd. All rights reserved....

  7. Enhancement of dielectric permittivity by incorporating PDMS-PEG multiblock copolymers in silicone elastomers

    DEFF Research Database (Denmark)

    A Razak, Aliff Hisyam; Szabo, Peter; Skov, Anne Ladegaard

    2015-01-01

    A silicone elastomer from PDMS-PEG multiblock copolymer has been prepared by use of silylation reactions for both copolymer preparation and crosslinking. The dielectric and mechanical properties of the silicone elastomers were carefully investigated, as well as the morphology of the elastomers wa...... to a significantly increased dielectric permittivity. The conductivity also remained low due to the resulting discontinuity in PEG within the silicone matrix....

  8. Design of Elastomer Structure to Facilitate Incorporation of Expanded Graphite in Silicones Without Compromising Electromechanical Integrity

    DEFF Research Database (Denmark)

    Hassouneh, Suzan Sager; Daugaard, Anders Egede; Skov, Anne Ladegaard

    2015-01-01

    The development of elastomer materials with a high dielectric permittivity has attracted increased interest over the past years due to their use in, for example, dielectric elastomers. For this particular use, both the electrically insulating properties - as well as the mechanical properties......-functional crosslinker, which allows for development of a suitable network matrix. The dielectric permittivity was increased by almost a factor of 4 compared to a benchmark silicone elastomer....

  9. Tuning of a cavity in a silicon photonic crystal by thermal expansion of an elastomeric infill

    NARCIS (Netherlands)

    Erdamar, A.K.; Van Leest, M.M.; Picken, S.J.; Caro, J.

    2011-01-01

    We use an elastomer as infill material for a photonic crystal. As a result of the thermal-expansion-induced strongly negative thermal optical coefficient, this material is highly suitable for thermal tuning of the transmission of a cavity. This is demonstrated by global infilling of a hole-type

  10. Effects of magnetic order on the superconducting length scales and critical fields in single crystal ErNi2B2C

    DEFF Research Database (Denmark)

    Gammel, P.L.; Barber, B.P.; Ramirez, A.P.

    1999-01-01

    The flux line form factor in small angle neutron scattering and transport data determines the superconducting length scares and critical fields in single crystal ErNi2B2C. For H parallel to c, the coherence length xi increases and the penetration depth lambda decreases when crossing T-N = 6.0 K...

  11. Detailed optical spectroscopy of hybridization gap and hidden-order transition in high-quality URu2Si2 single crystals

    NARCIS (Netherlands)

    Bachar, N.; Stricker, D.; Muleady, S.; Wang, K.; Mydosh, J.A.; Huang, Y.K.; van der Marel, D.

    2016-01-01

    We present a detailed temperature and frequency dependence of the optical conductivity measured on clean high-quality single crystals of URu2Si2 of ac− and ab-plane surfaces. Our data demonstrate the itinerant character of the narrow 5f bands, becoming progressively coherent as the temperature is

  12. The Ordered K2NiF4-type Structure of Mixed Crystals La2-xSrxLi1/2Co1/2O4 (x

    NARCIS (Netherlands)

    Warda, S.A.; Massa, Werner; Reinen, Dirk; Hu, Zhiwei; Kaindl, Günter; Groot, F.M.F. de

    1999-01-01

    Solids of the composition La2-xSrxLi1/2Co1/2O4 (x50, x=0.2) crystallize in a superstructure of the K2NiF4 lattice with a doubled unit cell in the (001) plane (space group Ammm; a=b=J2a0), caused by cation ordering between lithium and cobalt on the octahedral sites. The electronic structure of the

  13. Fabrication of thermoplastic polyester elastomer/layered zinc hydroxide nitrate nanocomposites with enhanced thermal, mechanical and combustion properties

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Wei; Ma, Liyan; Song, Lei; Hu, Yuan, E-mail: yuanhu@ustc.edu.cn

    2013-08-15

    The objective of this study is to explore the potential of layered zinc hydroxide nitrate modified with sodium benzoate as nanoparticle in thermoplastic polyester elastomer (TPEE). The organically modified zinc hydroxide nitrate was compounded with TPEE using solution blending method. The nanocomposite structure was characterized by means of X-ray diffraction and transmission electron microscopy. The results showed that the nanoparticle was homogenously dispersed in TPEE matrix, and partially exfoliated structure was formed. The thermal behavior, mechanical and thermal combustion properties of the novel nanocomposite were studied respectively through differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA) and microscale combustion calorimeter (MCC). For the nanocomposite containing 7 wt% nanoparticle, the crystallization temperature evaluated by DSC was increased by 10 °C. The storage modulus at −95 °C measured by DMA was improved by around 26%. The heat release capacity (an indicator of a material fire hazard) from MCC testing was reduced by about 56% (compared to the results of neat TPEE). - Highlights: • We prepare zinc hydroxide nitrate modified by sodium benzoate (SB-ZHN). • We prepare and characterize thermoplastic polyester elastomer/SB-ZHN nanocomposites. • We investigate the thermal and combustion properties of the nanocomposites. • We study the thermodynamic properties of the nanocomposites.

  14. Synthesis and electromechanical characterization of a new acrylic dielectric elastomer with high actuation strain and dielectric strength

    Science.gov (United States)

    Hu, Wei; Niu, Xiaofan; Yang, Xinguo; Zhang, Naifang; Pei, Qibing

    2013-04-01

    Dielectric Elastomers (DEs) can be actuated under high electric field to produce large strains. Most high-performing DE materials such as the 3M™ VHB™ membranes are commercial products designed for industrial pressure-sensitive adhesives. The limited knowledge of the exact chemical structures of these commercial materials has made it difficult to understand the relationship between molecular structures and electromechanical properties. In this work, new acrylic elastomers based on n-butyl acrylate and acrylic acid were synthesized from monomer solutions by UV-initiated bulk polymerization. The new acrylic copolymers have a potential to obtain high dielectric constant, actuation strain, dielectric strength, and a high energy density. Silicone and ester oligomer diacrylates were also added onto the copolymer structures to suppress crystallization and to crosslink the polymer chains. Four acrylic formulations were developed with different amounts of acrylic acid. This gives a tunable stiffness, while the dielectric constant is varied from 4.3 to 7.1. The figure-of-merit performance of the best formulation is 186 % area strain, 222 MV/m of dielectric strength, and 2.7 MJ/m3 of energy density. To overcome electromechanical instability, different prestrain ratios were investigated, and under the optimized prestrain, the material has a lifetime of thousands of cycles at 120 % area strain.

  15. Investigation on the growth, spectral, lifetime, mechanical analysis and third-order nonlinear optical studies of L-methionine admixtured D-mandelic acid single crystal: A promising material for nonlinear optical applications

    Science.gov (United States)

    Jayaprakash, P.; Sangeetha, P.; Kumari, C. Rathika Thaya; Caroline, M. Lydia

    2017-08-01

    A nonlinear optical bulk single crystal of L-methionine admixtured D-mandelic acid (LMDMA) has been grown by slow solvent evaporation technique using water as solvent at ambient temperature. The crystallized LMDMA single crystal subjected to single crystal X-ray diffraction study confirmed monoclinic system with the acentric space group P21. The FTIR analysis gives information about the modes of vibration in the various functional groups present in LMDMA. The UV-visible spectral analysis assessed the optical quality and linear optical properties such as extinction coefficient, reflectance, refractive index and from which optical conductivity and electric susceptibility were also evaluated. The frequency doubling efficiency was observed using Kurtz Perry powder technique. A multiple shot laser was utilized to evaluate the laser damage threshold energy of the crystal. Discrete thermodynamic properties were carried out by TG-DTA studies. The hardness, Meyer's index, yield strength, elastic stiffness constant, Knoop hardness, fracture toughness and brittleness index were analyzed using Vickers microhardness tester. Layer growth pattern and the surface defect were examined by chemical etching studies using optical microscope. Fluorescence emission spectrum was recorded and lifetime was also studied. The electric field response of crystal was investigated from the dielectric studies at various temperatures at different frequencies. The third-order nonlinear optical response in LMDMA has been investigated using Z-scan technique with He-Ne laser at 632.8 nm and nonlinear parameters such as refractive index (n2), absorption coefficient (β) and susceptibility (χ3) investigated extensively for they are in optical phase conjucation, high-speed optical switches and optical dielectric devices.

  16. Preparation, crystal growth, characterization, thermal and third-order nonlinear optical properties of ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) for all-optical switching

    Science.gov (United States)

    Wang, X. Q.; Ren, Q.; Sun, J.; Fan, H. L.; Li, T. B.; Liu, X. T.; Zhang, G. H.; Zhu, L. Y.; Xu, D.

    2011-06-01

    A novel organometallic third-order nonlinear optical crystal: ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) (ETPPADT) has been prepared, and large optical-quality single crystals have been grown by the solvent evaporation method. Its structural, optical and physicochemical properties are characterized by elemental analyses, UV-Vis-NIR transmission, infrared spectroscopy and thermal analysis. The thin films of ETPPADT doped into poly(methyl methacrylate) (PMMA) with a concentration of 1 wt% have been prepared using spin-coating method. The linear refractive index and the thickness of the thin films were measured by a prism coupler. The third-order nonlinear optical properties of the films have been investigated using Z-scan technique at the wavelength of 1064 nm with laser duration of 20 ps, which reveal that the composited films exhibit large negative nonlinear refractive indices about 4×10 -10 esu and no nonlinear absorption. The influence of thickness of the film and the incident laser intensity on the third-order optical nonlinearities have been investigated. Two figures of merit, W and T, have been calculated to be | W|≅120≫1 and | T|=0≪1, respectively. All the results show that ETPPADT crystal has potential application on all-optical switching.

  17. Modified and Unmodified Zinc Oxide as Coagent in Elastomer Compounds

    Directory of Open Access Journals (Sweden)

    Kołodziejczak-Radzimska Agnieszka

    2014-09-01

    Full Text Available The aim of this work was to study the activity of unmodified and modified ZnO in the peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR and ethylene-propylene copolymer (EPM. In the first step, zinc oxide was obtained by emulsion precipitation. Maleic acid was introduced onto the surface of ZnO using an in situ method. The unmodified and modified zinc oxide was characterized using dispersive and morphological analysis, BET surface area analysis, and elemental, spectroscopic and thermal analysis. In the second stage of the research, the ZnO/MA systems were incorporated into the structure of elastomer compounds improving the kinetic and mechanical properties of vulcanizates. The proposed modification method had a favorable effect on the physicochemical properties of the zinc oxide and on the kinetic and mechanical properties of the vulcanizates. This study demonstrated that modification of zinc oxide by maleic acid is a promising technique.

  18. Mimicking biological stress–strain behaviour with synthetic elastomers

    Science.gov (United States)

    Vatankhah-Varnosfaderani, Mohammad; Daniel, William F. M.; Everhart, Matthew H.; Pandya, Ashish A.; Liang, Heyi; Matyjaszewski, Krzysztof; Dobrynin, Andrey V.; Sheiko, Sergei S.

    2017-09-01

    Despite the versatility of synthetic chemistry, certain combinations of mechanical softness, strength, and toughness can be difficult to achieve in a single material. These combinations are, however, commonplace in biological tissues, and are therefore needed for applications such as medical implants, tissue engineering, soft robotics, and wearable electronics. Present materials synthesis strategies are predominantly Edisonian, involving the empirical mixing of assorted monomers, crosslinking schemes, and occluded swelling agents, but this approach yields limited property control. Here we present a general strategy for mimicking the mechanical behaviour of biological materials by precisely encoding their stress–strain curves in solvent-free brush- and comb-like polymer networks (elastomers). The code consists of three independent architectural parameters—network strand length, side-chain length and grafting density. Using prototypical poly(dimethylsiloxane) elastomers, we illustrate how this parametric triplet enables the replication of the strain-stiffening characteristics of jellyfish, lung, and arterial tissues.

  19. Magnetic force induced tristability for dielectric elastomer actuators

    Science.gov (United States)

    Li, Xin-Qiang; Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2017-10-01

    This paper presents a novel dielectric elastomer actuator (DEA) with three stable states. By introducing magnetic forces and coupling them with two cone dielectric elastomer (DE) films, an inherent tristability for the DEA is obtained with a compact design. It is easy to switch between the three stable states by controlling the voltages applied to the DE films. A theoretical model of the system’s potential energy that contains the free energy of the DEs and the potential energy of the applied magnetic field was developed for the tristable mechanism. The experimental results demonstrate that controllable transitions between the three stable states can be achieved with this design by applying over-critical voltages to the various DE films. The maximum dynamic range of the DEA can exceed 53.8% of the total length of the device and the DE’s creep speed was accelerated under the action of the magnetic field.

  20. Dielectric elastomer fingers for versatile grasping and nimble pinching

    Science.gov (United States)

    Lau, Gih-Keong; Heng, Kim-Rui; Ahmed, Anansa S.; Shrestha, Milan

    2017-05-01

    Boneless soft robotic fingers cannot apply concentrated forces to pinch a delicate object. This letter reports a three-dimensional design of dielectric elastomer fingers with higher flexural stiffness and close to 90° voltage-controllable bending for object gripping and pinching. It makes use of tension arch flexures to elevate a pre-stretched dielectric elastomer actuator (DEA) into a roof shape and thus magnifies the tension-induced moment, 40 times higher than a flat DEA does, to bend a stiff base frame. Such fingers make normally close-grippers to lift a payload 8-9 times their weight. They also make normally open grippers that pinch a highly deformable raw egg yolk.

  1. Strong dielectric-elastomer grippers with tension arch flexures

    Science.gov (United States)

    Heng, Kim-Rui; Ahmed, Anansa S.; Shrestha, Milan; Lau, Gih-Keong

    2017-04-01

    Soft grippers based on dielectric elastomer actuator (DEA) are usually too flimsy to perform the task of pick and place on a heavier object given their low payload capacity. This work developed a new design of DEA unimorph consists of a flexible frame holding at a DEA on the discrete support by a stiffer spine-like flexure of 380μm thick Polyvinyl chloride (PVC) sheet. It finds an equilibrium of curling up when the DEA's pre-stretch is partially released; it can electrically unfolds upon a voltage application. This dielectric elastomer unimorph of 3 grams produced a maximum voltage induced bending of close to 90° and a maximum voltage-induced blocked force of up to 168mN. Given their higher stiffness and large actuation, these 3-D shaped and strengthened DEA unimorphs can make stronger grippers for passive grasping and active pinching.

  2. Application of speckle shearing interferometry to the evaluation of creep strain in elastomers

    Science.gov (United States)

    Pascual-Francisco, Juan Benito; Michtchenko, Alexandre; Susarrey-Huerta, Orlando; Barragán-Pérez, Omar; Ortiz-Gonzáles, Antonio de Jesús

    2017-10-01

    In this paper, authors present a new application of speckle shearing interferometry (shearography) to a phenomenon known as creep compliance, which is an important mechanical property of viscoelastic materials. Two different sealing elastomers were tested in a short-term creep experiment, applying a constant tensile stress to a specimen. An experimental in-plane shearography setup was implemented to measure directly the in-plane creep strains produced in the tested object. In order to show the effectiveness of shearography for the assessment of this mechanical property, results were compared to that obtained with an equipment of Digital Image Correlation (DIC). It was demonstrated that shearography can be potentially and successfully applied to the creep analysis of these kind of materials. Finally, advantages and limitations of this measurement method are discussed.

  3. Stretchable and waterproof elastomer-coated organic photovoltaics for washable electronic textile applications

    Science.gov (United States)

    Jinno, Hiroaki; Fukuda, Kenjiro; Xu, Xiaomin; Park, Sungjun; Suzuki, Yasuhito; Koizumi, Mari; Yokota, Tomoyuki; Osaka, Itaru; Takimiya, Kazuo; Someya, Takao

    2017-10-01

    Textile-compatible photovoltaics play a crucial role as a continuous source of energy in wearable devices. In contrast to other types of energy harvester, they can harvest sufficient electricity (on the order of milliwatts) for wearable devices by utilizing the cloth itself as the platform for photovoltaics. Three features are important for textile-compatible photovoltaics, namely environmental stability, sufficient energy efficiency and mechanical robustness. However, achieving these simultaneously remains difficult because of the low gas barrier properties of ultrathin superstrates and substrates. Here, we report on ultraflexible organic photovoltaics coated on both sides with elastomer that simultaneously realize stretchability and stability in water whilst maintaining a high efficiency of 7.9%. The efficiency of double-side-coated devices decreases only by 5.4% after immersion in water for 120 min. Furthermore, the efficiency of the devices remains at 80% of the initial value even after 52% mechanical compression for 20 cycles with 100 min of water exposure.

  4. Numerical analysis and experimental verification of elastomer bending process with different material models

    Directory of Open Access Journals (Sweden)

    Kut Stanislaw

    2016-01-01

    Full Text Available The article presents the results of tests in order to verifying the effectiveness of the nine selected elastomeric material models (Neo-Hookean, Mooney with two and three constants, Signorini, Yeoh, Ogden, Arruda-Boyce, Gent and Marlow, which the material constants were determined in one material test - the uniaxial tension testing. The convergence assessment of nine analyzed models were made on the basis of their performance from an experimental bending test of the elastomer samples from the results of numerical calculations FEM for each material models. To calculate the material constants for the analyzed materials, a model has been generated by the stressstrain characteristics created as a result of experimental uniaxial tensile test with elastomeric dumbbell samples, taking into account the parameters received in its 18th cycle. Using such a calculated material constants numerical simulation of the bending process of a elastomeric, parallelepipedic sampleswere carried out using MARC / Mentat program.

  5. Polydimethylsiloxane elastomer injection in the management of the patulous eustachian tube.

    Science.gov (United States)

    Mackeith, S A C; Bottrill, I D

    2016-09-01

    To determine the effectiveness of augmentation surgery using polydimethylsiloxane elastomer injection for the management of patulous eustachian tube. All patients were treated with eustachian tube injection augmentation performed via a combined transnasal-transoral endoscopic approach. Clinical presentation, volume of injection, complications and initial response were all prospectively recorded. Longer-term follow up was conducted through structured telephone interviews using previously described patient-reported outcome measures. Overall, 8 of 11 patients (73 per cent) derived complete or significant symptom improvement; 1 patient had significant improvements but was dissatisfied, and in 2 patients the symptoms were unchanged. The eight satisfied patients showed improvement in their quality-of-life scores. This study describes an effective treatment option for patulous eustachian tube. Unlike many prior published reports, previously described patient-reported outcome measures were utilised in order to allow more direct comparison.

  6. Unique load dependency of static friction of wrinkles formed on textile-embedded elastomer surfaces

    Directory of Open Access Journals (Sweden)

    Takuya Ohzono

    2017-05-01

    Full Text Available We investigate, over a wide range of normal loads, the static friction on textile-embedded elastomer surfaces that show hierarchical microstructures tunable by adjusting internal in-plane compressive strains. These microstructures, under compression, comprise small protrusions on textile fibers and surface-buckling-based wrinkles with periodicities on the order of tens and hundreds of microns, respectively. The static-friction coefficients unexpectedly increase under normal loads. This unique property, associated with the transition from partial to almost total contact, depends on both loads and the aspect ratio of the wrinkles. Wrinkle-structure tuning modulates load-dependent friction’s nonlinearity, which may augment the tribological performance of elastomeric materials.

  7. Robust hybrid elastomer/metal-oxide superhydrophobic surfaces

    OpenAIRE

    Hoshian, Sasha; Jokinen, Ville; Franssila, Sami

    2016-01-01

    We introduce a new type of hybrid material: a nanostructured elastomer covered by a hard photoactive metal-oxide thin film resembling the exoskeleton of insects. It has extreme water repellency and fast self-recovery after damage. A new fabrication method for replicating high aspect ratio, hierarchical re-entrant aluminum structures into polydimethylsiloxane (PDMS) is presented. The method is based on a protective titania layer deposited by atomic layer deposition (ALD) on the aluminum templa...

  8. Biomimetic Underwater Robots Based on Dielectric Elastomer Actuators

    OpenAIRE

    Shintake, Jun; Shea, Herbert; Floreano, Dario

    2016-01-01

    Dielectric elastomer actuators (DEAs), a soft actuator technology, hold great promise for biomimetic underwater robots. The high-voltages required to drive DEAs can however make them challenging to use in water. This paper demonstrates a method to create DEA-based biomimetic swimming robots that operate reliably even in conductive liquids. We ensure the insulation of the high-voltage DEA electrodes without degrading actuation performance by laminating silicone layers. A fish and a jellyfish w...

  9. Interfacial Stress Transfer in an Aramid Reinforced Thermoplastic Elastomer

    OpenAIRE

    Coffey, Austin

    2007-01-01

    Abstract The interfacial micromechanics of Twaron 2200 aramid fibers in an engineering thermoplastic elastomer (Pebax 7033, polyether amide block co-polymer) has been investigated by determining the distribution of interfacial shear stress along fibers in single-fiber model composites using Raman spectroscopy. The effects of various fiber surface treatments on the interfacial shear stress and fragmentation of the aramid fibers are discussed. The fiber average stress in...

  10. Micropatterning on silicon elastomer (PDMS) with deep UVs

    OpenAIRE

    sprotocols

    2015-01-01

    Authors: Nicolas CARPI, Matthieu PIEL, Ammar Azioune, Damien Cuvelier & Jenny Fink ### Abstract This protocol describes a technique to imprint adhesive micropatterns on silicon elastomers like PDMS (poly-dimethyl siloxane). The micropatterns are stable for days (depending on the cell type) and regions outside the patterns prevent cell attachment. This technique is fast and easy and can be useful to combine cell stretching and micro-patterning. ### Introduction This protoco...

  11. Characteristics and utilization of thermoplastic elastomers (TPE)-an overview

    Energy Technology Data Exchange (ETDEWEB)

    Roestamsjah [R and D Center for Applied Chemistry, Indonesian Inst. of Sciences (Indonesia)

    1998-10-01

    The unique feature of thermoplastic elastomer, the combining of processing characteristics of thermoplastics with the physical properties of vulcanized rubber is reviewed. Highlights of TPE and its characteristics is aimed to generate interest in TPE, where SANS technique will be utilized for its characterization. The topics discussed include rubber elasticity, state of aggregation of polymers, microseparation in block copolymer system, application of TPE, and finally some notes in developing interest in TPE and SANS in Indonesia. (author)

  12. Towards liquid crystalline elastomer optically tunable photonic microstructures

    Science.gov (United States)

    Nocentini, S.; Martella, D.; Parmeggiani, C.; Zanotto, S.; Wiersma, D. S.

    2016-09-01

    In this paper we investigate the potentials of liquid crystalline elastomer microstructures for the realization of optically tunable photonic microstructures. While certain limitations regarding the compromise between feature size and structure warping have been observed, it turns out that the simultaneous presence of a refractive index tuning effect and of a shape tuning effect intrinsic to the LCE material can be harnessed to design tunable photonic devices with unique behavior.

  13. CREATING ACTIVATING SYSTEMS FOR THE EFFICIENT VULCANIZATION OF ELASTOMERS

    OpenAIRE

    O. V. Karmanova; L. V. Popova; O. V. Poimenova; I. K. Gusev

    2014-01-01

    Results of the study vulcanization of polydienes were presented. Vulcanization activators role in the formation of the actual curing agents and the formation of the spatial structure of the vulcanizates was considered. It is shown that to be effective requires the use of sulfur-vulcanization of zinc-containing vulcanization activators with a developed surface, capable of uniformly dispersed in a medium rubber. Activating sulfur vulcanization system elastomers as alloys of zinc oxide with ...

  14. Degradation of elastomer by heat and/or radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Masayuki [Advanced Research Institute for Science and Engineering, Waseda University, 51-Goukan, 10F 08, 3-4-1 Ookubo, Shinjuku-Ku, Tokyo 169-8555 (Japan)], E-mail: masayuki@kurenai.waseda.jp

    2007-12-15

    This article studied various problems on the degradation of elastomers by heat and/or radiation. Three kinds of elastomers were irradiated and evaluated by the radiation resistant property using the measurement of tensile test. The fluorine containing elastomer, which has excellent heat resistant properties, was found to be less durable for irradiation than ethylene-propylene-diene (EPDM) elastomer. Ten kinds of different compounding formulas of EPDM were prepared to investigate whether the compounding for heat resistant has durability for irradiation. The thermal exposure was performed in an air oven. The duration of thermal exposure at 140 deg. C was 384 h. The irradiation condition was 5.0 kGy/h at 70 deg. C, and the total dose was 0.9 MGy. Elongation retained was taken for the evaluation of the stability. It was found that the formulas for improving the thermal stability did not bring radiation resistant of samples in the experiment. The rate constant of the increase in C=O concentration by heat and radiation was measured and defined as k{sub c}(h) and k{sub c}(r), respectively. The rate constant of that under the combined addition of the heat and the radiation is expressed as k{sub c}(h + r). Eq. was obtained by the experiment and it was found that there is a synergistic relationship between heat and radiation on the increase in C=O concentration (1)k{sub c}(h+r)>k{sub c}(h)+k(r). Similar relationship was observed on the rate of decrease in ultimate elongation of a certain EPDM.

  15. Characteristics of Elastomer Seals Exposed to Space Environments

    Science.gov (United States)

    Daniels, Christopher C.; deGroh, Henry, III; Dunlap, Patrick H., Jr.; Finkbeiner, Joshua R.; Steinetz, Bruce M.; Bastrzyk, Marta B.; Oswald, Jay J.; Banks, Bruce A.; Dever, Joyce A.; Miller, Sharon K.; hide

    2008-01-01

    A universal docking and berthing system is being developed by the National Aeronautics and Space Administration (NASA) to support all future space exploration missions to low-Earth orbit (LEO), to the Moon, and to Mars. The Low Impact Docking System (LIDS) is being designed to operate using a seal-on-seal configuration in numerous space environments, each having unique exposures to temperature, solar radiation, reactive elements, debris, and mission duration. As the LIDS seal is likely to be manufactured from an elastomeric material, performance evaluation of elastomers after exposure to atomic oxygen (AO) and ultraviolet radiation (UV) was conducted, of which the work presented herein was a part. Each of the three candidate silicone elastomer compounds investigated, including Esterline ELA-SA-401, and Parker Hannifin S0383-70 and S0899-50, was characterized as a low outgassing compound, per ASTM E595, having percent total mass loss (TML) less than 1.0 percent and collected volatile condensable materials (CVCM) less than 0.1 percent. Each compound was compatible with the LIDS operating environment of -50 to 50 C. The seal characteristics presented include compression set, elastomer-to-elastomer adhesion, and o-ring leakage rate. The ELA-SA-401 compound had the lowest variation in compression set with temperature. The S0383-70 compound exhibited the lowest compression set after exposure to AO and UV. The adhesion for all of the compounds was significantly reduced after exposure to AO and was further decreased after exposure to AO and UV. The leakage rates of o-ring specimens showed modest increases after exposure to AO. The leakage rates after exposure to AO and UV were increased by factors of up to 600 when compared to specimens in the as-received condition.

  16. Mechanically Reinforced Skin-Electronics with Networked Nanocomposite Elastomer.

    Science.gov (United States)

    Han, Seungyong; Kim, Min Ku; Wang, Bo; Wie, Dae Seung; Wang, Shuodao; Lee, Chi Hwan

    2016-12-01

    Mechanically reinforced skin-electronics are presented by exploiting networked nanocomposite elastomers where high quality metal nanowires serve as conducting paths. Theoretical and experimental studies show that the established skin-electronics exhibit superior mechanical enhancements against crack and delamination phenomena. Device applications include a class of biomedical devices that offers the ability of thermotherapeutic stimulation and electrophysiological monitoring, all via the skin. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Compatibility Studies on Elastomers and Polymers with Ethanol Blended Gasoline

    OpenAIRE

    Dhaliwal, J S; M. S. Negi; G. S. Kapur; Shashi Kant

    2014-01-01

    This paper reports the compatibility studies of 10% ethanol blended gasoline (E10) with four types of elastomer materials, namely, Neoprene rubber, Nitrile rubber, hydrogenated Nitrile butadiene rubber (HNBR), and Polyvinyl chloride/Nitrile butadiene rubber blend (PVC/NBR), and two types of plastic materials, namely, Nylon-66 and Polyoxymethylene (Delrin). These materials have applications in automotives as engine seals, gaskets, fuel system seals and hoses, and so forth. Two types of the eth...

  18. Evaluation of a Conductive Elastomer Seal for Spacecraft

    Science.gov (United States)

    Daniels, Christopher C.; Mather, Janice L.; Oravec, Heather A.; Dunlap, Patrick H., Jr.

    2016-01-01

    An electrically conductive elastomer was evaluated as a material candidate for a spacecraft seal. The elastomer used electrically conductive constituents as a means to reduce the resistance between mating interfaces of a sealed joint to meet spacecraft electrical bonding requirements. The compound's outgassing levels were compared against published NASA requirements. The compound was formed into a hollow O-ring seal and its compression set was measured. The O-ring seal was placed into an interface and the electrical resistance and leak rate were quantified. The amount of force required to fully compress the test article in the sealing interface and the force needed to separate the joint were also measured. The outgassing and resistance measurements were below the maximum allowable levels. The room temperature compression set and leak rates were fairly high when compared against other typical spacecraft seal materials, but were not excessive. The compression and adhesion forces were desirably low. Overall, the performance of the elastomer compound was sufficient to be considered for future spacecraft seal applications.

  19. A survey on dielectric elastomer actuators for soft robots.

    Science.gov (United States)

    Gu, Guo-Ying; Zhu, Jian; Zhu, Li-Min; Zhu, Xiangyang

    2017-01-23

    Conventional industrial robots with the rigid actuation technology have made great progress for humans in the fields of automation assembly and manufacturing. With an increasing number of robots needing to interact with humans and unstructured environments, there is a need for soft robots capable of sustaining large deformation while inducing little pressure or damage when maneuvering through confined spaces. The emergence of soft robotics offers the prospect of applying soft actuators as artificial muscles in robots, replacing traditional rigid actuators. Dielectric elastomer actuators (DEAs) are recognized as one of the most promising soft actuation technologies due to the facts that: i) dielectric elastomers are kind of soft, motion-generating materials that resemble natural muscle of humans in terms of force, strain (displacement per unit length or area) and actuation pressure/density; ii) dielectric elastomers can produce large voltage-induced deformation. In this survey, we first introduce the so-called DEAs emphasizing the key points of working principle, key components and electromechanical modeling approaches. Then, different DEA-driven soft robots, including wearable/humanoid robots, walking/serpentine robots, flying robots and swimming robots, are reviewed. Lastly, we summarize the challenges and opportunities for the further studies in terms of mechanism design, dynamics modeling and autonomous control.

  20. Dynamic pattern of wrinkles in a dielectric elastomer.

    Science.gov (United States)

    Godaba, Hareesh; Zhang, Zhi-Qian; Gupta, Ujjaval; Chiang Foo, Choon; Zhu, Jian

    2017-04-19

    A membrane of a dielectric elastomer may undergo electromechanical phase transition from the flat to wrinkled state, when the applied voltage reaches a critical value. The wrinkled region is observed to expand at the expense of the flat region during the phase transition. In this paper, we report on a dynamic pattern of wrinkles in a circular membrane of a dielectric elastomer. During phase transition, both the flat and wrinkled regions move interchangeably in the membrane. The radial prestretch is found to significantly affect electromechanical phase transition. For example, a membrane with a small prestretch can exhibit a dynamic pattern of wrinkles, which is essentially related to snap-through instability. However, a membrane with a large prestretch undergoes continuous phase transition, without exhibiting a dynamic pattern. An analytical model is developed to interpret these experimental phenomena. Finite element simulations are performed to predict the wrinkle morphology, especially the coexistence of flat and wrinkled regions. Both the theoretical calculations and finite element simulations are qualitatively consistent with the experiments. Additionally, we observe another type of electromechanical behavior involving a dynamic pattern of wrinkles with different wavelengths. The membrane first undergoes continuous transition from the flat to wrinkled state, followed by discontinuous transition from one wrinkled state to another. These results may inspire new applications for dielectric elastomers such as on-demand patterning of wrinkles for microfluidics and stretchable electronics.

  1. Rupture of a highly stretchable acrylic dielectric elastomer

    Science.gov (United States)

    Pharr, George; Sun, Jeong-Yun; Suo, Zhigang

    2012-02-01

    Dielectric elastomers have found widespread application as energy harvesters, actuators, and sensors. In practice these elastomers are subject to large tensile stretches, which potentially can lead to mechanical fracture. In this study, we have examined fracture properties of the commercial acrylic elastomer VHB 4905. We have found that inserting a pre-cut into the material drastically reduces the stretch at rupture from λrup = 9.43±1.05 for pristine samples down to only λrup = 3.63±0.45 for the samples with a pre-cut. Furthermore, using ``pure-shear'' test specimens with a pre-crack, we have measured the fracture energy and stretch at rupture as a function of the sample geometry. The stretch at rupture was found to decrease with sample height, which agrees with an analytical prediction. Additionally, we have measured the fracture energy as a function of stretch-rate. The apparent fracture energy was found to increase with stretch-rate from γ 1500 J/m^2 to γ 5000 J/m^2 for the investigated rates of deformation. This phenomenon is due to viscoelastic properties of VHB 4905, which result in an apparent stiffening for sufficiently large stretch-rates.

  2. Control of the stiffness of robotic appendages using dielectric elastomers

    Science.gov (United States)

    Morton, Jeffrey

    A new robotic leg design is presented that utilizes dielectric elastomers (3M VHB 4910) to rapidly control stiffness changes for enhanced mobility and agility of a field demonstrated hexapod robot. It has been shown that stiffness changes of electro-active membranes made of dielectric elastomers can overcome challenges with other polymer materials that use heat to create modulus and stiffness changes. Applied electric fields eliminate issues with thermal transport rates and thermo-mechanical delaminatation. The dielectric elastomer is characterized uniaxially to understand its hyperelastic and viscoelastic properties. The uniaxial data is fit to a hyperelastic and viscoelastic finite deformation model. The material is then pre-stretched biaxially to stretch ratios ranging from 200%, 300% and 400%. A set of electro-mechanical transverse load experiments are then utilized to obtain up to 92% reduction in stiffness that is controlled by an electric field. The results are compared to a finite deformation membrane finite element model to understand and improve field driven stiffness changes for real-time robotic applications.

  3. The influence of static pre-stretching on the mechanical ageing of filled silicone rubbers for dielectric elastomer applications

    DEFF Research Database (Denmark)

    Zakaria, Shamsul Bin; Yu, Liyun; Kofod, Guggi

    2015-01-01

    -stretching is difficult to achieve withhighly filled elastomers. However, despite the negative outlook for metal oxide-filled silicone elastomers,the study paves the way for reliable dielectric elastomers by indicating that simply post-curing siliconeelastomers before use may increase reliability....

  4. Morphology of Thermoplastic Elastomers:Stereoblock Polypropylene

    Energy Technology Data Exchange (ETDEWEB)

    Pople, John A

    2002-08-06

    The morphologies of low-density (0.86 g/cm{sup 3}), elastomeric polypropylene (ePP) derived from bis(2-arylindenyl) hafnium dichloride were investigated using a combination of polarized optical microscopy (OM), differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS), Fourier transform infrared (FT-IR) spectroscopy, and tapping mode atomic force microscopy (TMAFM). These low-crystallinity polypropylenes, when crystallized isothermally from the melt, exhibit morphologies reminiscent of classical semi-crystalline polymers. The presence of lamellae, cross-hatching, hedrites, and spherulites was revealed by high resolution TM-AFM. These elastomeric polypropylenes can be fractionated into components of different average tacticities and crystallinities, but similar molecular mass. The analysis of the morphologies of all of the fractions revealed both large hierarchical structures and cross-hatching typical of the {alpha}-modification of crystalline isotactic polypropylene for all but the lowest crystalline ether soluble fraction. Evidence for high-melting crystals in all of the fractions are most consistent with a stereoblock microstructure of atactic and isotactic sequences.

  5. Growth of dopamine crystals

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Vidya, E-mail: vidya.patil@ruparel.edu; Patki, Mugdha, E-mail: mugdha.patki@ruparel.edu [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)

    2016-05-06

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  6. ZnO as a cheap and effective filler for high breakdown strength elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Skov, Anne Ladegaard

    2017-01-01

    . In this article, we explore the use of a cheap and abundant metal oxide filler, namely ZnO, as a filler in silicone-based dielectric elastomers. The electro-mechanical properties of the elastomer composites are investigated, and their performance is evaluated by means of figures of merit. Various commercial...

  7. Glycerol as high-permittivity liquid filler in dielectric silicone elastomers

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Yu, Liyun; Gerhard, R.

    2016-01-01

    A recently reported novel class of elastomers was tested with respect to its dielectric properties. The new elastomer materialis based on a commercially available poly(dimethylsiloxane) composition, which has been modified by embedding glycerol droplets intoits matrix. The approach has two major ...

  8. Glycerol as high-permittivity liquid filler in dielectric silicone elastomers

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Yu, Liyun; Skov, Anne Ladegaard

    A recently reported novel class of elastomers was tested with respect to its dielectric properties. The new elastomer material is based on a commercially available polydimethylsiloxane (PDMS) composition, which has been modified by embedding glycerol droplets into its matrix.The approach has two ...

  9. Phase Behavior of Three PBX Elastomers in High-Pressure Chlorodifluoromethane

    Science.gov (United States)

    Lee, Byung-Chul

    2017-10-01

    The phase equilibrium behavior data are presented for three kinds of commercial polymer-bonded explosive (PBX) elastomers in chlorodifluoromethane (HCFC22). Levapren^{{registered }} ethylene- co-vinyl acetate (LP-EVA), HyTemp^{{registered }} alkyl acrylate copolymer (HT-ACM), and Viton^{{registered }} fluoroelastomer (VT-FE) were used as the PBX elastomers. For each elastomer + HCFC22 system, the cloud point (CP) and/or bubble point (BP) pressures were measured while varying the temperature and elastomer composition using a phase equilibrium apparatus fitted with a variable-volume view cell. The elastomers examined in this study indicated a lower critical solution temperature phase behavior in the HCFC22 solvent. LP-EVA showed the CPs at temperatures of 323 K to 343 K and at pressures of 3 MPa to 10 MPa, whereas HT-ACM showed the CPs at conditions between 338 K and 363 K and between 4 MPa and 12 MPa. For the LP-EVA and HT-ACM elastomers, the BP behavior was observed at temperatures below about 323 K. For the VT-FE + HCFC22 system, only the CP behavior was observed at temperatures between 323 K and 353 K and at pressures between 6 MPa and 21 MPa. As the elastomer composition increased, the CP pressure increased, reached a maximum value at a specific elastomer composition, and then remained almost constant.

  10. Artificial muscles of dielectric elastomers attached to artificial tendons of functionalized carbon fibers

    Science.gov (United States)

    Ye, Zhihang; Faisal, Md. Shahnewaz Sabit; Asmatulu, Ramazan; Chen, Zheng

    2014-03-01

    Dielectric elastomers are soft actuation materials with promising applications in robotics and biomedical de- vices. In this paper, a bio-inspired artificial muscle actuator with artificial tendons is developed for robotic arm applications. The actuator uses dielectric elastomer as artificial muscle and functionalized carbon fibers as artificial tendons. A VHB 4910 tape is used as the dielectric elastomer and PDMS is used as the bonding material to mechanically connect the carbon fibers to the elastomer. Carbon fibers are highly popular for their high electrical conductivities, mechanical strengths, and bio-compatibilities. After the acid treatments for the functionalization of carbon fibers (500 nm - 10 μm), one end of carbon fibers is spread into the PDMS material, which provides enough bonding strength with other dielectric elastomers, while the other end is connected to a DC power supply. To characterize the actuation capability of the dielectric elastomer and electrical conductivity of carbon fibers, a diaphragm actuator is fabricated, where the carbon fibers are connected to the actuator. To test the mechanical bonding between PDMS and carbon fibers, specimens of PDMS bonded with carbon fibers are fabricated. Experiments have been conducted to verify the actuation capability of the dielectric elastomer and mechanical bonding of PDMS with carbon fibers. The energy efficiency of the dielectric elastomer increases as the load increases, which can reach above 50%. The mechanical bonding is strong enough for robotic arm applications.

  11. Characterization, fabrication, and analysis of soft dielectric elastomer actuators capable of complex 3D deformation

    Science.gov (United States)

    Lai, William

    Inspired by nature, the development of soft actuators has drawn large attention to provide higher flexibility and allow adaptation to more complex environment. This thesis is focused on utilizing electroactive polymers as active materials to develop soft planar dielectric elastomer actuators capable of complex 3D deformation. The potential applications of such soft actuators are in flexible robotic arms and grippers, morphing structures and flapping wings for micro aerial vehicles. The embraces design for a freestanding actuator utilizes the constrained deformation imposed by surface stiffeners on an electroactive membrane to avert the requirement of membrane pre-stretch and the supporting frames. The proposed design increases the overall actuator flexibility and degrees-of-freedom. Actuator design, fabrication, and performance are presented for different arrangement of stiffeners. Digital images correlation technique were utilized to evaluate the in-plane finite strain components, in order to elucidate the role of the stiffeners in controlling the three dimensional deformation. It was found that a key controlling factor was the localized deformation near the stiffeners, while the rest of the membrane would follow through. A detailed finite element modeling framework was developed with a user-material subroutine, built into the ABAQUS commercial finite element package. An experimentally calibrated Neo-Hookean based material model that coupled the applied electrical field to the actuator mechanical deformation was employed. The numerical model was used to optimize different geometrical features, electrode layup and stacking sequence of actuators. It was found that by splitting the stiffeners into finer segments, the force-stroke characteristics of actuator were able to be adjusted with stiffener configuration, while keeping the overall bending stiffness. The efficacy of actuators could also be greatly improved by increasing the stiffener periodicity. The developed

  12. Dielectric elastomers, with very high dielectric permittivity, based on silicone and ionic interpenetrating networks

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Hvilsted, Søren

    2015-01-01

    permittivity and the Young's modulus of the elastomer. One system that potentially achieves this involves interpenetrating polymer networks (IPNs), based on commercial silicone elastomers and ionic networks from amino- and carboxylic acid-functional silicones. The applicability of these materials as DEs...... is demonstrated herein, and a number of many and important parameters, such as dielectric permittivity/loss, viscoelastic properties and dielectric breakdown strength, are investigated. Ionic and silicone elastomer IPNs are promising prospects for dielectric elastomer actuators, since very high permittivities...... are obtained while dielectric breakdown strength and Young's modulus are not compromised. These good overall properties stem from the softening effect and very high permittivity of ionic networks – as high as ε′ = 7500 at 0.1 Hz – while the silicone elastomer part of the IPN provides mechanical integrity...

  13. Degradation patterns of silicone-based dielectric elastomers in electrical fields

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Skov, Anne Ladegaard

    2017-01-01

    Silicone elastomers have been heavily investigated as candidates for the flexible insulator material in dielectric elastomer transducers and are as such almost ideal candidates because of their inherent softness and compliance. However, silicone elastomers suffer from low dielectric permittivity....... This shortcoming has been attempted optimized through different approaches during recent years. Material optimization with the sole purpose of increasing the dielectric permittivity may lead to the introduction of problematic phenomena such as premature electrical breakdown due to high leakage currents of the thin...... elastomer film. Within this work, electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers are investigated. Results showed that different types of polymer backbone chemistries lead to differences in electrical breakdown patterns, which were revealed through SEM imaging...

  14. A simple method for reducing inevitable dielectric loss in high-permittivity dielectric elastomers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Yu, Liyun; Mazurek, Piotr Stanislaw

    2016-01-01

    elastomer matrix, with high dielectric permittivity and a low Young's modulus, aligned with no loss of mechanical stability, was prepared through the use of commercially available chloropropyl-functional silicone oil mixed into a tough commercial liquid silicone rubber silicone elastomer. The addition......Commercial viability of dielectric elastomers (DEs) is currently limited by a few obstacles, including high driving voltages (in the kV range). Driving voltage can be lowered by either decreasing the Young's modulus or increasing the dielectric permittivity of silicone elastomers, or a combination...... of chloropropyl-functional silicone oil in concentrations up to 30 phr was found to improve the properties of the silicone elastomer significantly, as dielectric permittivity increased to 4.4, dielectric breakdown increased up to 25% and dielectric losses were reduced. The chloropropyl-functional silicone oil...

  15. Pneumatic Multi-Pocket Elastomer Actuators for Metacarpophalangeal Joint Flexion and Abduction-Adduction

    Directory of Open Access Journals (Sweden)

    Tapio Veli Juhani Tarvainen

    2017-09-01

    Full Text Available During recent years, interest has been rising towards developing fluidic fiber-reinforced elastomer actuators for wearable soft robotics used in hand rehabilitation and power-assist. However, they do not enable finger abduction-adduction, which plays an important role in activities of daily living, when grasping larger objects. Furthermore, the developed gloves often do not have separate control of joints, which is important for doing various common rehabilitation motions. The main obstacle for the development of a fully-assisting glove is moving a joint with multiple degrees of freedom. If the functions are built into the same structure, they are naturally coupled and affect each other, which makes them more difficult to design and complex to control than a simple flexion-extension actuator. In this study, we explored the key design elements and fabrication of pneumatic multi-pocket elastomer actuators for a soft rehabilitation glove. The goal was to gain more control over the metacarpophalangeal joint’s response by increasing the degree of actuation. Three main functional designs were tested for achieving both flexion and abduction-adduction. Five prototypes, with four different actuator geometries and four different reinforcement types, were designed and fabricated. They were evaluated by recording their free motion with motion capture and measuring their torque output using a dummy finger. Results showed the strengths and weaknesses of each design in separating the control of the two functions. We discuss the different improvements that are needed in order to make each design plausible for developing an actuator that meets the requirements for full assist of the hand’s motions. In conclusion, we show that it is possible to produce multi-pocket actuators for assisting MCP joint motion in both flexion and abduction-adduction, although coupling between the separate functions is still problematic and should be considered further.

  16. Synthesis and stop band tuning application of colloidal photonic crystal

    Science.gov (United States)

    Xia, Jiqiang

    were significantly enhanced by modifying the permittivity of the solid film. Static and dynamic stop band tuning characteristics of elastomer encapsulated PBG composites were investigated through a dynamic spectroscopic apparatus. This apparatus, which met essentially all of the goals set during the design stage, was constructed in-house. The results of the piezoelectric stop band tuning using this apparatus indicated that deformation of the photonic crystals significantly influenced their reflection spectra. The mechanochromic mechanism was investigated using Kossel diffraction technique, with the result indicating that the stop band attenuating and broadening may be attributed primarily to the disorder induced during deformation. The characteristics of static and dynamic mechanochromic tuning of PBG composites can be controlled by the thermomechanical properties of the encapsulating polymers. In addition, the electrical percolation of melt-mixed, conductive HDPE-SWNT and HDPE-MWNT composites was studied and compared with HDPE-CB composites. The introduction of SWNT or NMWNT into HDPE decreased its resistivity by up to 13 orders of magnitude. The percolation behavior agreed very well with the percolation theory and the threshold was ca. 1.5 wt% (0.96 vol%) for HDPE-SWNT. The morphology, thermostability and crystallinity of the composites were also investigated to understand the structure-property relationship.

  17. Batch fabrication of optical actuators using nanotube-elastomer composites towards refreshable Braille displays

    Science.gov (United States)

    Camargo, C. J.; Campanella, H.; Marshall, J. E.; Torras, N.; Zinoviev, K.; Terentjev, E. M.; Esteve, J.

    2012-07-01

    This paper reports an opto-actuable device fabricated using micro-machined silicon moulds. The actuating component of the device is made from a composite material containing carbon nanotubes (CNTs) embedded in a liquid crystal elastomer (LCE) matrix. We demonstrate the fabrication of a patterned LCE-CNT film by a combination of mechanical stretching and thermal cross-linking. The resulting poly-domain LCE-CNT film contains ‘blister-shaped’ mono-domain regions, which reversibly change their shape under light irradiation and hence can be used as dynamic Braille dots. We demonstrate that blisters with diameters of 1.0 and 1.5 mm, and wall thickness 300 µm, will mechanically contract under irradiation by a laser diode with optical power up to 60 mW. The magnitude of this contraction was up to 40 µm, which is more than 10% of their height in the ‘rest’ state. The stabilization time of the material is less than 6 s for both actuation and recovery. We also carried out preliminary tests on the repeatability of this photo-actuation process, observing no material or performance degradation. This manufacturing approach establishes a starting point for the design and fabrication of wide-area tactile actuators, which are promising candidates for the development of new Braille reading applications for the visually impaired.

  18. Mechanical and thermal properties of PP/PBT blends compatibilized with triblock thermoplastic elastomer

    Directory of Open Access Journals (Sweden)

    Ignaczak Wojciech

    2015-09-01

    Full Text Available A linear triblock copolymer, poly(styrene-b-etylene/butylene-b-styrene(SEBS thermoplastic elastomer (TPE grafted with maleic anhydride was used for compatibilization of PP/PBT blends. PP/PBT blends of different mass ratios 60/40, 50/50, 40/60 were mixed with 2.5, 5.0 and 7.5 wt.% of SEBS copolymer in a twin screw extruder. Differential scanning calorimetry and dynamic mechanical analysis were performed to define the phase structure of PP/PBT blends. TPE with a rubbery mid-block shifted the glass transition of PP/PBT blend towards lower temperatures, and significant decrease the crystallization temperature of a crystalline phase of PP component was observed. The influence of the amount of compatibilizer and the blend composition on the mechanical properties (tensile and flexural strengths, toughness and moduli was determined. Addition of 5 wt.% of a triblock TPE led to a three-fold increase of PP/PBT toughness. A significant increase of impact properties was observed for all materials compatibilized with the highest amount of SEBS copolymer.

  19. Nanomechanical probing of thin-film dielectric elastomer transducers

    Science.gov (United States)

    Osmani, Bekim; Seifi, Saman; Park, Harold S.; Leung, Vanessa; Töpper, Tino; Müller, Bert

    2017-08-01

    Dielectric elastomer transducers (DETs) have attracted interest as generators, actuators, sensors, and even as self-sensing actuators for applications in medicine, soft robotics, and microfluidics. Their performance crucially depends on the elastic properties of the electrode-elastomer sandwich structure. The compressive displacement of a single-layer DET can be easily measured using atomic force microscopy (AFM) in the contact mode. While polymers used as dielectric elastomers are known to exhibit significant mechanical stiffening for large strains, their mechanical properties when subjected to voltages are not well understood. To examine this effect, we measured the depths of 400 nanoindentations as a function of the applied electric field using a spherical AFM probe with a radius of (522 ± 4) nm. Employing a field as low as 20 V/μm, the indentation depths increased by 42% at a load of 100 nN with respect to the field-free condition, implying an electromechanically driven elastic softening of the DET. This at-a-glance surprising experimental result agrees with related nonlinear, dynamic finite element model simulations. Furthermore, the pull-off forces rose from (23.0 ± 0.4) to (49.0 ± 0.7) nN implying a nanoindentation imprint after unloading. This embossing effect is explained by the remaining charges at the indentation site. The root-mean-square roughness of the Au electrode raised by 11% upon increasing the field from zero to 12 V/μm, demonstrating that the electrode's morphology change is an undervalued factor in the fabrication of DET structures.

  20. Cylindrical dielectric elastomer actuators reinforced with inextensible fibers

    Science.gov (United States)

    Goulbourne, Nakhiah C. S.

    2006-03-01

    Novel actuator configurations for various applications can be obtained using cylindrical dielectric elastomer actuators. A new configuration for a contractile electro-elastomer is presented here for the first time. A cylindrical or tubular configuration is used to realize simultaneous axial shortening and radial expansion when a voltage is applied across the thickness of the hollow cylinder. In this configuration, the inner and outer surfaces of a cylindrical dielectric elastomer are coated with compliant electrodes. The outer cylindrical surface is then enclosed by a network of helical fibers that are very thin, very flexible and inextensible. Fiber networks or cord families are commonly used in many different materials and for a variety of applications. The primary purpose of these networks is structural, that is to say, for reinforcement. The composite active structure proposed here is reminiscent of the McKibben actuator, a pneumatically actuated cylindrical construct consisting of a flexible rubber bladder sheathed in a fiber network, which garners its impressive contracting force from the inextensible fibers that prevent axial extension when an inflation pressure is applied to the internal bladder [1]. The system is modeled using an electro- elastic formulation derived from the large deformation theory of reinforced cylinders [2]. The model combines Maxwell-Faraday electrostatics and nonlinear elasticity theory [3]. Illustratively, solutions are obtained assuming a Mooney-Rivlin material model for a silicone actuator. The results indicate that the relationship between the axial contraction force and the axial shortening is linear for the voltage range considered. The importance of other system parameters such as the fiber angle and the applied constant pressure is also reported.

  1. Electronic crystal growth

    Science.gov (United States)

    Sato, T.; Miyagawa, K.; Kanoda, K.

    2017-09-01

    Interacting atoms or molecules condense into liquid, and, when cooled further, they form a crystal. The time evolution of the atomic or molecular ordering has been widely studied as a nonequilibrium emergence of order from a supercooled liquid or a glass. Interacting electrons in a variety of correlated electron systems also form crystals, but observing the time evolution of electronic crystallization has been experimentally challenging. Here, working with an organic conductor exhibiting a supercooled charge liquid or charge glass as a metastable state, we observed electronic crystal growth through resistivity and nuclear magnetic resonance measurements. The temperature profile of the crystal growth is similar to those observed in classical systems and reveals two distinct regimes for the mechanism of electronic crystallization.

  2. Formation of free radicals during mechanical degradation of elastomers.

    Science.gov (United States)

    Devries, K. L.; Williams, M. L.; Roylance, D. K.

    1971-01-01

    Solithane 113 (an amorphous polyurethane elastomer) was prepared by curing equal proportions of castor oil and trifunctional isocyanate for 6 hr 45 min at 170 F. The sample material was mechanically degraded by grinding below and above its glass transition point at liquid nitrogen and room temperatures. The EPR spectra of ground samples were recorded and the number of free radicals were determined by a computer double-integration of the recorded spectra and by a comparison of the values with those of a standard material. Curves of EPR spectra suggest that different molecular mechanisms may be active in degradation of this material below and above its glass transition temperature.

  3. Printing 3D dielectric elastomer actuators for soft robotics

    Science.gov (United States)

    Rossiter, Jonathan; Walters, Peter; Stoimenov, Boyko

    2009-03-01

    We present a new approach to the fabrication of soft dielectric elastomer actuators using a 3D printing process. Complete actuators including active membranes and support structures can be 3D printed in one go, resulting in a great improvement in fabrication speed and increases in accuracy and consistency. We describe the fabrication process and present force and displacement results for a double-membrane antagonistic actuator. In this structure controlled prestrain is applied by the simple process of pressing together two printed actuator halves. The development of 3D printable soft actuators will have a large impact on many application areas including engineering, medicine and the emerging field of soft robotics.

  4. Novel percolation phenomena and mechanism of strengthening elastomers by nanofillers.

    Science.gov (United States)

    Wang, Zhenhua; Liu, Jun; Wu, Sizhu; Wang, Wenchuan; Zhang, Liqun

    2010-03-28

    Nano-strengthening by employing nanoparticles is necessary for high-efficiency strengthening of elastomers, which has already been validated by numerous researches and industrial applications, but the underlying mechanism is still an open challenge. In this work, we mainly focus our attention on studying the variation of the tensile strength of nanofilled elastomers by gradually increasing the filler content, within a low loading range. Interestingly, the percolation phenomenon is observed in the relationship between the tensile strength and the filler loading, which shares some similarities with the percolation phenomenon occurring in rubber toughened plastics. That is, as the loading of nanofillers (carbon black, zinc oxide) increases, the tensile strength of rubber nanocomposites (SBR, EPDM) increases slowly at first, then increases abruptly and finally levels off. Meanwhile, the bigger the particle size, the higher the filler content at the percolation point, and the lower the corresponding tensile strength of rubber nanocomposites. The concept of a critical particle-particle distance (CPD) is proposed to explain the observed percolation phenomenon. It is suggested that rubber strengthening through nanoparticles is attributed to the formation of stretched straight polymer chains between neighbor particles, induced by the slippage of adsorbed polymer chains on the filler surface during tension. Meanwhile, the factors to govern this CPD and the critical minimum particle size (CMPS) figured out in this work are both discussed and analyzed in detail. Within the framework of this percolation phenomenon, this paper also clearly answers two important and intriguing issues: (1) why is it necessary and essential to strengthen elastomers through nanofillers; (2) why does it need enough loading of nanofillers to effectively strengthen elastomers. Moreover, on the basis of the percolation phenomenon, we give out some guidance for reinforcement design of rubbery materials

  5. Thermoelectric elastomer fabricated using carbon nanotubes and nonconducting polymer

    Science.gov (United States)

    Choi, Jeong-Hun; Hyun, Cheol-Min; Jo, Hyunjin; Son, Ji Hee; Lee, Ji Eun; Ahn, Ji-Hoon

    2017-09-01

    The electrical and thermoelectric properties of an organic elastomer composite composed of carbon nanotubes (CNTs) and a nonconductive polymer were systemically investigated as a function of CNT content. As the CNT content of the poly(dimethylsiloxane) (PDMS) matrix increased, the electrical conductivity increased remarkably (by about 250 times) without a large increase in the thermal conductivity, which could lead to significant improvement in the ZT value. Moreover, the Seebeck coefficient was also enhanced by increasing the CNT content. Consequently, the ZT value was effectively increased by a small increase in the quantity of CNTs in the nonconductive polymer matrix.

  6. Magnetorheological elastomer-based quadrupolar element of electric circuits

    Energy Technology Data Exchange (ETDEWEB)

    Bica, Ioan, E-mail: ibica2@yahoo.co [West University of Timisoara, Faculty of Physics, Bd. V. Parvan, No. 4, 300223 Timisoara (Romania)

    2010-01-15

    The author of this paper describes a quadrupolar electric circuit element (Q) based on electroconductive magnetorheological elastomer. It is shown by means of the experimental setup presented in the paper, that the electrical resistances, measured at the gates of Q, decrease with the increase of the strength H of the transverse magnetic field. But, for intensities of the control current (I{sub c} = const.) injected into Q along the direction normal to H{sup -}>, the voltage at the outlet of Q decreases as the strength of the magnetic field increases. The as-obtained experimental results are presented and discussed.

  7. Viscoelastic creep elimination in dielectric elastomer actuation by preprogrammed voltage

    Science.gov (United States)

    Zhang, Junshi; Wang, Yanjie; McCoul, David; Pei, Qibing; Chen, Hualing

    2014-11-01

    Viscoelasticity causes a time-dependent deformation and lowers the response speed and energy conversion efficiency of VHB-based dielectric elastomers (DEs), thus seriously restricting a wide range of applications of this otherwise versatile soft smart material. The viscoelastic deformation of a prestretched VHB film in a circular actuator configuration is studied both theoretically and experimentally. By adjusting the applied voltage, viscoelastic creep can be dispelled and an invariable strain is obtained by simulation. Subsequently, an experiment was designed to validate the simulation and the results indicate that a constant strain can be achieved by preprogramming the applied actuation voltage.

  8. Solid Silicone Elastomer Material(DC745U)-Historical Overview and New Experimental Results

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz-Acosta, Denisse [Los Alamos National Laboratory

    2012-08-08

    DC745U is a silicone elastomer used in several weapon systems. DC745U is manufactured by Dow Corning and its formulation is proprietary. Risk changes without notification to the customer. {sup 1}H and {sup 29}Si{l_brace}{sup 1}H{r_brace} NMR have previously determined that DC745U contains {approx} 98.5% dimethyl siloxane, {approx}1.5% methyl-phenyl siloxane, and a small amount (<1%) of vinyl siloxane repeat units that are converted to crosslinking sites. The polymer is filled with {approx} 38 wt.% of a mixture of fumed silica and quartz. Some conclusions are: (1) DMA shows that crystallization does have an effect on the mechanical properties of DC745U; (2) DMA shows that the crystallization is time and temperature dependent; (3) Mechanical tests show that DC745U undergo a crystalline transition at temperatures below -50 C; (4) Rate and temperature does not have an effect above crystalline transition; (5) Crystalline transition occurs faster at colder temperatures; (6) The material remains responsive and recovers after warming it to temperature above -40 C; (7) We were able to review all previous historical data on DC745U; (8) Identified specific gaps in materials understanding; (9) Developed design of experiments and testing methods to address gaps associated with post-curing and low temperature mechanical behavior; (10) Resolved questions of post-cure and alleviated concerns associated with low temperature mechanical behavior with soak time and temperature; and (11) This work is relevant to mission-critical programs and for supporting programmatic work for weapon research.

  9. Effect of vulcanization temperature and dental stone colour on colour degradation of maxillofacial silicone elastomers.

    Science.gov (United States)

    Cifter, Ebru Demet; Ozdemir-Karatas, Meltem; Baca, Emrah; Cinarli, Adem; Balik, Ali; Sancakli, Erkan; Gokcen-Rohlig, Bilge

    2017-03-31

    Colour degradation is a major problem in maxillofacial silicone elastomers. Recent studies have focused on colour stability and the mechanical properties of the silicone elastomers. A colour match is also essential for the acceptance of the prosthesis by the patient. The aim of this study is to assess the colour degradation of the silicone elastomer after being moulded in different colours of dental stones at two different vulcanization temperatures. Five different colours of dental stones were used to fabricate a total of 120 silicone blocks using a Cosmesil M511 maxillofacial silicone elastomer. Vulcanization was completed at two different temperatures (25 and 100° Celsius). Colour measurements were obtained with a Conica Minolta spectrophotometer. The CIEDE2000 formula was used to calculate the colour differences (∆E00). Two-way ANOVA, one-way ANOVA with Bonferroni corrected post-hoc p values and independent samples t-test were used for the statistical analyses. High temperature vulcanization causes lightening of the maxillofacial silicone elastomers without regard to the dental stone colour (p = 0.001). Specimens moulded in green stone lightened least at room temperature (p = 0.999). Compared to the control group, at high temperature, all specimens moulded in coloured dental stones darkened significantly (p vulcanized in a stainless steel mould. White, yellow and reddish-brown dental stones make the silicone elastomer appear more yellow even if the elastomer is vulcanized at room temperature.

  10. A New Mechanical Loading Configuration for Maximizing The Performance of Dielectric Elastomer Generators

    Science.gov (United States)

    Shian, Samuel; Huang, Jiangshui; Suo, Zhigang; Clarke, David

    2013-03-01

    Electrical energy can be generated from mechanical deformations using dielectric elastomers but currently achieved energy densities and conversion efficiencies are still small. In this presentation, we demonstrate that significant improvements, an energy density over 500 mJ/g and up to 10% in efficiency, can be produced using VHB elastomers by altering the mechanical loading geometry. A major limitation is viscous losses in the VHB elastomer indicating that higher efficiencies with other elastomers will be attainable. The basic concept of mechanical energy harvesting with a dielectric elastomer sheet is a straightforward electromechanical cycle leading to a voltage step-up: a sheet is stretched, electrical charge at low voltage is placed on either side using compliant electrodes, the stretch is released causing the sheet's initial thickness and area to be recovered increasing the charge potential which can then be harvested. Integral to maximizing the energy conversion is the amount of mechanical energy that can be stored elastically and the amount of capacitance change in the elastomer sheet during stretching. We show that these factors can be maximized by equi-biaxial loading. Details of our dielectric elastomer generator will be described as well as the procedures we use for quantifying its performance.

  11. Shape instability of a magnetic elastomer membrane

    Energy Technology Data Exchange (ETDEWEB)

    Raikher, Yu L; Stolbov, O V [Institute of Continuous Media Mechanics, Ural Branch of RAS, 614013 Perm (Russian Federation); Stepanov, G V [State Scientific Center ' Institute of Chemistry and Technology of Organoelement Compounds' , 11123 Moscow (Russian Federation)], E-mail: raikher@icmm.ru

    2008-08-07

    Shape instability occurring in a thin plate (membrane) made of a soft magnetoelastic material under a uniform magnetic field is predicted and analysed. The instability onset is shown to be similar to the second-order transition; the dependence of the threshold field on the magnetic and geometric parameters of the membrane is derived analytically; the membrane shapes (domes) are evaluated with the aid of numerical simulation. The theory proposed is in general agreement with experiments performed on a siloxane rubber/iron carbonyl composite. (fast track communication)

  12. OD (order-disorder) character of the crystal structure of godlevskite Ni9S8

    DEFF Research Database (Denmark)

    Merlino, Stefano; Makovicky, Emil

    2009-01-01

    Godlevskite Ni9S8 has been found to be an OD (order-disorder) structure consisting of two kinds of OD layers in strict alternation; these layers display stacking disorder. They have layer symmetries P( )2m and P212(2), respectively (symmetry elements in parentheses are perpendicular to OD layers...

  13. Crystal structures of spin-Jahn-Teller-ordered MgCr2O4 and ZnCr2O4

    Science.gov (United States)

    Kemei, Moureen C.; Barton, Phillip T.; Moffitt, Stephanie L.; Gaultois, Michael W.; Kurzman, Joshua A.; Seshadri, Ram; Suchomel, Matthew R.; Kim, Young-Il

    2013-08-01

    Magnetic ordering in the geometrically frustrated magnetic oxide spinels MgCr2O4 and ZnCr2O4 is accompanied by a structural change that helps to relieve the frustration. Analysis of high-resolution synchrotron x-ray scattering reveals that the low-temperature structures are well described by a two-phase model of tetragonal I41/amd and orthorhombic Fddd symmetries. The Cr4 tetrahedra of the pyrochlore lattice are distorted at these low-temperatures, with the Fddd phase displaying larger distortions than the I41/amd phase. The spin-Jahn-Teller distortion is approximately one order of magnitude smaller than is observed in first-order Jahn-Teller spinels such as NiCr2O4 and CuCr2O4. In analogy with NiCr2O4 and CuCr2O4, we further suggest that the precise nature of magnetic ordering can itself provide a second driving force for structural change.

  14. Crystal structures of spin-Jahn-Teller-ordered MgCr2O4 and ZnCr2O4.

    Science.gov (United States)

    Kemei, Moureen C; Barton, Phillip T; Moffitt, Stephanie L; Gaultois, Michael W; Kurzman, Joshua A; Seshadri, Ram; Suchomel, Matthew R; Kim, Young-Il

    2013-08-14

    Magnetic ordering in the geometrically frustrated magnetic oxide spinels MgCr2O4 and ZnCr2O4 is accompanied by a structural change that helps to relieve the frustration. Analysis of high-resolution synchrotron x-ray scattering reveals that the low-temperature structures are well described by a two-phase model of tetragonal I41/amd and orthorhombic Fddd symmetries. The Cr4 tetrahedra of the pyrochlore lattice are distorted at these low-temperatures, with the Fddd phase displaying larger distortions than the I41/amd phase. The spin-Jahn-Teller distortion is approximately one order of magnitude smaller than is observed in first-order Jahn-Teller spinels such as NiCr2O4 and CuCr2O4. In analogy with NiCr2O4 and CuCr2O4, we further suggest that the precise nature of magnetic ordering can itself provide a second driving force for structural change.

  15. Self-healing of optical functions by molecular metabolism in a swollen elastomer

    Directory of Open Access Journals (Sweden)

    Mitsunori Saito

    2012-12-01

    Full Text Available Optical functions of organic dyes, e.g., fluorescence or photochromism, tend to degrade by light irradiation, which causes a short lifetime of photonic devices. Self-healing of optical functions is attainable by metabolizing bleached molecules with nonirradiated ones. A polydimethylsiloxane elastomer provides a useful matrix for dye molecules, since its flexible structure with nano-sized intermolecular spaces allows dye diffusion from a reservoir to an operation region. Swelling the elastomer with a suitable solvent promotes both dissolution and diffusion of dye molecules. This self-healing function was demonstrated by an experiment in which a photochromic elastomer exhibited improved durability against a repeated coloring-decoloring process.

  16. A lightweight push-pull acoustic transducer composed of a pair of dielectric elastomer films.

    Science.gov (United States)

    Sugimoto, Takehiro; Ando, Akio; Ono, Kazuho; Morita, Yuichi; Hosoda, Kosuke; Ishii, Daisaku; Nakamura, Kentaro

    2013-11-01

    A lightweight push-pull acoustic transducer using dielectric elastomer films was proposed for use in advanced audio systems in homes. The push-pull structure consists of two dielectric elastomer films developed to serve as an electroactive polymer. The transducer utilizes the change in the surface area of the dielectric elastomer film, induced by an electric-field-induced change in the thickness, for sound generation. The resonance frequency of the transducer was derived from modeling the push-pull configuration to estimate the lower limit of the frequency range. Measurement results presented an advantage of push-pull driving in the suppression of harmonic distortion.

  17. Impact of hydrocarbon drilling mud on mud motor elastomers at different temperatures

    Science.gov (United States)

    Epikhin, A. V.; Melnikov, V. V.; Nechaeva, L. N.; Ulyanova, O. S.

    2016-09-01

    The paper describes the experimental research of hydrocarbon drilling mud impact on engineering parameters of mud motor elastomer samples. It is believed to be urgent due to an increase in using mud motors in oil and gas well construction now, and the issue of intense exploitation is currently topical. The test results of elastomer IRP- 1226 dependent on the temperature are shown in the paper. It is proved that the hydrocarbon drilling muds have a significant impact on wearing of mud motors elastomers under the condition of a temperature increase.

  18. Effect of ordered B-site cations on the structure, elastic and thermodynamic properties of KTa0.5Nb0.5O3 crystal

    Science.gov (United States)

    Yang, Wenlong; Han, Junsheng; Wang, Li; Shen, Yanqing; Li, Linjun; Yang, Yuqiang; Li, Haidong; Chen, Liangyu

    2017-07-01

    BO6 oxygen octahedral was considered as the key part in ABO3 perovskite structure, and the electro-optical, elastic and thermodynamic properties of potassium tantalate niobate (KTa0.5Nb0.5O3, abbreviated as KTN) were closely depended on the B-site Ta/Nb ratio and ordering. The effect of [100]NT, [110]NT, and [111]NT B-site cations ordering (N means a pure Nb layer parallel to ( h, k, l), T means a pure Ta layer parallel to ( h, k, l)) on structure, elastic properties and Debye temperatures properties of KTN were investigated based on density functional theory (DFT). KTN with [111]NT B-site ordering presents an cubic phase structure with excellent stability from the view of lattice properties. The elastic properties include elastic stiffness coefficients C ij , bulk modulus B, shear modulus G, Young's modulus E and Poisson' ratio ν were calculated. The elastic stiffness coefficients C 11 of KTN with B-site ordering have approached to maximum 485.506 GPa, indicating that KTN materials have better deformation ability along x axis compared with other perovskite materials. The calculated results of bulk modulus B and the shear modulus G show that KTN with [100]NT B-site ordering has stronger ability to resist fracture and plastic deformation. And the criteria B/G <1.75 suggests that KTN should be classified as a brittle material. The KTN with [100]NT B-site has excellent ductility properties compared with any other B-site arrangements. Debye temperatures of KTN with [100]NT, [110]NT, [111]NT are about 650 K, and KTN with [100]NT B-site has best thermodynamic stability.

  19. Pre-Stressed Double Network Elastomers And Hydrogels

    Science.gov (United States)

    Singh, Naveen; Lesser, Alan

    2011-03-01

    A new approach to prepare and characterize pre-stressed double network elastomers and hydrogel systems is investigated. In one example, a styrene-butadiene-styrene (SBS) tri-block copolymer system containing physical cross-links is used to achieve a pre-stressed double network by additional chemical crosslinking in a strained state using ultra-violet (UV) light. Unusual physical and mechanical properties that result from the interactions between each network are presented. These double network elastomers show a transition between competitive and collaborative behavior in their mechanical properties, as well as lower permanent set in both low and high strain regimes along with lower hysteresis. These networks exhibit lower modulus, along with lower coefficient of thermal expansion, still showing lower swelling ratios, which results from a competition of the networks. In another example, a new two-step curing schedule is utilized for Polyacrylamide based hydrogels, where a strain is induced in the middle of curing reaction. The final mechanical properties of these double network hydrogels are studied and compared to both first network and the single network formed without any step strain.

  20. Outdoor weathering of facial prosthetic elastomers differing in Durometer hardness.

    Science.gov (United States)

    Willett, Emily S; Beatty, Mark W

    2015-03-01

    Facial prosthetic elastomers with wide ranges in hardness are available, yet material weatherability is unknown. The purpose of this study was to assess color, Durometer hardness, and tensile property changes after 3000 hours of outdoor weathering. Unpigmented elastomers with Durometer hardness 5, 30, 50, 70, and A-2186 were polymerized into dumbbells (ASTM D412) and disks, 34 mm in diameter by 6 mm thick. Materials were subjected to outdoor or time passage environments for 3000 hours. CIELab color (n=5), Durometer hardness (n=5), and tensile mechanical properties (n=10) were measured at 0 and 3000 hours, and group differences were assessed by material and weathering condition (ANOVA/Tukey, α=.05). Except for A-2186, the mean Durometer changes for all materials were 1 unit or less, with no significant differences observed between time passage and weathered groups (P≥.05). Three-thousand-hour tensile mechanical property results demonstrated nonsignificant differences between time passage and weathered materials but significantly changed properties from immediately tested materials (Phardness 5 and 30 and A-2186. With a few exceptions, outdoor weathering produced relatively small changes in color, Durometer hardness, or tensile properties compared with time passage. Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

  1. Superhydrophobic/superoleophilic magnetic elastomers by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Milionis, Athanasios, E-mail: am2vy@virginia.edu [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Fragouli, Despina; Brandi, Fernando; Liakos, Ioannis; Barroso, Suset [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Athanassiou, Athanassia, E-mail: athanassia.athanassiou@iit.it [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy)

    2015-10-01

    Highlights: • We report the development of magnetic nanocomposite sheets. • Laser irradiation of the nanocomposites induces chemical and structural changes to the surface. • The laser-patterned surfaces exhibit superhydrophobicity and superoleophilicity. • The particle contribution in altering the surface and bulk properties of the material is studied. - Abstract: We report the development of magnetic nanocomposite sheets with superhydrophobic and supeoleophilic surfaces generated by laser ablation. Polydimethylsiloxane elastomer free-standing films, loaded homogeneously with 2% wt. carbon coated iron nanoparticles, were ablated by UV (248 nm), nanosecond laser pulses. The laser irradiation induces chemical and structural changes (both in micro- and nano-scale) to the surfaces of the nanocomposites rendering them superhydrophobic. The use of nanoparticles increases the UV light absorption efficiency of the nanocomposite samples, and thus facilitates the ablation process, since the number of pulses and the laser fluence required are greatly reduced compared to the bare polymer. Additionally the magnetic nanoparticles enhance significantly the superhydrophobic and oleophilic properties of the PDMS sheets, and provide to PDMS magnetic properties making possible its actuation by a weak external magnetic field. These nanocomposite elastomers can be considered for applications requiring magnetic MEMS for the controlled separation of liquids.

  2. Dielectric Elastomer Actuators for Soft Wave-Handling Systems.

    Science.gov (United States)

    Wang, Tao; Zhang, Jinhua; Hong, Jun; Wang, Michael Yu

    2017-03-01

    This article presents a soft handling system inspired by the principle of the natural wave (named Wave-Handling system) aiming to offer a soft solution to delicately transport and sort fragile items such as fruits, vegetables, biological tissues in food, and biological industries. The system consists of an array of hydrostatically coupled dielectric elastomer actuators (HCDEAs). Due to the electrostriction property of dielectric elastomers, the handling system can be controlled by electric voltage rather than the cumbersome pneumatic system. To study the working performance of the Wave-Handling system and how the performance can be improved, the basic properties of HCDEA are investigated through experiments. We find that the HCDEA exhibits some delay and hysteretic characteristics when activated by periodic voltage and the characteristics are influenced by the frequency and external force also. All this will affect the performance of the Wave-Handling system. However, the electric control, simple structure, light weight, and low cost of the soft handling system show great potential to move from laboratory to practical application. As a proof of design concept, a simply made prototype of the handling system is controlled to generate a parallel moving wave to manipulate a ball. Based on the experimental results, the improvements and future work are discussed and we believe this work will provide inspiration for soft robotic engineering.

  3. Novel Arrangements for High Performance and Durable Dielectric Elastomer Actuation

    Directory of Open Access Journals (Sweden)

    Runan Zhang

    2016-07-01

    Full Text Available This paper advances the design of Rod Pre-strained Dielectric Elastomer Actuators (RP-DEAs in their capability to generate comparatively large static actuation forces with increased lifetime via optimized electrode arrangements. RP-DEAs utilize thin stiff rods to constrain the expansion of the elastomer and maintain the in-plane pre-strain in the rod longitudinal direction. The aim is to study both the force output and the durability of the RP-DEA. Initial design of the RP-DEA had poor durability, however, it generated significantly larger force compared with the conventional DEA due to the effects of pre-strain and rod constraints. The durability study identifies the in-electro-active-region (in-AR lead contact and the non-uniform deformation of the structure as causes of pre-mature failure of the RP-DEA. An optimized AR configuration is proposed to avoid actuating undesired areas in the structure. The results show that with the optimized AR, the RP-DEA can be effectively stabilized and survive operation at least four times longer than with a conventional electrode arrangement. Finally, a Finite Element simulation was also performed to demonstrate that such AR design and optimization can be guided by analyzing the DEA structure in the state of pre-activation.

  4. Elastomer modulus and dielectric strength scaling with sample thickness

    Science.gov (United States)

    Larson, Kent

    2015-04-01

    Material characteristics such as adhesion and dielectric strength have well recognized dependencies on material thickness. There is disagreement, however, on the scale: the long held dictum that dielectric strength is inversely proportional to the square root of sample thickness has been shown to not always hold true for all materials, nor for all possible thickness regions. In D-EAP applications some studies have postulated a "critical thickness" below which properties show significantly less thickness dependency. While a great deal of data is available for dielectric strength, other properties are not nearly as well documented as samples get thinner. In particular, elastic modulus has been found to increase and elongation to decrease as sample thickness is lowered. This trend can be observed experimentally, but has been rarely reported and certainly does not appear in typical suppliers' product data sheets. Both published and newly generated data were used to study properties such as elastic modulus and dielectric strength vs sample thickness in silicone elastomers. Several theories are examined to explain such behavior, such as the impact of defect size and of common (but not well reported) concentration gradients that occur during elastomer curing that create micron-sized layers at the upper and lower interfaces with divergent properties to the bulk material. As Dielectric Electro-Active Polymer applications strive to lower and lower material thickness, changing mechanical properties must be recognized and taken into consideration for accurate electro-mechanical predictions of performance.

  5. Strong, Resilient, and Sustainable Aliphatic Polyester Thermoplastic Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Watts, Annabelle; Kurokawa, Naruki; Hillmyer, Marc A. (UMM)

    2017-05-03

    Thermoplastic elastomers (TPEs) composed of ABA block polymers exhibit a wide variety of properties and are easily processable as they contain physical, rather than chemical, cross-links. Poly(γ-methyl-ε-caprolactone) (PγMCL) is an amorphous polymer with a low entanglement molar mass (Me = 2.9 kg mol–1), making it a suitable choice for tough elastomers. Incorporating PγMCL as the midblock with polylactide (PLA) end blocks (fLA = 0.17) results in TPEs with high stresses and elongations at break (σB = 24 ± 2 MPa and εB = 1029 ± 20%, respectively) and low levels of hysteresis. The use of isotactic PLA as the end blocks (fLLA = 0.17) increases the strength and toughness of the material (σB = 30 ± 4 MPa, εB = 988 ± 30%) due to its semicrystalline nature. This study aims to demonstrate how the outstanding properties in these sustainable materials are a result of the entanglements, glass transition temperature, segment–segment interaction parameter, and crystallinity, resulting in comparable properties to the commercially relevant styrene-based TPEs.

  6. Synthesis and characterization of energetic thermoplastic elastomers for propellant formulations

    Directory of Open Access Journals (Sweden)

    Aparecida M. Kawamoto

    2009-01-01

    Full Text Available Synthesis and characterization of energetic ABA-type thermoplastic elastomers for propellant formulations has been carried out. Following the working plan elaborated, the synthesis and characterization of Poly 3- bromomethyl-3-methyl oxetane (PolyBrMMO, Poly 3- azidomethyl-3-methyl oxetane (PolyAMMO, Poly 3,3-bis-azidomethyl oxetane (PolyBAMO and Copolymer PolyBAMO/AMMO (by TDI end capping has been successfully performed. The thermoplastic elastomers (TPEs were synthesized using the chain elongation process PolyAMMO, GAP and PolyBAMO by diisocyanates. In this method 2.4-toluene diisocyanate (TDI is used to link block A (hard and mono- functional to B (soft and di-functional. For the hard A-block we used PolyBAMO and for the soft B-block we used PolyAMMO or GAP.This is a joint project set up, some years ago, between the Chemistry Division of the Institute of Aeronautics and Space (IAE - subordinated to the Brazilian Ministry of Defense - and the Fraunhofer Institut Chemische Technologie (ICT, in Germany. The products were characterized by different techniques as IR- and (1H,13CNMR spectroscopies, elemental and thermal analyses. New methodologies based on FT-IR analysis have been developed as an alternative for the determination of the molecular weight and CHNO content of the energetic polymers.

  7. EFFECTS OF TRITIUM GAS EXPOSURE ON EPDM ELASTOMER

    Energy Technology Data Exchange (ETDEWEB)

    Clark, E.

    2009-12-11

    Samples of four formulations of ethylene-propylene diene monomer (EPDM) elastomer were exposed to initially pure tritium gas at one atmosphere and ambient temperature for various times up to about 420 days in closed containers. Two formulations were carbon-black-filled commercial formulations, and two were the equivalent formulations without filler synthesized for this work. Tritium effects on the samples were characterized by measuring the sample volume, mass, flexibility, and dynamic mechanical properties and by noting changes in appearance. The glass transition temperature was determined by analysis of the dynamic mechanical properties. The glass transition temperature increased significantly with tritium exposure, and the unfilled formulations ceased to behave as elastomers after the longest tritium exposure. The filled formulations were more resistant to tritium exposure. Tritium exposure made all samples significantly stiffer and therefore much less able to form a reliable seal when employed as O-rings. No consistent change of volume or density was observed; there was a systematic lowering of sample mass with tritium exposure. In addition, the significant radiolytic production of gas, mainly protium (H{sub 2}) and HT, by the samples when exposed to tritium was characterized by measuring total pressure in the container at the end of each exposure and by mass spectroscopy of a gas sample at the end of each exposure. The total pressure in the containers more than doubled after {approx}420 days tritium exposure.

  8. A novel variable stiffness mechanism for dielectric elastomer actuators

    Science.gov (United States)

    Li, Wen-Bo; Zhang, Wen-Ming; Zou, Hong-Xiang; Peng, Zhi-Ke; Meng, Guang

    2017-08-01

    In this paper, a novel variable stiffness mechanism is proposed for the design of a variable stiffness dielectric elastomer actuator (VSDEA) which combines a flexible strip with a DEA in a dielectric elastomer minimum energy structure. The DEA induces an analog tuning of the transverse curvature of the strip, thus conveniently providing a voltage-controllable flexural rigidity. The VSDEA tends to be a fully flexible and compact structure with the advantages of simplicity and fast response. Both experimental and theoretical investigations are carried out to reveal the variable stiffness performances of the VSDEA. The effect of the clamped location on the bending stiffness of the VSDEA is analyzed, and then effects of the lengths, the loading points and the applied voltages on the bending stiffness are experimentally investigated. An analytical model is developed to verify the availability of this variable stiffness mechanism, and the theoretical results demonstrate that the bending stiffness of the VSDEA decreases as the applied voltage increases, which agree well with the experimental data. Moreover, the experimental results show that the maximum change of the relative stiffness can reach about 88.80%. It can be useful for the design and optimization of active variable stiffness structures and DEAs for soft robots, vibration control, and morphing applications.

  9. A variable stiffness dielectric elastomer actuator based on electrostatic chucking.

    Science.gov (United States)

    Imamura, Hiroya; Kadooka, Kevin; Taya, Minoru

    2017-05-14

    Dielectric elastomer actuators (DEA) are one type of promising artificial muscle; however, applications of bending-type DEA for robotic end-effectors may be limited by their low stiffness and ability to resist external loads without buckling. Unimorph DEA can produce large out-of-plane deformation suitable for use as robotic end effectors; however, design of such actuators for large displacement comes at the cost of low stiffness and blocking force. This work proposes and demonstrates a variable stiffness dielectric elastomer actuator (VSDEA) consisting of a plurality of unimorph DEA units operating in parallel, which can exhibit variable electrostatic chucking to modulate the structure's bending stiffness. The unimorph DEA units are additively manufactured using a high-resolution pneumatic dispenser, and VSDEA comprising various numbers of units are assembled. The performance of the DEA units and VSDEA are compared to model predictions, exhibiting a maximum stiffness change of 39.2×. A claw actuator comprising two VSDEA and weighing 0.6 grams is demonstrated grasping and lifting a 10 gram object.

  10. Magnetoactive elastomer as an element of a magnetic retina fixator

    Science.gov (United States)

    Makarova, L. A.; Nadzharyan, T. A.; Alekhina, Yu A.; Stepanov, G. V.; Kazimirova, E. G.; Perov, N. S.; Kramarenko, E. Yu

    2017-09-01

    We explore the possibility of creating an effective retinal fixator on the basis of magnetoactive elastomers (MAEs) and systems of permanent magnets. MAEs consist of silicone elastomer matrix with embedded magnetic iron microparticles. We study theoretically and experimentally magnetic forces acting between MAE samples and permanent magnets in various configurations. The theoretical model is based around classical magnetostatics and Maxwell equations with different parameters accounting for peculiarities of the material and the setup. Approximation of the experimentally measured magnetization curves for MAE samples was used to find input parameters for the theoretical model. To test the model, we conducted a series of experimental measurements of magnetic forces accompanied by model predictions for the system of one cylindrical magnet and a cuboid MAE sample. Calculated dependences of the average pressure arising from magnetic interactions on the distance between the closest faces of MAE samples and a permanent magnet are in a good agreement with the experimental data. The proof on concept for smaller magnetic systems required for eye surgery includes data for 10 magnets configuration and a thin MAE band. This research demonstrates high prospects of using MAE as an element of a magnetic fixator for treatment of complicated retinal detachments.

  11. Antagonistic dielectric elastomer actuator for biologically-inspired robotics

    Science.gov (United States)

    Conn, Andrew T.; Rossiter, Jonathan

    2011-04-01

    For optimal performance, actuators designed for biologically-inspired robotics applications need to be capable of mimicking the key characteristics of natural musculoskeletal systems. These characteristics include a large output stroke, high energy density, antagonistic operation and passive compliance. The actuation properties of dielectric elastomer actuators (DEAs) make them viable for use as an artificial muscle technology. However, much like the musculoskeletal system, rigid structures are needed to couple the compliant DEA layers to a load. In this paper, a cone DEA design is developed as an antagonistic, multi-DOF actuator, viable for a variety for biologically-inspired robotics applications. The design has the advantage of maintaining pre-strain through a support structure without substantially lowering the overall mass-specific power density. Prototype cone DEAs have been fabricated with VHB 4910 acrylic elastomer and have characteristic dimensions of 49mm (strut length) and 60mm (DEA diameter). Multi-DOF kinematical outputs of the cone DEAs were measured using a custom 3D motion tracking system. Experimental tests of the prototypes demonstrate antagonistic linear (+/-10mm), rotational (+/-25°) and combined multi-DOF strokes. Overall, antagonistic cone DEAs are shown to produce a complex multi-DOF output from a mass-efficient support structure and thus are well suited for being exploited in biologically-inspired robotics.

  12. Dielectric elastomer vibrissal system for active tactile sensing

    Science.gov (United States)

    Conn, Andrew T.; Pearson, Martin J.; Pipe, Anthony G.; Welsby, Jason; Rossiter, Jonathan

    2012-04-01

    Rodents are able to dexterously navigate confined and unlit environments by extracting spatial and textural information with their whiskers (or vibrissae). Vibrissal-based active touch is suited to a variety of applications where vision is occluded, such as search-and-rescue operations in collapsed buildings. In this paper, a compact dielectric elastomer vibrissal system (DEVS) is described that mimics the vibrissal follicle-sinus complex (FSC) found in rodents. Like the vibrissal FSC, the DEVS encapsulates all sensitive mechanoreceptors at the root of a passive whisker within an antagonistic muscular system. Typically, rats actively whisk arrays of macro-vibrissae with amplitudes of up to +/-25°. It is demonstrated that these properties can be replicated by exploiting the characteristic large actuation strains and passive compliance of dielectric elastomers. A prototype DEVS is developed using VHB 4905 and embedded strain gauges bonded to the root of a tapered whisker. The DEVS is demonstrated to produce a maximum rotational output of +/-22.8°. An electro-mechanical model of the DEVS is derived, which incorporates a hyperelastic material model and Euler- Bernoulli beam equations. The model is shown to predict experimental measurements of whisking stroke amplitude and whisker deflection.

  13. Experimental investigations on energy harvesting performance of dielectric elastomers

    Science.gov (United States)

    Wang, Yongquan; Liu, Xuejing; Xue, Huanhuan; Chen, Hualing; Jia, Shuhai

    2014-03-01

    In this paper, the emerging technology of energy harvesting based on dielectric elastomers (DE), a new type of functional materials belonging to the family of Electroactive Polymers (EAPs), is presented with emphasis on its performance characteristics and some key influencing factors. At first, on the basic principle of DE energy harvesting, the effects of some control parameters are theoretically analyzed under certain mechanical and electrical constraints. Then, a type of annular DE generator using the commercial elastomers of VHB 4910 (3M, USA), is specially designed and fabricated. A series of experimental tests for the device's energy harvesting performance are implemented at different pre-stretch ratios, stretch amplitudes (displacements), and bias voltages in the constant charge (open-circuit) condition. The experiment results demonstrate the associated influence laws of the above control parameters on the performance of the DE generator, and have good consistent with those obtained from the theoretical analysis. This study is expected to provide a helpful guidance for the design and operation of practical DE energy harvesting devices/systems.

  14. Multifunctional shape memory electrodes for dielectric elastomer actuators enabling high holding force and low-voltage multisegment addressing

    Science.gov (United States)

    McCoul, David; Rosset, Samuel; Besse, Nadine; Shea, Herbert

    2017-02-01

    Dielectric elastomer actuators (DEAs) are an attractive form of electromechanical transducer, possessing high energy densities, an efficient design, mechanical flexibility, high speed, and noiseless operation. They have been incorporated into a variety of elegant devices, such as microfluidic devices, tunable optics, haptic displays, and minimum-energy grippers. Dielectric elastomer minimum energy structures (DEMESs) take advantage of the prestretch of the DEA to bend a non-stretchable but flexible component to perform mechanical work. The gripper is perhaps the most intuitive type of DEMES, capable of grasping objects but with only small to moderate forces. We present a novel configuration of a DEA using electrodes made of a conductive shape-memory polymer (SMP), incorporated into the design of a gripper. The SMP electrodes allow the DEA to be rigid in the cold state, offering greater holding force than a conventional gripper. Joule heating applied to the SMP electrodes softens them, allowing for electrostatic actuation. Cooling then locks in the actuated position without the need for continued power to be supplied. Additionally, the Joule heating voltage is at least one order of magnitude less than electrostatic actuation voltages, allowing for addressing of multiple actuator elements using commercially available transistors. The shape memory gripper incorporates this addressing into its design, enabling the three segments of each finger to be controlled independently.

  15. The Abrasive Wear Resistance of the Segmented Linear Polyurethane Elastomers Based on a Variety of Polyols as Soft Segments

    Directory of Open Access Journals (Sweden)

    Konrad Kwiatkowski

    2017-12-01

    Full Text Available The presented results make an original contribution to the development of knowledge on the prediction and/or modeling of the abrasive wear properties of polyurethanes. A series of segmented linear polyurethane elastomers (PUR—In which the hard segments consist of 4,4′-methylene bis(phenylisocyanate and 1,4-butanodiol, whilst polyether, polycarbonate, or polyester polyols constitute the soft segments—Were synthesized and characterized. The hardness and wear performance as functions of the variable chemical composition of polyurethane elastomers were evaluated in order to define the relationship between studied factors. The microstructure was characterized in detail, including analysis of the hydrogen bonding by Fourier transformed infrared (FT-IR spectroscopy and the phase structure by X-ray scattering (WAXS and differential scanning calorimetry (DSC methods. The presented studies provide the key features of the polymer composition affecting the abrasive resistance as well as attempts to explain the origin of the differences in the polyurethane elastomers’ performance.

  16. Anisotropic Dye Adsorption and Anhydrous Proton Conductivity in Smectic Liquid Crystal Networks: The Role of Cross-Link Density, Order, and Orientation.

    Science.gov (United States)

    Liang, Ting; van Kuringen, Huub P C; Mulder, Dirk J; Tan, Shuai; Wu, Yong; Borneman, Zandrie; Nijmeijer, Kitty; Schenning, Albertus P H J

    2017-10-11

    In this work, the decisive role of rigidity, orientation, and order in the smectic liquid crystalline network on the anisotropic proton and adsorbent properties is reported. The rigidity in the hydrogen-bonded polymer network has been altered by changing the cross-link density, the order by using different mesophases (smectic, nematic, and isotropic phases), whereas the orientation of the mesogens was controlled by alignment layers. Adding more cross-linkers improved the integrity of the polymer films. For the proton conduction, an optimum was found in the amount of cross-linker and the smectic organization results in the highest anhydrous proton conduction. The polymer films show anisotropic proton conductivity with a 54 times higher conductivity in the direction perpendicular to the molecular director. After a base treatment of the smectic liquid crystalline network, a nanoporous polymer film is obtained that also shows anisotropic adsorption of dye molecules and again straight smectic pores are favored over disordered pores in nematic and isotropic networks. The highly cross-linked films show size-selective adsorption of dyes. Low cross-linked materials do not show this difference due to swelling, which decreases the order and creates openings in the two-dimensional polymer layers. The latter is, however, beneficial for fast adsorption kinetics.

  17. Toughening modification of poly(butylene terephthalate)/poly(ethylene terephthalate) blends by an epoxy-functionalized elastomer

    Science.gov (United States)

    Zhang, Weizhou; Wang, Kai; Yan, Wei; Guo, Weihong

    2017-10-01

    New toughened poly(butylene terephthalate) (PBT)/poly(ethylene terephthalate) (PET) (40/60 wt%) blends were obtained by melting with Glycidyl methacrylate grafted poly(ethylene octane) copolymer (POE-g-GMA), varying the POE-g-GMA content up to 20 wt%, in a twin-screw extruder, followed by injection molding. The influence of POE-g-GMA on the properties of the PBT/PET blends was investigated by mechanical testing, Fourier transform infrared (FT-IR) analysis, gel fractions analysis, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and scanning electronic microscopy (SEM). The mechanical testing results indicated that the incorporation of POE-g-GMA led to increases in the notched impact strength and decreases in the tensile strength, flexural strength, and flexural modulus. When POE-g-GMA content reached 20 wt%, the notched impact strength (8.0 kJ m‑2) was achieved for the PBT/PET/POE-g-GMA blends. FT-IR results proved that some PBT/PET/POE-g-GMA copolymers were produced, which improved the compatibility between POE-g-GMA and the PBT/PET matrix. The extent of crosslinking was observed by gel fraction measurements. DMA results further testified chain-extending and micro-crosslink reactions occurred between POE-g-GMA and PBT/PET blends. In addition, the reactions induced by POE-g-GMA affected the crystallization behavior of PBT/PET blends obviously, as observed from DSC results. By means of SEM observation of the impact fracture surface morphology, and the discussion of the micro-crosslink reaction process between the epoxide-containing elastomers and PBT/PET matrix, the toughening mechanism was proposed to be taken into account the shear yielding of PBT/PET matrix and cavitation of elastomer particles.

  18. The superacid HBr/AlBr(3) : protonation of benzene and ordered crystal structure of [C(6)H(7)](+)[Al(2)Br(7)](-).

    Science.gov (United States)

    Scholz, Franziska; Himmel, Daniel; Eisele, Lea; Unkrig, Wiebke; Krossing, Ingo

    2014-02-03

    Crystalline and properly ordered protonated benzene as the [C6 H7 ](+) [Al2 Br7 ](-) ⋅(C6 H6 ) salt 1 are obtained by the combination of solid AlBr3 , benzene, and HBr gas. Compound 1 was characterized and verified by NMR, Raman and X-Ray spectroscopy. This unexpected simple and straight forward access shows that HBr/AlBr3 is an underestimated superacid that should be used more frequently. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. A small biomimetic quadruped robot driven by multistacked dielectric elastomer actuators

    Science.gov (United States)

    Nguyen, Canh Toan; Phung, Hoa; Dat Nguyen, Tien; Lee, Choonghan; Kim, Uikyum; Lee, Donghyouk; Moon, Hyungpil; Koo, Jachoon; Nam, Jae-do; Ryeol Choi, Hyouk

    2014-06-01

    A kind of dielectric elastomer (DE) material, called ‘synthetic elastomer’, has been developed based on acrylonitrile butadiene rubber (NBR) to be used as a dielectric elastomer actuator (DEA). By stacking single layers of synthetic elastomer, a linear actuator, called a multistacked actuator, is produced, and used by mechatronic and robotic systems to generate linear motion. In this paper, we demonstrate the application of the multistacked dielectric elastomer actuator in a biomimetic legged robot. A miniature robot driven by a biomimetic actuation system with four 2-DOF (two-degree-of-freedom) legged mechanisms is realized. Based on the experimental results, we evaluate the performance of the proposed robot and validate the feasibility of the multistacked actuator in a locomotion system as a replacement for conventional actuators.

  20. Novel encapsulation technique for incorporation of high permittivity fillers into silicone elastomers

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Hvilsted, Søren; Skov, Anne Ladegaard

    2014-01-01

    The research on soft elastomers with high dielectric permittivity for the use as dielectric electroactive polymers (DEAP) has grown substantially within the last decade. The approaches to enhance the dielectric permittivity can be categorized into three main classes: 1) Mixing or blending in high...... permittivity fillers, 2) Grafting of high permittivity molecules onto the polymer backbone in the elastomer, and 3) Encapsulation of high permittivity fillers. The approach investigated here is a new type of encapsulation which does not interfere with the mechanical properties to the same content...... as for the traditionally applied thermoplastic encapsulation. The properties of the elastomers are investigated as function of the filler content and type. The dielectric permittivity, dielectric loss, conductivity, storage modulus as well as viscous loss are compared to elastomers with the same amounts of high...

  1. Three-dimensional structure of olefinic thermoplastic elastomer blends using electron tomography

    NARCIS (Netherlands)

    Sengupta, P.; Noordermeer, Jacobus W.M.

    2005-01-01

    The present communication reports the first use of electron tomography in reconstructing the three-dimensional morphology in thermoplastic elastomer blends. The blends investigated were dynamically vulcanized blends of ethylene-propylene-diene (EPDM) rubber/poly(propylene)/oil and

  2. Mechanically Stretchable and Electrically Insulating Thermal Elastomer Composite by Liquid Alloy Droplet Embedment

    Science.gov (United States)

    Jeong, Seung Hee; Chen, Si; Huo, Jinxing; Gamstedt, Erik Kristofer; Liu, Johan; Zhang, Shi-Li; Zhang, Zhi-Bin; Hjort, Klas; Wu, Zhigang

    2015-01-01

    Stretchable electronics and soft robotics have shown unsurpassed features, inheriting remarkable functions from stretchable and soft materials. Electrically conductive and mechanically stretchable materials based on composites have been widely studied for stretchable electronics as electrical conductors using various combinations of materials. However, thermally tunable and stretchable materials, which have high potential in soft and stretchable thermal devices as interface or packaging materials, have not been sufficiently studied. Here, a mechanically stretchable and electrically insulating thermal elastomer composite is demonstrated, which can be easily processed for device fabrication. A liquid alloy is embedded as liquid droplet fillers in an elastomer matrix to achieve softness and stretchability. This new elastomer composite is expected useful to enhance thermal response or efficiency of soft and stretchable thermal devices or systems. The thermal elastomer composites demonstrate advantages such as thermal interface and packaging layers with thermal shrink films in transient and steady-state cases and a stretchable temperature sensor. PMID:26671673

  3. Synthesis of microbial elastomers based on soybean oily acids. Biocompatibility studies

    Energy Technology Data Exchange (ETDEWEB)

    Hazer, Derya Burcu [Department of Neurosurgery, Faculty of Medicine, School of Medicine, Hacettepe University, Sihhiye, 06100 Ankara (Turkey); Hazer, Baki [Department of Chemistry, Zonguldak Karaelmas University, 67100 Zonguldak (Turkey); Kaymaz, Figen, E-mail: burcuhazer@hotmail.co, E-mail: bkhazer@karaelmas.edu.t [Department of Histology, Faculty of Medicine, School of Medicine, Hacettepe University, Sihhiye, 06100 Ankara (Turkey)

    2009-06-15

    Biocompatibility studies of the autoxidized and unoxidized unsaturated medium-long chain length (m-lcl) co-poly-3-hydroxyalkanoates (m-lclPHAs) derived from soya oily acids have been reported. Pseudomonas oleovorans was grown on a series of mixtures of octanoic acid (OA) and soya oily acids (Sy) with weight ratios of 20:80, 28:72 and 50:50 in order to obtain unsaturated m-lcl copolyesters coded PHO-Sy-2080, PHO-Sy-2872 and PHO-Sy-5050, respectively. The PHA films were obtained by solvent cast from CHCl{sub 3}. They were all originally sticky and waxy except PHO-Sy-5050. Autoxidation of the unsaturated copolyester films was carried out on exposure to air at room temperature in order to obtain crosslinked polymers. They became a highly flexible elastomer after being autoxidized (about 40 days of autoxidation). The in vivo tissue reactions of the autoxidized PHAs were evaluated by subcutaneous implantation in rats. The rats appeared to be healthy throughout the implantation period. No symptom such as necrosis, abscess or tumorigenesis was observed in the vicinity of the implants. Retrieved materials varied in their physical appearance after 6 weeks of implantation. In vivo biocompatibility studies of the medical applications indicated that the microbial copolyesters obtained were all biocompatible and especially the PHOSy series of copolyesters had the highest biocompatibility among them.

  4. Low Modulus Silicone Elastomer Networks with Desirable Viscoelastic Properties for Cell Mobility Studies

    Science.gov (United States)

    Albert, Julie N. L.; Genzer, Jan

    2013-03-01

    Biocompatible silicone elastomer networks provide a versatile platform for studying the effect of compliance on cell movement. In conventional network formation schemes, poly(dimethylsiloxane) (PDMS) is cross-linked via reactive end groups, and the modulus of the material is controlled by the ratio of polymer to cross-linker. However, low modulus networks fabricated in this manner are imperfect and insufficiently cross-linked with high soluble fractions and reduced elasticity, especially as the network modulus approaches that of soft tissues (on the order of 10 kPa). In order to overcome these limitations, we synthesized PDMS chains in which vinylmethylsiloxane units were incorporated every ~15-20 kDa along the polymer backbone. We then cross-linked the polymer through the vinyl groups using hydrosilylation chemistry. The resultant networks exhibited lower soluble fractions and lower viscous dissipation/greater elasticity as compared to equivalent-modulus networks fabricated by the conventional end-group cross-linking scheme. We attribute the mechanical properties of our networks to the presence of network-bound free chain ends that effectively plasticize the network to lower the modulus without compromising network elasticity.

  5. Magneto-responsive liquid crystalline elastomer nanocomposites as potential candidates for dynamic cell culture substrates

    Energy Technology Data Exchange (ETDEWEB)

    Herrera-Posada, Stephany; Mora-Navarro, Camilo; Ortiz-Bermudez, Patricia; Torres-Lugo, Madeline [Department of Chemical Engineering, Call Box 9000, University of Puerto Rico, Mayagüez PR 00681 (Puerto Rico); McElhinny, Kyle M.; Evans, Paul G. [Department of Materials Science and Engineering, 1509 University Avenue, University of Wisconsin-Madison, WI 53706 (United States); Calcagno, Barbara O. [Department of General Engineering, Call Box 9000, University of Puerto Rico, Mayagüez PR 00681 (Puerto Rico); Acevedo, Aldo, E-mail: aldo.acevedo@upr.edu [Department of Chemical Engineering, Call Box 9000, University of Puerto Rico, Mayagüez PR 00681 (Puerto Rico)

    2016-08-01

    Recently, liquid crystalline elastomers (LCEs) have been proposed as active substrates for cell culture due to their potential to attach and orient cells, and impose dynamic mechanical signals through the application of external stimuli. In this report, the preparation of anisotropic and oriented nematic magnetic-sensitized LCEs with iron oxide nanoparticles, and the evaluation of the effect of particle addition at low concentrations on the resultant structural, thermal, thermo-mechanical, and mechanical properties is presented. Phase transformations produced by heating in alternating magnetic fields were investigated in LCEs in contact with air, water, and a common liquid cell culture medium was also evaluated. The inclusion of nanoparticles into the elastomers displaced the nematic-to-isotropic phase transition, without affecting the nematic structure as evidenced by similar values of the order parameter, while reducing the maximum thermomechanical deformations. Remote and reversible deformations of the magnetic LCEs were achieved through the application of alternating magnetic fields, which induces the nematic–isotropic phase transition through nanoparticle heat generation. Formulation parameters can be modified to allow for remote actuation at values closer to the human physiological temperature range and within the range of deformations that can affect the cellular behavior of fibroblasts. Finally, a collagen surface treatment was performed to improve compatibility with NIH-3T3 fibroblast cultures, which enabled the attachment and proliferation of fibroblasts on substrates with and without magnetic particles under quiescent conditions. The LCEs developed in this work, which are able to deform and experience stress changes by remote contact-less magnetic stimulation, may allow for further studies on the effect of substrate morphology changes and dynamic mechanical properties during in vitro cell culture. - Highlights: • Magnetic LCE nanocomposites were

  6. Dry Rolling Friction and Wear of Elastomer Systems and Their Finite Element Modelling

    OpenAIRE

    Xu, Dan

    2009-01-01

    Elastomers and their various composites, and blends are frequently used as engineering working parts subjected to rolling friction movements. This fact already substantiates the importance of a study addressing the rolling tribological properties of elastomers and their compounds. It is worth noting that until now the research and development works on the friction and wear of rubber materials were mostly focused on abrasion and to lesser extent on sliding type of loading. As the tribological ...

  7. Change in color of a maxillofacial prosthetic silicone elastomer, following investment in molds of different materials

    OpenAIRE

    Sethi, Tania; Kheur, Mohit; Coward, Trevor; Patel, Naimesha

    2015-01-01

    Purpose: In the authors? experience, the color of silicone elastomer following polymerization in molds made of gypsum products is slightly different from the color that was matched in the presence of the patient, before the silicone is packed. It is hypothesized that the investing materials and separating media have an effect on the color during the polymerization process of the silicone. Materials and Methods: This study compares and evaluates the change in color of silicone elastomer packed...

  8. Green silicone elastomer obtained from a counterintuitively stable mixture of glycerol and PDMS

    DEFF Research Database (Denmark)

    Mazurek, P.; Hvilsted, S.; Skov, A. L.

    2016-01-01

    and scanning electron microscopy. The materials were proven additionally to exhibit a strong affinity to water, which was investigated by simple water absorption tests. Incorporating glycerol into PDMS decreased the Young's modulus of the composites yet the ultimate strain of the elastomer was not compromised......, even in the presence of very high loadings. The conducted experiments highlight the great potential of this new type of elastomer and reveal some possible applications....

  9. From boots to buoys: promises and challenges of dielectric elastomer energy harvesting

    Science.gov (United States)

    Kornbluh, Roy D.; Pelrine, Ron; Prahlad, Harsha; Wong-Foy, Annjoe; McCoy, Brian; Kim, Susan; Eckerle, Joseph; Low, Tom

    2011-04-01

    Dielectric elastomers offer the promise of energy harvesting with few moving parts. Power can be produced simply by stretching and contracting a relatively low-cost rubbery material. This simplicity, combined with demonstrated high energy density and high efficiency, suggests that dielectric elastomers are promising for a wide range of energy harvesting applications. Indeed, dielectric elastomers have been demonstrated to harvest energy from human walking, ocean waves, flowing water, blowing wind, and pushing buttons. While the technology is promising, there are challenges that must be addressed if dielectric elastomers are to be a successful and economically viable energy harvesting technology. These challenges include developing materials and packaging that sustains long lifetime over a range of environmental conditions, design of the devices that stretch the elastomer material, as well as system issues such as practical and efficient energy harvesting circuits. Progress has been made in many of these areas. We have demonstrated energy harvesting transducers that have operated over 5 million cycles. We have also shown the ability of dielectric elastomer material to survive for months underwater while undergoing voltage cycling. We have shown circuits capable of 78% energy harvesting efficiency. While the possibility of long lifetime has been demonstrated at the watt level, reliably scaling up to the power levels required for providing renewable energy to the power grid or for local use will likely require further development from the material through to the systems level.

  10. Starch-based bio-elastomers functionalized with red beetroot natural antioxidant.

    Science.gov (United States)

    Tran, Thi Nga; Athanassiou, Athanassia; Basit, Abdul; Bayer, Ilker S

    2017-02-01

    Red beetroot (RB) powder was incorporated into starch-based bio-elastomers to obtain flexible biocomposites with tunable antioxidant properties. Starch granules within the bio-elastomers affected the release of the antioxidant molecule betanin in the RB powder. The bio-elastomers were hydrophobic and resisted dissolution in water, hence the release of betanin was due to diffusion rather than polymer matrix disintegration. Hydrophobicity was maintained even after water immersion. Released betanin demonstrated highly efficient antioxidant scavenging activity against 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(+)). RB powder was also found to increase the Young's modulus of the bio-elastomers without compromising their elongation ability. Infrared spectral analysis indicated weak interactions through hydrogen bonding among starch granules, RB powder and PDMS polymer within the bio-elastomers. Hence, as a simple but intelligent biomaterial consisting of mainly edible starch and RB powder the present bio-elastomers can be used in active packaging for a variety of pharmaceutical, medical, and food applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Comparison of Adhesion and Retention Forces for Two Candidate Docking Seal Elastomers

    Science.gov (United States)

    Hartzler, Brad D.; Panickar, Marta B.; Wasowski, Janice L.; Daniels, Christopher C.

    2011-01-01

    To successfully mate two pressurized vehicles or structures in space, advanced seals are required at the interface to prevent the loss of breathable air to the vacuum of space. A critical part of the development testing of candidate seal designs was a verification of the integrity of the retaining mechanism that holds the silicone seal component to the structure. Failure to retain the elastomer seal during flight could liberate seal material in the event of high adhesive loads during undocking. This work presents an investigation of the force required to separate the elastomer from its metal counter-face surface during simulated undocking as well as a comparison to that force which was necessary to destructively remove the elastomer from its retaining device. Two silicone elastomers, Wacker 007-49524 and Esterline ELASA-401, were evaluated. During the course of the investigation, modifications were made to the retaining devices to determine if the modifications improved the force needed to destructively remove the seal. The tests were completed at the expected operating temperatures of -50, +23, and +75 C. Under the conditions investigated, the comparison indicated that the adhesion between the elastomer and the metal counter-face was significantly less than the force needed to forcibly remove the elastomer seal from its retainer, and no failure would be expected.

  12. Polyamide 4,6 nanocomposites with and without the use of a maleated polyolefin elastomer as a toughener

    Energy Technology Data Exchange (ETDEWEB)

    Chiu, Fang-Chyou, E-mail: maxson@mail.cgu.edu.tw [Department of Chemical and Materials Engineering, Chang Gung University, Tao-Yuan 333, Taiwan (China); Deng, Tsung-Lin [Department of Chemical and Materials Engineering, Chang Gung University, Tao-Yuan 333, Taiwan (China)

    2011-02-15

    In this study, polyamide 4,6 (PA 4,6)-based nanocomposites were successfully prepared using a twin screw extruder. A commercial organo-montmorillonite (denoted as 30B) and a commercial maleated polyolefin elastomer (denoted as POEMA) served as the reinforcing filler and toughener, respectively. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results confirmed the nano-scaled dispersion of 30B in the composites. Nevertheless, the presence of POEMA slightly depreciated the dispersibility of 30B. Polarized light microscope (PLM) observations showed that the inclusions of 30B and POEMA led to the formation of diffused/broken PA 4,6 spherulites. Differential scanning calorimetry (DSC) results indicated that the addition of 30B retarded the crystallization of PA 4,6; the addition of POEMA led to a similar retardation effect on PA 4,6 crystallization. Interesting melting behaviors associated mainly with the crystal annealing of PA 4,6 upon heating were observed for the fast-cooled samples. The presence of POEMA was noted to hamper the annealing process of PA 4,6 crystals. The thermal stability enhancement of PA 4,6 in the presence of 30B was further raised to a higher extent when POEMA was included in the matrix. The rigidity, including the storage/Young's/flexural moduli, of PA 4,6 significantly increased after adding 30B. These properties, however, declined after the additional incorporation of POEMA. The PA 4,6/POEMA/30B nanocomposites basically displayed balanced impact strength between those of the neat PA 4,6 and PA 4,6/POEMA blends.

  13. Stretchable biocompatible electronics by embedding electrical circuitry in biocompatible elastomers.

    Science.gov (United States)

    Jahanshahi, Amir; Salvo, Pietro; Vanfleteren, Jan

    2012-01-01

    Stretchable and curvilinear electronics has been used recently for the fabrication of micro systems interacting with the human body. The applications range from different kinds of implantable sensors inside the body to conformable electrodes and artificial skins. One of the key parameters in biocompatible stretchable electronics is the fabrication of reliable electrical interconnects. Although very recent literature has reported on the reliability of stretchable interconnects by cyclic loading, work still needs to be done on the integration of electrical circuitry composed of rigid components and stretchable interconnects in a biological environment. In this work, the feasibility of a developed technology to fabricate simple electrical circuits with meander shaped stretchable interconnects is presented. Stretchable interconnects are 200 nm thin Au layer supported with polyimide (PI). A stretchable array of light emitting diodes (LEDs) is embedded in biocompatible elastomer using this technology platform and it features a 50% total elongation.

  14. Thermoplastic Polyurethane Elastomer Nanocomposites: Morphology, Thermophysical, and Flammability Properties

    Directory of Open Access Journals (Sweden)

    Wai K. Ho

    2010-01-01

    Full Text Available Novel materials based on nanotechnology creating nontraditional ablators are rapidly changing the technology base for thermal protection systems. Formulations with the addition of nanoclays and carbon nanofibers in a neat thermoplastic polyurethane elastomer (TPU were melt-compounded using twin-screw extrusion. The TPU nanocomposites (TPUNs are proposed to replace Kevlar-filled ethylene-propylene-diene-monomer rubber, the current state-of-the-art solid rocket motor internal insulation. Scanning electron microscopy analysis was conducted to study the char characteristics of the TPUNs at elevated temperatures. Specimens were examined to analyze the morphological microstructure during the pyrolysis reaction and in fully charred states. Thermophysical properties of density, specific heat capacity, thermal diffusivity, and thermal conductivity of the different TPUN compositions were determined. To identify dual usage of these novel materials, cone calorimetry was employed to study the flammability properties of these TPUNs.

  15. Thermal stability of segmented polyurethane elastomers reinforced by clay particles

    Directory of Open Access Journals (Sweden)

    Pavličević Jelena

    2009-01-01

    Full Text Available The aim of this work was to determine the influence of clay nanoparticles on thermal properties of segmented polyurethanes based on hexamethylene- diisocyanate, aliphatic polycarbonate diol and 1,4-butanediol as chain extender. The organically modified particles of montmorillonite and bentonite were used as reinforcing fillers. The structure of elastomeric materials was varied either by diol type or chain extender content. The ratio of OH groups from diol and chain extender (R was either 1 or 10. Thermal properties of prepared materials were determined using modulated differential scanning calorimetry (MDSC. Thermal stability of obtained elastomers has been studied by simultaneously thermogravimetry coupled with DSC. The glass transition temperature, Tg, of soft segments for all investigated samples was about -33°C. On the basis of DTG results, it was concluded that obtained materials were very stable up to 300°C.

  16. Thermal performance of an elastomer subjected to radiant heating

    Science.gov (United States)

    Hender, D. R.; Cross, C. R.

    1981-06-01

    This paper describes a test technique and modeling procedure that has been developed to provide an accurate thermal response model for a one-dimensional subliming ablation analysis code. Thin foil thermocouples are molded into the elastomer at different depths and tests are run at a broad range of radiant heat rates, thereby developing accurate temperature response data. Several test runs are made at a low heat flux to enable verification or adjustment of thermophysical properties measured in the laboratory. The modeling procedure consists of establishing a set of thermal properties and ablation parameters that match the test data over the range of test conditions. An NBR/EPDM blend material was used in the testing and modeling reported in this paper.

  17. Multiphase design of autonomic self-healing thermoplastic elastomers

    Science.gov (United States)

    Chen, Yulin; Kushner, Aaron M.; Williams, Gregory A.; Guan, Zhibin

    2012-06-01

    The development of polymers that can spontaneously repair themselves after mechanical damage would significantly improve the safety, lifetime, energy efficiency and environmental impact of man-made materials. Most approaches to self-healing materials require the input of external energy, healing agents, solvent or plasticizer. Despite intense research in this area, the synthesis of a stiff material with intrinsic self-healing ability remains a key challenge. Here, we show a design of multiphase supramolecular thermoplastic elastomers that combine high modulus and toughness with spontaneous healing capability. The designed hydrogen-bonding brush polymers self-assemble into a hard-soft microphase-separated system, combining the enhanced stiffness and toughness of nanocomposites with the self-healing capability of dynamic supramolecular assemblies. In contrast to previous self-healing polymers, this new system spontaneously self-heals as a single-component solid material at ambient conditions, without the need for any external stimulus, healing agent, plasticizer or solvent.

  18. Visual implant elastomer mark retention through metamorphosis in amphibian larvae

    Science.gov (United States)

    Campbell Grant, Evan H.

    2008-01-01

    Questions in population ecology require the study of marked animals, and marks are assumed to be permanent and not overlooked by observers. I evaluated retention through metamorphosis of visual implant elastomer marks in larval salamanders and frogs and assessed error in observer identification of these marks. I found 1) individual marks were not retained in larval wood frogs (Rana sylvatica), whereas only small marks were likely to be retained in larval salamanders (Eurycea bislineata), and 2) observers did not always correctly identify marked animals. Evaluating the assumptions of marking protocols is important in the design phase of a study so that correct inference can be made about the population processes of interest. This guidance should be generally useful to the design of mark–recapture studies, with particular application to studies of larval amphibians.

  19. Thermoplastic Dielectric Elastomer of Triblock Copolymer with High Electromechanical Performance.

    Science.gov (United States)

    Ma, Zipeng; Xie, Yuhan; Mao, Jie; Yang, Xuxu; Li, Tiefeng; Luo, Yingwu

    2017-08-01

    Dielectric elastomer (DE) actuators have been shown to have promising applications as soft electromechanical transducers in many emerging technologies. The DE actuators, which are capable of large actuation strain over a wide range of excitation frequencies, are highly desirable. Here, the first single-component DE of a triblock copolymer with attractive electromechanical performance is reported. Symmetric poly(styrene-b-butyl acrylate-b-styrene) (SBAS) is designed and synthesized. The SBAS actuator exhibits about 100% static actuation area strain and excellent dynamic performance, as evidenced by a wide half bandwidth of 300 Hz and a very high specific power of 1.2 W g-1 within the excitation frequency range of 300-800 Hz. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. A solid-state dielectric elastomer switch for soft logic

    Energy Technology Data Exchange (ETDEWEB)

    Chau, Nixon [Biomimetics Laboratory, Auckland Bioengineering Institute, The University of Auckland, Level 6, 70 Symonds Street, Auckland 1010 (New Zealand); Slipher, Geoffrey A., E-mail: geoffrey.a.slipher.civ@mail.mil; Mrozek, Randy A. [U.S. Army Research Laboratory, 2800 Powder Mill Road, Adelphi, Maryland 20783 (United States); O' Brien, Benjamin M. [StretchSense, Ltd., 27 Walls Rd., Penrose, Auckland 1061 (New Zealand); Anderson, Iain A. [Biomimetics Laboratory, Auckland Bioengineering Institute, The University of Auckland, Level 6, 70 Symonds Street, Auckland 1010 (New Zealand); StretchSense, Ltd., 27 Walls Rd., Penrose, Auckland 1061 (New Zealand); Department of Engineering Science, School of Engineering, The University of Auckland, Level 3, 70 Symonds Street, Auckland 1010 (New Zealand)

    2016-03-07

    In this paper, we describe a stretchable solid-state electronic switching material that operates at high voltage potentials, as well as a switch material benchmarking technique that utilizes a modular dielectric elastomer (artificial muscle) ring oscillator. The solid-state switching material was integrated into our oscillator, which self-started after 16 s and performed 5 oscillations at a frequency of 1.05 Hz with 3.25 kV DC input. Our materials-by-design approach for the nickel filled polydimethylsiloxane based switch has resulted in significant improvements over previous carbon grease-based switches in four key areas, namely, sharpness of switching behavior upon applied stretch, magnitude of electrical resistance change, ease of manufacture, and production rate. Switch lifetime was demonstrated to be in the range of tens to hundreds of cycles with the current process. An interesting and potentially useful strain-based switching hysteresis behavior is also presented.

  1. Numerical investigation of smart base isolation system employing MR elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Usman, M; Sung, S H; Jang, D D; Jung, H J [Department of Civil and Environmental Engineering, KAIST, 305-701, Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Koo, J H [Department of Mechanical and Manufacturing Engineering, Miami University, Oxford, Ohio 45056 (United States)], E-mail: hjung@kaist.ac.kr

    2009-02-01

    This paper evaluates the dynamic performance of a newly proposed smart base isolation system employing Magneto-Rheological Elastomers (MREs). MREs belong to a class of smart materials whose elastic modulus or stiffness can be adjusted by varying the magnitude of the magnetic field. The base isolation systems are considered as one of the most effective devices for vibration reduction of civil engineering structures in the event of earthquakes. The proposed base isolation system strives to enhance the performance of the conventional base-isolation system by using controllable MREs. To validate the effectiveness of the MRE-based isolation system, an extensive simulation study has been performed using a five degree-of-freedom structure under several historical earthquake excitations. The results show that the proposed system outperformed the conventional system in reducing the responses of the structure in all the seismic excitations considered in the study.

  2. Dielectric-elastomer-based fabrication method for varifocal microlens array.

    Science.gov (United States)

    Wang, Lihui; Hayakawa, Tomohiko; Ishikawa, Masatoshi

    2017-12-11

    We report on a method to fabricate a varifocal microlens array that employs a dielectric elastomer (DE) sandwiched between two electrodes as the lens material. The microlens array is patterned on the electrode plates, and when the electrodes are subjected to a controllable operating voltage, the DE material is "squeezed" by the Maxwell force to deform the lens array pattern, thus resulting in curvature deformation yielding a tunable lens profile. The tunable focal length performance ranges from 950 mm to infinity. When compared with liquid-filled lenses, solid-based varifocal lenses are more robust to thermal expansion, gravity, and vibrational motion. Our approach can be utilized in applications such as machine vision systems.

  3. Experimental study on the dielectric properties of polyacrylate dielectric elastomer

    Science.gov (United States)

    Qiang, Junhua; Chen, Hualing; Li, Bo

    2012-02-01

    The dielectric constant of elastomeric dielectric material is an essential physical parameter, whose value may affect the electromechanical deformation of a dielectric elastomer actuator. Since the dielectric constant is influenced by several external factors as reported before, and no certain value has been confirmed to our knowledge, in the present paper, on the basis of systematical comparison of recent past literature, we conducted extensive works on the measurement of dielectric properties of VHB films, involving five influencing factors: prestretch (both equal and unequal biaxial), electrical frequency, electrode material, stress relaxation time and temperature. Experimental results directly show that the dielectric response changes according to these factors, based on which we investigate the significance of each factor, especially the interaction of two external conditions on the dielectric constant of deformable dielectric, by presenting a physical picture of the mechanism of polarization.

  4. Nonlinear Dynamical Model of a Soft Viscoelastic Dielectric Elastomer

    Science.gov (United States)

    Zhang, Junshi; Chen, Hualing; Li, Dichen

    2017-12-01

    Actuated by alternating stimulation, dielectric elastomers (DEs) show a behavior of complicated nonlinear vibration, implying a potential application as dynamic electromechanical actuators. As is well known, for a vibrational system, including the DE system, the dynamic properties are significantly affected by the geometrical sizes. In this article, a nonlinear dynamical model is deduced to investigate the geometrical effects on dynamic properties of viscoelastic DEs. The DEs with square and arbitrary rectangular geometries are considered, respectively. Besides, the effects of tensile forces on dynamic performances of rectangular DEs with comparably small and large geometrical sizes are explored. Phase paths and Poincaré maps are utilized to detect the periodicity of the nonlinear vibrations of DEs. The resonance characteristics of DEs incorporating geometrical effects are also investigated. The results indicate that the dynamic properties of DEs, including deformation response, vibrational periodicity, and resonance, are tuned when the geometrical sizes vary.

  5. Axion crystals

    Science.gov (United States)

    Ozaki, Sho; Yamamoto, Naoki

    2017-08-01

    The low-energy effective theories for gapped insulators are classified by three parameters: permittivity ɛ, permeability μ, and theta angle θ. Crystals with periodic ɛ are known as photonic crystals. We here study the band structure of photons in a new type of crystals with periodic θ (modulo 2 π) in space, which we call the axion crystals. We find that the axion crystals have a number of new properties that the usual photonic crystals do not possess, such as the helicity-dependent mass gap and nonrelativistic gapless dispersion relation at small momentum. We briefly discuss possible realizations of axion crystals in condensed matter systems and high-energy physics.

  6. [Obtaining ribosome crystals in homogenates].

    Science.gov (United States)

    Bersani, F; Longo, I; Fanti, M; Pettazzoni, P

    1979-08-30

    Chick embryos are homogenized in order to analyse ribosome crystallization. Ribosome crystallization has been induced by hypothermic treatment in chick embryos homogenate. Tetramers and crystals were produced by gradually inducing the temperature over a span of 10 h to 4 degrees C. It has been observed that the concentration of KCl in the buffer is a critical point. It is suggested that the nuclear fraction is engaged in ribosome crystallization.

  7. Synthesis of thermoplastic poly(ester-olefin elastomers

    Directory of Open Access Journals (Sweden)

    Tanasijević Branka

    2004-01-01

    Full Text Available A series of thermoplastic poly(ester-olefin elastomers, based on poly(ethylene-stat-butylene, HO-PEB-OH, as the soft segment and poly (butylene terephthalate, PBT, as the hard segment, were synthesized by a catalyzed transesterification reaction in solution. The incorporation of soft hydrogenated poly(butadiene segments into the copolyester backbone was accomplished by the polycondensation of α, ω-dihydroxyl telechelic HO-PEB-OH, (PEB Mn = 3092 g/mol with 1,4-butanediol (BD and dimethyl terephthalate (DMT in the presence of a 50 wt-% high boiling solvent i.e., 1,2,4-trichlorobenzene. The molar ratio of the starting comonomers was selected to result in a constant hard to soft weight ratio of 60:40. The synthesis was optimized in terms of both the concentration of catalyst, tetra-n-butyl-titanate (Ti(OBu4, and stabilizer, N,N'-diphenyl-p-phenylenediamine (DPPD, as well as the reaction time. It was found that the optimal catalyst concentration (Ti(OBu4 for the synthesis of these thermoplastic elastomers was 1.0 mmol/mol ester and the optimal DPPD concentration was 1.0 wt-%. The extent of the reaction was followed by measuring the inherent viscosity of the reaction mixture. The effectiveness of the incorporation of the soft segments into the copolymer chains was proved by Soxhlet extraction with chloroform. The molecular structures, composition and the size of the synthesized poly(ester-butylenes were verified by 1H NMR spectroscopy, viscometry of dilute solutions and the complex dynamic melt viscosity. The thermal properties of poly(ester-olefins were investigated by differential scanning calorimetry (DSC. The degree of crystallinity was also determined by DSC. The thermal and thermo-oxidative stability were investigated by thermogravimetric analysis (TGA. The rheological properties of poly(ester-olefins were investigated by dynamic mechanical spectroscopy in the melt and solid state.

  8. Synthesis and properties of butadiene-alpha-methylstyrene thermoplastic elastomer

    Directory of Open Access Journals (Sweden)

    A. V. Firsova

    2016-01-01

    Full Text Available Butadiene-α-methylstyrene block – copolymer – a thermoplastic elastomer (TPE-R DMST occupies a special place among the ethylene – vinyl aromatic block copolymers. TPE-R DMST comprising as plastic – poly-α-methylstyrene unit and elastic – polybutadiene block. TPE-R DMST has high heat resistance, flexibility, abrasion resistance compared to butadiene-styrene thermoplastic elastomer (TPE DST. The synthesis of block copolymers of butadiene and α-methylstyrene was carried out. The process of polymerization the α-methylstyrene characterized the high speed of polymerization in polar medium and low reaction speed in hydrocarbon solvents. Anionic catalyst nbutyllithium (n-BuLi and high concentration – 60–80% α-methylstyrene in the mixture influenced by synthesis of the 1st block of TPE-R DMST, it’s technologically difficult. Found that the low temperature of polymerization α-methylstyrene (+61 o C, the reversibility of these reactions and the high concentration of residual monomer are very importance. It was revealed that a high polymerization rate α-methylstyrene can be achieved by conducting the reaction in a hydrocarbon solvent with polar additives compounds such as tetrahydrofuran (THF and methyl tert-butyl ether (MTBE. The conditions for the synthesis of P-DMST were developed. The kinetics of polymerization for the first DMST-P unit was obtained. Analysis of physical and mechanical properties DMST-P samples was conducted. The optimum content of bound α-methylstyrene block copolymer provides a good combination of properties in a relatively wide temperature range. The tensile strength at normal and elevated temperatures, the hardness and the stiffness of the polymer increased by increasing the content of bound α-methylstyrene. The elongation and the elasticity reduced by increasing the content of bound α-methylstyrene.

  9. Toughening mechanism in elastomer-modified epoxy resins, part 2

    Science.gov (United States)

    Yee, A. F.; Pearson, R. A.

    1984-01-01

    The role of matrix ductility on the toughenability and toughening mechanism of elastomer-modified DGEBRA epoxies was investigated. Matrix ductility was varied by using epoxide resins of varying epoxide monomer molecular weights. These epoxide resins were cured using 4,4' diaminodiphenyl sulfone (DDS) and, in some cases, modified with 10% HYCAR(r)CTBN 1300X8. Fracture roughness values for the neat epoxies were found to be almost independent on the monomer molecular weight of the epoxide resin used. However, it was found that the fracture toughness of the elastomer-modified epoxies was very dependent upon the epoxide monomer molecular weight. Tensile dilatometry indicated that the toughening mechanism, when present, is similar to the mechanisms found for the piperidine cured epoxies in Part 1. SEM and OM corroborate this finding. Dynamic mechanical studies were conducted to shed light on the toughenability of the epoxies. The time-dependent small strain behavior of these epoxies were separated into their bulk and shear components. The bulk component is related to brittle fracture, whereas the shear component is related to yielding. It can be shown that the rates of shear and bulk strain energy buildup for a given stress are uniquely determined by the values of Poisson's ratio, nu. It was found that nu increases as the monomer molecular weight of the epoxide resin used increases. This increase in nu can be associated with the low temperature beta relaxation. The effect of increasing cross-link density is to shift the beta relaxation to higher temperatures and to decrease the magnitude of the beta relaxation. Thus, increasing cross-link density decreases nu and increases the tendency towards brittle fracture.

  10. Poly(butylene 2,5-furandicarboxylate-ε-caprolactone: A new bio-based elastomer with high strength and biodegradability

    Directory of Open Access Journals (Sweden)

    M. Y. Zheng

    2017-08-01

    Full Text Available A new bio-based elastomer, poly(butylene 2,5-furandicarboxylate-ε-caprolactone (PBFCL, has been synthesized from 2,5-furandicarboxylic acid, 1,4-butanediol, and ε-caprolactone successfully for the first time. The obtained copolyester was characterized in terms of chemical structure, thermal and mechanical properties, and enzymatic degradability. In PBFCL elastomer, butylene-2,5-furandiacrboxylate units (hard segments crystallize to serve as physical crosslinks while ε-caprolactone polyester diol (soft segments provide flexibility. PBFCL is a multi-blocked copolyester with randomly distributed rigid and soft segments. It possesses original feature of high strength and biodegradability stemming from the uses of aromatic and aliphatic monomers respectively. An important aspect of this new furanic-aliphatic polyester is its tailor-made properties simply achieved by changing the content of hard or soft segments. Typically, PBFCL-40 of optimal composition has Young’s modulus as low as 15.4 MPa, tensile strength as high 24.8 MPa, and elongation as long as 885%.

  11. Solid State NMR Investigations of Chain Dynamics and Network Order in Model Poly(dimethylsiloxane) Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J P; Mayer, B P; Wilson, T S; Chinn, S C; Maxwell, R S

    2010-12-09

    This work is at a relatively early stage, however it has been demonstrated that we can reliably probe basic network architectures using the MQ-NMR technique. The initial results are in good agreement with what is known from standard network theory and will serve as a basis for the study of progressively increasing structural complexity in Siloxane network systems.

  12. DuPont Dow Elastomers, Order Denying Petition for Objection to Permit

    Science.gov (United States)

    This document may be of assistance in applying the Title V air operating permit regulations. This document is part of the Title V Petition Database available at www2.epa.gov/title-v-operating-permits/title-v-petition-database. Some documents in the database are a scanned or retyped version of a paper photocopy of the original. Although we have taken considerable effort to quality assure the documents, some may contain typographical errors. Contact the office that issued the document if you need a copy of the original.

  13. Foam injection molding of thermoplastic elastomers: Blowing agents, foaming process and characterization of structural foams

    Science.gov (United States)

    Ries, S.; Spoerrer, A.; Altstaedt, V.

    2014-05-01

    Polymer foams play an important role caused by the steadily increasing demand to light weight design. In case of soft polymers, like thermoplastic elastomers (TPE), the haptic feeling of the surface is affected by the inner foam structure. Foam injection molding of TPEs leads to so called structural foam, consisting of two compact skin layers and a cellular core. The properties of soft structural foams like soft-touch, elastic and plastic behavior are affected by the resulting foam structure, e.g. thickness of the compact skins and the foam core or density. This inner structure can considerably be influenced by different processing parameters and the chosen blowing agent. This paper is focused on the selection and characterization of suitable blowing agents for foam injection molding of a TPE-blend. The aim was a high density reduction and a decent inner structure. Therefore DSC and TGA measurements were performed on different blowing agents to find out which one is appropriate for the used TPE. Moreover a new analyzing method for the description of processing characteristics by temperature dependent expansion measurements was developed. After choosing suitable blowing agents structural foams were molded with different types of blowing agents and combinations and with the breathing mold technology in order to get lower densities. The foam structure was analyzed to show the influence of the different blowing agents and combinations. Finally compression tests were performed to estimate the influence of the used blowing agent and the density reduction on the compression modulus.

  14. Design and thermal analysis of a mold used in the injection of elastomers

    Science.gov (United States)

    Fekiri, Nasser; Canto, Cécile; Madec, Yannick; Mousseau, Pierre; Plot, Christophe; Sarda, Alain

    2017-10-01

    In the process of injection molding of elastomers, improving the energy efficiency of the tools is a current challenge for industry in terms of energy consumption, productivity and product quality. In the rubber industry, 20% of the energy consumed by capital goods comes from heating processes; more than 50% of heat losses are linked to insufficient control and thermal insulation of Molds. The design of the tooling evolves in particular towards the reduction of the heated mass and the thermal insulation of the molds. In this paper, we present a complex tool composed, on one hand, of a multi-cavity mold designed by reducing the heated mass and equipped with independent control zones placed closest to each molding cavity and, on the other hand, of a regulated channel block (RCB) which makes it possible to limit the waste of rubber during the injection. The originality of this tool lies in thermally isolating the regulated channel block from the mold and the cavities between them in order to better control the temperature field in the material which is transformed. We present the design and the instrumentation of the experimental set-up. Experimental measurements allow us to understand the thermal of the tool and to show the thermal heterogeneities on the surface of the mold and in the various cavities. Tests of injection molding of the rubber and a thermal balance on the energy consumption of the tool are carried out.

  15. Development of a fatigue testing setup for dielectric elastomer membrane actuators

    Science.gov (United States)

    Hill, M.; Rizzello, G.; Seelecke, S.

    2017-04-01

    Dielectric elastomers (DE's) represent a transduction technology with high potential in many fields, including industries, due to their low weight, flexibility, and small energy consumption. For industrial applications, it is of fundamental importance to quantify the lifetime of DE technology, in terms of electrical and mechanical fatigue, when operating in realistic environmental conditions. This work contributes toward this direction, by presenting the development of an experimental setup which permits systematic fatigue testing of DE membranes. The setup permits to apply both mechanical and electrical stimuli to several membranes simultaneously, while measuring at the same time their mechanical (force, deformation) and electrical response (capacitance, resistance). In its final state, the setup will allow to test up to 15 DE membranes at the same time for several thousands of cycles. Control of the modules, monitoring of the actuators, and data acquisition are realized on a cRio FPGA-system running with LabVIEW. The setup is located in a climate chamber, in order to investigate the fatigue mechanisms at different environmental conditions, i.e., in terms of temperature and humidity. The setup consists of two main parts, namely a fatigue group and a measurement group. The fatigue group stays permanently in the climate chamber, while the measurement group is assembled to the fatigue group and allows to perform measurements at 20°C.

  16. Effects of Atomic Oxygen and Grease on Outgassing and Adhesion of Silicone Elastomers for Space Applications

    Science.gov (United States)

    deGroh, Henry C., III; Puleo, Bernadette J.; Steinetz, Bruce M.

    2012-01-01

    An investigation of silicone elastomers for seals used in docking and habitat systems for future space exploration vehicles is being conducted at NASA. For certain missions, NASA is considering androgynous docking systems where two vehicles each having a seal would be required to: dock for a period of time, seal effectively, and then separate with minimum push-off forces for undocking. Silicone materials are generally chosen for their wide operating temperatures and low leakage rates. However silicone materials are often sticky and usually exhibit considerable adhesion when mated against metals and silicone surfaces. This paper investigates the adhesion unit pressure for a space rated silicone material (S0383-70) for either seal-on-seal (SoS) or seal-on-aluminum (SoAl) operation modes in the following conditions: as-received, after ground-based atomic-oxygen (AO) pre-treatment, after application of a thin coating of a space-qualified grease (Braycote 601EF), and after a combination of AO pre-treatment and grease coating. In order of descending adhesion reduction, the AO treatment reduced seal adhesion the most, followed by the AO plus grease pre-treatment, followed by the grease treatment. The effects of various treatments on silicone (S0383-70 and ELA-SA-401) outgassing properties were also investigated. The leading adhesion AO pretreatment reduction led to a slight decrease in outgassing for the S0383-70 material and virtually no change in ELA-SA-401 outgassing.

  17. A mathematical model for an integrated self priming dielectric elastomer generator

    Science.gov (United States)

    Illenberger, Patrin K.; Wilson, Katherine E.; Henke, E.-F. Markus; Madawala, Udaya K.; Anderson, Iain A.

    2017-04-01

    Dielectric Elastomer Generators (DEG) can capture energy from natural movement sources such as wind, the tides and human locomotion. The harvested energy can be used for low power devices such as wireless sensor nodes and wearable electronics. A challenge for low power DEG is overcoming the losses associated with charge management. A circuit which can do this exists: the Self Priming Circuit (SPC) which consists of diodes and capacitors. The SPC is connected in parallel to the DEG where it transfers charge onto/o_ the DEG based on changes in the DEG capacitance. Modelling and experimental validation of the SPC have been performed in the past, allowing design and implementation of effective SPCs which match a particular DEG. While the SPC is effective, it is still an external circuit which adds additional mass and cost to the DEG. By splitting the DEG into separate capacitors and using them to build an SPC, the Integrated SPC (I-SPC) can be realized. This reduces the components required to build a SPC/DEG and improves the performance. This paper presents a mathematical model with experimental data of a first order I-SPC. Additionally, comparisons between the SPC and I-SPC are drawn.

  18. Improving Asphalt Mixture Performance by Partially Replacing Bitumen with Waste Motor Oil and Elastomer Modifiers

    Directory of Open Access Journals (Sweden)

    Sara Fernandes

    2017-08-01

    Full Text Available The environmental concern about waste generation and the gradual decrease of oil reserves has led the way to finding new waste materials that may partially replace the bitumens used in the road paving industry. Used motor oil from vehicles is a waste product that could answer that demand, but it can also drastically reduce the viscosity, increasing the asphalt mixture’s rutting potential. Therefore, polymer modification should be used in order to avoid compromising the required performance of asphalt mixtures when higher amounts of waste motor oil are used. Thus, this study was aimed at assessing the performance of an asphalt binder/mixture obtained by replacing part of a paving grade bitumen (35/50 with 10% waste motor oil and 5% styrene-butadiene-styrene (SBS as an elastomer modifier. A comparison was also made with the results of a previous study using a blend of bio-oil from fast pyrolysis and ground tire rubber modifier as a partial substitute for usual PG64-22 bitumen. The asphalt binders were tested by means of Fourier infrared spectra and dynamic shear rheology, namely by assessing their continuous high-performance grade. Later, the water sensitivity, fatigue cracking resistance, dynamic modulus and rut resistance performance of the resulting asphalt mixtures was evaluated. It was concluded that the new binder studied in this work improves the asphalt mixture’s performance, making it an excellent solution for paving works.

  19. Experimental Investigation on Mechanical Properties of Magnetorheological Elastomer with Circular Honeycomb Holes

    Directory of Open Access Journals (Sweden)

    Miao eYu

    2015-01-01

    Full Text Available In order to enhance adjustable mechanical properties of a specific magnetorheological elastomer (MRE, this study presents a new exterior structure of MRE by punching circular honeycomb holes on the MRE samples. Seven silicone rubber MRE samples with the same component are fabricated and then punched holes with different numbers and diameters. The influence of different porosities on the mechanical properties of MRE under various magnetic fields is experimentally investigated by using a rheometer with electromagnetic suite. It is shown from experimental investigation that the porosity of MRE samples has a significant impact on the performance of MRE; the shear storage modulus (MR effect and the loss factor is greatly increased. It is also observed that all the field-induced mechanical properties of the samples attain their respective maximum performance when the porosity increases to a critical value. The experimental results presented in this work directly indicate that high performances of the field-dependent mechanical and rheological properties can be achieved by means of external alternative structures such as honeycomb holes.

  20. Electromechanical conversion efficiency for dielectric elastomer generator in different energy harvesting cycles

    Directory of Open Access Journals (Sweden)

    Jian-Bo Cao

    2017-11-01

    Full Text Available In order to improve electromechanical conversion efficiency for dielectric elastomer generators (DEG, on the base of studying DEG energy harvesting cycles of constant voltage, constant charge and constant electric field intensity, a new combined cycle mode and optimization theory in terms of the generating mechanism and electromechanical coupling process have been built. By controlling the switching point to achieve the best energy conversion cycle, the energy loss in the energy conversion process is reduced. DEG generating test bench which was used to carry out comparative experiments has been established. Experimental results show that the collected energy in constant voltage cycle, constant charge cycle and constant electric field intensity energy harvesting cycle decreases in turn. Due to the factors such as internal resistance losses, electrical losses and so on, actual energy values are less than the theoretical values. The electric energy conversion efficiency by combining constant electric field intensity cycle with constant charge cycle is larger than that of constant electric field intensity cycle. The relevant conclusions provide a basis for the further applications of DEG.

  1. Lipid-induced degradation in biocompatible poly(Styrene-Isobutylene-Styrene) (SIBS) thermoplastic elastomer.

    Science.gov (United States)

    Fittipaldi, Mauro; Grace, Landon R

    2017-04-01

    The thermoplastic elastomer Poly(Styrene-block-Isobutylene-block-Styrene) (SIBS) is highly biocompatible, which has led to its use in several commercially-available implants. However, lipid-induced degradation has been previously identified as a primary cause of failure in long-term SIBS implants subject to mechanical loading. Thus, understanding the mechanisms and extent of lipid-induced damage and the role of styrene-isobutylene ratio and molecular weight is critical to improving longevity of SIBS-based implants in order to fully exploit the biocompatibility advantages. Samples of four different SIBS formulations were fabricated via compression molding, immersed to lipid saturation contents from 5 to 80% by weight, and tested in uniaxial tension, stress relaxation, and dynamic creep modes. Degradation mechanisms were investigated via infrared spectroscopy, chromatography, and microscopy. No evidence of lipid-induced chemical interactions or chain scissoring was observed. However, a decrease in tensile strength, loss of dynamic creep performance and faster relaxation with increasing lipid content is attributed to strong internal straining. The magnitude of these losses is inversely proportional to both molecular weight and styrene content, suggesting that selection of these variables during the design phase should be based not only on the mechanical requirements of the application, but the expected degree of lipid exposure. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Electromechanical conversion efficiency for dielectric elastomer generator in different energy harvesting cycles

    Science.gov (United States)

    Cao, Jian-Bo; E, Shi-Ju; Guo, Zhuang; Gao, Zhao; Luo, Han-Pin

    2017-11-01

    In order to improve electromechanical conversion efficiency for dielectric elastomer generators (DEG), on the base of studying DEG energy harvesting cycles of constant voltage, constant charge and constant electric field intensity, a new combined cycle mode and optimization theory in terms of the generating mechanism and electromechanical coupling process have been built. By controlling the switching point to achieve the best energy conversion cycle, the energy loss in the energy conversion process is reduced. DEG generating test bench which was used to carry out comparative experiments has been established. Experimental results show that the collected energy in constant voltage cycle, constant charge cycle and constant electric field intensity energy harvesting cycle decreases in turn. Due to the factors such as internal resistance losses, electrical losses and so on, actual energy values are less than the theoretical values. The electric energy conversion efficiency by combining constant electric field intensity cycle with constant charge cycle is larger than that of constant electric field intensity cycle. The relevant conclusions provide a basis for the further applications of DEG.

  3. Semiactive Vibration Control Using a Magnetorheological Damper and a Magnetorheological Elastomer Based on the Bouc-Wen Model

    Directory of Open Access Journals (Sweden)

    Wei Zhu

    2014-01-01

    Full Text Available A vibration control system is put forward using a magnetorheological damper (MRD and a magnetorheological elastomer (MRE connected in series. In order to model the hysteresis of the MRD, a Bouc-Wen model and a corresponding parameter identification method are developed for the MRD. The experimental results validate the proposed Bouc-Wen model that can predict the hysteretic behavior of the MRD accurately. The role of the MRE is illustrated by an example of a single degree-of-freedom system. A semiactive vibration control strategy of the proposed vibration control system is proposed. To validate this new approach, experiments are conducted and the results highlight significantly improved vibration reduction effect of the proposed vibration control system than the vibration control system only using the MRD.

  4. Crystal defects and cation ordering domains in epitaxial PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} relaxor ferroelectric thin films investigated by high-resolution transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Birajdar, B.I., E-mail: balaji.birajdar@ww.uni-erlangen.de [Max Planck Institute of Microstructure Physics, D-06120 Halle (Germany); Chopra, A.; Alexe, M.; Hesse, D. [Max Planck Institute of Microstructure Physics, D-06120 Halle (Germany)

    2011-06-15

    Highlights: > Epitaxial thin films of PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} grown by pulsed laser deposition. > Microstructure studied by transmission electron microscopy. > Microstructural defects: {pi} stacking faults and cation ordering domains. > Explanation for the formation of defects. > Explanation of reduced dielectric constant of relaxor thin films. - Abstract: Epitaxial thin films of the relaxor ferroelectric PbSc{sub 0.5}Ta{sub 0.5}O{sub 3} (PST) were grown by pulsed laser deposition on an SrTiO{sub 3} substrate with an SrRuO{sub 3} buffer layer and investigated by diffraction contrast imaging and high-resolution transmission electron microscopy (TEM) in cross-section and plan-view. Crystal defects, viz. misfit dislocations, {pi} stacking faults and cation ordering domains, have been characterized and the mechanism of their formation is discussed. The state of the structural disorder in PST relaxor thin films is characterized by the high density of {pi} stacking faults and the rather small size (<10 nm) of the cation ordering domains, and is therefore markedly distinct from the state of the disorder in bulk relaxor PST. Polar nanoregions, supposed to be essential for explaining the relaxor properties, could not be detected using TEM, possibly due to their high fluctuation frequency. The dielectric constant of the relaxor PST thin films is about an order of magnitude smaller than that of bulk relaxor PST, which is attributed to the large density of {pi} stacking faults in the thin films.

  5. Color stability and colorant effect on maxillofacial elastomers. Part III: weathering effect on color.

    Science.gov (United States)

    Haug, S P; Andres, C J; Moore, B K

    1999-04-01

    Maxillofacial prostheses are serviceable for approximately 6 months, after which they need to be refabricated because of the deterioration of color and physical properties. This third article in a 3-part series evaluated the color stability of commonly used colorant-elastomer combinations as a result of exposure to weathering. Fifteen specimens were fabricated for each of the 3 elastomers (Silastic medical adhesive type A, Silastic 4-4210, and Silicone A-2186) and 6 colorants (dry earth pigments, rayon fiber flocking, artist's oil paints, kaolin, liquid cosmetics, and no colorant) for a total of 270 specimens (18 groups of 15 specimens). The 15 specimens of each elastomer-colorant combination were separated into 3 test condition groups (control, time passage, and natural weathering) of 5 specimens per test condition group. Control specimens were evaluated within 1 month of fabrication. The time passage group was sealed in glass containers and kept in the dark for 6 months before testing. The natural weathering groups were placed on the roof of the dental school for 6 months and exposed to sunlight and weathering. Color and optical density data for each elastomer-colorant combination were subjected to a 1-way analysis of variance to examine effects among test conditions (control, time passage, and weathering). When significant differences were observed, the Student-Newman-Keuls multiple range test was performed to identify differences in elastomer-colorant combinations among each test condition at a significance level of .05. Changes in color, as a result of weathering, were noted in many of the colorant-elastomer combinations. Also, color change occurred not only to the colored, but also to uncolored materials over time without exposure to weathering. Clinically, the addition of colorants could have a stabilizing effect on the elastomer color when it is exposed to weathering.

  6. Epoxy elastomers reinforced with functionalized multi-walled carbon nanotubes as stimuli-responsive shape memory materials

    Energy Technology Data Exchange (ETDEWEB)

    Lama, G. C.; Nasti, G.; Cerruti, P.; Gentile, G.; Carfagna, C. [Institute of Polymer Chemistry and Technology (ICTP-CNR), via Campi Flegrei 34, 80078 Pozzuoli (Italy); Ambrogi, V. [Department of Chemical, Materials and Production Engineering - University of Naples Federico II, Piazzale Tecchio 80, 80125 Napoli (Italy)

    2014-05-15

    In this work, the incorporation of multiwalled carbon nanotubes (MWCNT) into epoxy-based elastomers was carried out in order to obtain nanocomposite systems with shape memory effect. For the preparation of elastomeric matrices, p-bis(2,3-epoxypropoxy)-α-methylstilbene (DOMS) was cured with sebacic acid. DOMS was synthesized in our laboratory and it is characterized by a rigid-rod, potentially liquid crystalline structure. A lightly cross-linked liquid crystalline elastomer was obtained. As for nanocomposites, variable amounts (0.75, 1.50, 3.0, 6.0, 12.0 wt.%) of COOH-MWCNTs were employed. In order to improve the nanotubes dispersibility and the interfacial adhesion with the epoxy matrix, an optimized two-step procedure was developed, which consisted in grafting the epoxy monomer onto the nanotube surface and then curing it in presence of crosslinking agent. DOMS-functionalized MWCNT were characterized through solvent dispersion experiments, FTIR spectroscopy and TGA analysis, which demonstrated the occurred covalent functionalization of the nanotubes with the epoxy monomers. The morphological analysis through electron microscopy demonstrated that this was an efficient strategy to improve the dispersion of nanotubes within the matrix. The second part of the work was devoted to the structural, thermal, mechanical and electric characterization of elastomeric nanocomposites. The results indicated a general improvement of properties of nanocomposites. Also, independently of the nanotube content, a smectic phase formed. Shape memory features of LC systems were also evaluated. It was demonstrated the shape could be recovered through heating, solvent immersion, as well as upon the application of an electrical field.

  7. Optically Anomalous Crystals

    CERN Document Server

    Shtukenberg, Alexander; Kahr, Bart

    2007-01-01

    Optical anomalies in crystals are puzzles that collectively constituted the greatest unsolved problems in crystallography in the 19th Century. The most common anomaly is a discrepancy between a crystal’s symmetry as determined by its shape or by X-ray analysis, and that determined by monitoring the polarization state of traversing light. These discrepancies were perceived as a great impediment to the development of the sciences of crystals on the basis of Curie’s Symmetry Principle, the grand organizing idea in the physical sciences to emerge in the latter half of the 19th Century. Optically Anomalous Crystals begins with an historical introduction covering the contributions of Brewster, Biot, Mallard, Brauns, Tamman, and many other distinguished crystallographers. From this follows a tutorial in crystal optics. Further chapters discuss the two main mechanisms of optical dissymmetry: 1. the piezo-optic effect, and 2. the kinetic ordering of atoms. The text then tackles complex, inhomogeneous crystals, and...

  8. Nuclear order in copper

    DEFF Research Database (Denmark)

    Annila, A.J.; Clausen, K.N.; Lindgård, P-A.

    1990-01-01

    A new ordering vector k=(2π/a)(0, 2/3, 2/3) for fcc antiferromagnets has been found by neutron-diffraction experiments at nanokelvin temperatures in the nuclear-spin system of a 65Cu single crystal. The corresponding reflection together with the previously observed (100) Bragg peak show the prese......A new ordering vector k=(2π/a)(0, 2/3, 2/3) for fcc antiferromagnets has been found by neutron-diffraction experiments at nanokelvin temperatures in the nuclear-spin system of a 65Cu single crystal. The corresponding reflection together with the previously observed (100) Bragg peak show...

  9. Dopamine-Incorporated Dual Bioactive Electroactive Shape Memory Polyurethane Elastomers with Physiological Shape Recovery Temperature, High Stretchability, and Enhanced C2C12 Myogenic Differentiation.

    Science.gov (United States)

    Zhao, Xin; Dong, Ruonan; Guo, Baolin; Ma, Peter X

    2017-09-06

    Soft tissue engineering needs elastic biomaterials not only mimicking the elasticity of soft tissue but also possessing multiple bioactivity to promote cell adhesion, proliferation, and differentiation, which still remain ongoing challenges. Herein, we synthesized a series of dopamine-incorporated dual bioactive electroactive shape memory polyurethane elastomers by combining the properties of elastomeric poly(citric acid-co-polycaprolactone) (CA-PCL) polyurethane elastomer, bioactive dopamine (DA), and electroactive aniline hexamer (AH). The chemical structures, electroactivity, conductivity, thermal properties, hydrophilicity and hydration ability, mechanical properties, and degradability of the polyurethane elastomers were systematically characterized. The elastomers showed excellent shape fixity ratio and shape recovery ability under physiological conditions. The elastomers' elongation and stress were tailored by the AH content, whereas the hydrophilicity and hydration ability of the elastomers were adjusted by the content of DA and AH, as well as the doping state of AH. The viability and proliferation results of C2C12 cells seeded on the elastomers showed their excellent cytocompatibility. Additionally, by analyzing the protein and gene level, the promotion effect on myogenic differentiation of C2C12 cells by these elastomers compared to that by control groups (PCL80 000, CA-PCL elastomer, and CA-PCL elastomer with the DA segment) was demonstrated. Furthermore, the results from subcutaneous implantation confirmed the elastomers' mild host response in vivo. These results represent that these dopamine-incorporated dual bioactive electroactive shape memory polyurethane elastomers are promising candidates for soft tissue regeneration that is sensitive to electrical signals.

  10. Mechanical and optical effects of elastomer interaction in polypropylene modification: Ethylene-propylene rubber, poly-(ethylene-co-octene and styrene-butadiene elastomers

    Directory of Open Access Journals (Sweden)

    M. Gahleitner

    2012-09-01

    Full Text Available The interaction between binary combinations of three different elastomer classes commonly applied in impact modification of isotactic polypropylene (iPP was studied. Blends based on a homogeneous ethylene-propylene (EP random copolymer (EP-RACO and a heterophasic EP impact copolymer comprising ethylene-propylene rubber (EPR with different external elastomer types, one homogeneous ethylene-1-octene copolymer (EOC, and two hydrogenated styrenebutadiene-styrene triblock copolymers (SEBS with different styrene content, were prepared. The phase morphology, mobility as a function of temperature, mechanical and optical properties were studied. Special effects could be achieved for the combination of two different elastomer types. The results clearly demonstrate the possibility to achieve attractive property combinations in ternary systems consisting of a crystalline PP matrix and two different types of elastomer, EPR or EOC on the one hand and SEBS on the other hand. A combination of density matching and compatibilization effects allows reaching good low temperature impact strength together with a transparency close to matrix level when selecting a butadiene-rich SEBS type.

  11. Mechanical and Electrical Ageing Effects on the Long-Term Stretching of Silicone Dielectric Elastomers with Soft Fillers

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin; Yu, Liyun

    2016-01-01

    Dielectric elastomer materials for actuators need to be soft and stretchable while possessing high dielectric permittivity. Soft silicone elastomers can be obtained through the use of silicone oils, while enhanced permittivity can be obtained through the use of dipolar groups on the polymer...

  12. Aging Behavior and Performance Projections for a Polysulfide Elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Celina, Mathias C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Giron, Nicholas Henry [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Quintana, Adam [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-05-01

    The accelerated aging behavior and aging state of a 30 year old field retrieved polysulfide elastomer was examined. The material is used as an environmental thread sealant for a stainless steel bolt in a steel threaded insert in an aluminum assembly. It is a two component curable polysulfide elastomer that is commercially available in a similar formulation as was applied 30 years ago. The primary goal of this study was to establish if aging over 30 years under moderate aging conditions (mostly ambient temperature and humidity) resulted in significant property changes, or if accelerated aging could identify developing aging pathways which would prevent the extended use of this material. The aging behavior of this material was examined in three ways: A traditional accelerated thermo-oxidative aging study between 95 to 140°C which focused on physical and chemical properties changes, an evaluation of the underlying oxidation rates between RT and 125°C, and an assessment of the aging state of a small 30 year old sample. All three data sets were used to establish aging characteristics, their time evolution, and to extrapolate the observed behavior to predict performance limits at RT. The accelerated aging study revealed a relatively high average activation energy of ~130 kJ/mol which gives overconfident performance predictions. Oxidation rates showed a decreasing behavior with aging time and a lower E a of ~84 kJ/mol from time - temperature superposition , but also predicted sufficient additional performance at RT. Consistent with these projections for extended RT performance, only small changes were observed for the 30 year old material. Extrapolations using this partially aged material also predict ongoing use as a viable option. Unexpected RT degradation could only develop into a concern should the oxidation rate not trend lower over time as was observed at elevated temperature. Considering all data acquired in this limited aging study , there are no immediately

  13. The Mechanical Performance of Subscale Candidate Elastomer Docking Seals

    Science.gov (United States)

    Bastrzyk, Marta B.; Daniels, Christopher C.

    2010-01-01

    The National Aeronautics and Space Administration is developing a Low Impact Docking System (LIDS) for future exploration missions. The mechanism is a new state-of-the-art device for in-space assembly of structures and rendezvous of vehicles. At the interface between two pressurized modules, each with a version of the LIDS attached, a composite elastomer-metal seal assembly prevents the breathable air from escaping into the vacuum of space. Attached to the active LIDS, this seal mates against the passive LIDS during docking operation. The main interface seal assembly must exhibit low leak and outgas values, must be able to withstand various harsh space environments, must remain operational over a range of temperatures from -50 C to 75 C, and perform after numerous docking cycles. This paper presents results from a comprehensive study of the mechanical performance of four candidate subscale seal assembly designs at -50, 23, 50, and 75 C test temperatures. In particular, the force required to fully compress the seal during docking, and that which is required for separation during the undocking operation were measured. The height of subscale main interface seal bulbs, as well as the test temperature, were shown to have a significant effect on the forces the main interface seal of the LIDS may experience during docking and undocking operations. The average force values required to fully compress each of the seal assemblies were shown to increase with test temperature by approximately 50% from -50 to 75 C. Also, the required compression forces were shown to increase as the height of the seal bulb was increased. The seal design with the tallest elastomer seal bulb, which was 31% taller than that with the shortest bulb, required force values approximately 45% higher than those for the shortest bulb, independent of the test temperature. The force required to separate the seal was shown to increase with decreasing temperature after 15 hours of simulated docking. No adhesion

  14. Enhanced electromechanical performance of bio-based gelatin/glycerin dielectric elastomer by cellulose nanocrystals.

    Science.gov (United States)

    Ning, Nanying; Wang, Zhifei; Yao, Yang; Zhang, Liqun; Tian, Ming

    2015-10-05

    To meet the growing demand of environmental protection and resource saving, it is imperative to explore bio-based elastomers as next-generation dielectric elastomers (DEs). In this study, we used a bio-based gelatin/glycerin (GG) elastomer as the DE matrix because GG exhibits high dielectric constant (ɛr). Cellulose nanocrystals (CNCs), extracted from natural cellulose fibers, were used to improve the mechanical strength of GG elastomer. The results showed that CNCs with a large number of hydroxyl groups disrupted the hydrogen bonds between gelatin molecules and formed new stronger hydrogen bonds with gelatin molecules. A good interfacial adhesion between CNCs and GG was formed, and thus a good dispersion of CNCs in GG matrix was obtained, leading to the improved mechanical strength of GG. More interestingly, the ɛr of GG elastomer was obviously increased by adding 5 wt% of CNCs, ascribed to the increase in the polarizability of gelatin chains caused by the disruption of hydrogen bonds of gelatin. As a result, a 230% increase in the actuated strain at low electric field of GG was obtained by adding 5 wt% of CNCs. Since CNCs, gelatin and glycerol are all bio-based, this study offers a new method to prepare high performance DE for its application in biological and medical fields. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Semi-active control of a sandwich beam partially filled with magnetorheological elastomer

    Science.gov (United States)

    Dyniewicz, Bartłomiej; Bajkowski, Jacek M.; Bajer, Czesław I.

    2015-08-01

    The paper deals with the semi-active control of vibrations of structural elements. Elastomer composites with ferromagnetic particles that act as magnetorheological fluids are used. The damping coefficient and the shear modulus of the elastomer increases when it is exposed to an electro-magnetic field. The control of this process in time allows us to reduce vibrations more effectively than if the elastomer is permanently exposed to a magnetic field. First the analytical solution for the vibrations of a sandwich beam filled with an elastomer is given. Then the control problem is defined and applied to the analytical formula. The numerical solution of the minimization problem results in a periodic, perfectly rectangular control function if free vibrations are considered. Such a temporarily acting magnetic field is more efficient than a constantly acting one. The surplus reaches 20-50% or more, depending on the filling ratio of the elastomer. The resulting control was verified experimentally in the vibrations of a cantilever sandwich beam. The proposed semi-active control can be directly applied to engineering vibrating structural elements, for example helicopter rotors, aircraft wings, pads under machines, and vehicles.

  16. Study on the control of the compositions and properties of a biodegradable polyester elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Liu Quanyong; Weng Jingyi; Zhang Liqun [Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China); Tan Tianwei, E-mail: liu_quanyong@126.co, E-mail: zhanglq@mail.buct.edu.c [Key Laboratory of Bioprocess of Beijing, Beijing University of Chemical Technology, Beijing 100029 (China)

    2009-04-15

    Biodegradable polyester elastomers are widely reported to be applied in varied biomedical fields. In this paper, we attempt to investigate how both the thermal-curing time and molar ratio of the monomers affect the final compositions and properties of the novel poly(glycerol-sebacate-citrate) (PGSC) elastomers. First, PGSC elastomers are obtained after the thermal curing of the moldable mixtures consisting of citric acid and poly(glycerol-sebacate) (PGS) prepolymers synthesized in the lab. Then further studies show that, on the one hand, the control of longer thermal-curing time results in elastomers with less sol, lower swelling degree, slower degradation, greater mechanical strength and higher glass transition temperature and, on the other hand, the crosslink with more citric acid is advantageous to greatly improving their mechanical strength and glass transition temperatures, simultaneously decreasing their sol contents, swelling degrees and degradation rates. The PGSC elastomers show thermosetting properties, certain strength, mass losses lower than 20% after 4-week degradation and durative water absorption during degradation. Thus they might be potentially used as degradable bio-coatings, varied soft biomedical membranes and drug delivery matrices.

  17. A Transparent, Highly Stretchable, Autonomous Self-Healing Poly(dimethyl siloxane) Elastomer.

    Science.gov (United States)

    Zhang, Baolin; Zhang, Ping; Zhang, Hanzhi; Yan, Casey; Zheng, Zijian; Wu, Biao; Yu, You

    2017-08-01

    An innovative self-healing polydimethylsiloxane (PDMS) elastomer, namely, PDMS-TFB, is reported by incorporating the reversibly dynamic imine bond as the self-healing points into the PDMS networks. The PDMS-TFB elastomer features good optical transmittance (80%) in full visible light region, high stretchability (≈700%), and excellent autonomous self-healing ability at room temperature. Surprisingly, the self-healing behavior can take place in water and even at a temperature as low as -20 °C in air, showing a promising outlook for broader applications. As a proof-of-concept, this study demonstrates the use of the PDMS-TFB elastomer for preparing anticorrosion coating and adhesive layer, and also the use of such an elastomer to be the platform for fabricating the flexible interconnector and chemical sensor. Remarkably, no significant difference is observed between the pristine and healed samples. Taking full advantage of these unique properties, it is anticipated that such a PDMS-TFB elastomer shows wide applications in the fields of materials science, electronics, biology, optics, etc. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Parameters design of the dielectric elastomer spring-roll bending actuator (Conference Presentation)

    Science.gov (United States)

    Li, Jinrong; Liu, Liwu; Liu, Yanju; Leng, Jinsong

    2017-04-01

    Dielectric elastomers are novel soft smart material that could deform sustainably when subjected to external electric field. That makes dielectric elastomers promising materials for actuators. In this paper, a spring-roll actuator that would bend when a high voltage is applied was fabricated based on dielectric elastomer. Using such actuators as active parts, the flexible grippers and inchworm-inspired crawling robots were manufactured, which demonstrated some examples of applications in soft robotics. To guide the parameters design of dielectric elastomer based spring-roll bending actuators, the theoretical model of such actuators was established based on thermodynamic theories. The initial deformation and electrical induced bending angle of actuators were formulated. The failure of actuators was also analyzed considering some typical failure modes like electromechanical instability, electrical breakdown, loss of tension and maximum tolerant stretch. Thus the allowable region of actuators was determined. Then the bending angle-voltage relations and failure voltages of actuators with different parameters, including stretches of the dielectric elastomer film, number of active layers, and dimensions of spring, were investigated. The influences of each parameter on the actuator performances were discussed, providing meaningful guidance to the optical design of the spring-roll bending actuators.

  19. Crystal rainbows

    Energy Technology Data Exchange (ETDEWEB)

    Neskovic, N. E-mail: nnesko@vin.bg.ac.yu; Petrovic, S

    2003-06-01

    This review is devoted to ion transmission through axial channels of thin crystals. In this process the rainbows occur. The effect is called the crystal rainbow effect. We shall describe its origin and present the experiments in which it has been observed. We shall explain also how the crystal rainbows can be classified using catastrophe theory. This classification has resulted in a universal, simple and accurate approximation to the continuum potential in the channels. Besides, the periodicity of the angular distributions of transmitted ions with the reduced crystal thickness will be considered. It will be introduced via the effect of zero-degree focusing of channeled ions. In addition, we shall mention the doughnut effect in ion channeling, which has proven to be the rainbow effect with tilted crystals. All these considerations will demonstrate clearly the usefulness of the theory of crystal rainbows, which is the proper theory of ion channeling in thin crystals00.

  20. Dielectric elastomer actuators for octopus inspired suction cups.

    Science.gov (United States)

    Follador, M; Tramacere, F; Mazzolai, B

    2014-09-25

    Suction cups are often found in nature as attachment strategy in water. Nevertheless, the application of the artificial counterpart is limited by the dimension of the actuators and their usability in wet conditions. A novel design for the development of a suction cup inspired by octopus suckers is presented. The main focus of this research was on the modelling and characterization of the actuation unit, and a first prototype of the suction cup was realized as a proof of concept. The actuation of the suction cup is based on dielectric elastomer actuators. The presented device works in a wet environment, has an integrated actuation system, and is soft. The dimensions of the artificial suction cups are comparable to proximal octopus suckers, and the attachment mechanism is similar to the biological counterpart. The design approach proposed for the actuator allows the definition of the parameters for its development and for obtaining a desired pressure in water. The fabricated actuator is able to produce up to 6 kPa of pressure in water, reaching the maximum pressure in less than 300 ms.