Sample records for black pdms structures

  1. A new approach to fabricate pdms structures using femtosecond laser (United States)

    Selvaraj, Hamsapriya

    Polydimethylsiloxane (PDMS) is commonly used to prototype micro and nano featured components due to its beneficial properties. PDMS based devices have been used for diverse applications such as cell culturing, cell sorting and sensors. Motivated by such diverse applications possible through pure PDMS and reinforced PDMS, numerous efforts have been directed towards developing novel fabrication techniques. Prototyping 2D and 3D pure and reinforced PDMS microdevices normally require a long curing time and must go through multiple steps. This research explores the possibility of fabricating microscale and nanoscale structures directly from PDMS resin using femtosecond laser processing. This study offers an alternative fabrication route that potentially lead to a new way for prototyping of pure and reinforced PDMS devices, and the generation of hybrid nanomaterials. In depth investigation of femtosecond laser irradiation of PDMS resin reveals that the process is highly intensity-dependent. At low to intermediate intensity regime, femtosecond laser beam is able to rapidly cure the resin and create micron-sized structures directly from PDMS resin. At higher intensity regime, a total break-down of the resin material occurs and leads to the formation of PDMS nanoparticles. This work demonstrates a new way of rapid curing of PDMS resin on a microsecond timescale using femtosecond laser irradiation. The proposed technique permits maskless singlestep curing and is capable of fabricating 2D and 3D structures in micro-scale. Reinforced PDMS microstructures also have been fabricated through this method. The proposed technique permits both reinforcement and rapid curing and is ideal for fabricating reinforced structures in microscale. The strength of the nanofiber reinforced PDMS microstructures has been investigated by means of Nanoindentation test. The results showed significant improvement in strength of the material. Hybrid PDMS-Si and hybrid PDMS-Al nanoparticle aggregate

  2. Accounting for PDMS shrinkage when replicating structures

    DEFF Research Database (Denmark)

    Madsen, Morten Hannibal; Feidenhans'l, Nikolaj Agentoft; Hansen, Poul-Erik


    are seldom applied to counteract the shrinkage of PDMS. Also, to perform metrological measurements using replica techniques one has to take the shrinkage into account. Thus we report a study of the shrinkage of PDMS with several different mixing ratios and curing temperatures. The shrinkage factor, with its...

  3. How does the molecular network structure influence PDMS elastomer wettability? (United States)

    Melillo, Matthew; Genzer, Jan

    Poly(dimethylsiloxane) (PDMS) is one of the most common elastomers, with applications ranging from medical devices to absorbents for water treatment. Fundamental understanding of how liquids spread on the surface of and absorb into PDMS networks is of critical importance for the design and use of another application - microfluidic devices. We have systematically studied the effects of polymer molecular weight, loading of tetra-functional crosslinker, end-group chemical functionality, and the extent of dilution of the curing mixture on the mechanical and surface properties of end-linked PDMS networks. The gel and sol fractions, storage and loss moduli, liquid swelling ratios, and water contact angles have all been shown to vary greatly based on the aforementioned variables. Similar trends were observed for the commercial PDMS material, Sylgard-184. Our results have confirmed theories predicting the relationships between modulus and swelling. Furthermore, we have provided new evidence for the strong influence that substrate modulus and molecular network structure have on the wettability of PDMS elastomers. These findings will aid in the design and implementation of efficient microfluidics and other PDMS-based materials that involve the transport of liquids.

  4. Micro-structured PDMS piezoelectric enhancement through charging conditions (United States)

    Kachroudi, Achraf; Basrour, Skandar; Rufer, Libor; Sylvestre, Alain; Jomni, Fathi


    Micro-structured cellular polydimethylsiloxane (PDMS) materials were prepared by a low-cost molding process allowing us to control geometry and sample size. Cellular structures are charged with a triangular quasi-static voltage with amplitudes between 1 kV and 4 kV and a frequency of 0.5 Hz fixed after having evaluated the conditions enhancing the piezoelectric response of the cellular PDMS. The piezo-electret PDMS material charged at room temperature has a piezoelectric coefficient d 33 of 350 pC/N, which is ten times larger than that of polyvinylidene fluoride. The high piezoelectric coefficient with a very low elastic modulus of 300 kPa makes these materials very useful for wearable device applications. The piezoelectric coefficient d 33 of the samples poled at high temperatures improves thermal stability but reduces PDMS piezo-electret piezoelectricity, which is explained by the structure’s stiffness. These results are useful and allow us to set the conditions for the preparation of the piezo-electret materials according to desired applications.

  5. Structured PDMS Chambers for Enhanced Human Neuronal Cell Activity on MEA Platforms

    Institute of Scientific and Technical Information of China (English)

    Joose Kreutzer; Laura Yl(a)-Outinen; Paula K(a)irn(a); Tiina Kaarela; Jarno Mikkonen; Heli Skottman; Susanna Narkilahti; Pasi Kallio


    Structured poly(dimethylsiloxane) (PDMS) chambers were designed and fabricated to enhance the signaling of human Embryonic Stem Cell (hESC) - derived neuronal networks on Microelectrode Array (MEA) platforms.The structured PDMS chambers enable cell seeding on restricted areas and thus,reduce the amount of needed coating materials and cells.In addition,the neuronal cells formed spontaneously active networks faster in the structured PDMS chambers than that in control chainbers.In the PDMS chambers,the neuronal networks were more active and able to develop their signaling into organized signal trains faster than control cultures.The PDMS chamber design enables much more repeatable analysis and rapid growth of functional neuronal network in vitro.Moreover,due to its easy and cheap fabrication process,new configurations can be easily fabricated based on investigator requirements.

  6. Microfluidic free-flow zone electrophoresis and isotachophoresis using carbon black nano-composite PDMS sidewall membranes. (United States)

    Fu, Xiaotong; Mavrogiannis, Nicholas; Ibo, Markela; Crivellari, Francesca; Gagnon, Zachary R


    We present a new type of free-flow electrophoresis (FFE) device for performing on-chip microfluidic isotachophoresis and zone electrophoresis. FFE is performed using metal gallium electrodes, which are isolated from a main microfluidic flow channel using thin micron-scale polydimethylsiloxane/carbon black (PDMS/CB) composite membranes integrated directly into the sidewalls of the microfluidic channel. The thin membrane allows for field penetration and effective electrophoresis, but serves to prevent bubble generation at the electrodes from electrolysis. We experimentally demonstrate the ability to use this platform to perform on-chip free-flow electrophoretic separation and isotachophoretic concentration. Due to the small size and simple fabrication procedure, this PDMS/CB platform could be used as a part of an on-chip upstream sample preparation toolkit for portable microfluidic diagnostic applications.

  7. Preparation, characterization, and silanization of 3D microporous PDMS structure with properly sized pores for endothelial cell culture. (United States)

    Zargar, Reyhaneh; Nourmohammadi, Jhamak; Amoabediny, Ghassem


    Nowadays, application of porous polydimethylsiloxane (PDMS) structure in biomedical is becoming widespread, and many methods have been established to create such structure. Although the pores created through these methods are mostly developed on the outer surface of PDMS membrane, this study offers a simple and cost-efficient technique for creating three-dimensional (3D) microporous PDMS structure with appropriate pore size for endothelial cell culture. In this study, combination of gas foaming and particulate leaching methods, with NaHCO3 as effervescent salt and NaCl as progen are used to form a 3D PDMS sponge. The in situ chemical reaction between NaHCO3 and HCl resulted in the formation of small pores and channels. Moreover, soaking the samples in HCl solution temporarily improved the hydrophilicity of PDMS, which then facilitated the penetration of water for further leaching of NaCl. The surface chemical modification process was performed by (3-aminopropyl)triethoxysilane to culture endothelial cells on porous PDMS matrix. The results are an indication of positive response of endothelial cells to the fabricated PDMS sponge. Because of simplicity and practicality of this method for preparing PDMS sponge with appropriate pore size and biological properties, the fabricated matrix can perfectly be applied to future studies in blood-contacting devices.

  8. The Mechanical Aspects of Formation and Application of PDMS Bilayers Rolled into a Cylindrical Structure

    Directory of Open Access Journals (Sweden)

    Dongwon Kang


    Full Text Available A polydimethylsiloxane (PDMS film with its surface being oxidized by a plasma treatment or a UV-ozone (UVO treatment, that is, a bilayer made of PDMS and its oxidized surface layer, is known to roll into a cylindrical structure upon exposure to the chloroform vapor due to the mismatch in the swelling ratio between PDMS and the oxidized layer by the chloroform vapor. Here we analyzed the formation of the rolled bilayer with the mechanical aspects: how the mismatch in the swelling ratio of the bilayer induces rolling of the bilayer, why any form of trigger that breaks the symmetry in the in-plane stress level is needed to roll the bilayer uniaxially, why the rolled bilayer does not unroll in the dry state when there is no more mismatch in the swelling ratio, and how the measured curvature of rolled bilayer matches well with the prediction by the theory. Moreover, for the use of the rolled bilayer as the channel of the microfluidic device, we examined whether the rolled bilayer deforms or unrolls by the flow of the aqueous solution that exerts the circumferential stress on the rolled bilayer.

  9. TECHNICAL NOTE: Spun-cast micromolding for etchless micropatterning of electrically functional PDMS structures (United States)

    McClain, Maxine A.; La Placa, Michelle C.; Allen, Mark G.


    Polydimethylsiloxane (PDMS) is widely used in bioMEMS applications; however, patterning of this material to form complex structures is often challenging. Chemical etches are typically ineffective due to the inertness of the material. Plasma processing of bulk material can be time intensive and presents concerns regarding the mechanical properties of the post-etched polymer due to etch-induced cross-linking of surrounding material. Presented in this paper, the etchless process of spun-cast micromolding (SCμM) is used to create an array of patterned, PDMS, electrical microcables. The microcables are arranged in a net-like array and incorporate electrical functionality. The geometries fabricated with these techniques include straight and sinusoidal microcables. In addition to the cables themselves, specific regions of the cables' top insulating layer can also be patterned using a hierarchical application of the SCμM process, creating exposed electrical access sites useful as electrical access points for electrophysiological applications. The SCμM process is a simple, relatively rapid technique that can be used to make highly compliant electronic structures with patternable geometries.

  10. Nanoporous materials from stable and metastable structures of 1,2-PB-b-PDMS block copolymers

    DEFF Research Database (Denmark)

    Schulte, Lars; Grydgaard, Anne; Jakobsen, Mathilde R.


    matrix component) and secondly degrading PDMS (the expendable component). Depending on the temperature of the cross-linking reaction different morphologies can be ‘frozen’ from the same block copolymer. Starting with a block copolymer precursor of lamellar morphology at room temperature, the gyroid...... structure or a metastable structure showing hexagonal symmetry (probably HPL) were permanently captured by cross-linking the precursor at 140 °C or at 85 °C, respectively. PDMS was degraded by reaction with tetrabutylamonium fluoride; considerations on the mechanism of cleaving reaction are presented....... The characterization of the materials at different stages of preparation includes gravimetry, infrared spectroscopy, small angle x-ray scattering, electron microscopy and isothermal nitrogen adsorption experiments....

  11. A simple method for fabricating multi-layer PDMS structures for 3D microfluidic chips

    KAUST Repository

    Zhang, Mengying


    We report a simple methodology to fabricate PDMS multi-layer microfluidic chips. A PDMS slab was surface-treated by trichloro (1H,1H,2H,2H-perfluorooctyl) silane, and acts as a reusable transferring layer. Uniformity of the thickness of the patterned PDMS layer and the well-alignment could be achieved due to the transparency and proper flexibility of this transferring layer. Surface treatment results are confirmed by XPS and contact angle testing, while bonding forces between different layers were measured for better understanding of the transferring process. We have also designed and fabricated a few simple types of 3D PDMS chip, especially one consisting of 6 thin layers (each with thickness of 50 μm), to demonstrate the potential utilization of this technique. 3D fluorescence images were taken by a confocal microscope to illustrate the spatial characters of essential parts. This fabrication method is confirmed to be fast, simple, repeatable, low cost and possible to be mechanized for mass production. © The Royal Society of Chemistry 2010.

  12. Fabrication of Photonic Crystal Structures on Flexible Organic Light-Emitting Diodes by Using Nano-Imprint and PDMS Mold

    Directory of Open Access Journals (Sweden)

    Ho Ting-Lin


    Full Text Available In this paper, nanoimprint lithography was used to create a photonic crystals structure film in organic light-emitting diode (OLED component, and then compare the efficiency of components whether with nanostructure or not. By using two different kinds of mold, such as silicon mold and PDMS mold, the nano structures in PMMA (molecular weight of 350K were fabricated. Nanostructures in period of 403.53nm with silicon mold and nano structures in period of 385.64nm with PDMS mold as photonic crystal films were fabricated and were integrated into OLED. In experimental results, the OLED without photonic crystal films (with packing behaves 193.3cd/m2 for luminous intensity, 3.481cd/A for lightening efficiency (ηL and 0.781 lm/W for lightening power (ηP where V is 14V and I is 5.5537mA; the OLED with photonic crystal films (with packing behaves 241.6cd/m2 for luminous intensity, 4.173cd/A for lightening efficiency (ηL and 0.936 lm/W for lightening power (ηP where voltage of 14V and current (I of 5.7891mA, which shows that the latter perform is well.

  13. Time-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures

    KAUST Repository

    Mishra, Himanshu


    Wetting of rough surfaces involves time-dependent effects, such as surface deformations, non-uniform filling of surface pores within or outside the contact area, and surface chemistries, but the detailed impact of these phenomena on wetting is not entirely clear. Understanding these effects is crucial for designing coatings for a wide range of applications, such as membrane-based oil-water separation and desalination, waterproof linings/windows for automobiles, aircrafts, and naval vessels, and antibiofouling. Herein, we report on time-dependent contact angles of water droplets on a rough polydimethylsiloxane (PDMS) surface that cannot be completely described by the conventional Cassie-Baxter or Wenzel models or the recently proposed Cassie-impregnated model. Shells of sand dollars (Dendraster excentricus) were used as lithography-free, robust templates to produce rough PDMS surfaces with hierarchical, periodic features ranging from 10-7-10-4 m. Under saturated vapor conditions, we found that in the short-term (<1 min), the contact angle of a sessile water droplet on the templated PDMS, θSDT = 140° ± 3°, was accurately described by the Cassie-Baxter model (predicted θSDT = 137°); however, after 90 min, θSDT fell to 110°. Fluorescent confocal microscopy confirmed that the initial reduction in θSDT to 110° (the Wenzel limit) was primarily a Cassie-Baxter to Wenzel transition during which pores within the contact area filled gradually, and more rapidly for ethanol-water mixtures. After 90 min, the contact line of the water droplet became pinned, perhaps caused by viscoelastic deformation of the PDMS around the contact line, and a significant volume of water began to flow from the droplet to pores outside the contact region, causing θSDT to decrease to 65° over 48 h on the rough surface. The system we present here to explore the concept of contact angle time dependence (dynamics) and modeling of natural surfaces provides insights into the design and

  14. Rapid bonding of polydimethylsiloxane (PDMS) to various stereolithographically (STL) structurable epoxy resins using photochemically cross-linked intermediary siloxane layers (United States)

    Wilhelm, Elisabeth; Neumann, Christiane; Sachsenheimer, Kai; Länge, Kerstin; Rapp, Bastian E.


    In this paper we present a fast, low cost bonding technology for combining rigid epoxy components with soft membranes made out of polydimethylsiloxane (PDMS). Both materials are commonly used for microfluidic prototyping. Epoxy resins are often applied when rigid channels are required, that will not deform if exposed to high pressure. PDMS, on the other hand, is a flexible material, which allows integration of membrane valves on the chip. However, the integration of pressure driven components, such as membrane valves and pumps, into a completely flexible device leads to pressure losses. In order to build up pressure driven components with maximum energy efficiency a combination of rigid guiding channels and flexible membranes would be advisable. Stereolithographic (STL) structuring would be an ideal fabrication technique for this purpose, because complex 3D-channels structures can easily be fabricated using this technology. Unfortunately, the STL epoxies cannot be bonded using common bonding techniques. For this reason we propose two UV-light based silanization techniques that enable plasma induced bonding of epoxy components. The entire process including silanization and corona discharge bonding can be carried out within half an hour. Average bond strengths up to 350 kPa (depending on the silane) were determined in ISO-conform tensile testing. The applicability of both techniques for microfluidic applications was proven by hydrolytic stability testing lasting more than 40 hours.

  15. Silver nanowire-embedded PDMS with a multiscale structure for a highly sensitive and robust flexible pressure sensor. (United States)

    Joo, Yunsik; Byun, Junghwan; Seong, Narkhyeon; Ha, Jewook; Kim, Hyunjong; Kim, Sangwoo; Kim, Taehoon; Im, Hwarim; Kim, Donghyun; Hong, Yongtaek


    The development of highly sensitive pressure sensors with a low-cost and facile fabrication technique is desirable for electronic skins and wearable sensing devices. Here a low-cost and facile fabrication strategy to obtain multiscale-structured elastomeric electrodes and a highly sensitive and robust flexible pressure sensor is presented. The principles of spontaneous buckle formation of the PDMS surface and the embedding of silver nanowires are used to fabricate the multiscale-structured elastomeric electrode. By laminating the multiscale-structured elastomeric electrode onto the dielectric layer/bottom electrode template, the pressure sensor can be obtained. The pressure sensor is based on the capacitive sensing mechanism and shows high sensitivity (>3.8 kPa(-1)), fast response and relaxation time (pressure sensor arrays and they can detect the spatial distribution of the applied pressure. It is also demonstrated that the fingertip pressure sensing device can sense the pressure distribution of each finger, when grabbing an object.

  16. Molecular dynamics insights into the structural and diffusive properties of ZIF-8/PDMS mixed matrix membranes in the n-butanol/water pervaporation process (United States)

    Sun, Tao; Fang, Manquan; Wu, Zhen; Yu, Lixin; Li, Jiding


    Molecular dynamics (MD) simulation was used to study the structural and diffusive properties of zeolitic imidazolate framework-8 (ZIF-8)/polydimethylsiloxane (PDMS), a novel alcohol-permselective mixed matrix membrane (MMM). Simulation models of one pure PDMS membrane and three ZIF-8/PDMS MMMs with increasing loadings were successfully constructed. Non-bond energy turned out to be a strong attractive interaction between the PDMS matrix and ZIF-8 cells. The morphology and mobility of PDMS chains were characterized by mean square displacement (MSD). The fraction of free volume (FFV) of the pure membrane and MMMs was calculated and showed declining trends with increasing ZIF-8 loadings. The diffusion coefficients of n-butanol and water molecules were calculated by the Einstein relation. {D}n-\\text{butanol} first increased then decreased, while {D}{{water}} decreased with the increasing loadings. The mechanism of selective diffusion behaviour was investigated and it was found that the inner channels of ZIF-8 provided selective pathways for n-butanol. Diffusion coefficients were correlated with FFV and the results showed that the logarithm of {D}{{water}} demonstrated a good linear relation with the inverse FFV and was in agreement with the free volume theory, while {D}n-\\text{butanol} showed a significant deviation in the case of MMM-1 due to the selective diffusion channels provided by ZIF-8.

  17. Canonical structure of 2D black holes

    CERN Document Server

    Navarro-Salas, J; Talavera, C F


    We determine the canonical structure of two-dimensional black-hole solutions arising in $2D$ dilaton gravity. By choosing the Cauchy surface appropriately we find that the canonically conjugate variable to the black hole mass is given by the difference of local (Schwarzschild) time translations at right and left spatial infinities. This can be regarded as a generalization of Birkhoff's theorem.

  18. 基于微流体芯片结构的PDMS二次倒模工艺研究%Research on twice molding technology of PDMS based on microfluidic chip structure

    Institute of Scientific and Technical Information of China (English)

    郝晓剑; 张斌珍; 杨潞霞; 范新磊; 姚德启; 王春水


    研究了用于制作微流体芯片结构的聚二甲基硅氧烷(PDMS)与PDMS之间的倒模方法.首先,通过使用同一个微流体芯片模具倒出多个相同的PDMS负模结构;接着分别在各负模结构上溅射不同种类、不同厚度的金属,然后再对溅射过金属的负模上浇铸PDMS并固化以进行二次倒模,最后对二次倒模出的PDMS微流体结构表面粘连、结构完整性、尺寸等进行观测,从而通过比较得到倒模溅射所需的最佳金属和溅射金属薄膜的最优厚度.此方法倒出的PDMS微流体结构完整性好,不仅提出了一种全新的用于PDMS倒模的方法,而且解决了PDMS与PDMS之间直接倒模时所遇到的相互粘连和结构撕裂等难题.%The molding methods for polydimethylsiloxane( PDMS)and mold of PDMS based on microfulidic chip structure are investigated. Firstly, mold several same PDMS negative mold structures by using the same microfluidic chip. Then,sputter different thickness and types of metals on the PDMS negative mold structures,and then mold on it. Finally the structure of the secondary mold surface adhesion, structural integrity and size are investigated to determine the optimal metal and thickness. The PDMS microfluidic structural integrity is good by means of this method. This is not only a new method for PDMS molding,but also a novel solution to the mutual adhesion between PDMS and the PDMS mold and structural tear while molding directly and provides a good reference for which can not mold to get the structure of complex microfluidic chips.

  19. Influence of 1,2-PB matrix cross-linking on structure and properties of selectively etched 1,2-PB-b-PDMS block copolymers

    DEFF Research Database (Denmark)

    Guo, Fengxiao; Andreasen, Jens Wenzel; Vigild, Martin Etchells;


    A series of samples with varying cross-linking degree were prepared from the same 1,2-polybutadiene-b-polydimethylsiloxane (1,2-PB-b-PDMS) diblock copolymer precursor. The stability of nanopores generated after PDMS cleaving depends on the cross-linking degree of 1,2-PB. The swelling ratio...

  20. 3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting. (United States)

    Fassler, Andrew; Majidi, Carmel


    Liquid phase electronic circuits are created by freeze casting gallium-indium (GaIn) alloys, such as eutectic gallium-indium (EGaIn), and encapsulating these frozen components within an elastomer. These metal alloys are liquid at room temperature, and can be cast using either injection or a vacuum to fill a PDMS mold and placing the mold in a freezer. Once solidified, a GaIn alloy segment can be manipulated, altered, or bonded to other circuit elements. A stretchable circuit can be fabricated by placing frozen components onto an elastomer substrate, which can be either patterned or flat, and sealing with an additional layer of elastomer. Circuits produced in this fashion are soft, stretchable, and can have complex 3D channel geometries. In contrast, current fabrication techniques, including needle injection, mask deposition, and microcontact printing, are limited to 2D planar designs. Additionally, freeze casting fabrication can create closed loops, multi-terminal circuits with branching features, and large area geometries.

  1. Hawking Radiation from Regular Black Hole as a Possible Probe for Black Hole Interior Structure

    CERN Document Server

    Deng, Yanbin


    The notion of the black hole singularity and the proof of the singularity theorem in general relativity were considered great successes in gravitational physics. On the other hand they also presented deep puzzles to physicists. Conceptual challenges were set up by the intractability of the singularity. The existence of black hole horizons which cover up the interior, including the singularity of the black hole from outside observers, builds an information curtain, further hindering physicists from understanding the nature of the singularity and the interior structure of black holes. The regular black hole is a concept produced out of multiple attempts to establish a tractable and understandable interior structure for black hole and to avoid the singularity inside the black hole body. A method is needed to check the correctness of the new constructions of black holes. After studying the Hawking radiation by fermion tunnelling from one type of regular black hole, structure dependent results were obtained. The r...

  2. Lifetime of Nano-Structured Black Silicon for Photovoltaic Applications

    DEFF Research Database (Denmark)

    Plakhotnyuk, Maksym; Davidsen, Rasmus Schmidt; Schmidt, Michael Stenbæk;


    In this work, we present recent results of lifetime optimization for nano-structured black silicon and its photovoltaic applications. Black silicon nano-structures provide significant reduction of silicon surface reflection due to highly corrugated nanostructures with excellent light trapping pro......, respectively. This is promising for use of black silicon RIE nano-structuring in a solar cell process flow...

  3. Lifetime of Nano-Structured Black Silicon for Photovoltaic Applications

    DEFF Research Database (Denmark)

    Plakhotnyuk, Maksym; Davidsen, Rasmus Schmidt; Schmidt, Michael Stenbæk;


    In this work, we present recent results of lifetime optimization for nano-structured black silicon and its photovoltaic applications. Black silicon nano-structures provide significant reduction of silicon surface reflection due to highly corrugated nanostructures with excellent light trapping......, respectively. This is promising for use of black silicon RIE nano-structuring in a solar cell process flow...

  4. Observational strong gravity and quantum black hole structure

    CERN Document Server

    Giddings, Steven B


    Quantum considerations have led many theorists to believe that classical black hole physics is modified not just deep inside black holes but at horizon scales, or even further outward. The near-horizon regime has just begun to be observationally probed for astrophysical black holes -- both by LIGO, and by the Event Horizon Telescope. This suggests exciting prospects for observational constraints on or discovery of new quantum black hole structure.

  5. Evaluating structural and microstructural changes of PDMS –SiO{sub 2} hybrid materials after sterilization by gamma irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, J. Carlos [Department of Materials and Ceramic Engineering/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Lancastre, Joana [Campus Tecnologico e Nuclear, IST, University of Lisbon, E.N 10, 2686-953 Sacavém (Portugal); Vaz Fernandes, M. Helena [Department of Materials and Ceramic Engineering/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Margaça, Fernanda M.A.; Ferreira, Luís [Campus Tecnologico e Nuclear, IST, University of Lisbon, E.N 10, 2686-953 Sacavém (Portugal); Miranda Salvado, Isabel M., E-mail: [Department of Materials and Ceramic Engineering/CICECO, University of Aveiro, 3810-193 Aveiro (Portugal)


    PDMS–SiO{sub 2} hybrid materials obtained by sol–gel process have been extensively studied over the past years due to its promising biomedical applications namely as bone substitutes, catheters, and drug delivery devices. Regardless of the intended biomedical application, all these materials should go through a sterilization process before interfacing with a living structure. However, it is unclear whether they undergo structural and microstructural changes when subjected to sterilization by gamma irradiation. This paper addresses this issue by showing that a sol–gel processed biomaterial based on the PDMS–CaO–SiO{sub 2} hybrid system suffers only small structural changes when submitted to a radiation dose of 25 kGy, the dose usually recommended to achieve a Sterility Assurance Level of 10{sup −6} when the natural contamination level and microorganism types cannot be calculated. The characterization was assessed by FT-IR, {sup 29}Si–{"1H} CP-MAS, thermal analysis (DTG), and SEM. - Highlights: • Hybrid PDMS–SiO{sub 2} materials were subjected to sterilization by γ-irradiation. • Materials suffer only small structural changes when irradiated. • Characterization was assessed by FT-IR, {sup 29}Si-{"1H} CP-MAS, DTG and SEM.

  6. Fabrication of hybrid nanostructured arrays using a PDMS/PDMS replication process. (United States)

    Hassanin, H; Mohammadkhani, A; Jiang, K


    In the study, a novel and low cost nanofabrication process is proposed for producing hybrid polydimethylsiloxane (PDMS) nanostructured arrays. The proposed process involves monolayer self-assembly of polystyrene (PS) spheres, PDMS nanoreplication, thin film coating, and PDMS to PDMS (PDMS/PDMS) replication. A self-assembled monolayer of PS spheres is used as the first template. Second, a PDMS template is achieved by replica moulding. Third, the PDMS template is coated with a platinum or gold layer. Finally, a PDMS nanostructured array is developed by casting PDMS slurry on top of the coated PDMS. The cured PDMS is peeled off and used as a replica surface. In this study, the influences of the coating on the PDMS topography, contact angle of the PDMS slurry and the peeling off ability are discussed in detail. From experimental evaluation, a thickness of at least 20 nm gold layer or 40 nm platinum layer on the surface of the PDMS template improves the contact angle and eases peeling off. The coated PDMS surface is successfully used as a template to achieve the replica with a uniform array via PDMS/PDMS replication process. Both the PDMS template and the replica are free of defects and also undistorted after demoulding with a highly ordered hexagonal arrangement. In addition, the geometry of the nanostructured PDMS can be controlled by changing the thickness of the deposited layer. The simplicity and the controllability of the process show great promise as a robust nanoreplication method for functional applications.

  7. Improved actuation strain of PDMS-based DEA materials chemically modified with softening agents (United States)

    Biedermann, Miriam; Blümke, Martin; Wegener, Michael; Krüger, Hartmut


    Dielectric elastomer actuators (DEAs) are smart materials that gained much in interest particularly in recent years. One active field of research is the improvement of their properties by modification of their structural framework. The object of this work is to improve the actuation properties of polydimethylsiloxane (PDMS)-based DEAs by covalent incorporation of mono-vinyl-terminated low-molecular PDMS chains into the PDMS network. These low-molecular units act as a kind of softener within the PDMS network. The loose chain ends interfere with the network formation and lower the network's density. PDMS films with up to 50wt% of low-molecular PDMS additives were manufactured and the chemical, mechanical, electrical, and electromechanical properties of these novel materials were investigated.

  8. Biaxially stretchable silver nanowire conductive film embedded in a taro leaf-templated PDMS surface (United States)

    Wu, Chunhui; Jiu, Jinting; Araki, Teppei; Koga, Hirotaka; Sekitani, Tsuyoshi; Wang, Hao; Suganuma, Katsuaki


    A biaxially wave-shaped polydimethylsiloxane (PDMS) surface was developed simply by using a taro leaf as the template. The resulting leaf-templated PDMS (L-PDMS) possesses a micro-sized curved interface structure, which is greatly beneficial for the exact embedding of a silver nanowire (AgNW) network conductive film covering the L-PDMS surface. The intrinsically curved AgNW/L-PDMS film surface, without any dangling nanowire, could prevent the fracture of AgNWs due to stretching stress even after cyclic stretching. More importantly, it also exhibited a biaxial stretchability, which showed ultra-stable resistance after continuous stretching for 100 cycles each in X- and Y-directions. This biaxially stretchable AgNW/L-PDMS film could extend the application fields in stretchable electronics.

  9. Anti-stiction coating of PDMS moulds for rapid microchannel fabrication by double replica moulding

    DEFF Research Database (Denmark)

    Zhuang, Guisheng; Kutter, Jörg Peter


    ), which resulted in an anti-stiction layer for the improved release after PDMS casting. The deposition of FDTS on an O2 plasma-activated surface of PDMS produced a reproducible and well-performing anti-stiction monolayer of fluorocarbon, and we used the FDTS-coated moulds as micro-masters for rapid......In this paper, we report a simple and precise method to rapidly replicate master structures for fast microchannel fabrication by double replica moulding of polydimethylsiloxane (PDMS). A PDMS mould was surface-treated by vapour phase deposition of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS...

  10. Surface micromachined PDMS microfluidic devices fabricated using a sacrificial photoresist (United States)

    Ganapathy Subramani, Balasubramanian; Selvaganapathy, Ponnambalam Ravi


    PDMS is a widely used material for construction of microfluidic devices. The traditional PDMS microfabrication process, although versatile, cannot be used to form microfluidic devices with embedded tall topological features, such as thick-film electrodes and porous reactor beds. This paper presents an elegant surface micromachining process for microfluidic devices that allows complete leak-proof sealing and a conformal contact of the PDMS with tall pre-existing topographical features and demonstrates this approach by embedding 6 µm thick Ag/AgCl (high capacity 1680 µA s) electrodes inside the microchannels. In this process, thin spin-cast films of the PDMS are used as the structural material and a photoresist is used as the sacrificial material. A crucial parameter, namely adhesion of the spun-cast structural layer to the substrate, was characterized for different pre-polymer ratios using a standard tensile test, and a 1:3 (curing agent:base) combination was found to be the best with a maximum adhesion strength of 7.2 MPa. The elastic property of the PDMS allowed extremely fast release times of ~1 min of the fabricated microchannels. The versatility of this process was demonstrated by the fabrication of a pneumatic microvalve with multi-layered microchannel geometry. The valve closure occurred at 6.37 kPa. Preliminary results of this paper have been presented at the Canadian Workshop on MEMS and Microfluidics, Montréal, Canada, August 2007.

  11. Effect of Rheological Properties of Phenolic Resin/PDMS-OH Blend on Its Foam's Cell Structure%PF/PDMS-OH流变性能对其泡沫材料泡孔结构的影响

    Institute of Scientific and Technical Information of China (English)

    王梦蕾; 俞科静; 钱坤


    The phenolic (PF) resin was modified by hydroxyl terminated polysiloxane (PDMS–OH) with different mass fraction of 10%,15% and 20% though mechanical blending respectively. A series of PF/PDMS–OH foam composites,based on the modified resin were prepared by chemical foaming method. The static/dynamic rheological behavior of PF/PDMS–OH foam composites was characterized by rotary rheometer to study the effect of viscoelastic response of resin blends on the foaming behavior. Fourier transform infrared spectroscopy (FTIR) was used to study the chemical reaction between PF resin and PDMS–OH during the curing process. Scanning electron microscope (SEM) was used to observe the cell structure of PF foam. The results indicate that the resin blend with 15% PDMS–OH present thebest viscoelasticity for foaming. There is chemical cross-linking between PDMS–OH and PF,which all contribute to impact the cell morphology of PF/PDMS–OH foam. Meanwhile,FTIR results show that the chemical bond between phenolic resin and PDMS–OH is built during the curing process,the cross-linking structure provide resin and foam with more stable soft segment.%分别将质量分数为10%,15%和20%的端羟基聚硅氧烷(PDMS–OH)通过机械共混的方法改性酚醛树脂(PF),进而采用化学发泡的方法制备PF/PDMS–OH泡沫复合材料。采用旋转式流变仪表征共混体系的稳态及动态流变性能,研究黏弹性对树脂发泡过程的影响。傅立叶变换红外光谱表征PDMS–OH与树脂在固化过程中的化学反应。扫描电镜表征不同共混体系下泡孔的结构与形态。结果表明,加入15% PDMS–OH的共混体系具有最利于发泡成型的黏弹性,且可与PF形成化学交联作用,对PF泡沫的泡孔形态影响显著。同时红外表征显示,PDMS–OH与PF在固化过程中发生化学交联,这种互穿交联网状结构为PF及泡沫提供了更多稳定的柔性链段。

  12. Supermassive black holes, large scale structure and holography

    CERN Document Server

    Mongan, T R


    A holographic analysis of large scale structure in the universe estimates the mass of supermassive black holes at the center of large scale structures with matter density varying inversely as the square of the distance from their center. The estimate is consistent with two important test cases involving observations of the supermassive black hole with mass 3.6\\times10^{-6} times the galactic mass in Sagittarius A^{*} near the center of our Milky Way and the 2\\times10^{9} solar mass black hole in the quasar ULAS J112001.48+064124.3 at redshift z=7.085. It is also consistent with upper bounds on central black hole masses in globular clusters M15, M19 and M22 developed using the Jansky Very Large Array in New Mexico.

  13. Benchtop fabrication of PDMS microstructures by an unconventional photolithographic method

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Chang Mo; Sim, Woo Young; Lee, Seung Hwan; Foudeh, Amir M; Bae, Hojae; Khademhosseini, Ali [Center for Biomedical Engineering, Department of Medicine, Brigham and Women' s Hospital, Harvard Medical School, 65 Landsdowne Street, Cambridge, MA 02139 (United States); Lee, Sang-Hoon, E-mail: alik@rics.bwh.harvard.ed, E-mail: [Department of Biomedical Engineering, College of Health Science, Korea University, Jeongneung-dong, Seongbuk-gu, Seoul 136-703 (Korea, Republic of)


    Poly(dimethylsiloxane) (PDMS) microstructures have been widely used in bio-microelectromechanical systems (bio-MEMS) for various types of analytical, diagnostic and therapeutic applications. However, PDMS-based soft lithographic techniques still use conventional microfabrication processes to generate a master mold, which requires access to clean room facilities and costly equipment. With the increasing use of these systems in various fields, the development of benchtop systems for fabricating microdevices is emerging as an important challenge in their widespread use. Here we demonstrate a simple, low-cost and rapid method to fabricate PDMS microstructures by using micropatterned poly(ethylene glycol) diacrylate (PEGDA) master molds. In this method, PEGDA microstructures were patterned on a glass substrate by photolithography under ambient conditions and by using simple tools. The resulting PEGDA structures were subsequently used to generate PDMS microstructures by standard molding in a reproducible and repeatable manner. The thickness of the PEGDA microstructures was controllable from 15 to 300 {mu}m by using commonly available spacer materials. We also demonstrate the use of this method to fabricate microfluidic channels capable of generating concentration gradients. In addition, we fabricated PEGDA microstructures by photolithography from the light generated from commonly available laminar cell culture hood. These data suggest that this approach could be beneficial for fabricating low-cost PDMS-based microdevices in resource limited settings.

  14. Structural and magnetic properties of Fe{sub 2-x}CoSm{sub x}O{sub 4}-nanoparticles and Fe{sub 2-x}CoSm{sub x}O{sub 4}-PDMS magnetoelastomers as a function of Sm content

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz, Mariano M.; Mietta, Jose L.; Soledad Antonel, P. [Instituto de Quimica Fisica de Materiales, Ambiente y Energia (INQUIMAE), Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Cantilo s/n (1428), Buenos Aires (Argentina); Perez, Oscar E. [Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Cantilo s/n (1428), Buenos Aires (Argentina); Martin Negri, R. [Instituto de Quimica Fisica de Materiales, Ambiente y Energia (INQUIMAE), Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Cantilo s/n (1428), Buenos Aires (Argentina); Jorge, Guillermo, E-mail: [Instituto de Fisica de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Av. Cantilo s/n (1428), Buenos Aires (Argentina); Instituto de Ciencias, Universidad Nacional de General Sarmiento, J.M. Gutierrez 1150 (1613), Los Polvorines, Buenos Aires (Argentina)


    We have synthesized magnetic Fe{sub 2-x}CoSm{sub x}O{sub 4} nanoparticles (NPs) by means of the coprecipitation method, varying Sm content from x=0 to x=0.5. Energy-dispersive X-ray spectroscopy showed agreement between the metal proportion of the obtained nanoparticles and the stoichiometric mixture of cations used for the synthesis. Part of the particles were heated at 800 Degree-Sign C, and both were characterized by X-ray diffraction, scanning electron microscope imaging and magnetization measurements. Physical and magnetic properties were analyzed as a function of Sm content, before and after the heating treatment. A phase segregation is found for the calcined nanoparticles with large Sm content. The magnetic remanence, saturation and coercive field were investigated as a function of Sm content for both heated and unheated (as-prepared) particles. Polydimethylsiloxane-NPs magnetoelastomers were prepared and cured under an external uniform magnetic field, obtaining structured anisotropic composites, in which inorganic needles (columnar micrometric structures) oriented in the direction of the magnetic field are formed. Young modulus and remanent magnetic moment were measured and magnetization time relaxation experiments were performed in the directions parallel and perpendicular to the needles in order to determine the magnetic and elastic anisotropy of the composites. The elastic modulus measured parallel to the needles resulted almost twice in magnitude with respect to the perpendicular modulus. The measured magnetic anisotropy of the composites is probably due to the enhanced interparticle interaction within a needle and the freezing of an preferred easy axis distribution among the particles at the curing process. - Highlights: Black-Right-Pointing-Pointer We study magnetic and physical properties of Sm-substituted Fe{sub 2}CoO{sub 4} nanoparticles. Black-Right-Pointing-Pointer Magnetic nanoparticles were synthesized by the coprecipitation method. Black

  15. Stretchable electronics based on Ag-PDMS composites (United States)

    Larmagnac, Alexandre; Eggenberger, Samuel; Janossy, Hanna; Vörös, Janos


    Patterned structures of flexible, stretchable, electrically conductive materials on soft substrates could lead to novel electronic devices with unique mechanical properties allowing them to bend, fold, stretch or conform to their environment. For the last decade, research on improving the stretchability of circuits on elastomeric substrates has made significant progresses but designing printed circuit assemblies on elastomers remains challenging. Here we present a simple, cost-effective, cleanroom-free process to produce large scale soft electronic hardware where standard surface-mounted electrical components were directly bonded onto all-elastomeric printed circuit boards, or soft PCBs. Ag-PDMS tracks were stencil printed onto a PDMS substrate and soft PCBs were made by bonding the top and bottom layers together and filling punched holes with Ag-PDMS to create vias. Silver epoxy was used to bond commercial electrical components and no mechanical failure was observed after hundreds of stretching cycles. We also demonstrate the fabrication of a stretchable clock generator.

  16. Universal near-horizon conformal structure and black hole entropy

    CERN Document Server

    Chakrabarti, Sayan K; Sen, Siddhartha


    It is shown that a massless scalar probe reveals a universal near-horizon conformal structure for a wide class of black holes, including the BTZ. The central charge of the corresponding Virasoro algebra contains information about the black hole. With a suitable quantization condition on the central charge, the CFT associated with the black hole in our approach is consistent with the recent observation of Witten, where the dual theory for the BTZ in the AdS/CFT framework has been identified with the construction of Frenkel, Lepowsky and Meurman. This CFT admits the Fischer-Griess monster group as its symmetry. The logarithm of the dimension of a specific representation of the monster group has been identified by Witten as the entropy of the BTZ black hole. Our algebraic approach shows that a wide class of black holes share the same near-horizon conformal structure as that for the BTZ. With a suitable quantization condition, the CFT's for all these black holes can be identified with the FLM model and the corres...

  17. Varying Fine Structure Constant and Black Hole Physics

    CERN Document Server

    Das, S; Das, Saurya; Kunstatter, Gabor


    Recent astrophysical observations suggest that the fine structure constant $\\alpha=e^2/\\hbar c$ may be slowly increasing with time. This may be due to an increase of $e$ or a decrease of $c$, or both. In this article, we argue from model independent considerations that this variation should be considered adiabatic. Then, we examine in detail the consequences of such an adiabatic variation in the context of a specific model of quantized charged black holes. We find that the second law of black hole thermodynamics is obeyed, regardless of the origin of the variation, and that interesting constraints arise on the charge and mass of black holes. Finally, we estimate the work done on a black hole of mass $M$ due to the $\\alpha$ variation.

  18. Global Structure of Exact Scalar Hairy Dynamical Black Holes

    CERN Document Server

    Fan, Zhong-Ying; Lu, Hong


    We study the global structure of some exact scalar hairy dynamical black holes which were constructed in Einstein gravity either minimally or non-minimally coupled to a scalar field. We find that both the apparent horizon and the local event horizon (measured in luminosity coordinate) monotonically increase with the advanced time as well as the Vaidya mass. At late advanced times, the apparent horizon approaches the event horizon and gradually becomes future outer. Correspondingly, the space-time arrives at stationary black hole states with the relaxation time inversely proportional to the $1/(n-1)$ power of the final black hole mass. These results strongly support the solutions describing the formation of black holes with scalar hair. We also obtain new charged dynamical solutions in the non-minimal theory by introducing an Maxwell field which is non-minimally coupled to the scalar. The presence of the electric charge strongly modifies the dynamical evolution of the space-time.


    Institute of Scientific and Technical Information of China (English)

    Ze-yong Zhao; Wei-wei Yap; Rong-ni Du; Qin Zhang; Qiang Fu; Ze-hao Qiu; Su-lan Yuan


    A series of polydimethylsiloxane (PDMS) with varied molecular weights (Mw = 3x106,1x106 and 0.5x106)were melt blended with PP to investigate the effect of PDMS molecular weight (MW) on the morphology and mechanical properties of PP/PDMS blends.Scanning electron microscopic (SEM) examination showed that the size of PDMS domains was dependent on the MW of PDMS.It was found that the lower the value of PDMS MW,the better dispersion of the PDMS domains in the PP matrix.Tensile and Izod impact tests revealed that the addition of PDMS with lower MW would lead to a more significant increase in impact strength of the blends compared with the blends with higher MW ones,while the influence of the molecular weight on tensile strengths of the blends was relatively small in the MW range studied.Differential scanning calorimetry (DSC) results also showed that the crystallization temperature of PP was increased with decreasing PDMS MW,indicating a better nucleation capability of lower MW of PDMS.Melting flow rate (MFR)measurements indicated that the processibility of PP could be enhanced by adding PDMS,and again the lower MW PDMS resulted in better data.Our work demonstrates that not only the processibility but also the mechanical properties of PP could be enhanced to a more significant degree by using low MW PDMS than the higher ones.

  20. Visualisation and characterisation of heterogeneous bimodal PDMS networks

    DEFF Research Database (Denmark)

    Bahrt, Frederikke; Daugaard, Anders Egede; Fleury, Clemence;


    by rheology. All heterogeneous bimodal networks displayed significantly lower moduli than mono-modal PDMS elastomers prepared from the long polymer chains. Low-loss moduli as well as low-sol fractions indicate that low-elastic moduli can be obtained without compromising the network's structure...

  1. Self-regenerating and hybrid irreversible/reversible PDMS microfluidic devices (United States)

    Shiroma, Letícia S.; Piazzetta, Maria H. O.; Duarte-Junior, Gerson F.; Coltro, Wendell K. T.; Carrilho, Emanuel; Gobbi, Angelo L.; Lima, Renato S.


    This paper outlines a straightforward, fast, and low-cost method to fabricate polydimethylsiloxane (PDMS) chips. Termed sandwich bonding (SWB), this method requires only a laboratory oven. Initially, SWB relies on the reversible bonding of a coverslip over PDMS channels. The coverslip is smaller than the substrate, leaving a border around the substrate exposed. Subsequently, a liquid composed of PDMS monomers and a curing agent is poured onto the structure. Finally, the cover is cured. We focused on PDMS/glass chips because of their key advantages in microfluidics. Despite its simplicity, this method created high-performance microfluidic channels. Such structures featured self-regeneration after leakages and hybrid irreversible/reversible behavior. The reversible nature was achieved by removing the cover of PDMS with acetone. Thus, the PDMS substrate and glass coverslip could be detached for reuse. These abilities are essential in the stages of research and development. Additionally, SWB avoids the use of surface oxidation, half-cured PDMS as an adhesive, and surface chemical modification. As a consequence, SWB allows surface modifications before the bonding, a long time for alignment, the enclosure of sub-micron channels, and the prototyping of hybrid devices. Here, the technique was successfully applied to bond PDMS to Au and Al.

  2. Polydimethylsiloxane (PDMS) modulates CD38 expression, absorbs retinoic acid and may perturb retinoid signalling. (United States)

    Futrega, Kathryn; Yu, Jianshi; Jones, Jace W; Kane, Maureen A; Lott, William B; Atkinson, Kerry; Doran, Michael R


    Polydimethylsiloxane (PDMS) is the most commonly used material in the manufacture of customized cell culture devices. While there is concern that uncured PDMS oligomers may leach into culture medium and/or hydrophobic molecules may be absorbed into PDMS structures, there is no consensus on how or if PDMS influences cell behaviour. We observed that human umbilical cord blood (CB)-derived CD34(+) cells expanded in standard culture medium on PDMS exhibit reduced CD38 surface expression, relative to cells cultured on tissue culture polystyrene (TCP). All-trans retinoic acid (ATRA) induces CD38 expression, and we reasoned that this hydrophobic molecule might be absorbed by PDMS. Through a series of experiments we demonstrated that ATRA-mediated CD38 expression was attenuated when cultures were maintained on PDMS. Medium pre-incubated on PDMS for extended durations resulted in a time-dependant reduction of ATRA in the medium and increasingly attenuated CD38 expression. This indicated a time-dependent absorption of ATRA into the PDMS. To better understand how PDMS might generally influence cell behaviour, Ingenuity Pathway Analysis (IPA) was used to identify potential upstream regulators. This analysis was performed for differentially expressed genes in primary cells including CD34(+) haematopoietic progenitor cells, mesenchymal stromal cells (MSC), and keratinocytes, and cell lines including prostate cancer epithelial cells (LNCaP), breast cancer epithelial cells (MCF-7), and myeloid leukaemia cells (KG1a). IPA predicted that the most likely common upstream regulator of perturbed pathways was ATRA. We demonstrate here that ATRA is absorbed by PDMS in a time-dependent manner and results in the concomitant reduced expression of CD38 on the cell surface of CB-derived CD34(+) cells.

  3. Atomic and electronic structure of exfoliated black phosphorus

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Ryan J.; Topsakal, Mehmet; Jeong, Jong Seok; Wentzcovitch, Renata M.; Mkhoyan, K. Andre, E-mail: [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Low, Tony; Robbins, Matthew C.; Haratipour, Nazila; Koester, Steven J. [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)


    Black phosphorus, a layered two-dimensional crystal with tunable electronic properties and high hole mobility, is quickly emerging as a promising candidate for future electronic and photonic devices. Although theoretical studies using ab initio calculations have tried to predict its atomic and electronic structure, uncertainty in its fundamental properties due to a lack of clear experimental evidence continues to stymie our full understanding and application of this novel material. In this work, aberration-corrected scanning transmission electron microscopy and ab initio calculations are used to study the crystal structure of few-layer black phosphorus. Directly interpretable annular dark-field images provide a three-dimensional atomic-resolution view of this layered material in which its stacking order and all three lattice parameters can be unambiguously identified. In addition, electron energy-loss spectroscopy (EELS) is used to measure the conduction band density of states of black phosphorus, which agrees well with the results of density functional theory calculations performed for the experimentally determined crystal. Furthermore, experimental EELS measurements of interband transitions and surface plasmon excitations are also consistent with simulated results. Finally, the effects of oxidation on both the atomic and electronic structure of black phosphorus are analyzed to explain observed device degradation. The transformation of black phosphorus into amorphous PO{sub 3} or H{sub 3}PO{sub 3} during oxidation may ultimately be responsible for the degradation of devices exposed to atmosphere over time.

  4. Constructing Black Titania with Unique Nanocage Structure for Solar Desalination. (United States)

    Zhu, Guilian; Xu, Jijian; Zhao, Wenli; Huang, Fuqiang


    Solar desalination driven by solar radiation as heat source is freely available, however, hindered by low efficiency. Herein, we first design and synthesize black titania with a unique nanocage structure simultaneously with light trapping effect to enhance light harvesting, well-crystallized interconnected nanograins to accelerate the heat transfer from titania to water and with opening mesopores (4-10 nm) to facilitate the permeation of water vapor. Furthermore, the coated self-floating black titania nanocages film localizes the temperature increase at the water-air interface rather than uniformly heating the bulk of the water, which ultimately results in a solar-thermal conversion efficiency as high as 70.9% under a simulated solar light with an intensity of 1 kW m(-2) (1 sun). This finding should inspire new black materials with rationally designed structure for superior solar desalination performance.

  5. Subcrustal structure of the black sea basin from seismological data (United States)

    Yanovskaya, T. B.; Gobarenko, V. S.; Yegorova, T. P.


    The P-wave travel time data from the earthquakes offshore and onshore around the Black Sea are used for the tomographic reconstruction of the three-dimensional (3D) velocity distribution in the lithosphere of the region. The preliminary refinement of the foci parameters (the coordinates and origin time) has reduced the random errors in the travel-time data. The earthquake data were supplemented by the previous deep seismic sounding (DSS) data on the profiles in Crimea and offshore off the Black Sea. The dataset included more than 4000 travel times overall. In order to eliminate the crustal effect, the travel times were reduced to a surface at a depth of 35 km corresponding to the mean Moho depth in the region. The improved crustal model was used for removing the contribution of the crust from the initial data. The new tomography method, which was recently developed by one of the authors and which relies on the assumption of smoothness of the lateral velocity variations, was applied for reconstructing the velocity structure of the upper mantle beneath the Black Sea up to a depth of 95 km. The lateral velocity variation maps at different depths and the vertical velocity distributions along the meridional and sublatitudinal cross sections across the Black Sea were constructed. High velocities were revealed in the subcrustal lithosphere, and the structural difference below two subbasins—the West Black Sea (WBS) and the East Black Sea (EBS) ones—was established. It shows that the high-velocity body below the WBS is located deeper than below the EBS and is distinguished by higher velocities. Based on these results, it is concluded that the lithosphere beneath the Black Sea has a continental origin.

  6. Effects of O2 plasma treatment of PDMS on the deposition of electrospun PVA nanofibers (United States)

    Kobayashi, Natsumi; Miki, Norihisa; Hishida, Koichi; Hotta, Atsushi


    A new polymeric nanofiber-alignment technique with the selective deposition of the nanofibers using oxygen (O2) plasma treatment on a base material for the electrospinning was introduced. Generally, without any pretreatments, electrospun fibers are deposited randomly on the collector. In this work, we focused on the O2 plasma treatment of the surface of the base material to modify the surface morphology and to add polar groups to the surface. O2 plasma-treated and untreated surface of poly (dimethylsiloxane) (PDMS) was prepared by masking a part of PDMS film by another PDMS film. The polyvinyl alcohol (PVA) fibers were then deposited onto the PDMS film. The surface structure of the PDMS film with PVA nanofibers was analyzed by scanning electron microscopy, water contact angle measurements, and X-ray photon spectroscopy. Only a few PVA nanofibers were deposited randomly on the untreated area of the PDMS film, while a number of PVA nanofibers were selectively deposited onto the O2 plasma-treated area. Intriguingly, PVA nanofibers were neatly aligned along the border of the untreated and the treated areas. The contact angle of the plasma-treated surface of PDMS decreased from 105 to 22 degree and the atomic ratio of O/Si was 1.7 times higher than that of the untreated PDMS.

  7. Novel anti-flooding poly(dimethylsiloxane) (PDMS) catalyst binder for microbial fuel cell cathodes

    KAUST Repository

    Zhang, Fang


    Poly(dimethylsiloxane) (PDMS) was investigated as an alternative to Nafion as an air cathode catalyst binder in microbial fuel cells (MFCs). Cathodes were constructed around either stainless steel (SS) mesh or copper mesh using PDMS as both catalyst binder and diffusion layer, and compared to cathodes of the same structure having a Nafion binder. With PDMS binder, copper mesh cathodes produced a maximum power of 1710 ± 1 mW m -2, while SS mesh had a slightly lower power of 1680 ± 12 mW m -2, with both values comparable to those obtained with Nafion binder. Cathodes with PDMS binder had stable power production of 1510 ± 22 mW m -2 (copper) and 1480 ± 56 mW m -2 (SS) over 15 days at cycle 15, compared to a 40% decrease in power with the Nafion binder. Cathodes with the PDMS binder had lower total cathode impedance than those with Nafion. This is due to a large decrease in diffusion resistance, because hydrophobic PDMS effectively prevented catalyst sites from filling up with water, improving oxygen mass transfer. The cost of PDMS is only 0.23% of that of Nafion. These results showed that PDMS is a very effective and low-cost alternative to Nafion binder that will be useful for large scale construction of these cathodes for MFC applications. © 2012 Elsevier B.V.

  8. Internal Structure of Einstein-Yang-Mills Black Holes


    Donets, E. E.; Gal'tsov, D. V.; Zotov, M. Yu.


    It is shown that a generic black hole solution of the SU(2) Einstein-Yang-Mills equations develops a new type of an infinitely oscillating behavior near the singularity. Only for certain discrete values of the event horizon radius exceptional solutions exist, possessing an inner structure of the Schwarzschild or Reissner-Nordstrom type.

  9. Internal Structure of Einstein-Yang-Mills Black Holes

    CERN Document Server

    Donets, E E; Zotov, M Yu


    Interior solutions for the SU(2) Einstein-Yang-Mills black holes are investigated. It is found that generically the metric does not possess inner Cauchy horizons and infinitely oscillates near the singularity. However, for certain discrete radii of the event horizon exceptional solutions exist with an inner structure of the Schwarzschild (n=1) or Reissner--Nordstrom (n=2,3,...) type.

  10. The causal structure of dynamical charged black holes

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sungwook E; Hwang, Dong-il; Stewart, Ewan D; Yeom, Dong-han, E-mail:, E-mail:, E-mail: [Department of Physics, KAIST, Daejeon 305-701 (Korea, Republic of)


    We study the causal structure of dynamical charged black holes, with a sufficient number of massless fields, using numerical simulations. Neglecting Hawking radiation, the inner horizon is a null Cauchy horizon and a curvature singularity due to mass inflation. When we include Hawking radiation, the inner horizon becomes space-like and is separated from the Cauchy horizon, which is parallel to the out-going null direction. Since a charged black hole must eventually transit to a neutral black hole, we studied the neutralization of the black hole and observed that the inner horizon evolves into a space-like singularity, generating a Cauchy horizon which is parallel to the in-going null direction. Since the mass function is finite around the inner horizon, the inner horizon is regular and penetrable in a general relativistic sense. However, since the curvature functions become trans-Planckian, we cannot say more about the region beyond the inner horizon, and it is natural to say that there is a 'physical' space-like singularity. However, if we assume an exponentially large number of massless scalar fields, our results can be extended beyond the inner horizon. In this case, strong cosmic censorship and black hole complementarity can be violated.

  11. Encapsulated PDMS microspheres with reactive handles

    DEFF Research Database (Denmark)

    Gonzalez, Lidia; Ma, Baoguang; Li, Li


    , cured PDMS microspheres are coated with poly(methyl methacrylate) using a chemical process (solvent evaporation technique). Three solvents are used in three different experiments: dichloromethane, tetrahydrofuran, and acetone. The composition and morphology of the cured PDMS microspheres and PMMA coated...

  12. Optical waveguides using PDMS-metal oxide hybrid nanocomposites (United States)

    Hosseinzadeh, Arash; Middlebrook, Christopher T.; Mullins, Michael E.


    Development of passive and active polymer based optical materials for high data rate waveguide routing and interconnects has gained increased attention because of their excellent properties such as low absorption, cost savings, and ease in fabrication. However, optical polymers are typically limited in the range of their refraction indices. Combining polymeric and inorganic optical materials provides advantages for as development of nano-composites with higher refractive indices with the possibility of being used as an active optical component. In this paper a new composite material is proposed based on polymer-metal oxide nano-composites for use as optical wave guiding structures and components. PDMS (Polydimethylsiloxane) is utilized for the polymer portion while the inorganic material is titanium dioxide. Refraction indices as high as 1.74 have been reported using these composites. For PDMS-TiO2 hybrids, the higher the ratio of titanium dioxide to PDMS, the higher the resulting refractive index. The index of refraction as a function of the PDMS:TiO2 ratio is reported with an emphasis on use as optical waveguide devices. Absorption spectrum of the nano-composites is measured showing low absorption at 850 nm and high absorption in the UV regime for direct UV laser/light curing. Prototype multimode waveguides are fabricated using soft imprint embossing that is compatible with the low viscosity nano-composite material. Cross dimensional shape and profile show the potential for full scale development utilizing the material set.

  13. Near horizon structure of extremal vanishing horizon black holes

    Directory of Open Access Journals (Sweden)

    S. Sadeghian


    Full Text Available We study the near horizon structure of Extremal Vanishing Horizon (EVH black holes, extremal black holes with vanishing horizon area with a vanishing one-cycle on the horizon. We construct the most general near horizon EVH and near-EVH ansatz for the metric and other fields, like dilaton and gauge fields which may be present in the theory. We prove that (1 the near horizon EVH geometry for generic gravity theory in generic dimension has a three dimensional maximally symmetric subspace; (2 if the matter fields of the theory satisfy strong energy condition either this 3d part is AdS3, or the solution is a direct product of a locally 3d flat space and a d−3 dimensional part; (3 these results extend to the near horizon geometry of near-EVH black holes, for which the AdS3 part is replaced with BTZ geometry. We present some specific near horizon EVH geometries in 3, 4 and 5 dimensions for which there is a classification. We also briefly discuss implications of these generic results for generic (gauged supergravity theories and also for the thermodynamics of near-EVH black holes and the EVH/CFT proposal.

  14. A new polydimethylsiloxane (PDMS) microcantilever with integrated optical waveguide for biosensing application (United States)

    Sanati Nezhad, A.; Ghanbari, M.; Agudelo, C. G.; Packirisamy, M.; Bhat, R.


    This paper reports a novel biosensor monolithically integrate optical waveguide into PDMS microcantilever. The sensor consists of buried optical fibers, integrated optical waveguide and horizontal PDMS microcantilever suspended into microfluidic channel. The thin PDMS layer involves microcantilever, microfluidic cannels and optical channels fabricated using soft lithography technique. The thin layer is covered by semi-bonding of a glass slide and a PDMS layer to enable introducing the material of waveguide core into the waveguide channel embedded into PDMS microcantilever. The covering layers are then replaced by other PDMS layers which have hollow features to release the microcantilever for free deflection and to seal microfluidic network. The input and output multimode fibers are horizontally inserted into the optical channels. The light received at the input fiber is conducted through the optical waveguide microcantilever and is delivered to the output fiber. Numerical model is presented to simulate the optical performance of the optical waveguide PDMS microcantilever under fluid flow testing and to find the proper dimensions and waveguide material. The deflection of microcantilever under flow loading distorts the light and causes power loss at the output fiber. COMSOL Multiphysics 3.5 is used to perform fluid structure interaction analysis to assess the cantilever defection due to fluid flow and the optical simulation to estimate the power loss due to cantilever deflection. The proposed biosensor can be used to measure the force within the range of living cell growth force and to be integrated within bio-sensing microdevices to carefully measure the fluid flow rate.

  15. Plasma-Based Surface Modification of Polydimethylsiloxane for PDMS-PDMS Molding


    Lopera, S.; Mansano, R. D.


    We present and compare two processes for plasma-based surface modification of Polydimethylsiloxane (PDMS) to achieve the antisticking behavior needed for PDMS-PDMS molding. The studied processes were oxygen plasma activation for vapor phase silanization and plasma polymerization with tetrafluoromethane/hydrogen mixtures under different processing conditions. We analyzed topography changes of the treated surfaces by atomic force microscopy and contact angle measurements. Plasma treatment were ...

  16. Femtosecond laser induced microripple on PDMS surface

    Institute of Scientific and Technical Information of China (English)

    Jin Xie; Changhe Zhou; Wei Wang; Tengfei Wu


    laser pulses and the subsequent cool-down solidification of the melting PDMS along with the movement of the femtosecond laser spot. This result will be helpful to understand the interaction between the femtosecond laser and the polymer.

  17. Dynamical structure of magnetized dissipative accretion flow around black holes

    CERN Document Server

    Sarkar, Biplob


    We study the global structure of optically thin, advection dominated, magnetized accretion flow around black holes. We consider the magnetic field to be turbulent in nature and dominated by the toroidal component. With this, we obtain the complete set of accretion solutions for dissipative flows where bremsstrahlung process is regarded as the dominant cooling mechanism. We show that rotating magnetized accretion flow experiences virtual barrier around black hole due to centrifugal repulsion that can trigger the discontinuous transition of the flow variables in the form of shock waves. We examine the properties of the shock waves and find that the dynamics of the post-shock corona (PSC) is controlled by the flow parameters, namely viscosity, cooling rate and strength of the magnetic field, respectively. We separate the effective region of the parameter space for standing shock and observe that shock can form for wide range of flow parameters. We obtain the critical viscosity parameter that allows global accret...

  18. Dynamical structure of magnetized dissipative accretion flow around black holes (United States)

    Sarkar, Biplob; Das, Santabrata


    We study the global structure of optically thin, advection dominated, magnetized accretion flow around black holes. We consider the magnetic field to be turbulent in nature and dominated by the toroidal component. With this, we obtain the complete set of accretion solutions for dissipative flows where bremsstrahlung process is regarded as the dominant cooling mechanism. We show that rotating magnetized accretion flow experiences virtual barrier around black hole due to centrifugal repulsion that can trigger the discontinuous transition of the flow variables in the form of shock waves. We examine the properties of the shock waves and find that the dynamics of the post-shock corona (PSC) is controlled by the flow parameters, namely viscosity, cooling rate and strength of the magnetic field, respectively. We separate the effective region of the parameter space for standing shock and observe that shock can form for wide range of flow parameters. We obtain the critical viscosity parameter that allows global accretion solutions including shocks. We estimate the energy dissipation at the PSC from where a part of the accreting matter can deflect as outflows and jets. We compare the maximum energy that could be extracted from the PSC and the observed radio luminosity values for several supermassive black hole sources and the observational implications of our present analysis are discussed.

  19. Low cost fabrication of polymer composite (h-ZnO + PDMS) material for piezoelectric device application (United States)

    Singh, Akanksha; Das, Sonatan; Bharathkumar, Mareddi; Revanth, D.; Karthik, ARB; Sudhakara Sastry, Bala; Ramgopal Rao, V.


    Flexible piezoelectric composites offer alternative and/or additional solutions to sensor, actuator and transducer applications. Here in this work, we have successfully fabricated highly flexible piezoelectric composites with poly dimethyl siloxane (PDMS) using herbal zinc oxide (h-ZnO) as filler having weight fractions up to 50 wt.% by solution casting of dispersions of h-ZnO in PDMS. Excellent piezo properties (Resonant frequency 935 Hz, d*33 29.76 pm V-1), physiochemical properties (Wurtzite structure ZnO, 380 nm absorbance) and mechanical properties (Young modulus 16.9 MPa) have been optimized with theoretical simulations and observed experimentally for h-ZnO + PDMS. As such, the demonstrated piezoelectric PDMS membranes combined with the excellent properties of these composites open new ways to ‘soft touch’ applications and could serve as a variety of soft and sensitive electromechanical transducers, which are desired for a variety of sensor and energy harvesting applications.

  20. Synthesis and characterization of fluorinated PEO-b-PDMS-b-fluorinated PEO by free radical addition

    Institute of Scientific and Technical Information of China (English)

    Wei Hu Li; Xing Yuan Zhang; Jia Bing Dai


    Fluorinated poly(ethylene oxide)propyl-b-polydimethylsiloxane-b-propyl fluorinated poly(ethylene oxide)(FPEO-b-PDMS-b-FPEO)was synthesized by a free radical addition of carbon-hydrogen of polyether segments of poly(ethylene oxide)propyl-b-polydimethylsiloxane-b-propyl poly(ethylene oxide)(PEO-b-PDMS-b-PEO)to hexafluoropropylene(HFP)using rert-butyl peroxypivalate as an initiator.In order to reduce the possibility of side reaction,the protection and deprotection via silylation were used for the end-hydroxyls in PEO-b-PDMS-b-PEO chain.The structure of Intermediates and FPEO-b-PDMS-b-FPEO was confirmed by means of Fourier transform infrared and 1H NMR spectroscopy.The effects of amount of initiator,reaction temperature and time on free radical addition were investigated in detail.

  1. Study of Different Sol-Gel Coatings to Enhance the Lifetime of PDMS Devices: Evaluation of Their Biocompatibility

    Directory of Open Access Journals (Sweden)

    María Aymerich


    Full Text Available A study of PDMS (polydimethylsiloxane sol-gel–coated channels fabricated using soft lithography and a laser direct writing technique is presented. PDMS is a biocompatible material that presents a high versatility to reproduce several structures. It is widely employed in the fabrication of preclinical devices due to its advantages but it presents a rapid chemical deterioration to organic solvents. The use of sol-gel layers to cover the PDMS overcomes this problem since it provides the robustness of glass for the structures made with PDMS, decreasing its deterioration and changing the biocompatibility of the surface. In this work, PDMS channels are coated with three different kinds of sol-gel compositions (60MTES/40TEOS, 70MTES/30TISP and 80MTES/20TISP. The endothelial cell adhesion to the different coated devices is evaluated in order to determine the most suitable sol-gel preparation conditions to enhance cellular adhesion.

  2. Hawking Radiation as a Possible Probe for the Interior Structure of Regular Black Holes (United States)

    Deng, Yanbin; Cleaver, Gerald


    The notion of black hole singularity and the proof of the singularity theorem were considered great successes in classical general relativity whereas they meanwhile brought with deep puzzles. Conceptual challenges were set up by the intractability of the singularity. The existence of black hole horizons which cover up the black hole interior including the singularity from outside observers, builds an information curtain, further hindering physicists from understanding the nature of the singularity and the interior structure of black holes. The regular black hole is a concept produced out of multiple attempts of establishing a tractable and understandable interior structure for black holes as well as avoiding the singularity behind the black hole horizon. The practicality of the new constructions of black holes would be considered more reliable if there can be found some connection between the interior of regular black holes and some far-reaching signals released from the black hole. After studying the Hawking radiation by fermion tunnelling from one type of regular black hole, structure dependent results were obtained. The result being structure dependent hints the prospects of employing the Hawking radiation as a method to probe into the structure of black holes.

  3. Rapid fabrication of microfluidic PDMS devices from reusable PDMS molds using laser ablation (United States)

    Isiksacan, Ziya; Tahsin Guler, M.; Aydogdu, Berkan; Bilican, Ismail; Elbuken, Caglar


    The conventional fabrication methods for microfluidic devices require cleanroom processes that are costly and time-consuming. We present a novel, facile, and low-cost method for rapid fabrication of polydimethylsiloxane (PDMS) molds and devices. The method consists of three main fabrication steps: female mold (FM), male mold (MM), and chip fabrication. We use a CO2 laser cutter to pattern a thin, spin-coated PDMS layer for FM fabrication. We then obtain reusable PDMS MM from the FM using PDMS/PDMS casting. Finally, a second casting step is used to replicate PDMS devices from the MM. Demolding of one PDMS layer from another is carried out without any potentially hazardous chemical surface treatment. We have successfully demonstrated that this novel method allows fabrication of microfluidic molds and devices with precise dimensions (thickness, width, length) using a single material, PDMS, which is very common across microfluidic laboratories. The whole process, from idea to device testing, can be completed in 1.5 h in a standard laboratory.

  4. Handcrafted multilayer PDMS microchannel scaffolds for peripheral nerve regeneration. (United States)

    Hossain, Ridwan; Kim, Bongkyun; Pankratz, Rachel; Ajam, Ali; Park, Sungreol; Biswal, Sibani L; Choi, Yoonsu


    Injuries that result in the loss of limb functionality may be caused by the severing of the peripheral nerves within the affected limb. Several bioengineered peripheral nerve scaffolds have been developed in order to provide the physical support and topographical guidance necessary for the naturally disorganized axon outgrowth to reattach to distal nerve stumps as an alternative to other procedures, like nerve grafting. PDMS has been chosen for the base material of the scaffolds due to its biocompatibility, flexibility, transparency, and well-developed fabrication techniques. The process of observing the axon outgrowth across the nerve gaps with PDMS scaffolds has been challenging due to the limited number and fineness of longitudinal sections that can be extracted from harvested nerve tissue samples after implantation. To address this, multilayer microchannel scaffolds were developed with the object of providing more refined longitudinal observation of axon outgrowth by longitudinally 'sectioning' the device during fabrication, removing the need for much of the sample preparation process. This device was then implanted into the sciatic nerves of Lewis rats, and then harvested after two and four weeks to analyze the difference in nerve regeneration between two different time periods. The present layer by layer structure, which is separable after nerve regeneration and is treated as an individual layer during the histology process, provides the details of biological events during axonal regeneration. Confocal microscopic imaging showed the details of peripheral nerve regeneration including nerve branches and growth cones observable from within the microchannels of the multilayer PDMS microchannel scaffolds.

  5. 3D Printing PDMS Elastomer in a Hydrophilic Support Bath via Freeform Reversible Embedding (United States)


    Polydimethylsiloxane (PDMS) elastomer is used in a wide range of biomaterial applications including microfluidics, cell culture substrates, flexible electronics, and medical devices. However, it has proved challenging to 3D print PDMS in complex structures due to its low elastic modulus and need for support during the printing process. Here we demonstrate the 3D printing of hydrophobic PDMS prepolymer resins within a hydrophilic Carbopol gel support via freeform reversible embedding (FRE). In the FRE printing process, the Carbopol support acts as a Bingham plastic that yields and fluidizes when the syringe tip of the 3D printer moves through it, but acts as a solid for the PDMS extruded within it. This, in combination with the immiscibility of hydrophobic PDMS in the hydrophilic Carbopol, confines the PDMS prepolymer within the support for curing times up to 72 h while maintaining dimensional stability. After printing and curing, the Carbopol support gel releases the embedded PDMS prints by using phosphate buffered saline solution to reduce the Carbopol yield stress. As proof-of-concept, we used Sylgard 184 PDMS to 3D print linear and helical filaments via continuous extrusion and cylindrical and helical tubes via layer-by-layer fabrication. Importantly, we show that the 3D printed tubes were manifold and perfusable. The results demonstrate that hydrophobic polymers with low viscosity and long cure times can be 3D printed using a hydrophilic support, expanding the range of biomaterials that can be used in additive manufacturing. Further, by implementing the technology using low cost open-source hardware and software tools, the FRE printing technique can be rapidly implemented for research applications.

  6. 3D Printing PDMS Elastomer in a Hydrophilic Support Bath via Freeform Reversible Embedding. (United States)

    Hinton, Thomas J; Hudson, Andrew; Pusch, Kira; Lee, Andrew; Feinberg, Adam W


    Polydimethylsiloxane (PDMS) elastomer is used in a wide range of biomaterial applications including microfluidics, cell culture substrates, flexible electronics, and medical devices. However, it has proved challenging to 3D print PDMS in complex structures due to its low elastic modulus and need for support during the printing process. Here we demonstrate the 3D printing of hydrophobic PDMS prepolymer resins within a hydrophilic Carbopol gel support via freeform reversible embedding (FRE). In the FRE printing process, the Carbopol support acts as a Bingham plastic that yields and fluidizes when the syringe tip of the 3D printer moves through it, but acts as a solid for the PDMS extruded within it. This, in combination with the immiscibility of hydrophobic PDMS in the hydrophilic Carbopol, confines the PDMS prepolymer within the support for curing times up to 72 h while maintaining dimensional stability. After printing and curing, the Carbopol support gel releases the embedded PDMS prints by using phosphate buffered saline solution to reduce the Carbopol yield stress. As proof-of-concept, we used Sylgard 184 PDMS to 3D print linear and helical filaments via continuous extrusion and cylindrical and helical tubes via layer-by-layer fabrication. Importantly, we show that the 3D printed tubes were manifold and perfusable. The results demonstrate that hydrophobic polymers with low viscosity and long cure times can be 3D printed using a hydrophilic support, expanding the range of biomaterials that can be used in additive manufacturing. Further, by implementing the technology using low cost open-source hardware and software tools, the FRE printing technique can be rapidly implemented for research applications.

  7. PDMS/PVDF hybrid electrospun membrane with superhydrophobic property and drop impact dynamics for dyeing wastewater treatment using membrane distillation

    KAUST Repository

    An, Alicia Kyoungjin


    Fouling in membrane distillation (MD) results in an increase in operation costs and deterioration in a water quality. In this work, a poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP) electrospun (E-PH) membrane was fabricated by hybridizing polydimethylsiloxane (PDMS) polymeric microspheres with superhydrophobicity onto the E-PH membrane via electrospinning. The resulting hybrid PDMS with E-PH (E-PDMS) membrane showed a significant enhancement in surface hydrophobicity (contact angle, CA = 155.4°) and roughness (Ra = 1,285mm). The zeta potential of E-PDMS membrane surface showed a higher negative value than that of a commercial PVDF (C-PVDF) membrane. These properties of E-PDMS membrane provided an antifouling in treating of differently-charged dyes and generated a flake-like dye–dye (loosely bound foulant) structure on the membrane surface rather than in the membrane pores. This also led to a high productivity of E-PDMS membrane (34 Lm-2h-1, 50% higher than that of C-PVDF membrane) without fouling or wetting. In addition, complete color removal and pure water production were achieved during a long-term operation. An application of intermittent water flushing (WF) in direct contact MD (DCMD) operation led to a 99% CA recovery of E-PDMS membrane indicating its sustainability. Therefore, the E-PDMS membrane is a promising candidate for MD application in dyeing wastewater treatment.

  8. Black Hole Mergers as Probes of Structure Formation (United States)

    Alicea-Munoz, Emily


    Observations of gravitational waves from massive black hole (MBH) mergers can provide us with important clues about the era of structure formation in the early universe. Previous research in this field has been limited to calculating merger rates of MBHs using different models where many assumptions are made about the specific values of physical parameters of the mergers, resulting in merger rate estimates that span 5 to 6 orders of magnitude. We develop a semi-analytical, phenomenological model that includes plausible combinations of several physical parameters involved in the mergers. which we then turn around to determine how well LISA observations will be able to enhance our understanding of the universe during the critical z approximately equal to 5-30 structure formation era. We do this by generating synthetic LISA observable data (masses, redshifts, merger rates), which are then analyzed using a Markov Chain Monte Carlo (MCMC) method. This allows us to constrain the physical parameters of the mergers.

  9. Characterization of polydimethylsiloxane (PDMS) properties for biomedical micro/nanosystems. (United States)

    Mata, Alvaro; Fleischman, Aaron J; Roy, Shuvo


    Polydimethylsiloxane (PDMS Sylgard 184, Dow Corning Corporation) pre-polymer was combined with increasing amounts of cross-linker (5.7, 10.0, 14.3, 21.4, and 42.9 wt.%) and designated PDMS1, PDMS2, PDMS3, PDMS4, and PDMS5, respectively. These materials were processed by spin coating and subjected to common micro-fabrication, micro-machining, and biomedical processes: chemical immersion, oxygen plasma treatment, sterilization, and exposure to tissue culture media. The PDMS formulations were analyzed by gravimetry, goniometry, tensile testing, nano-indentation, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Spin coating of PDMS was formulation dependent with film thickness ranging from 308 microm on PDMS1 to 171 microm on PDMS5 at 200 revolutions per minute (rpm). Ultimate tensile stress (UTS) increased from 3.9 MPa (PDMS1) to 10.8 MPa (PDMS3), and then decreased down to 4.0 MPa (PDMS5). Autoclave sterilization (AS) increased the storage modulus (sigma) and UTS in all formulations, with the highest increase in UTS exhibited by PDMS5 (218%). PDMS surface hydrophilicity and micro-textures were generally unaffected when exposed to the different chemicals, except for micro-texture changes after immersion in potassium hydroxide and buffered hydrofluoric, nitric, sulfuric, and hydrofluoric acids; and minimal changes in contact angle after immersion in hexane, hydrochloric acid, photoresist developer, and toluene. Oxygen plasma treatment decreased the contact angle of PDMS2 from 109 degrees to 60 degrees. Exposure to tissue culture media resulted in increased PDMS surface element concentrations of nitrogen and oxygen.

  10. Using Black Hole Mergers to Explore Structure Formation (United States)

    Alicea-Munoz, E.; Miller, M. Coleman


    Observations of gravitational waves from massive black hole mergers will open a new window into the era of structure formation in the early universe. Past efforts have concentrated on calculating merger rates using different physical assumptions, resulting in merger rate estimates that span a wide range (0.1 - 10(exp 4) mergers/year). We develop a semi-analytical, phenomenological model of massive black hole mergers that includes plausible combinations of several physical parameters, which we then turn around to determine how well observations with the Laser Interferometer Space Antenna (LISA) will be able to enhance our understanding of the universe during the critical z approximately equal to 5-30 epoch. Our approach involves generating synthetic LISA observable data (total BH masses, BH mass ratios, redshifts, merger rates), which are then analyzed using a Markov Chain Monte Carlo method, thus finding constraints for the physical parameters of the mergers. We find that our method works well at estimating merger parameters and that the number of merger events is a key discriminant among models, therefore making our method robust against observational uncertainties. Our approach can also be extended to more physically-driven models and more general problems in cosmology. This work is supported in part by the Cooperative Education Program at NASA/GSFC.

  11. Lens array fabrication method with volume expansion property of PDMS (United States)

    Jang, WonJae; Kim, Junoh; Lee, Muyoung; Lee, Jooho; Bang, Yousung; Won, Yong Hyub


    Conventionally, poly (dimethylsiloxane) lens array is fabricated by replica molding. In this paper, we describe simple method for fabricating lens array with expanding property of PDMS. The PDMS substrate is prepared by spin coating on cleaned glass. After spin coating PDMS, substrate is treated with O2 plasma to promote adhesion between PDMS substrate and photoresist pattern on it. Positive photoresist az-4330 and AZ 430K developer is used for patterning on PDMS. General photolithography process is used to patterning. Then patterned PDMS substrate is dipped to 1- Bromododecane bath. During this process, patterned photoresist work as a barrier and prevent blocked PDMS substrate from reaction with 1-Bromododecane. Unblocked part of PDMS directly react with 1-Bromododecane and results in expanded PDMS volume. The expansion of PDMS is depends on absorbed 1-Bromododecane volume, dipping time and ratio of block to open area. The focal length of lens array is controlled by those PDMS expansion factors. Scale of patterned photoresist determine a diameter of each lens. The expansion occurs symmetrically at center of unblocked PDMS and 1-Bromododecane interface. As a result, the PDMS lens array is achieved by this process.

  12. Stretching micropatterned cells on a PDMS membrane. (United States)

    Carpi, Nicolas; Piel, Matthieu


    Mechanical forces exerted on cells and/or tissues play a major role in numerous processes. We have developed a device to stretch cells plated on a PolyDiMethylSiloxane (PDMS) membrane, compatible with imaging. This technique is reproducible and versatile. The PDMS membrane can be micropatterned in order to confine cells or tissues to a specific geometry. The first step is to print micropatterns onto the PDMS membrane with a deep UV technique. The PDMS membrane is then mounted on a mechanical stretcher. A chamber is bound on top of the membrane with biocompatible grease to allow gliding during the stretch. The cells are seeded and allowed to spread for several hours on the micropatterns. The sample can be stretched and unstretched multiple times with the use of a micrometric screw. It takes less than a minute to apply the stretch to its full extent (around 30%). The technique presented here does not include a motorized device, which is necessary for applying repeated stretch cycles quickly and/or computer controlled stretching, but this can be implemented. Stretching of cells or tissue can be of interest for questions related to cell forces, cell response to mechanical stress or tissue morphogenesis. This video presentation will show how to avoid typical problems that might arise when doing this type of seemingly simple experiment.

  13. On Black Hole Structures in Scalar-Tensor Theories of Gravity

    CERN Document Server

    Bronnikov, Kirill A; Rodrigues, Denis C


    We review some properties of black hole structures appearing in gravity with a massless scalar field, with both minimal and nonminimal coupling. The main properties of the resulting cold black holes are described. The study of black holes in scalar-gravity systems is extended to $k$-essence theories, and some examples are explicitly worked out. In these cases, even while the existence of horizons is possible, the metric regularity requirement on the horizon implies either a cold black type structure or a singular behavior of the scalar field.

  14. Modulation of hepatocarcinoma cell morphology and activity by parylene-C coating on PDMS.

    Directory of Open Access Journals (Sweden)

    Nazaré Pereira-Rodrigues

    Full Text Available BACKGROUND: The ability to understand and locally control the morphogenesis of mammalian cells is a fundamental objective of cell and developmental biology as well as tissue engineering research. We present parylene-C (ParC deposited on polydimethylsiloxane (PDMS as a new substratum for in vitro advanced cell culture in the case of Human Hepatocarcinoma (HepG2 cells. PRINCIPAL FINDINGS: Our findings establish that the intrinsic properties of ParC-coated PDMS (ParC/PDMS influence and modulate initial extracellular matrix (ECM; here, type-I collagen surface architecture, as compared to non-coated PDMS substratum. Morphological changes induced by the presence of ParC on PDMS were shown to directly affect liver cell metabolic activity and the expression of transmembrane receptors implicated in cell adhesion and cell-cell interaction. These changes were characterized by atomic force microscopy (AFM, which elucidated differences in HepG2 cell adhesion, spreading, and reorganization into two- or three-dimensional structures by neosynthesis of ECM components. Local modulation of cell aggregation was successfully performed using ParC/PDMS micropatterns constructed by simple microfabrication. CONCLUSION/SIGNIFICANCE: We demonstrated for the first time the modulation of HepG2 cells' behavior in relation to the intrinsic physical properties of PDMS and ParC, enabling the local modulation of cell spreading in a 2D or 3D manner by simple microfabrication techniques. This work will provide promising insights into the development of cell-based platforms that have many applications in the field of in vitro liver tissue engineering, pharmacology and therapeutics.

  15. Black Holes and Quantum Theory: The Fine Structure Constant Connection

    Directory of Open Access Journals (Sweden)

    Cahill R. T.


    Full Text Available The new dynamical theory of space is further confirmed by showing that the effective “black hole” masses M BH in 19 spherical star systems, from globular clusters to galaxies, with masses M , satisfy the prediction that M BH = α 2 M , where α is the fine structure constant. As well the necessary and unique generalisations of the Schr ̈ odinger and Dirac equations permit the first derivation of gravity from a deeper theory, showing that gravity is a quantum effect of quantum matter interacting with the dynamical space. As well the necessary generalisation of Maxwell’s equations displays the observed light bending effects. Finally it is shown from the generalised Dirac equation where the spacetime mathematical formalism, and the accompanying geodesic prescription for matter trajectories, comes from. The new theory of space is non-local and we see many parallels between this and quantum theory, in addition to the fine structure constant manifesting in both, so supporting the argument that space is a quantum foam system, as implied by the deeper information-theoretic theory known as Process Physics. The spatial dynamics also provides an explanation for the “dark matter” effect and as well the non-locality of the dynamics provides a mechanism for generating the uniformity of the universe, so explaining the cosmological horizon problem.

  16. Sub-15nm Silicon Lines Fabrication via PS-b-PDMS Block Copolymer Lithography

    DEFF Research Database (Denmark)

    Rasappa, Sozaraj; Schulte, Lars; Borah, Dipu


    This paper describes the fabrication of nanodimensioned silicon structures on silicon wafers from thin films of a poly(styrene)-block-poly(dimethylsiloxane) (PS-b-PDMS) block copolymer (BCP) precursor self-assembling into cylindrical morphology in the bulk. The structure alignment of the PS......-b-PDMS (33 k–17 k) was conditioned by applying solvent and solvothermal annealing techniques. BCP nanopatterns formed after the annealing process have been confirmed by scanning electron microscope (SEM) after removal of upper PDMS wetting layer by plasma etching. Silicon nanostructures were obtained...... by subsequent plasma etching to the underlying substrate by an anisotropic dry etching process. SEM images reveal the formation of silicon nanostructures, notably of sub-15nm dimensions....

  17. A Versatile Bonding Method for PDMS and SU-8 and Its Application towards a Multifunctional Microfluidic Device

    Directory of Open Access Journals (Sweden)

    Zhen Zhu


    Full Text Available This paper reports a versatile and irreversible bonding method for poly(dimethylsiloxane (PDMS and SU-8. The method is based on epoxide opening and dehydration reactions between surface-modified PDMS and SU-8. A PDMS replica is first activated via the low-cost lab equipment, i.e., the oxygen plasma cleaner or the corona treater. Then both SU-8 and plasma-treated PDMS samples are functionalized using hydrolyzed (3-aminopropyltriethoxysilane (APTES. Ultimately, the samples are simply brought into contact and heated to enable covalent bonding. The molecular coupling and chemical reactions behind the bonding occurring at the surfaces were characterized by water contact angle measurement and X-ray photoelectron spectroscopy (XPS analysis. The reliability of bonded PDMS-SU-8 samples was examined by using tensile strength and leakage tests, which revealed a bonding strength of over 1.4 MPa. The presented bonding method was also applied to create a metal-SU-8-PDMS hybrid device, which integrated SU-8 microfluidic structures and microelectrodes. This hybrid system was used for the effective trapping of microparticles on-chip, and the selective releasing and identification of predefined trapped microparticles. The hybrid fabrication approach presented here, based on the PDMS-SU-8 bonding, enables multifunctional integration in complex microfluidic devices.

  18. Black Hole Mergers as Probes of Structure Formation (United States)

    Alicea-Munoz, E.; Miller, M. Coleman


    Intense structure formation and reionization occur at high redshift, yet there is currently little observational information about this very important epoch. Observations of gravitational waves from massive black hole (MBH) mergers can provide us with important clues about the formation of structures in the early universe. Past efforts have been limited to calculating merger rates using different models in which many assumptions are made about the specific values of physical parameters of the mergers, resulting in merger rate estimates that span a very wide range (0.1 - 104 mergers/year). Here we develop a semi-analytical, phenomenological model of MBH mergers that includes plausible combinations of several physical parameters, which we then turn around to determine how well observations with the Laser Interferometer Space Antenna (LISA) will be able to enhance our understanding of the universe during the critical z 5 - 30 structure formation era. We do this by generating synthetic LISA observable data (total BH mass, BH mass ratio, redshift, merger rates), which are then analyzed using a Markov Chain Monte Carlo method. This allows us to constrain the physical parameters of the mergers. We find that our methodology works well at estimating merger parameters, consistently giving results within 1- of the input parameter values. We also discover that the number of merger events is a key discriminant among models. This helps our method be robust against observational uncertainties. Our approach, which at this stage constitutes a proof of principle, can be readily extended to physical models and to more general problems in cosmology and gravitational wave astrophysics.

  19. Synthesis and characterization of a novel hydroxypolyether blocked polydimethylsiloxane PEO-b-PDMS-b-PEO

    Institute of Scientific and Technical Information of China (English)

    Wei Hu Li; Xing Yuan Zhang; Jia Bing Dai


    A novel hydroxypolyether blocked polydimethylsiloxane,poly(ethylene oxide)propyl-b-polydimethylsiloxane-b-propyl poly(ethylene oxide)(PEO-b=PDMS-b-PEO)was synthesized by simple hydrosilation reaction of poly(ethylene glycol)monoallyl ether with α,ω-dihydrogen terminated PDMS(HPDMS).Fourier transform infrared spectroscopy(FTIR)and 1H NMR were used to identify the structure of PEO-b-PDMS-b-PEO and intermediate product HPDMS.Based on the effect investigations of temperature.reactant molar ratio,catalyst and time on the hydrosilation,it Was found that the conversion of Si-H bond to Si-C bond increased with the increase of catalyst and time,and the reaction completed when the content of catalyst Was 22 μg/g and the time Was 5 h,respectively.Urethane reaction of OH and NCO group confirms that PEO-b-PDMS-b-PEO is more reactive toward to diisocyanate than α,ω-dihydroxylbutyl terminated PDMS.

  20. Fabrication of TEOS/PDMS/F127 hybrid coating materials for conservation of historic stone sculptures (United States)

    Liu, Yurong; Liu, Jia


    The present work was aimed to develop a new kind of stone conservation materials (TEOS/PDMS/F127 hybrid coating) by a facile sol-gel method for the protection of decayed sandstones of Chongqing Dazu stone sculptures in China. The hydrophobic property, surface morphology, water vapor permeability, ultraviolet aging resistance and mechanical properties were measured to evaluate the effectiveness of TEOS/PDMS/F127 hybrid coating as a stone conservation material. The results showed that the addition of hydroxyl-terminated polydimethylsiloxane (PDMS-OH) contributed to improve the hydrophobic properties and incorporation of PEO-PPO-PEO (F127) surfactant resulted in the formation of superficial protrusions with micro- and nanoscopic structures and overall alteration of surface morphology and roughness, thus preventing the coating materials from cracking. After treatment with TEOS/PDMS/F127 hybrid coating materials, the ultraviolet aging resistance and mechanical properties of stone were also improved without the obvious effects on the breathability and color of the stone, indicating promising applications of TEOS/PDMS/F127 hybrid coating materials for conservation of historic stone sculptures.

  1. Cold Scalar-Tensor Black Holes Causal Structure, Geodesics, Stability

    CERN Document Server

    Bronnikov, K A; Constantinidis, C P; Fabris, J C


    We study the structure and stability of spherically symmetric Brans-Dicke black-hole type solutions with an infinite horizon area and zero Hawking temperature, existing for negative values of the coupling constant $\\omega$. These solutions split into two classes, depending on finite (B1) or infinite (B2) proper time needed for an infalling particle to reach the horizon. Class B1 metrics can be extended through the horizon only for discrete values of mass and scalar charge, depending on two integers m and n. For even m-n, the space-time is globally regular; for odd m, the metric changes its signature on the horizon but remains Lorentzian. Geodesics are smoothly continued across the horizon, but for odd m timelike geodesics become spacelike and vice versa. Causality problems, arising in some cases, are discussed. Tidal forces are shown to grow infinitely near type B1 horizons. All vacuum static, spherically symmetric solutions of the Brans-Dicke theory with $\\omega<-3/2$ are found to be linearly stable again...

  2. Internal Structure of Charged AdS Black Holes

    CERN Document Server

    Bhattacharjee, Srijit; Virmani, Amitabh


    When an electrically charged black hole is perturbed its inner horizon becomes a singularity, often referred to as the Poisson-Israel mass inflation singularity. Ori constructed a model of this phenomenon for asymptotically flat black holes, in which the metric can be determined explicitly in the mass inflation region. In this paper we implement the Ori model for charged AdS black holes. We find that the mass function inflates faster than the flat space case as the inner horizon is approached. Nevertheless, the mass inflation singularity is still a weak singularity: although spacetime curvature becomes infinite, tidal distortions remain finite on physical objects attempting to cross it.


    Institute of Scientific and Technical Information of China (English)

    QIU Yongxing; YU Xiaojie; FENG Lingxian


    A new reactive graft copolymer, poly (dimethyl siloxane)-graft-ω-hydroxyl-poly (ethylene oxide) (PDMS-g-(PEO-OH)), was synthesized by the hydrosilylation reaction of α, ω-bifunctional PEO macromonomer (CH2=CH-CH2-PEO-OH) with poly (hydromethylsiloxane) (PHMS). The obtained copolymer, exhibited the expected comblike structure as indicated by the result of detailed characterization and the needed reactivity as demonstrated by the result of esterification between PDMS-g-(PEO-OH)and aminoacetic acid. This reactive graft copolymer is expected to be very useful in the preparation of new bioactive polymer materials.

  4. Preparation and evaluation of the bioinspired PS/PDMS photochromic films by the self-assembly dip-drawing method. (United States)

    Shieh, Jen-Yu; Kuo, Jen-Yu; Weng, Hsueh-Ping; Yu, Hsin Her


    Emulsifier-free emulsion polymerization was employed to synthesize polystyrene (PS) microspheres, which were then self-assembled into an ordered periodic structure. A photochromic film was formed by adding polydimethylsiloxane (PDMS) around the self-assembly of PS microspheres on a PDMS substrate. During polymerization, the PS microspheres shrunk depending on the amount of the hydrophilic comonomer, sodium 4-styrenesulfonate (NaSS). Variation in structural color was strongly affected by the size of the PS microspheres. Scanning electron microscopy was used to observe the surface and cross sections of the self-assembled microspheres. Results showed that the order and stacking thickness of microspheres were dependent on the drawing rate of the substrate and suspension concentration. High-transmittance photochromic films could be prepared when the drawing rate was lower than 1 μm/s and the suspension concentration was 20 wt %. PDMS surrounding the vacant space between regularly arranged PS microspheres could not only protect them but also increase the degree of matching between the refractive indices of PS and PDMS. The stability of the reflected structural color increased, and the optical transmittance of the photochromic film approached 95% after PDMS was poured between the PS microspheres. A special pattern could be designed and embedded inside the photochromic film. The PS/PDMS photochromic films can also be applied in decorative painting as well as in security devices, color-changing false nails, and privacy filters.

  5. Rapid prototyping of microstructures in polydimethylsiloxane (PDMS) by direct UV-lithography

    NARCIS (Netherlands)

    Scharnweber, Tim; Truckenmüller, Roman; Schneider, Andrea M.; Welle, Alexander; Reinhardt, Martina; Giselbrecht, Stefan


    Microstructuring of polydimethylsiloxane (PDMS) is a key step for many lab-on-a-chip (LOC) applications. In general, the structure is generated by casting the liquid prepolymer against a master. The production of the master in turn calls for special equipment and know how. Furthermore, a given maste

  6. Structurally Coloured Secondary Particles Composed of Black and White Colloidal Particles



    This study investigated the colourful secondary particles formed by controlling the aggregation states of colloidal silica particles and the enhancement of the structural colouration of the secondary particles caused by adding black particles. We obtained glossy, partially structurally coloured secondary particles in the absence of NaCl, but matte, whitish secondary particles were obtained in the presence of NaCl. When a small amount of carbon black was incorporated into both types of seconda...

  7. Electrically tunable, optical microcavity based on metallized and ultra-soft PDMS gel (United States)

    Franke, M.; Slowik, I.; Paschew, G.; Merkel, U.; Fröb, H.; Leo, K.; Richter, A.


    Tunable, optical microcavities (MC) gain more and more importance for display, laser or other optical applications. The setup of dielectric elastomer actuators (DEA) enables a simple integration of an optical cavity, since reflective electrodes can confine a cavity that is filled with a transparent elastomer. Applying a voltage to the electrodes leads to squeezing of the elastomer and, due to the cavity thickness decrease, the resonator modes of interfering light changes. In this work we present an electrically tunable, optical MC based on ultra-soft poly(dimethylsiloxane) (PDMS). The PDMS gel is coated on a glass substrate with a distributed Bragg reflector, an ITO bottom electrode and a flexible, highly reflective metal electrode and mirror on top. The usage of an ultra-soft PDMS gel, with a storage modulus of about 1kPa, allows to decrease the operating voltage down to a few hundred or even several ten volts. The critical step of fabrication is the metallization of the PDMS gel layer that requires a previous oxidizing surface activation to gain reflective and conductive silver based layers on top. Therefore, the effects of oxygen plasma and UV/ozone treatment on PDMS and the created metal layer were investigated intensively. The performance of the electrically tunable, optical MC is tremendously dependent from an adequate surface activation and structuring of the top electrodes considering the mirror displacement and activation voltage. Here we could show that tunable MCs based on oxygen plasma activated PDMS show a homogenous and high thickness decrease up to 70% at 200V.

  8. PDMS/PVA composite ferroelectret for improved energy harvesting performance (United States)

    Shi, J.; Luo, Z.; Zhu, D.; Beeby, S. P.


    This paper address the PDMS ferroelectret discharge issue for improved long- term energy harvesting performance. The PDMS/PVA ferroelectret is fabricated using a 3D-printed plastic mould technology and a functional PVA composite layer is introduced. The PDMS/PVA composite ferroelectret achieved 80% piezoelectric coefficient d33 remaining, compared with 40% without the proposed layer over 72 hours. Further, the retained percentage of output voltage is about 73% over 72 hours.

  9. Near-Horizon Conformal Structure of Black Holes

    CERN Document Server

    Birmingham, Daniel; Sen, S; Birmingham, Danny; Gupta, Kumar S.; Sen, Siddhartha


    The near-horizon properties of a black hole are studied within an algebraic framework, using a scalar field as a simple probe to analyze the geometry. The operator H governing the near-horizon dynamics of the scalar field contains an inverse square interaction term. It is shown that the operators appearing in the corresponding algebraic description belong to the representation space of the Virasoro algebra. The operator H is studied using the representation theory of the Virasoro algebra. We observe that the wave functions exhibit scaling behaviour in a band-like region near the horizon of the black hole.

  10. PDMS气动微泵的研制%Development of a PDMS Pneumatic Peristaltic Micropump

    Institute of Scientific and Technical Information of China (English)

    关艳霞; 凌宇


    聚二甲聚硅氧烷(PDMS)气动微泵具有结构简单、易于制作、造价低和易于集成的特点.对微泵的结构进行了分析、设计与制作,较详细地讨论了关键制作工艺,并对影响流速的主要因素进行了分析,通过对结构参数的优化,使微泵的最大流速达到0.55μL/min,较相关文献中的微泵的流速提高4倍,使微泵更具有实用性.%A PDMS pneumatic peristaltic micropump has features of simplicity in structures and fabricating technique,fast in replication,low in cost,easy in integrating with other microfluidic component. In this paper,the development of a PDMS pneumatic peristaltic micropump has been done by analyzing the structure of a PDMS pneumatic peristaltic micropump, and the key process and the main factors affecting velocity have been discussed. By optimizing the structural parameters of the pump,the flow rate has been to 0. 55 μL/min,5 times of the flow rate of the micopump reported in the related literature,and that make it more practical.

  11. Micromolded U-shaped PDMS optical waveguide for biosensing applications (United States)

    Punjabi, Nirmal; Khatri, Anjali; Mukherji, Soumyo


    Integrated optical waveguide sensors are usually fabricated using materials like silicon, silica, SU-8, etc. Their fabrication requires clean room processes which are expensive and time-consuming. We demonstrated the fabrication of PDMS based optical waveguide in non-cleanroom environment using soft lithography technique. A master-mold was fabricated using Acralyn. PDMS polymer was chosen for waveguide fabrication, as it provides low refractive index contrast in the sensing region. These PDMS waveguides were found to be 5-times more sensitive than SU-8 waveguides. High sensitivity along with mechanical robustness and ease of fabrication of PDMS waveguides provides a promising and versatile platform for biosensor application.

  12. Characterization of Piezoelectric PDMS-Nanoparticle Composites (United States)

    Borsa, C. J.; Mionic Ebersold, M.; Bowen, P.; Farine, P.-A.; Briand, D.


    In this work, the novel fabrication and characterization of elastomeric piezoelectric nanocomposites are explored. Fabrication methods explored herein utilize ball milled barium titanate powder dispersions, along with double walled carbon nanotubes which are dispersed in toluene though the use of an ultrasonic probe. Test devices are then constructed with electrodes made from evaporated gold on polyimide foils and protective dielectrics of pristine PDMS. Two different device construction methods are explored utilizing both direct contact bonding and plasma bonding of the active composite layers to the dielectric/electrode. Test samples are evaluated through the use of a dedicated Berlincourt type piezoelectric d33 meter.

  13. Elastic properties of nonstoichiometric reacted PDMS networks

    DEFF Research Database (Denmark)

    Skov, Anne Ladegaard; Hansen, Kristoffer Karsten; Sommer-Larsen, Peter;


    The influence of stoichiometry on the elastic modulus of eight-functional end-linked poly(dimethylsiloxane) (PDMS) networks was investigated by extensional rheometry with extensions up to more than 100%, and the stress-strain relation was found to be almost linear-a characteristic property...... obtained for the Mooney-Rivlin constants. It was furthermore found that trapped entanglements dominate when there is an excess of cross-linker, ensuring that all long difunctional DMS chains are bound to the infinite network in both ends....

  14. Improving dielectric permittivity by incorporating PDMS-PEG block copolymer into PDMS network

    DEFF Research Database (Denmark)

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

    Polydimethylsiloxane (PDMS) is well-known to cause hydrophobic surfaces due to their low surface energy as well as they possess low conductivity and extremely low glass transition temperature 1. On the other hand, polyethyleneglycol (PEG) behaves hydrophilic and is a highly conductive polymer...

  15. Dependence of optical structure of coke from black coal on petrologic peculiarities of the coal

    Energy Technology Data Exchange (ETDEWEB)

    Proskuryakov, A.E.; Stankevich, A.S.; Podchishchaeva, N.I.; Shkoller, M.B.


    Analyzes factors that influence optical structure of coke from Kuzbass black coal. An optical microscope (magnification 800-2,000 times) was used. On the basis of investigations 8 types of optical structures in coke were determined: an isotropic structure, fine grain structure, medium grain structure, large grain structure, fibre-like structure, inertinite structure and a relict structure. The following criteria for determining optical structures are used: optical character of coke matter, grain size, grain geometry, microlites and primary structure. Using regression analysis, dependence of the optical structures on the following indices were derived: vitrinite reflectivity, vitrinite content and reduction degree. 12 refs.

  16. PDMS-based Optical Leaky Waveguide Coated with Self-assemble Au-NPs for Bio-analytical Detections

    Directory of Open Access Journals (Sweden)

    Yi-Chieh Chen


    Full Text Available This paper presents a novel method for fabricating PDMS-based optical leaky waveguides coated with self-assembled gold nano-particles (Au-NP for bio-analytical detection utilizing the localized surface plasmon resonance (LSPR effect. In the presented method, a PDMS optical waveguide is first cast in Teflon tubing to form a cylindrical leaky waveguide structure. The de-molded PDMS optical waveguide is then modified with PDDA molecules and coated with a layer of 13 nm Au-NPs for inducing the LSPR effect. The fabricated LSPR sensor is finally connected to multi-mode optic fibers for guiding the detection light. The measured sensitivity of the PDMS waveguide based LSPR sensor for detecting diluted glycerol solutions was 7.25 AU/RIU and 325.97 nm/RIU. Experimental results of a label-free detection of DNA hybridization show that the presented PDMS waveguide based LSPR sensor has a good linear response and has a detection limit of about 10pM, confirming the detection performance of the developed PDMS waveguide-based LSPR sensor.

  17. Domain Structure of Black Hole Space-Times with a Cosmological Constant

    CERN Document Server

    Armas, Jay; Harmark, Troels


    We generalize the domain structure for stationary black hole space-times to include asymptotically de Sitter and Anti-de Sitter space-times. Given a set of commuting Killing vector fields of a space-time the domain structure lives on the submanifold of the orbit space on which at least one of the Killing vector fields has zero norm. In general the domain structure provides topological and geometrical invariants of black hole space-times that in specific cases have proven to be a crucial part of a full characterization leading to uniqueness theorems. In four and five dimensions the domain structure generalizes the rod structure. We examine in detail the domain structure for four, five, six and seven-dimensional black hole space-times including a very general class of spherically symmetric and static black hole space-times as well as the exact solutions for Kerr-(Anti)-de Sitter black holes. While for asymptotically Anti-de Sitter space-times the domain structures resemble that of asymptotically flat space-time...

  18. Stretchable Metamaterial Absorber Using Liquid Metal-Filled Polydimethylsiloxane (PDMS

    Directory of Open Access Journals (Sweden)

    Kyeongseob Kim


    Full Text Available A stretchable metamaterial absorber is proposed in this study. The stretchability was achieved by liquid metal and polydimethylsiloxane (PDMS. To inject liquid metal, microfluidic channels were fabricated using PDMS powers and microfluidic-channel frames, which were built using a three-dimensional printer. A top conductive pattern and ground plane were designed after considering the easy injection of liquid metal. The proposed metamaterial absorber comprises three layers of PDMS substrate. The top layer is for the top conductive pattern, and the bottom layer is for the meandered ground plane. Flat PDMS layers were inserted between the top and bottom PDMS layers. The measured absorptivity of the fabricated absorber was 97.8% at 18.5 GHz, and the absorption frequency increased from 18.5 to 18.65 GHz as the absorber was stretched from its original length (5.2 cm to 6.4 cm.

  19. Bulk modification of PDMS microchips by an amphiphilic copolymer. (United States)

    Xiao, Yan; Yu, Xiao-Dong; Xu, Jing-Juan; Chen, Hong-Yuan


    A simple and rapid bulk-modification method based on adding an amphiphilic copolymer during the fabrication process was employed to modify PDMS microchips. Poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) was used as the additive substance. Compared to the native PDMS microchips, both the contact angle and the EOF of the bulk-modified PDMS microchips decreased. The effects of the additive loading and the pH on the EOF were investigated in detail. The bulk-modified PDMS microchips exhibited reproducible and stable EOF behavior. The application of the bulk-modified PDMS microchips was also studied and the results indicated that they could be successfully used to separate amino acids and to suppress protein adsorption.

  20. Phase structures of 4D stringy charged black holes in canonical ensemble

    CERN Document Server

    Jia, Qiang; Tan, Xiao-Jun


    We study the thermodynamics and phase structures of the asymptotically flat dilatonic black holes in 4 dimensions, placed in a cavity {\\it a la} York, in string theory for an arbitrary dilaton coupling. We consider these charged black systems in canonical ensemble for which the temperature at the wall of and the charge inside the cavity are fixed. We find that the dilaton coupling plays the key role in the underlying phase structures. The connection of these black holes to higher dimensional brane systems via diagonal (double) and/or direct dimensional reductions indicates that the phase structures of the former may exhaust all possible ones of the latter, which are more difficult to study, under conditions of similar settings. Our study also shows that a diagonal (double) dimensional reduction preserves the underlying phase structure while a direct dimensional reduction has the potential to change it.

  1. Features for Exploiting Black-Box Optimization Problem Structure

    DEFF Research Database (Denmark)

    Tierney, Kevin; Malitsky, Yuri; Abell, Tinus


    Black-box optimization (BBO) problems arise in numerous scientic and engineering applications and are characterized by compu- tationally intensive objective functions, which severely limit the number of evaluations that can be performed. We present a robust set of features that analyze the tness...... landscape of BBO problems and show how an algorithm portfolio approach can exploit these general, problem indepen- dent features and outperform the utilization of any single minimization search strategy. We test our methodology on data from the GECCO Workshop on BBO Benchmarking 2012, which contains 21...

  2. PDMS microchannel fabrication technique based on microwire-molding

    Institute of Scientific and Technical Information of China (English)

    JIA YueFei; JIANG JiaHuan; MA XiaoDong; LI Yuan; HUANG HeMing; CAI KunBao; CAI ShaoXi; WU YunPeng


    Micro-flow channel is basic functional component of microfluidic chip, and every step-forward of its construction technique has been receiving concern all over the world. This article presents a notcomplicated but flexible method for fabrication of micro-flow channels. This method mainly utilizes the conventional molding capability of polydimethylsiloxane (PDMS) and widespread commercial microwires as templates. We have fabricated out some conventional types of microchannels with different topological shapes, as examples for the demonstration of this flexible fabrication route which was not dependent on the stringent demands of photolithographical or microelectromechanical system (MEMS)techniques. The smooth surface, high-intensity, and high flexibility of the wires made it possible to create many types of topological structures of the two-dimensional or three-dimensional microchannel or channel array. The geometric shape of the cross-section of thus forming microchannel in PDMS was the negative of that of embedded-in microwire, in high-fidelity if suitable measures were taken. Moreover, such a microchannel fabrication process can easily integrate the conductivity and low resistivity of the metal wire to create micro-flow devices that are suitable for the electromagnetic control of liquid or the temperature regulation in the microchannel. Furthermore some preliminary optical analysis was provided for the observation of thus forming rounded microchannel. Based on this molding strategy,we even made some prototypes for functional microflow application, such as microsolenoids chip and temperature control gadgets. And an experiment of forming a droplet in the cross channel further confirmed the feasibility and applicability of this flexible microchannel forming technique.

  3. The Young Modulus of Black Strings and the Fine Structure of Blackfolds

    CERN Document Server

    Armas, Jay; Harmark, Troels; Obers, Niels A


    We explore corrections in the blackfold approach, which is a worldvolume theory capturing the dynamics of thin black branes. The corrections probe the fine structure of the branes, going beyond the approximation in which they are infinitely thin, and account for the dipole moment of worldvolume stress-energy as well as the internal spin degrees of freedom. We show that the dipole correction is induced elastically by bending a black brane. We argue that the long-wavelength transport coefficient capturing this response is a relativistic generalization of the Young modulus of elastic materials and we compute it analytically. Using this we draw predictions for black rings in dimensions greater than six. Furthermore, we employ our corrected blackfold equations to various multi-spinning black hole configurations in the blackfold limit, finding perfect agreement with known analytic solutions.

  4. On The Phase Structure and Thermodynamic Geometry of R-Charged Black Holes

    CERN Document Server

    Sahay, Anurag; Sengupta, Gautam


    We study the phase structure and equilibrium state space geometry of R-charged black holes in $D = 5$, 4 and 7 and the corresponding rotating $D3$, $M2$ and $M5$ branes. For various charge configuratins of the compact black holes in the canonical ensemble we demonstrate new liquid-gas like phase coexistence behaviour culminating in second order critical points. The critical exponents turn out to be the same as that of four dimensional asymptotically AdS black holes in Einstein Maxwell theory. We further establish that the regions of stability for R-charged black holes are, in some cases, more constrained than is currently believed, due to properties of some of the response coefficients. The equilibrium state space scalar curvature is calculated for various charge configurations, both for the case of compact as well as flat horizons and its asymptotic behaviour with temperature is established.

  5. Echoes from the Abyss: Evidence for Planck-scale structure at black hole horizons

    CERN Document Server

    Abedi, Jahed; Afshordi, Niayesh


    In classical General Relativity (GR), an observer falling into an astrophysical black hole is not expected to experience anything dramatic as she crosses the event horizon. However, tentative resolutions to problems in quantum gravity, such as the cosmological constant problem, or the black hole information paradox, invoke significant departures from classicality in the vicinity of the horizon. It was recently pointed out that such near-horizon structures can lead to late-time echoes in the black hole merger gravitational wave signals that are otherwise indistinguishable from GR. We search for observational signatures of these echoes in the gravitational wave data released by advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), following the three black hole merger events GW150914, GW151226, and LVT151012. In particular, we look for repeating damped echoes with time-delays of $8 M \\log M$ (+spin corrections, in Planck units), corresponding to Planck-scale departures from GR near their respecti...

  6. The Canadian war on drugs: structural violence and unequal treatment of Black Canadians. (United States)

    Khenti, Akwatu


    This paper examines the impact of Canada's war on drugs on segments of the Black community, specifically with respect to the impact of structural violence, over-policing, and high incarceration rates. It offers evidence of the systemic nature of these dynamics by examining the early context of the war, growing stigma against Blacks, globalizing influences, and the punitive focus of funding and policy. The paper also explores how Black men have been identified as the main enemy and how drug control efforts have served to diminish the health, well-being, and self-image of Black men via discriminatory and inequitable treatment before the law. The current high rates of imprisonment of Black men are an indicator of systematic deprivation of significant social capital, which will perpetuate socioeconomic harm and cycles of violence. This commentary calls for an immediate dissolution of policies regulating the war on drugs as the first step in remedying the injustices experienced by Black Canadians. Due to the lack of Canadian data in this important area, the paper also emphasizes the critical need for more research to shed more light on the Canadian-specific complexities.

  7. Horizon structure of rotating Einstein-Born-Infeld black holes and shadow

    Energy Technology Data Exchange (ETDEWEB)

    Atamurotov, Farruh [Institute of Nuclear Physics, Tashkent (Uzbekistan); Inha University in Tashkent, Tashkent (Uzbekistan); Ulugh Beg Astronomical Institute, Tashkent (Uzbekistan); National University of Uzbekistan, Tashkent (Uzbekistan); Ghosh, Sushant G. [Jamia Millia Islamia, Centre for Theoretical Physics, New Delhi (India); University of Kwa-Zulu-Natal, Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, Private Bag 54001, Durban (South Africa); Ahmedov, Bobomurat [Institute of Nuclear Physics, Tashkent (Uzbekistan); Ulugh Beg Astronomical Institute, Tashkent (Uzbekistan); National University of Uzbekistan, Tashkent (Uzbekistan)


    We investigate the horizon structure of the rotating Einstein-Born-Infeld solution which goes over to the Einstein-Maxwell's Kerr-Newman solution as the Born-Infeld parameter goes to infinity (β → ∞). We find that for a given β, mass M, and charge Q, there exist a critical spinning parameter a{sub E} and r{sub H}{sup E}, which corresponds to an extremal Einstein-Born-Infeld black hole with degenerate horizons, and a{sub E} decreases and r{sub H}{sup E} increases with increase of the Born-Infeld parameter β, while a < a{sub E} describes a non-extremal Einstein-Born-Infeld black hole with outer and inner horizons. Similarly, the effect of β on the infinite redshift surface and in turn on the ergo-region is also included. It is well known that a black hole can cast a shadow as an optical appearance due to its strong gravitational field. We also investigate the shadow cast by the both static and rotating Einstein-Born-Infeld black hole and demonstrate that the null geodesic equations can be integrated, which allows us to investigate the shadow cast by a black hole which is found to be a dark zone covered by a circle. Interestingly, the shadow of an Einstein-Born-Infeld black hole is slightly smaller than for the Reissner-Nordstrom black hole, which consists of concentric circles, for different values of the Born-Infeld parameter β, whose radius decreases with increase of the value of the parameter β. Finally, we have studied observable distortion parameter for shadow of the rotating Einstein-Born-Infeld black hole. (orig.)

  8. Internal structure of non-Abelian black holes and nature of singularity

    CERN Document Server

    Galtsov, D V; Zotov, M Yu


    Recent results concerning the internal structure of static spherically-symmetric non-Abelian black holes in the Einstein-Yang-Mills (EYM) theory and its generalizations including scalar fields are reviewed and discussed with an emphasis on the problem of a generic singularity in black holes. It is argued that in the theories admitting a violation of the naive no-hair conjecture the structure of singularity is essentially affected by the "hair roots". This invalidates an image of a non-Abelian black hole as a Schwarzschild black hole sitting inside the soliton. We give an analytic description of the generic oscillatory approach to the singularity in the pure EYM theory in terms of a divergent discrete sequence and show that the mass function is exponentially growing "in average". The second type of a generic approach to the singularity in hairy black holes is a "power-law mass inflation" which is realized in the theories including scalar fields. Both singularities are spacelike and no Cauchy horizons are met i...

  9. Viscoelastic nature of Au nanoparticle–PDMS nanocomposite gels

    Indian Academy of Sciences (India)

    Ritu Gupta; Hima K Nagamanasa; Rajesh Ganapathy; Giridhar U Kulkarni


    A stable gel of Au nanoparticles in polydimethylsiloxane (PDMS) nanocomposite is prepared by employing the curing agent of PDMS elastomer as a reducing agent for the formation of Au nanoparticles by an in-situ process. The viscoelastic nature of these gels is very sensitive to the Au nanoparticle loading and the synthetic temperature conditions. Even a very low Au content of 0.09 wt% is sufficient enough to bring in the transition from sponge state to gel state at room temperature. Higher synthetic temperature also forms sponge formation. Infrared and ultraviolet–visible spectroscopy measurements have provided insight into PDMS crosslinking and nanoparticle formation, respectively. The optimization of the gel properties can have direct influence on the processability of Au nanoparticle–PDMS nanocomposite gels, with interesting implications in electronic, optical and microfluidic devices.

  10. Truncated acoustic black hole structure with the optimized tapering shape and damping coating

    DEFF Research Database (Denmark)

    Ih, Jeong-Guon; Kim, Miseong; Lee, Ik Jin


    The acoustic black hole (ABH) structure can be an option as a vibration damper by providing a tapered wedge at the end of a beam or plate. However, not much work has been done on design to yield an effective ABH design for such a plate. We attempt to optimize the shape of the ABH to effectively...

  11. An Experimental and Theoretical Investigation of Ultrasound Transmission in Bubbly PDMS Phononic Crystals (United States)

    Christianson, Caleb; Mukhopadhyay, Saikat; Sachse, Wolfgang; Stewart, Derek


    Phononic crystals are two- and three-dimensional structures with a periodic arrangement of two or more materials with different acoustic properties. Depending on the size, structure, and characteristics of the constituent materials, metamaterials with interesting acoustic properties can be formed. These crystals can be used to control the transmission of sound at selected frequencies, focus sound, or serve as waveguides. In this talk, we will focus on the transmission of ultrasonic waves through polydimethylsiloxane (PDMS) films with entrapped air bubbles. Two different theoretical models were used to predict ultrasonic transmission through air-PDMS crystals: (1) a simple scattering model for a series of partially reflective thin films and (2) the code MULTEL, which calculates the transmission using multiple scattering theory. A fabrication process was also developed to stack layers of the crystals with unprecedented alignment. We measured the ultrasonic transmission through the films using the ultrasonic through-transmission mode in a water bath and found an excellent agreement between the measured and calculated transmission. Additionally, we used these models to predict the performance of new phononic structures by scanning a large parameter space and showed how ultrasonic transmission through PDMS layers can be engineered by varying the dimensions, separation, and arrangement of air bubbles. This work was supported by the National Science Foundation.

  12. Isolated Horizon structures in quasi-equilibrium black hole initial data

    CERN Document Server

    Jaramillo, José Luis


    Isolated horizon conditions enforce the time invariance of both the intrinsic and the extrinsic geometry of a (quasi-local) black hole horizon. Non-expanding horizons, only requiring the invariance of the intrinsic geometry, have been succesfully employed in (excision) initial data of black holes in instantaneous equilibrium. Here we propose the use of the full isolated horizon structure when solving the elliptic system that results from the full set of conformal 3+1 Einstein equations under a quasi-equilibrium Ansatz prescription. We argue that a set geometric inner boundary conditions for this extended elliptic system then follows, determining the shape of the excision surface.

  13. Microscopic quantum structure of black hole and vacuum versus quantum statistical origin of gravity

    CERN Document Server

    Wang, Shun-Jin


    The Planckon densely piled model of vacuum is proposed. Based on it, the microscopic quantum structure of Schwarzschild black hole and quantum statistical origin of its gravity are studied. It is shown that thermodynamic temperature equilibrium and mechanical acceleration balance make the space-time of the black hole horizon singular and Casimir effect works inside the horizon. This effect makes the inside vacuum have less zero fluctuation energy than the outside vacuum, and a temperature difference as well as gravity as thermal pressure are created. A dual relation between inside and outside regions of the black hole is found. By dual relation, an attractor behaviour of the horizon surface is unveiled. Outside horizon, there exist thermodynamic non-equilibrium and mechanical non-balance which lead to outward centrifugal energy flow and inward gravitation energy flow, their compensation establishes local equilibrium. The lost vacuum energy in negative gravitation potential regions has been removed to the blac...

  14. DNA microarray synthesis by using PDMS molecular stamp (II) -- Oligonucleotide on-chip synthesis using PDMS stamp

    Institute of Scientific and Technical Information of China (English)


    Based on the standard phosphoramidites chemistry protocol, two oligonucleotides synthetic routes were studied by contact stamping reactants to a modified glass slide. Route A was a contact coupling reaction, in which a nucleoside monomer was transferred and coupled to reactive groups (OH) on a substrate by spreading the nucleoside activated with tetrazole on a polydimethylsiloxane (PDMS) stamp. Route B was a contact detritylation, in which one nucleoside was fixed on the desired synthesis regions where dimethoxytrityl (DMT) protecting groups on the 5′-hydroxyl of the support-bound nucleoside were removed by stamping trichloroacetic acid (TCA) distributed on features on a PDMS stamp. Experiments showed that the synthetic yield and the reaction speed of route A were higher than those of route B. It was shown that 20 mer oligonucleotide arrays immobilized on the glass slide were successfully synthesized using the PDMS stamps, and the coupling efficiency showed no difference between the PDMS stamping and the conventional synthesis methods.

  15. Horizon structure of Kerr-Bardeen black hole and particle acceleration

    CERN Document Server

    Ghosh, Sushant G


    We investigate the horizon structure and ergoregion in a Kerr-Bardeen regular black hole, a rotating generalization of the well known regular black hole due to Bardeen \\cite{Bardeen:1968}, which has an additional parameter ($g$) due to magnetic charge, apart from mass ($M$) and rotation parameter ($a$). Interestingly, for each value of parameter $g$, there exist a critical rotation parameter ($a=a_{E}$), which corresponds to an extremal black hole with degenerate horizons, while for $aa_{E}$. We find that the extremal value $a_E$ is also influenced by the parameter $g$ and so is the ergoregion. While the value of $a_E$ remarkably decreases when compared with the Kerr black hole, the ergoregion becomes more thick with increase in $g$. We also study collision of two equal mass particle near the horizon of this black hole, and explicitly bring out the effect of parameter $g$. The center-of-mass energy ($E_{CM}$) not only depends on rotation parameter $a$, but also on parameter $g$. It is demonstrated that the ce...

  16. Effect of van der Waals interactions on the structural and elastic properties of black phosphorus

    DEFF Research Database (Denmark)

    Appalakondaiah, S.; Vaitheeswaran, G.; Lebègue, S.;


    The structural and elastic properties of orthorhombic black phosphorus have been investigated using first-principles calculations based on density functional theory. The structural parameters have been calculated using the local density approximation (LDA), the generalized gradient approximation...... (GGA), and with several dispersion corrections to include van der Waals interactions. It is found that the dispersion corrections improve the lattice parameters over LDA and GGA in comparison with experimental results. The calculations reproduce well the experimental trends under pressure and show...

  17. Controlled Contamination of Epoxy Composites with PDMS and Removal by Laser Ablation (United States)

    Palmieri, Frank; Ledesma, Rodolfo; Cataldo, Daniel; Lin, Yi; Wohl, Christopher; Gupta, Mool; Connell, John


    Surface preparation is critical to the performance of adhesively bonded composites. During manufacturing, minute quantities of mold release compounds are inevitably deposited on faying surfaces and may compromise bond performance. To ensure safety, mechanical fasteners and other crack arrest features must be installed in the bondlines of primary structures, which negates some advantages of adhesively bonded construction. Laser ablation is an automated, repeatable, and scalable process with high potential for the surface preparation of metals and composites in critical applications such as primary airframe structures. In this study, laser ablation is evaluated on composite surfaces for the removal of polydimethylsiloxane (PDMS), a common mold release material. Composite panels were contaminated uniformly with PDMS film thicknesses as low as 6.0 nm as measured by variable angle spectroscopic ellipsometry. Bond performance was assessed by mechanical testing using a 250 F cure, epoxy adhesive and compared with pre-bond surface inspection results. Water contact angle, optically stimulated electron emission, and laser induced breakdown spectroscopy were used to characterize contaminated and laser ablated surfaces. The failure mode obtained from double cantilever beam tests correlated well with surface characterization data. The test results indicated that even low levels of PDMS were not completely removed by laser ablation.

  18. Intrinsic Topological Structure of Entropy of Kerr Black Holes%Kerr黑洞熵的内禀拓扑结构

    Institute of Scientific and Technical Information of China (English)

    颜继江; 杨国宏; 田立君


    In the light of φ-mapping method and the relationship between entropy and the Euler characteristic, the intrinsic topological structure of entropy of Kerr black holes is studied. From the Gauss-Bonnet-Chern theorem, it is shown that the entropy of Kerr black hole is determined by singularities of the Killing vector field of spacetime. These singularities naturally carry topological numbers, Hopf indices and Brouwer degrees, which can also be viewed as topological quantization of entropy of Kerr black holes. Specific results S =A/4 for non-extreme Kerr black holes and S = 0 for extreme ones are calculated independently by using the above-mentioned methods.

  19. Novel hierarchical tantalum oxide-PDMS hybrid coating for medical implants: One pot synthesis, characterization and modulation of fibroblast proliferation. (United States)

    Tran, Phong A; Fox, Kate; Tran, Nhiem


    Surface properties such as morphology, roughness and charge density have a strong influence on the interaction of biomaterials and cells. Hierarchical materials with a combination of micron/submicron and nanoscale features for coating of medical implants could therefore have significant potential to modulate cellular responses and eventually improve the performance of the implants. In this study, we report a simple, one pot wet chemistry preparation of a hybrid coating system with hierarchical surface structures consisting of polydimethylsiloxane (PDMS) and tantalum oxide. Medical grade, amine functional PDMS was mixed with tantalum ethoxide which subsequently formed Ta2O5in situ through hydrolysis and condensation during coating process. The coatings were characterized by SEM, EDS, XPS, confocal scanning microscopy, contact angle measurement and in vitro cell culture. Varying PDMS and tantalum ethoxide ratios resulted in coatings of different surface textures ranging from smooth to submicro- and nano-structured. Strikingly, hierarchical surfaces containing both microscale (1-1.5μm) and nanoscale (86-163nm) particles were found on coatings synthesized with 20% and 40% (v/v) tantalum ethoxide. The coatings were similar in term of hydrophobicity but showed different surface roughness and chemical composition. Importantly, higher cell proliferation was observed on hybrid surface with hierarchical structures compared to pure PDMS or pure tantalum oxide. The coating process is simple, versatile, carried out under ambient condition and requires no special equipment.

  20. Hybrid integrated PDMS microfluidics with a silica capillary. (United States)

    Dimov, Ivan K; Riaz, Asif; Ducrée, Jens; Lee, Luke P


    To harness the properties of both PDMS and silica, we have demonstrated hybrid integrated PDMS microfluidic systems with fused silica capillaries. The hybrid integrated PDMS microfluidics and silica capillary (iPSC) modules exhibit a novel architecture and method for leakage free CE sample injection merely requiring a single high voltage source and one pair of electrodes. The use of the iPSC device is based on a modular approach which allows the capillary to be reused extensively whilst replacing the attached fluidic module for different experiments. Integrating fused silica capillaries with PDMS microfluidic modules allows the direct application of a wide variety of well established conventional CE protocols for separations of complex analytes. Furthermore it bears the potential for facile coupling to standard electro-spray ionization mass spectrometry (ESI-MS), letting users focus on the sample analysis rather than the development of new separation protocols. The fabrication of the iPSC module consists of a simple and quick three-step method that submerges a fused silica capillary in PDMS prepolymer. After cross linking the prepolymer and punching the inlets, the iPSC module layer can be mounted onto a microfluidic device for CE separation.

  1. Black holes and global structures of spherical spacetimes in Horava-Lifshitz theory

    CERN Document Server

    Greenwald, Jared; Lu, J X; Satheeshkumar, V H; Wang, Anzhong


    We systematically study black holes in the Horava-Lifshitz (HL) theory by following the kinematic approach, in which a horizon is defined as the surface at which massless test particles are infinitely redshifted. Because of the nonrelativistic dispersion relations, the speed of light is unlimited, and test particles do not follow geodesics. As a result, there are significant differences in causal structures and black holes between general relativity (GR) and the HL theory. In particular, horizon radii generically depend on the energies of test particles. Applying them to the spherical static vacuum solutions found recently in the nonrelativistic general covariant theory of gravity, we find that, for test particles with sufficiently high energy, the radius of the horizon can be made as small as desired, although the singularities can be seen in principle only by observers with infinitely high energy. In these studies, we pay particular attention to the global structures of the solutions, and find that, because...

  2. Further Evidence for the Conformal Structure of a Schwarzschild Black Hole in an Algebraic Approach

    CERN Document Server

    Sen-Gupta, K; Gupta, Kumar S.; Sen, Siddhartha


    We study the excitations of a massive Schwarzschild black hole of mass M resulting from the capture of infalling matter described by a massless scalar field. The near-horizon dynamics of this system is governed by a Hamiltonian which is related to the Virasoro algebra and admits a one-parameter family of self-adjoint extensions described by a parameter z \\in R . The density of states of the black hole can be expressed equivalently in terms of z or M, leading to a consistent relation between these two parameters. The corresponding black hole entropy is obtained as S = S(0) - 3/2 log S(0) + C, where S(0) is the Bekenstein-Hawking entropy, C is a constant with other subleading corrections exponentially suppressed. The appearance of this precise form of the black hole entropy within our formalism, which is expected on general grounds in any conformal field theoretic description, provides strong evidence for the near-horizon conformal structure in this system.

  3. Dynamics of the population phenological structure of Polistes dominulus in the black sea biosphere reserve

    Directory of Open Access Journals (Sweden)

    L. Y. Rusina


    Full Text Available The change in the phenotypic population structure of Polistes dominulus (Christ (Hymenoptera, Vespidae paper-wasp nested in the Black Sea Reserve was analysed. It was shown that colour patterns of clypeus, mesoscutum and first tergite vary considerably in different phases of the population number. The impact of factors of different nature on the relationship between the colour patterns and mode of colony foundation is discussed.

  4. Dynamics of the population phenological structure of Polistes dominulus in the black sea biosphere reserve


    L. Y. Rusina; Е. S. Orlova


    The change in the phenotypic population structure of Polistes dominulus (Christ) (Hymenoptera, Vespidae) paper-wasp nested in the Black Sea Reserve was analysed. It was shown that colour patterns of clypeus, mesoscutum and first tergite vary considerably in different phases of the population number. The impact of factors of different nature on the relationship between the colour patterns and mode of colony foundation is discussed.

  5. Nanooxide/Polymer Composites with Silica@PDMS and Ceria-Zirconia-Silica@PDMS: Textural, Morphological, and Hydrophilic/Hydrophobic Features (United States)

    Sulym, Iryna; Goncharuk, Olena; Sternik, Dariusz; Terpilowski, Konrad; Derylo-Marczewska, Anna; Borysenko, Mykola V.; Gun'ko, Vladimir M.


    SiO2@PDMS and CeO2-ZrO2-SiO2@PDMS nanocomposites were prepared and studied using nitrogen adsorption-desorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), measurements of advancing and receding contact angles with water, and microcalorimetry. The pore size distributions indicate that the textural characteristics change after oxide modification by poly(dimethylsiloxane) (PDMS). Composites are characterized by mainly mesoporosity and macroporosity of aggregates of oxide nanoparticles or oxide@PDMS nanoparticles and their agglomerates. The FT-IR spectra show that PDMS molecules cover well the oxide surface, since the intensity of the band of free silanols at 3748 cm-1 decreases with increasing PDMS concentration and it is absent in the IR spectrum at C PDMS ≥ 20 wt% that occurs due to the hydrogen bonding of the PDMS molecules to the surface hydroxyls. SEM images reveal that the inter-particle voids are gradually filled and aggregates are re-arranged and increase from 20 to 200 nm in size with the increasing polymer concentration. The highest hydrophobicity (contact angle θ = 140° at C PDMS = 20-40 wt%) is obtained for the CeO2-ZrO2-SiO2@PDMS nanocomposites. The heat of composite immersion in water shows a tendency to decrease with increasing PDMS concentration.

  6. Design and Fabrication of a PDMS Microchip Based Immunoassay

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Guocheng; Wang, Wanjun; Wang, Jun; Lin, Yuehe


    In this paper, we describe the design and fabrication process of a polydimethylsiloxane (PDMS) microchip for on-chip multiplex immunoassay application. The microchip consists of a PDMS microfluidic channel layer and a micro pneumatic valve control layer. By selectively pressurizing the pneumatic microvalves, immuno reagents were controlled to flow and react in certain fluidic channel sites. Cross contamination was prevented by tightly closed valves. Our design was proposed to utilize PDMS micro channel surface as the solid phase immunoassay substrate and simultaneously detect four targets antigens on chip. Experiment result shows that 20psi valve pressure is sufficient to tightly close a 200µm wide micro channel with flow rate up to 20µl/min.

  7. Viscoelastic and optical properties of four different PDMS polymers (United States)

    Deguchi, Shinji; Hotta, Junya; Yokoyama, Sho; Matsui, Tsubasa S.


    Polydimethylsiloxane (PDMS) is the most commonly used silicone elastomer with a wide range of applications including microfluidics and microcontact printing. Various types of PDMS are currently available, and their bulk material properties have been extensively investigated. However, because the properties are rarely compared in a single study, it is often unclear whether the large disparity of the reported data is attributable to the difference in methodology or to their intrinsic characteristics. Here we report on viscoelastic properties and optical properties of four different PDMS polymers, i.e. Sylgard-184, CY52-276, SIM-360, and KE-1606. Our results show that all the PDMSs are highly elastic rather than viscoelastic at the standard base/curing agent ratios, and their quantified elastic modulus, refractive index, and optical cleanness are similar but distinct in magnitude.

  8. Toluene optical fibre sensor based on air microcavity in PDMS (United States)

    Kacik, Daniel; Martincek, Ivan


    We prepared and demonstrated a compact, simple-to-fabricate, air microcavity in polydimethylsiloxane (PDMS) placed at the end of a single-mode optical fibre. This microcavity creates a Fabry-Perot interferometer sensor able to measure concentrations of toluene vapour in air. Operation of the sensor is provided by diffusion of the toluene vapour to the PDMS, and the consequent extension of length d of the air microcavity in PDMS. The sensor response for the presence of vapours is fast and occurs within a few seconds. By using the prepared sensor toluene vapour concentration in air can be measured in the range from about 0.833 g.m-3 to saturation, with better sensitivity than 0.15 nm/g.m-3 up to maximal sensitivity 1.4 nm/g.m-3 at around concentration 100 g.m-3 in time 5 s.

  9. Osteogenic differentiation on DLC-PDMS-h surface. (United States)

    Soininen, Antti; Kaivosoja, Emilia; Sillat, Tarvo; Virtanen, Sannakaisa; Konttinen, Yrjö T; Tiainen, Veli-Matti


    The hypothesis was that anti-fouling diamond-like carbon polydimethylsiloxane hybrid (DLC-PDMS-h) surface impairs early and late cellular adhesion and matrix-cell interactions. The effect of hybrid surface on cellular adhesion and cytoskeletal organization, important for osteogenesis of human mesenchymal stromal cells (hMSC), where therefore compared with plain DLC and titanium (Ti). hMSCs were induced to osteogenesis and followed over time using scanning electron microscopy (SEM), time-of-flight secondary ion mass spectrometry (ToF-SIMS), immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR), and hydroxyapatite (HA) staining. SEM at 7.5 hours showed that initial adherence and spreading of hMSC was poor on DLC-PDMS-h. At 5 days some hMSC were undergoing condensation and apoptotic fragmentation, whereas cells on DLC and Ti grew well. DAPI-actin-vinculin triple staining disclosed dwarfed cells with poorly organized actin cytoskeleton-focal complex/adhesion-growth substrate attachments on hybrid coating, whereas spread cells, organized microfilament bundles, and focal adhesions were seen on DLC and in particular on Ti. Accordingly, at day one ToF-SIMS mass peaks showed poor protein adhesion to DLC-PDMS-h compared with DLC and Ti. COL1A1, ALP, OP mRNA levels at days 0, 7, 14, 21, and/or 28 and lack of HA deposition at day 28 demonstrated delayed or failed osteogenesis on DLC-PDMS-h. Anti-fouling DLC-PDMS-h is a poor cell adhesion substrate during the early protein adsorption-dependent phase and extracellular matrix-dependent late phase. Accordingly, some hMSCs underwent anoikis-type apoptosis and failed to complete osteogenesis, due to few focal adhesions and poor cell-to-ECM contacts. DLC-PDMS-h seems to be a suitable coating for non-integrating implants/devices designed for temporary use.

  10. Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre

    CERN Document Server

    Doeleman, Sheperd; Rogers, Alan E E; Plambeck, Richard; Freund, Robert; Tilanus, Remo P J; Friberg, Per; Ziurys, Lucy M; Moran, James M; Corey, Brian; Young, Ken H; Smythe, Daniel L; Titus, Michael; Marrone, Daniel P; Cappallo, Roger J; Bock, Douglas C J; Bower, Geoffrey C; Chamberlin, Richard; Davis, Gary R; Krichbaum, Thomas P; Lamb, James; Maness, Holly; Niell, Arthur E; Roy, Alan; Strittmatter, Peter; Werthimer, Daniel; Whitney, Alan R; Woody, David


    The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation (ref 1). Sagittarius A*, the compact source of radio, infrared and X-ray emission at the centre of the Milky Way, is the closest example of this phenomenon, with an estimated black hole mass that is 4 million times that of the Sun (refs. 2,3). A long-standing astronomical goal is to resolve structures in the innermost accretion flow surrounding Sgr A* where strong gravitational fields will distort the appearance of radiation emitted near the black hole. Radio observations at wavelengths of 3.5 mm and 7 mm have detected intrinsic structure in Sgr A*, but the spatial resolution of observations at these wavelengths is limited by interstellar scattering (refs. 4-7). Here we report observations at a wavelength of 1.3 mm that set a size of 37 (+16, -10; 3-sigma) microarcseconds on the intrinsic diameter of Sgr A*. This is less than the expe...

  11. Brans-Dicke Theory with Λ>0: Black Holes and Large Scale Structures. (United States)

    Bhattacharya, Sourav; Dialektopoulos, Konstantinos F; Romano, Antonio Enea; Tomaras, Theodore N


    A step-by-step approach is followed to study cosmic structures in the context of Brans-Dicke theory with positive cosmological constant Λ and parameter ω. First, it is shown that regular stationary black-hole solutions not only have constant Brans-Dicke field ϕ, but can exist only for ω=∞, which forces the theory to coincide with the general relativity. Generalizations of the theory in order to evade this black-hole no-hair theorem are presented. It is also shown that in the absence of a stationary cosmological event horizon in the asymptotic region, a stationary black-hole horizon can support a nontrivial Brans-Dicke hair. Even more importantly, it is shown next that the presence of a stationary cosmological event horizon rules out any regular stationary solution, appropriate for the description of a star. Thus, to describe a star one has to assume that there is no such stationary horizon in the faraway asymptotic region. Under this implicit assumption generic spherical cosmic structures are studied perturbatively and it is shown that only for ω>0 or ω≲-5 their predicted maximum sizes are consistent with observations. We also point out how, many of the conclusions of this work differ qualitatively from the Λ=0 spacetimes.

  12. Temperature and thermodynamic structure of Einstein's equations for a cosmological black hole

    CERN Document Server

    Bhattacharya, Krishnakanta


    It is expected that the cosmological black holes are the closest realistic solutions of gravitational theories and they evolve with time. Moreover, the natural way of defining thermodynamic entities for the stationary ones is not applicable in the case of a time dependent spacetime. Here we confine our discussion within the Sultana-Dyer metric which is a cosmological black hole solution of Einstein's gravity. In literature, there exists two expressions of horizon temperature -- one is time dependent and the other does not depend on time. To single out the correct one we find the temperature by studying the Hawking effect in the tunnelling formalism. This leads to time dependent structure. After identifying the correct one, the Einstein's equations are written on the horizon and we show that this leads to the first law of thermodynamics. In this process the expressions for horizon entropy and energy, obtained earlier by explicit calculations, are being used. This provides the evidence that Einstein's equations...

  13. Jet Launching Structure Resolved Near the Supermassive Black Hole in M87

    CERN Document Server

    Doeleman, Sheperd S; Schenck, David E; Beaudoin, Christopher; Blundell, Ray; Bower, Geoffrey C; Broderick, Avery E; Chamberlin, Richard; Freund, Robert; Friberg, Per; Gurwell, Mark A; Ho, Paul T P; Honma, Mareki; Inoue, Makoto; Krichbaum, Thomas P; Lamb, James; Loeb, Abraham; Lonsdale, Colin; Marrone, Daniel P; Moran, James M; Oyama, Tomoaki; Plambeck, Richard; Primiani, Rurik A; Rogers, Alan E E; Smythe, Daniel L; SooHoo, Jason; Strittmatter, Peter; Tilanus, Remo P J; Titus, Michael; Weintroub, Jonathan; Wright, Melvyn; Young, Ken H; Ziurys, Lucy M; 10.1126/science.1224768


    Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by accretion of matter onto super massive black holes. While the measured width profiles of such jets on large scales agree with theories of magnetic collimation, predicted structure on accretion disk scales at the jet launch point has not been detected. We report radio interferometry observations at 1.3mm wavelength of the elliptical galaxy M87 that spatially resolve the base of the jet in this source. The derived size of 5.5 +/- 0.4 Schwarzschild radii is significantly smaller than the innermost edge of a retrograde accretion disk, suggesting that the M87 jet is powered by an accretion disk in a prograde orbit around a spinning black hole.

  14. fs- and ns-laser processing of polydimethylsiloxane (PDMS) elastomer: Comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Stankova, N.E., E-mail: [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, Sofia 1784 (Bulgaria); Atanasov, P.A.; Nedyalkov, N.N.; Stoyanchov, T.R. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, Sofia 1784 (Bulgaria); Kolev, K.N.; Valova, E.I.; Georgieva, J.S.; Armyanov, St.A. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, Sofia 1113 (Bulgaria); Amoruso, S.; Wang, X.; Bruzzese, R. [CNR-SPIN, Dipartimento di Scienze Fisiche, Universita degli Studi di Napoli Federico II, Complesso Universitario di Monte S. Angelo, Via Cintia, I-80126 Napoli (Italy); Grochowska, K.; Śliwiński, G. [Photophysics Department, The Szewalski Institute, Polish Academy of Sciences, 14 Fiszera St., 80-231 Gdańsk (Poland); Baert, K.; Hubin, A. [Vrije Universiteit Brussels, Faculty of Engineering, Research group, SURF “Electrochemical and Surface Engineering” (Belgium); Delplancke, M.P.; Dille, J. [Université Libre de Bruxelles, Materials Engineering, Characterization, Synthesis and Recycling (Service 4MAT), Faculté des Sciences Appliquées, 1050 Brussels (Belgium)


    Highlights: • fs- and ns-laser (266 and 532 nm) processing of PDMS-elastomer, in air, is studied. • High definition tracks (on the PDMS-elastomer surface) for electrodes are produced. • Selective Pt or Ni metallization of the tracks is produced via electroless plating. • Irradiated and metallized tracks are characterized by μ-Raman spectrometry and SEM. • DC resistance of Pt and Ni tracks is always between 0.5 and 15 Ω/mm. - Abstract: Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial as encapsulation and/or as substrate insulator carrier for long term neural implants because of its remarkable properties. Femtosecond (λ = 263 and 527 nm) and nanosecond (266 and 532 nm) laser processing of PDMS-elastomer surface, in air, is investigated. The influence of different processing parameters, including laser wavelength, pulse duration, fluence, scanning speed and overlapping of the subsequent pulses, on the surface activation and the surface morphology are studied. High definition tracks and electrodes are produced. Remarkable alterations of the chemical composition and structural morphology of the ablated traces are observed in comparison with the native material. Raman spectra illustrate well-defined dependence of the chemical composition on the laser fluence, pulse duration, number of pulses and wavelength. An extra peak about ∼512–518 cm{sup −1}, assigned to crystalline silicon, is observed after ns- or visible fs-laser processing of the surface. In all cases, the intensities of Si−O−Si symmetric stretching at 488 cm{sup −1}, Si−CH{sub 3} symmetric rocking at 685 cm{sup −1}, Si−C symmetric stretching at 709 cm{sup −1}, CH{sub 3} asymmetric rocking + Si−C asymmetric stretching at 787 cm{sup −1}, and CH{sub 3} symmetric rocking at 859 cm{sup −1}, modes strongly decrease. The laser processed areas are also analyzed by SEM and optical microscopy. Selective Pt or Ni metallization of the laser processed

  15. Diameter structure modeling and the calculation of plantation volume of black poplar clones

    Directory of Open Access Journals (Sweden)

    Andrašev Siniša


    Full Text Available A method of diameter structure modeling was applied in the calculation of plantation (stand volume of two black poplar clones in the section Aigeiros (Duby: 618 (Lux and S1-8. Diameter structure modeling by Weibull function makes it possible to calculate the plantation volume by volume line. Based on the comparison of the proposed method with the existing methods, the obtained error of plantation volume was less than 2%. Diameter structure modeling and the calculation of plantation volume by diameter structure model, by the regularity of diameter distribution, enables a better analysis of the production level and assortment structure and it can be used in the construction of yield and increment tables.

  16. The effect of compatibilization and rheological properties of polystyrene and poly(dimethylsiloxane) on phase structure of polystyrene/poly(dimethylsiloxane) blends

    DEFF Research Database (Denmark)

    Chuai, C. Z.; Li, S; Almdal, Kristoffer;


    The compatibilization effect of polystyrene (PS)-poly(dimethylsiloxane) (PDMS) diblock copolymer (PS-b-PDMS) and the effect of rheological properties of PS and PDMS on phase structure of PS/PDMS blends were investigated using a selective extraction technique and scanning electron microscopy (SEM)...

  17. Study of the glow curve structure of the minerals separated from black pepper (Piper nigrum L.) (United States)

    Guzmán, S.; Ruiz Gurrola, B.; Cruz-Zaragoza, E.; Tufiño, A.; Furetta, C.; Favalli, A.; Brown, F.


    The inorganic mineral fraction extracted from black pepper (Piper nigrum L.) has been analysed using a thermoluminescence (TL) method, investigating the glow curve structure, including an evaluation of the kinetic parameters. Different grain sizes, i.e. 10, 74, and 149 μm, were selected from commercial black pepper. The X-ray diffraction of the inorganic fraction shows that quartz is the main mineral present in it. The samples were exposed to 1-25 kGy doses by gamma rays of 60Co in order to analyse the thermally stimulated luminescence response as a function of the delivered dose. The glow curves show a complex structure for different grain sizes of the pepper mineral samples. The fading of the TL signal at room temperature was obtained after irradiation, and it was observed that the maximum peaks of the glow curves shift towards higher values of the temperature when the elapsed time from irradiation increases. It seems that the fading characteristic may be related to a continuous trap distribution responsible for the complex structure of the glow curve. Similar glow curves structure behaviour was found under ultraviolet irradiation of the samples. The activation energy and the frequency factor were determined from the glow curves of different grain sizes using a deconvolution programme because of the evident complexity of the structure.

  18. Microfabrication procedure of PDMS microbeam array using photolithography for laminin printing and piconewton force transduction on axons. (United States)

    Sasoglu, F Mert; Bohl, Andrew J; Layton, Bradley E


    The purpose of this paper is to introduce our design for transducing forces on the order of tens of piconewtons by optically measuring deflection of a microfabricated beam tip as it pulls on an array of flexible structures such as axons in an array of laminin-printed neurons. To achieve this we have designed polymeric beams with spring constants on the order of 10 pN/microm. We have fabricated circular microbeams with Sylgard polydimethylsiloxane (PDMS). The elastic modulus of PDMS was determined experimentally using a microscale and a micrometer at different concentrations of curing agent and base agent and found to be on the order of 100 kPa. The designed geometry is a 100x100 tapered microcone array with each beam having a length of 100 microm, and a base diameter of 10 microm. A SU-8 negative photoresist is etched using photolithography and used as a mold for PDMS soft lithography. PDMS was injected into the mold and the array peeled from the mold.

  19. Novel silicone compatible cross-linkers for controlled functionalization of PDMS networks

    DEFF Research Database (Denmark)

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


    Polydimethylsiloxane (PDMS) elastomers are excellent materials for dielectric electroactive polymers (DEAPs) due to their high efficiency and fast response. PDMS suffers, however, from low dielectric permittivity and high voltages are therefore required when the material is used for DEAP actuators...

  20. Surface morphology of PS-PDMS diblock copolymer films

    DEFF Research Database (Denmark)

    Andersen, T.H.; Tougaard, S.; Larsen, N.B.


    Spin coated thin films (∼400 Å) of poly(styrene)–poly(dimethylsiloxane) (PS–PDMS) diblock copolymers have been investigated using X-ray Photoelectron Spectroscopy and Atomic Force Microscopy. Surface segregation of the poly(dimethylsiloxane) blocks was studied for five diblock copolymers which...

  1. Modular microfluidic systems using reversibly attached PDMS fluid control modules

    DEFF Research Database (Denmark)

    Skafte-Pedersen, Peder; Sip, Christopher G.; Folch, Albert;


    The use of soft lithography-based poly(dimethylsiloxane) (PDMS) valve systems is the dominating approach for high-density microscale fluidic control. Integrated systems enable complex flow control and large-scale integration, but lack modularity. In contrast, modular systems are attractive altern...

  2. Investigation of PDMS as coating on CMUTs for Imaging

    DEFF Research Database (Denmark)

    la Cour, Mette Funding; Stuart, Matthias Bo; Laursen, Mads Bjerregaard;


    A protective layer is necessary for Capacitive Mi- cromachined Ultrasonic Transducers (CMUTs) to be used for imaging purpose. The layer should both protect the device itself and the patient while maintaining the performance of the device. In this work Sylgard 170 PDMS is tested as coating material...

  3. Embedded Acoustic Black Holes for semi-passive broadband vibration attenuation in thin-walled structures (United States)

    Zhao, Liuxian; Semperlotti, Fabio


    We explore the use of structure-embedded Acoustic Black Holes (ABH) to design thin-walled structural components exhibiting broadband vibration attenuation characteristics. The ABH is a geometric taper with a power-law profile fully integrated into the structural component and able to induce a smooth and progressive decrease of both the velocity and the wavelength of flexural waves. Previous studies have shown these characteristics to be critical to enable highly efficient vibration attenuation systems. The performance of ABH thin-walled structures is numerically and experimentally evaluated under both transient and steady state excitation conditions. Both numerical and experimental results suggest that the proposed approach enables highly efficient and broadband vibration attenuation performance.

  4. Bacterial community structure and diversity in a black soil as affected by long-term fertilization

    Institute of Scientific and Technical Information of China (English)

    WEI Dan; YANG Qian; ZHANG Jun-Zheng; WANG Shuang; CHEN Xue-Li; ZHANG Xi-Lin; LI Wei-Qun


    Black soil (Mollisol) is one of the main soil types in northeastern China.Biolog and polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) methods were used to examine the influence of various fertilizer combinations on the structure and function of the bacterial community in a black soil collected from Harbin,Heilongjiang Province.Biolog results showed that substrate richness and catabolic diversity of the soil bacterial community were the greatest in the chemical fertilizer and chemical fertilizer+manure treatments.The metabolic ability of the bacterial community in the manure treatment was similar to the control.DGGE fingerprinting indicated similarity in the distribution of most 16S rDNA bands among all treatments,suggesting that microorganisms with those bands were stable and not influenced by fertilization.However,chemical fertilizer increased the diversity of soil bacterial community.Principal component analysis of Biolog and DGGE data revealed that the structure and function of the bacterial community were similar in the control and manure treatments,suggesting that the application of manure increased the soil microbial population,but had no effect on the bacterial community structure.Catabolic function was similar in the chemical fertilizer and chemical fertilizer+manure treatments,but the composition structure of the soil microbes differed between them.The use of chemical fertilizers could result in a decline in the catabolic activity of fast-growing or eutrophic bacteria.

  5. Air-spaced PDMS piezo-electret cantilevers for vibration energy harvesting (United States)

    Kachroudi, A.; Basrour, S.; Rufer, L.; Jomni, F.


    This paper reports a design of a new prototype of air-spaced cantilevers made from a micro-structured PDMS piezo-electret material for accelerometer and energy harvesting applications. The test performed on these cantilevers in a sensor mode exhibits a stable sensitivity of 385 mV/g for a frequency ranging from 5 Hz to 200 Hz that encompass most macro-scale vibrations. In the energy harvesting mode, the cantilever generates a power of 103 nW with a load resistance of 217 MΩ.

  6. PDMS and MWCNT – How to Obtain an Efficient and Controlled Distribution of Conductive Fillers in PDMS

    DEFF Research Database (Denmark)

    Hassonueh, S. S.; Goswami, Kaustav; Skov, Anne Ladegaard

    by traditional preparation of the crosslinked elastomer. Both pathways have been investigated and the presentation will outline results from both approaches. Direct processing of the MWCNT together with PDMS prepolymers by mechanical mixing, sonication, speedmixing or roll milling have been investigated...

  7. [Cloning and structure of gene encoded alpha-latrocrustoxin from the Black widow spider venom]. (United States)

    Danilevich, V N; Luk'ianov, S A; Grishin, E V


    The primary structure of the crusta gene encoding alpha-latrocrustoxin (alpha-LCT), a high molecular mass neurotoxin specific to crustaceans, was determined in the black widow spider Latrodectus mactans tredicimguttatus genome. The total length of the sequenced DNA was 4693 bp. The structural part of the black widow spider chromosome gene encoding alpha-LCT does not contain introns. The sequenced DNA contains a single extended open reading frame (4185 bp) and encodes a protein precursor of alpha-LCT, comprising 1395 aa. We assume the Met residue at position -10 relative to the N-terminal residue of Glu1 of the mature toxin to be the first one in the protein precursor. The calculated molecular mass of the precursor (156147 Da) exceeds that of the mature toxin by approximately 30 kDa. These data are in agreement with the notion that over the course of maturation the protein precursor undergoes double processing--cleavage of a decapeptide from the N-terminal part and of a approximately 200-aa fragment from the C-terminal part. alpha-LCT displayed a number of imperfect ankyrin-like repeats and areas of structural homology with earlier studied latrotoxins; the highest homology degree (62%) was revealed with alpha-latroinsectotoxin (alpha-LIT).

  8. Holographic entanglement entropy and the extended phase structure of STU black holes

    CERN Document Server

    Caceres, Elena; Pedraza, Juan F


    We study the extended thermodynamics, obtained by considering the cosmological constant as a thermodynamic variable, of STU black holes in 4-dimensions in the fixed charge ensemble. The associated phase structure is conjectured to be dual to an RG-flow on the space of field theories. We find that for some charge configurations the phase structure resembles that of a Van der Waals gas: the system exhibits a family of first order phase transitions ending in a second order phase transition at a critical temperature. We calculate the holographic entanglement entropy for several charge configurations and show that for the cases where the gravity background exhibits Van der Waals behavior, the entanglement entropy presents a transition at the same critical temperature. To further characterize the phase transition we calculate appropiate critical exponents show that they coincide. Thus, the holographic entanglement entropy successfully captures the information of the extended phase structure. Finally, we discuss the...

  9. The primary structure of a short neurotoxin homologue from Dendroaspis polylepis polylepis (Black mamba venom

    Directory of Open Access Journals (Sweden)

    F. J. Joubert


    Full Text Available Toxin CM-7 was purified from black mamba venom by gel filtration on Sephadex G-50 followed by ion exchange chromotography on CM-cellulose. It contains 60 amino acids, including eight half-cystines. The complete amino acid sequence of toxin CM-7 has been elucidated. In toxin CM-7 the eleven structurally invariant amino acids of the neurotoxins and cardiotoxins are conserved, but it has only one of the five functionally invariant amino acids of the neurotoxins. The eight cysteine residues of toxin CM-7 are in the same locations as those in short neurotoxins of known structures and are presumed to be similarly cross-linked. The sequence of CM-7 is structurally homologous with the short neurotoxins, but it is less toxic.

  10. Black holes in binary stars

    NARCIS (Netherlands)

    Wijers, R.A.M.J.


    Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes

  11. Carbon doped PDMS: conductance stability over time and implications for additive manufacturing of stretchable electronics (United States)

    Tavakoli, Mahmoud; Rocha, Rui; Osorio, Luis; Almeida, Miguel; de Almeida, Anibal; Ramachandran, Vivek; Tabatabai, Arya; Lu, Tong; Majidi, Carmel


    Carbon doped PDMS (cPDMS), has been used as a conductive polymer for stretchable electronics. Compared to liquid metals, cPDMS is low cost and is easier to process or to print with an additive manufacturing process. However, changes on the conductance of the carbon based conductive PDMS (cPDMS) were observed over time, in particular after integration of cPDMS and the insulating polymer. In this article we investigate the process parameters that lead to improved stability over conductance of the cPDMS over time. Slight modifications to the fabrication process parameters were conducted and changes on the conductance of the samples for each method were monitored. Results suggested that change of the conductance happens mostly after integration of a pre-polymer over a cured cPDMS, and not after integration of the cPDMS over a cured insulating polymer. We show that such changes can be eliminated by adjusting the integration priority between the conductive and insulating polymers, by selecting the right curing temperature, changing the concentration of the carbon particles and the thickness of the conductive traces, and when possible by changing the insulating polymer material. In this way, we obtained important conclusions regarding the effect of these parameters on the change of the conductance over time, that should be considered for additive manufacturing of soft electronics. Also, we show that these changes can be possibly due to the diffusion from PDMS into cPDMS.

  12. Structural and sensory characterization of key pungent and tingling compounds from black pepper (Piper nigrum L.). (United States)

    Dawid, Corinna; Henze, Andrea; Frank, Oliver; Glabasnia, Anneke; Rupp, Mathias; Büning, Kirsten; Orlikowski, Diana; Bader, Matthias; Hofmann, Thomas


    To gain a more comprehensive knowledge on whether, besides the well-known piperine, other compounds are responsible for the pungent and tingling oral impression imparted by black pepper, an ethanol extract prepared from black pepper (Piper nigrum L.) was screened for its key sensory-active nonvolatiles by application of taste dilution analysis (TDA). Purification of the compounds perceived with the highest sensory impact, followed by LC-MS and 1D/2D NMR experiments as well as synthesis, led to the structure determination of 25 key pungent and tingling phytochemicals, among which the eight amides 1-(octadeca-2E,4E,13Z-trienyl)piperidine, 1-(octadeca-2E,4E,13Z-trienyl)pyrrolidine, (2E,4E,13Z)-N-isobutyl-octadeca-2,4,13-trienamide, 1-(octadeca-2E,4E,12Z-trienoyl)-pyrrolidine, 1-(eicosa-2E,4E,15Z-trienyl)piperidine, 1-(eicosa-2E,4E,15Z-trienyl)pyrrolidine, (2E,4E,15Z)-N-isobutyl-eicosa-2,4,15-trienamide, and 1-(eicosa-2E,4E,14Z-trienoyl)-pyrrolidine were not yet reported in literature. Sensory studies by means of a modified half-tongue test revealed recognition thresholds ranging from 3.0 to 1150.2 nmol/cm² for pungency and from 520.6 to 2162.1 nmol/cm² for the tingling orosensation depending on their chemical structure.

  13. Design and fabrication of microfluidic mixer from carbonyl iron–PDMS composite membrane

    KAUST Repository

    Li, Jiaxing


    This paper introduces a carbonyl iron-PDMS (CI-PDMS) composite magnetic elastomer in which carbonyl iron (CI) particles are uniformly distributed in a PDMS matrix. The CI particles and the PDMS were mixed at different weight ratios and tested to determine the influence of CI concentration. The magnetic and mechanical properties of the magnetic elastomers were characterized, respectively, by vibrating-sample magnetometer and by tensile testing using a mechanical analyzer. The elastomer was found to exhibit high magnetization and good mechanical flexibility. The morphology and deformation of the CI-PDMS membrane also were observed. A magnetically actuated microfluidic mixer (that is, a micromixer) integrated with CI-PDMS elastomer membranes was successfully designed and fabricated. The high efficiency and quality of the mixing makes possible the impressive potential applications of this unique CI-PDMS material in microfluidic systems. © Springer-Verlag 2010.

  14. Control of PDMS crosslinking by encapsulating a hydride crosslinker in a PMMA microcapsule

    DEFF Research Database (Denmark)

    Ma, Baoguang; Hansen, Jens Henrik; Hvilsted, Søren;


    crosslinker in a PMMA shell. Microcapsules are mixed with vinyl-terminated PDMS to create a gelation system, which allows for storage at 50 °C, without premature gelation, and in addition allows for extensive crosslinking reaction at 120 °C. Both visual observations and rheological studies show that a robust...... PDMS elastomer is obtained upon heating the gelation system. Furthermore, the influence of stoichiometric imbalance on the equilibrium storage modulus of the PDMS network is investigated, by employing different amounts of microcapsules in vinyl-terminated PDMS. It has been found that adding...... microcapsules increases the equilibrium storage modulus of the PDMS elastomer until the diffusion of the hydride crosslinker is constricted. An optimum amount of crosslinker used in the control crosslinking reaction has also been found. However, compared to the pure PDMS elastomer, the modulus of the PDMS...

  15. Mesomorphic phase behaviour of low molar mass PEP-PDMS diblock copolymers synthesized by anionic polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Vigild, M.E.


    The phase behaviour of low molar mass poly(ethylene-alt-propylene) -poly(dimethylsiloxane) (PEP-PDMS) is investigated in this thesis by the combination of dynamical mechanical spectroscopy (rheology) to measure phase transition temperatures, and small-angle x-ray scattering to identify the morphology of encountered phases. Samples of PEP-PDMS in the range of 0.2-0.7 in volume fraction of PEP are studied. This diblock copolymer system exhibits the three classical phases of lamellar sandwich structure (LAM), hexagonally packed cylinders (HEX), and spheres arranged on a body centered cubic lattice (BCC). Furthermore the gyroid phase (Ia3d symmetry) of two interpenetrating networks was also identified as a stable phase of the PEP-PDMS system. Time resolved measurements of small-angle neutron scattering in tandem with simultaneous in-situ rheological measurements are performed on samples showing transitions between different ordered phases. The identification of especially the BCC and gyroid phases from scattering experiments is treated. By performing mesoscopic crystallographic measurements using a custom built goniometer it was unambiguously shown that the application of shear to an unoriented powder-like sample introduces uniaxial orientation of the gyroid phase. The orientation of the ordered phase is otherwise random, causing a two-dimensional powder. Finally this dissertation presents a discussion of relevant parameters for the description of diblock copolymer phase behaviour together with descriptions of anionic polymerization for the synthesis of copolymers, and various experimental techniques for the characterization of diblocks. (au). 9 tabs., 40 ills., 81 refs.


    Directory of Open Access Journals (Sweden)

    Lychman V. A.


    Full Text Available The results of a long-term research of the influence of various biologically active agents (a humic preparation Lignogumat and microbiological Baikal EM fertilizer on a structural state and the enzymatic activity of ordinary carbonated black soil are presented. It has been established that biologically active substances contribute to increased enzymatic activity, humus and improve the soil structure

  17. Loss of acoustic black hole effect in a structure of finite size (United States)

    Tang, Liling; Cheng, Li


    The Acoustic Black Hole (ABH) effect takes place in thin-walled structures with diminishing thickness as a result of the reduction in the bending wave speed. It was shown to exist as a broadband phenomenon, based on wave propagation theory in structures of semi-infinite size. The ABH effect exhibits appealing features for various applications, such as passive vibration control, energy harvesting, and sound radiation control. In this paper, we demonstrate the disappearance of the ABH effect in a finite beam at specific frequency ranges above the cut-on frequency, both experimentally and theoretically. Analyses show that the phenomenon takes place at frequencies which are close to the low order local resonant frequencies of the portion of the beam demarcated by the position of the excitation force. These frequencies can be predicted so that the phenomenon can be avoided for the targeted frequency ranges in ABH applications.

  18. Maps Showing Geology, Structure, and Geophysics of the Central Black Hills, South Dakota (United States)

    Redden, Jack A.; DeWitt, Ed


    This 1:100,000-scale digital geologic map details the complex Early Proterozoic granitic rocks, Early Proterozoic supracrustal metamorphic rocks, and Archean crystalline basement of the Black Hills. The granitic rocks host pegmatite deposits renowned for their feldspar, mica, spodumene, and beryl. The supracrustal rocks host the Homestake gold mine, which produced more than 40 million ounces of gold over a 125-year lifetime. The map documents the Laramide deformation of Paleozoic and Mesozoic cover rocks; and shows the distribution of Laramide plutonic rocks associated with precious-metals deposits. Four 1:300,000-scale maps summarize Laramide structures; Early Proterozoic structures; aeromagnetic anomalies; and gravity anomalies. Three 1:500,000-scale maps show geophysical interpretations of buried Early Proterozoic to Archean rocks in western South Dakota and eastern Wyoming.

  19. Modeling angle-resolved photoemission of graphene and black phosphorus nano structures. (United States)

    Park, Sang Han; Kwon, Soonnam


    Angle-resolved photoemission spectroscopy (ARPES) data on electronic structure are difficult to interpret, because various factors such as atomic structure and experimental setup influence the quantum mechanical effects during the measurement. Therefore, we simulated ARPES of nano-sized molecules to corroborate the interpretation of experimental results. Applying the independent atomic-center approximation, we used density functional theory calculations and custom-made simulation code to compute photoelectron intensity in given experimental setups for every atomic orbital in poly-aromatic hydrocarbons of various size, and in a molecule of black phosphorus. The simulation results were validated by comparing them to experimental ARPES for highly-oriented pyrolytic graphite. This database provides the calculation method and every file used during the work flow.

  20. Numerical modeling of roll structures in mesoscale vortexes over the Black Sea

    CERN Document Server

    Iarova, D A


    This paper is a case study of horizontal atmospheric rolls that formed over the Black Sea on 16 August 2007. The rolls were discovered in WRF modeling results for a mesoscale cyclone that originated over the sea on 15 August 2007. The roll formation mechanisms, such as Rayleigh-Benard convective instability, dynamic instability, advection and stretching of vertical velocity field inhomogeneities, are considered. It is shown that indeed convective instability played an important role in the roll formation but dynamic instability did not occur. In order to distinguish other possible mechanisms of the roll formation numerical experiments were performed. In these experiments sea surface temperature in the initial conditions was decreased in order to prevent convective instability. Even though convective instability was suppressed roll-like structures still appeared in the modeling results, although their height and circulation velocity were smaller than in the control run. It was found that these structures were ...

  1. Growth control of sessile microbubbles in PDMS devices

    CERN Document Server

    Volk, Andreas; Kähler, Christian J; Hilgenfeldt, Sascha; Marin, Alvaro


    In a microfluidic environment, the presence of bubbles is often detrimental to the functionality of the device, leading to clogging or cavitation, but microbubbles can also be an indispensable asset in other applications such as microstreaming. In either case, it is crucial to understand and control the growth or shrinkage of these bodies of air, in particular in common soft-lithography devices based on polydimethylsiloxane (PDMS), which is highly permeable to gases. In this work, we study the gas transport into and out of a bubble positioned in a microfluidic device, taking into account the direct gas exchange through PDMS as well as the transport of gas through the liquid in the device. Hydrostatic pressure regulation allows for the quantitative control of growth, shrinkage, or the attainment of a stable equilibrium bubble size. We find that the vapor pressure of the liquid plays an important role for the balance of gas transport, accounting for variability in experimental conditions and suggesting addition...

  2. Soft and flexible conductive PDMS/MWCNT composites

    DEFF Research Database (Denmark)

    Hassouneh, Suzan Sager; Yu, Liyun; Skov, Anne Ladegaard;


    Conductive elastomers based on MWCNT in polydimethylsiloxane (PDMS) have been prepared by a range of dispersion methods such as ultrasonication, speedmixing and roll milling in combination with physical or covalent modification. The ionic liquid (IL), 1-ethyl-3-methylimidazolium bis(trifluorometh......Conductive elastomers based on MWCNT in polydimethylsiloxane (PDMS) have been prepared by a range of dispersion methods such as ultrasonication, speedmixing and roll milling in combination with physical or covalent modification. The ionic liquid (IL), 1-ethyl-3-methylimidazolium bis...... in conductivity was observed, which was attributed to a change in morphology occurring between 4 and 5 wt % MWCNT. As an alternative to IL dispersing aids a novel functionalized MWCNT was prepared by free radical polymerization using α-methacryloxypropyl-polydimethylsiloxane, which could be used directly...


    Institute of Scientific and Technical Information of China (English)

    Yi-cai Zhu; Xiao-hong Zhang; Jin-liang Qiao; Gen-shuan Wei


    Polydimethylsiloxane (PDMS) rubber latex with two sorts of sensitizers, trimethylol propane tri-methacrylate (TMPTMA) and diethylene glycol di-acrylate (DEGDA), was irradiated with γ-rays and electron beams in various conditions.The radiation crosslinking reaction of PDMS occurs in the inner phase of the latex and is relatively isolated from the water phase. Therefore the oxygen and the radicals produced by the radiolysis reaction of water almost have no effect on the crosslinking reaction of polymer. The experimental data correspond with the Charlesby-Pinner relationship in the main. The gelation doses, degree of crosslinking and degradation as well as G values of crosslinking were calculated. From them, the sensitization coefficients were derived to offer a quantitative measurement of the enhancing effect of sensitizer on the radiation crosslinking.

  4. Fabrication and characterization of phantoms made of polydimethylsiloxane (PDMS) (United States)

    Villanueva-Luna, A. E.; Santiago-Alvarado, A.; Castro-Ramos, J.; Licona-Moran, B.; Vazquez-Montiel, S.; Flores-Gil, A.; Delgado-Atencio, J. A.


    The transparent elastomer Polydimethylsiloxane (PDMS) Sylgard 184 is increasingly used in optical applications, as in the manufacture of microlens, waveguides (optical fibers) and to elaborated phantoms (simulator of biological tissue); The wide range of applications is due to its excellent physic-chemical properties, its low cost, easy operation and null toxicity. This paper describes the manufacturing process and physic-chemical characterization of Phantoms prepared with PDMS as grid and doped with some elements present as Gliceryl, ink, glucose 10% and melanin provided by sigma aldrich. We made phantoms with different concentrations and elements; we measured their profiles, and thicknesses. Finally, we obtained their Raman Spectra. We present the experimental results obtained of the physic-chemical parameters of the phantoms and the conclusions.

  5. Parametric and scattering characterization of PDMS membranes for optical applications (United States)

    Santiago-Alvarado, A.; Vazquez Montiel, S.; Munoz-Lopez, J.; Castro-Ramos, J.; Delgado Atencio, J. A.


    Today elastic membranes are being used more frequent as optical surfaces in the science or in the industry. This due to the advantages that they display in their handling and in their cost of production. These characteristics make them ideals to apply them in micro-optical components and Tunable Focus Liquid Filled Length Lens (TFLFLL). In order to know if a membrane of PDMS (PDMS Sylgard 184) is feasible for a specific application within the field of the optics, it is necessary to know its mechanical, optical and chemical properties. In this work the parametric membrane characterization is reported for an optical application. An important factor in the performance of these membranes is related with their scattering factor that is produced due to the roughness and impurities (micro-bubbles or dust particles). These membranes are used as refractive surface in TFLFLL. Experimental results of the characterization process and device performance are presented.

  6. Engineers are from PDMS-land, Biologists are from Polystyrenia. (United States)

    Berthier, Erwin; Young, Edmond W K; Beebe, David


    As the integration of microfluidics into cell biology research proceeds at an ever-increasing pace, a critical question for those working at the interface of both disciplines is which device material to use for a given application. While PDMS and soft lithography methods offer the engineer rapid prototyping capabilities, PDMS as a material has characteristics that have known adverse effects on cell-based experiments. In contrast, while polystyrene (PS), the most commonly used thermoplastic for laboratory cultureware, has provided decades of grounded and validated research conclusions in cell behavior and function, PS as a material has posed significant challenges in microfabrication. These competing issues have forced microfluidics engineers and biologists to make compromises in how they approach specific research questions, and furthermore, have attenuated the impact of microfluidics on biological research. In this review, we provide a comparison of the attributes of PDMS and PS, and discuss reasons for their popularity in their respective fields. We provide a critical evaluation of the strengths and limitations of PDMS and PS in relation to the advancement and future impact on microfluidic cell-based studies and applications. We believe that engineers have a responsibility to overcome any challenges associated with microfabrication, whether with PS or other materials, and that engineers should provide options and solutions that assist biologists in their experimental design. Our goal is not to advocate for any specific material, but provide guidelines for researchers who desire to choose the most suitable material for their application, and suggest important research directions for engineers working at the interface between microfabrication technology and biological application.

  7. Discovery of Black Dye Crystal Structure Polymorphs: Implications for Dye Conformational Variation in Dye-Sensitized Solar Cells. (United States)

    Cole, Jacqueline M; Low, Kian Sing; Gong, Yun


    We present the discovery of a new crystal structure polymorph (1) and pseudopolymorph (2) of the Black Dye, one of the world's leading dyes for dye-sensitized solar cells, DSSCs (10.4% device performance efficiency). This reveals that Black Dye molecules can adopt multiple low-energy conformers. This is significant since it challenges existing models of the Black Dye···TiO2 adsorption process that renders a DSSC working electrode; these have assumed a single molecular conformation that refers to the previously reported Black Dye crystal structure (3). The marked structural differences observed between 1, 2, and 3 make the need for modeling multiple conformations more acute. Additionally, the ordered form of the Black Dye (1) provides a more appropriate depiction of its anionic structure, especially regarding its anchoring group and NCS bonding descriptions. The tendency toward NCS ligand isomerism, evidenced via the disordered form 2, has consequences for electron injection and electron recombination in Black Dye embedded DSSC devices. Dyes 2 and 3 differ primarily by the absence or presence of a solvent of crystallization, respectively; solvent environment effects on the dye are thereby elucidated. This discovery of multiple Black Dye conformers from diffraction, with atomic-level definition, complements recently reported nanoscopic evidence for multiple dye conformations existing at a dye···TiO2 interface, for a chemically similar DSSC dye; those results emanated from imaging and spectroscopy, but were unresolved at the submolecular level. Taken together, these findings lead to the general notion that multiple dye conformations should be explicitly considered when modeling dye···TiO2 interfaces in DSSCs, at least for ruthenium-based dye complexes.

  8. Sub-100 nm gold nanohole-enhanced Raman scattering on flexible PDMS sheets (United States)

    Lee, Seunghyun; Ongko, Andry; Kim, Ho Young; Yim, Sang-Gu; Jeon, Geumhye; Jeong, Hee Jin; Lee, Seungwoo; Kwak, Minseok; Yang, Seung Yun


    Surface-enhanced Raman spectroscopy (SERS) is a highly sensitive vibrational spectroscopy technique enabling detection of multiple analytes at the molecular level in a nondestructive and rapid manner. In this work, we introduce a new approach to fabricate deep subwavelength-scaled (sub-100 nm) metallic nanohole arrays (quasi-3D metallic nanoholes) on flexible and highly efficient SERS substrates. Target structures have been fabricated using a two-step process consisting of (i) direct pattern transfer of spin-coated polymer films onto polydimethylsiloxane (PDMS) substrates by plasma etching with transferred anodic aluminum oxide masks, and (ii) producing SERS-active substrates by functionalization of the etched polymeric films followed by Au deposition. Such an all-dry, top-down lithographic approach enables on-demand patterning of SERS-active metallic nanoholes with high structural fidelity even onto flexible and stretchable substrates, thus making possible multiple sensing modes in a versatile fashion. For example, metallic nanoholes on flexible PDMS substrates are highly amenable to their integration with curved glass sticks, which can be used in optical fiber-integrated SERS systems. Au surfaces immobilized by probe DNA molecules show a selective enhancement of Raman scattering with Cy5-labeled complementary DNA (as compared to flat Au surfaces), demonstrating the potential of using the quasi-3D Au nanohole arrays for bio-sensing applications.

  9. Virion Structure of Black Queen Cell Virus, a Common Honeybee Pathogen (United States)

    Spurny, Radovan; Přidal, Antonín; Pálková, Lenka; Kiem, Hoa Khanh Tran; de Miranda, Joachim R.


    ABSTRACT Viral diseases are a major threat to honeybee (Apis mellifera) populations worldwide and therefore an important factor in reliable crop pollination and food security. Black queen cell virus (BQCV) is the etiological agent of a fatal disease of honeybee queen larvae and pupae. The virus belongs to the genus Triatovirus from the family Dicistroviridae, which is part of the order Picornavirales. Here we present a crystal structure of BQCV determined to a resolution of 3.4 Å. The virion is formed by 60 copies of each of the major capsid proteins VP1, VP2, and VP3; however, there is no density corresponding to a 75-residue-long minor capsid protein VP4 encoded by the BQCV genome. We show that the VP4 subunits are present in the crystallized virions that are infectious. This aspect of the BQCV virion is similar to that of the previously characterized triatoma virus and supports the recent establishment of the separate genus Triatovirus within the family Dicistroviridae. The C terminus of VP1 and CD loops of capsid proteins VP1 and VP3 of BQCV form 34-Å-tall finger-like protrusions at the virion surface. The protrusions are larger than those of related dicistroviruses. IMPORTANCE The western honeybee is the most important pollinator of all, and it is required to sustain the agricultural production and biodiversity of wild flowering plants. However, honeybee populations worldwide are suffering from virus infections that cause colony losses. One of the most common, and least known, honeybee pathogens is black queen cell virus (BQCV), which at high titers causes queen larvae and pupae to turn black and die. Here we present the three-dimensional virion structure of BQCV, determined by X-ray crystallography. The structure of BQCV reveals large protrusions on the virion surface. Capsid protein VP1 of BQCV does not contain a hydrophobic pocket. Therefore, the BQCV virion structure provides evidence that capsid-binding antiviral compounds that can prevent the

  10. Separating a water-propanol mixture using PDMS pervaporation membranes

    Directory of Open Access Journals (Sweden)

    Mahacine Amrani


    Full Text Available Recovering and purifying organic solvents during chemical and pharmaceutical synthesis has great economic and environmental importance. Water-alcohol mixture pervaporation was investigated using a pervaporation cell and hy-drophobic membranes. This work studied polydimethylsiloxane (PDMS membrane performance and hydrophobic membranes for removing propanol from aqueous mixtures. PDMS is recognised as being alcohol permselective du-ring pervaporation. It was also observed that water was transferred through a hydrophobic membrane as water’s molecular size is smaller than that of propanol. A laboratory-scale pervaporation unit was used for studying this membrane’s separation characteristics in terms of pervaporation flux and selectivity for feeds containing up to water mass and 30°C-50°C. Total propanol/water flux was observed to vary as operating temperature increased. Although PDMS membranes presented good characteristics for separating water/propanol mixtures, the separation factor and pervaporation flow decreased as water content in the feed increased. The tested membrane was found to be very e-fficient for water concentrations of less than 0.3, corresponding to total flux transfer maximum.

  11. Embedded silver PDMS electrodes for single cell electrical impedance spectroscopy (United States)

    Wei, Yuan; Xu, Zhensong; Cachia, Mark A.; Nguyen, John; Zheng, Yi; Wang, Chen; Sun, Yu


    This paper presents a microfluidic device with wide channels and embedded AgPDMS electrodes for measuring the electrical properties of single cells. The work demonstrates the feasibility of using a large channel design and embedded electrodes for impedance spectroscopy to circumvent issues such as channel clogging and limited device re-usability. AgPDMS electrodes were formed on channel sidewalls for impedance detection and cell electrical properties measurement. Equivalent circuit models were used to interpret multi-frequency impedance data to quantify each cell’s cytoplasm conductivity and specific membrane capacitance. T24 cells were tested to validate the microfluidic system and modeling results. Comparisons were then made by measuring two leukemia cell lines (AML-2 and HL-60) which were found to have different cytoplasm conductivity values (0.29  ±  0.15 S m-1 versus 0.47  ±  0.20 S m-1) and specific membrane capacitance values (41  ±  25 mF m-2 versus 55  ±  26 mF m-2) when the cells were flown through the wide channel and measured by the AgPDMS electrodes.

  12. Relationships between MODIS black-sky shortwave albedo and airborne lidar based forest canopy structure (United States)

    Korhonen, Lauri; Rautiainen, Miina; Arumäe, Tauri; Lang, Mait; Flewelling, James; Tokola, Timo; Stenberg, Pauline


    Albedo is one of the essential climate variables affecting the Earth's radiation balance. It is however not well understood how changes in forest canopy structure influence the albedo. Canopy structure can be mapped consistently for fairly large areas using airborne lidar sensors. Our objective was to study the relationships between MODIS shortwave black sky albedo product and lidar-based estimates of canopy structure in different biomes ranging from arctic to tropical. Our study is based on six structurally different forest sites located in Finland, Estonia, USA and Laos. Lidar-based mean height of the canopy, canopy cover and their transformations were used as predictor variables to describe the canopy structure. Tree species composition was also included for the three sites where it was available. We noticed that the variables predicting albedo best were different in open and closed canopy forests. In closed canopy forests, the species information was more important than canopy structure variables (R2=0.31-0.32) and using only structural variables resulted in poor R2 (0.13-0.15). If the 500 m MODIS pixel contained a mixture of forests and other land cover types, the albedo was strongly related to the forest area percent. In open canopy forests, structural variables such as canopy cover or height explained albedo well, but species information still improved the models (R2=0.27-0.52). We obtained the highest R2=0.52 using only structural variables in Laos on a partially degraded tropical forest with large variation in canopy cover. The different canopy structure variables were often correlated and the one that provided the best model changed from site to site.

  13. Preliminary study of the mite community structure in different black truffle producing soils

    Directory of Open Access Journals (Sweden)

    Mikel Queralt


    Full Text Available Aims of the study: The goals of this paper are to provide preliminary data on the composition of the mite community in truffle-producing soils (both wild and plantations; and to elucidate those species which may interact with the black truffle life cycle.Area of study: The study was carried out in two black truffle productive zones in Navarra (Spain, in four different plantations and five wild production areas.Material and Methods: Fauna was extracted using Berlese Tullgren funnels. Animals were separated into taxonomic groups, and mites were identified. To analyse the composition and community structure of the different habitats, parameters such as abundance, species richness, and Shanon Weiner diversity index (H’ were calculated.Main results: A total of 305 mites were recognized, belonging to 58 species representing the three major taxonomic groups (Oribatida, Prostigmata, Mesostigmata.Research highlights: The results show a possible trend towards wild areas having greater diversity and species richness than plantations. Furthermore, community analysis shows differences in species compositions among different study areas, and oribatid mites always exhibit the highest relative abundance and species richness.Keywords: Acari; Tuber melanosporum; Oribatida; Mesostigmata; Prostigmata; truffle orchards. 

  14. The Dimensions of Subjective Well-Being among Black Americans: A Structural Model Analysis. (United States)

    Tran, Thanh V.; And Others


    Analysis of data from 668 black adult respondents to the 1980 National Survey of Black Americans suggests that subjective well-being among black Americans is multidimensional. A three-factor model of subjective well-being encompassing strain (depressive symptoms), life satisfaction, and self-esteem was empirically supported and consistently…

  15. Differing patterns of brain structural abnormalities between black and white patients with their first episode of psychosis.

    LENUS (Irish Health Repository)

    Morgan, K D


    African-Caribbean and black African people living in the UK are reported to have a higher incidence of diagnosed psychosis compared with white British people. It has been argued that this may be a consequence of misdiagnosis. If this is true they might be less likely to show the patterns of structural brain abnormalities reported in white British patients. The aim of this study therefore was to investigate whether there are differences in the prevalence of structural brain abnormalities in white and black first-episode psychosis patients.

  16. Micropatterning of hydrogels on locally hydrophilized regions on PDMS by stepwise solution dipping and in situ gelation. (United States)

    Sugaya, Sari; Kakegawa, Shunta; Fukushima, Shizuka; Yamada, Masumi; Seki, Minoru


    This study presents a simple but highly versatile method of fabricating picoliter-volume hydrogel patterns on poly(dimethylsiloxane) (PDMS) substrates. Hydrophilic regions were prepared on hydrophobic PDMS plates by trapping and melting functional polymer particles and performing subsequent reactions with partially oxidized dextran. Small aliquots of a gelation solution were selectively trapped on the hydrophilic areas by a simple dipping process that was utilized to make thin hydrogel patterns by the in situ gelation of a sol solution. Using this process, we successfully formed calcium alginate, collagen I, and chitosan hydrogels with a thickness of several micrometers and shapes that followed the hydrophilized regions. In addition, alginate and collagen gel patterns were used to capture cells with different adhesion properties selectively on or off the hydrogel structures. The presented strategy could be applicable to the preparation of a variety of hydrogels for the development of functional biosensors, bioreactors, and cell cultivation platforms.

  17. A Method to Pattern Silver Nanowires Directly on Wafer-Scale PDMS Substrate and Its Applications. (United States)

    Chou, Namsun; Kim, Youngseok; Kim, Sohee


    This study describes a fabrication method of microsized AgNW patterns based on poly dimethylsiloxane (PDMS) substrate using a poly(p-xylylene) (parylene) stencil technique. Various patterns of AgNW conductive sheets were created on the wafer scale area in the forms of straight and serpentine lines, texts, and symbols, which dimensions ranged from a few tens of micrometers to hundreds of micrometers. We demonstrated the electrical performance of straight line and serpentine line patterned AgNW electrodes when subjected to mechanical strains. The gauge factor and stretchability ranged from 0.5 to 55.2 at 2% uniaxial strain and from 4.7 to 55.7%, respectively, depending on the shapes and structures of the AgNW electrodes. Using the developed AgNW patterning technique, we fabricated strain sensors to detect small body signals epidermally such as hand motion, eye blink and heart rate. Also, tactile sensors were fabricated and exhibited the sensitivity of 3.91 MPa(-1) in the pressure range lower than 50 kPa, and 0.28 MPa(-1) in the pressure range greater than 50 kPa up to 1.3 MPa. From these results, we concluded that the proposed technique enables the fabrication of reliable AgNW patterns on wafer-scale PDMS substrate and the potential applications for various flexible electronic devices.

  18. Black Hole or MECO? Decided by a Thin Luminous Ring Structure Deep Within Quasar Q0957

    CERN Document Server

    Schild, Rudolph E


    Optical, Infrared, X-ray, and radio wavelength studies of quasars are beginning to define the luminous quasar structure from techniques of reverberation and microlensing. An important result is that the inner quasar structure of the first identified gravitational lens, Q0957+561 A,B seems not to show the kind of structure expected for a supermassive black hole, but instead show a clean-swept interior region as due to the action of a magnetic propeller, just as expected for a MECO (Magnetic Eternally Collapsing Object) structure. Given the present state of the observations, the strongest model discriminant seems to be the existence of a thin luminous band around the inner edge of the accretion disc, at a distant radius ~ 70 R_g from the ~ 4 x 10^9 Mo central object. Since the existence of a clean magnetic propeller swept inner region ~70 R_g surrounded by a sharp ~ 1 R_g disc edge are the low-hard state spectral properties associated with a highly redshifted central MECO object, we are led to the conclusion th...

  19. Production of Structural Colors with High Contrast and Wide Viewing Angles from Assemblies of Polypyrrole Black Coated Polystyrene Nanoparticles. (United States)

    Yang, Xiaoming; Ge, Dengteng; Wu, Gaoxiang; Liao, Zhiwei; Yang, Shu


    Structural color with wide viewing angles has enormous potential applications in pigment, ink formulation, displays, and sensors. However, colors obtained from colloidal assemblies with low refractive index contrast or without black additives typically appear pale. Here, we prepare polypyrrole (PPy) black coated polystyrene (PS) nanoparticles and demonstrate well-defined colors with high color contrast and wide viewing angles under ambient light. Depending on the loading of pyrrole during polymerization, PPy nanogranules of different sizes and coverages are grafted to the surface of PS nanoparticles. The bumpy particles can self-assemble into quasi-amorphous arrays, resulting in low angle dependent structure colors under ambient light. The color can be tuned by the size of the PS nanoparticles, and the presence of the PPy black on PS nanoparticles enhances the color contrast by suppressing incoherent and multiple scattering.

  20. Characterization of the nanosized porous structure of black Si solar cells fabricated via a screen printing process

    Institute of Scientific and Technical Information of China (English)

    Tang Yehua; Fei Jianming; Cao Hongbin; Zhou Chunlan; Wang Wenjing; Zhou Su; Zhao Yan; Zhao Lei; Li Hailing; Yan Baojun; Chen Jingwei


    A silicon (Si) surface with a nanosized porous structure was formed via simple wet chemical etching catalyzed by gold (Au) nanoparticles on p-type Cz-Si (100).The average reflectivity from 300 to 1200 nm was less than 1.5%.Black Si solar cells were then fabricated using a conventional production process.The results reflected the output characteristics of the cells fabricated using different etching depths and emitter dopant profiles.Heavier dopants and shallower etching depths should be adopted to optimize the black Si solar cell output characteristics.The efficiency at the optimized etching time and dopant profile was 12.17%.However,surface passivation and electrode contact due to the nanosized porous surface structure are still obstacles to obtaining high conversion efficiency for the black Si solar cells.

  1. A two-fluid model for black-hole accretion flows: particle acceleration and disc structure (United States)

    Lee, Jason P.; Becker, Peter A.


    Hot, tenuous advection-dominated accretion flows around black holes are ideal sites for the Fermi acceleration of relativistic particles at standing shock waves in the accretion disc. Previous work has demonstrated that the shock-acceleration process can be efficient enough to power the observed, strong outflows in radio-loud active galaxies such as M87. However, the dynamical effect (back-reaction) on the flow, exerted by the pressure of the relativistic particles, has not been previously considered, and this effect can have a significant influence on the disc structure. We reexamine the problem by developing a new, two-fluid model for the structure of the accretion disc that includes the dynamical effect of the relativistic particle pressure, combined with the pressure of the background (thermal) gas. The new model is analogous to the two-fluid model of cosmic ray acceleration in supernova-driven shock waves. As part of the model, we also develop a new set of shock jump conditions, which are solved along with the hydrodynamic conservation equations to determine the structure of the accretion disc. The solutions include the formation of a mildly relativistic outflow (jet) at the shock radius, driven by the relativistic particles accelerated in the disc. One of our main conclusions is that in the context of the new two-fluid accretion model, global smooth (shock-free) solutions do not exist, and the disc must always contain a standing shock wave, at least in the inviscid case considered here.

  2. Optical properties of polydimethylsiloxane (PDMS) during nanosecond laser processing (United States)

    Stankova, N. E.; Atanasov, P. A.; Nikov, Ru. G.; Nikov, R. G.; Nedyalkov, N. N.; Stoyanchov, T. R.; Fukata, N.; Kolev, K. N.; Valova, E. I.; Georgieva, J. S.; Armyanov, St. A.


    This article presents experimental investigations of effects of the process parameters on the medical grade polydimethylsiloxane (PDMS) elastomer processed by laser source with irradiation at UV (266 and 355 nm), VIS (532 nm) and NIR (1064 nm). Systematic experiments are done to characterize how the laser beam parameters (wavelength, fluence, and number of pulses) affect the optical properties and the chemical composition in the laser treated areas. Remarkable changes of the optical properties and the chemical composition are observed. Despite the low optical absorption of the native PDMS for UV, VIS and NIR wavelengths, successful laser treatment is accomplished due to the incubation process occurring below the polymer surface. With increasing of the fluence and the number of the pulses chemical transformations are revealed in the entire laser treated area and hence decreasing of the optical transmittance is observed. The incubation gets saturation after a certain number of pulses and the laser ablation of the material begins efficiently. At the UV and VIS wavelengths the number of the initial pulses, at which the optical transmittance begins to reduce, decreases from 16 up to 8 with increasing of the laser fluence up to 1.0, 2.5 and 10 J cm-2 for 266, 355 and 532 nm, respectively. In the case of 1064 nm the optical transmittance begins to reduce at 11th pulse incident at a fluence of 13 J cm-2 and the number of the pulses decreases to 8 when the fluence reaches value of 16 J cm-2. The threshold laser fluence needed to induce incubation process after certain number of pulses of 8 is different for every wavelength irradiation as the values increase from 1.0 for 266 nm up to 16 J cm-2 for 1064 nm. The incubation and the ablation processes occur in the PDMS elastomer material during its pulsed laser treatment are a complex function of the wavelength, fluence, number of pulses and the material properties as well.

  3. Simple, rapid and, cost-effective fabrication of PDMS electrophoresis microchips using poly(vinyl acetate) as photoresist master. (United States)

    Lobo-Júnior, Eulício O; Gabriel, Ellen F M; Dos Santos, Rodrigo A; de Souza, Fabrício R; Lopes, Wanderson D; Lima, Renato S; Gobbi, Angelo L; Coltro, Wendell K T


    This study describes a simple, rapid, and cost-effective fabrication of PDMS electrophoresis microchips using poly(vinyl acetate) (PVAc) emulsion as photoresist master. High-relief microfluidic structures were defined on poly(vinyl acetate) previously deposited on printed circuit boards surfaces without cleanroom facilities and sophisticated instrumentation. After a UV exposure, channels with heights ranging from 30 to 140 μm were obtained by controlling the emulsion mass deposited on the master surface. The developing stage was performed using water rather than the organic solvents that are applied for conventional masks. The surface morphology was characterized by optical imaging, profilometry, and SEM. Based on the achieved results, the proposed method offers suitable reproducibility for the prototyping of electrophoresis microchips in PDMS. The feasibility of the resulting PDMS electrophoresis chips was successfully demonstrated with the separation of major inorganic cations within 100 s using a contactless conductivity detection system. The separation efficiencies ranged from ca. 67 900 to 125 600 plates/m. Due to the satisfactory performance and simplified instrumentation, we believe this fabrication protocol presents potential to be implemented in any chemical, biochemical, or biological laboratory.

  4. Design and microfabrication of a high-aspect-ratio PDMS microbeam array for parallel nanonewton force measurement and protein printing (United States)

    Sasoglu, F. M.; Bohl, A. J.; Layton, B. E.


    Cell and protein mechanics has applications ranging from cellular development to tissue engineering. Techniques such as magnetic tweezers, optic tweezers and atomic force microscopy have been used to measure cell deformation forces of the order of piconewtons to nanonewtons. In this study, an array of polymeric polydimethylsiloxane (PDMS) microbeams with diameters of 10-40 µm and lengths of 118 µm was fabricated from Sylgard® with curing agent concentrations ranging from 5% to 20%. The resulting spring constants were 100-300 nN µm-1. The elastic modulus of PDMS was determined experimentally at different curing agent concentrations and found to be 346 kPa to 704 kPa in a millimeter-scale array and ~1 MPa in a microbeam array. Additionally, the microbeam array was used to print laminin for the purpose of cell adhesion. Linear and nonlinear finite element analyses are presented and compared to the closed-from solution. The highly compliant, transparent, biocompatible PDMS may offer a method for more rapid throughput in cell and protein mechanics force measurement experiments with sensitivities necessary for highly compliant structures such as axons.

  5. Rapid prototyping of microfluidic systems using a PDMS/polymer tape composite. (United States)

    Kim, Jungkyu; Surapaneni, Rajesh; Gale, Bruce K


    Rapid prototyping of microfluidic systems using a combination of double-sided tape and PDMS (polydimethylsiloxane) is introduced. PDMS is typically difficult to bond using adhesive tapes due to its hydrophobic nature and low surface energy. For this reason, PDMS is not compatible with the xurography method, which uses a knife plotter and various adhesive coated polymer tapes. To solve these problems, a PDMS/tape composite was developed and demonstrated in microfluidic applications. The PDMS/tape composite was created by spinning it to make a thin layer of PDMS over double-sided tape. Then the PDMS/tape composite was patterned to create channels using xurography, and bonded to a PDMS slab. After removing the backing paper from the tape, a complete microfluidic system could be created by placing the construct onto nearly any substrate; including glass, plastic or metal-coated glass/silicon substrates. The bond strength was shown to be sufficient for the pressures that occur in typical microfluidic channels used for chemical or biological analysis. This method was demonstrated in three applications: standard microfluidic channels and reactors, a microfluidic system with an integrated membrane, and an electrochemical biosensor. The PDMS/tape composite rapid prototyping technique provides a fast and cost effective fabrication method and can provide easy integration of microfluidic channels with sensors and other components without the need for a cleanroom facility.

  6. Full elastic constitutive relation of non-isotropic aligned-CNT/PDMS flexible nanocomposites (United States)

    Sepúlveda, A. T.; Guzman de Villoria, R.; Viana, J. C.; Pontes, A. J.; Wardle, B. L.; Rocha, L. A.


    The elastic response of vertically aligned-carbon nanotube/polydimethylsiloxane (A-CNT/PDMS) nanocomposites is presented in this study and related to the underlying aligned-CNT morphology. Multiwalled carbon nanotubes (MWCNTs) at 1% Vf are embedded in a flexible substrate of PDMS to create a flexible polymer nanocomposite (PNC). The PNC properties are evaluated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile mechanical tests, and the full linearly elastic constitutive relation is established for such a PNC. The results suggest that the CNTs retain the alignment after wetting and curing of PDMS. PDMS is significantly modified by the reinforcing aligned-CNT fibers, demonstrating non-isotropic (as opposed to the isotropic neat PDMS) elastic properties all different from PDMS (Young's modulus of 0.8 MPa), including an anisotropy ratio of 4.8 and increases in the modulus of A-CNT/PDMS over PDMS by more than 900% and 100%, in the CNT longitudinal and transverse directions, respectively. This study reports the first full constitutive relation that may be useful in modeling PNCs as composites or as elements of hierarchical nanoengineered composites, particularly PDMS-CNT PNCs are envisioned as elements in biomedical devices such as pressure transducers and energy harvesters.

  7. Rapid selective metal patterning on polydimethylsiloxane (PDMS) fabricated by capillarity-assisted laser direct write

    KAUST Repository

    Lee, Ming-Tsang


    In this study we demonstrate a novel approach for the rapid fabricating micro scale metal (silver) patterning directly on a polydimethylsiloxane (PDMS) substrate. Silver nanoparticles were sintered on PDMS to form conductive metal films using laser direct write (LDW) technology. To achieve good metal film quality, a capillarity-assisted laser direct writing (CALDW) of nanoparticle suspensions on a low surface energy material (PDMS) was utilized. Experimental results showed controllable electrical conductivities and good film properties of the sintered silver patterns. This study reveals an advanced method of metal patterning on PDMS, and proposes a new research application of LDW in a nanoparticle colloidal environment. © 2011 IOP Publishing Ltd.

  8. Investigation on the mechanism of nitrogen plasma modified PDMS bonding with SU-8

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chengxin; Yuan, Yong J., E-mail:


    Graphical abstract: - Highlights: • Different nitrogen plasma processes modified PDMS bonding with SU-8 had been studied. • The effect of nitrogen plasma modification would produce the best result and the recovery of PDMS hydrophobicity could be delayed. - Abstract: Polydimethylsiloxane (PDMS) and SU-8 are both widely used for microfluidic system. However, it is difficult to permanently seal SU-8 microfluidic channels using PDMS with conventional methods. Previous efforts of combining these two materials mainly employed oxygen plasma modified PDMS. The nitrogen plasma modification of PDMS bonding with SU-8 is rarely studied in recent years. In this work, the mechanism of nitrogen plasma modified PDMS bonding with SU-8 was investigated. The fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and contact angle of a water droplet were used to analyze the nitrogen plasma modified surface and the hydrophilic stability of PDMS samples. Pull-off tests were used for estimating the bonding effect of interface between nitrogen plasma modified PDMS and SU-8.

  9. Kinetic convex hulls, Delaunay triangulations and connectivity structures in the black-box model

    Directory of Open Access Journals (Sweden)

    Mark de Berg


    Full Text Available Over the past decade, the kinetic-data-structures framework has become thestandard in computational geometry for dealing with moving objects. A fundamental assumption underlying the framework is that the motions of the objects are known in advance. This assumption severely limits the applicability of KDSs. We study KDSs in the black-box model, which is a hybrid of the KDS model and the traditional time-slicing approach. In this more practical model we receive the position of each object at regular time steps and we have an upper bound on dmax, the maximum displacement of any point in one time step.We study the maintenance of the convex hull and the Delaunay triangulation of a planar point set P in the black-box model, under the following assumption on dmax: there is some constant k such that for any point p in P the disk of radius dmax contains at most k points. We analyze our algorithms in terms of Δk, the so-called k-spread of P. We show how to update the convex hull at each time step in O(min(n, kΔklog nlog n amortized time. For the Delaunay triangulation our main contribution is an analysis of the standard edge-flipping approach; we show that the number of flips is O(k2Δk2 at each time step.

  10. Dynamic molecular structure of plant biomass-derived black carbon (biochar)

    Energy Technology Data Exchange (ETDEWEB)

    Keiluweit, M.; Nico, P.S.; Johnson, M.G.; Kleber, M.


    Char black carbon (BC), the solid residue of incomplete combustion, is continuously being added to soils and sediments due to natural vegetation fires, anthropogenic pollution, and new strategies for carbon sequestration ('biochar'). Here we present a molecular-level assessment of the physical organization and chemical complexity of biomass-derived chars and, specifically, that of aromatic carbon in char structures. BET-N{sub 2} surface area, X-ray diffraction (XRD), synchrotron-based Near-edge X-ray Absorption Fine Structure (NEXAFS), and Fourier transform infrared (FT-IR) spectroscopy are used to show how two plant materials (wood and grass) undergo analogous, but quantitatively different physical-chemical transitions as charring temperature increases from 100 to 700 C. These changes suggest the existence of four distinct categories of char consisting of a unique mixture of chemical phases and physical states: (i) in transition chars the crystalline character of the precursor materials is preserved, (ii) in amorphous chars the heat-altered molecules and incipient aromatic polycondensates are randomly mixed, (iii) composite chars consist of poorly ordered graphene stacks embedded in amorphous phases, and (iv) turbostratic chars are dominated by disordered graphitic crystallites. The molecular variations among the different char categories translate into differences in their ability to persist in the environment and function as environmental sorbents.

  11. Population structure and genetic diversity of black redhorse (Moxostoma duquesnei) in a highly fragmented watershed (United States)

    Reid, S.M.; Wilson, C.C.; Mandrak, N.E.; Carl, L.M.


    Dams have the potential to affect population size and connectivity, reduce genetic diversity, and increase genetic differences among isolated riverine fish populations. Previous research has reported adverse effects on the distribution and demographics of black redhorse (Moxostoma duquesnei), a threatened fish species in Canada. However, effects on genetic diversity and population structure are unknown. We used microsatellite DNA markers to assess the number of genetic populations in the Grand River (Ontario) and to test whether dams have resulted in a loss of genetic diversity and increased genetic differentiation among populations. Three hundred and seventy-seven individuals from eight Grand River sites were genotyped at eight microsatellite loci. Measures of genetic diversity were moderately high and not significantly different among populations; strong evidence of recent population bottlenecks was not detected. Pairwise FST and exact tests identified weak (global FST = 0.011) but statistically significant population structure, although little population structuring was detected using either genetic distances or an individual-based clustering method. Neither geographic distance nor the number of intervening dams were correlated with pairwise differences among populations. Tests for regional equilibrium indicate that Grand River populations were either in equilibrium between gene flow and genetic drift or that gene flow is more influential than drift. While studies on other species have identified strong dam-related effects on genetic diversity and population structure, this study suggests that barrier permeability, river fragment length and the ecological characteristics of affected species can counterbalance dam-related effects. ?? 2007 Springer Science+Business Media B.V.

  12. Controlled Mechanical Cracking of Metal Films Deposited on Polydimethylsiloxane (PDMS

    Directory of Open Access Journals (Sweden)

    Andreas Polywka


    Full Text Available Stretchable large area electronics conform to arbitrarily-shaped 3D surfaces and enables comfortable contact to the human skin and other biological tissue. There are approaches allowing for large area thin films to be stretched by tens of percent without cracking. The approach presented here does not prevent cracking, rather it aims to precisely control the crack positions and their orientation. For this purpose, the polydimethylsiloxane (PDMS is hardened by exposure to ultraviolet radiation (172 nm through an exposure mask. Only well-defined patterns are kept untreated. With these soft islands cracks at the hardened surface can be controlled in terms of starting position, direction and end position. This approach is first investigated at the hardened PDMS surface itself. It is then applied to conductive silver films deposited from the liquid phase. It is found that statistical (uncontrolled cracking of the silver films can be avoided at strain below 35%. This enables metal interconnects to be integrated into stretchable networks. The combination of controlled cracks with wrinkling enables interconnects that are stretchable in arbitrary and changing directions. The deposition and patterning does not involve vacuum processing, photolithography, or solvents.

  13. Ethanol fermentation integrated with PDMS composite membrane: An effective process. (United States)

    Fu, Chaohui; Cai, Di; Hu, Song; Miao, Qi; Wang, Yong; Qin, Peiyong; Wang, Zheng; Tan, Tianwei


    The polydimethylsiloxane (PDMS) membrane, prepared in water phase, was investigated in separation ethanol from model ethanol/water mixture and fermentation-pervaporation integrated process. Results showed that the PDMS membrane could effectively separate ethanol from model solution. When integrated with batch ethanol fermentation, the ethanol productivity was enhanced compared with conventional process. Fed-batch and continuous ethanol fermentation with pervaporation were also performed and studied. 396.2-663.7g/m(2)h and 332.4-548.1g/m(2)h of total flux with separation factor of 8.6-11.7 and 8-11.6, were generated in the fed-batch and continuous fermentation with pervaporation scenario, respectively. At the same time, high titre ethanol production of ∼417.2g/L and ∼446.3g/L were also achieved on the permeate side of membrane in the two scenarios, respectively. The integrated process was environmental friendly and energy saving, and has a promising perspective in long-terms operation.

  14. Growth control of sessile microbubbles in PDMS devices. (United States)

    Volk, Andreas; Rossi, Massimiliano; Kähler, Christian J; Hilgenfeldt, Sascha; Marin, Alvaro


    In a microfluidic environment, the presence of bubbles is often detrimental to the functionality of the device, leading to clogging or cavitation, but microbubbles can also be an indispensable asset in other applications such as microstreaming. In either case, it is crucial to understand and control the growth or shrinkage of these bodies of air, in particular in common soft-lithography devices based on polydimethylsiloxane (PDMS), which is highly permeable to gases. In this work, we study the gas transport into and out of a bubble positioned in a microfluidic device, taking into account the direct gas exchange through PDMS as well as the transport of gas through the liquid in the device. Hydrostatic pressure regulation allows for the quantitative control of growth, shrinkage, or the attainment of a stable equilibrium bubble size. We find that the vapor pressure of the liquid plays an important role for the balance of gas transport, accounting for variability in experimental conditions and suggesting additional means of bubble size control in applications.

  15. Semi-contact-writing of polymer molds for prototyping PDMS chips with low surface roughness, sharp edges and locally varying channel heights (United States)

    Gutzweiler, Ludwig; Stumpf, Fabian; Tanguy, Laurent; Roth, Guenter; Koltay, Peter; Zengerle, Roland; Riegger, Lutz


    Microfluidic systems fabricated in polydimethylsiloxane (PDMS) enable a broad variety of applications and are widespread in the field of Lab-on-a-Chip. Here we demonstrate semi-contact-writing, a novel method for fabrication of polymer based molds for casting microfluidic PDMS chips in a highly flexible, time and cost-efficient manner. The method is related to direct-writing of an aqueous polymer solution on a planar glass substrate and substitutes conventional, time- and cost-consuming UV-lithography. This technique facilitates on-demand prototyping in a low-cost manner and is therefore ideally suited for rapid chip layout iterations. No cleanroom facilities and less expertise are required. Fabrication time from scratch to ready-to-use PDMS-chip is less than 5 h. This polymer writing method enables structure widths down to 140 μm and controllable structure heights ranging from 5.5 μm for writing single layers up to 98 μm by stacking. As a unique property, freely selectable height variations across a substrate can be achieved by application of local stacking. Furthermore, the molds exhibit low surface roughness (R a   =  24 nm, R RMS  =  28 nm) and high fidelity edge sharpness. We validated the method by fabrication of molds to cast PDMS chips for droplet based flow-through PCR with single-cell sensitivity.

  16. New Trends in Black American Interracial Marriage: The Social Structural Context. (United States)

    Tucker, M. Belinda; Mitchell-Kernan, Claudia


    Addressed underlying demographic correlates of interracial marriage as distinct among Black women and men. Found that interracially married tended to be younger, more likely to have been married before, and more distant in age from their spouses. Persons born in North and foreign countries were more likely to be married to non-Blacks. (Author/NB)

  17. High Overtone Quasinormal Modes of Analog Black Holes and the Small Scale Structure of the Background Fluid

    CERN Document Server

    Daghigh, Ramin G


    The goal of this paper is to build a foundation for, and explore the possibility of, using high overtone quasinormal modes of analog black holes to probe the small scale (microscopic) structure of a background fluid in which an analog black hole is formed. This may provide a tool to study the small scale structure of some interesting quantum systems such as Bose-Einstein condensates. In order to build this foundation, we first look into the hydrodynamic case where we calculate the high overtone quasinormal mode frequencies of a 3+1 dimensional canonical non-rotating acoustic black hole. The leading order calculations have been done earlier in the literature. Here, we obtain the first order correction. We then analyze the high overtone quasinormal modes of acoustic black holes in a Bose-Einstein condensate using the linearized Gross-Pitaevskii equation. We point out that at the high overtone quasinormal mode limit, the only term that is important in the linearized Gross-Pitaevskii equation is the quantum poten...

  18. Development of a PDMS-grafted alumina membrane and its evaluation as solvent resistant nanofiltration membrane

    NARCIS (Netherlands)

    Pinheiro de Melo, A.F.; Hoogendoorn, D.; Nijmeijer, A.; Winnubst, A.J.A.


    A new solvent resistant nanofiltration (SRNF) membrane is developed by grafting a PDMS polymer into the pores of a 5 nm γ-alumina ceramic membrane. These PDMS-grafted γ-alumina membranes were attained through a two-step synthesis. The linking agent, 3-aminopropyltriethoxysilane (APTES), was first ap

  19. Improved wafer-scale fabrication of aligned pdms-glass microchips with integrated electrodes

    NARCIS (Netherlands)

    Li, J.; Le Gac, S.; Berg, van den A.; Viovy, J.L.; Tabeling, P.; Descroix, S.; Malaquin, L.


    We report an improved fabrication process of PDMS-based hybrid chips at the scale of a whole wafer and including an alignment step. This implies a control of the dimension variations of this elastomer upon temperature changes and the production of a PDMS wafer compatible with the use of standard ali

  20. Preparation and characterization of magnetite–PDMS composites by magnetic induction heating

    Energy Technology Data Exchange (ETDEWEB)

    Darwish, Mohamed S.A., E-mail: [Institute for Nanomaterials, Advanced Technologies and Innovation, Technical University of Liberec, Studentská 2, 461 17 Liberec (Czech Republic); Egyptian Petroleum Research Institute, 1 Ahmed El-Zomor Street, El Zohour Region, Nasr City, Cairo 11727 (Egypt); Stibor, Ivan [Institute for Nanomaterials, Advanced Technologies and Innovation, Technical University of Liberec, Studentská 2, 461 17 Liberec (Czech Republic)


    Magnetic induction heating was used to produce magnetite–Poly (dimethylsiloxane) (PDMS) composites in the presence of the magnetite nanoparticles. Magnetite nanoparticles under an AC magnetic field generate heat, which used to accelerate polymerization and curing of PDMS. Magnetite nanoparticles were prepared using co-precipitation process in the presence of the basic solution. Magnetite nanoparticle was characterized using Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), zeta potential, dynamic light scattering (DLS), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Magnetite–PDMS composite morphology was characterized using scanning electron microscopy, while curing and thermal stability were assessed through infrared spectroscopy and thermogravimetric analysis, respectively. Heating properties and rate of heating of magnetite nanoparticles and magnetite–PDMS composites were studied as a function of time applied and magnetite content (20% and 30%). The improved thermal stability of magnetite–PDMS composite, which produced in a shorter time without using catalyst, compared with the conventional PDMS will offer potential as thermally stable elastomers. - Highlights: • Magnetic induction heating was used to produce magnetite–PDMS composites. • The composites produced in a shorter time without catalyst with improved in the thermal stability. • Magnetite–PDMS composites are promising as thermally stable elastomers.

  1. Elastomeric PDMS Planoconvex Lenses Fabricated by a Confined Sessile Drop Technique. (United States)

    Ekgasit, S; Kaewmanee, N; Jangtawee, P; Thammacharoen, C; Donphoongpri, M


    The ubiquity of high quality smartphones at affordable prices not only accelerated the social penetration in the global population but also promoted nontraditional usage of smartphones as point-of-care medical diagnostic devices, sensors, and portable digital microscopes. This paper reveals a simple, rapid, cost-effective, and template-free technique for mass-scale production of an elastomeric PDMS (ePDMS) planoconvex lens capable of converting a smartphone into a portable digital microscope. By taking advantage of the resistance to spreading of liquid by a sharp edge, highly stable spherical cap of viscous liquid PDMS (lPDMS) on a smooth PMMA circular disk was fabricated. The axisymmetric spreading of lPDMS under the gravitational force and interfacial tension force enable the formation of spherical cap with a certain radius of curvature. A thermal treatment at 80 °C for 30 min cured the spherical cap lPDMS into a bubble-free ePDMS planoconvex lens. Lenses with focal lengths of 55.2-3.4 mm could be reproducibly fabricated by adjusting the volume of dispensed lPDMSs and diameter of PMMA disks. High-resolution panoramic microscope images without a distortion of small cylindrical object could be constructed on-the-fly using the imbedded smartphone app. Applications of the smartphone digital microscope equipped with an ePDMS planoconvex lens for imaging of micro printings, gun shot residues, cylindrical objects, and bullet toolmarks were explored.

  2. Tensile strength of oxygen plasma-created surface layer of PDMS (United States)

    Ohishi, Taiki; Noda, Haruka; Matsui, Tsubasa S.; Jile, Huge; Deguchi, Shinji


    Polydimethylsiloxane (PDMS) is a commonly used silicone elastomer with broad applications. Particularly for bioengineering use, PDMS is treated with oxygen plasma with which its surface is oxidized to allow positive interaction with water and live cells. In exchange for the acquisition of hydrophilicity, the oxidized PDMS becomes mechanically brittle so that resulting formation of cracks affects the system in various ways. However, tensile strength (TS), which is an inherent capacity of a material to withstand tensile loads before breaking and is thus a key parameter limiting the use of the material, remains unclear regarding oxidized PDMS. Here we determine the TS of oxide layers created on the surface of PDMS based on micro-stretch experiments using a custom-made device. We show that the surface layer displays cracks upon tensile loading of small strains of within 10% to have a TS of ~10-100 kPa, which is approximately two orders of magnitude lower than that of unmodified PDMS. We further show that the TS sharply decreases with oxidation duration to become highly brittle, while the thickness of the resulting oxide layer finally reaches a plateau even with prolonged plasma treatment. Consequently, we suggest that gradual surface modification of PDMS takes place only within a finite region even with prolonged plasma treatment, as distinct from previously held assumptions. These quantitative data provide critical design information for the oxide layer of plasma-hydrophilized PDMS.

  3. Motor Skill Performance by Low SES Preschool and Typically Developing Children on the PDMS-2 (United States)

    Liu, Ting; Hoffmann, Chelsea; Hamilton, Michelle


    The purpose of this study was to compare the motor skill performance of preschool children from low socioeconomic (SES) backgrounds to their age matched typically developing peers using the Peabody Developmental Motor Scales-2 (PDMS-2). Sixty-eight children (34 low SES and 34 typically developing; ages 3-5) performed the PDMS-2. Standard scores…

  4. Black titania: effect of hydrogenation on structural and thermal stability of nanotitania (United States)

    Khanam, Rizwin; Taparia, Dolly; Mondal, Biplob; Mohanta, Dambarudhar


    We report on the effect of hydrogenation on sol-gel-derived, anatase-phase TiO2 nanoparticles. The structural analysis of white nanotitania (W-TiO2) and hydrogenated black titania (B-TiO2) has been carried out by X-ray diffraction (XRD) studies, which confirms anatase phase for both the cases, but with weak diffraction signals in the latter system. Upon hydrogenation, nanotitania system is believed to acquire a disordered phase in the form of a thin amorphous layer surrounding the nanoparticles, which can be realized through transmission electron microscopy analyses. As compared to W-TiO2 (~3.15 eV), the optical band gap of B-TiO2 is substantially reduced with respective band gap values of ~1.99 and 1.53 eV for 0.5 and 1 % H2 inclusion cases. Moreover, thermogravimetric analysis reveals high temperature thermal stability of B-TiO2 system, especially in the range of 350-600 °C. Exploiting thermal, optical and electronic properties of hydrogenated nanotitania could find scope in infrared optics, hydrogen storage and suitable photocatalytic applications.

  5. Fabrication and characterization of artificial hair cell sensor based on MWCNT-PDMS composite (United States)

    Kim, Chi Yeon; Lee, Hyun Sup; Cho, Yo Han; Joh, Cheeyoung; Choi, Pyung; Park, Seong Jin


    The aim of this work is to design and fabricate a flow sensor using an artificial hair cell (AHC) inspired by biological hair cells of fish. The sensor consists of a single cilium structure with high aspect ratio and a mechanoreceptor using force sensitive resistor (FSR). The cilium structure is designed for capturing a drag force with direction due to flow field around the sensor and the mechanoreceptor is designed for sensing the drag force with direction from the cilium structure and converting it into an electric signal. The mechanoreceptor has a symmetric four electrodes to sense the drag force and its direction. To fabricate the single cilium structure with high aspect ratio, we have proposed a new design concept using a separated micro mold system (SMS) fabricated by the LIGA process. For a successful replication of the cilium structure, we used the hot embossing process with the help of a double-sided mold system. We used a composite of multiwall carbon nanotube and polydimethylsiloxane (MWCNT-PDMS). The performance of the mechanoreceptors was measured by a computer-controlled nanoindenter. We carried out several experiments with the sensor in the different flow rate and direction using the experimental test apparatus. To calibrate the sensor and calculate the velocity with direction based the signal from the sensor, we analyzed the coupled phenomena between flow field and the cilium structure to calculate the deflection of the cilium structure and the drag force applying to the cilium structure due to the flow field around sensor.

  6. Characterizing the secondary protein structure of black widow dragline silk using solid-state NMR and X-ray diffraction. (United States)

    Jenkins, Janelle E; Sampath, Sujatha; Butler, Emily; Kim, Jihyun; Henning, Robert W; Holland, Gregory P; Yarger, Jeffery L


    This study provides a detailed secondary structural characterization of major ampullate dragline silk from Latrodectus hesperus (black widow) spiders. X-ray diffraction results show that the structure of black widow major ampullate silk fibers is comprised of stacked β-sheet nanocrystallites oriented parallel to the fiber axis and an amorphous region with oriented (anisotropic) and isotropic components. The combination of two-dimensional (2D) (13)C-(13)C through-space and through-bond solid-state NMR experiments provide chemical shifts that are used to determine detailed information about the amino acid motif secondary structure in black widow spider dragline silk. Individual amino acids are incorporated into different repetitive motifs that make up the majority of this protein-based biopolymer. From the solid-state NMR measurements, we assign distinct secondary conformations to each repetitive amino acid motif and, hence, to the amino acids that make up the motifs. Specifically, alanine is incorporated in β-sheet (poly(Alan) and poly(Gly-Ala)), 3(1)-helix (poly(Gly-Gly-Xaa), and α-helix (poly(Gln-Gln-Ala-Tyr)) components. Glycine is determined to be in β-sheet (poly(Gly-Ala)) and 3(1)-helical (poly(Gly-Gly-X(aa))) regions, while serine is present in β-sheet (poly(Gly-Ala-Ser)), 3(1)-helix (poly(Gly-Gly-Ser)), and β-turn (poly(Gly-Pro-Ser)) structures. These various motif-specific secondary structural elements are quantitatively correlated to the primary amino acid sequence of major ampullate spidroin 1 and 2 (MaSp1 and MaSp2) and are shown to form a self-consistent model for black widow dragline silk.

  7. Tree spatial structure, host composition and resource availability influence mirid density or black pod prevalence in cacao agroforests in Cameroon. (United States)

    Gidoin, Cynthia; Babin, Régis; Bagny Beilhe, Leïla; Cilas, Christian; ten Hoopen, Gerben Martijn; Bieng, Marie Ange Ngo


    Combining crop plants with other plant species in agro-ecosystems is one way to enhance ecological pest and disease regulation mechanisms. Resource availability and microclimatic variation mechanisms affect processes related to pest and pathogen life cycles. These mechanisms are supported both by empirical research and by epidemiological models, yet their relative importance in a real complex agro-ecosystem is still not known. Our aim was thus to assess the independent effects and the relative importance of different variables related to resource availability and microclimatic variation that explain pest and disease occurrence at the plot scale in real complex agro-ecosystems. The study was conducted in cacao (Theobroma cacao) agroforests in Cameroon, where cocoa production is mainly impacted by the mirid bug, Sahlbergella singularis, and black pod disease, caused by Phytophthora megakarya. Vegetation composition and spatial structure, resource availability and pest and disease occurrence were characterized in 20 real agroforest plots. Hierarchical partitioning was used to identify the causal variables that explain mirid density and black pod prevalence. The results of this study show that cacao agroforests can be differentiated on the basis of vegetation composition and spatial structure. This original approach revealed that mirid density decreased when a minimum number of randomly distributed forest trees were present compared with the aggregated distribution of forest trees, or when forest tree density was low. Moreover, a decrease in mirid density was also related to decreased availability of sensitive tissue, independently of the effect of forest tree structure. Contrary to expectations, black pod prevalence decreased with increasing cacao tree abundance. By revealing the effects of vegetation composition and spatial structure on mirids and black pod, this study opens new perspectives for the joint agro-ecological management of cacao pests and diseases at the

  8. Impacts of methamidophos, copper, and their combinations on bacterial community structure and function in black soil

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Huiwen; ZHOU; Qixing; ZHANG; Qianru; ZHANG; Chengg


    The potential ecotoxicologial risks of methamidophos, copper, and their combinations on microbial community of black soil ecosystem in the Northeast China were assessed in species richness and structures by using 16S rDNA-PCR-DGGE analysis approach, and functional characteristics at community levels by using BIOLOGGN system analysis method as well as two conventional methods(DHA and SIR). All results of DGGE banding fingerprint patterns(amplified by bacterial specific 16S rDNA V3 high variable region universal primer) indicated that the species richness of bacterial community in tested soil was significantly decreased to different extents by using different concentrations of single methamidophos, copper, especially some of their combinations had worse effects than their corresponding single factors. In addition,the structures of soil bacterial community had been disturbed under all stresses applied in this study because of the enrichment of some species and the disappearance of other species from the bacterial community. The effects of the single factors with lower concentrations on the communiy structure were weaker than those with higher concentrations. Moreover, the bacterial community structures under the combined stresses of methamidophos and copper were significantly different from those of control and their corresponding single factors. The change of DHA and carbon source substrate utilizing fingerprint patterns based on BIOLOGGNsystem were two relatively sensitive directors corresponding to the stress presented in this study. Between methamodophos and copper, there happened the significant joint-toxic actions when they were used in combination on DHA and carbon source substrate utilizing fingerprint patterns of soil bacterial communities. The DHA of soil under the combined stresses was lower than that of the control and that under the single factors, and the BIOLOGGN substrate utilizing patterns of soil treated by combinations were distinctively

  9. Surface tension-induced high aspect-ratio PDMS micropillars with concave and convex lens tips

    KAUST Repository

    Li, Huawei


    This paper reports a novel method for the fabrication of 3-dimensional (3D) Polydimethylsiloxane (PDMS) micropillars with concave and convex lens tips in a one-step molding process, using a CO2 laser-machined Poly(methyl methacrylate) (PMMA) mold with through holes. The PDMS micropillars are 4 mm high and have an aspect ratio of 251. The micropillars are formed by capillary force drawing up PDMS into the through hole mold. The concave and convex lens tips of the PDMS cylindrical micropillars are induced by surface tension and are controllable by changing the surface wetting properties of the through holes in the PMMA mold. This technique eliminates the requirements of expensive and complicated facilities to prepare a 3D mold, and it provides a simple and rapid method to fabricate 3D PDMS micropillars with controllable dimensions and tip shapes. © 2013 IEEE.

  10. Trophic structure of the fouling community in Odessa Bay (Black Sea

    Directory of Open Access Journals (Sweden)

    A. Y. Varigin


    Full Text Available The trophic structure of the coastal fouling community of Odessa Bay (Black Sea, which was composed of 10 species of macrophytes, 57 invertebrate species and 4 species of fish, was determined. The basic trophic relationship between organisms composing the community is shown. A minimization of interspecific trophic competition within the community is noted. The main sources of food material entering the fouling community were determined. We show that a significant proportion of food in the form of detritus, dissolved organic matter and small planktonic organisms enters the community from the water column. Filtration and pumping activity of sestonophage-organisms, particularly mussels, helps to attract food material to the community. Primary producers of the community are macrophytes and microphytes, which develop on account of their photosynthetic activity and ensure the provision of food to herbivores. The trophic group of detritophages consumes different fractions of the detritus which accumulates in the byssus threads of bivalve molluscs. In this context, mussel druses act as sediment traps, collecting detritus. Numerous polyphages, which are essentially omnivores and do not usually lack food material, were noted in the community. A small group of carnivorous invertebrates, whose representatives actively attack small animals, was identified. The abundance of these species in the community was about 1%, and their biomass less than 0.6%. Fish living in macrophyte weeds are the consumers in the community. We determined that the highest relative abundance (over 36% in the fouling community was reached by sestonophages and polyphages. We found that the undisputed leader in the relative biomass (over 97% in the fouling community ofOdessaBaywas the sestonophages (mainly composed of mussels. We determined that the trophic structure index of the community was 0.94, which confirms the significant dominance in biomass of bivalves over other species in

  11. Genetic differentiation and spatial structure of Geosmithia morbida, the causal agent of thousand cankers disease in black walnut (Juglans nigra). (United States)

    Hadziabdic, Denita; Vito, Lisa M; Windham, Mark T; Pscheidt, Jay W; Trigiano, Robert N; Kolarik, Miroslav


    The main objectives of this study were to evaluate genetic composition of Geosmithia morbida populations in the native range of black walnut and provide a better understanding regarding demography of the pathogen. The fungus G. morbida, and the walnut twig beetle, Pityophthorus juglandis, have been associated with a disease complex of black walnut (Juglans nigra) known as thousand cankers disease (TCD). The disease is manifested as branch dieback and canopy loss, eventually resulting in tree death. In 2010, the disease was detected in black walnut in Tennessee, and subsequently in Virginia and Pennsylvania in 2011 and North Carolina in 2012. These were the first incidences of TCD east of Colorado, where the disease has been established for more than a decade on indigenous walnut species. A genetic diversity and population structure study of 62 G. morbida isolates from Tennessee, Pennsylvania, North Carolina and Oregon was completed using 15 polymorphic microsatellite loci. The results revealed high haploid genetic diversity among seven G. morbida populations with evidence of gene flow, and significant differentiation among two identified genetic clusters. There was a significant correlation between geographic and genetic distance. Understanding the genetic composition and demography of G. morbida can provide valuable insight into recognizing factors affecting the persistence and spread of an invasive pathogen, disease progression, and future infestation predictions. Overall, these data support the hypotheses of two separate, highly diverse pathogen introductions into the native range of black walnut.

  12. Membranes ceramic by PDMS/SLC containing groups phosphotungstic acid

    Energy Technology Data Exchange (ETDEWEB)

    Lima, M.O.; Guimaraes, D.H.; Santa Rosa, L.O.; Silva da, L.T.F.; Fiuza, J.R.A.; Boaventura, F.J.S.; Jose, N.M. [Univ. Federal da Bahia, Salvador (Brazil). Dept. of Physical Chemistry


    This study investigated the use of a hybrid material developed for proton exchange membrane fuel cell (PEMFC) applications. The materials were comprised of polydimethylsiloxane reticulated with tetrathylorthosilicate and reinforced with silicon carbide (SiC) and phosphotungstic acid. PDMS and TEOS were reacted in a 70-30 mass proportion. Al203 and PWA were then incorporated in mass proportions of 5, 10, 15, 20, and 25 per cent. The membranes were then analyzed using X-ray diffraction (XRD), thermogravimetric (TG), direct scanning calorimetry (DSC) and Fourier Transform Infrared (FTIR) techniques. The study showed that the addition of SiC and PWA altered both the organization of the material as well as its crystallinity. Load incorporation increased the thermal stability of the material in relation to the pure matrix. The membranes did not exhibit any phase separation. It was concluded that the materials are suitable for PEMFC applications.

  13. Straightforward protein immobilization on Sylgard 184 PDMS microarray surface. (United States)

    Heyries, Kevin A; Marquette, Christophe A; Blum, Loïc J


    In this work, a straightforward technique for protein immobilization on Sylgard 184 is described. The method consists of a direct transfer of dried protein/salt solutions to the PDMS interface during the polymer curing. Such non-conventional treatment of proteins was found to have no major negative consequence on their integrity. The mechanisms of this direct immobilization were investigated using a lysine modified dextran molecule as a model. Clear experimental results suggested that both chemical bounding and molding effect were implicated. As a proof of concept study, three different proteins were immobilized on a single microarray (Arachis hypogaea lectin, rabbit IgG, and human IgG) and used as antigens for capture of chemiluminescent immunoassays. The proteins were shown to be easily recognized by their specific antibodies, giving antibody detection limits in the fmol range.

  14. Enhanced biocompatibility of PDMS (polydimethylsiloxane) polymer films by ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ionescu, M., E-mail: [Australian Nuclear Science and Technology Organization, Sydney (Australia); Winton, B.; Wexler, D. [Faculty of Engineering, University of Wollongong, Wollongong (Australia); Siegele, R.; Deslantes, A.; Stelcer, E.; Atanacio, A.; Cohen, D.D. [Australian Nuclear Science and Technology Organization, Sydney (Australia)


    PDMS films several microns thick deposited on polished Si wafers were irradiated with Mg, Ta, and Fe in the low energy range of 40 keV to 200 keV, and for doses of 10{sup 16}-10{sup 18} ions/cm{sup 2}. After irradiation the films surface is self-organised into 3D coherent and semi-coherent domains. As a consequence of the surface irradiation conditions and the surface boundary conditions, some domains are highly ordered in the form of parallel waves of approximately 1 {mu}m in height, or the result can be semi-ordered regions or disordered regions. In addition, the surface energy of the irradiated polymer is increasing, as reflected in the decrease in its surface hydrophobicity, which is beneficial for cell adhesion. The irradiated samples were tested in vivo, and the results show an increase in viable cell count of up to 650%.

  15. Biocompatible membrane of PDMS for the new chamber prosthesis stapes. (United States)

    Banasik, Katarzyna; Kwacz, Monika


    Stapes protheses are designed for patients with otosclerosis resulting immobilization or significant reduction of the stapes mobility. All currently used prostheses are called - piston prosthesis. However, its use to stimulate the cochlea is still imperfect. New chamber stapes prosthesis allows the perilymph excitation more effective than the piston prothesis. Moreover, the chamber prosthesis eliminates the common causes of piston-stapedotomy failures. The most important element of the new prosthesis is a flexible membrane. The membrane stiffness should be close to the stiffness of normal annular ligament. This work presents the process of selection of the membrane's thickness and its manufacturing technology. Method A 3D model of the chamber stapes prosthesis was build using Autodesk Inventor 2015. The model was imported to Abacus 6.13 computing environment. During numerical simulations, displacements corresponding to applied loads were calculated and the membrane thickness was adjusted so that its stiffness was the same as the ligament stiffness (~ 120 N/m). The compliance ratios calculated from the load-displacement curves for the membrane and the annular ligament were verified using linear regression analysis. After determining the thickness, the manufacturing technology of the membrane was developed. Results The best similarity between the membrane's and annular ligament's stiffness was achieved for PDMS membrane with the 0,15- mm thickness (similarity ratio R2=0,997752). In this work, the technological parameters of spin-coating process for membrane manufacture are also presented. Summary The proper functioning of the chamber stapes prosthesis requires the PDMS membrane with a thickness of 0,15 mm. The 0,15-mm membrane has the tiffness close to the stiffness of the normal annular ligament. Therefore, the chamber stapes prosthesis provides the perilymph stimulation at the level comparable to the healthy ear. New prosthesis is currently under pre

  16. The influence of the PDMS technique in the study of the induced modifications of polymers used in nuclear environment; Apport de la technique PDMS a l`etude des modifications induites dans des polymeres utilises en ambiance nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Nsouli, B. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire


    The PDMS technique (Particle Induced Desorption Mass Spectrometry) combined with a TOF detection (Time of Flight) is the main tool used in this study of polymer degradation in nuclear environment. Ar{sup 3+} ions with a 9 MeV energy have been used to induce the secondary ion emission, and the study was devoted to two stresses typical of this type of environment. The first part of the work concerned with the structural modifications induced by gamma irradiation on ion exchange resin, used for nuclear effluents reprocessing, namely the poly(4-vinylpyridine), or P-4PV. For such a material, the negative fragment emission is particularly sensitive to structural modifications. Difficult physical measurements in such an insoluble and infusible material (IR, UV - Vis, EPR, TGA, dielectric measurements) became consistent after the degradation mechanisms were elucidated. These effects, interpreted in terms of scissions and recombinations, enabled us to explicit different modes of energy deposition, and shed light on some discrepancies between SIMS and PDMS. The second part of the study is devoted to the thermal ageing of an elastomer, used in fabrication of valve gaskets submitted to high temperatures. First of all, we studied the constituents of the polymeric material, i. e. copolymer, homo polymers, and also additives. This last component proved useful to analyze, as a superficial lubricant layer can mask the conformational rearrangements which seem to occur after few hours of thermal treatment (PE blocks are prevailing at the surface). Here too, the PDMS information is important to account for static SIMS and ESCA results, as its probed layer thickness lies in-between. (author) 187 refs.

  17. Optimal use of resources structures home ranges and spatial distribution of black bears (United States)

    Mitchell, M.S.; Powell, R.A.


    Research has shown that territories of animals are economical. Home ranges should be similarly efficient with respect to spatially distributed resources and this should structure their distribution on a landscape, although neither has been demonstrated empirically. To test these hypotheses, we used home range models that optimize resource use according to resource-maximizing and area-minimizing strategies to evaluate the home ranges of female black bears, Ursus americanus, living in the southern Appalachian Mountains. We tested general predictions of our models using 104 home ranges of adult female bears studied in the Pisgah Bear Sanctuary, North Carolina, U.S.A., from 1981 to 2001. We also used our models to estimate home ranges for each real home range under a variety of strategies and constraints and compared similarity of simulated to real home ranges. We found that home ranges of female bears were efficient with respect to the spatial distribution of resources and were best explained by an area-minimizing strategy with moderate resource thresholds and low levels of resource depression. Although resource depression probably influenced the spatial distribution of home ranges on the landscape, levels of resource depression were too low to quantify accurately. Home ranges of lactating females had higher resource thresholds and were more susceptible to resource depression than those of breeding females. We conclude that home ranges of animals, like territories, are economical with respect to resources, and that resource depression may be the mechanism behind ideal free or ideal preemptive distributions on complex, heterogeneous landscapes. ?? 2007 The Association for the Study of Animal Behaviour.

  18. Results of many-year subsatellite measurements of current fine structure in northeastern Black Sea (United States)

    Lavrova, Olga; Krayushkin, Evgeny; Kalashnikova, Nina

    Results of subsatellite measurements of coastal currents in the shelf zone of northeastern Black Sea are presented. The measurements have been performed every year since 2006 in June and September-October months near the Gelendzhik Bay. The main instruments used are Acoustic Doppler Current Profilers (ADCP) and CTD probes. Ground and ship measurements were conducted simultaneously with satellite imaging in microwave (ASAR Envisat, ERS-2, RADARSAT-2, TerraSAR-X), visible and infrared (OLI Landsat-8, ETM+ Landsat-7, TM Landsat-5, MODIS Terra/Aqua, AVHRR NOAA) ranges. The investigations performed revealed spatial, depth and temporal variability of current direction and velocity in the shelf zone. Multiple instances of counter-currents opposing to the Ring Current were registered. In our view, they are associated with a passage of small-scale anticyclonic eddies across the region of interest. The 3D structure of the eddies in the upper quasi-uniform layer was analyzed based on ADCP data. The use of high resolution (3 m) SAR data in combination with ADCP measurements at the resolution of 0.5 m allowed us to detect a number of internal wave trains. Form ADCP and thermistors records, their amplitudes were estimated to reach 5-8 m. Joint analysis of satellite SAR and subsatellite data gave an assessment of their typical wavelength at 90-100 m. Generation mechanisms of these internal waves are suggested. Another phenomenon of interest observed in the region of the measurements is surface manifestations of ring waves near localized natural and anthropogenic generation sources. Such ring waves are most frequently found in the anchor area for ships, whose oscillations can be the source of their generation. The work was in part supported by the Russian Foundation for Basic Research (projects #14-05-00520-а, and 13-07-12017-ofi_m). SAR data from RADARSAT-2 and TerraSAR-X were obtained under SOAR RADARSAT-2/TerraSAR-X Project #5074.

  19. Characterizing the Deformation of the Polydimethylsiloxane (PDMS Membrane for Microfluidic System through Image Processing

    Directory of Open Access Journals (Sweden)

    Xiang Qian


    Full Text Available Polydimethylsiloxane (PDMS membranes have been widely used in the microfluidic community to achieve various functions such as control, sensing, filter, etc. In this paper, an experimental process was proposed to directly characterize the deformation of the on-chip PDMS membrane at large deformation based on the image processing method. High precision pressures were applied on the surface of the PDMS membrane with fixed edges and a series deformation of the PDMS membrane were captured by the imaging system. The Chan and Vese (CV level set method was applied to segment the images of the deformed membrane. The volumes wrapped by the deformed membranes were obtained, and pressure-volumes relationships of the PDMS membranes with different geometry parameters were also calculated. Then the membrane capacitance can be derived by differentiating the curve of pressure-volumes. In addition, the theoretical estimation of the capacitance of the PDMS membrane at large deformation was also obtained through finite element simulation (FEM, which was in good agreement with the experimental results. These results are expected to be significant for designing and on-chip measuring of such PDMS membrane based microfluidic components in our future work.

  20. The Fabrication and Application of a PDMS Micro Through-Holes Mask in Electrochemical Micromanufacturing

    Directory of Open Access Journals (Sweden)

    Xiaolei Chen


    Full Text Available The electrochemical micromanufacturing process, as a key micromanufacturing technology, plays an important role in diverse industries. In this paper, polydimethylsiloxane (PDMS is employed as a mask in the electrochemical micromanufacture of microstructures because of its chemical resistance, low cost, flexibility, and high molding capability. A new method for fabricating a PDMS micro through-holes mask is proposed. In this method, a thin resist film is employed to enhance the adhesion between the substrate and the SU-8 pillar array which is used as a mold. A vacuum-aided process is used to inject the PDMS gel into the SU-8 mold and the PDMS micro through-holes mask can be peeled off from the SU-8 mold when the gel is cured. Experiments were conducted to verify the feasibility of the proposed approach and PDMS microholes of various shapes were obtained. The PDMS mask can then be successfully applied in the electrochemical micromanufacturing process to generate microstructures and microdimple and embossment arrays have been successfully demonstrated. Furthermore, the PDMS mask can be reused, as it is not damaged during the manufacturing process.

  1. Vacuum-driven power-free microfluidics utilizing the gas solubility or permeability of polydimethylsiloxane (PDMS). (United States)

    Xu, Linfeng; Lee, Hun; Jetta, Deekshitha; Oh, Kwang W


    Suitable pumping methods for flow control remain a major technical hurdle in the path of biomedical microfluidic systems for point-of-care (POC) diagnostics. A vacuum-driven power-free micropumping method provides a promising solution to such a challenge. In this review, we focus on vacuum-driven power-free microfluidics based on the gas solubility or permeability of polydimethylsiloxane (PDMS); degassed PDMS can restore air inside itself due to its high gas solubility or gas permeable nature. PDMS allows the transfer of air into a vacuum through it due to its high gas permeability. Therefore, it is possible to store or transfer air into or through the gas soluble or permeable PDMS in order to withdraw liquids into the embedded dead-end microfluidic channels. This article provides a comprehensive look at the physics of the gas solubility and permeability of PDMS, a systematic review of different types of vacuum-driven power-free microfluidics, and guidelines for designing solubility-based or permeability-based PDMS devices, alongside existing applications. Advanced topics and the outlook in using micropumping that utilizes the gas solubility or permeability of PDMS will be also discussed. We strongly recommend that microfluidics and lab-on-chip (LOC) communities harness vacuum energy to develop smart vacuum-driven microfluidic systems.

  2. Enhancement of output performance through post-poling technique on BaTiO3/PDMS-based triboelectric nanogenerator (United States)

    Ali, Danish; Yu, Bin; Duan, Xiaochao; Yu, Hao; Zhu, Meifang


    In the modern era, the invention of new energy sources is important in order to make advances possible in electronic media. A triboelectric nanogenerator (TENG) is considered to be strong design that converts mechanical power into electrical power, using organic (polymer) or inorganic (lead, ceramic etc) materials to initiate the triboelectrification process, followed by charge separation. In this study, a lead-free BaTiO3/PDMS-Al-based TENG was fabricated by mixing tetragonal ferroelectric BaTiO3 nanocrystals in a PDMS matrix to make a composite for a working electrode film. It is worth noting that a new post- poling process has been introduced to align the dipole structures in the BaTiO3 nanocrystals, and to attain a high electron density on the surface of the working electrode film. The output was recorded up to 375 V and 6 μA of close circuit voltage and short circuit current, respectively, at a current density of 0.3 μA cm-2 and an effective power equal to 2.25 mW at a load resistance of 100 MΩ, and is four times higher than a PDMS-Al-based TENG. This study also reveals the hidden locks that will enable other inorganic materials with a dipole structure to enhance their output using the post-poling technique. The TENG has a vast field of applications due to its stability, the flexibility of its thin films and its biocompatibility. It is also an aid for exploring new TENG devices with enhanced output performance.

  3. Phase structure of the Born-Infeld-anti-de Sitter black holes probed by non-local observables

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Xiao-Xiong [Chongqing Jiaotong University, School of Material Science and Engineering, Chongqing (China); Chinese Academy of Sciences, Institute of Theoretical Physics, Beijing (China); Liu, Xian-Ming [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, MA (United States); Hubei University for Nationalities, Center for Theoretical Physics, School of Sciences, Enshi, Hubei (China); Li, Li-Fang [Chinese Academy of Sciences, State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Beijing (China)


    With the non-local observables such as two point correlation function and holographic entanglement entropy, we probe the phase structure of the Born-Infeld-anti-de Sitter black holes. For the case bQ > 0.5, where b is the Born-Infeld parameter and Q is the charge of the black hole, the phase structure is found to be similar to that of the Van der Waals phase transition, namely the black hole undergoes a first order phase transition and a second order phase transition before it reaches a stable phase. While for the case bQ < 0.5, a new phase branch emerges besides the Van der Waals phase transition. For the first order phase transition, the equal area law is checked, and for the second order phase transition, the critical exponent of the heat capacity is obtained. All these results are found to be the same as that observed in the entropy-temperature plane. (orig.)

  4. Probing the Magnetic Field Structure in {Sgr}\\,{\\rm{A}}* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations (United States)

    Gold, Roman; McKinney, Jonathan C.; Johnson, Michael D.; Doeleman, Sheperd S.


    Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical simulations to model thermal synchrotron emission from the Galactic Center source Sagittarius A* (Sgr A*). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability as well as models with large-scale ordered fields in magnetically arrested disks. We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford–Znajek-driven funnel jet. Our comparisons between the simulations and observations favor models with ordered magnetic fields near the black hole event horizon in Sgr A*, though both disk- and jet-dominated emission can satisfactorily explain most of the current EHT data. We also discuss how the black hole shadow can be filled-in by jet emission or mimicked by the absence of funnel jet emission. We show that stronger model constraints should be possible with upcoming circular polarization and higher frequency (349 GHz) measurements.

  5. Effects of warming on the structure and function of a boreal black spruce forest

    Energy Technology Data Exchange (ETDEWEB)

    Stith T.Gower


    A strong argument can be made that there is a greater need to study the effect of warming on boreal forests more than on any other terrestrial biome. Boreal forests, the second largest forest biome, are predicted to experience the greatest warming of any forest biome in the world, but a process-based understanding of how warming will affect the structure and function of this economically and ecologically important forest biome is lacking. The effects of warming on species composition, canopy structure and biogeochemical cycles are likely to be complex; elucidating the underlying mechanisms will require long-term whole-ecosystem manipulation to capture all the complex feedbacks (Shaver et al. 2000, Rustad et al. 2001, Stromgren 2001). The DOE Program for Ecosystem Research funded a three year project (2002-2005) to use replicated heated chambers on soil warming plots in northern Manitoba to examine the direct effects of whole-ecosystem warming. We are nearing completion of our first growing season of measurements (fall 2004). In spite of the unforeseen difficulty of installing the heating cable, our heating and irrigation systems worked extremely well, maintaining environmental conditions within 5-10% of the specified design 99% of the time. Preliminary data from these systems, all designed and built by our laboratory at the University of Wisconsin, support our overall hypothesis that warming will increase the carbon sink strength of upland boreal black spruce forests. I request an additional three years of funding to continue addressing the original objectives: (1) Examine the effect of warming on phenology of overstory, understory and bryophyte strata. Sap flux systems and dendrometer bands, monitored by data loggers, will be used to quantify changes in phenology and water use. (2) Quantify the effects of warming on nitrogen and water use by overstory, understory and bryophytes. (3) Compare effects of warming on autotrophic respiration and above- and belowground

  6. Variation in diffusion of gases through PDMS due to plasma surface treatment and storage conditions. (United States)

    Markov, Dmitry A; Lillie, Elizabeth M; Garbett, Shawn P; McCawley, Lisa J


    Polydimethylsiloxane (PDMS) is a commonly used polymer in the fabrication of microfluidic devices due to such features as transparency, gas permeability, and ease of patterning with soft lithography. The surface characteristics of PDMS can also be easily changed with oxygen or low pressure air plasma converting it from a hydrophobic to a hydrophilic state. As part of such a transformation, surface methyl groups are removed and replaced with hydroxyl groups making the exposed surface to resemble silica, a gas impermeable substance. We have utilized Platinum(II)-tetrakis(pentaflourophenyl)porphyrin immobilized within a thin (~1.5 um thick) polystyrene matrix as an oxygen sensor, Stern-Volmer relationship, and Fick's Law of simple diffusion to measure the effects of PDMS composition, treatment, and storage on oxygen diffusion through PDMS. Results indicate that freshly oxidized PDMS showed a significantly smaller diffusion coefficient, indicating that the SiO2 layer formed on the PDMS surface created an impeding barrier. This barrier disappeared after a 3-day storage in air, but remained significant for up to 3 weeks if PDMS was maintained in contact with water. Additionally, higher density PDMS formulation (5:1 ratio) showed similar diffusion characteristics as normal (10:1 ratio) formulation, but showed 60 % smaller diffusion coefficient after plasma treatment that never recovered to pre-treatment levels even after a 3-week storage in air. Understanding how plasma surface treatments contribute to oxygen diffusion will be useful in exploiting the gas permeability of PDMS to establish defined normoxic and hypoxic oxygen conditions within microfluidic bioreactor systems.

  7. Effect of mold treatment by solvent on PDMS molding into nanoholes (United States)

    Con, Celal; Cui, Bo


    Polydimethylsiloxane (PDMS) is the most popular and versatile material for soft lithography due to its flexibility and easy fabrication by molding process. However, for nanoscale patterns, it is challenging to fill uncured PDMS into the holes or trenches on the master mold that is coated with a silane anti-adhesion layer needed for clean demolding. PDMS filling was previously found to be facilitated by diluting it with toluene or hexane, which was attributed to the great reduction of viscosity for diluted PDMS. Here, we suggest that the reason behind the improved filling for diluted PDMS is that the diluent solvent increases in situ the surface energy of the silane-treated mold and thus the wetting of PDMS to the mold surface. We treated the master mold surface (that was already coated with a silane anti-adhesion monolayer) with toluene or hexane, and found that the filling by undiluted PMDS into the nanoscale holes on the master mold was improved despite the high viscosity of the undiluted PDMS. A simple estimation based on capillary filing into a channel also gives a filling time on the millisecond scale, which implies that the viscosity of PMDS should not be the limiting factor. We achieved a hole filling down to sub-200-nm diameter that is smaller than those of the previous studies using regular Sylgard PDMS (not hard PDMS, Dow Corning Corporation, Midland, MI, USA). However, we are not able to explain using a simple argument based on wetting property why smaller, e.g., sub-100-nm holes, cannot be filled, for which we suggested a few possible factors for its explanation.

  8. Black holes

    CERN Document Server

    Chrúsciel, P T


    This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usual one for gravity, and leads to the one associated with the Unruh metric in the case of Euler equations. We review the global conditions which have been used in the Scri-based definition of a black hole and point out the deficiencies of the Scri approach. Various results on the structure of horizons and apparent horizons are presented, and a new proof of semi-convexity of horizons based on a variational principle is given. Recent results on the classification of stationary singularity-free vacuum solutions are reviewed. ...

  9. Line Shapes Emitted from Spiral Structures around Symmetric Orbits of Supermassive Binary Black Holes

    CERN Document Server

    Smailagić, Marijana


    Variability of active galactic nuclei is not well understood. One possible explanation is existence of supermassive binary black holes (SMBBH) in their centres. It is expected that major mergers are common in the Universe. It is expected that each supermassive black hole of every galaxy eventually finish as a SMBBH system in the core of newly formed galaxy. Here we model the emission line profiles of active galactic nuclei (AGN) assuming that the flux and emission line shapes variation are induced by supermassive binary black hole systems (SMBBH). We assume that accreting gas inside of circumbinary (CB) disk is photo ionized by mini accretion disk emission around each SMBBH. We calculate variations of emission line flux, shifts and shapes for different parameters of SMBBH orbits. We consider cases with different masses and inclinations for circular orbits and measure the effect to the shape of emission line profiles and flux variability.

  10. Prediction of Partition Coefficients of Organic Compounds for SPME/PDMS

    Directory of Open Access Journals (Sweden)

    Liao Hsuan-Yu


    Full Text Available The partition coefficients of 51 organic compounds between SPME/PDMS and gas were compiled from the literature sources in this study. The effect of physicochemical properties and descriptors on the partitioning process of partition coefficients was explicated by the correlation analysis. The PDMS-gas partition coefficients were well correlated to the molecular weight of organic compounds (r = 0.832, p < 0.05. An empirical model, consisting of the molecular weight and the polarizability, was developed to appropriately predict the partition coefficients of organic compounds. The empirical model for estimating the PDMS-gas partition coefficient will contribute to the practical applications of the SPME technique.

  11. Polydimethylsiloxane (PDMS Coating onto Magnetic Nanoparticles Induced by Attractive Electrostatic Interaction

    Directory of Open Access Journals (Sweden)

    Carina Sötebier


    Full Text Available In this article, we present an efficient synthesis pathway of polydimethylsiloxane (PDMS coated magnetic nanoparticles from hydrophilic polyacrylate coated ferrofluids (NPPAA. A block copolymer based on polydimethylsiloxane is selected for its propensity to interact with the carboxylate functions on the NPPAA. The interaction is due to negative charges on NPPAA and positive ones on the amphiphilic copolymer. The synthesis is achieved by interfacial interaction, simplifying the purification of the PDMS-coated nanoparticles (NPPDMS from subproducts such as ions and water. NPPDMS are well dispersed in hydrophobic solvents (toluene, diethyl ether and can then be embedded into a curable PDMS polymer.

  12. Quantitative Analysis of Major Factors Affecting Black Carbon Transport and Concentrations in the Unique Atmospheric Structures of Urban Environment (United States)

    Liang, Marissa Shuang

    Black carbon (BC) from vehicular emission in transportation is a principal component of particulate matters ≤ 2.5 mum (PM2.5). PM2.5 and other diesel emission pollutants (e.g., NOx) are regulated by the Clean Air Act (CAA) according to the National Ambient Air Quality standards (NAAQS). This doctoral dissertation details a study on transport behaviors of black carbon and PM2.5 from transportation routes, their relations with the atmospheric structure of an urban formation, and their relations with the use of biodiesel fuels. The results have implications to near-road risk assessment and to the development of sustainable transportation solutions in urban centers. The first part of study quantified near-roadside black carbon transport as a function of particulate matter (PM) size and composition, as well as microclimatic variables (temperature and wind fields) at the interstate highway I-75 in northern Cincinnati, Ohio. Among variables examined, wind speed and direction significantly affect the roadside transport of black carbon and hence its effective emission factor. Observed non-Gaussian dispersion occurred during low wind and for wind directions at acute angles or upwind to the receptors, mostly occurring in the morning hours. Meandering of air pollutant mass under thermal inversion is likely the driving force. In contrary, Gaussian distribution predominated in daytime of strong downwinds. The roles of urban atmospheric structure, wind fields, and the urban heat island (UHI) effects were further examined on pollutant dispersion and transport. Spatiotemporal variations of traffic flow, atmospheric structure, ambient temperature and PM2.5 concentration data from 14 EPA-certified NAAQS monitoring stations, were analyzed in relation to land-use in the Cincinnati metropolitan area. The results show a decade-long UHI effects with higher interior temperature than that in exurban, and a prominent nocturnal thermal inversion frequent in urban boundary layer. The

  13. Fabrication of broadband antireflective black metal surfaces with ultra-light-trapping structures by picosecond laser texturing and chemical fluorination (United States)

    Zheng, Buxiang; Wang, Wenjun; Jiang, Gedong; Mei, Xuesong


    A hybrid method consisting of ultrafast laser-assisted texturing and chemical fluorination treatment was applied for efficiently enhancing the surface broadband antireflection to fabricate black titanium alloy surface with ultra-light-trapping micro-nanostructure. Based on the theoretical analysis of surface antireflective principle of micro-nanostructures and fluoride film, the ultra-light-trapping micro-nanostructures have been processed using a picosecond pulsed ultrafast laser on titanium alloy surfaces. Then fluorination treatment has been performed by using fluoroalkyl silane solution. According to X-ray diffraction phase analysis of the surface compositions and measurement of the surface reflectance using spectrophotometer, the broadband antireflective properties of titanium alloy surface with micro-nano structural characteristics were investigated before and after fluorination treatment. The results show that the surface morphology of micro-nanostructures processed by picosecond laser has significant effects on the antireflection of light waves to reduce the surface reflectance, which can be further reduced using chemical fluorination treatment. The high antireflection of over 98 % in a broad spectral range from ultraviolet to infrared on the surface of metal material has been achieved for the surface structures, and the broadband antireflective black metal surfaces with an extremely low reflectance of ultra-light-trapping structures have been obtained in the wavelength range from ultraviolet-visible to near-infrared, middle-wave infrared. The average reflectance of microgroove groups structured surface reaches as low as 2.43 % over a broad wavelength range from 200 to 2600 nm. It indicates that the hybrid method comprising of picosecond laser texturing and chemical fluorination can effectively induce the broadband antireflective black metal surface. This method has a potential application for fabricating antireflective surface used to improve the

  14. Substantial molecular variation and low genetic structure in Kenya’s black rhinoceros: implications for conservation

    NARCIS (Netherlands)

    Muya, S.M.; Bruford, M.W.; Muigai, A.W.T.; Osiemo, Z.B.; Mwachiro, E.; Ouma, B.O.; Goossens, B.


    Kenya’s black rhinoceros population declined by more than 98% from 20,000 individuals in the 1970s to around 400 individuals in 1990 due to the effects of poaching, at which time the surviving individuals were isolated in a series of demographically inviable subpopulations. An initial management exe

  15. Study on internal structure of Maxwell-Gauss-Bonnet black hole

    Energy Technology Data Exchange (ETDEWEB)

    Rannu, K A; Alexeyev, S O [Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetsy Prospect, 13, Moscow 119991 (Russian Federation); Barrau, A, E-mail: rannu@xray.sai.msu.r [Laboratoire de Physique Subatomique et de Cosmologie, UJF-INPG-CNRS, 53, avenue des Martyrs, 38026 Grenoble cedex (France)


    The influence of the Maxwell field on a static, asymptotically flat and spherically-symmetric Gauss-Bonnet black hole is considered. Numerical computations suggest that if the charge increases beyond a critical value, the inner determinant singularity is replaced by an inner singular horizon.

  16. Event Horizon Telescope Observations as Probes for Quantum Structure of Astrophysical Black Holes

    CERN Document Server

    Giddings, Steven B


    The need for a consistent quantum evolution for black holes has led to proposals that their semiclassical description is modified not just near the singularity, but at horizon or larger scales. If such modifications extend beyond the horizon, they influence regions accessible to distant observeration. Natural candidates for these modifications behave like metric fluctuations, with characteristic length and time scales set by the horizon radius. We investigate the possibility of using the Event Horizon Telescope to observe these effects, if they have a strength sufficient to make quantum evolution consistent with unitarity. We find that such quantum fluctuations can introduce a strong time dependence for the shape and size of the shadow that a black hole casts on its surrounding emission. For the black hole in the center of the Milky Way, detecting the rapid time variability of its shadow will require non-imaging timing techniques. However, for the much larger black hole in the center of the M87 galaxy, a vari...

  17. Black Female Adolescents' Career Aspirations and Expectations: Rising to the Challenge of the American Occupational Structure. (United States)

    Brown, Sherlon P.

    Career and life planning, while a complex task for people of all races and ages, is often compounded for black adolescent females. Social and economic traditions such as racism, poverty, and oppression have often retarded their employment perceptions, aspirations, expectations, and realities. This article explores the relationship between black…

  18. Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy for mapping nano-scale distribution of organic carbon forms in soil: Application to black carbon particles (United States)

    Lehmann, Johannes; Liang, Biqing; Solomon, Dawit; Lerotic, Mirna; LuizãO, Flavio; Kinyangi, James; SchäFer, Thorsten; Wirick, Sue; Jacobsen, Chris


    Small-scale heterogeneity of organic carbon (C) forms in soils is poorly quantified since appropriate analytical techniques were not available up to now. Specifically, tools for the identification of functional groups on the surface of micrometer-sized black C particles were not available up to now. Scanning Transmission X-ray Microscopy (STXM) using synchrotron radiation was used in conjunction with Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy to investigate nano-scale distribution (50-nm resolution) of C forms in black C particles and compared to synchrotron-based FTIR spectroscopy. A new embedding technique was developed that did not build on a C-based embedding medium and did not pose the risk of heat damage to the sample. Elemental sulfur (S) was melted to 220°C until it polymerized and quenched with liquid N2 to obtain a very viscous plastic S in which the black C could be embedded until it hardened to a noncrystalline state and was ultrasectioned. Principal component and cluster analysis followed by singular value decomposition was able to resolve distinct areas in a black carbon particle. The core of the studied biomass-derived black C particles was highly aromatic even after thousands of years of exposure in soil and resembled the spectral characteristics of fresh charcoal. Surrounding this core and on the surface of the black C particle, however, much larger proportions of carboxylic and phenolic C forms were identified that were spatially and structurally distinct from the core of the particle. Cluster analysis provided evidence for both oxidation of the black C particle itself as well as adsorption of non-black C. NEXAFS spectroscopy has great potential to allow new insight into black C properties with important implications for biogeochemical cycles such as mineralization of black C in soils and sediments, and adsorption of C, nutrients, and pollutants as well as transport in the geosphere, hydrosphere, and atmosphere.

  19. Structural Transition in the NGC 6251 Jet: an Interplay with the Supermassive Black Hole and Its Host Galaxy (United States)

    Tseng, Chih-Yin; Asada, Keiichi; Nakamura, Masanori; Pu, Hung-Yi; Algaba, Juan-Carlos; Lo, Wen-Ping


    The structure of the NGC 6251 jet on the milliarcsecond scale is investigated using images taken with the European VLBI Network and the Very Long Baseline Array. We detect a structural transition of the jet from a parabolic to a conical shape at a distance of (1-2) × 105 times the Schwarzschild radius from the central engine, which is close to the sphere of gravitational influence of the supermassive black hole (SMBH). We also examine the jet pressure profiles with the synchrotron minimum energy assumption to discuss the physical origin of the structural transition. The NGC 6251 jet, together with the M87 jet, suggests a fundamental process of structural transition in the jets of active galactic nuclei (AGNs). Collimated AGN jets are characterized by their external galactic medium, showing that AGN jets interplay with the SMBH and its host galaxy.

  20. Structural Transition in the NGC 6251 Jet: An Interplay with the Supermassive Black Hole and Its Host Galaxy

    CERN Document Server

    Tseng, Chih-Yin; Nakamura, Masanori; Pu, Hung-Yi; Algaba, Juan-Carlos; Lo, Wen-Ping


    The structure of the NGC 6251 jet at the milliarcsecond scale is investigated using the images taken with the European VLBI Network and the Very Long Baseline Array. We detect a structural transition of the jet from a parabolic to a conical shape at a distance of (1-2) x 10^5 times the Schwarzschild radius from the central engine, which is close to the sphere of gravitational influence (SGI) of the supermassive black hole (SMBH). We also examine the jet pressure profiles with the synchrotron minimum energy assumption to discuss the physical origin of the structural transition. The NGC 6251 jet, together with the M 87 jet, suggests a fundamental process of the structural transition in active galactic nuclei (AGN) jets. The collimated AGN jets are characterized by their external galactic medium, showing that AGN jets interplay with the SMBH and its host galaxy.

  1. Microanatomy of Passerine hard-cornified tissues: beak and claw structure of the Black-capped Chickadee (Poecile atricapillus) (United States)

    Van Hemert, Caroline R.; Handel, Colleen M.; Blake, J.; Swor, Rhonda; O'Hara, Todd M.


    The microanatomy of healthy beaks and claws in passerine birds has not been well described in the literature, despite the importance of these structures in avian life. Histological processing of hard-cornified tissues is notoriously challenging and only a few reports on effective techniques have been published. An emerging epizootic of beak deformities among wild birds in Alaska and the Pacific Northwest region of North America recently highlighted the need for additional baseline information about avian hard-cornified structures. In this study, we examine the beak and claw of the Black-capped Chickadee (Poecile atricapillus), a common North American passerine that is affected by what has been described as “avian keratin disorder.” We use light and scanning electron microscopy and high-magnification radiography to document the healthy microanatomy of these tissues and identify features of functional importance. We also describe detailed methods for histological processing of avian hard-cornified structures and discuss the utility of special stains. Results from this study will assist in future research on the functional anatomy and pathology of hard-cornified structures and will provide a necessary reference for ongoing investigations of avian keratin disorder in Black-capped Chickadees and other wild passerine species.

  2. Landscape structure and plague occurrence in black-tailed prairie dogs on grasslands of the western USA (United States)

    Collinge, S.K.; Johnson, W.C.; Ray, C.; Matchett, R.; Grensten, J.; Cully, J.F.; Gage, K.L.; Kosoy, M.Y.; Loye, J.E.; Martin, A.P.


    Landscape structure influences the abundance and distribution of many species, including pathogens that cause infectious diseases. Black-tailed prairie dogs in the western USA have declined precipitously over the past 100 years, most recently due to grassland conversion and their susceptibility to sylvatic plague. We assembled and analyzed two long-term data sets on plague occurrence in black-tailed prairie dogs to explore the hypotheses that plague occurrence is associated with colony characteristics and landscape context. Our two study areas (Boulder County, Colorado, and Phillips County, Montana) differed markedly in degree of urbanization and other landscape characteristics. In both study areas, we found associations between plague occurrence and landscape and colony characteristics such as the amount of roads, streams and lakes surrounding a prairie dog colony, the area covered by the colony and its neighbors, and the distance to the nearest plague-positive colony. Logistic regression models were similar between the two study areas, with the best models predicting positive effects of proximity to plague-positive colonies and negative effects of road, stream and lake cover on plague occurrence. Taken together, these results suggest that roads, streams and lakes may serve as barriers to plague in black-tailed prairie dog colonies by affecting movement of or habitat quality for plague hosts or for fleas that serve as vectors for the pathogen. The similarity in plague correlates between urban and rural study areas suggests that the correlates of plague are not altered by uniquely urban stressors. ?? Springer 2005.

  3. Enhancing relative permittivity by incorporating PDMS-PEG multiblock copolymers in binary polymer blends

    DEFF Research Database (Denmark)

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

    Polydimethylsiloxane (PDMS) elastomers are well-known to be soft and highly stretchable, yet they never achieve maximum elongation when utilised as dielectric elastomers, simply because their dielectric permittivity remains rather low. Conversely, polyethyleneglycols (PEG) are not stretchable...

  4. Physico-chemical properties of PDMS surfaces suitable as substrates for cell cultures (United States)

    Raczkowska, Joanna; Prauzner-Bechcicki, Szymon; Lukes, Jaroslav; Sepitka, Josef; Bernasik, Andrzej; Awsiuk, Kamil; Paluszkiewicz, Czesława; Pabijan, Joanna; Lekka, Małgorzata; Budkowski, Andrzej


    Elastic properties of the substrate have profound effect on adhesion and proliferation of cells. Here, we introduce a method to produce polydimethylsiloxane (PDMS) substrates with stiffness tuned monotonically from 1.67 to 0.24 MPa, by the time of UV irradiation adjusted up to 5 h. The Young's modulus (determined by using nanoindenter) scales linearly with stiffness calculated using AFM-based force spectroscopy data. Such a relation enables the determination of the Young modulus from AFM force - distance curves also when the Herz model is not applicable. Our findings demonstrate that surface properties of PDMS substrates are not affected by the applied methodology of tuning substrate elasticity. Finally, the colorimetric proliferation assay (MTT) carried out for non-malignant (HCV29) and cancerous (T24) bladder cancer cells depicted a significant contribution of PDMS substrate elasticity to the behavior of cells. The softer PDMS substrate demonstrated excellent cytocompatibility whereas the stiff one is more cell-repellent.

  5. Fabrication of silver nanorods embedded in PDMS film and its application for strain sensing (United States)

    Goel, Pratibha; Singh, J. P.


    Highly reflective and surface conductive strain gauges have been prepared by embedding the silver nanorods (AgNRs) into polydimethylsiloxane (PDMS). Thermal curing of PDMS on AgNRs grown Si wafer leads to a flexible, reflective and conductive silver surface. The reflectance of the as prepared films were observed to be 60% with a low value of sheet resistance. The reflectance of the film was able to be tuned from 60% to 15% in the visible region. The fabrication of a parallel plate capacitor strain sensor from AgNRs embedded PDMS, and tuning of the capacitance with respect to the applied strain, leads to a gauge factor of ~1. These mechanically tunable AgNRs/PDMS films demonstrate potential application as a strain sensor.

  6. Green silicone elastomer obtained from a counterintuitively stable mixture of glycerol and PDMS

    DEFF Research Database (Denmark)

    Mazurek, P.; Hvilsted, S.; Skov, A. L.


    for obtaining elastomeric composites with uniformly distributed glycerol droplets. Various compositions, containing from 0 to 140 parts of glycerol per 100 parts of PDMS by weight, were prepared and investigated in terms of ATR-FTIR, broadband dielectric spectroscopy, mechanical properties as well as optical......A green and cheap silicone-based elastomer has been developed. Through the simple mixing-in of biodiesel-originating glycerol into commercially available polydimethylsiloxane (PDMS) pre-polymer, a glycerol-in-PDMS emulsion was produced. This counterintuitively stable mixture became a basis...... 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...

  7. Fabrication of the PDMS-Glass Microfluidic Chip with Integrated Electrodes%集成电极的PDMS-玻璃微流控芯片的制备

    Institute of Scientific and Technical Information of China (English)

    伍择希; 张卫平; 陈俊杰; 李金凤; 陈文元; 吴校生; 崔峰; 刘武; 姜川


    微流控芯片在分析化学和生物检测方面有着广阔的应用前景.对集成电极的PDMS -玻璃微流控芯片的制备工艺进行了研究与分析.最终使用SU -8快速制备阳模,使用PDMS转移图形得到具有微流控通道的PDMS盖片;在玻璃基板上加工Pt电极,除了需要外露的部分电极外,其他部分以薄层PDMS保护,得到电极基板;将PDMS盖片与电极基板半固化键合制得同时具有加热和温度传导电极以及CE高压电极的PDMS -玻璃芯片.ANSYS模拟分析证明加热芯片热惯性小,加热时温度分布效果好.%In the field of the analytical chemistry and biological detection, the microfluidic chip has a broad application prospect. The fabrication process of the PDMS-glass microfluidic chip with integrated electrodes was researched and analyzed. The male mould was made by SU - 8, and the PDMS cover plate with microfluidic channels was obtained by the PDMS transferred pattern. Through processing the Pt electrode on the glass substrate and protecting the Pt electrode with the thin layer PDMS except the part of the exposed electrode, the electrode substrate was obtained. By half-curing bonding of the PDMS cover plate and electrode substrate, the PDMS-glass chip with heating electrodes, temperature detecting electrodes and high-voltage CE electrodes was obtained. The ANSYS simulation analysis shows that the thermal inertia is small and the tempe-rature distribution effect is good when the chip is heated.

  8. Stretchable and bendable carbon nanotube on PDMS super-lyophobic sheet for liquid metal manipulation (United States)

    Kim, Daeyoung; Jung, Daewoong; Yoo, Jun Hyeon; Lee, Yunho; Choi, Wonjae; Lee, Gil S.; Yoo, Koangki; Lee, Jeong-Bong


    We report a vertically-aligned carbon nanotube (CNT) forest on polydimethylsiloxane (PDMS) sheet as a novel widely stretchable and bendable anti-wetting super-lyophobic surface for naturally oxidized gallium-based liquid metals. The vertically-aligned CNT has inherent chemical inertness and a hierarchical texture combining micro/nanoscale roughness; these two characters render the developed sheet as a super-lyophobic substrate against gallium-based liquid metals. The vertically-aligned CNT forest was first grown on Si substrate and then transferred onto a PDMS sheet by imprinting. It was found that the transferred CNT on the PDMS sheet maintained its vertically-aligned nature as well as hierarchical micro/nano surface morphology. It was found that the static contact angles of the gallium-based liquid metal droplet on the CNT on Si and on the CNT on PDMS were both greater than 155° and the contact angle hysteresis on the CNT on Si was 4° and that on the transferred CNT on PDMS was 19°. These measurement results showed that the surface retains a super-lyophobic property before and after the CNT transfer onto PDMS. We tested the CNT on PDMS sheet for its mechanical flexibility using stretching (50% and 100%) and bending (curvature of 0.1 and 0.4 mm-1). We carried out a bouncing test and a rolling test on the stretched/bent CNT on the PDMS sheet and the results confirmed that the flexible sheet maintains anti-wetting characteristics under bending or stretching conditions.

  9. Displacement and strain field assessment of PDMS using digital image correlation


    Mendonça, B; Ribeiro, J. E.; Lopes, H.; martins, p; M. A. P. Vaz


    The main goal of this work is the characterization of the hyper-elastic mechanical behaviour of PDMS. The special specimens of PDMS (Sylgard® 184) were tested in a bi-axial tensile machine. The displacement and strain fields were measured using a commercial digital image correlation system (ARAMIS of GOM) during the tensile test. The experimental measurements are compared with numerical simulations, which use the most popular algorithms of constitutive models to characterize the hyper-elastic...

  10. Displacement and strain field assessment of PDMS using digital image correlation


    Mendonça, B; Ribeiro, J. E.; Lopes, H.; martins, p; M. A. P. Vaz; Gomes, S.


    The main goal of this work is to characterize the hyper-elastic mechanical behaviour of PDMS. For that, were made-up special specimens of PDMS (Sylgard® 184) for test them in bi-axial tensile machine. During the tensile test was used a commercial digital image correlation system (ARAMIS of GOM) to obtain de displacement and strain fields. These measurements are compared with numerical simulations which uses the more popular algorithms of constitutive models.

  11. Direct transfer of multilayer graphene grown on a rough metal surface using PDMS adhesion engineering (United States)

    Jang, Heejun; Kang, Il-Suk; Lee, Youngbok; Cha, Yun Jeong; Yoon, Dong Ki; Ahn, Chi Won; Lee, Wonhee


    The direct transfer of graphene using polydimethylsiloxane (PDMS) stamping has advantages such as a ‘pick-and-place’ capability and no chemical residue problems. However, it is not easy to apply direct PDMS stamping to graphene grown via chemical vapor deposition on rough, grainy metal surfaces due to poor contact between the PDMS and graphene. In this study, graphene consisting of a mixture of monolayers and multiple layers grown on a rough Ni surface was directly transferred without the use of an adhesive layer. Liquid PDMS was cured on graphene to effect a conformal contact with the graphene. A fast release of graphene from substrate was achieved by carrying out wet-etching-assisted mechanical peeling. We also carried out a thermal post-curing of PDMS to control the level of adhesion between PDMS and graphene and hence facilitate a damage-free release of the graphene. Characterization of the transferred graphene by micro-Raman spectroscopy, SEM/EDS and optical microscopy showed neither cracks nor contamination from the transfer. This technique allows a fast and simple transfer of graphene, even for multilayer graphene grown on a rough surface.

  12. Comparison of dielectric properties of polydimethylsiloxane (PDMS) grafted polyacrylates/nano alumina and nano silica composites (United States)

    Murudkar, Vrishali V.; Gaonkar, Amita A.; Deshpande, V. D.; Mhaske, S. T.


    Polydimethylsiloxane possess very poor mechanical properties. However, typically the initial modulus and durability of material is low and to improve this aspect a reinforcement phase is required. For the composite to be effective the filler must be with large aspect ratio i.e. with large surface area to volume ratio. Nano alumina (Al2O3) and nano silica (SiO2) are materials of choice for nanocomposite design. Grafted Polydimethylsiloxane (G-PDMS) and nano alumina and nano Silica composites have been prepared, by solvent casting method. FTIR study reveals that there is bonding overlap in G-PDMS/SiO2 nano composites. In dielectric study, it is observed that G-PDMS/SiO2 nano composites were more conducting in nature than G-PDMS/ Al2O3 nano composites. G-PDMS/ Al2O3 nano composites showed enhanced dielectric constant and less loss of energy than G-PDMS/SiO2 nano composites.

  13. Solvent Recovery from Soybean Oil/Hexane Miscella by PDMS Composite Membrane

    Institute of Scientific and Technical Information of China (English)

    CAI Weibin; SUN Yanzhi; PIAO Xianglan; LI Jiding; ZHU Shenlin


    Traditional solvent recovery in the extraction step of edible oil processing is distillation,which consumes large amounts of energy.If the distillation is replaced by membrane process,the energy consumption can be reduced greatly.In this work,two kinds of membrane,PDMS(polydimethylsiloxane) composite membrane and Zeolite filled PDMS membrane were prepared,in which asymmetric microporous PVDF(polyvinylidenefluoride) membrane prepared with phase inversion method was functioned as the microporous supporting layer in the flat-plate composite membrane.The different function compositions of the PDMS/PVDF composite membranes were characterized by reflection Fourier transform infrared(FTIR) spectroscopy.The surface and section of PDMS/PVDF composite membranes were investigated by scanning electron microscope(SEM).The PDMS NF(nanofiltration) membranes were then applied in the recovery of hexane from soybean oil/hexane miscellas(1:3,mass ratio).The effects of pressure(0.5-1.5 MPa),cross-linking temperature and PDMS layer thickness on membrane performances were investigated.The results indicated that both two kinds of NF membranes were promising for solvent recovery,and zeolite filled in PDMS NF membrane could enhance the separation performance.


    Directory of Open Access Journals (Sweden)

    Aliona Novac


    Full Text Available : Among the specimens of Mytilus galloprovincialis Lmk. from the Black Sea, function of the color of the ostracum (brown, dark blue or brown with blue stripes, one can differentiate several forms. These colors are genetically determined (Stolbova, Pirkova, Ladyghina, 1996; Scherban, 2000; Shurova, 2001. The present paper analyzes the situation of these phenotypic groups, using specimens sampled at different depths in the area of Agigea dike.

  15. Comparison of structural health assessment capabilities in epoxy – carbon black and epoxy – carbon nanotube nanocomposites

    Directory of Open Access Journals (Sweden)

    F. Inam


    Full Text Available A novel method for comparing structural health of different types of brittle epoxy nanocomposites filled with carbon nanostructured fillers is presented. Epoxy – 0.2 vol% carbon black (CB and epoxy – 0.2 vol% carbon nanotube (CNT nanocomposite bars were prepared by calendering and thermal curing. Nanocomposite bars were subjected to Vickers diamond indentation to produce sub-surface damage. Electrical conductivities were analysed by 4-point method to estimate the structural damage caused by indentation. For comprehensive comparison, fracture toughness and percolation threshold were analysed as well. Because of the systematically induced indentation damage, a sharp decrease of 89% was observed in the electrical conductivity of epoxy – CNT nanocomposite as compared to 25% in the electrical conductivity of epoxy – CB nanocomposite. CNTs impart superior damage sensing capability in brittle nanocomposite structures, in comparison to CB, due to their high aspect ratio (fibrous nature and high electrical conductivity.

  16. Antibacterial and anticancer PDMS surface for mammalian cell growth using the Chinese herb extract paeonol(4-methoxy-2-hydroxyacetophenone) (United States)

    Jiao, Jiajia; Sun, Lili; Guo, Zaiyu; Hou, Sen; Holyst, Robert; Lu, Yun; Feng, Xizeng


    Polydimethylsiloxane (PDMS) is widely used as a cell culture platform to produce micro- and nano-technology based microdevices. However, the native PDMS surface is not suitable for cell adhesion and is always subject to bacterial pollution and cancer cell invasion. Coating the PDMS surface with antibacterial or anticancer materials often causes considerable harm to the non-cancer mammalian cells on it. We have developed a method to fabricate a biocompatible PDMS surface which not only promotes non-cancer mammalian cell growth but also has antibacterial and anticancer activities, by coating the PDMS surface with a Chinese herb extract, paeonol. Coating changes the wettability and the elemental composition of the PDMS surface. Molecular dynamic simulation indicates that the absorption of paeonol onto the PDMS surface is an energy favourable process. The paeonol-coated PDMS surface exhibits good antibacterial activity against both Gram-positive and Gram-negative bacteria. Moreover considerable antibacterial activity is maintained after the coated surface is rinsed or incubated in water. The coated PDMS surface inhibits bacterial growth on the contact surface and promotes non-cancer mammalian cell growth with low cell toxicity; meanwhile the growth of cancer cells is significantly inhibited. Our study will potentially guide PDMS surface modification approaches to produce biomedical devices.

  17. Online single particle measurements of black carbon coatings, structure and optical properties (United States)

    Allan, James; Liu, Dantong; Taylor, Jonathan; Flynn, Michael; Williams, Paul; Morgan, William; Whitehead, James; Alfarra, Rami; McFiggans, Gordon; Coe, Hugh


    The impacts of black carbon on meteorology and climate remain a major source of uncertainty, owing in part to the complex relationship between the bulk composition of the particulates and their optical properties. A particular complication stems from how light interacts with particles in response to the microphysical configuration and any 'coatings', i.e. non-black carbon material that is either co-emitted or subsequently obtained through atmospheric processing. This may cause the particle to more efficiently absorb or scatter light and may even change the sign of its radiative forcing potential. While much insight has been gained through measurements of bulk aerosol properties, either while suspended or after collection on a filter or impactor substrate, this does not provide a complete picture and thus may not adequately constrain the system. Here we present an overview of recent work to better constrain the properties of black carbon using online, in situ measurements of single particles, primarily using a Single Particle Soot Photometer (SP2). We have developed novel methods of inverting the data produced and combining the different metrics derived so as to give the most effective insights into black carbon sources, processes and properties. We have also used this measurement in conjunction with other instruments (sometimes in series) and used the data to challenge many commonly used models of optical properties such as core-shell Mie, Rayleigh-Debeye-Gans and effective medium. This work has been carried out in a variety of atmospheric environments and with laboratory-produced soots, e.g. from a diesel engine rig. Highlights include the finding that with real-world atmospheric aerosols, bulk optical measurements may be insufficient to derive brown carbon parameters without detailed morphological data. We also show that the enhancement of absorption for both ambient and laboratory generated particles only occurs after the coating mass fraction reaches a certain

  18. Black to Black

    DEFF Research Database (Denmark)

    Langkjær, Michael Alexander


    ’s a lifestyle I enjoy.” For Monáe, the tuxedo is both working clothes and a superhero uniform. Together with futuristic references to Fritz Lang’s dystopian Metropolis, her trademark starched shirt and tuxedo also recall Weimar and pre-war Berlin. While outwardly dissimilar, Sioux’s and Monáe’s shared black...... suggested that appreciation of the highly personal motives of both Siouxsie Sioux and Janelle Monáe in wearing black may be achieved via analogies with the minimalist sublime of American artists Frank Stella’s and Ad Reinhardt’s black canvasses....

  19. Geodesic Structures of Lifshitz Black Holes in 2+1 Dimensions

    CERN Document Server

    Cruz, Norman; Villanueva, J R


    We present an study of the geodesic equations of a black hole spacetime which is a solution of the three-dimensional NMG theory and is asymptotically Lifshitz with $z=3$ and $d=1$ found in [Ayon-Beato E., Garbarz A., Giribet G. and Hassaine M., Phys. Rev.{\\bf D} 80, 104029 (2009)]. By means of the corresponding effective potentials for massive particles and photons we find the allowed motions by the energy levels. Exact solutions for radial and non radial geodesics are given in terms of the Weierstrass elliptic $\\wp$, $\\sigma$, and $\\zeta$ functions.

  20. Kinetics and equilibrium partitioning of dissolved BTEX in PDMS and POM sheets. (United States)

    Nam, Go-Un; Bonifacio, Riza Gabriela; Kwon, Jung-Hwan; Hong, Yongseok


    Passive sampling of volatile organic chemicals from soil and groundwater is primarily important in assessing the status of environmental contamination. A group of low molecular weight pollutants usually found in petroleum fuels, benzene, toluene, ethylbenzene, and xylenes (BTEX) was studied for its kinetics and equilibrium partitioning with single-phase passive samplers using polydimethylsiloxane (PDMS) and polyoxymethylene (POM) as sorbing phase. PDMS (1 mm) and POM (0.076 mm) sheets were used for sorption of BTEX and concentrations were analyzed using GC-FID. The equilibrium absorption and desorption of PDMS in water was achieved after 120 min while POM sheets absorbed up to 35 days and desorbed in 7 days. The kinetic rate constants in PDMS is higher than in POM up to 3 orders of magnitude. Logarithms of partition coefficient were determined to be in the range of 1.6-2.8 for PDMS and 2.1-3.1 for POM. The results indicate that POM is a stronger sorbent for BTEX and has slower equilibration time than PDMS. The partitioning process for both polymers was found to be enthalpy-driven by measurement of K d values at varying temperatures. K d values increase at low temperature and high ionic strength conditions. Presence of other gasoline components, as well as dissolved organic matter, did not significantly affect equilibrium partitioning. A good 1:1 correlation between the measured and the predicted concentrations was established on testing the potential application of the constructed PDMS sampler on natural soils and artificial soils spiked with gasoline-contaminated water.

  1. Investigation Into Accessible Surface Vinyl Concentrations of Nonstoichiometric PDMS Microspheres from Hydrosilylation Reactions and Their Further Crosslinking Reactions

    DEFF Research Database (Denmark)

    Ma, Baoguang; Hansen, Jens Henrik; Hvilsted, Søren


    The introduction of surface vinyl groups to PDMS microspheres broadens the latter's applicability range since the microspheres can be further functionalized or crosslinked into elastomers. Quantification of the surface vinyl concentration of PDMS microspheres is therefore essential. Here, a novel...... for cured silicones. Vinyl functional PDMS microspheres are mixed with a hydride crosslinker and non-reactive silicone oil to create a system which allows for extensive crosslinking. Both visual observations and rheological studies show that a robust macroscopic PDMS elastomer is obtained upon crosslinking....... Furthermore, the influence of stoichiometric imbalance, and the weight fraction of silicone oil on the terminal storage modulus of the macroscopic PDMS elastomer, is investigated. The wide range of stoichiometries facilitating crosslinking between the PDMS microspheres and the hydride crosslinker found...

  2. High-gain dipole antenna using polydimethylsiloxane-glass microsphere (PDMS-GM) substrate for 5G applications (United States)

    Muhamad, Wan Asilah Wan; Ngah, Razali; Jamlos, Mohd Faizal; Soh, Ping Jack; Ali, Mohd Tarmizi


    A new dipole antenna designed using polydimethylsiloxane-glass microsphere (PDMS-GM) substrate is presented. The PDMS-GM substrate offered a lower permittivity of 1.85 compared to pure PDMS of 2.7. This resulted in a wide operating frequency range from 19 GHz up to more than 45 GHz, indicating a bandwidth of more than 28 GHz. The proposed PDMS-GM antenna featured a gain of up to 13.3 dB compared to pure PDMS which only produced 13 GHz of bandwidth and 5.5 dB gain. Instead of wide bandwidth and high gain, the proposed antenna is capable of becoming water resistant by covering its radiator and SMA connector. Such capabilities of the new PDMS-GM antenna indicated suitability for the fifth-generation (5G) wireless communication systems.

  3. Novel method to prepare multiwalled carbon nanotube/poly(dimethyl siloxane) (MWCNT/PDMS) non-conducting composites

    DEFF Research Database (Denmark)

    Goswami, Kaustav; Daugaard, Anders Egede; Skov, Anne Ladegaard

    due to a localized distribution of CNT. Ultrasonicated and dispersed multiwalled CNTs were mixed with short chain ,- vinyl terminated PDMS. When the whole mixture containing dispersed CNT and short chain PDMS was irradiated with UV radiation in presence of deficient amount of hexa functional thiol...... PDMS crosslinker and a photoinitiator, hyperbranced PDMS layer was formed over the CNTs. The prepared hyperbranched CNTs were mixed in different weight ratios (0.33%, 0.66%, 1%) with long chain ,- vinyl terminated PDMS and crosslinked subsequently with the same hexa functional thiol PDMS via UV...... photoinitiated thiol-ene chemistry to obtain the networks. Rheology of the prepared networks showed a gradual decrease in storage modulus (G’) in the entire frequency range as the amount of CNT was increased due to a reduction in crosslinking density imposed by the CNT was increased due to a reduction...

  4. Probing the magnetic field structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

    CERN Document Server

    Gold, Roman; Johnson, Michael D; Doeleman, Sheperd S


    Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic-field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical (MHD) simulations to model thermal synchrotron emission from the Galactic Center source Sagittarius A$^\\ast$ (Sgr A*). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability (MRI) as well as models with large-scale ordered fields in magnetically-arrested disks (MAD). We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford-...

  5. Nanostructure of PDMS-TEOS-PrZr hybrids prepared by direct deposition of gamma radiation energy (United States)

    Lancastre, Joana J. H.; Falcão, António N.; Margaça, Fernanda M. A.; Ferreira, Luís M.; Miranda Salvado, Isabel M.; Almásy, László; Casimiro, Maria H.; Meiszterics, Anikó


    Organic-inorganic materials have been the object of intense research due to their wide range of properties and therefore innumerous applications. We prepared organic-inorganic hybrid materials by direct energy deposition on a mixture of polydimethylsiloxane silanol terminated (33 wt% fixed content), tetraethylorthosilicate and a minor content of zirconium propoxide that varied from 1 to 5 wt% using gamma radiation from a Co-60 source. The samples, dried in air at room temperature, are bulk, flexible and transparent. Their nanostructure was investigated by small angle neutron scattering. It was found that the inorganic oxide network has fractal structure, which becomes denser as the zirconium propoxide content decreases. The results suggest that oxide nanosized regions grow from the OH terminal group of PDMS which are the condensation seeds. Their number and position remains unaltered with the variation of zirconium propoxide content that only affects their microstructure. A model is proposed for the nanostructure of the oxide network that develops in the irradiation processed hybrid materials.

  6. Surface studies on benzophenone doped PDMS microstructures fabricated using KrF excimer laser direct write lithography

    Energy Technology Data Exchange (ETDEWEB)

    Kant, Madhushree Bute; Shinde, Shashikant D. [Department of Physics, University of Pune, Pune 411007 (India); Bodas, Dhananjay [Centre for Nanobioscience, Agharkar Research Institute, Agharkar road, Pune 411004 (India); Patil, K.R. [Center for Materials Characterization, National Chemical Laboratories, Pune 411008 (India); Sathe, V.G. [UGC DAE Inter University Consortium, Indore 452017 (India); Adhi, K.P. [Department of Physics, University of Pune, Pune 411007 (India); Gosavi, S.W., E-mail: [Department of Physics, University of Pune, Pune 411007 (India)


    Graphical abstract: - Highlights: • Use of KrF Laser micromachining for Lab-On-Chip applications at lower fluence. • Addition of Benzophenone in PDMS enhances its self development sensitivity. • Benzophenone helps efficient energy transfer for equal density of bond scissioning. • Correlation of chemical composition with laser dose and microstructure. • Microstructures with well defined clean sidewalls. - Abstract: This paper discusses microfabrication process for benzophenone doped polydimethylsiloxane (PDMS) using laser lithography. KrF excimer laser of 248 nm with 20 ns pulse width at repetition rate of 1 Hz was used for microfabrication of undoped and benzophenone doped PDMS. The doped-PDMS shows sensitivity below 365 nm, permitting processing under ambient light. The analysis of etch depth revealed that doped PDMS shows self developable sensitivity at lower fluence of ∼250 mJ/cm{sup 2}. The unexposed and exposed surface was studied using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Scanning electron microscopy (SEM). Spectrocopic analysis indicated increase in C-O, C=O, Si-O{sub 3} and Si-O{sub 4} bonding at the expense of Si-C and Si-O{sub 2} bonds of PDMS. In case of laser exposed doped-PDMS, removal of benzophenone from probe depth of spectroscopy was observed. Whereas the surface morphology of exposed and unexposed doped-PDMS was observed to be same, indicating clean development of PDMS micropatterns. The present study indicates that addition of 3.0 wt.% benzophenone in PDMS enhance self development sensitivity of PDMS. The self developable results on doped-PDMS are quite encouraging for its potential use in point of care Lab-On-Chip applications, for fabricating micropatterns using direct write laser lithography technology.

  7. Rapid and low-cost fabrication of polystyrene-based molds for PDMS microfluidic devices using a CO2 laser

    KAUST Repository

    Li, Huawei


    In this article, we described a rapid and low-cost method to fabricate polystyrene molds for PDMS microfluidic devices using a CO2 laser system. It takes only several minutes to fabricate the polystyrene mold with bump pattern on top of it using a CO2 laser system. The bump pattern can be easily transferred to PDMS and fabricate microchannles as deep as 3μm on PDMS. © (2012) Trans Tech Publications, Switzerland.

  8. Stable modification of PDMS surface properties by plasma polymerization: application to the formation of double emulsions in microfluidic systems. (United States)

    Barbier, Valessa; Tatoulian, Michaël; Li, Hong; Arefi-Khonsari, Farzaneh; Ajdari, Armand; Tabeling, Patrick


    We describe a method based on plasma polymerization for the modification and control of the surface properties of poly(dimethylsiloxane) (PDMS) surfaces. By depositing plasma polymerized acrylic acid coatings on PDMS, we succeeded to fabricate stable (several days) hydrophilic and patterned hydrophobic/hydrophilic surfaces. We used this approach to generate direct and (for the first time in this material) double emulsions in PDMS microchannels.

  9. Structural, mechanical and electrical characterization of epoxy-amine/carbon black nanonocomposites

    Directory of Open Access Journals (Sweden)


    Full Text Available This work presents an insight into the effect of preparation procedure and the filler content on both electrical and mechanical properties of a nanocomposite system. For the preparation of the nanocomposites diglycidyl ether of bisphenol A (DGEBA was used with triethylenetetramine (TETA as a curing agent. As fillers carbon black (CB nanoparticles with size from 25 to 75 nm were used. The characterization was done using Dynamic Mechanical Analysis (DMA, Dielectric Relaxation Spectroscopy (DRS, Differential Scanning Calorimetry (DSC, Wide Angle X-ray Diffraction (WAXD and electrical conductivity measurements. The dependence of the dynamic mechanical and dielectric parameters (E′, E″, tanδ, ε', ε″, σ and Tg is associated with the filler content and is controlled by the employed curing conditions. An increase in electrical conductivity, which is observed at about 1% w/w of carbon black, indicates the creation of conducting paths and is associated with the Maxwell Wagner Sillars (MWS relaxation, probably due to the formation of aggregated microstructures in the bulk composite..

  10. 基于微流控技术的新型PDMS平面微阀%Development and Characterization of Novel Planar PDMS Microvalve for Integrated Microfluidic Systems

    Institute of Scientific and Technical Information of China (English)

    倪君辉; 李蓓智; 杨建国; LIN Qiao


    This paper presented a novel PDMS planar vajve for integrated microfluidic syslems. It featured use of a simple centered stopper-flap based planar configuration, realizing the incorporation of flap, stopper and microflow channels into one single PDMS layer,which aUowed for simple structure and easy system integration. The valve could be easily fahricated using standard PDMS replica molding technique. Test results demonstrate this valve is able to regulate fluid flow efficietly wich a small reverse flow of 0. 1 mL/min, and a high ratio of forward flow to reverse flow rale of up to 41∶ 1. This microvalve can be potemially used in various microfluidic systems , due to its planar cunfiguralion , simple fabrication , and use of low-cost PDMS material.%针对常规微阀结构较为复杂,存在着制作成本较高、难于加工和不易系统集成等问题,提出了一种设计简单的柔性阀片-阀塞结构的PDMS平面微阀的研究.微阀的制作采用了标准PDMS模塑法微细加工工艺.测试结果表明微阀工作性能良好,反向泄漏量可以减少到0.1 mL/min,而微阀的正/反向流量比可以达到41:1,满足了微流体控制系统对流量调节的要求,可广泛应用于各种微流控系统中.

  11. Breast cancers from black women exhibit higher numbers of immunosuppressive macrophages with proliferative activity and of crown-like structures associated with lower survival compared to non-black Latinas and Caucasians. (United States)

    Koru-Sengul, Tulay; Santander, Ana M; Miao, Feng; Sanchez, Lidia G; Jorda, Merce; Glück, Stefan; Ince, Tan A; Nadji, Mehrad; Chen, Zhibin; Penichet, Manuel L; Cleary, Margot P; Torroella-Kouri, Marta


    Racial disparities in breast cancer incidence and outcome are a major health care challenge. Patients in the black race group more likely present with an early onset and more aggressive disease. The occurrence of high numbers of macrophages is associated with tumor progression and poor prognosis in solid malignancies. Macrophages are observed in adipose tissues surrounding dead adipocytes in "crown-like structures" (CLS). Here we investigated whether the numbers of CD163+ tumor-associated macrophages (TAMs) and/or CD163+ CLS are associated with patient survival and whether there are significant differences across blacks, non-black Latinas, and Caucasians. Our findings confirm that race is statistically significantly associated with the numbers of TAMs and CLS in breast cancer, and demonstrate that the highest numbers of CD163+ TAM/CLS are found in black breast cancer patients. Our results reveal that the density of CD206 (M2) macrophages is a significant predictor of progression-free survival univariately and is also significant after adjusting for race and for HER2, respectively. We examined whether the high numbers of TAMs detected in tumors from black women were associated with macrophage proliferation, using the Ki-67 nuclear proliferation marker. Our results reveal that TAMs actively divide when in contact with tumor cells. There is a higher ratio of proliferating macrophages in tumors from black patients. These findings suggest that interventions based on targeting TAMs may not only benefit breast cancer patients in general but also serve as an approach to remedy racial disparity resulting in better prognosis patients from minority racial groups.

  12. Surface modification of PDMS microchips with poly(ethylene glycol) derivatives for μTAS applications. (United States)

    de Campos, Richard Piffer Soares; Yoshida, Inez Valeria Pagotto; da Silva, José Alberto Fracassi


    In this work is presented a method for the modification of native PDMS surface in order to improve its applicability as a substrate for microfluidic devices, especially in the analysis of nonpolar analytes. Therefore, poly(ethylene glycol) divinyl ether modified PDMS substrate was obtained by surface modification of native PDMS. The modified substrate was characterized by attenuated total reflectance infrared spectroscopy, water contact angle measurements, and by evaluating the adsorption of rhodamine B and the magnitude of the EOF mobility. The reaction was confirmed by the spectroscopic evaluation. The formation of a well-spread water film over the surface immediately after the modification was an indicative of the modified surface hydrophilicity. This characteristic was maintained for approximately ten days, with a gradual return to a hydrophobic state. Fluorescence assays showed that the nonpolar adsorption property of PDMS was significantly decreased. The EOF mobility obtained was 3.6 × 10(-4) cm(2) V(-1) s(-1) , higher than the typical values found for native PDMS. Due to the better wettability promoted by the modification, the filling of the microchannels with aqueous solutions was facilitated and trapping of air bubbles was not observed.

  13. Air plasma assisting microcontact deprinting and printing for gold thin film and PDMS patterns. (United States)

    Gou, Hong-Lei; Xu, Jing-Juan; Xia, Xing-Hua; Chen, Hong-Yuan


    In this paper, we present a simple method to fabricate gold film patterns and PDMS patterns by air plasma assisting microcontact deprinting and printing transfer approaches. Chemical gold plating is employed instead of conventional metal evaporation or sputtering to obtain perfect gold film both on flat and topographic PDMS chips, and complicated SAM precoating is replaced by simple air plasma treatment to activate both the surface of gold film and PDMS. In this way, large area patterns of conductive gold film and PDMS patterns could be easily obtained on the elastomeric PDMS substrate. Both the chemical plating gold film and transferred gold film were of good electrochemical properties and similar hydrophilicity with smooth and conductive surface, which made it potentially useful in microfluidic devices and electronics. The gold transfer mechanism is discussed in detail. For typical applications, a cell patterning chip based on the gold pattern was developed to imply the interfacial property, and dielectrophoresis control of live cells was carried out with the patterned gold as interdigital electrodes to show the conductivity.

  14. Hybrid microsystem with functionalized silicon substrate and PDMS sample operating microchannel: A reconfigurable microfluidics scheme

    Institute of Scientific and Technical Information of China (English)


    A hybrid microsystem with separately functioned temperature controlling substrate and sample operating fluidic microchannel was developed to demonstrate a reconfigurable microfluidics scheme.The temperature controlling substrate integrated a micro heater and a temperature sensor by using traditional silicon-based micromechanical system(MEMS)technique,which guaranteed high performance and robust reliability for repeatable usage.The sample operating fluidic microchannel was prepared by poly-(dimethylsiloxane) (PDMS)based soft lithography technique,which made it cheap enough for disposable applications.The PDMS microchannel chip was attached to the temperature controlling substrate for reconfigurable thermal applications.A thin PDMS film was used to seal the microchannel and bridge the functionalized substrate and the sample inside the channel,which facilitated heat transferring and prevented sample contaminating the temperature controlling substrate.Demonstrated by a one dimensional thermal resistance model,the thin PDMS film was important for the present reconfiguration applications.Thermal performance of this hybrid microsystem was examined,and the experimental results demonstrated that the chip system could work stably over hours with temperature variation less than 0.1oC.Multiple PDMS microchannel chips were tested on one heating substrate sequentially with a maximum intra-chip temperature difference of 1.0oC.DNA extracted from serum of a chronic hepatitis B virus(HBV)patient was amplified by this hybrid microsystem and the gel electrophoresis result indicated that the present reconfigurable microfluidic scheme worked successfully.

  15. 3-cm Fine Structure Masers: A Unique Signature of Supermassive Black Hole Formation via Direct Collapse in the Early Universe

    CERN Document Server

    Dijkstra, Mark; Loeb, Abraham


    The direct collapse black hole (DCBH) scenario describes the isothermal collapse of a pristine gas cloud directly into a massive, M_BH=10^4-10^6 M_sun black hole. In this paper we show that large HI column densities of primordial gas at T~10^4 K with low molecular abundance - which represent key aspects of the DCBH scenario - provide optimal conditions for pumping of the 2p-level of atomic hydrogen by trapped Lyman alpha (Lya) photons. This Lya pumping mechanism gives rise to inverted level population of the 2s_1/2-2p_3/2 transition, and therefore to stimulated fine structure emission at 3.04 cm (rest-frame). We show that simplified models of the DCBH scenario amplify the CMB by up to a factor of 10^5, above which the maser saturates. Hyperfine splitting of the 3-cm transition gives rise to a characteristic broad (FWHM ~ tens of MHz in the observers frame) asymmetric line profile. This signal subtends an angular scale of ~ 1-10 mas, which translates to a flux of ~ 0.3-3 microJy, which is detectable with ultra...

  16. Genetic diversity and population structure of black Dahe pig based on DNA sequences analyses of mitochondrial and nuclear genes. (United States)

    Tang, Lizhou; Yu, Long; Wang, Junjie; Liu, Chao; Shi, Xiaodong; Ding, Wei; Zhu, Lei; Guo, Songchang


    To investigate the genetic diversity and population structure of black Dahe pigs, we collected 175 samples from 5 local populations and sequenced them using a combination of two selected molecular markers for mitochondrial cytochrome b and Major Histocompatibility Complex (MHC) DRB. Overall, the results of AMOVA and phylogenetic tree and gene flow analyses detected high levels of gene flow among the five populations, particularly individual pigs from Dahe town (Pop1) or Yingshang town (Pop2) to other populations (Pop3, Pop4, and Pop5). The genetic diversity analyses showed that the diversity indices of the five populations did not vary significantly, but they were much lower than those of other Chinese pig species. These results suggest that distinct gene flow, unstable population pattern, and lower genetic diversity have been influenced mainly by human introductions for economic ends. These findings provide genetic information that could be used for the preservation and further genetic improvement of the black Dahe pig, as well as an important reference for the evaluation, conservation, and utilization of the genetic resources of this breed.

  17. Fouling release nanostructured coatings based on PDMS-polyurea segmented copolymers

    KAUST Repository

    Fang, Jason


    The bulk and surface characteristics of a series of coatings based on PDMS-polyurea segmented copolymers were correlated to their fouling release performance. Incorporation of polyurea segments to PDMS backbone gives rise to phase separation with the extensively hydrogen bonded hard domains creating an interconnected network that imparts mechanical rigidity. Increasing the compositional complexity of the system by including fluorinated or POSS-functionalized chain extenders or through nanoclay intercalation, confers further thermomechanical improvements. In analogy to the bulk morphology, the surface topography also reflects the compositional complexity of the materials, displaying a wide range of motifs. Investigations on settlement and subsequent removal of Ulva sporelings on those nanostructured surfaces indicate that the work required to remove the microorganisms is significantly lower compared to coatings based on standard PDMS homopolymer. All in all, the series of materials considered in this study demonstrate advanced fouling release properties, while exhibiting superior mechanical properties and, thus, long term durability. © 2010 Elsevier Ltd.

  18. Microfabrication of Bubbular Cavities in PDMS for Cell Sorting and Microcell Culture Applications

    Institute of Scientific and Technical Information of China (English)

    Ut-Binh T.Giang; Michael R.King; Lisa A.DeLouise


    We describe a novel technique, low surface energy Gas Expansion Molding (GEM), to fabricate microbubble arrays in polydimethylsiloxane (PDMS) which are incorporated into parallel plate flow chambers and tested in cell sorting and microcell culture applications. This architecture confers several operational advantages that distinguish this technology approach from currently used methods. Herein we describe the GEM process and the parameters that are used to control microbubble formation and a Vacuum-Assisted Coating (VAC) process developed to selectively and spatially alter the PDMS surface chemistry in the wells and on the microchannel surface. We describe results from microflow image visualization studies conducted to investigate fluid streams above and within microbubble wells and conclude with a discussion of cell culture studies in PDMS.

  19. PDMS Rod-SBSE System Coupled with Gas Chromatography for Determination of PAHs in Aqueous Samples

    Institute of Scientific and Technical Information of China (English)

    CHENG Chuan-xian; PEI Hai-rong; LAN Xiao-zheng


    A method for the analysis of trace polycyclic aromatic hydrocarbons(PAHs) in aqueous samples has been established by polydimethylsiloxane(PDMS) rod aided stir bar sorptive extraction(SBSE).The homemade PDMS rod has a size of 30 mm×3 mm o.d.with a volume of ca.200 μL,stable in thermal desorption process.The enriched PAHs by the PDMS rod were released in a homemade thermal desorption system coupled with gas chromatography.Experimental parameters for extraction of six PAHs were optimized including extraction time,pH,ionic strength and temperature of solution.The procedure has good recoveries of 80.0%-100.3% and very low limits of detection of 4.0-33 ng/L.PAHs in rain and river water were analyzed by this method.

  20. Surface tension-induced PDMS micro-pillars with controllable tips and tilt angles

    KAUST Repository

    Li, Huawei


    This paper reports a novel method to fabricate three-dimensional (3D) polydimethylsiloxane (PDMS) micro-pillars using a CO2 laser-machined poly(methyl methacrylate) (PMMA) mold with through-holes. This method eliminates the requirements of expensive and complicated facilities to fabricate a 3D mold. The micro-pillars were formed by the capillary force that draws PDMS into the through-holes of the PMMA mold. The tilt angles of the micro-pillars depend on the tilt angles of the through-holes in the mold, and the concave and convex micro-lens tip shapes of the PDMS micro-pillars can be modified by changing the surface wettability of the PMMA through-holes.

  1. A PDMS-Based Microfluidic Hanging Drop Chip for Embryoid Body Formation

    Directory of Open Access Journals (Sweden)

    Huei-Wen Wu


    Full Text Available The conventional hanging drop technique is the most widely used method for embryoid body (EB formation. However, this method is labor intensive and limited by the difficulty in exchanging the medium. Here, we report a microfluidic chip-based approach for high-throughput formation of EBs. The device consists of microfluidic channels with 6 × 12 opening wells in PDMS supported by a glass substrate. The PDMS channels were fabricated by replicating polydimethyl-siloxane (PDMS from SU-8 mold. The droplet formation in the chip was tested with different hydrostatic pressures to obtain optimal operation pressures for the wells with 1000 μm diameter openings. The droplets formed at the opening wells were used to culture mouse embryonic stem cells which could subsequently developed into EBs in the hanging droplets. This device also allows for medium exchange of the hanging droplets making it possible to perform immunochemistry staining and characterize EBs on chip.

  2. Uniform integration of gold nanoparticles in PDMS microfluidics with 3D micromixing (United States)

    SadAbadi, H.; Packirisamy, M.; Wuthrich, R.


    The integration of gold nanoparticles (AuNPs) on the surface of polydimethylsiloxane (PDMS) microfluidics for biosensing applications is a challenging task. In this paper we address this issue by integration of pre-synthesized AuNPs (in a microreactor) into a microfluidic system. This method explored the affinity of AuNPs toward the PDMS surface so that the pre-synthesized particles will be adsorbed onto the channel walls. AuNPs were synthesized inside a microreactor before integration. In order to improve the size uniformity of the synthesized AuNPs and also to provide full mixing of reactants, a 3D-micromixer was designed, fabricated and then integrated with the microreactor in a single platform. SEM and UV/Vis spectroscopy were used to characterize the AuNPs on the PDMS surface.

  3. Chemical sensing by band modulation of a black phosphorus/molybdenum diselenide van der Waals hetero-structure (United States)

    Feng, Zhihong; Chen, Buyun; Qian, Shuangbei; Xu, Linyan; Feng, Liefeng; Yu, Yuanyuan; Zhang, Rui; Chen, Jiancui; Li, Qianqian; Li, Quanning; Sun, Chongling; Zhang, Hao; Liu, Jing; Pang, Wei; Zhang, Daihua


    We report on a new chemical sensor based on black phosphorus/molybdenum diselenide van der Waals hetero-junctions. Due to the atomically thin nature of two-dimensional (2D) materials, surface adsorption of gas molecules can effectively modulate the band alignment at the junction interface, making the device a highly sensitive detector for chemical adsorptions. Compared to sensors made of homogeneous nanomaterials, the hetero-junction demonstrates considerably lower detection limit and higher sensitivity toward nitrogen dioxide. Kelvin probe force microscopy and finite element simulations have provided experimental and theoretical explanations for the enhanced performance, proving that chemical adsorption can induce significant changes in band alignment and carrier transport behaviors. The study demonstrates the potential of van der Waals hetero-junction as a new platform for sensing applications, and provides more insights into the interaction between gaseous molecules and 2D hetero-structures.

  4. Synthesis, characterization and lubricating effect of long chain branched polydimethylsiloxane-g-polyethylene copolymers%长支链型PDMS-g-PE共聚物的制备及其增塑润滑作用

    Institute of Scientific and Technical Information of China (English)

    金震; 范宏


    Long chain branched polydimethylsiloxane-g-polyethylene (PDMS-g-PE) copolymers were synthesized by hydrosilylation reaction between polymethylhydrosiloxane and vinyl terminated PE macromonomer. The structure and properties were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H NMR), high temperature gel permeation chromatography (HT-GPC) and differential scanning calorimetry (DSC). The effect of the hydrogen content of polymethylhydrosiloxane on the copolymer structure and properties was investigated. It was found that the molecular weight of PDMS-g-PE increased with the hydrogen content of polymethylhydrosiloxane since more PE macromonomers were grafted onto the polydimethylsiloxane main chains. The glass transition temperature (Tg) of PDMS-g-PE was extremely low, indicating the excellent molecular chain flexibility. PDMS-g-PE with more PE branched chains showed higher melting temperature (Tm) and higher melting enthalpy (ΔHm). PDMS-g-PE was used as flow modifier for HDPE. When 2% PDMS-g-PE was added to HDPE, the melting flow rate (MFR) increased by 21%, the elongation at break improved significantly and the impact strength improved a little, while the tensile strength and elastic modulus decreased slightly.%通过低含氢硅油与末端双键聚乙烯大单体的硅氢加成反应,制备了长支链型聚硅氧烷-聚乙烯接枝共聚物(PDMS-g-PE)。采用傅里叶变换红外光谱(FT-IR)、核磁共振波谱(1H NMR)、高温凝胶渗透色谱(HT-GPC)和差示扫描量热分析(DSC)表征了共聚物的结构与性能。考察了硅油含氢量对共聚物结构和热性能的影响,并将其用作HDPE的流动改性剂,研究了其增塑润滑改性效果。结果表明,硅油含氢量越高,能加成上的PE支链越多,PDMS-g-PE的分子量越大。PDMS-g-PE的聚硅氧烷主链具有极低的玻璃化温度(Tg),显示出优异的分子链柔顺性。聚乙烯支链使PDMS

  5. 高结构炭黑酸化改性的研究%Research on High Structure Carbon Black Modification of Acidification

    Institute of Scientific and Technical Information of China (English)

    孟春财; 陈建; 金永中; 张敬雨; 伍雅峰


    The experimental samples were made by changing the reaction time and acid concentration and acidizing to modify different high structure carbon black. The dispersion and stability of the modified carbon black in aqueous solution was determined by natural sedimentation method. The shading rate of each modified carbon black was detected by the laser particle size analyzer. The relationship between the surface groups of carbon black and its dispersion was analysed quantitatively by acid-base titratioa And the performance indicators were compared between the modified carbon black and carbon black pigment. The results showed that, the modified carbon black, which was prepared by the N234 carbon black and 6mol/L sulfuric acid for 8 hours, dispersed best, due to the content increase of phenolic hydroxyl and lactone. Comparing the dispersion of carbon black and the price, the modified carbon black was better than the pigment carbon black.%通过改变时间、硫酸浓度等反应条件,酸化改性不同品种炭黑,得到了实验所需试样.采用自然沉降法测定了酸化改性高结构炭黑在水溶液中的分散性及稳定性.利用激光粒度分布仪检测了每种改性炭黑的遮光率,根据酸碱滴定法定量分析了炭黑表面基团与分散性的关系,并比较了改性炭黑与色素炭黑之间的性能指标.结果表明,炭黑N234与6mol/L硫酸反应8h制备的改性炭黑分散性最佳,原因是其表面的酚羟基和内酯基含量有所增加.通过比较炭黑的分散性及市场价格,得知改性炭黑优于色素炭黑.

  6. TeraHz tuning of whispering gallery modes in a PDMS, stand-alone, stretchable microsphere

    CERN Document Server

    Madugani, Ramgopal; Ward, Jonathan M; Riordan, John Daniel; Coppola, Sara; Vespini, Veronica; Grilli, Simonetta; Finizio, Andrea; Ferraro, Pietro; Chormaic, Síle Nic


    We report on tuning the optical whispering gallery modes in a poly dimethyl siloxane-based (PDMS) microsphere resonator by more than a THz. The PDMS microsphere system consists of a solid spherical resonator directly formed with double stems on either side. The stems act like tie-rods for simple mechanical stretching of the microresonator over tens of microns, resulting in tuning of the whispering gallery modes by one free spectral range. Further investigations demonstrate that the whispering gallery mode shift has a higher sensitivity (0.13 nm/{\\mu}N) to an applied force when the resonator is in its maximally stretched state compared to its relaxed state.

  7. Monolithic PDMS Laminates for Dielectric Elastomer Transducers through Open-Air PlasmATreatment

    DEFF Research Database (Denmark)

    Hassouneh, Suzan Sager; Oubæk, Jakob; Daugaard, Anders Egede


    The present study investigates the use of an open-air plasma-treatment system for the surface modification of polydimethylsiloxane (PDMS), in order to improve layer-to-layer adhesion. The procedure presented herein is more cost efficient compared to conventional vacuum-based plasma-treatment......, and it is performed at different speeds and distances away from the nozzle, to investigate how these two parameters influence the resulting interfacial layer of two fully cured PDMS films. The plasma-treatment is determined not to alter mechanical properties compared to the single film, while peel forces...

  8. Shear and Extensional Rheometry of PDMS Tamponade Agents Used in Vitroretinal Surgery (United States)

    Day, Michael; Blanchard, Rowan-Louise; English, Rob; Dobbie, Tom; Williams, Rachel; Garvey, Michael; Wong, David


    The emulsification of low molar mass silicone oil (PDMS)-based tamponade agents used in the treatment of complex retinal detachments is a significant clinical problem leading to the patient suffering impairment of vision whilst the tamponade is in place. This is particularly the case in temporal postoperative applications where the tamponade can remain in the ocular cavity for several months. The majority of clinicians prefer to use a PDMS fluid of kinematic viscosity 1000 cS, which offers ease of manual injection. Work is progressing towards the development of tamponades with a reduced tendency to emulsify, through specific tailoring of rheology and interfacial properties. Greater knowledge of the mechanism of intraocular emulsification is being elucidated and has led to the development of `polymer modified' tamponades with enhanced performance. Such materials are formulated by the addition of a high molecular weight PDMS to the base PDMS fluid. Measurement of the shear viscosity at moderate shear rates is useful in predicting performance during manual injection into the eye. However, the determination of the behaviour in both shear and extension at high strain rates is useful in predicting resistance to intraocular emulsification and in informing future modeling studies. Initial experiments focused on rotational rheometry (shear) and capillary breakup rheometry (CaBER—extension). A range of polymer modified tamponades were characterised—based on PDMS base oils from 100-5000 cS and containing up to 30% by weight PDMS of molecular weight varying in the range 100-800 kDa. Even though the volume occupancy of the polymeric additive ranged from dilute to significantly interpenetrated, a linear response was observed in each case. However, subsequent experiments using capillary rheometry lead to the observation of non-linear behaviour and significant differences in the type of response. Systems with enhanced high strain rate tensile viscosities gave improved

  9. Static friction of biomimetic surface microstructure of PDMS under wet and dry conditions (United States)

    Yu, Haiwu; Jia, Hongduo; Gong, Ling; Li, Rong; Wang, Caiping; Wang, Xiaojie


    Smooth adhesive pad found among arthropods, amphibians, particularly tree frogs, are usually covered with surface microstructure of different shape to enhance the attachment abilities on the smooth substrate. During the last decade, it has gained more attentions in the development of anti-slippery systems by mimicking these unique characteristics. In this paper, we studied a new amphibian species newt by observing their climbing abilities on wet and dry vertical smooth surface, and found that the newts can even hang on the surface with an inclination angle more than 90° without falling. We investigated the toe pad micro-structured surface of the newt by using scanning electron microscopy (SEM), and found that an array of hexagonal cells with micro-ridges on cell borders exists for the larvae; while an array of hexagonal cells separated by microgrooves is for the adult. Inspired by these features, the biomimetic micro-structured surfaces were fabricated using a soft elastomeric material polydimethysiloxane (PDMS). Four different microstructures were chosen to study their tribological properties with a solid substrate under wet and dry conditions. The patterns of the microstructures include round pillar, hexagonal pillar, round pillars surrounded by a closed hexagonal ridge, and round pillars surrounded by a semi-closed hexagonal ridge. The static friction tests were carried out using the multi-functional surface meter TYPE12. The results showed that the area ratio of the micro pillar plays a major role in enhancing the static friction for both wet and dry conditions, while the numerical density of the micro pillar has less effect on the friction enhancement. Among the four kind specimens, the specimen with hexagonal pillars would increase the static friction more than others at the same test conditions when the pillar area ratio is lower than 40%.

  10. Magnetosphere of a Kerr black hole immersed in magnetized plasma and its perturbative mode structure

    CERN Document Server

    Yang, Huan; Lehner, Luis


    This work studies jet-like electromagnetic configurations surrounding a slowly-spinning black-hole immersed in a uniformly magnetized force-free plasma. In the first part of this work, we present a family of stationary solutions that are jet-capable. While these solutions all satisfy the force-free equations and the appropriate boundary conditions, our numerical experiments show a unique relaxed state starting from different initial data, and so one member of the family is likely preferred over the others. In the second part of this work, we analyze the perturbations of this family of jet-like solutions, and show that the perturbative modes exhibit a similar split into the trapped and traveling categories previously found for perturbed Blandford-Znajek solutions. In the eikonal limit, the trapped modes can be identified with the fast magnetosonic waves in the force-free plasma and the traveling waves are essentially the Alfven waves. Moreover, within the scope of our analysis, we have not seen signs of unstab...

  11. Mergers of Unequal Mass Galaxies: Supermassive Black Hole Binary Evolution and Structure of Merger Remnants

    CERN Document Server

    Khan, Fazeel Mahmood; Berczik, Peter; Berentzen, Ingo; Just, Andreas; Spurzem, Rainer


    Galaxy centers are residing places for Super Massive Black Holes (SMBHs). Galaxy mergers bring SMBHs close together to form gravitationally bound binary systems which, if able to coalesce in less than a Hubble time, would be one of the most promising sources of gravitational waves for the Laser Interferometer Space Antenna (LISA). In spherical galaxy models, SMBH binaries stall at a separation of approximately one parsec, leading to the "final parsec problem" (FPP). On the other hand, it has been shown that merger-induced triaxiality of the remnant in equal-mass mergers is capable of supporting a constant supply of stars on so-called centrophilic orbits that interact with the binary and thus avoid the FPP. In this paper, using a set of direct N-body simulations of mergers of initially spherically symmetric galaxies with different mass ratios, we show that the merger-induced triaxiality is able to drive unequal-mass SMBH binaries to coalescence. The binary hardening rates are high and depend only weakly on the...

  12. Clumpy accretion onto black holes. I. Clumpy-ADAF structure and radiation

    CERN Document Server

    Wang, J -M; Li, Y -R


    In this paper, we investigate the dynamics of clumps embedded in and confined by the advection-dominated accretion flows (ADAF), in which collisions among the clumps are neglected. We start from the collisionless Boltzmann equation and assume that interaction between the clumps and the ADAF is responsible for transporting angular momentum of clumps outward. The inner edge of the clumpy-ADAF is set to be the tidal radius of the clumps. We consider strong and weak coupling cases, in which the averaged properties of clumps follow the ADAF dynamics and mainly determined by the black hole potential, respectively. We get the analytical solution of the dynamics of clumps for the two cases. The velocity dispersion of clumps is one magnitude higher than the ADAF for the strong coupling case. For the weak coupling case, we find that the mean radial velocity of clumps is linearly proportional to the coefficient of the drag force. We show that the tidally disrupted clumps would lead to accumulation of the debris to form ...

  13. Special structure of mitochondrial DNA control region and phylogenetic relationship among individuals of the black rockfish, Sebastes schlegelii. (United States)

    Zhang, Hui; Zhang, Yan; Zhang, Xiumei; Song, Na; Gao, Tianxiang


    This study deals with the structure of mitochondrial DNA (mtDNA) control region (CR) of the black rockfish, Sebastes schlegelii. Two termination-associated sequences (TASs), two complementary termination-associated sequences (cTASs), and conserved sequence block (CSB), such as CSB-F, CSB-E, CSB-D, CSB1, CSB2, and CSB3, were detected in S. schlegelii. The results indicated that the structures of these blocks are similar to most marine fishes, but it is special that there are two TASs and two cTASs in the CR of S. schlegelii. One conserved region was found from 450 bp to the end of the CR, which is also a special feature of S. schlegelii. All sequences of CSB1, CSB2, and CSB3 blocks are the consensus among different individuals, which is quite different from most vertebrates. In addition, the complete mtDNA CR sequences and the first 449 bp of the CR are used to analyze the phylogenetic relationships of S. schlegelii. The phylogenetic trees show a lack of genetic structure among individuals. This study also indicated a signal that the genetic diversity might be similar between the wild and cultured individuals, which may be helpful to the fisheries management.

  14. Black holes, formation of structure, and extreme physics: the present and future of X-ray astrophysics (United States)

    Kraft, Ralph; Bautz, Mark


    X-ray astrophysics lies at the conjunction of many of the big picture questions we have about our Universe. We detect X-rays from supermassive black holes when the Universe was 7% of its present age, just after the formation of the first galaxies. Most of the baryons in the Universe are in clusters or in the filaments between collapsed structures heated to X-ray emitting temperatures. X-ray studies of the evolution of these collapsed structures provide strong constraints on cosmological parameters. Studies by future X-ray observatories of this hot filamentary gas between clusters and of halos of galaxies will provide unique windows in the processes of the early universe and formation of structure. In this presentation, we discuss the current state of X-ray astrophysics. We will present the status of and recent science highlights from the current generation of X-ray observatories. We will outline the scientific potential for missions that will soon be launched including NICER, eRosita, and a potential refly of the Hitomi mission, as well as longer term missions such as the European L2 Athena mission. Finally, we will summarize the status of the X-ray Surveyor, one of the four large mission concepts under study prior to the 2020 Astrophysics Decadal Review.

  15. Chemical Bonding and Structural Information of Black CarbonReference Materials and Individual Carbonaceous AtmosphericAerosols

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, Rebecca J.; Tivanski, Alexei V.; Marten, Bryan D.; Gilles, Mary K.


    The carbon-to-oxygen ratios and graphitic nature of a rangeof black carbon standard reference materials (BC SRMs), high molecularmass humic-like substances (HULIS) and atmospheric particles are examinedusing scanning transmission X-ray microscopy (STXM) coupled with nearedge X-ray absorption fine structure (NEXAFS) spectroscopy. UsingSTXM/NEXAFS, individual particles with diameter>100 nm are studied,thus the diversity of atmospheric particles collected during a variety offield missions is assessed. Applying a semi-quantitative peak fittingmethod to the NEXAFS spectra enables a comparison of BC SRMs and HULIS toparticles originating from anthropogenic combustion and biomass burns,thus allowing determination of the suitability of these materials forrepresenting atmospheric particles. Anthropogenic combustion and biomassburn particles can be distinguished from one another using both chemicalbonding and structural ordering information. While anthropogeniccombustion particles are characterized by a high proportion ofaromatic-C, the presence of benzoquinone and are highly structurallyordered, biomass burn particles exhibit lower structural ordering, asmaller proportion of aromatic-C and contain a much higher proportion ofoxygenated functional groups.

  16. White South Africans' Reactions to Black Advancement: A Two-Sample Confirmatory Investigation of the Structure of Attitude Using an Analogy to the Multitrait-Multimethod Design. (United States)

    Taylor, Terence R.; Chemel, Charles S.


    A questionnaire measuring affective, conative, and cognitive responses to 3 aspects of Black advancement in the workplace was administered to 128 White English-speaking and 140 Afrikaans-speaking South Africans. Results of confirmatory, single-group, and multigroup analyses of the data indicate that the structures were very similar across the…

  17. Proximity association in polygynous western black crested gibbons (Nomascus concolor jingdongensis): network structure and seasonality%Proximity association in polygynous western black crested gibbons (Nomascus concolor jingdongensis):network structure and seasonality

    Institute of Scientific and Technical Information of China (English)

    Zhen-Hua GUAN; Bei HUANG; Wen-He NING; Qing-Yong NI; Xue-Long JIANG


    We investigated the structure and seasonality of the proximity network in a group of polygynous western black crested gibbons (Nomascus concolor) using social network analysis.The spatial proximity changed seasonally and was affected by temperature and rainfall.Preferred proximity association was not distributed randomly among individuals.Kinship was one explanation for the social structure,as offspring preferred to maintain close proximity with their mothers.The proximity of infants to mothers decreased with age,and independent offspring had lower proximity to mothers than dependent ones.We found that the adult male had different proximity relationships with two different adult females.The frequency of proximity between the male and the infant-carrying female was significantly higher than that between the male and the female who had immigrated carrying one offspring of uncertain paternity into the group.Infanticide avoidance and/or predation protection for dependent infants might explain the proximity relationship differences.Temperature influenced group proximity association,with individual proximity increasing in the cold months and decreasing in the hot months.Group proximity decreased in months with higher anthropogenic disturbance.

  18. Results of the Joint Project (NASU-TUBITAK) "The Thermal Structure of the Crust in the Black Sea Analysis of Magnetic and Heat Flow Data" (United States)

    Starostenko, Vitaly; Dolmaz, M. Nuri; Kutas, Roman; Rusakov, Oleg; Oksum, Erdinc; Tutunsatar, H. Evrim; Hisarli, Z. Mumtaz; Okyar, Mahmut; Kalyoncuoglu, U. Yalcin; Legostaeva, Olga


    . Keywords: Black Sea, Curie Point Depth, Heat Flow, Thermal Structure

  19. 3-cm Fine Structure Masers: A Unique Signature of Supermassive Black Hole Formation via Direct Collapse in the Early Universe (United States)

    Dijkstra, Mark; Sethi, Shiv; Loeb, Abraham


    The direct collapse black hole (DCBH) scenario describes the isothermal collapse of a pristine gas cloud directly into a massive, {M}{BH} = 104-106{M}⊙ black hole. In this paper we show that large H i column densities of primordial gas at T˜ {10}4 K with low molecular abundance—which represent key aspects of the DCBH scenario—provide optimal conditions for the pumping of the 2p-level of atomic hydrogen by trapped Lyα photons. This Lyα pumping mechanism gives rise to an inverted level population of the 2{s}1/2-2{p}3/2 transition, and therefore also gives rise to stimulated fine structure emission at λ =3.04 {cm} (rest-frame). We show that simplified models of the DCBH scenario amplify the CMB by up to a factor of ˜ {10}5, above which the maser saturates. Hyperfine splitting of the 3 cm transition gives rise to a characteristic broad (FWHM ˜ tens of MHz in the observers frame) asymmetric line profile. This signal subtends an angular scale of ˜1-10 mas, which translates to a flux of ˜0.3-3 μJy, which is detectable with ultra-deep surveys being planned with SKA1-MID. While challenging, as the signal is visible for a fraction of the collapse time of the cloud, the matching required physical conditions imply that a detection of the redshifted 3-cm emission line could provide direct evidence for the DCBH scenario.


    Institute of Scientific and Technical Information of China (English)

    Jian-hua Cao; Yang-zheng Lin; Ji-ding Li; Cui-xian Chen


    This study deals with polydimethylsiloxane(PDMS)/polyvinylidene fluoride(PVDF)composite membranes for propane separation from propane/nitrogen mixtures,which is relevant to the recovery of propane in petroleum and chemical industry.The surface and cross-section morphology of PDMS/PVDF composite membranes was observed by scanning electron microscope(SEM).The surface morphology of PDMS/PVDF composite membranes is very dense.There are three layers,the thin dense top layer,finger-like porous middle layer and sponge-like under layer in the cross-section SEM image of PDMS/PVDF composite membranes.The effects of the types of cross-linking agents and pressure on the membrane permselectivity were investigated.The permeability of nitrogen was independent of feed pressure.However,the permeability of propane increased with the pressure increasing for all membranes.The membrane cured by a tri-functional crosslinker with attached vinyl groups had better performance than the tetra-functional one,in both selectivity and permeation flux.The total permeation flux is 1.769 × 10-2 cm3(STP)/(cm2·s)and the separation factor is 19.17 when the mole percent of propane in the gas mixture is 10 at the 0.2 MPa pressure difference and 25°C.

  1. Dipolar cross-linkers for PDMS networks with enhanced dielectric permittivity and low dielectric loss

    DEFF Research Database (Denmark)

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


    Dipole grafted cross-linkers were utilized to prepare polydimethylsiloxane (PDMS) elastomers with various chain lengths and with various concentrations of functional cross-linker. The grafted cross-linkers were prepared by reaction of two alkyne-functional dipoles, 1-ethynyl-4-nitrobenzene and 3...

  2. LEO resistant PI-B-PDMS block copolymer films for solar array applications

    NARCIS (Netherlands)

    Lonkhuyzen, H. van; Bongers, E.; Fischer, H.R.; Dingemans, T.J.; Semprimoschnig, C.


    Due to their low atomic oxygen erosion yields PI-b-PDMS block copolymer films have considerable potential for application onto space exposed surfaces of satellites in low earth orbit. On solar arrays these materials might be used as electrical electrical insulation film, flexprint outer layer, elect

  3. CNT/PDMS composite flexible dry electrodes for long-term ECG monitoring. (United States)

    Jung, Ha-Chul; Moon, Jin-Hee; Baek, Dong-Hyun; Lee, Jae-Hee; Choi, Yoon-Young; Hong, Joung-Sook; Lee, Sang-Hoon


    We fabricated a carbon nanotube (CNT)/ polydimethylsiloxane (PDMS) composite-based dry ECG electrode that can be readily connected to conventional ECG devices, and showed its long-term wearable monitoring capability and robustness to motion and sweat. While the dispersion of CNTs in PDMS is challenging, we optimized the process to disperse untreated CNTs within PDMS by mechanical force only. The electrical and mechanical characteristics of the CNT/PDMS electrode were tested according to the concentration of CNTs and its thickness. The performances of ECG electrodes were evaluated by using 36 types of electrodes which were fabricated with different concentrations of CNTs, and with a differing diameter and thickness. The ECG signals were obtained by using electrodes of diverse sizes to observe the effects of motion and sweat, and the proposed electrode was shown to be robust to both factors. The CNT concentration and diameter of the electrodes were critical parameters in obtaining high-quality ECG signals. The electrode was shown to be biocompatible from the cytotoxicity test. A seven-day continuous wearability test showed that the quality of the ECG signal did not degrade over time, and skin reactions such as itching or erythema were not observed. This electrode could be used for the long-term measurement of other electrical biosignals for ubiquitous health monitoring including EMG, EEG, and ERG.

  4. Interaction between two solid surfaces across PDMS : influence of chain length and end group

    NARCIS (Netherlands)

    Sun, G.X.; Stark, R.; Kappl, M.; Leermakers, F.A.M.; Butt, H.J.


    Forces between solid surfaces across polymer melts are poorly understood despite their importance for adhesion and composite materials. Using an atomic force microscope (AFM) this force was measured for poly(dimethyl siloxane) (PDMS) on silicon oxide. The influence of molecular weight (4.0-40 kDa) w

  5. [Toluene, Benzene and Acetone Adsorption by Activated Carbon Coated with PDMS]. (United States)

    Liu, Han-bing; Jiang, Xin; Wang, Xin; Yang, Bing; Xue, Nan-dong; Zhang, Shi-lei


    To improve the adsorption selectivity of volatile organic compounds ( VOCs) , activated carbon ( AC) was modified by polydimethylsiloxane (PDMS) and characterized by BET analysis and Boehm titration. Dynamic adsorption column experiments were conducted and Yoon-Neslon(Y-N) model was used to identify adsorption effect for toluene, beuzene and acetone on AC when relative humidity was 0%, 50% and 90%, respectively. The results showed that the BET area, micropore volume and surface functional groups decreased with the PDMS modification, and surface hydrophobicity of the modified AC was enhanced leading to a lower water adsorption capacity. The results of dynamic adsorption showed that the adsorption kinetics and capacity of Bare-AC decreased with the increase of relative humidity, and the adsorption capacities of PDMS coated AC were 1.86 times (toluene) and 1.92 times (benzene) higher than those of Bare-AC, while a significant improvement of adsorption capacity for acetone was not observed. These findings suggest that polarity of molecule can be an important influencing factor for adsorption on hydrophobic surface developed by PDMS.

  6. Highly stable hydrophilic surfaces of PDMS thin layer obtained by UV radiation and oxygen plasma treatments

    Energy Technology Data Exchange (ETDEWEB)

    Menezes Atayde, Cleuson de; Doi, Ioshiaki [Center for Semiconductor Components, University of Campinas - UNICAMP, Campinas, SP (Brazil); School of Electrical and Computer Engineering, University of Campinas - UNICAMP, Campinas, SP (Brazil)


    Surface modification of polydimethylsiloxane (PDMS, Sylgard 184) was carried out by O{sub 2} plasma and UV in broadband mode/O{sub 2} plasma treatments with different exposure times, and studied in terms of hydrophilic stability. Water contact angle measurements, Fourier Transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) were used for the analysis of the modified surface and hydrophilic stability of the PDMS films. The results show reasonably good hydrophilic stability in the range of a week with a contact angle of around 70 for O{sub 2} plasma treated samples, whereas a more high hydrophilic stability, with a low contact angle of 65 up to 15 days, was observed for UV/O{sub 2} plasma treated PDMS. FTIR analysis of the samples reveals significant oxidation noted by large presence of Si-O-Si, and Si-OH bonds on the PDMS surface, which improves the affinity with water molecules and increases the hydrophilicy. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Optical absorption in transparent PDMS materials applied for multimode waveguides fabrication (United States)

    Cai, D. K.; Neyer, A.; Kuckuk, R.; Heise, H. M.


    The optical properties of transparent PDMS polymer materials, which can be integrated into general printed circuit board (PCB) for data communication, are of great interest due to the substantial market expectations for the near future. For the present paper, it was found that the absorption loss in polydimethylsiloxane (PDMS) is mainly caused by the vibrational overtone and combination bands of the CH 3-groups of the polymer in the spectral datacom region of 600-900 nm. Based on observed positions of fundamental, overtone and combination bands of the methyl-group, as recorded within the mid- and near-infrared spectra, anharmonicity constants and normal vibration frequencies were determined. Thus, an empirical equation for estimating the wavelengths with the most significant intrinsic absorption loss due to the corresponding band positions was formulated, which was found to agree well with the experimental data. In addition, PDMS multimode waveguides were fabricated and the respective optical insertion loss was measured at 850 nm, which is commercially used for optical datacom transmission and finally the thermal stability of PDMS multimode waveguides was verified as well.

  8. Stretchable conducting gold films prepared with composite MWNT/PDMS substrates (United States)

    Manzoor, M. U.; Lemoine, P.; Dixon, D.; Hamilton, J. W. J.; Maguire, P. D.


    Novel stretchable conducting films were prepared by depositing gold layers onto polymer nano-composites substrates formed by in-situ crosslinking of polydimethylsiloxane (PDMS) in the presence of multiwall carbon nanotubes (MWNT). The MWNT content interferes with the PDMS cure reaction giving variations in thermal degradation, solvent swelling, mechanical and electrical properties. Tensile cycling experiments were carried out on the gold-coated PDMS and nano-composite substrates SEM analysis and electrical measurements demonstrated that the crack widening and increased electrical resistance observed during strain cycling were reversible. The inclusion of 8 % MWNT into PDMS brought more micro-cracking in the gold layer yet reduced the electrical resistance of the gold-coated samples by 172X at 5 % strain, 38X at 10 % strain and 19X at 20 %. Hence, this improvement in conduction is attributed to assisted-conduction through the MWNT loaded substrate. This mechanism results in a more stable and reproducible electrical behaviour, making electrical conduction less critically dependent on defects in the gold layer.

  9. Irreversible bonding of polyimide and polydimethylsiloxane (PDMS) based on a thiol-epoxy click reaction (United States)

    Hoang, Michelle V.; Chung, Hyun-Joong; Elias, Anastasia L.


    Polyimide is one of the most popular substrate materials for the microfabrication of flexible electronics, while polydimethylsiloxane (PDMS) is the most widely used stretchable substrate/encapsulant material. These two polymers are essential in fabricating devices for microfluidics, bioelectronics, and the internet of things; bonding these materials together is a crucial challenge. In this work, we employ click chemistry at room temperature to irreversibly bond polyimide and PDMS through thiol-epoxy bonds using two different methods. In the first method, we functionalize the surfaces of the PDMS and polyimide substrates with mercaptosilanes and epoxysilanes, respectively, for the formation of a thiol-epoxy bond in the click reaction. In the second method, we functionalize one or both surfaces with mercaptosilane and introduce an epoxy adhesive layer between the two surfaces. When the surfaces are bonded using the epoxy adhesive without any surface functionalization, an extremely small peel strength (0.3 N mm-1 (method 2) are observed, and failure occurs by tearing of the PDMS layer. We envision that the novel processing route employing click chemistry can be utilized in various cases of stretchable and flexible device fabrication.

  10. [Effects of heavy machinery operation on the structural characters of cultivated soils in black soil region of Northeast China]. (United States)

    Wang, En-Heng; Chai, Ya-Fan; Chen, Xiang-Wei


    With the cultivated soils in black soil region of Northeast China as test objects, this paper measured their structural characters such as soil strength, bulk density, and non-capillary porosity/capillary porosity (NCP/CP) ratio before and after heavy and medium-sized machinery operation, aimed to study the effects of machinery operation on the physical properties of test soils. The results showed that after machinery operation, there existed three distinct layers from top to bottom in the soil profiles, i.e., plowed layer, cumulative compacted layer, and non-affected layer, according to the changes of soil strength. Under medium-sized machinery operation, these three layers were shallower, and there was a new plow pan at the depth between 17.5 and 30 cm. Heavy machinery operation had significant positive effects on the improvement of topsoil structure (P machinery, the bulk density of topsoil decreased by 7.2% and 3.5%, respectively, and NCP/CP increased by 556.6% after subsoiling, which would benefit water infiltration, reinforce water storage, and weaken the threat of soil erosion. The main action of heavy machinery operation was soil loosening, while that of medium-sized machinery operation was soil compacting.

  11. Synthesis and Characterization Multi-Block Copolymer PGMA-PBMA-PDMS-PBMA-PGMA by ATRP%多嵌段共聚物PGMA-PBMA-PDMS-PBMA-PGMA的ATRP合成与表征

    Institute of Scientific and Technical Information of China (English)

    周元林; 潘昱; 李迎军; 何方方; 张严金; 罗世凯; 雷卫华


    采用聚二甲基硅氧烷大分子(Bf—PDMS-Br)为引发剂,CuCl为催化剂,2,2’-联吡啶(bpy)为配体,甲基丙烯酸丁酯(BMA)和甲基丙烯酸缩水甘油酯(GMA)为单体,通过原子转移自由基聚合(ATRP)法,合成含有反应性环氧基的多嵌段共聚物PGMA-PBMA-PDMS-PBMA—PGMA。利用凝胶渗透色谱(GPC)、红外光谱(IR)、核磁共振(0H—NMR)、原子力显微镜(AFM)和热重分析(TG)方法对其分子量、分子结构、相形态及热稳定性进行研究。研究表明,多嵌段共聚物分子量可控,多分散性低(PDI=1.14~1.40);在微观相上形成有序纳米结构,粒径大小100nm~2μm;多嵌段聚合物低分解温度为270℃。高分解温度为480℃,具有良好的热稳定性;由于引入反应性基团环氧基,大大扩大了其应用范围。%In this paper, multi-block copolymer PGMA-PBMA-PDMS-PBMA-PGMA containing reactivity epoxy group was prepared by atom transfer radical polymerization (ATRP) method. The copolymer is synthesized by using polydimethylsiloxane molecules (Br-PDMS-Br) ended with functional groups as an initiator, cuprous chloride (CuC1) as a catalyst, 2,2'- bipyridine (bpy) as a ligand, rnethacrylate butyl ester (BMA) and glycidyl methacrylate (GMA) as monomers. Its molecular weight, molecular structure, morphology and thermal stability were identified by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), (hydrogen) nuclear magnetic resonance (1H-NMR), atomic force microscopy (AFM) and thermal gravimetric analysis (TG). The results show that molecular weight of the multi-block copolymer can be well controlled, polydispersity of the polymer is as low as 1.14 to 1.40. Microphase ordered nanostrueture is formed of which the particle size is 100 nm--2μm. Compatibility of the components and thermal stability of the multipolymer are great. Low decomposition temperature is 270

  12. Low-temperature solid-state microwave reduction of graphene oxide for transparent electrically conductive coatings on flexible polydimethylsiloxane (PDMS). (United States)

    Liang, Qizhen; Hsie, Sinsar Alec; Wong, Ching Ping


    Microwaves (MWs) are applied to initialize deoxygenation of graphene oxide (GO) in the solid state and at low temperatures (∼165 °C). The Fourier-transform infrared (FTIR) spectra of MW-reduced graphene oxide (rGO) show a significantly reduced concentration of oxygen-containing functional groups, such as carboxyl, hydroxyl and carbonyl. X-ray photoelectron spectra confirm that microwaves can promote deoxygenation of GO at relatively low temperatures. Raman spectra and TGA measurements indicate that the defect level of GO significantly decreases during the isothermal solid-state MW-reduction process at low temperatures, corresponding to an efficient recovery of the fine graphene lattice structure. Based on both deoxygenation and defect-level reduction, the resurgence of interconnected graphene-like domains contributes to a low sheet resistance (∼7.9×10(4) Ω per square) of the MW-reduced GO on SiO(2) -coated Si substrates with an optical transparency of 92.7 % at ∼547 nm after MW reduction, indicating the ultrahigh efficiency of MW in GO reduction. Moreover, the low-temperature solid-state MW reduction is also applied in preparing flexible transparent conductive coatings on polydimethylsiloxane (PDMS) substrates. UV/Vis measurements indicate that the transparency of the thus-prepared MW-reduced GO coatings on PDMS substrates ranges from 34 to 96 %. Correspondingly, the sheet resistance of the coating ranges from 10(5) to 10(9) Ω per square, indicating that MW reduction of GO is promising for the convenient low-temperature preparation of transparent conductors on flexible polymeric substrates.

  13. Black Droplets

    CERN Document Server

    Santos, Jorge E


    Black droplets and black funnels are gravitational duals to states of a large N, strongly coupled CFT on a fixed black hole background. We numerically construct black droplets corresponding to a CFT on a Schwarzchild background with finite asymptotic temperature. We find two branches of such droplet solutions which meet at a turning point. Our results suggest that the equilibrium black droplet solution does not exist, which would imply that the Hartle-Hawking state in this system is dual to the black funnel constructed in \\cite{Santos:2012he}. We also compute the holographic stress energy tensor and match its asymptotic behaviour to perturbation theory.

  14. Cancer Research Participation Beliefs and Behaviors of a Southern Black Population: A Quantitative Analysis of the Role of Structural Factors in Cancer Research Participation. (United States)

    Farr, Deeonna E; Brandt, Heather M; Comer, Kimberly D; Jackson, Dawnyéa D; Pandya, Kinjal; Friedman, Daniela B; Ureda, John R; Williams, Deloris G; Scott, Dolores B; Green, Wanda; Hébert, James R


    Increasing the participation of Blacks in cancer research is a vital component of a strategy to reduce racial inequities in cancer burden. Community-based participatory research (CBPR) is especially well-suited to advancing our knowledge of factors that influence research participation to ultimately address cancer-related health inequities. A paucity of literature focuses on the role of structural factors limiting participation in cancer research. As part of a larger CBPR project, we used survey data from a statewide cancer needs assessment of a Black faith community to examine the influence of structural factors on attitudes toward research and the contributions of both structural and attitudinal factors on whether individuals participate in research. Regression analyses and non-parametric statistics were conducted on data from 727 adult survey respondents. Structural factors, such as having health insurance coverage, experiencing discrimination during health care encounters, and locale, predicted belief in the benefits, but not the risks, of research participation. Positive attitudes toward research predicted intention to participate in cancer research. Significant differences in structural and attitudinal factors were found between cancer research participants and non-participants; however, directionality is confounded by the cross-sectional survey design and causality cannot be determined. This study points to complex interplay of structural and attitudinal factors on research participation as well as need for additional quantitative examinations of the various types of factors that influence research participation in Black communities.

  15. PCL-PDMS-PCL copolymer-based microspheres mediate cardiovascular differentiation from embryonic stem cells (United States)

    Song, Liqing

    Poly-epsilon-caprolactone (PCL) based copolymers have received much attention as drug or growth factor delivery carriers and tissue engineering scaffolds due to their biocompatibility, biodegradability, and tunable biophysical properties. Copolymers of PCL and polydimethylsiloxane (PDMS) also have shape memory behaviors and can be made into thermoresponsive shape memory polymers for various biomedical applications such as smart sutures and vascular stents. However, the influence of biophysical properties of PCL-PDMS-PCL copolymers on stem cell lineage commitment is not well understood. In this study, PDMS was used as soft segments of varying length to tailor the biophysical properties of PCL-based co-polymers. While low elastic modulus (embryonic stem cells, the range of 60-100 MPa PCL-PDMS-PCL showed little influence on the differentiation. Then different size (30-140 mum) of microspheres were fabricated from PCL-PDMS-PCL copolymers and incorporated within embryoid bodies (EBs). Mesoderm differentiation was induced using bone morphogenetic protein (BMP)-4 for cardiovascular differentiation. Differential expressions of mesoderm progenitor marker KDR and vascular markers CD31 and VE-cadherin were observed for the cells differentiated from EBs incorporated with microspheres of different size, while little difference was observed for cardiac marker alpha-actinin expression. Small size of microspheres (30 mum) resulted in higher expression of KDR while medium size of microspheres (94 mum) resulted in higher CD31 and VE-cadherin expression. This study indicated that the biophysical properties of PCL-based copolymers impacted stem cell lineage commitment, which should be considered for drug delivery and tissue engineering applications.

  16. Learning Structure Illuminates Black Boxes: an Introduction into Estimation of Distribution Algorithms

    NARCIS (Netherlands)

    Grahl, J.; Minner, S.; Bosman, P.A.N.; Michalewicz, Z.; Siarry, P.


    This chapter serves as an introduction to estimation of distribution algorithms (EDAs). Estimation of distribution algorithms are a new paradigm in evolutionary computation. They combine statistical learning with population-based search in order to automatically identify and exploit certain structur

  17. Effects of carbon blacks with various structures on vulcanization and reinforcement of filled ethylene-propylene-diene rubber

    Directory of Open Access Journals (Sweden)


    Full Text Available The effects of carbon blacks on vulcanization and mechanical properties of filled ethylene-propylene-diene rubber (EPDM are investigated, by comparing with five types of rubber-grade carbon blacks. Curing kinetics is studied by rheometer and the results indicate that the curing characteristics are influenced by combination of surface area of carbon black and sulphur content on the filler surface, because the former one enhances the physical cross-linking and the latter one introduces the additional chemical cross-linking. Both the degree of cross-linking and cure rate increase with increasing surface area and sulphur content, whereas the optimum cure time and scorch time decrease. The reinforcing nature of the carbon black is assessed from mechanical measurements. It is suggested that the surface area of carbon blacks strongly affects the physical properties of EPDM/carbon black composites. Conductive carbon black (N472 can be used as desirable reinforcing filler due to the higher degree of cross-linking of EPDM with N472 than other EPDM/carbon black composites. The morphology and distribution of particles are studied by using scanning electron microscope. The sound reinforcing ability of N472 is also supported by scanning electron microscope due to the notable dispersibility of N472 within EPDM matrix. N472 ensures the EPDM/N472 composite the most conductive sample among the five composites.

  18. Black psyllium (United States)

    Black psyllium is a weed that grows aggressively throughout the world. The plant was spread with the ... to make medicine. Be careful not to confuse black psyllium with other forms of psyllium including blond ...

  19. Experimental study of PDMS mechanical properties for the optimization of polymer based flexible pressure micro-sensors (United States)

    Dinh, T. H. N.; Martincic, E.; Dufour-Gergam, E.; Joubert, P.-Y.


    This paper reports on the optimization of flexible PDMS-based normal pressure capacitive micro-sensors dedicated to wearable applications. The deformation under a normal force of PDMS thin films of thicknesses ranging from 40 μm to 10 mm is firstly experimentally studied. This study points out that for capacitive micro-sensors using bulky PDMS thin films as deformable dielectric material, the sensitivity to an applied normal load can be optimized thanks to an adequate choice of the so-called form ratio of the involved PDMS thin film. Indeed, for capacitive micro-sensors exhibiting 9 mm2 electrodes, the capacitance change under a 6 N load can be adjusted from a few percent up to over 35% according to the choice of the load-free thickness of the used PDMS film. These results have been validated thanks to electromechanical characterizations carried out on two flexible PDMS based capacitive normal pressure micro-sensor samples fabricated with two different thicknesses. The obtained results open the way to the enhanced design of PDMS based pressure sensors dedicated to wearable and medical applications. Further works will extend this study to a wider range of sensor dimensions, and using numerical modelling.

  20. Underground riparian wood: Buried stem and coarse root structures of Black Poplar (Populus nigra L.) (United States)

    Holloway, James V.; Rillig, Matthias C.; Gurnell, Angela M.


    Despite the potential importance of tree species in influencing the processes of wood recruitment, transport, retention, and decay that control river wood budgets, focus has been relatively limited on this theme within fluvial wood research. Furthermore, one of the least investigated topics is the belowground living wood component of riparian trees. This paper presents observations of the morphology and age of buried stem and coarse root structures of eight Populus nigra individuals located in the riparian woodland of two sites on the middle to lower Tagliamento River, Italy. This species was selected because of its wide distribution along European rivers and its frequent dominance of riparian woodland. Each tree was excavated by hand to expose a minimum of half of the root system with complete exposure of the main axis. Smaller roots were then removed and larger protruding roots cut back to permit access to the main axis. The excavated structures were photographed from multiple angles for photogrammetric modelling; the structure and character of the exposed sediments around the tree's main axis were recorded; and wood samples were taken from the main aboveground stem(s), sections of the main buried axis, and major roots for dendrochronological analysis. Results from these field observations and laboratory dating of the wood samples were combined to describe the belowground morphology of each tree and to draw inferences concerning the impact of fluvial disturbances. Common features of these excavated structures included: (i) rooting depths to below the bar surface where the original tree established, with many young roots also existing at depth; (ii) translocation of the main buried axis in a downstream direction; (iii) a main buried axis comprised mainly of stems that have become buried and then generated new shoots, including multistem patches, and adventitious roots; (iv) the presence of steps and bends in the main buried axis associated with the generation of


    Directory of Open Access Journals (Sweden)

    Johana Rodríguez


    Full Text Available En este estudio se determinaron las propiedadesinterfaciales en solución acuosadel surfactante del tipo PDMS-éster quecontiene polidimetilsiloxano (PDMS,polietilenglicol (PEG, anhídrido maléicoy ácido fumárico. Para el estudio delas propiedades interfaciales se emplearonlas técnicas tensiometría y espectroscopiaen la región del UV-Vis. En soluciónacuosa este surfactante mostró uncomportamiento complejo, que es dependientede la concentración. En este surfactantese observó un cambio brusco enla curva de tensión superficial en funciónde la concentración, produciendo una reducciónde la tensión superficial del aguahasta 48,9 mN/m en la CMC. La concentracióndel surfactante en la CMC fue de1032 mg/L. La eficiencia del surfactantePDMS-éster se calculó como pC20 y sedeterminó como la concentración del surfactantenecesaria para conseguir una disminuciónde la tensión superficial de 20mN/m. El valor de C20 obtenido fue 213mg/L (1,554x10-5 mol/L (pC20=4,81.Esta concentración sirve como un indicadorde la eficiencia de la adsorcióndel surfactante, ya que la reducción de latensión superficial de la solución por elsurfactante depende de la substitución demoléculas en la interface solución/vapor.

  2. Global Structure of Three Distinct Accretion Flows and Outflows around Black Holes through Two-Dimensional Radiation-Magnetohydrodynamic Simulations

    CERN Document Server

    Ohsuga, Ken


    We present the detailed global structure of black hole accretion flows and outflows through newly performed two-dimensional radiation-magnetohydrodynamic simulations. By starting from a torus threaded with weak toroidal magnetic fields and by controlling the central density of the initial torus, rho_0, we can reproduce three distinct modes of accretion flow. In model A with the highest central density, an optically and geometrically thick supercritical accretion disk is created. The radiation force greatly exceeds the gravity above the disk surface, thereby driving a strong outflow (or jet). Because of the mild beaming, the apparent (isotropic) photon luminosity is ~22L_E (where L_E is the Eddington luminosity) in the face-on view. Even higher apparent luminosity is feasible if we increase the flow density. In model B with a moderate density, radiative cooling of the accretion flow is so efficient that a standard-type, cold, and geometrically thin disk is formed at radii greater than ~7R_S (where R_S is the S...

  3. Changes in oviduct structure in the black tiger shrimp,Penaeus monodon, during ovarian maturation

    Institute of Scientific and Technical Information of China (English)



    Objective:To examine the structure of the oviduct of the shrimp Penaeus monodon.Methods:The oviducts of P.monodon with three different major groups of ovarian development (Group (Gr.) 1:Stages Ⅰ & Ⅴ; Gr.2:Stages Ⅱ & Ⅲ; and Gr.3:Stage Ⅳ)were examined by light,transmission electron,and scanning electron microscopies,respectively.Results:The epithelium of the oviduct in Gr.1 was composed of tall simple columnar cells with their basal nuclei located on the basement membrane and its thick collagen fibers.In Gr.2,the oviduct seemed to produce some substances and their epithelial cells became transitional with centrally located nuclei and formed some vacuoles.Obviously,the epithelial cells in Gr.3 (at Stage Ⅳ) were disorganized,disrupted,and shed accumulated spherical secretory substances including some cellular contents into the lumen.Conclusions:The structural changes of the P.monodon oviduct were related to ovarian maturation stages (Grs.1-3).Prior to spawning,only the oviduct epithelium at ovary Stage Ⅳ produced and secreted a number of spherical secretion substances into the lumen.These substances may act as the oviductal lubricants to facilitate the spawning process.

  4. Black Holes (United States)

    Luminet, Jean-Pierre


    Foreword to the French edition; Foreword to the English edition; Acknowledgements; Part I. Gravitation and Light: 1. First fruits; 2. Relativity; 3. Curved space-time; Part II. Exquisite Corpses: 4. Chronicle of the twilight years; 5. Ashes and diamonds; 6. Supernovae; 7. Pulsars; 8. Gravitation triumphant; Part III. Light Assassinated: 9. The far horizon; 10. Illuminations; 11. A descent into the maelstrom; 12. Map games; 13. The black hole machine; 14. The quantum black hole; Part IV. Light Regained: 15. Primordial black holes; 16. The zoo of X-ray stars; 17. Giant black holes; 18. Gravitational light; 19. The black hole Universe; Appendices; Bibliography; Name index; Subject index.

  5. Femtosecond laser surface structuring and oxidation of chromium thin coatings: Black chromium

    Energy Technology Data Exchange (ETDEWEB)

    Kotsedi, L., E-mail: [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Nuru, Z.Y. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Mthunzi, P. [National Laser Centre, Council for Scientific and Industrial Research, 0001 Pretoria (South Africa); Muller, T.F.G. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Eaton, S.M. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Julies, B. [University of the Western Cape, Physics Department, Bellville, 7535 Cape Town (South Africa); Manikandan, E. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa); Ramponi, R. [Physics Department, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano (Italy); Maaza, M. [UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, Muckleneuk Ridge, P.O. Box 392, Pretoria (South Africa); Nanosciences African Network (NANOAFNET), iThemba LABS-National Research Foundation, 1 Old Faure Road, Somerset West 7129, P.O. Box 722, Somerset West, Western Cape (South Africa)


    Highlights: • Oxidation of the chromium thin film to chromium oxide by femtosecond laser with a fundamental wavelength of 1064 nm. • Solar absorber from chromium oxide that low percentage reflectance. • Femtosecond laser oxidation, with a de-focused laser. • Chromium oxide formation by femtosecond laser in normal ambient. - Abstract: In view of their potential applications as selective solar absorbers, chromium coatings on float glass substrates were nano/micro structured by femtosecond laser in air. Raman and X-rays diffraction investigations confirmed the formation of an ultra-porous α-Cr{sub 2}O{sub 3} layer at the surface; higher is the input laser power, enhanced is the crystallinity of the α-Cr{sub 2}O{sub 3} layer. The α-Cr{sub 2}O{sub 3} layer with the Cr underneath it in addition to the photo-induced porosity acted as a classical ceramic–metal nano-composite making the reflectance to decrease significantly within the spectral range of 190–1100 nm. The average reflectance decreased from 70 to 2%.

  6. Validation of an SPME method, using PDMS, PA, PDMS-DVB, and CW-DVB SPME fiber coatings, for analysis of organophosphorus insecticides in natural waters. (United States)

    Lambropoulou, D A; Sakkas, V A; Albanis, T A


    Solid-phase microextraction (SPME) has been optimized and applied to the determination of the organophosphorus insecticides diazinon, dichlofenthion, parathion methyl, malathion, fenitrothion, fenthion, parathion ethyl, bromophos methyl, bromophos ethyl, and ethion in natural waters. Four types of SPME fiber coated with different stationary phases (PDMS, PA, PDMS-DVB, and CW-DVB) were used to examine their extraction efficiencies for the compounds tested. Conditions that might affect the SPME procedure, such as extraction time and salt content, were investigated to determine the analytical performance of these fiber coatings for organophosphorus insecticides. The optimized procedure was applied to natural waters - tap, sea, river, and lake water - spiked in the concentration range 0.5 to 50 micro g L(-1) to obtain the analytical characteristics. Recoveries were relatively high - >80% for all types of aqueous sample matrix - and the calibration plots were reproducible and linear (R(2)>0.982) for all analytes with all the fibers tested. The limits of detection ranged from 2 to 90 ng L(-1), depending on the detector and the compound investigated, with relative standard deviations in the range 3-15% at all the concentration levels tested. The SPME partition coefficients (K(f)) of the organophosphorus insecticides were calculated experimentally for all the polymer coatings. The effect of organic matter such as humic acids on extraction efficiency was also studied. The analytical performance of the SPME procedure using all the fibers in the tested natural waters proved effective for the compounds.

  7. Transfer Function of Macro-Micro Manipulation on a PDMS Microfluidic Chip

    Directory of Open Access Journals (Sweden)

    Koji Mizoue


    Full Text Available To achieve fast and accurate cell manipulation in a microfluidic channel, it is essential to know the true nature of its input-output relationship. This paper aims to reveal the transfer function of such a micro manipulation controlled by a macro actuator. Both a theoretical model and experimental results for the manipulation are presented. A second-order transfer function is derived based on the proposed model, where the polydimethylsiloxane (PDMS deformation plays an important role in the manipulation. Experiments are conducted with input frequencies up to 300 Hz. An interesting observation from the experimental results is that the frequency responses of the transfer function behave just like a first-order integration operator in the system. The role of PDMS deformation for the transfer function is discussed based on the experimentally-determined parameters and the proposed model.

  8. Mechanically driven luminescence in a ZnS:Cu-PDMS composite

    Directory of Open Access Journals (Sweden)

    Kee-Sun Sohn


    Full Text Available The conventional mechanoluminescence (ML mechanism of phosphors such as SrAl2O4:Eu and ZnS:Mn is known to utilize carrier trapping at shallow traps followed by stress (or strain-induced detrapping, which leads to activator recombination in association with local piezoelectric fields. However, such a conventional ML mechanism was found to be invalid for the ZnS:Cu-embedded polydimethylsiloxane (PDMS composite, due to the absence of luminescence with a rigid matrix and a negligibly small value of the piezoelectric coefficient (d33 of the composite. An alternative mechanism, namely, the triboelectricity-induced luminescence has been proposed for the mechanically driven luminescence of a ZnS:Cu-PDMS composite.

  9. Rapid, Brushless Self-assembly of a PS-b-PDMS Block Copolymer for Nanolithography

    DEFF Research Database (Denmark)

    Rasappa, Sozaraj; Schulte, Lars; Borah, Dipu


    by grafting of a brush layer that renders the surface energy neutral relative to the constituent blocks. We provide here a first study on rapid, low temperature self-assembly of PS-b-PDMS (polystyrene-block-polydimethylsiloxane) on silicon substrates without a brush layer. We show that it forms line...... and antidot patterns after short solvo-thermal annealing. Unlike previous reports on this system, low temperature and short annealing time provide self-assembly in homogeneous thin films covering large substrate areas. This on-chip mask was then used for pattern transfer to the underlying silicon substrate....... SEM (scanning electron microscope) images reveal silicon nanowires relative to the PDMS patterns of the BCP mask....

  10. Deformation Analysis of a Pneumatically-Activated Polydimethylsiloxane (PDMS Membrane and Potential Micro-Pump Applications

    Directory of Open Access Journals (Sweden)

    Chi-Han Chiou


    Full Text Available This study presents a double-side diaphragm peristaltic pump for efficient medium transport without the unwanted backflow and the lagging effect of a diaphragm. A theoretical model was derived to predict the important parameter of the micropump, i.e., the motion of the valves at large deformations, for a variety of air pressures. Accordingly, we proposed an easy and robust design to fabricate a Polydimethylsiloxane (PDMS-based micropump. The theoretical model agrees with a numerical model and experimental data for the deformations of the PDMS membrane. Furthermore, variations of the generated flow rate, including pneumatic frequencies, actuated air pressures, and operation modes were evaluated experimentally for the proposed micropumps. In future, the theoretical equation could provide the optimal parameters for the scientists working on the fabrication of the diaphragm peristaltic pump for applications of cell-culture.

  11. A soft and conductive PDMS-PEG block copolymer as a compliant electrode for dielectric elastomers

    DEFF Research Database (Denmark)

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

    -methyl pyrrolidinone) with 1 wt% of surfactant (Triton X-100). The dispersion of MWCNTs in PDMS-PEG systemis shown in figure 2 where MWCNTs (dark areas) are well-distributed in the system indicating an acceptable dispersional though some big clusters appear in the optical microscope image. The conductivity of 4 phr...... MWCNTs is 10-3 S/cm compared to 10-1 S/cm of a non-stretchable reference conducting silicone elastomer (LR3162 from Wacker). Furthermore, PDMS-PEG block copolymer with 4 phr MWCNTs (Young’s modulus, Y = 0.26 MPa) is softer and more stretchable thanLR3162 (Y = 1.17 MPa)....

  12. Facile fabrication of functional PDMS surfaces with tunable wettablity and high adhesive force via femtosecond laser textured templating

    Directory of Open Access Journals (Sweden)

    Yanlei Hu


    Full Text Available Femtosecond laser processing is emerged as a promising tool to functionalize surfaces of various materials, including metals, semiconductors, and polymers. However, the productivity of this technique is limited by the low efficiency of laser raster scanning. Here we report a facile approach for efficiently producing large-area functional polymer surfaces, by which metal is firstly textured by a femtosecond laser, and the as-prepared hierarchical structures are subsequently transferred onto polydimethylsiloxane (PDMS surfaces. Aluminum pieces covered by laser induced micro/nano-structures act as template masters and their performance of displaying diverse colors are investigated. Polymer replicas are endowed with tunable wetting properties, which are mainly attributed to the multi-scale surface structures. Furthermore, the surfaces are found to have extremely high adhesive force for water drops because of the high water penetration depth and the resultant high contact angle hysteresis. This characteristic facilitates many potential applications like loss-free tiny water droplets transportation. The reusability of metal master and easiness of soft lithography make it to be a very simple, fast and cost-efficient way for mass production of functional polymeric surfaces.

  13. Synthesis and characterization of poly(phthalazinone ether nitrile)(PPEN)-polydimethylsiloxane (PDMS)block copolymers

    Institute of Scientific and Technical Information of China (English)

    Li Ming Dong; Gong Xiong Liao; Ming Jing Wang; Xi Gao Jian


    Block copolymers with different backbone compositions have been prepared by the condensation of dimethylamino terminated poly(dimethylsiloxane)(PDMS)and hydroquinone terminated poly(phthalazinone ether nitrile)(PPEN)in the presence of chlorobenzene/N-methyl pyrrolidone (NMP)as solvents.The products were characterized by FTIR,1H NMR and gel permeation chromatography.Differential scanning calorimetry analysis indicated that the block copolymers showed separated microphase.

  14. Homophobia, hypermasculinity and the US black church. (United States)

    Ward, Elijah G


    Black churches in the USA constitute a significant source of the homophobia that pervades black communities. This theologically-driven homophobia is reinforced by the anti-homosexual rhetoric of black nationalism. Drawing on a variety of sources, this paper discusses the sources of homophobia within black communities, and its impact upon self-esteem, social relationships and physical health. Religion-based homophobia and black nationalism point to wider structures which have influenced their emergence, including racism, patriarchy and capitalism. It is vital for US black churches and communities to understand and transcend their longstanding resistance to openly addressing complex, painful issues of sexuality and embrace healthier definitions of black manhood.

  15. Functionalized PDMS with versatile and scalable surface roughness gradients for cell culture

    KAUST Repository

    Zhou, Bingpu


    This manuscript describes a simple and versatile approach to engineering surface roughness gradients via combination of microfluidics and photo-polymerization. Through UV-mediated polymerization, N-isopropylacrylamide with concentration gradients are successfully grafted onto PDMS surface, leading to diverse roughness degrees on the obtained PDMS substrate. Furthermore, the extent of surface roughness can be controllably regulated via tuning the flow rate ratio between the monomer solution and deionized water. Average roughness ranging from 8.050 nm to 151.68 nm has well been achieved in this work. Such PDMS samples are also demonstrated to be capable of working as supporting substrates for controlling cell adhesion or detachment. Due to the different degrees of surface roughness on a single substrate, our method provides an effective approach for designing advanced surafecs for cell culture. Finally, the thermosensitive property of N-isopropylacrylamide makes our sample furnish as another means for controlling the cell detachment from the substrates with correspondence to the surrounding temperature.

  16. Numerical study of acoustophoretic motion of particles in a PDMS microchannel driven by surface acoustic waves. (United States)

    Nama, Nitesh; Barnkob, Rune; Mao, Zhangming; Kähler, Christian J; Costanzo, Francesco; Huang, Tony Jun


    We present a numerical study of the acoustophoretic motion of particles suspended in a liquid-filled PDMS microchannel on a lithium niobate substrate acoustically driven by surface acoustic waves. We employ a perturbation approach where the flow variables are divided into first- and second-order fields. We use impedance boundary conditions to model the PDMS microchannel walls and we model the acoustic actuation by a displacement function from the literature based on a numerical study of piezoelectric actuation. Consistent with the type of actuation, the obtained first-order field is a horizontal standing wave that travels vertically from the actuated wall towards the upper PDMS wall. This is in contrast to what is observed in bulk acoustic wave devices. The first-order fields drive the acoustic streaming, as well as the time-averaged acoustic radiation force acting on suspended particles. We analyze the motion of suspended particles driven by the acoustic streaming drag and the radiation force. We examine a range of particle diameters to demonstrate the transition from streaming-drag-dominated acoustophoresis to radiation-force-dominated acoustophoresis. Finally, as an application of our numerical model, we demonstrate the capability to tune the position of the vertical pressure node along the channel width by tuning the phase difference between two incoming surface acoustic waves.

  17. Mechanically tunable sub-10 nm metal gap by stretching PDMS substrate (United States)

    Liu, Wenjie; Shen, Yang; Xiao, Guohui; She, Xiaoyi; Wang, Jianfang; Jin, Chongjun


    Manipulating light in sub-10 nm or subnanometer metal nanogaps is crucial to study the strong interaction between electromagnetic waves and matters. However, the fabrication of metallic nanogaps with precisely controlled size and high-throughput still remains a challenge. Here, we developed an approach to actively control the gap distance between adjacent metal nanoparticles from 140 nm to sub-10 nm or even 0 nm via mechanical stretching process. To demonstrate this method, we manufactured the gold disk arrays in a square lattice on the polydimethylsiloxane (PDMS) substrate through interference lithography and gold deposition, and sub-10 nm interparticle gap was achieved as exerting a strain of 100% to the PDMS substrate. Transmission spectra show a remarkable red shift of the dipole resonance with narrowing gap from 140 nm to sub-10 nm. Importantly, a universal scaling law between the gap distance in nanoscale and the stretching amount of PDMS substrate in macroscopic scale were demonstrated experimentally and theoretically. Our method can tune the gap distance continuously and reversibly, suggesting potential applications in surface-enhanced Raman scattering, single photon emitter and quantum tunneling of electric charge.

  18. Sensitivity-enhanced temperature sensor based on PDMS-coated long period fiber grating (United States)

    Wang, Qi; Du, Chao; Zhang, Jiaming; Lv, Riqing; Zhao, Yong


    A sensitivity-enhanced temperature sensor based on a poly-dimethylsiloxane (PDMS)-coated long period fiber grating (LPFG) has been proposed and experimentally investigated. By embedding the LPFG in a temperature-sensitive elastomeric polymer, the temperature sensitivity of the proposed sensor could be effectively improved by 4 times higher than those of the conventional bare LPFG sensors due to the high thermo-optic coefficient (TOC) of PDMS. It can be found that the temperature sensitivities of higher-order modes are higher than those of lower-order modes by analyzing transmission spectra characteristics of the sensor. Because of LPFG is sensitive to surrounding refractive index (RI), the PDMS-coated LPFG will have a high temperature sensitivities of 255.4 pm/°C in the range of 20-80 °C. Due to the high measurement resolution of 0.078 °C, the sensor is promising to be applied to the fields that high-precision temperature measurement is required.

  19. An enzyme derivatized polydimethylsiloxane (PDMS) membrane for use in membrane introduction mass spectrometry (MIMS). (United States)

    Creba, A Skye; Weissfloch, Alexandra N E; Krogh, Erik T; Gill, Chris G


    Membrane introduction mass spectrometry (MIMS) provides direct measurement of volatile and semivolatile analytes in condensed and gas-phase samples without sample preparation steps. Although MIMS has numerous advantages that include direct, on-line, real-time analysis with low detection limits, current applications of MIMS are predominantly limited to volatile and semivolatile analytes that permeate hydrophobic membranes (e.g., polydimethylsiloxane; PDMS). We report the first enzyme modified PDMS membrane for use with MIMS. This was achieved by immobilizing Candida rugosa lipase directly onto the surface of oxidized PDMS. These surface immobilized enzymes catalyze ester hydrolysis, releasing an alcohol product at the membrane interface that is readily detected. We have successfully used an enzyme modified membrane for the analysis and quantification of low-volatility and hydrophilic esters. We report the quantification of several carboxylic acid esters in dilute aqueous solutions, including a phthalate monoester carboxylate that is not readily detected by conventional MIMS. This new interface demonstrates the potential for extending the range and versatility of MIMS.

  20. Influence of PDMS encapsulation on the sensitivity and frequency range of fiber-optic interferometer (United States)

    Nedoma, Jan; Fajkus, Marcel; Vasinek, Vladimir


    Fiber-optic sensors are one of the dynamically developing areas of photonics and photonic applications. This group of sensors can also include fiber-optic interferometers which enable very sensitive sensing. They are entirely passive regarding power supply, and immune to electromagnetic interference. This type of sensor is dependent on the phase change. It mostly used in the field which requires high measurement accuracy. We can achieve a change of sensitivity in the order of 10-8. The fundamental problem of fiber-optic interferometry is a design and imposition (encapsulation) of the measuring arm and reference arm of the interferometer. Polydimethylsiloxane elastomer (PDMS) is one of the possibilities to encapsulation of the sensory arm. Two-component PDMS Sylgard 184 is used type. The article analyzes the effect of encapsulation into a PDMS of the measuring arm of the interferometer to frequency response and sensitivity of the Mach-Zehnder interferometer with the division of power in a ratio of 1:1 (measuring arm and reference arm). Input power set to a reference value of 1 mW, this value was constant for all performed experimental measurements. The generator of a harmonic signal with fixed amplitude signal used for analysis of the frequency characteristic of the interferometer. The application written in LabView development environment, evaluated the amplitude-frequency spectra of the signal. Repeated test of assembled prototype verified the measured results.

  1. Development of PDMS-based flexible dry type SEMG electrodes by micromachining technologies (United States)

    Jung, Jung Mo; Cha, Doo Yeol; Kim, Deok Su; Yang, Hee Jun; Choi, Kyo Sang; Choi, Jong Myoung; Chang, Sung Pil


    The authors developed PDMS (polydimethylsiloxane)-based dry type surface electromyography (SEMG) electrodes for myoelectric prosthetic hands. The SEMG electrodes were strongly recommended to be fabricated on a flexible substrate to be compatible with the surface of skin. In this study, the authors designed a bar-shaped dry-type flexible SEMG electrodes comprised of two input electrodes and a reference electrode on a flexible PDMS substrate to measure EMG signals. The space distance between each electrode with a size of 10 mm × 2 mm was chosen to 18 mm to get optimal result according to the simulation result with taking into consideration the conduction velocity and the median frequency of EMG signals. Raw EMG signals were measured from Brachioradialis, Biceps brachii, deltoideus, and pectoralis major muscles, to drive the application of the myoelectric hand prosthesis. Measured raw EMG signals were transformed to root mean square (RMS) EMG signals using Acqknowledge4.2. The experimental peak voltage values of RMS EMG signals from Brachioradialis, Biceps brachii, deltoideus, and pectoralis major muscles were 2.96 V, 4.45 V, 1.74 V, and 2.62 V, respectively. Values from the dry type flexible SEMG electrodes showed higher peak values than a commercially available wet type Ag-AgCl electrode. The study shows that the PDMS-based flexible electrode devised for measuring myoelectric signals from the surface of skin is more useful for prosthetic hands because of its greater sensitivity and flexibility.

  2. PDMS-BaTiO3 Composites with Mechanically Tunable Optical Properties. (United States)

    Mohamed, Nasser; Hinojosa, Moises; Gonzalez, Virgilio


    Novel composites that show visible light transmittance, mechanically tunable refractive index and good mechanical properties based on PDMS and BaTiO3 (BT) nanoparticles (NP), were prepared in 2 steps. First, NP were obtained via mechanical milling; the BT was used as-purchased. Average particle sizes of ˜100nm were selected. Second, the NP were embedded into PDMS by in-situ polymerization. PDMS from Dow Corning (Sylgard 184) was supplied as a kit containing 2 components: the Base and the Curing Agent. The BT content was varied up to 1.0wt%. Finally, thick films were prepared by solvent casting and cured in a vacuum furnace, where the trapped air and solvent were extracted. Weight content of the NP was examined. XRD and Raman confirmed the desired tetragonal phase of BT NP. Average particle size was determined by SEM. EDS maps revealed a homogeneous dispersion of the NP. UV-Vis analysis showed transmittances of ˜70%. The ellipsometry results revealed that the wt% of BT significantly influences the optical response of the composite when it is stressed; however the response is not linear.

  3. A novel PDMS micro membrane biosensor based on the analysis of surface stress. (United States)

    Sang, Shengbo; Witte, Hartmut


    The biological and medical application of biosensors is more and more important with the development of technology and society. Detection of cells and biological molecules utilizing biosensors based on the analysis of surface stress would facilitate inexpensive and high-throughput test and diagnosis. This paper presents a biocompatible surface stress-based polydimethylsiloxane (PDMS) micro membrane biosensor. Each biosensor chip consists of two available PDMS micro membranes, one acts as active membrane and the other as reference. Biosensors were functionalized using different functional materials respectively: MUA (11 Mercapto 1 undecanoicacid), MUO (11 Mercapto 1 undecanol) and DOT (Dodecane thiol). Two biosensor test systems were built based on a white light interferometer and a fiber optic interferometer respectively. Finally, testing experiments using Escherichia coli (E. coli) were performed based on the biosensor test systems we built. The results of the experiments showed that the MUA is a better functional material to functionalize the biosensor membranes than MUO and DOT for E. coli detection, some properties of E. coli, such as healthily living and dead status, can be analyzed based on the PDMS micro membrane biosensors.

  4. Minimal dead-volume connectors for microfluidics using PDMS casting techniques (United States)

    Chiou, Chi-Han; Lee, Gwo-Bin


    This paper presents a minimal dead-volume micro-connector fabricated using poly-dimethylsiloxane (PDMS) casting techniques for microfluidic applications. A simple and versatile method of fabricating a micro-connector to have an efficient interconnection to external large-scale fluid equipment was demonstrated. To eliminate the dead volume, a capillary was bridged to a micro-channel via a connection channel, which was formed by the removal of a metal wire after the PDMS casting process. The new method does not require any adhesive, precise drilling, delicate alignment procedure and micromachining processes. It could also effectively prevent blocking of the capillaries which was commonly observed while using adhesives. With this approach, detachable and reusable micro-connectors with a minimal dead volume could be achieved. According to leakage tests, the micro-connector could withstand pressures up to 150 psi and a maximum flow rate of 50 µl min-1. The pull-out tests indicated that the PDMS fitting could provide enough mechanical strength for practical applications. Not only does this micro-connector significantly eliminate the dead volume, but it also increases the detection signal. While compared with more conventional Teflon tubing fitting, the micro-connector could reduce by at least 50% the dilution effect for sample loading analysis due to substantial elimination of the dead volume. Most importantly, this micro-connector has greater versatility for coupling capillaries to various kinds of microfluidic chips made of different materials.

  5. Siloxane-based photonic structures and their application in optic and optoelectronic devices (United States)

    Pudiš, Dušan; Šušlik, Łuboš; Jandura, Daniel; Goraus, Matej; Figurová, Mária; Martinček, Ivan; Gašo, Peter


    Polymer based photonics brings simple and cheap solutions often with interesting results. We present capabilities of some siloxanes focusing on polydimethylsiloxane (PDMS) with unique mechanical and optical properties. In combination of laser lithography technologies with siloxane embossing we fabricate different grating structures with one- and two-dimensional symmetry. Concept of PDMS based thin membranes with patterned surface as an effective diffraction element for modification of radiation pattern diagram of light emitting diodes is here shown. Also the PDMS was used as an alternative material for fabrication of complicated waveguide with implemented Bragg grating. For lab-on-chip applications, we patterned PDMS microstructures for microfluidic and micro-optic devices.

  6. Non-Abelian magnetic black strings versus black holes (United States)

    Mazharimousavi, S. Habib; Halilsoy, M.


    We present d+1 -dimensional pure magnetic Yang-Mills (YM) black strings (or 1-branes) induced by the d -dimensional Einstein-Yang-Mills-Dilaton black holes. The Born-Infeld version of the YM field makes our starting point which goes to the standard YM field through a limiting procedure. The lifting from black holes to black strings (with less number of fields) is done by adding an extra, compact coordinate. This amounts to the change of horizon topology from S^{d-2} to a product structure. Our black string in 5 dimensions is a rather special one, with uniform Hawking temperature and non-asymptotically flat structure. As the YM charge becomes large the string gets thinner to tend into a breaking point and transform into a 4-dimensional black hole.


    Institute of Scientific and Technical Information of China (English)

    Xia Zhan; Ji-ding Li; Jun-qi Huang; Cui-xian Chen


    Ethanol perm-selective PDMS/PVDF composite membranes were prepared by curing polydimethylsiloxane (PDMS) with various cross-linking reagents, such as tetraethoxylsilane (TEOS), γ-aminopropyltriethoxylsilane (APTEOS), phenyltrimethoxylsilane (PTMOS) and octyltrimethoxylsilane (OTMOS) as well. The cross-linking density and surface properties of the PDMS active layer were adjusted by varying cross-linking reagents. The pervaporation performance of PDMS membranes cured with different cross-linking reagents was investigated in detail. As temperature increased, the total flux of the four kinds of membranes all increased exponentially, and the separation factor followed a reversed order. The increase of thickness of PDMS layers depressed the total flux of composite membranes and had no obvious effect on selectivity of ethanol. It was found that the composite membrane cured by PTMOS showed much better separation performance compared with other membranes. A resistance-in-series model was used to investigate and estimate the overall mass transfer coefficients and boundary layer mass transfer coefficients of ethanol and water according to experimental results. The measured diffusivities of ethanol and water in PDMS membranes had a magnitude of 10-10 m2·s-1 and 10-11 m2·s-1 at 313.15 K, respectively.

  8. Critical behavior and microscopic structure of charged AdS black holes via an alternative phase space

    Directory of Open Access Journals (Sweden)

    Amin Dehyadegari


    Full Text Available It has been argued that charged Anti-de Sitter (AdS black holes have similar thermodynamic behavior as the Van der Waals fluid system, provided one treats the cosmological constant as a thermodynamic variable (pressure in an extended phase space. In this paper, we disclose the deep connection between charged AdS black holes and Van der Waals fluid system from an alternative point of view. We consider the mass of an AdS black hole as a function of square of the charge Q2 instead of the standard Q, i.e. M=M(S,Q2,P. We first justify such a change of view mathematically and then ask if a phase transition can occur as a function of Q2 for fixed P. Therefore, we write the equation of state as Q2=Q2(T,Ψ where Ψ (conjugate of Q2 is the inverse of the specific volume, Ψ=1/v. This allows us to complete the analogy of charged AdS black holes with Van der Waals fluid system and derive the phase transition as well as critical exponents of the system. We identify a thermodynamic instability in this new picture with real analogy to Van der Waals fluid with physically relevant Maxwell construction. We therefore study the critical behavior of isotherms in Q2–Ψ diagram and deduce all the critical exponents of the system and determine that the system exhibits a small–large black hole phase transition at the critical point (Tc,Qc2,Ψc. This alternative view is important as one can imagine such a change for a given single black hole i.e. acquiring charge which induces the phase transition. Finally, we disclose the microscopic properties of charged AdS black holes by using thermodynamic geometry. Interestingly, we find that scalar curvature has a gap between small and large black holes, and this gap becomes exceedingly large as one moves away from the critical point along the transition line. Therefore, we are able to attribute the sudden enlargement of the black hole to the strong repulsive nature of the internal constituents at the phase transition.

  9. Thermodynamical structure of AdS black holes in massive gravity with stringy gauge-gravity corrections (United States)

    Hendi, S. H.; Eslam Panah, B.; Panahiyan, S.


    Motivated by gauge/gravity group in the low energy effective theory of the heterotic string theory and novel aspects of massive gravity in the context of lattice physics, the minimal coupling of Gauss-Bonnet-massive gravity with Born-Infeld electrodynamics is considered. At first, the metric function is calculated and then the geometrical properties of the solutions are investigated. It is found that there is an essential singularity at the origin and the intrinsic curvature is regular elsewhere. In addition, the effects of massive parameters are studied and black hole solutions with multi horizons are found in this gravity. Also, the conserved and thermodynamic quantities are calculated, and it is shown that the solutions satisfy the first law of thermodynamics. Furthermore, using heat capacity of these black holes, thermal stability and phase transitions are investigated. The variation of different parameters and related modifications on the (number of) phase transition are examined. Next, the critical behavior of the Gauss-Bonnet-Born-Infeld-massive black holes in the context of extended phase space is studied. It is shown how the variation of the different parameters affects the existence and absence of phase transition. Also, it is found that for specific values of different parameters, these black holes may enjoy the existence of a new type of phase transition which to our knowledge was not observed in black hole physics before.

  10. Black Culture

    Directory of Open Access Journals (Sweden)

    Angela Khristin Brown


    Full Text Available The migration of blacks in North America through slavery became united.  The population of blacks past downs a tradition of artist through art to native born citizens. The art tradition involved telling stories to each generation in black families. The black culture elevated by tradition created hope to determine their personal freedom to escape from poverty of enslavement and to establish a way of life through tradition. A way of personal freedoms was through getting a good education that lead to a better foundation and a better way of life.

  11. A small-angle neutron scattering study of the structure of graphitized carbon black aggregates in Triton X-100/water solutions

    DEFF Research Database (Denmark)

    Garamus, V.M.; Pedersen, J.S.


    The structure of graphitized carbon black (CB) aggregates dispersed in water solutions with a non-ionic surfactant are studied by small-angle neutron scattering using contrast variation by heavy/light water mixing. The addition of CB to Triton X-100/water mixtures shifts the critical micelle...... particles is 8% and is constant with varying CB and surfactant concentration. The volume fraction of the voids does not exceed 1% of the CB; The micelle structure is found to be the same as in surfactant/water solutions. (C) 1998 Elsevier Science B.V....

  12. OncomiR detection in circulating body fluids: a PDMS microdevice perspective. (United States)

    Potrich, Cristina; Vaghi, Valentina; Lunelli, Lorenzo; Pasquardini, Laura; Santini, Gaia Cecilia; Ottone, Chiara; Quaglio, Marzia; Cocuzza, Matteo; Pirri, Candido Fabrizio; Ferracin, Manuela; Negrini, Massimo; Tiberio, Paola; De Sanctis, Veronica; Bertorelli, Roberto; Pederzolli, Cecilia


    There is an increasing interest in circulating microRNAs (miRNAs) as potential minimally invasive diagnostic biomarkers in oncology. Considerable efforts are being made in the development of lab-on-a-chip devices for biomedical applications to purify and detect miRNAs from biological fluids. Here, we report the development of an innovative polydimethylsiloxane (PDMS)-based parallel device whose internal surface can opportunely be functionalized with positively charged 3-aminopropyltriethoxysilane (APTES) alone or mixed with two different neutral poly(ethylene glycol) silanes (PEG-s). The differently functionalized internal surfaces of the PDMS chip were characterized with s-SDTB (sulfosuccinimidyl-4-o-(4,4-dimethoxytrityl) butyrate) and the portion of the surface able to adsorb a synthetic fluorescently labeled miRNA was determined. Interestingly, the adsorbed miRNA (both synthetic and cell supernatant-derived) was found mainly on the bottom surface of the chip and could be reverse transcribed into cDNA directly on the same PDMS chip used for its purification, saving hours with respect to the use of standard purification kits. We identified 0.1% APTES/0.9% PEG-silane as the most efficient PDMS functionalization to capture both synthetic and extracellular miRNA. Moreover, the amount of captured miRNA was increased by treating the cell supernatant with a commercially available lysis buffer for RNA extraction. We assessed that the available miRNA binding sites on the functionalized surface were efficiently saturated with only one incubation, shortening the time and greatly simplifying the protocol for miRNA purification from biological samples. Finally, the extracellular miRNA purification efficiency of the PDMS functionalized multichip determined via real-time quantitative polymerase chain reaction (RT-qPCR) was confirmed by droplet digital PCR (ddPCR) quantification. This work shows an innovative, rapid and easy to use microdevice for the purification and reverse

  13. The absence of concordant population genetic structure in the black-tailed prairie dog and the flea, Oropsylla hirsuta, with implications for the spread of Yersinia pestis. (United States)

    Jones, Philip H; Britten, Hugh B


    The black-tailed prairie dog (Cynomys ludovicianus) is a keystone species on the mid- and short-grass prairies of North America. The species has suffered extensive colony extirpations and isolation as a result of human activity including the introduction of an exotic pathogen, Yersinia pestis, the causative agent of sylvatic plague. The prairie dog flea, Oropsylla hirsuta, is the most common flea on our study colonies in north-central Montana and it has been shown to carry Y. pestis. We used microsatellite markers to estimate the level of population genetic concordance between black-tailed prairie dogs and O. hirsuta in order to determine the extent to which prairie dogs are responsible for dispersing this potential plague vector among prairie dog colonies. We sampled fleas and prairie dogs from six prairie dog colonies in two regions separated by about 46 km. These colonies were extirpated by a plague epizootic that began months after our sampling was completed in 2005. Prairie dogs showed significant isolation-by-distance and a tendency toward genetic structure on the regional scale that the fleas did not. Fleas exhibited higher estimated rates of gene flow among prairie dog colonies than the prairie dogs sampled from the same colonies. While the findings suggested black-tailed prairie dogs may have contributed to flea dispersal, we attributed the lack of concordance between the population genetic structures of host and ectoparasite to additional flea dispersal that was mediated by mammals other than prairie dogs that were present in the prairie system.

  14. Analyses of Composition and Structure on the Ancient Bronze Black Mirror“Hei-Qi-Gu”and Search Into the Treating Process of Its Surface Layer

    Institute of Scientific and Technical Information of China (English)

    范崇正; Suzuki Minoru; Inoue Miyoshi; Abe Tadahiro; Muraua Mitsuo; Asashi Ishikawa; 吴佑实; 李志超


    The Chinese ancient bronze black mirror"Hei-Qi-Gu"is famous for its black colour,brightsurface and anti-corroding property.In the present work,methods of SEM,IR,EPMA,Memhrane-XRD,and AFM were employed to detect the composition and structure of several pieces of Hei-Qi-Gu fragments.Itwas found that after casting,the surface of the bronze mirror was treated by a special process,and most ofCu was moved away while Sn and Si were rich in the surface layer.The oxides SnO2 and SiO2 on the surfacein a very small particle size are particularly stable and they protect the bronze alloy successfully.The surface layer and the transition layer have been dissected mainly,and some important informa-tion has been obtained.The special treating process of the mirror surface is searched and discussed.

  15. The technicolor "big picture" of black hole evolution: Multiwavelength views of AGN, galaxies, and large-scale structures (United States)

    Hickox, Ryan C.


    Large multiwavelength extragalactic surveys have revolutionized our understanding of the cosmic evolution of supermassive black holes (SMBHs). I will discuss recent results on the host galaxies and clustering of AGN selected using a range of techniques from the radio to the hard X-ray wavebands, including data from the NuSTAR and WISE space observatories. I will show that relatively small dark matter halos hosting star-forming galaxies are connected with rapid but highly variable black hole growth that is often heavily obscured. In contrast, massive halos hosting passive galaxies are associated with slower, mechanically-dominated modes of black hole growth. I will conclude by discussing new analysis techniques for measuring AGN clustering and look to the future of large-scale extragalactic surveys.

  16. Thermodynamical Structure of AdS Black Holes in Massive Gravity with Stringy Gauge-Gravity Corrections

    CERN Document Server

    Hendi, S H; Panahiyan, S


    Motivated by gauge/gravity group in the low energy effective theory of the heterotic string theory, the minimal coupling of Gauss-Bonnet-massive gravity with Born-Infeld electrodynamics is considered. At first the metric function is calculated and then the geometrical properties of the solutions are investigated. It is found that there is an essential singularity at the origin and the intrinsic curvature is regular elsewhere. In addition, the effects of massive parameters on the horizons of black holes are studied and the conserved and thermodynamic quantities are calculated. Also, it is shown that the solutions satisfy the first law of thermodynamics. Furthermore using heat capacity of these black holes, thermal stability and phase transitions are investigated. The variation of different parameters and related modifications on the (number of) phase transition are examined. Next, the critical behavior of the Gauss-Bonnet-Born-Infeld-massive black holes in context of extended phase space is studied. It is show...

  17. Poly(dimethyl siloxane) (PDMS) network blends of amphiphilic acrylic copolymers with poly(ethylene glycol)-fluoroalkyl side chains for fouling-release coatings. II. Laboratory assays and field immersion trials. (United States)

    Martinelli, Elisa; Sarvothaman, Mahesh K; Galli, Giancarlo; Pettitt, Michala E; Callow, Maureen E; Callow, James A; Conlan, Sheelagh L; Clare, Anthony S; Sugiharto, Albert B; Davies, Cait; Williams, David


    Amphiphilic copolymers containing different amounts of poly(ethylene glycol)-fluoroalkyl acrylate and polysiloxane methacrylate units were blended with a poly(dimethyl siloxane) (PDMS) matrix in different proportions to investigate the effect of both copolymer composition and loading on the biological performance of the coatings. Laboratory bioassays revealed optimal compositions for the release of sporelings of Ulva linza, and the settlement of cypris larvae of Balanus amphitrite. The best-performing coatings were subjected to field immersion tests. Experimental coatings containing copolymer showed significantly reduced levels of hard fouling compared to the control coatings (PDMS without copolymer), their performance being equivalent to a coating based on Intersleek 700™. XPS analysis showed that only small amounts of fluorine at the coating surface were sufficient for good antifouling/fouling-release properties. AFM analyses of coatings under immersion showed that the presence of a regular surface structure with nanosized domains correlated with biological performance.

  18. A Structural Equation Model of HIV-Related Stigma, Racial Discrimination, Housing Insecurity and Wellbeing among African and Caribbean Black Women Living with HIV in Ontario, Canada. (United States)

    Logie, Carmen H; Jenkinson, Jesse I R; Earnshaw, Valerie; Tharao, Wangari; Loutfy, Mona R

    African and Caribbean Black women in Canada have new HIV infection rates 7 times higher than their white counterparts. This overrepresentation is situated in structural contexts of inequities that result in social, economic and health disparities among African and Caribbean Black populations. Economic insecurity is a distal driver of HIV vulnerability, reducing access to HIV testing, prevention and care. Less is known about how economic insecurity indicators, such as housing security, continue to influence the lives of women living with HIV following HIV-positive diagnoses. The aim of this study was to test a conceptual model of the pathways linking HIV-related stigma, racial discrimination, housing insecurity, and wellbeing (depression, social support, self-rated health). We implemented a cross-sectional survey with African and Caribbean Black women living with HIV in 5 Ontario cities, and included 157 participants with complete data in the analyses. We conducted structural equation modeling using maximum likelihood estimation to evaluate the hypothesized conceptual model. One-fifth (22.5%; n = 39) of participants reported housing insecurity. As hypothesized, racial discrimination had significant direct effects on: HIV-related stigma, depression and social support, and an indirect effect on self-rated health via HIV-related stigma. HIV-related stigma and housing insecurity had direct effects on depression and social support, and HIV-related stigma had a direct effect on self-rated health. The model fit the data well: χ2 (45, n = 154) = 54.28, p = 0.387; CFI = 0.997; TLI = 0.996; RMSEA = 0.016. Findings highlight the need to address housing insecurity and intersecting forms of stigma and discrimination among African and Caribbean Black women living with HIV. Understanding the complex relationships between housing insecurity, HIV-related stigma, racial discrimination, and wellbeing can inform multi-level interventions to reduce stigma and enhance health.

  19. A flexible triboelectric-piezoelectric hybrid nanogenerator based on P(VDF-TrFE) nanofibers and PDMS/MWCNT for wearable devices (United States)

    Wang, Xingzhao; Yang, Bin; Liu, Jingquan; Zhu, Yanbo; Yang, Chunsheng; He, Qing


    This paper studied and realized a flexible nanogenerator based on P(VDF-TrFE) nanofibers and PDMS/MWCNT thin composite membrane, which worked under triboelectric and piezoelectric hybrid mechanisms. The P(VDF-TrFE) nanofibers as a piezoelectric functional layer and a triboelectric friction layer are formed by electrospinning process. In order to improve the performance of triboelectric nanogenerator, the multiwall carbon nanotubes (MWCNT) is doped into PDMS patterned films as the other flexible friction layer to increase the initial capacitance. The flexible nanogenerator is fabricated by low cost MEMS processes. Its output performance is characterized in detail and structural optimization is performed. The device’s output peak-peak voltage, power and power density under triboelectric mechanism are 25 V, 98.56 μW and 1.98 mW/cm3 under the pressure force of 5 N, respectively. The output peak-peak voltage, power and power density under piezoelectric working principle are 2.5 V, 9.74 μW, and 0.689 mW/cm3 under the same condition, respectively. We believe that the proposed flexible, biocompatible, lightweight, low cost nanogenerator will supply effective power energy sustainably for wearable devices in practical applications.

  20. Novel Conductive Carbon Black and Polydimethlysiloxane ECG Electrode: A Comparison with Commercial Electrodes in Fresh, Chlorinated, and Salt Water. (United States)

    Noh, Yeonsik; Bales, Justin R; Reyes, Bersain A; Molignano, Jennifer; Clement, Amanda L; Pins, George D; Florian, John P; Chon, Ki H


    In this study, we evaluated the performance of two novel conductive carbon black (CB) and polydimethlysiloxane (PDMS) bio-potential electrodes, with and without an integrated flexible copper mesh, against commercially available electrodes (Polar(®) textile, Silver-coated textile, and carbon rubber). The electrodes were tested in three types of water (fresh/unfiltered, chlorinated, and salt water). Our testing revealed that our CB/PDMS electrode with integrated copper mesh provided a high-fidelity ECG signal morphologies without any amplitude degradation in all of the types of water tested (N = 10). The non-meshed CB/PDMS electrodes were also subjected to a long-term durability test by the US Navy SCUBA divers during which the electrodes maintained ECG signal quality for a 6 h period of continuous use. The results of a material degradation analysis revealed the CB/PDMS composite material does not exhibit significant changes in physical integrity after prolonged exposure to the test conditions. The newly developed meshed CB/PDMS electrodes have the potential to be used in a wide variety of both dry and wet environments including the challenge of obtaining ECG signals in salt water environments.

  1. Does Parenting Explain the Effects of Structural Conditions on Children's Antisocial Behavior? A Comparison of Blacks and Whites. (United States)

    McLeod, Jane D.; And Others


    Data on black children and white children over age six and their mothers (from National Longitudinal Survey of Youth) indicate no racial differences in total effects of poverty and single parenthood on parenting practices (affection and spanking). Parenting practices were reciprocally related to child's antisocial behavior for whites, but did not…

  2. Black German identities : validating the multidimensional inventory of black identity

    NARCIS (Netherlands)

    Wandert, T.; Ochsmann, R.; Brug, P.; Chybicka, A.; Lacassagne, M.F.; Verkuyten, M.J.A.M.


    This study examines the reliability and validity of a German version of the Multidimensional Inventory of Black Identity (MIBI) in a sample of 170 Black Germans. The internal consistencies of all subscales are at least moderate. The factorial structure of the MIBI, as assessed by principal component

  3. Research on marking lines of silicone elastomer PDMS for super-hydrophobic surface fabrication based on picosecond laser (United States)

    Gang, Xiao; Dong, Shiyun; Yan, Shixing; Song, Chaoqun; Wang, Bin


    The picosecond laser has ultrashort pulse and superstrong peak power, which make it being focused on and applied in the micro-nanoscale fabrication field. Silicone elastomer PDMS is a typical antifouling material which can desorb defacement, using picosecond laser etching the surface through the way of galvanometer scanning in order to obtain a surface with micro-nano texture. The article studied the relationship between process parameters such as the power density, the scanning rate and the appearance of etched groove respectively, especially the width and depth of the groove. The results show that : for single marking, with the raise of the laser power density I, the depth of the groove increases, the inclination angle of the side wall is reduced. In another time, with the increase of the scanning rate v ,the depth of the groove decreases gradually and the surface morphology cannot be seen clearly. For multiple marking, the depth of the groove shown a falling slope from big to small with the increase of marking number. Finally,we got a path to optimize the process parameters to obtain a surface with micro-nano structures. After testing the surface contact angle, we found that the surface contact angle increased from 113° to 152°,which reached the level of superhydrophobic surface.

  4. Thermodynamics of Accelerating Black Holes. (United States)

    Appels, Michael; Gregory, Ruth; Kubizňák, David


    We address a long-standing problem of describing the thermodynamics of an accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon-even though the event horizon contains a conical singularity. This result not only extends the applicability of black hole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability, and phase structure of these black holes.

  5. Black holes in brane worlds

    Indian Academy of Sciences (India)

    M S Modgil; S Panda; S Sengupta


    A Kerr metric describing a rotating black hole is obtained on the three brane in a five-dimensional Randall-Sundrum brane world by considering a rotating five-dimensional black string in the bulk. We examine the causal structure of this space-time through the geodesic equations.

  6. Anti-icing properties of superhydrophobic ZnO/PDMS composite coating (United States)

    Yang, Chao; Wang, Fajun; Li, Wen; Ou, Junfei; Li, Changquan; Amirfazli, Alidad


    We present the excellent anti-icing performance for a superhydrophobic coating surface based on ZnO/polydimethylsiloxane (ZnO/PDMS) composite. The superhydrophobic ZnO/PDMS coating surface was prepared by a facile solution mixing, drop coating, room-temperature curing and surface abrading procedure. The superhydrophobic ZnO/PDMS composite coating possesses a water contact angle of 159.5° and a water sliding angle of 8.3° at room temperature (5 °C). The anti-icing properties of the superhydrophobic coating were investigated by continuously dropping cold-water droplets (about 0 °C) onto the pre-cooled surface using a home-made apparatus. The sample was placed at different tilting angle (0° and 10°) and pre-cooled to various temperatures (-5, -10 and -15 °C) prior to measure. The pure Al surface was also studied for comparison. It was found that icing accretion on the surface could be reduced apparently because the water droplets merged together and slid away from the superhydrophobic surface at all of the measuring temperatures when the surface is horizontally placed. In addition, water droplet slid away completely from the superhydrophobic surface at -5 and -10 °C when the surface is tilted at 10°, which demonstrates its excellent anti-icing properties at these temperatures. When the temperature decreased to -15 °C, though ice accretion on the tilted superhydrophobic coating surface could not be avoided absolutely, the amount of ice formed on the surface is very small, which indicated that the coating surface with superhydrophobicity could significantly reduce ice accumulation on the surface at very low temperature (-15 °C). Importantly, the sample is also stable against repeated icing/deicing cycles. More meaningfully, once the superhydrophobic surface is damaged, it can be repaired easily and rapidly.

  7. Enhancing Performance of Triboelectric Nanogenerator by Filling High Dielectric Nanoparticles into Sponge PDMS Film. (United States)

    Chen, Jie; Guo, Hengyu; He, Xianming; Liu, Guanlin; Xi, Yi; Shi, Haofei; Hu, Chenguo


    Understanding of the triboelectric charge accumulation from the view of materials plays a critical role in enhancing the output performance of triboelectric nanogenerator (TENG). In this paper, we have designed a feasible approach to modify the tribo-material of TENG by filling it with high permittivity nanoparticles and forming pores. The influence of dielectricity and porosity on the output performance is discussed experimentally and theoretically, which indicates that both the surface charge density and the charge transfer quantity have a close relationship with the relative permittivity and porosity of the tribo-material. A high output performance TENG based on a composite sponge PDMS film (CS-TENG) is fabricated by optimizing both the dielectric properties and the porosity of the tribo-material. With the combination of the enhancement of permittivity and production of pores in the PDMS film, the charge density of ∼19 nC cm(-2), open-circuit voltage of 338 V, and power density of 6.47 W m(-2) are obtained at working frequency of 2.5 Hz with the optimized film consisting of 10% SrTiO3 nanoparticles (∼100 nm in size) and 15% pores in volume, which gives over 5-fold power enhancement compared with the nanogenerator based on the pure PDMS film. This work gives a better understanding of the triboelectricity produced by the TENG from the view of materials and provides a new and effective way to enhance the performance of TENG from the material itself, not just its surface modification.

  8. Black holes and the multiverse (United States)

    Garriga, Jaume; Vilenkin, Alexander; Zhang, Jun


    Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.

  9. A clinoptilolite-PDMS mixed-matrix membrane for high temperature water softening. (United States)

    Yazdanbakhsh, Farzad; Alizadehgiashi, Moien; Sawada, James A; Kuznicki, Steven M


    A mixed-matrix membrane composed of polydimethylsiloxane (PDMS) as the continuous phase and clinoptilolite, a naturally occurring zeolite, as the active phase has been used to decrease the conductivity of water by more than 80% across the membrane. Testing was carried out using a cross-flow configuration at temperatures as high as 160 °C using a constant transmembrane pressure of 8 bar. The simple fabrication method for the membrane, the durability of the system under the test conditions, and a suitable flux rate make such membranes promising candidates for industrial wastewater treatment.

  10. More Fluorous Surface Modifier Makes it Less Oleophobic: Fluorinated-Siloxane Copolymer/PDMS Coatings


    Zhang, Wei; Zheng, Ying; Orsini, Lorenzo; Morelli, Andrea; Galli, Giancarlo; Chiellini, Emo; Carpenter, Everett E.; Wynne, Kenneth J.


    A copolyacrylate with semifluorinated and polydimethylsiloxane side chains (D5-3) was used as a surface modifier for a condensation cured PDMS coating. The decyl fluorous group is represented by “D”; “5” is a 5 kDa silicone, and “3” the mole ratio of fluorous to silicone side chain. Wetting behavior was assessed by dynamic contact angle (DCA) analysis using isopropanol, which differentiates silicone and fluorous wetting behavior. Interestingly, a maximum in surface oleophobicity was found at ...

  11. Simple fabrication of hydrophilic nanochannels using the chemical bonding between activated ultrathin PDMS layer and cover glass by oxygen plasma. (United States)

    Kim, So Hyun; Cui, Yidan; Lee, Min Jung; Nam, Seong-Won; Oh, Doori; Kang, Seong Ho; Kim, Youn Sang; Park, Sungsu


    This study describes a simple and low cost method for fabricating enclosed transparent hydrophilic nanochannels by coating low-viscosity PDMS (monoglycidyl ether-terminated polydimethylsiloxane) as an adhesion layer onto the surface of the nanotrenches that are molded with a urethane-based UV-curable polymer, Norland Optical Adhesive (NOA 63). In detail, the nanotrenches made of NOA 63 were replicated from a Si master mold and coated with 6 nm thick layer of PDMS. These nanotrenches underwent an oxygen plasma treatment and finally were bound to a cover glass by chemical bonding between silanol and hydroxyl groups. Hydrophobic recovery that is observed in the bulk PDMS was not observed in the thin film of PDMS on the mold and the PDMS-coated nanochannel maintained its surface hydrophilicity for at least one month. The potentials of the nanochannels for bioapplications were demonstrated by stretching λ-DNA (48,502 bp) in the channels. Therefore, this fabrication approach provides a practical solution for the simple fabrication of the nanochannels for bioapplications.

  12. Prevention of Heaving in Structures Built on Black Shale by Prevention of Crystal Growth within the Shales. (United States)


    gypsum growth within natural black shale environments. - 10 - TABLE I ORGANIC ADDITIVES USED IN PROJECT ADDITIVE SOURCE Amino Acetic Acid Pfanstiehl...EDTA Iowa State University Labs EMA 1103 Monsanto? Ethoquad 6012909 R113-50 Armak Ethoquad 6921305 RI15-50 Armak Gallic Acid JT Baker Glutamic Acid Iowa...the acid character of the additive. Duplicate experi- ments were used for each time period. Symbols are the same as in Figs. 2 and 3. Dequest 2060

  13. Structural Properties and Antifungal Activity against Candida albicans Biofilm of Different Composite Layers Based on Ag/Zn Doped Hydroxyapatite-Polydimethylsiloxanes

    Directory of Open Access Journals (Sweden)

    Andreea Groza


    Full Text Available Modern medicine is still struggling to find new and more effective methods for fighting off viruses, bacteria and fungi. Among the most dangerous and at times life-threatening fungi is Candida albicans. Our work is focused on surface and structural characterization of hydroxyapatite, silver doped hydroxyapatite and zinc doped hydroxyapatite deposited on a titanium substrate previously coated with polydimethylsiloxane (HAp-PDMS, Ag:HAp-PDMS, Zn:HAp-PDMS by different techniques: Scanning Electron Microscopy (SEM, Glow Discharge Optical Emission Spectroscopy (GDOES and Fourier Transform Infrared Spectroscopy (FTIR. The morphological studies revealed that the use of the PDMS polymer as an interlayer improves the quality of the coatings. The structural characterizations of the thin films revealed the basic constituents of both apatitic and PDMS structure. In addition, the GD depth profiles indicated the formation of a composite material as well as the successful embedding of the HAp, Zn:HAp and Ag:HAp into the polymer. On the other hand, in vitro evaluation of the antifungal properties of Ag:HAp-PDMS and Zn:HAp-PDMS demonstrated the fungicidal effects of Ag:HAp-PDMS and the potential antifungal effect of Zn:HAp-PDMS composite layers against C. albicans biofilm. The results acquired in this research complete previous research on the potential use of new complex materials produced by nanotechnology in biomedicine.

  14. Black tea (United States)

    ... combination.Talk with your health provider.Birth control pills (Contraceptive drugs)Black tea contains caffeine. The body breaks down caffeine to get rid of it. Birth control pills can decrease how quickly the body breaks down ...

  15. Resource Letter BH-1: Black Holes. (United States)

    Detweiler, Steven


    Lists resources on black holes, including: (1) articles of historical interest; (2) books and journal articles on elementary expositions; (3) elementary and advanced textbooks; and (4) research articles on analytic structure of black holes, black hole dynamics, and astrophysical processes. (SK)

  16. Treatment of PDMS surfaces using pulsed DBD plasmas: comparing the use of different gases and its influence on adhesion

    CERN Document Server

    Nascimento, Fellype do; Machida, Munemasa; Parada, Sergio


    In this work we present some results of the treatment of polydimethylsiloxane (PDMS) surfaces using pulsed dielectric barrier discharge plasmas. The results of plasma treatment using different gases to produce the plasmas (argon, argon plus water, helium, helium plus water, nitrogen and nitrogen plus water) were compared testing the adhesion between two PDMS samples for each kind of plasma. We also studied the water contact angle in function of plasma process time of PDMS surfaces with each kind of plasma. The plasmas were characterized by optical emission spectroscopy to identify the emitting species and determine plasma temperatures through comparison with emission spectra simulations. Measurements of power delivered to the plasmas were also performed. Plasmas of all gases are good enough for surface treatment with long exposure time. But when only a few discharges are applied the best choice is the helium plasma.

  17. Optical performance of a PDMS tunable lens with automatically controlled applied stress (United States)

    Cruz-Felix, Angel S.; Santiago-Alvarado, Agustín.; Hernández-Méndez, Arturo; Reyes-Pérez, Emilio R.; Tepichín-Rodriguez, Eduardo


    The advances in the field of adaptive optics and in the fabrication of tunable optical components capable to automatically modify their physical features are of great interest in areas like machine vision, imaging systems, ophthalmology, etc. Such components like tunable lenses are used to reduce the overall size of optical setups like in small camera systems and even to imitate some biological functions made by the human eye. In this direction, in the last years we have been working in the development and fabrication of PDMS-made tunable lenses and in the design of special mechanical mounting systems to manipulate them. A PDMS-made tunable lens was previously designed by us, following the scheme reported by Navarro et al. in 1985, in order to mimic the accommodation process made by the crystalline lens of the human eye. The design included a simulation of the application of radial stress onto the lens and it was shown that the effective focal length was indeed changed. In this work we show the fabrication process of this particular tunable lens and an optimized mechanism that is able to automatically change the curvature of both surfaces of the lens by the application of controlled stress. We also show results of a study and analysis of aberrations performed to the Solid Elastic Lens (SEL).

  18. XPS and μ-Raman study of nanosecond-laser processing of poly(dimethylsiloxane) (PDMS)

    Energy Technology Data Exchange (ETDEWEB)

    Armyanov, S., E-mail: [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, Sofia 1113 (Bulgaria); Stankova, N.E.; Atanasov, P.A. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Shose, Sofia 1784 (Bulgaria); Valova, E.; Kolev, K.; Georgieva, J. [Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Block 11, Sofia 1113 (Bulgaria); Steenhaut, O.; Baert, K.; Hubin, A. [Vrije Universiteit Brussels, Faculty of Engineering, Research Group, SURF “Electrochemical and Surface Engineering” (Belgium)


    Data about the chemical status of poly(dimethylsiloxane) (PDMS) after nanosecond Q-switched Nd:YAG laser treatment with near infrared, visible and ultraviolet radiation are presented. The μ-Raman spectroscopy analyses reveal as irradiation result a new sharp peak of crystalline silicon. In addition, broad bands appear assigned to D band of amorphous carbon and G band of microcrystalline and polycrystalline graphite. The μ-Raman spectra are variable taken in different inspected points in the trenches formed by laser treatment. The XPS surface survey spectra indicate the constituent elements of PDMS: carbon, oxygen and silicon. The spectra of detail XPS scans illustrate the influence of the laser treatment. The position of Si 2p peaks of the treated samples is close to the value of non-treated except that irradiated by 1064 nm 66 pulses, which is shifted by 0.9 eV. Accordingly, a shift by 0.4 eV is noticed of the O 1s peak, which reflects again a stronger oxidation of silicon. The curve fitting of Si 2p and O 1s peaks after this particular laser treatment shows the degree of conversion of organic to inorganic silicon that takes place during the irradiation.

  19. Electrohydrodynamic Generation and Delivery of Monodisperse Pico-Liter Droplets Using PDMS Microchip (United States)

    Kim, Sung Jae; Song, Yong-Ak; Skipper, Paul L.; Han, Jongyoon


    We developed a drop-on-demand microdroplet generator for the discrete dispensing of biosamples into a bio-analytical unit. This disposable PDMS microfluidic device can generate monodisperse droplets of pico-liter volume directly out of a plane sidewall of the microfluidic chip by an electrohydrodynamic mechanism. The droplet generation was accomplished without using either an inserted capillary or monolithically built-in tip. The minimum droplet volume was around 4 pico-liters, and the droplet generation was repeatable and stable for at least 30 minutes, with a typical variation of less than 2.0% of drop size. The Taylor cone, which is usually observed in electrospray, was suppressed by controlling the surface wetting property of the PDMS device as well as the surface tension of the sample liquids. A modification of the channel geometry right before the opening of the microchannel also enhanced the continuous droplet generation without applying any external pumping. A simple numerical simulation of the droplet generation verified the importance of controlling the surface wetting conditions for the droplet formation. Our microdroplet generator can be effectively applied to a direct interface of a microfluidic chip to a bio-sensing unit, such as AMS, MALDI-MS or protein microarray-type biochips. PMID:17134134

  20. Separation of natural antioxidants using PDMS electrophoresis microchips coupled with amperometric detection and reverse polarity. (United States)

    Lucca, Bruno Gabriel; Lunte, Susan Marie; Tomazelli Coltro, Wendell Karlos; Ferreira, Valdir Souza


    This report describes the use of PDMS ME coupled with amperometric detection for rapid separation of ascorbic, gallic , ferulic, p-coumaric acids using reverse polarity. ME devices were fabricated in PDMS by soft lithography and detection was accomplished using an integrated carbon fiber working electrode aligned in the end-channel configuration. Separation and detection parameters were investigated and the best conditions were obtained using a run buffer consisting of 5 mM phosphate buffer (pH 6.9) and a detection voltage of 1.0 V versus Ag/AgCl reference electrode. All compounds were separated within 70 s using gated injection mode with baseline resolution and separation efficiencies between 1200 and 9000 plates. Calibration curves exhibited good linearity and the LODs achieved ranged from 1.7 to 9.7 μM. The precision for migration time and peak height provided maximum values of 4% for the intrachip studies. Lastly, the analytical method was successfully applied for the analysis of ascorbic and gallic acids in commercial beverage samples. The results achieved using ME coupled with amperometric detection were in good agreement with the values provided by the supplier. Based on the data reported here, the proposed method shows suitability to be applied for the routine analysis of beverage samples.

  1. Micro pumping methods based on AC electrokinetics and Electrorheologically actuated PDMS valves (United States)

    Soni, Gaurav; Squires, Todd; Meinhart, Carl


    We have developed 2 different micropumping methods for transporting ionic fluids through microchannels. The first method is based on Induced Charge Electroosmosis (ICEO) and AC flow field-effect. We used an AC electric field to produce a symmetric ICEO flow on a planar electrode, called `gate'. In order to break the symmetry of ICEO, we applied an additional AC voltage to the gate electrode. Such modulation of the gate potential is called field effect and produces a unidirectional pumping over the gate surface. We used micro PIV to measure pumping velocities for a range of ionic concentration, AC frequency and gate voltage. We have also conducted numerical simulations to understand the deteriorating effect of lateral conduction of surface charge on the pumping velocities. The second method is based on vibration of a flexible PDMS diaphragm actuated by an electrorheological (ER) fluid. ER fluid is a colloidal suspension exhibiting a reversible liquid-to-solid transition under an electric field. This liquid-to-solid transition can yield very high shear stress and can be used to open and close a PDMS valve. Three such valves were fabricated and actuated in a peristaltic fashion in order to achieve positive displacement pumping of fluids.

  2. Optimization of the replica molding process of PDMS using pennate diatoms (United States)

    Hlúbiková, D.; Luís, A. T.; Vaché, V.; Ector, L.; Hoffmann, L.; Choquet, P.


    Biomimetic fabrication of nanostructured materials has recently attracted the attention of researchers as a cost-effective and easily applicable method of nanotexturing. Different techniques and materials have been used in order to replicate natural patterns, among which polydimethylsiloxane (PDMS Sylgard 184®) was recently used to replicate the micro- and nanoscale patterns from centric diatoms. In this paper, we test the reproducibility and precision of this approach using various morphologically different diatom species trying to optimize the molding parameters. The optimization process is focused on immobilization of diatoms on the glass support, which serves as a master for templating, as well as on the parameters of PDMS fabrication such as the ratio of the curing agent and elastomer, use of vacuum, curing time and temperature. The results indicate that higher ratios of curing agent and elastomer, longer curing time and lower temperature are the most favorable conditions to obtain negative diatom replicas of good quality with features of 50 nm. Although this method can give very precise results producing high-resolution molds with all micro- and nanostructures replicated, we revealed some limitations regarding the size and morphology of the species used. These results indicate that large round and flat diatom species seem to be more suitable for the cast molding.

  3. More Fluorous Surface Modifier Makes it Less Oleophobic: Fluorinated-Siloxane Copolymer/PDMS Coatings (United States)

    Zhang, Wei; Zheng, Ying; Orsini, Lorenzo; Morelli, Andrea; Galli, Giancarlo; Chiellini, Emo; Carpenter, Everett E.; Wynne, Kenneth J.


    A copolyacrylate with semifluorinated and polydimethylsiloxane side chains (D5-3) was used as a surface modifier for a condensation cured PDMS coating. The decyl fluorous group is represented by “D”; “5” is a 5 kDa silicone, and “3” the mole ratio of fluorous to silicone side chain. Wetting behavior was assessed by dynamic contact angle (DCA) analysis using isopropanol, which differentiates silicone and fluorous wetting behavior. Interestingly, a maximum in surface oleophobicity was found at low D5-3 concentration (0.4 wt%). Higher concentrations result in decreased oleophobicity reflected in decreased contact angles. To understand this unexpected observation, dynamic light scattering (DLS) studies were initiated on a model system consisting of hydroxyl-terminated PDMS (18 kDa) containing varying amounts of D5-3. DLS revealed D5-3 aggregation as a function of temperature and concentration. A model is proposed by which D5-3 surface concentration is depleted via phase separation favoring D5-3 aggregation at concentrations >0.4 wt%, that is, the CMC. This model suggests increasing aggregate / micelle concentrations at increased D5-3 concentration. Bulk morphologies studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) support this model by showing increased aggregate concentrations with increased D5-3 >0.4 wt%. PMID:20000339

  4. More fluorous surface modifier makes it less oleophobic: fluorinated siloxane copolymer/PDMS coatings. (United States)

    Zhang, Wei; Zheng, Ying; Orsini, Lorenzo; Morelli, Andrea; Galli, Giancarlo; Chiellini, Emo; Carpenter, Everett E; Wynne, Kenneth J


    A copolyacrylate with semifluorinated and polydimethylsiloxane side chains (D5-3) was used as a surface modifier for a condensation-cured PDMS coating. The decyl fluorous group is represented by "D"; "5" is a 5 kDa silicone, and "3" is the mole ratio of fluorous to silicone side chains. Wetting behavior was assessed by dynamic contact angle (DCA) analysis using isopropanol, which differentiates silicone and fluorous wetting behavior. Interestingly, a maximum in surface oleophobicity was found at low D5-3 concentration (0.4 wt %). Higher concentrations result in decreased oleophobicity, as reflected in decreased contact angles. To understand this unexpected observation, dynamic light scattering (DLS) studies were initiated on a model system consisting of hydroxyl-terminated PDMS (18 kDa) containing varying amounts of D5-3. DLS revealed D5-3 aggregation to be a function of temperature and concentration. A model is proposed by which D5-3 surface concentration is depleted via phase separation favoring D5-3 aggregation at concentrations >0.4 wt %, that is, the cmc. This model suggests increasing aggregate/micelle concentrations at increased D5-3 concentration. Bulk morphologies studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) support this model by showing increased aggregate concentrations with increased D5-3 > 0.4 wt %.


    Institute of Scientific and Technical Information of China (English)



    Thin-film zeolite-filled silicone/PVDF composite membranes were fabricated by incorporating zeolite particles into PDMS(poly(dimethylsiloxane)) membranes.The morphology of zeolite particles and zeolite filled silicone composite membranes were characterized by SEM.The zeolite-filled PDMS/PVDF composite membranes were applied for the pervaporation of ethanol/water mixtures and showed higher flux compared with that reported in literatures.The effect of zeolite loading and Si/Al ratio of zeolite particles on...

  6. Investigation Into Accessible Surface Vinyl Concentrations of Nonstoichiometric PDMS Microspheres from Hydrosilylation Reactions and Their Further Crosslinking Reactions

    DEFF Research Database (Denmark)

    Ma, Baoguang; Hansen, Jens Henrik; Hvilsted, Søren;


    titration method, which is based on efficiently and covalently bonding mono-functional hydride to vinyl, is employed to determine surface vinyl concentration. The titration method exhibits good reproducibility in detection, thereby underlining its potential applicability as a general titration method...... for cured silicones. Vinyl functional PDMS microspheres are mixed with a hydride crosslinker and non-reactive silicone oil to create a system which allows for extensive crosslinking. Both visual observations and rheological studies show that a robust macroscopic PDMS elastomer is obtained upon crosslinking...

  7. Divergence structure of the statistical entropy of the Dirac field in a plane symmetry black hole geometry

    Institute of Scientific and Technical Information of China (English)

    Li Gu-Qiang


    The divergences at all levels for the statistical enytropy of a plane symmetry black hole arising from the massless Dirac field are considered using the brick-wall model. It is shown that if we ignore the usual contribution from the vacuum surrounding the system, then the statistical entropy consists of two paarts: one is the linearly divergent term which has the geometric character, the other consists of two logarithmically divergent terms which are not proportional to the surface area of the horizon. The entropy of the Dirac field on extremal plane symmetry spacetime background has higher divergence than usual.

  8. Evaluation and characterization of ceramic membranes based on Pdms/SiC containing phosphotungstic acid as electrolytes for PEM-FC; Avaliacao e caracterizacao de membranas ceramicas condutoras a base de PDMS/SiC contendo acido fosfotungstico como eletrolito para PEM-FC

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Marcelo de Oliveira; Guimaraes, Danilo Hansen; Boaventura Filho, Jaime Soares; Jose, Nadia Mamede [Universidade Federal da Bahia (IQ/UFBA), Salvador, BA (Brazil). Inst. de Quimica. Grupo de Energia e Ciencias dos Materiais; Barbosa, Diego Augusto Batista; Paschoal, Carlos William de Araujo [Universidade Federal do Maranhao (DF/UFMA), Sao Luis, MA (Brazil). Dept. de Fisica; Almeida, Rafael Mendonca; Tanaka, Auro Atsushi [Universidade Federal do Maranhao (DQ/UFMA), Sao Luis, MA (Brazil). Dept. de Quimica


    This work presents the development of membranes with potential use in Proton Exchange Fuel Cells (PEM-FC), consisting of hybrid materials based on poly(dimethylsiloxane), crosslinked with tetraethyl orthosilicate (TEOS), and reinforced with silicon carbide and phosphotungstic acid. The membrane series PDMS/TEOS/SiC/PWA were prepared by the reaction of PDMS and TEOS, 70/30% proportions in mass, catalyzed by dibutyltin dilaurate. SiC was incorporated in a 25% proportion, and PWA in varied proportions (5, 10, 15 and 20%), by weight. The membranes were characterized by Thermo-Gravimetric Analysis (TGA), X-ray Diffraction, Scanning Electron Microscopy and impedance spectroscopy. SiC and PWA addition to the membrane increased both structure organization and material crystallinity. The insertion of PWA provided an increase in the conductivity. However, maximum conductivity was obtained with concentration levels above 10%. The insertion of SiC associated with the PWA did not influence the conductivity for concentrations between 10 and 20%. (author)

  9. Black hole accretion discs

    CERN Document Server

    Lasota, Jean-Pierre


    This is an introduction to models of accretion discs around black holes. After a presentation of the non-relativistic equations describing the structure and evolution of geometrically thin accretion discs we discuss their steady-state solutions and compare them to observation. Next we describe in detail the thermal-viscous disc instability model and its application to dwarf novae for which it was designed and its X-ray irradiated-disc version which explains the soft X--ray transients, i.e. outbursting black-hole low-mass X-ray binaries. We then turn to the role of advection in accretion flow onto black holes illustrating its action and importance with a toy model describing both ADAFs and slim discs. We conclude with a presentation of the general-relativistic formalism describing accretion discs in the Kerr space-time.

  10. Quasistars: Accreting black holes inside massive envelopes

    CERN Document Server

    Begelman, Mitchell C; Armitage, Philip J


    We study the structure and evolution of "quasistars," accreting black holes embedded within massive hydrostatic gaseous envelopes. These configurations may model the early growth of supermassive black hole seeds. The accretion rate onto the black hole adjusts so that the luminosity carried by the convective envelope equals the Eddington limit for the total mass. This greatly exceeds the Eddington limit for the black hole mass alone, leading to rapid growth of the black hole. We use analytic models and numerical stellar structure calculations to study the structure and evolution of quasistars. We derive analytically the scaling of the photospheric temperature with the black hole mass and envelope mass, and show that it decreases with time as the black hole mass increases. Once the photospheric temperature becomes lower than 10000 K, the photospheric opacity drops precipitously and the photospheric temperature hits a limiting value, analogous to the Hayashi track for red giants and protostars, below which no hy...

  11. Investigation of isomeric flavanol structures in black tea thearubigins using ultraperformance liquid chromatography coupled to hybrid quadrupole/ion mobility/time of flight mass spectrometry. (United States)

    Yassin, Ghada H; Grun, Christian; Koek, Jean H; Assaf, Khaleel I; Kuhnert, Nikolai


    Ultra performance liquid chromatography (UPLC) when coupled to ion mobility (IMS)/orthogonal acceleration time of flight mass spectrometry is a suitable technique for analyzing complex mixtures such as the black tea thearubigins. With the aid of this advanced instrumental analysis, we were able to separate and identify different isomeric components in the complex mixture which could previously not be differentiated by a conventional high performance liquid chromatography/tandem mass spectrometry. In this study, the difference between isomeric structures theasinensins, proanthocyanidins B-type and rutin (quercetin-3O-rutinoside) were studied, and these are present abundantly in many botanical sources. The differentiation between these structures was accomplished according to their acquired mobility drift times differing from the traditional investigations in mass spectrometry, where calculation of theoretical collisional cross sections allowed assignment of the individual isomeric structures. The present work demonstrates UPLC-IMS-MS as an efficient technology for isolating and separating isobaric and isomeric structures existing in complex mixtures discriminating between them according to their characteristic fragment ions and mobility drift times. Therefore, a rational assignment of isomeric structures in many phenolic secondary metabolites based on the ion mobility data might be useful in mass spectrometry-based structure analysis in the future.

  12. Changes in composition, structure and aboveground biomass over seventy-six years (1930-2006) in the Black Rock Forest, Hudson Highlands, southeastern New York State. (United States)

    Schuster, W S F; Griffin, K L; Roth, H; Turnbull, M H; Whitehead, D; Tissue, D T


    We sought to quantify changes in tree species composition, forest structure and aboveground forest biomass (AGB) over 76 years (1930-2006) in the deciduous Black Rock Forest in southeastern New York, USA. We used data from periodic forest inventories, published floras and a set of eight long-term plots, along with species-specific allometric equations to estimate AGB and carbon content. Between the early 1930s and 2000, three species were extirpated from the forest (American elm (Ulmus americana L.), paper birch (Betula papyrifera Marsh.) and black spruce (Picea mariana (nigra) (Mill.) BSP)) and seven species invaded the forest (non-natives tree-of-heaven (Ailanthus altissima (Mill.) Swingle) and white poplar (Populus alba L.) and native, generally southerly distributed, southern catalpa (Catalpa bignonioides Walt.), cockspur hawthorn (Crataegus crus-galli L.), red mulberry (Morus rubra L.), eastern cottonwood (Populus deltoides Bartr.) and slippery elm (Ulmus rubra Muhl.)). Forest canopy was dominated by red oak and chestnut oak, but the understory tree community changed substantially from mixed oak-maple to red maple-black birch. Density decreased from an average of 1500 to 735 trees ha(-1), whereas basal area doubled from less than 15 m(2) ha(-1) to almost 30 m(2) ha(-1) by 2000. Forest-wide mean AGB from inventory data increased from about 71 Mg ha(-1) in 1930 to about 145 Mg ha(-1) in 1985, and mean AGB on the long-term plots increased from 75 Mg ha(-1) in 1936 to 218 Mg ha(-1) in 1998. Over 76 years, red oak (Quercus rubra L.) canopy trees stored carbon at about twice the rate of similar-sized canopy trees of other species. However, there has been a significant loss of live tree biomass as a result of canopy tree mortality since 1999. Important constraints on long-term biomass increment have included insect outbreaks and droughts.

  13. Contact Mechanics of UV/Ozone-Treated PDMS by AFM and JKR Testing: Mechanical Performance from Nano- to Micrometer Length Scales

    NARCIS (Netherlands)

    Song, Jing; Tranchida, Davide; Vancso, G. Julius


    The Young’s modulus of cross-linked poly(dimethylsiloxane) (PDMS) surface was quantitatively investigated as a function of UV/ozone treatment time across different length scales. An AFM was used to probe PDMS surface mechanical properties at the nanometer length scale. The Young’s modulus of each sa

  14. PDMS-modified poly(styrene-alt-maleic anhydride)s as water-borne coatings based on surfactant-free latexes

    NARCIS (Netherlands)

    Gunbas, I.D.; Wouters, M.E.L.; Benthem, R.A.T.M. van; Koning, C.E.; Noordover, B.A.J.


    In this work, two series of PDMS-modified poly(styrene-alt-maleic anhydride)s (PSMA) were prepared by the partial imidization of their anhydride groups with mono-functional, amine-terminated polydimethyl siloxanes (PDMS-NH2) with two different molecular weights. Subsequently, surfactant-free artific

  15. The Central Engine Structure of 3C120: Evidence for a Retrograde Black Hole or a Refilling Accretion Disk (United States)

    Cowperthwaite, Philip S.; Reynolds, Christopher S.


    The broad-line radio galaxy 3C120 is a powerful source of both X-ray and radio emission including superluminal jet outflows. We report on our reanalysis of 160 ks of Suzaku data taken in 2006, previously examined by Kataoka et al. Spectral fits to the X-ray Imaging Spectrometer and Hard X-ray Detector/positive intrinsic negative data over a range of 0.7-45 keV reveal a well-defined iron K line complex with a narrow Kα core and relativistically broadened features consistent with emission from the inner regions of the accretion disk. Furthermore, the inner region of the disk appears to be truncated, with an inner radius of r in = 11.7+3.5 - 5.2 rg . If we assume that fluorescent iron line features terminate at the inner-most stable circular orbit (ISCO), then we measure a black hole spin of \\hat{a} black hole (\\hat{a} > 0.8) can be ruled out at the 99% confidence level. Alternatively, the disk may be truncated well outside of the ISCO of a rapid prograde hole. The most compelling scenario is the possibility that the inner regions of the disk were destroyed/ejected by catastrophic instabilities just prior to the time these observations were made.

  16. Implementing black hole as efficient power plant

    CERN Document Server

    Wei, Shao-Wen


    Treating the black hole molecules as working substance and considering its phase structure, we study the black hole heat engine by a charged anti-de Sitter black hole. In the reduced temperature-entropy chart, it is found that the work, heat, and efficiency of the engine are independent of the black hole charge. Applying the Rankine cycle with or without a back pressure mechanism to the black hole heat engine, the efficiency is numerically solved. The result shows that the black hole engine working along the Rankine cycle with a back pressure mechanism has a higher efficiency. This provides a novel and efficient mechanism to produce the useful mechanical work with black hole, and such heat engine may act as a possible energy source for the high energy astrophysical phenomena near the black hole.

  17. μ-Biomimetic flow-sensors--introducing light-guiding PDMS structures into MEMS. (United States)

    Herzog, Hendrik; Klein, Adrian; Bleckmann, Horst; Holik, Peter; Schmitz, Sam; Siebke, Georg; Tätzner, Simon; Lacher, Manfred; Steltenkamp, Siegfried


    In the area of biomimetics, engineers use inspiration from natural systems to develop technical devices, such as sensors. One example is the lateral line system of fish. It is a mechanoreceptive system consisting of up to several thousand individual sensors called neuromasts, which enable fish to sense prey, predators, or conspecifics. So far, the small size and high sensitivity of the lateral line is unmatched by man-made sensor devices. Here, we describe an artificial lateral line system based on an optical detection principle. We developed artificial canal neuromasts using MEMS technology including thick film techniques. In this work, we describe the MEMS fabrication and characterize a sensor prototype. Our sensor consists of a silicon chip, a housing, and an electronic circuit. We demonstrate the functionality of our μ-biomimetic flow sensor by analyzing its response to constant water flow and flow fluctuations. Furthermore, we discuss the sensor robustness and sensitivity of our sensor and its suitability for industrial and medical applications. In sum, our sensor can be used for many tasks, e.g. for monitoring fluid flow in medical applications, for detecting leakages in tap water systems or for air and gas flow measurements. Finally, our flow sensor can even be used to improve current knowledge about the functional significance of the fish lateral line.

  18. String-Corrected Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    Hubeny, Veronika; Maloney, Alexander; Rangamani, Mukund


    We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect -- the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive! The magnitude of this effect is related to the size of the compactification manifold.

  19. A preliminary factor analytic investigation into the firstorder factor structure of the Fifteen Factor Plus (15FQ+ on a sample of Black South African managers

    Directory of Open Access Journals (Sweden)

    Seretse Moyo


    Full Text Available Orientation: The Fifteen Factor Questionnaire Plus (15FQ+ is a prominent personality questionnaire that organisations frequently use in personnel selection in South Africa.Research purpose: The primary objective of this study was to undertake a factor analytic investigation of the first-order factor structure of the 15FQ+.Motivation for the study: The construct validity of the 15FQ+, as a measure of personality, is necessary even though it is insufficient to justify its use in personnel selection.Research design, approach and method: The researchers evaluated the fit of the measurement model, which the structure and scoring key of the 15FQ+ implies, in a quantitative study that used an ex post facto correlation design through structural equation modelling. They conducted a secondary data analysis. They selected a sample of 241 Black South African managers from a large 15FQ+ database.Main findings: The researchers found good measurement model fit. The measurement model parameter estimates were worrying. The magnitude of the estimated model parameters suggests that the items generally do not reflect the latent personality dimensions the designers intended them to with a great degree of precision. The items are reasonably noisy measures of the latent variables they represent.Practical/managerial implications: Organisations should use the 15FQ+ carefully on Black South African managers until further local research evidence becomes available.Contribution/value-add: The study is a catalyst to trigger the necessary additional research we need to establish convincingly the psychometric credentials of the 15FQ+ as a valuable assessment tool in South Africa.

  20. A new water absorbable mechanical Epidermal skin equivalent: the combination of hydrophobic PDMS and hydrophilic PVA hydrogel. (United States)

    Morales-Hurtado, M; Zeng, X; Gonzalez-Rodriguez, P; Ten Elshof, J E; van der Heide, E


    Research on human skin interactions with healthcare and lifestyle products is a topic continuously attracting scientific studies over the past years. It is possible to evaluate skin mechanical properties based on human or animal experimentation, yet in addition to possible ethical issues, these samples are hard to obtain, expensive and give rise to highly variable results. Therefore, the design of a skin equivalent is essential. This paper describes the design and characterization of a new Epidermal Skin Equivalent (ESE). The material resembles the properties of epidermis and is a first approach to mimic the mechanical properties of the human skin structure, variable with the length scale. The ESE is based on a mixture of Polydimethyl Siloxane (PDMS) and Polyvinyl Alcohol (PVA) hydrogel cross-linked with Glutaraldehyde (GA). It was chemically characterized by XPS and FTIR measurements and its cross section was observed by macroscopy and cryoSEM. Confocal Microscope analysis on the surface of the ESE showed an arithmetic roughness (Ra) between 14-16 μm and contact angle (CA) values between 50-60°, both of which are close to the values of in vivo human skins reported in the literature. The Equilibrium Water Content (ECW) was around 33.8% and Thermo Gravimetric Analysis (TGA) confirmed the composition of the ESE samples. Moreover, the mechanical performance was determined by indentation tests and Dynamo Thermo Mechanical Analysis (DTMA) shear measurements. The indentation results were in good agreement with that of the target epidermis reported in the literature with an elastic modulus between 0.1-1.5 MPa and it showed dependency on the water content. According to the DTMA measurements, the ESE exhibits a viscoelastic behavior, with a shear modulus between 1-2.5MPa variable with temperature, frequency and the hydration of the samples.

  1. Towards black-box calculations of tunneling splittings obtained from vibrational structure methods based on normal coordinates. (United States)

    Neff, Michael; Rauhut, Guntram


    Multidimensional potential energy surfaces obtained from explicitly correlated coupled-cluster calculations and further corrections for high-order correlation contributions, scalar relativistic effects and core-correlation energy contributions were generated in a fully automated fashion for the double-minimum benchmark systems OH3(+) and NH3. The black-box generation of the potentials is based on normal coordinates, which were used in the underlying multimode expansions of the potentials and the μ-tensor within the Watson operator. Normal coordinates are not the optimal choice for describing double-minimum potentials and the question remains if they can be used for accurate calculations at all. However, their unique definition is an appealing feature, which removes remaining errors in truncated potential expansions arising from different choices of curvilinear coordinate systems. Fully automated calculations are presented, which demonstrate, that the proposed scheme allows for the determination of energy levels and tunneling splittings as a routine application.

  2. Poly(Dimethylsiloxane) (PDMS) Affects Gene Expression in PC12 Cells Differentiating into Neuronal-Like Cells

    DEFF Research Database (Denmark)

    Lopacinska, Joanna M.; Emnéus, Jenny; Dufva, Martin


    Introduction: Microfluidics systems usually consist of materials like PMMA - poly(methyl methacrylate) and PDMS - poly(dimethylsiloxane) and not polystyrene (PS), which is usually used for cell culture. Cellular and molecular responses in cells grown on PS are well characterized due to decades...

  3. Effects of metabolic pathway precursors and polydimethylsiloxane (PDMS) on poly-(gamma)-glutamic acid production by Bacillus subtilis BL53. (United States)

    de Cesaro, Alessandra; da Silva, Suse Botelho; Ayub, Marco Antônio Záchia


    The aims of this study were to evaluate the effects of the addition of metabolic precursors and polydimethylsiloxane (PDMS) as an oxygen carrier to cultures of Bacillus subtilis BL53 during the production of γ-PGA. Kinetics analyses of cultivations of different media showed that B. subtilis BL53 is an exogenous glutamic acid-dependent strain. When the metabolic pathway precursors of γ-PGA synthesis, L-glutamine and a-ketoglutaric acid, were added to the culture medium, production of the biopolymer was increased by 20 % considering the medium without these precursors. The addition of 10 % of the oxygen carrier PDMS to cultures caused a two-fold increase in the volumetric oxygen mass transfer coefficient (kLa), improving γ-PGA production and productivity. Finally, bioreactor cultures of B. subtilis BL53 adopting the combination of optimized medium E, added of glutamine, α-ketoglutaric acid, and PDMS, showed a productivity of 1 g L(-1) h(-1) of g-PGA after only 24 h of cultivation. Results of this study suggest that the use of metabolic pathway precursors glutamine and a-ketolgutaric acid, combined with the addition of PDMS as an oxygen carrier in bioreactors, can improve γ-PGA production and productivity by Bacillus strains .

  4. The effect of carbon nanotubes and titanium dioxide incorporated in PDMS on biofilm community composition and subsequent mussel plantigrade settlement. (United States)

    Yang, Jin-Long; Li, Yi-Feng; Guo, Xing-Pan; Liang, Xiao; Xu, Yue-Feng; Ding, De-Wen; Bao, Wei-Yang; Dobretsov, Sergey


    This study investigated the effect of carbon nanotubes (CNTs) and titanium dioxide (TiO2) incorporated in PDMS on biofilm formation and plantigrade settlement of Mytilus coruscus. TiO2 increased bacterial density, and CNTs also increased bacterial density but reduced diatom density in biofilms after 28 days. Further analysis was conducted between bacterial communities on glass, PDMS, CNTs (0.5 wt%) and TiO2 (7.5 wt%). ANOSIM analysis revealed significant differences (R > 0.9) between seven, 14, 21 and 28 day-old bacterial communities. MiSeq sequencing showed that CNTs and TiO2 impacted the composition of 28 day-old bacterial communities by increasing the abundance of Proteobacteria and decreasing the abundance of Bacteroidetes. The maximum decreased settlement rate in 28 day-old biofilms on CNTs and TiO2 was > 50% in comparison to those on glass and PDMS. Thus, CNTs and TiO2 incorporated in PDMS altered the biomass and community composition of biofilms, and subsequently decreased mussel settlement.


    Pervaporation is potentially a cost-effective means of recovering biofuels, such as ethanol, from biomass fermentation broths for small- to medium-scale applications (~2 - 20 million liters per year). Hydrophobic zeolite-filled polydimethylsiloxane (PDMS) membranes have been sho...

  6. Rapid fabrication of microfluidic polymer electrolyte membrane fuel cell in PDMS by surface patterning of perfluorinated ion-exchange resin

    Energy Technology Data Exchange (ETDEWEB)

    Song, Yong-Ak; Han, Jongyoon [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Department of Biological Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Batista, Candy [Roxbury Community College, 1234 Columbus Ave., Roxbury Crossing, MA 02120 (United States); Sarpeshkar, Rahul [Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States)


    In this paper we demonstrate a simple and rapid fabrication method for a microfluidic polymer electrolyte membrane (PEM) fuel cell using polydimethylsiloxane (PDMS), which has become the de facto standard material in BioMEMS. Instead of integrating a Nafion sheet film between two layers of a PDMS device in a traditional ''sandwich format,'' we pattern a perfluorinated ion-exchange resin such as a Nafion resin on a glass substrate using a reversibly bonded PDMS microchannel to generate an ion-selective membrane between the fuel-cell electrodes. After this patterning step, the assembly of the microfluidic fuel cell is accomplished by simple oxygen plasma bonding between the PDMS chip and the glass substrate. In an example implementation, the planar PEM microfluidic fuel cell generates an open circuit voltage of 600-800 mV and delivers a maximum current output of nearly 4 {mu}A. To enhance the power output of the fuel cell we utilize self-assembled colloidal arrays as a support matrix for the Nafion resin. Such arrays allow us to increase the thickness of the ion-selective membrane to 20 {mu}m and increase the current output by 166%. Our novel fabrication method enables rapid prototyping of microfluidic fuel cells to study various ion-exchange resins for the polymer electrolyte membrane. Our work will facilitate the development of miniature, implantable, on-chip power sources for biomedical applications. (author)

  7. Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles. (United States)

    Wei, Xi; Syed, Abeer; Mao, Pan; Han, Jongyoon; Song, Yong-Ak


    Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

  8. Applications of PDMS partitioning methods in the study of biodegradation of pyrene in the

    DEFF Research Database (Denmark)

    Tejeda-Agredano, MC; Gouliarmou, Varvara; Ortega-Calvo, JJ

    to the physical association of bacteria and HS. Here, we propose the use of partitioning techniques using poly(dimethylsiloxane) (PDMS) to study the effect of binding of pyrene to a dissolved humic acid isolated from soil on biodegradation of this PAH by a representative soil bacterium. The application...... of these techniques in biodegradation studies may solve many questions about enhancements in diffusive mass transfer, in capacity/speciation and in dissolution. Therefore, our study may provide new insights into the effects of HS on microbial degradation of polycyclic aromatic hydrocarbons (PAHs).......Although there are reports on the inhibition of anthropogenic organic chemicals biodegradation due to binding to dissolved humic substances (HS), there is an increasing body of evidence pointing to an enhancing effect in the case of hydrophobic chemicals, like pyrene. The addition of humic...

  9. Preparation of PDMS-coated microspheres by sol-gel method for sorptive extraction of PAHs

    Institute of Scientific and Technical Information of China (English)

    Chang Guang Yang; Xiang Juan Ji; Xiao Zheng Lan


    In this paper, a novel SPME mode, PDMS-coated solid glass microspheres (SGMs), were prepared by sol-gel method. Using homemade thermal desorption unit coupled with CGC-FID, six PAHs as model analytes, the performance of the new mode was characterized. The new extractive phase exhibited high thermal stability and satisfactory extraction capability. The detection limits were 0.01-0.045 ng/mL, and the linearity was from 0.5 ng/mL to 96 ng/mL. The R.S.D.s of repeatability for retention time and peak area were all within 0.074% and 6.7%, respectively. The recoveries of the PAHs were 78-127% from the sarnples taken from river water.

  10. Multi-channel peristaltic pump for microfluidic applications featuring monolithic PDMS inlay

    DEFF Research Database (Denmark)

    Skafte-Pedersen, Peder; Sabourin, David; Dufva, Martin


    The design, fabrication and characterization of a miniaturized, mechanically-actuated 12-channel peristaltic pump for microfluidic applications and built from simple, low-cost materials and fabrication methods is presented. Two pump configurations are tested, including one which reduces pulsating...... flow. Both use a monolithic PDMS pumping inlay featuring three-dimensional geometries favourable to pumping applications and 12 wholly integrated circular channels. Flow rates in the sub-µL min-1 to µL min-1 range were obtained. Channel-to-channel flow rate variability was comparable to a commercial...... pumping system at lower flow rates. The small footprint, 40 mm by 80 mm, of the micropump renders it portable, and allows its use on microscope stages adjacent to microfluidic devices, thus reducing system dead volumes. The micropump's design allows potential use in remote and resource-limited locations...

  11. Comparative analysis of fabrication methods for achieving rounded microchannels in PDMS (United States)

    Bartlett, Nicholas W.; Wood, Robert J.


    Many microfluidic applications demand control over channel cross-sectional geometry. In particular, rounded microchannels are essential to the function of microfluidic valves, which have played an integral part in the success of microfluidics over the past fifteen years. Here we investigate the relative strengths and weaknesses of different strategies for fabricating rounded microchannels in PDMS, systematically examining five common strategies. We consider the appropriateness of the fabrication strategies for microchannels of differing sizes and aspect ratios, and evaluate these various strategies on a number of metrics ranging from microchannel resolution to fabrication difficulty. We discuss the merits of the different strategies for a range of applications, and make recommendations on which strategy to use based on the driving constraints of the device.

  12. Patterned Fibers Embedded Microfluidic Chips Based on PLA and PDMS for Ag Nanoparticle Safety Testing

    Directory of Open Access Journals (Sweden)

    Yaowen Liu


    Full Text Available A new method to integrate poly-dl-lactide (PLA patterned electrospun fibers with a polydimethylsiloxane (PDMS microfluidic chip was successfully developed via lithography. Hepatocyte behavior under static and dynamic conditions was investigated. Immunohistochemical analyses indicated good hepatocyte survival under the dynamic culture system with effective hepatocyte spheroid formation in the patterned microfluidic chip vs. static culture conditions and tissue culture plate (TCP. In particular, hepatocytes seeded in this microfluidic chip under a flow rate of 10 μL/min could re-establish hepatocyte polarity to support biliary excretion and were able to maintain high levels of albumin and urea secretion over 15 days. Furthermore, the optimized system could produce sensitive and consistent responses to nano-Ag-induced hepatotoxicity during culture. Thus, this microfluidic chip device provides a new means of fabricating complex liver tissue-engineered scaffolds, and may be of considerable utility in the toxicity screening of nanoparticles.

  13. Confocal restricted-height imaging of suspension cells (CRISC) in a PDMS microdevice during apoptosis. (United States)

    Muñoz-Pinedo, Cristina; Green, Douglas R; van den Berg, Albert


    We have monitored and imaged cell death induced in human leukemic U937 cells over time using three-color confocal imaging. Three different apoptotic inducers, anti-Fas, TNF-alpha and Etoposide were used. Individual cascaded events such as loss of mitochondrial transmembrane potential, exposure of phosphatidyl-serine, membrane blebbing and permeabilization of the cell membrane have been observed in real time with different individual cells. From the results, an interesting heterogeneicity in the apoptotic phenotype has been observed. The CRISC method is easy to use and provides biologist with a powerful additional tool to study in real-time processes of several hours of duration such as apoptosis. We predict that the period of cell viability obtained after protein coating of the PDMS devices (>80 h) will also allow monitoring of other biological processes of longer duration or long onset time, such as mitosis, phagocytosis and differentiation.

  14. A PDMS-Based Cylindrical Hybrid Lens for Enhanced Fluorescence Detection in Microfluidic Systems

    Directory of Open Access Journals (Sweden)

    Bor-Shyh Lin


    Full Text Available Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of fluorescence detection. However, these strategies encounter common issues of complex manufacturing processes and high costs. In this study; a miniature, cylindrical and hybrid lens made of polydimethylsiloxane (PDMS to improve the fluorescence detection in microfluidic systems is proposed. The hybrid lens integrates a laser focusing lens and a fluorescence collecting lens to achieve dual functions and simplify optical setup. Moreover, PDMS has advantages of low-cost and straightforward fabrication compared with conventional optical components. The performance of the proposed lens is first examined with two fluorescent dyes and the results show that the lens provides satisfactory enhancement for fluorescence detection of Rhodamine 6G and Nile Red. The overall increments in collected fluorescence signal and detection sensitivity are more than 220% of those without lens, and the detection limits of Rhodamine 6G and Nile red are lowered to 0.01 μg/mL and 0.05 μg/mL, respectively. The hybrid lens is further applied to the detection of Nile red-labeled Chlorella vulgaris cells and it increases both signal intensity and detection sensitivity by more than 520%. The proposed hybrid lens also dramatically reduces the variation in detected signal caused by the deviation in incident angle of excitation light.

  15. A PDMS-based cylindrical hybrid lens for enhanced fluorescence detection in microfluidic systems. (United States)

    Lin, Bor-Shyh; Yang, Yu-Ching; Ho, Chong-Yi; Yang, Han-Yu; Wang, Hsiang-Yu


    Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of fluorescence detection. However, these strategies encounter common issues of complex manufacturing processes and high costs. In this study; a miniature, cylindrical and hybrid lens made of polydimethylsiloxane (PDMS) to improve the fluorescence detection in microfluidic systems is proposed. The hybrid lens integrates a laser focusing lens and a fluorescence collecting lens to achieve dual functions and simplify optical setup. Moreover, PDMS has advantages of low-cost and straightforward fabrication compared with conventional optical components. The performance of the proposed lens is first examined with two fluorescent dyes and the results show that the lens provides satisfactory enhancement for fluorescence detection of Rhodamine 6G and Nile Red. The overall increments in collected fluorescence signal and detection sensitivity are more than 220% of those without lens, and the detection limits of Rhodamine 6G and Nile red are lowered to 0.01 μg/mL and 0.05 μg/mL, respectively. The hybrid lens is further applied to the detection of Nile red-labeled Chlorella vulgaris cells and it increases both signal intensity and detection sensitivity by more than 520%. The proposed hybrid lens also dramatically reduces the variation in detected signal caused by the deviation in incident angle of excitation light.

  16. A multi-scale PDMS fabrication strategy to bridge the size mismatch between integrated circuits and microfluidics. (United States)

    Muluneh, Melaku; Issadore, David


    In recent years there has been great progress harnessing the small-feature size and programmability of integrated circuits (ICs) for biological applications, by building microfluidics directly on top of ICs. However, a major hurdle to the further development of this technology is the inherent size-mismatch between ICs (~mm) and microfluidic chips (~cm). Increasing the area of the ICs to match the size of the microfluidic chip, as has often been done in previous studies, leads to a waste of valuable space on the IC and an increase in fabrication cost (>100×). To address this challenge, we have developed a three dimensional PDMS chip that can straddle multiple length scales of hybrid IC/microfluidic chips. This approach allows millimeter-scale ICs, with no post-processing, to be integrated into a centimeter-sized PDMS chip. To fabricate this PDMS chip we use a combination of soft-lithography and laser micromachining. Soft lithography was used to define micrometer-scale fluid channels directly on the surface of the IC, allowing fluid to be controlled with high accuracy and brought into close proximity to sensors for highly sensitive measurements. Laser micromachining was used to create ~50 μm vias to connect these molded PDMS channels to a larger PDMS chip, which can connect multiple ICs and house fluid connections to the outside world. To demonstrate the utility of this approach, we built and demonstrated an in-flow magnetic cytometer that consisted of a 5 × 5 cm(2) microfluidic chip that incorporated a commercial 565 × 1145 μm(2) IC with a GMR sensing circuit. We additionally demonstrated the modularity of this approach by building a chip that incorporated two of these GMR chips connected in series.

  17. Community Composition and Structure of Soil Macro-Arthropods Under Agricultural Land Uses in the Black Soil Region of Jilin Province, China

    Institute of Scientific and Technical Information of China (English)

    WU Dong-hui; ZHANG Bai; CHEN Peng


    Soil macro-arthropods in the black soil region in Jilin Province of China were investigated with the emphasis laid on the species richness and abundance in relation to the types of land-use, i.e., farm yard, farm land and Three-North Forest Shelter Belt. Soil macro-arthropods were hand-sorted in the field. A total of 2 357 soil macro-arthropod individuals was captured and fell into 70 families. The results suggested that type of land use affected the species richness and abundance of soil macro-arthropods. Agricultural practices had a strong impact on the soil macro-arthropods community, the conventional cultivations changed the vertical structure of macro-arthropods in the soil profile, and improved the richness and abundance of macro-arthropods in the lower soil layers especially in July. The results also showed that different groups of soil macro-arthropods had various responses to land use changes.

  18. Cosmic Intelligence and Black Holes

    CERN Document Server

    Lefebvre, V A; Lefebvre, Vladimir A.; Efremov, Yuri N.


    The paper is devoted to a new direction in SETI. After a general discussion of the field, the authors put forth the hypothesis that the black holes may serve as a physical substratum for intelligent beings. This hypothesis is based on four parallels between the brain-psyche system, on the one hand, and black holes, on the other. (1) The descriptions of brain and psyche, in the system brain-psyche, are complementary to each other, as descriptions by internal and external observers of a black hole in Susskind-t'Hooft's schema. (2) There is an aspect of the inner structure of a black hole in Kerr's model of the rotating black hole that is isomorphic to the structure of the human subjective domain in the psychological model of reflexion. (3) Both black holes and the brain-psyche system have a facet which can be represented using thermodynamic concepts. (4) The brain lends itself to a holographic description; as has been recently demonstrated by Susskind, black holes can also be described holographically. The auth...

  19. Orbital resonances around black holes. (United States)

    Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja


    We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.

  20. Black Holes: A Traveler's Guide (United States)

    Pickover, Clifford A.


    BLACK HOLES A TRAVELER'S GUIDE Clifford Pickover's inventive and entertaining excursion beyond the curves of space and time. "I've enjoyed Clifford Pickover's earlier books . . . now he has ventured into the exploration of black holes. All would-be tourists are strongly advised to read his traveler's guide." -Arthur C. Clarke. "Many books have been written about black holes, but none surpass this one in arousing emotions of awe and wonder towards the mysterious structure of the universe." -Martin Gardner. "Bucky Fuller thought big. Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." -Wired. "The book is fun, zany, in-your-face, and refreshingly addictive." -Times Higher Education Supplement.

  1. Investigations on the Structure Tectonics, Geophysics, Geochemistry, and Hydrocarbon Potential of the Black Mesa Basin, Northeastern Arizona

    Energy Technology Data Exchange (ETDEWEB)

    Barker, Colin; Carroll, Herbert; Erickson, Richard; George, Steve; Guo, Genliang; Reeves,T.K.; Sharma, Bijon; Szpakiewicz, Michael; Volk, Len


    The U.S. Department of Energy (DOE) has instituted a basin-analysis study program to encourage drilling in underexplored and unexplored areas and increase discovery rates for hydrocarbons by independent oil companies within the continental United States. The work is being performed at the DOE's National Institute for Petroleum and Energy Research (NIPER) in Bartlesville, Oklahoma, by the Exploration and Drilling Group within BDM-Oklahoma (BDM), the manager of the facility for DOE. Several low-activity areas in the Mid-Continent, west, and southwest were considered for the initial study area (Reeves and Carroll 1994a). The Black Mesa region in northwestern Arizona is shown on the U.S. Geological Survey 1995 oil and gas map of the United States as an undrilled area, adapted from Takahashi and Gautier 1995. This basin was selected by DOE s the site for the initial NIPER-BDM survey to develop prospects within the Lower-48 states (Reeves and Carroll 1994b).

  2. black cat

    Institute of Scientific and Technical Information of China (English)



    The black cat is a masterpiece of short fiction of Poe. He successfully solved the problem of creating of the horror effect by using scene description, symbol, repetition and first-person narrative methods. And created a complete and unified mysterious terror, achieved the effect of shocking. This paper aims to discuss the mystery in-depth and to enrich the research system in Poe’s novels.

  3. Microwave irradiation on carbon black: Studies on the transformation of particles into nano-balls, nano-sticks and nano-onion like structures (United States)

    Asokan, Vijayshankar; Venkatachalapathy, Vishnukanthan; Rajavel, Krishnamoorthy; Madsen, Dorte Nørgaard


    The solid-state transformation behavior of carbon black (CB) nanoparticles after irradiated with microwave energy was studied with and without influence of a metal catalyst. The CB sample was exposed to microwave radiation at power of 900 W from the oven and collected after 15 min and after 30 min and 45 min of irradiation. The samples were characterized using X-ray diffraction measurements, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM) and thermogravimetric analysis. Characterization of the samples prepared without catalyst shows that microwave irradiation can transform CB nanoparticles into nano-balls and nano-stick like structures. While nanoballs of almost 300-500 nm diameter are visible in all the samples irrespective of microwave irradiation time, amorphous nano-stick like structure are present only in the sample collected after 30 min of microwave irradiation. CB irradiated together with a metal catalyst resulted in metal-encapsulated onion like structures with perfectly arranged graphene layers.


    Directory of Open Access Journals (Sweden)

    Salenko E. A.


    Full Text Available This article describes the results of programming of a yield of winter wheat grain on quality and productivity of winter wheat in the conditions of teaching and experimental farm of Stavropol upland. There were given the weather conditions during the research, their influence on the formation of the structure yield and quality of winter wheat. We have presented an analysis and a comparative evaluation of the structure of the winter wheat crop, including a variety of quantitative traits: the length of the stem and ear, number of grains per ear, mass of one ear, weight of 1000 grains, tillering and overall productivity yields. This scientific article describes the technical requirements to the content: protein, gluten, vitreous, the DCO, the class of grain. In general, the results of 4-year data on leached black soils of Stavropol Upland were the largest and the best indicators on the structure of winter wheat yield and grain quality, as they were obtained with the introduction of the planned dose N126R80K72 harvest of 6.0 t/ha according to the method of calculation by V.V. Ageev, planned yield levels 5.0 and 6.0 t / ha have been achieved, the accuracy of programming (99% was obtained by calculating the doses of fertilizers by the method of V. V. Ageev

  5. The renaissance of black phosphorus (United States)

    Ling, Xi; Wang, Han; Huang, Shengxi; Xia, Fengnian; Dresselhaus, Mildred S.


    One hundred years after its first successful synthesis in the bulk form in 1914, black phosphorus (black P) was recently rediscovered from the perspective of a 2D layered material, attracting tremendous interest from condensed matter physicists, chemists, semiconductor device engineers, and material scientists. Similar to graphite and transition metal dichalcogenides (TMDs), black P has a layered structure but with a unique puckered single-layer geometry. Because the direct electronic band gap of thin film black P can be varied from 0.3 eV to around 2 eV, depending on its film thickness, and because of its high carrier mobility and anisotropic in-plane properties, black P is promising for novel applications in nanoelectronics and nanophotonics different from graphene and TMDs. Black P as a nanomaterial has already attracted much attention from researchers within the past year. Here, we offer our opinions on this emerging material with the goal of motivating and inspiring fellow researchers in the 2D materials community and the broad readership of PNAS to discuss and contribute to this exciting new field. We also give our perspectives on future 2D and thin film black P research directions, aiming to assist researchers coming from a variety of disciplines who are desirous of working in this exciting research field.

  6. Abrasion and fatigue resistance of PDMS containing multiblock polyurethanes after accelerated water exposure at elevated temperature. (United States)

    Chaffin, Kimberly A; Wilson, Charles L; Himes, Adam K; Dawson, James W; Haddad, Tarek D; Buckalew, Adam J; Miller, Jennifer P; Untereker, Darrel F; Simha, Narendra K


    Segmented polyurethane multiblock polymers containing polydimethylsiloxane and polyether soft segments form tough and easily processed thermoplastic elastomers (PDMS-urethanes). Two commercially available examples, PurSil 35 (denoted as P35) and Elast-Eon E2A (denoted as E2A), were evaluated for abrasion and fatigue resistance after immersion in 85 °C buffered water for up to 80 weeks. We previously reported that water exposure in these experiments resulted in a molar mass reduction, where the kinetics of the hydrolysis reaction is supported by a straight forward Arrhenius analysis over a range of accelerated temperatures (37-85 °C). We also showed that the ultimate tensile properties of P35 and E2A were significantly compromised when the molar mass was reduced. Here, we show that the reduction in molar mass also correlated with a reduction in both the abrasion and fatigue resistance. The instantaneous wear rate of both P35 and E2A, when exposed to the reciprocating motion of an ethylene tetrafluoroethylene (ETFE) jacketed cable, increased with the inverse of the number averaged molar mass (1/Mn). Both materials showed a change in the wear surface when the number-averaged molar mass was reduced to ≈ 16 kg/mole, where a smooth wear surface transitioned to a 'spalling-like' pattern, leaving the wear surface with ≈ 0.3 mm cracks that propagated beyond the contact surface. The fatigue crack growth rate for P35 and E2A also increased in proportion to 1/Mn, after the molar mass was reduced below a critical value of ≈30 kg/mole. Interestingly, this critical molar mass coincided with that at which the single cycle stress-strain response changed from strain hardening to strain softening. The changes in both abrasion and fatigue resistance, key predictors for long term reliability of cardiac leads, after exposure of this class of PDMS-urethanes to water suggests that these materials are susceptible to mechanical compromise in vivo.

  7. Black Holes From the Dark Ages: Exploring the Reionization Era and Early Structure Formation With Quasars and Gamma-Ray Bursts

    CERN Document Server

    Djorgovski, S G


    The cosmic reionization era, which includes formation of the first stars, galaxies, and AGN, is now one of the most active frontiers of cosmological research. We review briefly our current understanding of the early structure formation, and use the ideas about a joint formation of massive black holes (which power the early QSOs) and their host galaxies to employ high-redshift QSOs as probes of the early galaxy formation and primordial large-scale structure. There is a growing evidence for a strong biasing in the formation of the first luminous sources, which would lead to a clumpy reionization. Absorption spectroscopy of QSOs at z > 6 indicates the end of the reionization era at z ~ 6; yet measurements from the WMAP satellite suggest and early reionization at z ~ 10 - 20. The first generation of massive stars, perhaps aided by the early mini-quasars, may have reionized the universe at such high redshifts, but their feedback may have disrupted the subsequent star and galaxy formation, leading to an extended an...

  8. Stand structure and yield of the mixed white poplar and black locust plantations on sandy ridges between the Danube and Tisza rivers in Hungary

    Institute of Scientific and Technical Information of China (English)


    The paper deals with the stand structure and yield of black locust (Robinia pseudoacacia L.) forests mixed with white (Populus alba L.) in various proportions, partly applying a new methodological approach. The main stand structure and yield factors were determined separately for each species, measured stem by stem, using the volume functions prepared for each species. The ratio of the volumes of the species (A and B) in mixed and in pure stands (based on volume tables) was determined. A close relationship has been found between the ratio by relative total volume and the proportion (by the number of stems) of the species. The relative surplus in the volume of the mixed stands varied between 1.24-1.55 at the age of 16 compared to the control, i.e. the yield of pure stands of the species concerned. The trial has also proven that if two species have a fast initial growth rate and a similar rotation age, they can be planted in mixed stands resulting in mutual advantages.

  9. Black gold

    CERN Document Server

    Fletcher, MW


    Following the Yom Kippur war of October 1973, OPEC raises the price of oil by 70% along with a 5% reduction in oil production. Len Saunders a highly skilled and knowledgeable British engineer for Jaguar motors, is approached by the UK energy commission in the January of 1974 to create a new propulsion system; using a secret document from a German WW2 scientist, that they have come into possession of. Len Saunders sets to work on creating the holy grail of energy. Seven years later 1981, Haidar Farooq the Kuwait oil minister working at OPEC and head of a secret organisation named Black Gold bec

  10. High quality sub-10 nm graphene nanoribbons by on-chip PS-b-PDMS block copolymer lithography

    DEFF Research Database (Denmark)

    Rasappa, Sozaraj; Caridad, Jose; Schulte, Lars


    the trenches of graphoepitaxial substrates. The SD template was furthermore used as lithographic mask to fabricate high-quality sub-10 nm graphene nanoribbons. This was realized by one step oxygen plasma treatment, which accomplishes three tasks: hardening the PDMS block by oxidation, and etching both the PS...... block and the graphene under PS. Raman analysis supports the formation of graphene nanoribbons with an average distance between defects corresponding to the oxidized PDMS pitch, with no sign of defects generated in the ribbon channel. This suggests a high degree of protection of the nanoribbons...... of 10.5 kg/mol. Thin SD films directly spin cast onto silicon substrates and on graphene, form regular line patterns of sub-10 nm pitch on the substrates after few minutes of annealing at 45 ºC in the presence of toluene vapour. Perfect pattern alignment was achieved by confining the films inside...

  11. Formation of Supermassive Black Holes

    CERN Document Server

    Volonteri, Marta


    Evidence shows that massive black holes reside in most local galaxies. Studies have also established a number of relations between the MBH mass and properties of the host galaxy such as bulge mass and velocity dispersion. These results suggest that central MBHs, while much less massive than the host (~ 0.1%), are linked to the evolution of galactic structure. In hierarchical cosmologies, a single big galaxy today can be traced back to the stage when it was split up in hundreds of smaller components. Did MBH seeds form with the same efficiency in small proto-galaxies, or did their formation had to await the buildup of substantial galaxies with deeper potential wells? I briefly review here some of the physical processes that are conducive to the evolution of the massive black hole population. I will discuss black hole formation processes for `seed' black holes that are likely to place at early cosmic epochs, and possible observational tests of these scenarios.

  12. Optical black hole lasers

    CERN Document Server

    Faccio, Daniele; Lamperti, Marco; Leonhardt, Ulf


    Using numerical simulations we show how to realise an optical black hole laser, i.e. an amplifier formed by travelling refractive index perturbations arranged so as to trap light between a white and a black hole horizon. The simulations highlight the main features of these lasers: the growth inside the cavity of positive and negative frequency modes accompanied by a weaker emission of modes that occurs in periodic bursts corresponding to the cavity round trips of the trapped modes. We then highlight a new regime in which the trapped mode spectra broaden until the zero-frequency points on the dispersion curve are reached. Amplification at the horizon is highest for zero-frequencies, therefore leading to a strong modification of the structure of the trapped light. For sufficiently long propagation times, lasing ensues only at the zero-frequency modes.

  13. Polyelectrolyte multilayer surface functionalization of poly(dimethylsiloxane) (PDMS) for reduction of yeast cell adhesion in microfluidic devices


    Schmolke, Hannah; Demming, Stefanie; Edlich, Astrid; Magdanz, Veronika; Büttgenbach, Stephanus; Franco-Lara, Ezequiel; Krull, Rainer; Klages, Claus-Peter


    Polyelectrolyte multilayers (PEMs) based on the combinations poly(diallyldimethylammonium chloride)∕poly(acrylic acid) (PDADMAC∕PAA) and poly(allylamine hydrochloride)∕PAA (PAH∕PAA) were adsorbed on poly(dimethylsiloxane) (PDMS) and tested for nonspecific surface attachment of hydrophobic yeast cells using a parallel plate flow chamber. A custom-made graft copolymer containing poly(ethylene glycol) (PEG) side chains (PAA-g-PEG) was additionally adsorbed on the PEMs as a terminal layer. A suit...

  14. Influence of the PDMS substrate stiffness on the adhesion of Acanthamoeba castellanii

    Directory of Open Access Journals (Sweden)

    Sören B. Gutekunst


    Full Text Available Background: Mechanosensing of cells, particularly the cellular response to substrates with different elastic properties, has been discovered in recent years, but almost exclusively in mammalian cells. Much less attention has been paid to mechanosensing in other cell systems, such as in eukaryotic human pathogens.Results: We report here on the influence of substrate stiffness on the adhesion of the human pathogen Acanthamoebae castellanii (A. castellanii. By comparing the cell adhesion area of A. castellanii trophozoites on polydimethylsiloxane (PDMS substrates with different Young’s moduli (4 kPa, 29 kPa, and 128 kPa, we find significant differences in cell adhesion area as a function of substrate stiffness. In particular, the cell adhesion area of A. castellanii increases with a decreasing Young’s modulus of the substrate.Conclusion: The dependence of A. castellanii adhesion on the elastic properties of the substrate is the first study suggesting a mechanosensory effect for a eukaryotic human pathogen. Interestingly, the main targets of A. castellanii infections in the human body are the eye and the brain, i.e., very soft environments. Thus, our study provides first hints towards the relevance of mechanical aspects for the pathogenicity of eukaryotic parasites.

  15. PDMS glass serpentine microchannel chip for time domain PCR with bubble suppression in sample injection (United States)

    Cho, Chul-Ho; Cho, Woong; Ahn, Yoomin; Hwang, Seung-Yong


    This paper reports on the development of a low-cost microreactor (10 µl) biochip for DNA polymerase chain reaction (PCR). The microbiochip (20 mm × 28 mm) is a hybrid type that is composed of a polydimethylsiloxane (PDMS) layer with a serpentine microchannel (360 µm × 100 µm) chamber and glass substrate integrated with a microheater and thermal microsensor. Because of the hydrophobic chip surface, bubbles are usually created during sample loading in the PMDS-based microchip. These bubbles disrupt the stable biochemical reaction. An improved microreactor chamber was designed using microfluidic simulation. The reactor has a rounded-corner serpentine channel architecture, which enables stable injection into the hydrophobic surface using only a micropipette. The reactor temperature needed for the PCR reaction is controlled within ±0.5 °C by the LabVIEW software proportional-integrative-derivative (PID) controller. PCR analyses of the sex-determining Y chromosome (SRY) gene and mouse GAPDH gene were successfully performed in less than 54 min by the fabricated microreactor chip.

  16. Transient deflection response in microcantilever array integrated with polydimethylsiloxane (PDMS) microfluidics. (United States)

    Anderson, Ryan R; Hu, Weisheng; Noh, Jong Wook; Dahlquist, William C; Ness, Stanley J; Gustafson, Timothy M; Richards, Danny C; Kim, Seunghyun; Mazzeo, Brian A; Woolley, Adam T; Nordin, Gregory P


    We report the integration of a nanomechanical sensor consisting of 16 silicon microcantilevers with polydimethylsiloxane (PDMS) microfluidics. For microcantilevers positioned near the bottom of a microfluidic flow channel, a transient differential analyte concentration for the top versus bottom surface of each microcantilever is created when an analyte-bearing fluid is introduced into the flow channel (which is initially filled with a non-analyte containing solution). We use this effect to characterize a bare (nonfunctionalized) microcantilever array in which the microcantilevers are simultaneously read out with our recently developed high sensitivity in-plane photonic transduction method. We first examine the case of non-specific binding of bovine serum albumin (BSA) to silicon. The average maximum transient microcantilever deflection in the array is -1.6 nm, which corresponds to a differential surface stress of only -0.23 mN m(-1). This is in excellent agreement with the maximum differential surface stress calculated based on a modified rate equation in conjunction with finite element simulation. Following BSA adsorption, buffer solutions with different pH are introduced to further study microcantilever array transient response. Deflections of 20-100 nm are observed (2-14 mN m(-1) differential surface stress). At a flow rate of 5 μL min(-1), the average measured temporal width (FWHM) of the transient response is 5.3 s for BSA non-specific binding and 0.74 s for pH changes.

  17. Transparent, superhydrophobic, and wear-resistant surfaces using deep reactive ion etching on PDMS substrates. (United States)

    Ebert, Daniel; Bhushan, Bharat


    Surfaces that simultaneously exhibit superhydrophobicity, low contact angle hysteresis, and high transmission of visible light are of interest for many applications, such as optical devices, solar panels, and self-cleaning windows. Superhydrophobicity could also find use in medical devices where antifouling characteristics are desirable. These applications also typically require mechanical wear resistance. The fabrication of such surfaces is challenging due to the competing goals of superhydrophobicity and transmittance in terms of the required degree of surface roughness. In this study, deep reactive ion etching (DRIE) was used to create rough surfaces on PDMS substrates using a O2/CF4 plasma. Surfaces then underwent an additional treatment with either octafluorocyclobutane (C4F8) plasma or vapor deposition of perfluorooctyltrichlorosilane (PFOTCS) following surface activation with O2 plasma. The effects of surface roughness and the additional surface modifications were examined with respect to the contact angle, contact angle hysteresis, and optical transmittance. To examine wear resistance, a sliding wear experiment was performed using an atomic force microscope (AFM).

  18. Fabrication of the replica templated from butterfly wing scales with complex light trapping structures (United States)

    Han, Zhiwu; Li, Bo; Mu, Zhengzhi; Yang, Meng; Niu, Shichao; Zhang, Junqiu; Ren, Luquan


    The polydimethylsiloxane (PDMS) positive replica templated twice from the excellent light trapping surface of butterfly Trogonoptera brookiana wing scales was fabricated by a simple and promising route. The exact SiO2 negative replica was fabricated by using a synthesis method combining a sol-gel process and subsequent selective etching. Afterwards, a vacuum-aided process was introduced to make PDMS gel fill into the SiO2 negative replica, and the PDMS gel was solidified in an oven. Then, the SiO2 negative replica was used as secondary template and the structures in its surface was transcribed onto the surface of PDMS. At last, the PDMS positive replica was obtained. After comparing the PDMS positive replica and the original bio-template in terms of morphology, dimensions and reflectance spectra and so on, it is evident that the excellent light trapping structures of butterfly wing scales were inherited by the PDMS positive replica faithfully. This bio-inspired route could facilitate the preparation of complex light trapping nanostructure surfaces without any assistance from other power-wasting and expensive nanofabrication technologies.

  19. Imagine the Universe! The Anatomy of Black Holes. Probing the Structure & Evolution of the Cosmos. An Information and Activity Booklet. Grades 9-12, 1998-1999. (United States)

    Whitlock, Laura A.; Granger, Kara C.; Mahon, Jane D.

    The information provided in this booklet is meant to give the necessary background information so that the science of black holes can be taught confidently to secondary students. The featured activities can be used to engage and excite students about the topic of black holes in different disciplines and in a number of ways. Activities include: (1)…

  20. Edge phonons in black phosphorus (United States)

    Ribeiro, H. B.; Villegas, C. E. P.; Bahamon, D. A.; Muraca, D.; Castro Neto, A. H.; de Souza, E. A. T.; Rocha, A. R.; Pimenta, M. A.; de Matos, C. J. S.


    Black phosphorus has recently emerged as a new layered crystal that, due to its peculiar and anisotropic crystalline and electronic band structures, may have important applications in electronics, optoelectronics and photonics. Despite the fact that the edges of layered crystals host a range of singular properties whose characterization and exploitation are of utmost importance for device development, the edges of black phosphorus remain poorly characterized. In this work, the atomic structure and behaviour of phonons near different black phosphorus edges are experimentally and theoretically studied using Raman spectroscopy and density functional theory calculations. Polarized Raman results show the appearance of new modes at the edges of the sample, and their spectra depend on the atomic structure of the edges (zigzag or armchair). Theoretical simulations confirm that the new modes are due to edge phonon states that are forbidden in the bulk, and originated from the lattice termination rearrangements.

  1. Functionalization of PDMS modified and plasma activated two-component polyurethane coatings by surface attachment of enzymes (United States)

    Kreider, Alexej; Richter, Katharina; Sell, Stephan; Fenske, Mandus; Tornow, Christian; Stenzel, Volkmar; Grunwald, Ingo


    This article describes a new strategy for coupling the enzyme horseradish peroxidase to a two-component polyurethane (2C-PUR) coating. A stable polymer conjugate was achieved by combining the enzyme and the 2C-PUR coating which was modified with poly(dimethylsiloxane) (PDMS), located at the surface. An atmospheric pressure plasma jet system was used to convert alkyl groups from the PDMS into polar silanol functionalities. This conversion was proven by X-ray photoelectron spectroscopy and dynamic contact angle measurements. In addition, the stability of the activated 2C-PUR surface containing silanol groups was determined by measuring the contact angle as a function of time. Compared to the non-modified 2C-PUR systems the one with PDMS displayed a higher stability over a time period over 28 h. In a silanization process the coating was treated with (3-aminopropyl) trimethoxysilane and the enzyme was subsequently immobilized to the coating via the cross linker glutaraldehyde to receive new biomimetic catalytic/enzymatic functions. The chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity as compared to references samples without using a cross linker (physisorption). The presented technique offers the opportunity to design new and smart multifunctional surface coatings which employ biomimetic capabilities.

  2. Functionalization of PDMS modified and plasma activated two-component polyurethane coatings by surface attachment of enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Kreider, Alexej; Richter, Katharina; Sell, Stephan; Fenske, Mandus; Tornow, Christian; Stenzel, Volkmar [Fraunhofer Institute for Manufacturing Technology and Advanced Materials - IFAM, Wiener Strasse 12, 28359 Bremen (Germany); Grunwald, Ingo, E-mail: [Fraunhofer Institute for Manufacturing Technology and Advanced Materials - IFAM, Wiener Strasse 12, 28359 Bremen (Germany)


    This article describes a new strategy for coupling the enzyme horseradish peroxidase to a two-component polyurethane (2C-PUR) coating. A stable polymer conjugate was achieved by combining the enzyme and the 2C-PUR coating which was modified with poly(dimethylsiloxane) (PDMS), located at the surface. An atmospheric pressure plasma jet system was used to convert alkyl groups from the PDMS into polar silanol functionalities. This conversion was proven by X-ray photoelectron spectroscopy and dynamic contact angle measurements. In addition, the stability of the activated 2C-PUR surface containing silanol groups was determined by measuring the contact angle as a function of time. Compared to the non-modified 2C-PUR systems the one with PDMS displayed a higher stability over a time period over 28 h. In a silanization process the coating was treated with (3-aminopropyl) trimethoxysilane and the enzyme was subsequently immobilized to the coating via the cross linker glutaraldehyde to receive new biomimetic catalytic/enzymatic functions. The chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity as compared to references samples without using a cross linker (physisorption). The presented technique offers the opportunity to design new and smart multifunctional surface coatings which employ biomimetic capabilities.

  3. A Contact Angle Study of the Interaction between Embedded Amphiphilic Molecules and the PDMS Matrix in an Aqueous Environment

    Directory of Open Access Journals (Sweden)

    Wenjun Qiu


    Full Text Available Poly(dimethylsiloxane (PDMS surface modification via gradient-induced transport of embedded amphiphilic molecules is a novel, easy, flexible, and environmentally friendly approach for reducing protein adsorption on PDMS in microfluidic applications. To better understand the processing and the potential use in the viability-sensitive applications such as manipulation and culturing of primary neural cells, we systematically investigate how embedded molecules interact with a PDMS matrix and its surface in aqueous environments by studying the wetting angle over time under various processing conditions, including water exposure time, water exposure temperature, curing master materials, in addition to comparing different embedded amphiphilic molecules. The results indicate that the water exposure time clearly plays an important role in the surface properties. Our interpretation is that molecular rearrangement of the surface-embedded molecules improves surface coverage in the short term; while over a longer period, the transport of molecules embedded in the bulk enhance its coverage. However, this improvement finally terminates when molecules transported from the bulk to the surface are not sufficient to replace the molecules leaching into the water.

  4. Development of an electrolyte based on a composite of TEOS/PDMS/ALUMINA with phosphotungstic acid for PEMFC application

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, D.G.; Lima, M.O.; Santa Rosa, L.O.; Jose, N.M.; Boaventura, F.J.S. [Univ. Federal da Bahia, Salvador (Brazil). Dept. of Physical Chemistry


    This study analyzed the suitability of PDMS/TEOS/Al203/PWA membranes for use in proton exchange membrane fuel cells (PEMFC) applications. The membranes were prepared using a sol-gel method and were comprised of polydimethylsiloxane (PDMS) reticulated with tetraethoxysilane (TEOS) reinforced with alumina. Phosphotunguistic acid was used as a proton conducting species. PDMS and TEOS were reacted in a 70-30 mass proportion. Al203 and PWA were then incorporated in mass proportions of 5, 10, 15, 20, and 25 per cent. The membranes were then analyzed using X-ray diffraction (XRD), thermogravimetric (TG), direct scanning calorimetry (DSC) and Fourier Transform Infrared (FTIR) techniques. The band characteristics of the hybrid matrix and alumina were characterized. Results of the study showed that the thermal stability and residual mass of the membranes increased with the addition of reinforcing materials. Conductivity was 10 mS per cm, which decreased with increases in crystallinity. Homogenous reinforcement distribution was observed throughout the matrix. It was concluded that the materials are suitable for PEMFC applications.

  5. Nanoparticle-Incorporated PDMS Film as an Improved Performance SPME Fiber for Analysis of Volatile Components of Eucalyptus Leaf

    Directory of Open Access Journals (Sweden)

    Parviz Aberoomand Azar


    Full Text Available A new fabrication strategy was proposed to prepare polydimethylsiloxane (PDMS- coated solid-phase microextraction (SPME on inexpensive and unbreakable Cu fiber. PDMS was covalently bonded to the Cu substrate using self-assembled monolayer (SAM of (3-mercaptopropyltrimethoxysilane (3MPTS as binder. To increase the performance of the fiber, the incorporation effect of some nanomaterials including silica nanoparticles (NPs, carbon nanotubes (CNTs, and carboxylated carbon nanotubes (CNT-COOH to PDMS coating was compared. The surface morphology of the prepared fibers was characterized by scanning electron microscopy (SEM, and their applicability was evaluated through the extraction of some volatile organic compounds (VOCs of Eucalyptus leaf in headspace mode, and parameters affecting the extraction efficiency including extraction temperature and extraction time were optimized. Extracted compounds were analyzed by GC-MS instrument. The results obtained indicated that prepared fibers have some advantages relative to previously prepared SPME fibers, such as higher thermal stability and improved performance of the fiber. Also, results showed that SPME is a fast, simple, quick, and sensitive technique for sampling and sample introduction of Eucalyptus VOCs.

  6. Chemical modification of PDMS surface without impacting the viscoelasticity: Model systems for a better understanding of elastomer/elastomer adhesion and friction


    DIRANY, Mohammed; DIES, Laëtitia; Restagno, Frédéric; Léger, Liliane; Poulard, Christophe; MIQUELARD-GARNIER, Guillaume


    The influence of both viscoelastic and interfacial parameters on the surface properties of elastomers is difficult to study. Here, we describe a simple route to achieve surface modification of PDMS without impacting the viscoelastic properties of the bulk. PEG modified PDMS surfaces were synthesized by two step surface modification based on hydrosilylation. The covalent grafting of PEG on the surface has been evidenced by AFM and ATR-FTIR, and its effect on the hydrophilicity characterized by...

  7. Surface modification of poly(dimethylsiloxane) (PDMS) microchannels with DNA capture-probes for potential use in microfluidic DNA analysis systems (United States)

    Khodakov, Dmitriy A.; Thredgold, Leigh D.; Lenehan, Claire E.; Andersson, Gunther A.; Kobus, Hilton; Ellis, Amanda V.


    Poly(dimethylsiloxane) (PDMS) is an elastomeric material used for microfluidic devices and is especially suited to medical and forensic applications. This is due to its relatively low cost, ease of fabrication, excellent optical transmission characteristics and its ability to support electroosmotic flow, required during electrophoretic separations. These aspects combined with its large range of surface modification chemistries, make PDMS an attractive substrate in microfluidic devices for, in particular, DNA separation. Here, we report the successful wet chemical surface modification of PDMS microchannels using a simple three step method to produce an isothiocyanate-terminated surface. Initially, PDMS was oxygen plasma treated to produce a silanol-terminated surface, this was then reacted with 3-aminopropyltriethoxysilane with subsequent reaction of the now amine-terminated surface with p-phenylenediisothiocyanate. Water contact angle measurements both before and after modification showed a reduction in hydrophobicity from 101o for native PDMS to 94o for the isothiocyante-terminated PDMS. The isothiocyanate-terminated surface was then coupled with an amineterminated single-stranded DNA (ssDNA) oligonucleotide capture probe via a thiourea linkage. Confirmation of capture probe attachment was observed using fluorescent microscopy after hybridization of the capture probes with fluorescently labeled complimentary ssDNA oligonucleotides.

  8. The Black Hole Universe Model (United States)

    Zhang, Tianxi


    The black hole universe model is a multiverse model of cosmology recently developed by the speaker. According to this new model, our universe is a fully grown extremely supermassive black hole, which originated from a hot star-like black hole with several solar masses, and gradually grew up from a supermassive black hole with million to billion solar masses to the present state with trillion-trillion solar masses by accreting ambient matter or merging with other black holes. The entire space is structured with infinite layers or universes hierarchically. The innermost three layers include the universe that we live, the inside star-like and supermassive black holes called child universes, and the outside space called mother universe. The outermost layer is infinite in mass, radius, and entropy without an edge and limits to zero for both the matter density and absolute temperature. All layers are governed by the same physics and tend to expand physically in one direction (outward or the direction of increasing entropy). The expansion of a black hole universe decreases its density and temperature but does not alter the laws of physics. The black hole universe evolves iteratively and endlessly without a beginning. When one universe expands out, a new similar one is formed from inside star-like and supermassive black holes. In each of iterations, elements are resynthesized, matter is reconfigurated, and the universe is renewed rather than a simple repeat. The black hole universe is consistent with the Mach principle, observations, and Einsteinian general relativity. It has only one postulate but is able to explain all phenomena occurred in the universe with well-developed physics. The black hole universe does not need dark energy for acceleration and an inflation epoch for flatness, and thus has a devastating impact on the big bang model. In this talk, I will present how this new cosmological model explains the various aspects of the universe, including the origin

  9. Particles that slide over the water surface: Synthesis and characterization of iron oxides particles coated with PDMS, with hydrophobic and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Souza Neto, Francisco [Sciences and Technology Unit of the University – UnUCET, State University of Goiás, 75132-903 Anápolis, GO (Brazil); Araújo, Olacir Alves, E-mail: [Sciences and Technology Unit of the University – UnUCET, State University of Goiás, 75132-903 Anápolis, GO (Brazil); Guilherme, Luciana R.; Garg, Vijayendra K. [Sciences and Technology Unit of the University – UnUCET, State University of Goiás, 75132-903 Anápolis, GO (Brazil); Oliveira, Aderbal C.; Souza, Paulo E.N. de [Institute of Physics, University of Brasília, 70910-900 Brasília, DF (Brazil); Franco Júnior, Adolfo [Institute of Physics, Federal University of Goiás, 74001-970 Goiânia, GO (Brazil)


    Magnetic nanoparticles have been of great scientific interest because of their possible industrial and biomedical applications. The magnetic iron oxide was synthesized by the co precipitation of alkaline hydrolysis of ions Fe{sup 2+} and Fe{sup 3+} in aqueous system. The coated particles were obtained by heating (50 and 250 °C) mixed magnetic iron oxide and polydimethylsiloxane oil for 30 min obtaining magnetic dust particles with hydrophobic behavior. These were used to learn the dragging effects and removal of nonpolar organic compound in aqueous systems. The samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), chemical analysis by potenciometric titration, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), contact angle measurement and Mössbauer spectroscopy. The diffractogram of X-ray presented peaks that were assigned to presence of spinel structure maghemite and magnetite with medium sized crystallites of 10.95 nm for the polymeric coated magnetic iron oxide, confirmed by TEM, with superparamagnetic character, also confirmed by VSM. The infrared spectrum showed absorption band at 570 cm{sup −1} characteristic of the Fe-O bonding in inverted spinel structure and the absorption bands in 1263, 1105, 1025 and 800 cm{sup −1} indicating the presence of PDMS on the magnetic iron oxide particles. Thermogravimetric analysis has been used to estimate the sample thermal stability of polymeric material (9.7 ± 4) % on the inorganic matrices. Contact angle measurement of the coated samples at 250 °C presented a better nonpolar character in comparison to the coated samples at 50 °C. The samples at room temperature (25 °C) presented the phases of magnetite and maghemite which were also confirmed by Mössbauer spectroscopy. It was possible to obtain iron oxides particles coated with PDMS, with hydrophobic and magnetic properties, which slide over the

  10. The fabrication of microfluidic structures by means of full-wafer adhesive bonding using a poly(dimethylsiloxane) catalyst (United States)

    Samel, Björn; Kamruzzaman Chowdhury, M.; Stemme, Göran


    In this work, we present the use of a PDMS (poly(dimethylsiloxane)) curing-agent as the intermediate layer for adhesive full-wafer bonding suitable for fabrication of microfluidic structures. The curing-agent of the two-component silicone rubber (Sylgard 184) is spin coated on a substrate, brought into contact with another PDMS layer and heat cured to create an irreversible seal which is as strong as or even stronger than plasma-assisted PDMS bonding. The maximum bond strength is measured to 800 kPa when bonding together PDMS and silicon. The applicability of the new PDMS adhesive bonding method is verified by means of fabricating microfluidic structures. Using this method allows for wafer-level bonding of PDMS to various materials such as PDMS, glass or silicon and more importantly to selectively bond different layers by using a patterned adhesive bonding technique. Moreover, precise alignment of the structural layers is facilitated since curing is initiated upon heat which is an advantage when fabricating multilayer microfluidic devices.

  11. Underground riparian wood: Reconstructing the processes influencing buried stem and coarse root structures of Black Poplar (Populus nigra L.) (United States)

    Holloway, James V.; Rillig, Matthias C.; Gurnell, Angela M.


    Following analysis of morphological (including dendrochronological and sedimentological) aspects of buried stem and coarse root structures of eight mature P. nigra individuals located within two sites along the middle to lower Tagliamento River, Italy (Holloway et al., in press), this paper introduces information on the historical processes of vegetation development and river flow and links this to the form of these eight trees. Aerial images and flow time series are assembled to reconstruct the flood history, potential recruitment periods, and vegetation cover development in the vicinity of the studied trees. This information is combined with previous morphological evidence to reconstruct the development history of each tree via three-element summary diagrams showing (i) a time series of floods, aerial imagery dates, and potential recruitment periods, with colour-coded bars indicating likely key stages in the development of the tree; (ii) colour-coded overlays on an SfM photogrammetric model of each tree; and (iii) colour-coded text boxes providing explanatory annotations. The combined morphology-process analysis reveals complex three-dimensional underground structures, incorporating buried stems, shoots, and adventitious roots that are sometimes joined by grafting, linking the standing tree with the buried gravel surface on which it was recruited. Analysis of process data provides a firm basis for identifying and dating influential flow disturbance events and recruitment windows and shows that a relatively small number of flood events have significantly impacted the studied trees, which are mainly but not exclusively the largest floods in the record. Nevertheless, we stress that all suggested dates are best estimates in the light of the combined evidence. There is undoubted potential for building different interpretations of belowground woody structure development in light of such evidence, but we feel that the form and timing of the developmental trajectories we

  12. Black Urine

    Directory of Open Access Journals (Sweden)

    Rahim Vakili


    Full Text Available A 2-year-old boy was born at term of healthy, non-consanguineous Iranian parents. His mother attended in the clinic with the history of sometimes discoloration of diapers after passing urine. She noticed that first at the age of one month with intensified in recent months. His Physical examination and growth parameters were normal. His mother denied taking any medication (sorbitol, nitrofurantoin, metronidazole, methocarbamol, sena and methyldopa (5. Qualitative urine examination showed dark black discoloration. By this history, alkaptonuria was the most clinical suspicious. A 24-hour-urine sample was collected and sent for quantitative measurements. The urine sample was highly positive for homogentisic acid and negative for porphyrin metabolites.

  13. Black Holes and Beyond

    CERN Document Server

    Mathur, Samir D


    The black hole information paradox forces us into a strange situation: we must find a way to break the semiclassical approximation in a domain where no quantum gravity effects would normally be expected. Traditional quantizations of gravity do not exhibit any such breakdown, and this forces us into a difficult corner: either we must give up quantum mechanics or we must accept the existence of troublesome `remnants'. In string theory, however, the fundamental quanta are extended objects, and it turns out that the bound states of such objects acquire a size that grows with the number of quanta in the bound state. The interior of the black hole gets completely altered to a `fuzzball' structure, and information is able to escape in radiation from the hole. The semiclassical approximation can break at macroscopic scales due to the large entropy of the hole: the measure in the path integral competes with the classical action, instead of giving a subleading correction. Putting this picture of black hole microstates ...

  14. Phases of Kaluza-Klein Black Holes

    DEFF Research Database (Denmark)

    Harmark, Troels; Obers, N. A.


    We review the latest progress in understanding the phase structure of static and neutral Kaluza-Klein black holes, i.e. static and neutral solutions of pure gravity with an event horizon that asymptote to a d-dimensional Minkowski-space times a circle. We start by reviewing the (mu,n) phase diagram...... and the split-up of the phase structure into solutions with an internal SO(d-1) symmetry and solutions with Kaluza-Klein bubbles. We then discuss the uniform black string, non-uniform black string and localized black hole phases, and how those three phases are connected, involving issues such as classical...... instability and horizon-topology changing transitions. Finally, we review the bubble-black hole sequences, their place in the phase structure and interesting aspects such as the continuously infinite non-uniqueness of solutions for a given mass and relative tension....

  15. Evolution of supermassive black holes

    CERN Document Server

    Volonteri, M


    Supermassive black holes (SMBHs) are nowadays believed to reside in most local galaxies, and the available data show an empirical correlation between bulge luminosity - or stellar velocity dispersion - and black hole mass, suggesting a single mechanism for assembling black holes and forming spheroids in galaxy halos. The evidence is therefore in favour of a co-evolution between galaxies, black holes and quasars. In cold dark matter cosmogonies, small-mass subgalactic systems form first to merge later into larger and larger structures. In this paradigm galaxy halos experience multiple mergers during their lifetime. If every galaxy with a bulge hosts a SMBH in its center, and a local galaxy has been made up by multiple mergers, then a black hole binary is a natural evolutionary stage. The evolution of the supermassive black hole population clearly has to be investigated taking into account both the cosmological framework and the dynamical evolution of SMBHs and their hosts. The seeds of SMBHs have to be looked ...

  16. Embryonic staging system for the Black Mastiff Bat, Molossus rufus (Molossidae), correlated with structure-function relationships in the adult. (United States)

    Nolte, Mark J; Hockman, Dorit; Cretekos, Chris J; Behringer, Richard R; Rasweiler, John J


    An embryonic staging system for Molossus rufus (also widely known as Molossus ater) was devised using 17 reference specimens obtained during the postimplantation period of pregnancy from wild-caught, captive-bred females. This was done in part by comparing the embryos to a developmental staging system that had been created for another, relatively unrelated bat, Carollia perspicillata (family Phyllostomidae). Particular attention was paid to the development of species-specific features, such as wing and ear morphology, and these are discussed in light of the adaptive significance of these structures in the adult. M. rufus can be maintained and bred in captivity and is relatively abundant in the wild. This embryonic staging system will facilitate further developmental studies of M. rufus, a model species for one of the largest and most successful chiropteran families, the Molossidae.

  17. Black hole entropy in loop quantum gravity (United States)

    Agulló, Iván; Barbero G, J. Fernando; Borja, E. F.; Díaz-Polo, Jacobo; Villaseñor, Eduardo J. S.


    We discuss the recent progress on black hole entropy in loop quantum gravity, focusing in particular on the recently discovered discretization effect for microscopic black holes. Powerful analytical techniques have been developed to perform the exact computation of entropy. A statistical analysis of the structures responsible for this effect shows its progressive damping and eventual disappearance as one increases the considered horizon area.

  18. Strain Sensors with Adjustable Sensitivity by Tailoring the Microstructure of Graphene Aerogel/PDMS Nanocomposites. (United States)

    Wu, Shuying; Ladani, Raj B; Zhang, Jin; Ghorbani, Kamran; Zhang, Xuehua; Mouritz, Adrian P; Kinloch, Anthony J; Wang, Chun H


    Strain sensors with high elastic limit and high sensitivity are required to meet the rising demand for wearable electronics. Here, we present the fabrication of highly sensitive strain sensors based on nanocomposites consisting of graphene aerogel (GA) and polydimethylsiloxane (PDMS), with the primary focus being to tune the sensitivity of the sensors by tailoring the cellular microstructure through controlling the manufacturing processes. The resultant nanocomposite sensors exhibit a high sensitivity with a gauge factor of up to approximately 61.3. Of significant importance is that the sensitivity of the strain sensors can be readily altered by changing the concentration of the precursor (i.e., an aqueous dispersion of graphene oxide) and the freezing temperature used to process the GA. The results reveal that these two parameters control the cell size and cell-wall thickness of the resultant GA, which may be correlated to the observed variations in the sensitivities of the strain sensors. The higher is the concentration of graphene oxide, then the lower is the sensitivity of the resultant nanocomposite strain sensor. Upon increasing the freezing temperature from -196 to -20 °C, the sensitivity increases and reaches a maximum value of 61.3 at -50 °C and then decreases with a further increase in freezing temperature to -20 °C. Furthermore, the strain sensors offer excellent durability and stability, with their piezoresistivities remaining virtually unchanged even after 10 000 cycles of high-strain loading-unloading. These novel findings pave the way to custom design strain sensors with a desirable piezoresistive behavior.

  19. Air-stable supported membranes for single-cell cytometry on PDMS microchips. (United States)

    Phillips, K Scott; Kang, Kyung Mo; Licata, Louise; Allbritton, Nancy L


    Protein-reinforced supported bilayer membranes (rSBMs) composed of phosphatidylcholine (PC), biotin-PE and Neutravidin were used to coat hybrid microchips composed of polydimethylsiloxane (PDMS) and glass. Since the coatings required a freshly oxidized, hydrophilic substrate, a novel method to rapidly connect reservoirs using plasma oxidation was first developed and found to support up to 5.2 N cm(-2) (1.5 N) pull-off force. rSBMs were then assembled in the oxidized hydrophilic channels. The electroosmotic mobility (mu(eo)) of rSBM-coated channels was measured over a 3 h time to evaluate the stability of the coatings for microchip electrophoresis. rSBM-coated microchips with a simple cross-design had excellent properties for microchip separations, yielding efficiencies of up to 700,000 plates m(-1) for fluorescent dyes and peptides. The separation performance of rSBM and PC-coated channels was evaluated after repeatedly drying and rehydrating the channels. The separation efficiency of fluorescein on PC-coated devices decreased by 40% after one dehydration cycle and nearly 75% after 3 cycles. In contrast for rSBM-coated devices there was no significant change in the fluorescein efficiency until the third cycle (10% decreased efficiency). rSBM-coated channels were also markedly more stable when placed in a dehydrated state during long-term storage compared to PC-coated channels, and showed reduced chip failure and no reduction in performance for up to one month of dehydrated storage. Finally, rSBM-coated devices were used to perform single-cell cytometry. Microchips that had been dehydrated, stored two weeks, and rehydrated prior to use demonstrated similar performance to newly coated devices for the separation of fluorescein and carboxyfluorescein from single cells. Thus rSBM-coated devices were rugged withstanding electric fields, prolonged storage under dehydrated conditions, and biofouling by cellular constituents while maintaining excellent separation

  20. Highly-compliant, microcable neuroelectrodes fabricated from thin-film gold and PDMS. (United States)

    McClain, Maxine A; Clements, Isaac P; Shafer, Richard H; Bellamkonda, Ravi V; LaPlaca, Michelle C; Allen, Mark G


    Bio-electrodes have traditionally been made of materials such as metal and silicon that are much stiffer than the tissue from which they record or stimulate. This difference in mechanical compliance can cause incomplete or ineffective contact with the tissue. The electrode stiffness has also been hypothesized to cause chronic low-grade injury and scar-tissue encapsulation, reducing stimulation and recording efficiency. As an initial step to resolve these issues with electrode performance, we have developed and characterized electrically-functional, low-Young's modulus, microcable-shaped neuroelectrodes and demonstrated electrophysiological recording functionality. The microcable geometry gives the electrodes a similar footprint to traditional wire and microwire neuroelectrodes, while reducing the difference in Young's modulus from nervous tissue by orders of magnitude. The electrodes are composed of PDMS and thin-film gold, affording them a high-level of compliance that is well suited for in vivo applications. The composite Young's modulus of the electrode was experimentally determined to be 1.81 ± 0.01 MPa. By incorporating a high-tear-strength silicone, Sylgard 186, the load at failure was increased by 92%, relative to that of the commonly used Sylgard 184. The microcable electrodes were also electromechanically tested, with measurable conductivity (220 kΩ) at an average 8% strain (n = 2) after the application of 200% strain. Electrophysiological recording is demonstrated by wrapping the electrode around a peripheral nerve, utilizing the compliance and string-like profile of the electrode for effective recording in nerve tissue.

  1. Thermal degradation in a trimodal PDMS network by 1H Multiple Quantum NMR

    Energy Technology Data Exchange (ETDEWEB)

    Giuliani, J R; Gjersing, E L; Chinn, S C; Jones, T V; Wilson, T S; Alviso, C T; Herberg, J L; Pearson, M A; Maxwell, R S


    Thermal degradation of a filled, crosslinked siloxane material synthesized from PDMS chains of three different average molecular weights and with two different crosslinking species has been studied by {sup 1}H Multiple Quantum (MQ) NMR methods. Multiple domains of polymer chains were detected by MQ NMR exhibiting Residual Dipolar Coupling (<{Omega}{sub d}>) values of 200 Hz and 600 Hz, corresponding to chains with high average molecular weight between crosslinks and chains with low average molecular weight between crosslinks or near the multifunctional crosslinking sites. Characterization of the <{Omega}{sub d}> values and changes in <{Omega}{sub d}> distributions present in the material were studied as a function of time at 250 C and indicates significant time dependent degradation. For the domains with low <{Omega}{sub d}>, a broadening in the distribution was observed with aging time. For the domain with high <{Omega}{sub d}>, increases in both the mean <{Omega}{sub d}> and the width in <{Omega}{sub d}> were observed with increasing aging time. Isothermal Thermal Gravimetric Analysis (TGA) reveals a 3% decrease in weight over 20 hours of aging at 250 C. Degraded samples also were analyzed by traditional solid state {sup 1}H NMR techniques and offgassing products were identified by Solid Phase MicroExtraction followed by Gas Chromatography-Mass Spectrometry (SPME GC-MS). The results, which will be discussed here, suggest that thermal degradation proceeds by complex competition between oxidative chain scissioning and post-curing crosslinking that both contribute to embrittlement.

  2. Dissonant Black Droplets and Black Funnels

    CERN Document Server

    Fischetti, Sebastian; Way, Benson


    A holographic field theory on a fixed black hole background has a gravitational dual represented by a black funnel or a black droplet. These states are "detuned" when the temperature of the field theory near the horizon does not match the temperature of the background black hole. In particular, the gravitational dual to the Boulware state must be a detuned solution. We construct detuned droplets and funnels dual to a Schwarzschild background and show that the Boulware phase is represented by a droplet. We also construct hairy black droplets associated to a low-temperature scalar condensation instability and show that they are thermodynamically preferred to their hairless counterparts.

  3. Kerr-Newman Black Hole In Quintessence

    CERN Document Server

    Xu, Zhaoyi


    We study the Kerr-Newman solutions of the Einstein-Maxwell equation in quintessence field around a black hole by Newman-Janis algorithm. From the horizon structure and stationary limit surfaces, we find that Kerr-Newman black hole exists an ergosphere with $r^{+} < r < r^{L}$, which is related to the parameters $\\omega$ and $\\alpha$. We obtain the general expression between $\\alpha$ and $\\omega$ if the cosmological horizon exists, in which for $\\omega=-1/2$, $\\alpha\\leq\\sqrt{2}/5$, and for $\\omega=-2/3$, $\\alpha\\leq 1/6$. For $\\omega=-2/3$, the result is same with rotational black hole in quintessence. The singularity of the black holes is the same with that of Kerr black hole. We also discuss the rotation velocity of the black holes on the equatorial plane for $\\omega =-2/3$ and $-1/2$.

  4. The thermal radiation from dynamic black holes

    Institute of Scientific and Technical Information of China (English)


    Using the related formula of dynamic black holes, the instantaneous radiation energy density of the general spherically symmetric charged dynamic black hole and the arbitrarily accelerating charged dynamic black hole is calculated. It is found that the instantaneous radiation energy density of black hole is always proportional to the quartic of the temperature of event horizon in the same direction. The proportional coefficient of generalized Stefan-Boltzmann is no longer a constant, and it becomes a dynamic coefficient that is related to the event horizon changing rate, space-time structure near event horizon and the radiation absorption coefficient of the black hole. It is shown that there should be an internal relation between the gravitational field around black hole and its thermal radiation.

  5. Non-abelian black string construction

    CERN Document Server

    Mazharimousavi, S Habib


    We present d+1-dimensional pure magnetic Yang-Mills (YM) black strings (or 1-branes) induced by the d-dimensional Einstein-Yang-Mills-Dilaton (EYMD) black holes. Incorporation of non-abelian fields in black strings, to our knowledge, has not been considered so far, for this reason we aim to fill this gap. Born-Infeld (BI) version of the YM field makes our starting point which goes to the standard YM field through a limiting procedure. The lifting from black holes to black strings, (with less number of fields) is by adding an extra, compact coordinate. This amounts to the change of horizon topology from S^{d-2} to a product structure. Our black string in 5-dimensions is a rather special one, with uniform Hawking temperature and non-asymptotically flat Local isometry in the abelian limit with the space of colliding plane waves is discussed.

  6. Black Feminism: An Integrated Review of Literature. (United States)

    Love, Katie L


    This study presents a systematic literature review exploring the uses and potential benefits of Black Feminism in nursing research. Black Feminism may benefit knowledge development for nursing in a variety of ways, such as illuminating the multifaceted factors of Black women's identities in helping scholars move away from generalization of experiences, to improve understanding of health disparities, and making such changes by broadening the social consciousness of the nurse researchers, who are predominantly White. Discrimination in health disparities may be deconstructed if the focus is placed on asking different research questions and offering different interventions with the social structures that contributes to such actions. When Black Feminism guides the research method (including research questions and analysis), the accuracy of representing the experiences of Black women is increased. In this research, Black Feminism highlights experience, coping mechanisms, spiritual values, a tradition of strength, and a holistic view of identity.

  7. Black Silicon Solar Cells with Black Ribbons

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io;


    We present the combination of mask-less reactive ion etch (RIE) texturing and blackened interconnecting ribbons as a method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon made by mask-less reactive ion etching has total, average...... reflectance below 0.5% across a 156x156 mm2 silicon (Si) wafer. Black interconnecting ribbons were realized by oxidizing copper resulting in reflectance below 3% in the visible wavelength range. Screen-printed Si solar cells were realized on 156x156 mm2 black Si substrates with resulting efficiencies...... in the range 15.7-16.3%. The KOH-textured reference cell had an efficiency of 17.9%. The combination of black Si and black interconnecting ribbons may result in aesthetic, all-black panels based on conventional, front-contacted silicon solar cells....

  8. Poverty among Young Children in Black Immigrant, US-Born Black, and Non-Black Immigrant Families: The Role of Familial Contexts. Discussion Paper Series. DP 2010-02 (United States)

    Thomas, Kevin J. A.


    This study examines how familial contexts affect poverty disparities between the children of immigrant and US-born Blacks, and among Black and non-Black children of immigrants. Despite lower gross child poverty rates in immigrant than US-born Black families, accounting for differences in family structure reveals that child poverty risks among…

  9. Geothermal structure of the eastern Black Sea basin and the eastern Pontides orogenic belt: Implications for subduction polarity of Tethys oceanic lithosphere

    Directory of Open Access Journals (Sweden)

    Nafiz Maden


    Full Text Available The numerical results of thermal modeling studies indicate that the lithosphere is cold and strong beneath the Black Sea basin. The thermal lithospheric thickness increases southward from the eastern Pontides orogenic belt (49.4 km to Black Sea basin (152.2 km. The Moho temperature increases from 367 °C in the trench to 978 °C in the arc region. The heat flow values for the Moho surface change between 16.4 mW m−2 in the Black Sea basin and 56.9 mW m−2 in the eastern Pontides orogenic belt. Along the southern Black Sea coast, the trench region has a relatively low geothermal potential with respect to the arc and back-arc region. The numerical studies support the existence of southward subduction beneath the Pontides during the late Mesozoic–Cenozoic.

  10. Black hole accretion discs


    Lasota, Jean-Pierre


    This is an introduction to models of accretion discs around black holes. After a presentation of the non-relativistic equations describing the structure and evolution of geometrically thin accretion discs we discuss their steady-state solutions and compare them to observation. Next we describe in detail the thermal-viscous disc instability model and its application to dwarf novae for which it was designed and its X-ray irradiated-disc version which explains the soft X--ray transients, i.e. ou...

  11. Selected data for wells and test holes used in structure-contour maps of the Inyan Kara Group, Minnekahta Limestone, Minnelusa Formation, Madison Limestone, and Deadwood Formation in the Black Hills area, South Dakota (United States)

    Carter, J.M.


    This report presents selected data on wells and test holes that were used in the construction of structure-contour maps of selected formations that contain major aquifers in the Black Hills area of western South Dakota. Altitudes of the top of the Inyan Kara Group, Minnekahta Limestone, Minnelusa Formation, Madison Limestone, and Deadwood Formation are presented for the wells and test holes presented in this report.

  12. Analysis of black pepper volatiles by solid phase microextraction-gas chromatography: A comparison of terpenes profiles with hydrodistillation. (United States)

    Jeleń, Henryk H; Gracka, Anna


    Solid phase microextraction (SPME) is widely used in food flavor compounds analysis in majority for profiling volatile compounds. Based on such profiles conclusions are often drawn concerning the percentage composition of volatile compounds in particular food, spices or raw materials. This paper focuses on the usefulness of SPME for the profiling of volatile compounds from spices using black pepper as an example. SPME profiles obtained in different analytical conditions were compared to the profile of pepper volatiles obtained using hydrodistillation in Clevenger apparatus. The profiles of both monoterpenes and sesquiterpenes of black pepper were highly dependent on sample weight (0.1 and 1g samples were tested), and extraction time (durations from 2 to 120min were tested), regardless of the SPME fiber used (PDMS and CAR/PDMS coatings were used). The characteristic phenomenon for extraction from dry ground pepper was the decrease of monoterpenes % share in volatiles with increasing extraction times, whereas at the same time the % contents of sesquiterpenes increased. Addition of water to ground pepper substantially changed extraction kinetics and mutual proportions of mono to sesquiterpenes compared to dry samples by minimizing changes in mono- to sesquiterpenes ratio in different extraction times. Obtained results indicate that SPME can be a fast extraction method for volatiles of black pepper. Short extraction times (2-10min) in conjunction with the fast GC analysis (2.1min) proposed here may offer fast alternative to hydrodistillation allowing black pepper terpenes characterization.

  13. Effect of wettability and surface roughness on the adhesion properties of collagen on PDMS films treated by capacitively coupled oxygen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Juárez-Moreno, J.A. [Centro de Investigación Científica de Yucatán, Calle 43 No. 130, Col. Chuburna de Hidalgo C.P., 97200 Mérida, Yucatán (Mexico); Ávila-Ortega, A. [Facultad de Ingeniería Química—UADY, Periférico Norte Kilómetro 33.5, Col. Chuburna de Hidalgo Inn, C.P. , 97203 Mérida, Yucatán (Mexico); Oliva, A.I. [Centro de Investigación y de Estudios Avanzados del IPN–Unidad Mérida, Km. 6 Antigua carretera a Progreso Apdo. Postal 73, Cordemex, 97310 Mérida, Yucatán (Mexico); Avilés, F. [Centro de Investigación Científica de Yucatán, Calle 43 No. 130, Col. Chuburna de Hidalgo C.P., 97200 Mérida, Yucatán (Mexico); Cauich-Rodríguez, J.V., E-mail: [Centro de Investigación Científica de Yucatán, Calle 43 No. 130, Col. Chuburna de Hidalgo C.P., 97200 Mérida, Yucatán (Mexico)


    Highlights: • Plasma treatment was used as an adhesive tool for PDMS/collagen composite preparation. • Response surface methodology was used for statistical optimization. • A microscopic roughness can also lead to a mechanical interlocking between materials. • Hydroxyl groups on the PDMS surface contribute to the enhanced chemical interactions. • PDMS/collagen composite obtained by plasma treatment exhibited higher peel strength. - Abstract: Direct chemical bonding of biomolecules to the surface of chemically inert polymers such as polydimethylsiloxane (PDMS) is not easily achieved. Therefore, pre-activation of such materials, followed by attachment of the biomolecule is necessary. This paper describes a procedure to functionalize a PDMS surface by oxygen-based plasma followed by the adhesion of collagen type I for the preparation of adhesive-free bilayer composite intended as skin substitute. Plasma treatments between 40 and 120 W for 5 to 15 min were used and the extent of surface modification was followed by contact angle, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and adhesion test. It was found that as the plasma power and time were increased, PDMS contact angle decreased while surface roughness increased as revealed by SEM and AFM. The formation of oxygen-containing functional groups at the surface was detected by FTIR. T-peel tests, performed on PDMS treated at 80 W/13 min and covered with collagen showed maximum peel strength of 0.1 N/mm which was 3 times higher than that measured for the untreated bilayer composite. The observed enhancement in the adhesion strength was attributed to the increased mechanical interlocking driven by the increased roughness and the formation of hydrophilic functional groups.

  14. Black holes with surrounding matter in scalar-tensor theories. (United States)

    Cardoso, Vitor; Carucci, Isabella P; Pani, Paolo; Sotiriou, Thomas P


    We uncover two mechanisms that can render Kerr black holes unstable in scalar-tensor gravity, both associated with the presence of matter in the vicinity of the black hole and the fact that this introduces an effective mass for the scalar. Our results highlight the importance of understanding the structure of spacetime in realistic, astrophysical black holes in scalar-tensor theories.

  15. Joint Formation of Supermassive Black Holes and Galaxies


    Martin G. Haehnelt(IoA/KICC, Cambridge)


    The tight correlation between black hole mass and velocity dispersion of galactic bulges is strong evidence that the formation of galaxies and supermassive black holes are closely linked. I review the modeling of the joint formation of galaxies and their central supermassive black holes in the context of the hierarchical structure formation paradigm.

  16. Black Holes and Exotic Spinors

    Directory of Open Access Journals (Sweden)

    J. M. Hoff da Silva


    Full Text Available Exotic spin structures are non-trivial liftings, of the orthogonal bundle to the spin bundle, on orientable manifolds that admit spin structures according to the celebrated Geroch theorem. Exotic spin structures play a role of paramount importance in different areas of physics, from quantum field theory, in particular at Planck length scales, to gravity, and in cosmological scales. Here, we introduce an in-depth panorama in this field, providing black hole physics as the fount of spacetime exoticness. Black holes are then studied as the generators of a non-trivial topology that also can correspond to some inequivalent spin structure. Moreover, we investigate exotic spinor fields in this context and the way exotic spinor fields branch new physics. We also calculate the tunneling probability of exotic fermions across a Kerr-Sen black hole, showing that the exotic term does affect the tunneling probability, altering the black hole evaporation rate. Finally we show that it complies with the Hawking temperature universal law.

  17. PDMS-SiO{sub 2}-TiO{sub 2}-CaO hybrid materials – Cytocompatibility and nanoscale surface features

    Energy Technology Data Exchange (ETDEWEB)

    Almeida, J. Carlos [CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Wacha, András [Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudósok körútja 2, Budapest 1117 (Hungary); Gomes, Pedro S.; Fernandes, M. Helena R. [Laboratory for Bone Metabolism and Regeneration, Faculdade de Medicina Dentária, Universidade do Porto (Portugal); Fernandes, M. Helena Vaz [CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal); Salvado, Isabel M. Miranda, E-mail: [CICECO - Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro, 3810-193 Aveiro (Portugal)


    Two PDMS-SiO{sub 2}-TiO{sub 2}-CaO porous hybrid materials were prepared using the same base composition, precursors, and solvents, but following two different sol-gel procedures, based on the authors' previous works where for the first time, in this hybrid system, calcium acetate was used as calcium source. The two different procedures resulted in monolithic materials with different structures, microstructures, and surface wettability. Even though both are highly hydrophobic (contact angles of 127.2° and 150.6°), and present different filling regimes due to different surface topographies, they have demonstrated to be cytocompatible when tested with human osteoblastic cells, against the accepted idea that high-hydrophobic surfaces are not suitable to cell adhesion and proliferation. At the nanoscale, the existence of hydrophilic silica domains containing calcium, where water molecules are physisorbed, is assumed to support this capability, as discussed. - Highlights: • Two hybrid materials were prepared following two different sol-gel procedures. • Both are highly hydrophobic but demonstrated to be cytocompatible. • Different filling regimes were observed.

  18. Electrodynamics of Black Holes in STU Supergravity

    CERN Document Server

    Cvetic, M; Pope, C N; Saleem, Z H


    External magnetic fields can probe the composite structure of black holes in string theory. With this motivation we study magnetised four-charge black holes in the STU model, a consistent truncation of maximally supersymmetric supergravity with four types of electromagnetic fields. We employ solution generating techniques to obtain Melvin backgrounds, and black holes in these backgrounds. For an initially electrically charged static black hole immersed in magnetic fields, we calculate the resultant angular momenta and analyse their global structure. Examples are given for which the ergoregion does not extend to infinity. We calculate magnetic moments and gyromagnetic ratios via Larmor's formula. Our results are consistent with earlier special cases. A scaling limit and associated subtracted geometry in a single surviving magnetic field is shown to lift to $AdS_3\\times S^2$. Magnetizing magnetically charged black holes give static solutions with conical singularities representing strings or struts holding the ...


    Institute of Scientific and Technical Information of China (English)

    Xia Zhan; Ji-ding Li; Jian Chen; Jun-qi Huang


    Thin-film zeolite-filled silicone/PVDF composite membranes were fabricated by incorporating zeolite particles into PDMS (poly(dimethylsiloxane)) membranes. The morphology of zeolite particles and zeolite filled silicone composite membranes were characterized by SEM. The zeolite-filled PDMS/PVDF composite membranes were applied for the pervaporation of ethanol/water mixtures and showed higher flux compared with that reported in literatures. The effect of zeolite loading and Si/Al ratio of zeolite particles on pervaporation performance of ethanol/water mixtures was investigated. With the increase of zeolite loading from 10% to 30%, the total flux increased significantly from 265.0 g/(m~2h) to 820.7 g/(m~2h) with 5 wt% ethanol feed concentration at 50℃, and the separation factor increased from 11.3 to 13.7. The effects of operation temperature and ethanol feed concentration on pervaporation performance were also studied. As the temperature increased from 40℃ to 80℃, the separation factor varied from 12.1 to 13.7 which maintained the maximum value at 50℃, and the total flux increased exponentially from 435.5 g/(m~2h) to 2993.8 g/(m~2h) with 30% zeolite loading. Besides, the zeolite filled PDMS/PVDF composite membrane with 30% zeolite loading was ethanol perm-selective over a wide range of ethanol feed concentration (5 wt%-90 wt%), and especially showed excellent pervaporation performance in the low concentration range.

  20. In vitro blood flow in a rectangular PDMS microchannel: experimental observations using a confocal micro-PIV system. (United States)

    Lima, Rui; Wada, Shigeo; Tanaka, Shuji; Takeda, Motohiro; Ishikawa, Takuji; Tsubota, Ken-ichi; Imai, Yohsuke; Yamaguchi, Takami


    Progress in microfabricated technologies has attracted the attention of researchers in several areas, including microcirculation. Microfluidic devices are expected to provide powerful tools not only to better understand the biophysical behavior of blood flow in microvessels, but also for disease diagnosis. Such microfluidic devices for biomedical applications must be compatible with state-of-the-art flow measuring techniques, such as confocal microparticle image velocimetry (PIV). This confocal system has the ability to not only quantify flow patterns inside microchannels with high spatial and temporal resolution, but can also be used to obtain velocity measurements for several optically sectioned images along the depth of the microchannel. In this study, we investigated the ability to obtain velocity measurements using physiological saline (PS) and in vitro blood in a rectangular polydimethysiloxane (PDMS) microchannel (300 microm wide, 45 microm deep) using a confocal micro-PIV system. Applying this combination, measurements of trace particles seeded in the flow were performed for both fluids at a constant flow rate (Re = 0.02). Velocity profiles were acquired by successive measurements at different depth positions to obtain three-dimensional (3-D) information on the behavior of both fluid flows. Generally, the velocity profiles were found to be markedly blunt in the central region, mainly due to the low aspect ratio (h/w = 0.15) of the rectangular microchannel. Predictions using a theoretical model for the rectangular microchannel corresponded quite well with the experimental micro-PIV results for the PS fluid. However, for the in vitro blood with 20% hematocrit, small fluctuations were found in the velocity profiles. The present study clearly shows that confocal micro-PIV can be effectively integrated with a PDMS microchannel and used to obtain blood velocity profiles along the full depth of the microchannel because of its unique 3-D optical sectioning ability

  1. Problema de calibración de mercado y estructura implícita del modelo de bonos de Black-Cox || Market Calibration Problem and the Implied Structure of the Black-Cox Bond Model

    Directory of Open Access Journals (Sweden)

    Santana Jiménez, Lisette Josefina


    Full Text Available El principal resultado de este artículo consiste en la resolución del problema inverso del modelo de Black-Cox (1976, usando el método propuesto por Sukhomlin (2007. Se parte del enfoque retrógrado (backward para obtener una expresión exacta de la volatilidad implícita en función de parámetros cuantificables con datos de mercado y de variables conocidas. Se descubre la existencia de dos valores de la volatilidad para un activo subyacente en elmodelo referido, lo que indica que las asunciones tradicionales no lo definen de manera unívoca. Se encuentra la causa de que el modelo de Black-Cox contenga dos valores de la volatilidad. Además, se lleva a cabo una simulación, afin de verificar, numéricamente, que la expresión obtenida para la volatilidad es la inversión de la fórmula que representa la probabilidad de que la firma no alcance un nivel de insolvencia antes del tiempo de madurez de la deuda. Finalmente, se resuelve el problema de calibración de mercadodesde el punto de vista directo (forward, encontrándose una expresión que resulta de mayor utilidad para los agentes de mercado. || The main result of this paper consists in the resolution of the inverse problem for the Black-Cox (1976 model, using the method proposed by Sukhomlin (2007. Based on the backward approach, we obtain an exact expression of the implied volatility expressed as a function of quantifiable market parameters and known variables. We discover the existence of two values of the volatility for an underlying asset, in the referred model, which means that the model's traditional assumptions do not define it univocally. We findthe cause that the Black-Cox model contains two values of the volatility. Besides, we carry out a simulation in order to verify, numerically, that our volatility expression is in fact the inversion of the formula that represents the probability that the firm has not reached the reorganization boundary before the debt expires. Finally, we

  2. Single particle studies of black liquor gasification under pressurized conditions

    Energy Technology Data Exchange (ETDEWEB)

    Whitty, K.; Backman, R.; Hupa, M.; Backman, P.; Ek, P.; Hulden, S.T.; Kullberg, M.; Sorvari, V.


    The purpose of this project is to provide experimental data relevant to pressurized black liquor gasification concepts. Specifically, the following two goals will be achieved: Data on swelling, char yields and component release during pressurized pyrolysis of small samples of black liquor will be obtained. The reactivity and physical behavior of single black liquor droplets during simultaneous pyrolysis and gasification will be investigated. The structure and composition of black liquor char during formation and conversion will be studied. (orig.)

  3. The Black Black Woman and the Black Middle Class. (United States)

    Jeffers, Trellie


    Reprint of a 1973 article that describes the discrimination that particularly dark-skinned Black women suffer, especially at the hands of a color-conscious Black middle class. Calls for dark women to look to the African appearance and working-class roots as sources of pride and strength. (GC)

  4. Black holes and warped spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, W.J. III


    Black holes (BHs) and their warping effect on spacetime are described, beginning with a discussion on stellar evolution that includes white dwarfs, supernovas and neutron stars. The structure of static, rotating, and electrically charged BHs are considered, as well as the general theory of relativity, quantum mechanics, the Einstein-Rosen bridge, and wormholes in spacetime. Attention is also given to gravitational lenses, various space geometries, quasars, Seyfert galaxies, supermassive black holes, the evaporation and particle emission of BHs, and primordial BHs, including their temperature and lifetime.

  5. Preparing mono-dispersed liquid core PDMS microcapsules from thiol–ene–epoxy-tailored flow-focusing microfluidic devices

    DEFF Research Database (Denmark)

    Mazurek, Piotr Stanislaw; Daugaard, Anders Egede; Skolimowski, Maciej;


    An applied dual-cure system based on thiol–ene and thiol–epoxy “click chemistry” reactions was proved to be an extremely effective and easy to use tool for preparing microfluidic chips, thereby allowing for precise control over material properties and providing the possibility of covalently bonding...... of compositions in relation to high hydrophilicity and hydrophobicity. An obtained microfluidic device was subsequently used in order to produce PDMS microcapsules of very narrow size distribution and which contained various common liquids, such as water and ethanol, as well as an ionic liquid 2...

  6. Uniform droplet splitting and detection using Lab-on-Chip flow cytometry on a microfluidic PDMS device

    DEFF Research Database (Denmark)

    Kunstmann-Olsen, Casper; Hanczyc, Martin; Hoyland, James


    A PDMS chip is fabricated using soft lithography and applied to investigate the formation and division of nitrobenzene (NB) droplets in a two-phase system stabilized by oleic acid. Using an integrated on-chip flow cytometer setup, effected with optical fibers, droplet size distributions...... are analyzed in situ based on optical signal intensities. By controlling the hydrodynamic flow focusing, uniform droplets of sizes between 100 μm and 300 μm are created with precise size control. Cross-flow shearing allows one to divide these droplets into anything from 2 to 9 individual droplets, depending...

  7. Assessment of PDMS-water partition coefficients: implications for passive environmental sampling of hydrophobic organic compounds (United States)

    DiFilippo, Erica L.; Eganhouse, Robert P.


    Solid-phase microextraction (SPME) has shown potential as an in situ passive-sampling technique in aquatic environments. The reliability of this method depends upon accurate determination of the partition coefficient between the fiber coating and water (Kf). For some hydrophobic organic compounds (HOCs), Kf values spanning 4 orders of magnitude have been reported for polydimethylsiloxane (PDMS) and water. However, 24% of the published data examined in this review did not pass the criterion for negligible depletion, resulting in questionable Kf values. The range in reported Kf is reduced to just over 2 orders of magnitude for some polychlorinated biphenyls (PCBs) when these questionable values are removed. Other factors that could account for the range in reported Kf, such as fiber-coating thickness and fiber manufacturer, were evaluated and found to be insignificant. In addition to accurate measurement of Kf, an understanding of the impact of environmental variables, such as temperature and ionic strength, on partitioning is essential for application of laboratory-measured Kf values to field samples. To date, few studies have measured Kf for HOCs at conditions other than at 20 degrees or 25 degrees C in distilled water. The available data indicate measurable variations in Kf at different temperatures and different ionic strengths. Therefore, if the appropriate environmental variables are not taken into account, significant error will be introduced into calculated aqueous concentrations using this passive sampling technique. A multiparameter linear solvation energy relationship (LSER) was developed to estimate log Kf in distilled water at 25 degrees C based on published physicochemical parameters. This method provided a good correlation (R2 = 0.94) between measured and predicted log Kf values for several compound classes. Thus, an LSER approach may offer a reliable means of predicting log Kf for HOCs whose experimental log Kf values are presently unavailable. Future

  8. Black hole as a wormhole factory (United States)

    Kim, Sung-Won; Park, Mu-In


    There have been lots of debates about the final fate of an evaporating black hole and the singularity hidden by an event horizon in quantum gravity. However, on general grounds, one may argue that a black hole stops radiation at the Planck mass (ħc / G) 1 / 2 ∼10-5 g, where the radiated energy is comparable to the black hole's mass. And also, it has been argued that there would be a wormhole-like structure, known as "spacetime foam", due to large fluctuations below the Planck length (ħG /c3) 1 / 2 ∼10-33 cm. In this paper, as an explicit example, we consider an exact classical solution which represents nicely those two properties in a recently proposed quantum gravity model based on different scaling dimensions between space and time coordinates. The solution, called "Black Wormhole", consists of two different states, depending on its mass parameter M and an IR parameter ω: For the black hole state (with ωM2 > 1 / 2), a non-traversable wormhole occupies the interior region of the black hole around the singularity at the origin, whereas for the wormhole state (with ωM2 Censorship" by the existence of a wormhole-like structure which protects the naked singularity even after the black hole evaporation. One could understand the would-be wormhole inside the black hole horizon as the result of microscopic wormholes created by "negative" energy quanta which have entered the black hole horizon in Hawking radiation process; the quantum black hole could be a wormhole factory! It is found that this speculative picture may be consistent with the recent " ER = EPR " proposal for resolving the black hole entanglement debates.

  9. Effect of weight fraction of carbon black and number of plies of E-glass fiber to reflection loss of E-glass/ripoxy composite for radar absorbing structure (RAS) (United States)

    Widyastuti, Ramadhan, Rizal; Ardhyananta, Hosta; Zainuri, Mochamad


    Nowadays, studies on investigating radar absorbing structure (RAS) using fiber reinforced polymeric (FRP) composite materials are becoming popular research field because the electromagnetic properties of FRP composites can be tailored effectively by just adding some electromagnetic powders, such as carbon black, ferrite, carbonyl iron, and etc., to the matrix of composites. The RAS works not only as a load bearing structure to hold the antenna system, but also has the important function of absorbing the in-band electromagnetic wave coming from the electromagnetic energy of tracking systems. In this study, E-glass fiber reinforced ripoxy resin composite was fabricated by blending the conductive carbon black (Ketjenblack EC300J) with the binder matrix of the composite material and maximizing the coefficient of absorption more than 90% (more than -10 dB) within the X-band frequency (8 - 12 GHz). It was measured by electrical conductivity (LCR meter) and vector network analyzer (VNA). Finally, the composite RAS with 0.02 weight fraction of carbon black and 4 plies of E-glass fiber showed thickness of 2.1 mm, electrical conductivity of 8.33 × 10-6 S/m, and maximum reflection loss of -27.123 dB, which can absorb more than 90% of incident EM wave throughout the entire X-band frequency range, has been developed.

  10. Lee-Wick Black Holes

    CERN Document Server

    Bambi, Cosimo; Wang, Yixu


    We derive and study an approximate static vacuum solution generated by a point-like source in a higher derivative gravitational theory with a pair of complex conjugate ghosts. The gravitational theory is local and characterized by a high derivative operator compatible with Lee-Wick unitarity. In particular, the tree-level two-point function only shows a pair of complex conjugate poles besides the massless spin two graviton. We show that singularity-free black holes exist when the mass of the source $M$ exceeds a critical value $M_{\\rm crit}$. For $M > M_{\\rm crit}$ the spacetime structure is characterized by an outer event horizon and an inner Cauchy horizon, while for $M = M_{\\rm crit}$ we have an extremal black hole with vanishing Hawking temperature. The evaporation process leads to a remnant that approaches the zero-temperature extremal black hole state in an infinite amount of time.

  11. Lee-Wick black holes (United States)

    Bambi, Cosimo; Modesto, Leonardo; Wang, Yixu


    We derive and study an approximate static vacuum solution generated by a point-like source in a higher derivative gravitational theory with a pair of complex conjugate ghosts. The gravitational theory is local and characterized by a high derivative operator compatible with Lee-Wick unitarity. In particular, the tree-level two-point function only shows a pair of complex conjugate poles besides the massless spin two graviton. We show that singularity-free black holes exist when the mass of the source M exceeds a critical value Mcrit. For M >Mcrit the spacetime structure is characterized by an outer event horizon and an inner Cauchy horizon, while for M =Mcrit we have an extremal black hole with vanishing Hawking temperature. The evaporation process leads to a remnant that approaches the zero-temperature extremal black hole state in an infinite amount of time.

  12. Black Germanium fabricated by reactive ion etching (United States)

    Steglich, Martin; Käsebier, Thomas; Kley, Ernst-Bernhard; Tünnermann, Andreas


    A reactive ion etching technique for the preparation of statistical "Black Germanium" antireflection surfaces, relying on self-organization in a Cl2 etch chemistry, is presented. The morphology of the fabricated Black Germanium surfaces is the result of a random lateral distribution of pyramidal etch pits with heights around (1450 ± 150) nm and sidewall angles between 80° and 85°. The pyramids' base edges are oriented along the crystal directions of Germanium, indicating a crystal anisotropy of the etching process. In the Vis-NIR, the tapered Black Germanium surface structure suppresses interface reflection to structure in optoelectronics and IR optics.

  13. Flexible-textured polydimethylsiloxane antireflection structure for enhancing omnidirectional photovoltaic performance of Cu(In,Ga)Se2 solar cells. (United States)

    Kuo, Shou-Yi; Hsieh, Ming-Yang; Han, Hau-Vei; Lai, Fang-I; Chuang, Tsung-Yeh; Yu, Peichen; Lin, Chien-Chung; Kuo, Hao-Chung


    Because of the Sun's movement across the sky, broadband and omnidirectional light harvesting is a major development in photovoltaic technology. This study reports the fabrication and characterization of flexible-textured polydimethylsiloxane (PDMS) film on Cu(In,Ga)Se2 (CIGS) solar cells, which is one of the simplest and cheapest peel-off processes for fabricating a three-dimensional structure. A cell containing a textured PDMS film enhanced the short-circuit current density from 22.12 to 23.93 mA/cm2 in a simulated one-sun scenario. The omnidirectional antireflection of CIGS solar cells containing various PDMS films is also investigated. This study uses an angle-resolved reflectance spectroscope to investigate the omnidirectional and broadband optical properties of the proposed PDMS film. This improvement in light harvesting is attributable to the scattering of the PDMS film and the gradual refractive index profile between the PDMS microstructures and air. The flexible-textured PDMS film is suitable for creating an antireflective coating for a diverse range of photovoltaic devices.

  14. Complex communication signals: the case of the Blue-black Grassquit Volatinia jacarina (Aves, Emberizidae song. Part I - A structural analysis

    Directory of Open Access Journals (Sweden)

    Hernán Fandiño-Mariño


    Full Text Available The song of the Blue-black Grassquit Volatinia jacarina is different for every individual and the structural differences between individuals are quite complex. Samples of songs from different Brazilian localities, as well as from Venezuela and Mexico, were studied through a comparative analysis of their sonograms. From the structural point of view, the results show a song composed of a single note that is compacted in a ''window'' between 2 and 13 kHz and rarely occupying more than half of a second. The note is essentially pure and is repeatedly uttered with a high level of fidelity. A global frequency modulation decreases from the beginning to the end of the song. The main song components are referred to as ''Blocks'' and are of three types: ''Vibrations'' (Buzzes or Vibratos, ''Arabesques'' (complex notes and ''Isolated Modulations'' (simple syllables. Among other characteristics are double voices, which are quite diverse and probably function as codes for individual recognition. This song is considered a special case where a signature system has been developed to a high level of inter-individual variability.O canto do Tiziu Volatinia jacarina é único para cada indivíduo e as diferenças estruturais entre um e outro indivíduo são muito complexas. Cantos gravados em diversos lugares do Brasil e alguns da Venezuela e do México foram estudados através de uma análise comparativa dos seus sonogramas. Do ponto de vista estrutural, os resultados mostram que o canto é constituído por uma nota única que se encontra compactada numa ''janela'' entre 2 e 13 kHz e raramente ultrapassa meio segundo de duração. A nota, essencialmente pura, é repetida com alto grau de fidelidade entre uma emissão e outra. Constata-se uma modulação de freqüência global descendente do início ao fim do canto. Os principais componentes do canto do Tiziu foram denominados ''Blocos'' e são basicamente de três tipos: as ''Vibrações'' (Buzzes ou Vibratos, os

  15. Predictive Modeling of Black Spruce (Picea mariana (Mill. B.S.P. Wood Density Using Stand Structure Variables Derived from Airborne LiDAR Data in Boreal Forests of Ontario

    Directory of Open Access Journals (Sweden)

    Bharat Pokharel


    Full Text Available Our objective was to model the average wood density in black spruce trees in representative stands across a boreal forest landscape based on relationships with predictor variables extracted from airborne light detection and ranging (LiDAR point cloud data. Increment core samples were collected from dominant or co-dominant black spruce trees in a network of 400 m2 plots distributed among forest stands representing the full range of species composition and stand development across a 1,231,707 ha forest management unit in northeastern Ontario, Canada. Wood quality data were generated from optical microscopy, image analysis, X-ray densitometry and diffractometry as employed in SilviScan™. Each increment core was associated with a set of field measurements at the plot level as well as a suite of LiDAR-derived variables calculated on a 20 × 20 m raster from a wall-to-wall coverage at a resolution of ~1 point m−2. We used a multiple linear regression approach to identify important predictor variables and describe relationships between stand structure and wood density for average black spruce trees in the stands we observed. A hierarchical classification model was then fitted using random forests to make spatial predictions of mean wood density for average trees in black spruce stands. The model explained 39 percent of the variance in the response variable, with an estimated root mean square error of 38.8 (kg·m−3. Among the predictor variables, P20 (second decile LiDAR height in m and quadratic mean diameter were most important. Other predictors describing canopy depth and cover were of secondary importance and differed according to the modeling approach. LiDAR-derived variables appear to capture differences in stand structure that reflect different constraints on growth rates, determining the proportion of thin-walled earlywood cells in black spruce stems, and ultimately influencing the pattern of variation in important wood quality attributes

  16. Preparation and characterization of PDMS/PMMA core-shell latex particles having functional group in surface layer%表层功能化PDMS/PMMA核壳乳胶粒子的制备与表征

    Institute of Scientific and Technical Information of China (English)

    张国青; 刘喜军


    In this paper, the polydimethyl siloxane/polymethyl methacrylate(PDMS/PMMA)core-shell latex particles (-320 nm)respectively with itaconic acid(ITA),maleic anhydride(MAH)and glycidyl methacrylate(GMA) as functional monomer in surface layer were successfully synthesized employing pre-emulsification semi-continuous process by seeded emulsion polymerization method. Octamethyl cyclotetrasiloxane(D 4 )and Tetravinyl tetramethyl cyelotetrasiloxane as the main monomer were compounded to form PDMS core latex particles with methyl triethoxysilane(MTES)as cross-linking agent. The effects of the reaction time, surfactant and catalyst concentration, and the ratio of D 4 and VD 4 on the polymerization system were studied, and the optimal synthesizing process of PDMS core latex particles was defined.By laser particle size analyzer, Fourier transform infrared spectrometer and transmission electron microscopy analysis showed that the core monomer conversion was nearly 85%and PDMS latex particle size was at about 290 nm when the reaction time was 10 h,surfactant concentration was 5.3%, catalyst concentration was 5.3%,and D4∶VD4=4∶1.%分别以衣康酸(ITA)、马来酸酐(MAH)和甲基丙烯酸缩水甘油酯(GMA)为功能单体,采用预乳化半连续工艺通过种子乳液聚合方法成功合成了表层功能化的聚二甲基硅氧烷/聚甲基丙烯酸甲酯(PDMS/PMMA)核壳乳胶粒子(~320 nm)。PDMS核乳胶粒子以八甲基环四硅氧烷(D 4)和四甲基四乙烯基环四硅氧烷(VD 4)为单体、甲基三乙氧基硅烷(MTES)为交联剂构建而成,实验研究了反应时间、乳化剂和催化剂用量、单体D 4与VD 4比例对聚合体系的影响,并确定了PDMS核乳胶粒子合成最佳工艺。通过激光粒度分析仪、傅里叶变换红外光谱仪、透射电子显微镜等分析表明:当反应时间为10 h、乳化剂用量为核单体总量的5.3%、催化剂用量为核单体总量的5.3%

  17. Pengaruh Jenis Katalis terhadap Kekuatan Tarik dan Stabilitas Termal Polidimetilsiloksan (PDMS untuk Lapisan Pelindung Baja AISI 1050

    Directory of Open Access Journals (Sweden)

    Muhammad Atha Illah


    Full Text Available Polisiloksan adalah polimer yang paling banyak digunakan sebagai lapisan pelindung pada baja karena memiliki sifat yang unggul dibandingkan polimer lain. Polidimetilsiloksan (PDMS adalah salah satu  keluarga polisiloksan yang paling banyak digunakan dalam bentuk karet Room-Temperature Vulcanization (RTV. Pada penelitian ini, PDMS divulkanisir menggunakan katalis Bluesil Catalyst 60R (komersial, NaOH 2 M, H2SO4 2 M, Poli aminoamid, dan Red 683 (komersial dengan variasi komposisi masing-masing katalis 2 - 10 wt%. Katalis yang bisa membentuk karet silikon hanyalah Bluesil Catalyst 60R dan Red 683. Pada percobaannya, waktu pematangan semakin cepat seiring bertambahnya komposisi katalis yang diberikan. Elastisitas karet silikon sangat tinggi, karena sifat inilah karet silikon tidak pecah ketika diuji fleksural hingga 180o. Hasil pengujian tarik menunjukkan karet dengan Bluesil Catalyst 60R 6wt% memiliki kekuatan tarik paling optimum yaitu 1,625 MPa. Penambahan Bluesil Catalyst 60R 10wt% juga memberikan nilai kestabilan termal  karet silikon yang paling baik, berat sisanya adalah 39,172 % pada temperatur 800oC.

  18. ZnO–PDMS Nanohybrids: A Novel Optical Sensing Platform for Ethanol Vapor Detection at Room Temperature

    KAUST Repository

    Klini, Argyro


    © 2014 American Chemical Society. A new optical gas sensor platform based on highly luminescent ZnO-polymer nanohybrids is demonstrated. The nanohybrids consist of ZnO nanoparticles, typically 125 (±25) nm in size, dispersed in an inert cross-linked polydimethylsiloxane (PDMS) matrix. Upon exposure to ethanol-enriched air at room temperature, the nanocomposites exhibit a clear increase in their photoluminescence (PL) emission, which shows a nearly Langmuir dependence on the alcohol vapor pressure. The response time is on the order of 50 s, particularly at low ethanol concentrations. The limit of ethanol vapor detection (LOD) is as low as 0.4 Torr, while the sensor remains unaffected by the presence of water vapor, demonstrating the potential of the ZnO-PDMS system as an optical gas sensing device. The interaction of the ZnO nanoparticles with molecular oxygen plays an essential role on the overall performance of the sensor, as shown in comparative experiments performed in the presence and absence of atmospheric air. Notably, O2 was found to be quite effective in accelerating the sensor recovery process compared to N2 or vacuum.

  19. Robust superhydrophobic PDMS/camphor based composite coatings with self-cleaning and self-healing properties (United States)

    Mitra, Sushanta; Sahoo, Bichitra; Nanda, Sonil; Kozinski, Janusz


    We report a novel process for the preparation of self-cleaning polymer composite with self-healing ability to self-repair from chemical and mechanical damages using readily available materials like Polydimethylsiloxane (PDMS) and camphor soot particles. When the camphor soot particles loading attained a critical level, the composite coating on glass and stainless steel surfaces reveals self-cleaning property with water contact angle of 1710. We also demonstrate that any degradation of its surface energy under the oxygen plasma etching can be recuperated, illustrating that the obtained superhydrophobic surface has a good self-healing ability. The fabricated PDMS/Camphor soot hybrid coating exhibited excellent retention of superhydrophobicity against impact of sand particles from a height of 10-70 cm. In addition, after being damaged chemically by strong acid treatment (2M HNO3 solution), the coating can also restore its properties after a short thermal cycle. Such versatile superhydrophobic surfaces can have wide applications ranging from under-water marine vessels to coating for surfaces to protect them from moisture and unwanted penetration of water.

  20. Development of an enzymatic reactor applying spontaneously adsorbed trypsin on the surface of a PDMS microfluidic device. (United States)

    Kecskemeti, Adam; Bako, Jozsef; Csarnovics, Istvan; Csosz, Eva; Gaspar, Attila


    Herein, a microfluidic device (MD) containing immobilized trypsin for rapid and efficient proteolysis was described. Trypsin was immobilized via non-specific protein adsorption onto the hydrophobic poly(dimethylsiloxane) (PDMS) channel wall of the MD. Peptide mapping of bovine serum albumin (BSA) samples was carried out to estimate the stability of trypsin adsorbed on PDMS surface. Peptide maps of BSA samples were obtained by capillary zone electrophoresis (CZE), the RSD% for migration times were under 1%. Several proteins (hemoglobin, myoglobin, lysozyme, and BSA) in a wide molecular size range (15-70 kDa) were digested efficiently with ∼50 s contact time. The number of separated peaks correlated well with the expected number of peptides formed in the complete tryptic digestion of the proteins. Peptide mass fingerprinting of BSA and human serum was carried out. Trypsin retained its activity for 2 h; within this period, the MD can be used for multiple digestions. The main properties of this device are simple channel pattern, simple immobilization procedure, regenerability, and disposability; all these features make this MD one of the simplest yet applicable enzymatic microreactors. Graphical abstract Development of microfluidic device including a serpentine channel as an enzyme reactor for protein digestion.