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Periodic dynamics, localization metastability, and elastic interaction of colloidal particles with confining surfaces and helicoidal structure of cholesteric liquid crystals

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Physical Review E 2014年第6期90卷 062502-062502页

作者： Michael C. M. Varney Qiaoxuan Zhang Mykola Tasinkevych Nuno M. Silvestre Kris A. Bertness Ivan I. Smalyukh Department of Physics University of Colorado at Boulder Boulder Colorado 80309 USA Materials Science and Engineering Program University of Colorado at Boulder Boulder Colorado 80309 USA Max-Planck-Institut für Intelligente Systeme D-70569 Stuttgart Germany Institut für Theoretische Physik IV Universität Stuttgart D-70569 Stuttgart Germany Centro de Física Teórica e Computacional and Faculdade de Ciências da Universidade de Lisboa Av. Prof. Gama Pinto 2 1649-003 Lisboa Portugal National Institute of Standards and Technology Boulder Colorado 80305 USA Department of Electrical Computer and Energy Engineering and Liquid Crystals Materials Research Center University of Colorado at Boulder Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado at Boulder Boulder Colorado 80309 USA

Nematic and cholesteric liquid crystals are three-dimensional fluids that possess long-range orientational ordering and can support both topological defects and chiral superstructures. Implications of this ordering remain unexplored even for simple dynamic processes such as the ones found in so-called “fall experiments,” or motion of a spherical inclusion under the effects of gravity. Here we show that elastic and surface anchoring interactions prompt periodic dynamics of colloidal microparticles in confined cholesterics when gravity acts along the helical axis. We explore elastic interactions between colloidal microparticles and confining surfaces as well as with an aligned ground-state helical structure of cholesterics for different sizes of spheres relative to the cholesteric pitch, demonstrating unexpected departures from Stokes-like behavior at very low Reynolds numbers. We characterize metastable localization of microspheres under the effects of elastic and surface anchoring periodic potential landscapes seen by moving spheres, demonstrating the important roles played by anchoring memory, confinement, and topological defect transformation. These experimental findings are consistent with the results of numerical modeling performed through minimizing the total free energy due to colloidal inclusions at different locations along the helical axis and with respect to the confining substrates. A potential application emerging from this work is colloidal sorting based on particle shapes and sizes.

关键词： CHOLESTERIC liquid crystals LIQUID crystals ENANTIOSELECTIVE catalysis HELICAL waveguides GRAVITY

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Gradient field microscopy for label-free diagnosis of human biopsies [Invited]

Gradient field microscopy for label-free diagnosis of human ...

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作者： Kim, Taewoo Sridharan, Shamira Kajdacsy-Balla, André Tangella, Krishnarao Popescu, Gabriel Quantitative Light Imaging Laboratory Department of Electrical and Computer Engineering Beckman Institute for Advanced Science and Technology Urbana IL 61801 United States Quantitative Light Imaging Laboratory Department of Bioengineering Beckman Institute for Advanced Science and Technology Urbana IL 61801 United States University of Illinois at Chicago Department of Pathology Chicago IL 60612 United States Christie Clinic Department of Pathology University of Illinois at Urbana-Champaign Urbana IL 61801 United States

We introduce a label-free method for detecting high-grade prostatic intraepithelial neoplasia (HGPIN) in unstained biopsies. We image this condition based on the identification of basal cells in biopsies that otherwise would resemble prostate cancer by unassisted histologic examination. Gradient field microscopy (GFM) is used as a label-free imaging method which increases the contrast of a transparent sample by taking the first-order phase derivative that is very sensitive to rapid refractive index changes. GFM is able to image the basal cell layers in HGPIN biopsies because of their rapid refractive index changes at the periphery of small glandular structures. © 2012 Optical Society of America.

关键词： Biopsy

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Recent Advances in Detection of Ochratoxin-A

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Open Journal of Applied Biosensor 2013年第1期2卷 1-11页

作者： Ajeet Kaushik Sunil K. Arya Abhay Vasudev Shekhar Bhansali Bioelectronics Program Institute of Microelectronics A*STAR (Agency for Science Technology and Research) 11 Science Park Road Singapore Science Park II Singapore 117685 Singapore Bio-MEMS and Microsystems Lab Department of Electrical and Computer Engineering Florida International University Miami USA Bio-MEMS and Microsystems Lab Department of Electrical and Computer EngineeringFlorida International University Miami USA Department of Biomedical Engineering Florida International University Miami USA

Ochratoxin-A[7-(L-β-phenylalanylcarbonyl)-carboxyl-5-chloro-8-hydroxy-3,4-dihydro-3R-methyl-isocumarin, OTA] is a common food contaminant mycotoxin that enters the human body through the consumption of improperly stored food products. Upon ingestion, it leads to immuno-suppression and immuno-toxicity. OTA has been known to produce nephrotoxic, teratogenic, and carcinogenic activity (via oxidative DNA damage) in several species. This review introduces potentials of electrochemical biosensor to provide breakthroughs in OTA detection through improved selectivity and sensitivity and also the current approaches for detecting OTA in food products.

关键词： Biopolymer Mycotoxins Ochratoxin-A Chitosan Organic-Inorganic Hybrid Nanocomposite Biosensors

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Steep subthreshold slope nanowire nanoelectromechanical field-effect transistors (NW-NEMFETs)

Steep subthreshold slope nanowire nanoelectromechanical fiel...

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Berkeley Symposium on Energy Efficient Electronic Systems (E3S)

作者： Ji-Hun Kim Zack C. Y. Chen Soonshin Kwon Jie Xiang Department of Electrical and Computer Engineering University of California San La Jolla CA Department of Materials Science Program University of California San La Jolla CA

Significant physical challenges remain for CMOS technology to decrease I off as transistor dimension and power supply voltages continue downscaling. However, a fundamental thermodynamic limit in the subthreshold slope SS = |(∂V g )/(∂lnI d )| = ln10 · k B T/q at >60 mV/dec exists at room temperature. We have designed and demonstrated the first semiconductor nanowires (NWs) and nanoelectromechanical system (NEMS) field effect transistor structure (NW-NEMFET). We have previously demonstrated 0.5 ps intrinsic delay and near ballistic operation in quantum confined semiconductor heterostructure NWFETs with diameters less than 15 nm.[1] The current design uses high performance suspended semiconductor NWs as the conduction channel, while the electrostatic pull-in of the NW towards the gate stack enables abrupt switching to the off-state leading to high frequency, low power nanoelectronics. Simulation shows that compared to planar suspended-gate FET (SGFET) design [2], NW-NEMFET allows zero SS with 10 15 on-off ratio and near 1V pull-in voltage due to enhanced 3D capacitive coupling, as well as operation at very-high-frequency (VHF) and even ultra-high-frequency (UHF) due to the NW beams high aspect ratio and small dimensions.

关键词： Logic gates Silicon Electrodes Couplings Electrostatics Three-dimensional displays Transistors

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Multi-hole defect photonic crystals with enhanced surface area for biosensing applications

Multi-hole defect photonic crystals with enhanced surface ar...

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Laser science, LS 2013

作者： Hu, S. Kang, C. Zhao, Y. Mares, J.W. Vlasov, Y.A. Assefa, S. Weiss, S.M. Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 United States Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN 37235 United States Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States IBM T.J. Watson Research Center Yorktown Heights NY 10536 United States

Multi-hole defect (MHD) photonic crystal cavities functionalized with in situ synthesized DNA bioreceptors are demonstrated for biosensing applications. By significantly increasing light interaction with target biomol... 详细信息

ISBN: (纸本)9781557529879

关键词： Photonic crystals

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Group Method of Data Handling for Modeling Magnetorheological Dampers

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Intelligent Control and Automation 2013年第1期4卷 70-79页

作者： Khaled Assaleh Tamer Shanableh Yasmin Abu Kheil Department of Computer Science and Engineering American University of Sharjah Sharjah United Arab Emirates Department of Electrical Engineering American University of Sharjah Sharjah United Arab Emirates Mechatronics Graduate Program American University of Sharjah Sharjah United Arab Emirates

This paper proposes the use of Group Method of Data Handling (GMDH) technique for modeling Magneto-Rheological (MR) dampers in the context of system identification. GMDH is a multilayer network of quadratic neurons that offers an effective solution to modeling non-linear systems. As such, we propose the use of GMDH to approximate the forward and inverse dynamic behaviors of MR dampers. We also introduce two enhanced GMDH-based solutions. Firstly, a two-tier architecture is proposed whereby an enhanced GMD model is generated by the aid of a feedback scheme. Secondly, stepwise regression is used as a feature selection method prior to GMDH modeling. The proposed enhancements to GMDH are found to offer improved prediction results in terms of reducing the root-mean-squared error by around 40%.

关键词： System Identification Magneto-Rheological Dampers Group Method of Data Handling Polynomial Classifier

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High Energy Density, High Operating Frequency and Energy Efficient On-Chip Inductors based on Coiled Carbon Nanotubes (CCNTs)

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MRS Online Proceedings Library (OPL) 2013年第1期1551卷 41-46页

作者： H. Faraby P. R. Bandaru Department of Electrical and Computer Engineering University of California San Diego La Jolla California 92093-0407 USA Department of Mechanical and Aerospace Engineering Materials Science Program University of California San Diego La Jolla California 92093-0411 USA

We demonstrate the superior inductive properties of coiled carbon nanotubes (CCNTs) through numerical computation and analytical modeling, for the next generation of nanoscale, on-chip inductors. Taking advantage of the kinetic inductance (Lk), particularly evident at the nanoscale we find that the inductance can be increased by three orders of magnitude through changing the tube radius as well as the coil radius while the device footprint of the CCNTs can be reduced by 60%. By varying the geometric parameters of the coiled structure, the external magnetic inductance (LM,ext) can be as high as 20% of the Lk. We also report that the self resonant frequency (fSR) of CCNTs can be as much of the order of THz whereas the fSR of conventional copper(Cu) spiral inductors are limited to around 40GHz. Moreover when the material volume is considered, CCNTs have the potential to achieve Quality Factor (Q) eight times as Cu and when the footprint volume is considered Q can be twice as Cu All these promising properties of CCNTs make them a potential candidate for the entire frequency spectrum.

关键词： C nanoscale morphology

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Low-power signal processing methodologies for implantable biosensing platforms

Low-power signal processing methodologies for implantable bi...

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IEEE Signal Processing in Medicine and Biology Symposium (SPMB)

作者： Robert A. Croce Santhisagar Vaddiraju Allen Legassey Syed K. Islam Fotios Papadimitrakopoulos Faquir C. Jain Department of Electrical and Computer Engineering University of Connecticut CT USA Dept. of Chemistry University of Connecticut CT USA Technology Incubation Program Biorasis Inc. CT USA Department of Electrical Engineering and Computer Science University of Tennessee Knoxville TN USA

This paper presents the design and implementation of highly-miniaturized, low-power CMOS signal conditioning schemes intended for use in a totally implantable biomedical sensor platform. Due to the thrust for the development implantable biomedical sensing systems for health management and disease prevention, there exists a need for signal processing schemes which occupy very little on-chip real estate and consume negligible amounts of power. In light of this, this paper presents both a CMOS current-to-frequency converter and voltage-to-frequency converter which have been designed primarily for use in implantable biosensing platforms and applications. Such designs can be implemented in stand-alone single sensor designs, or in tandem to create multi-analyte architectures. The versatility of employing current-to-frequency as well as voltage-to-frequency signal transduction schemes presents an avenue for the integration with any electrochemical sensing element which has been fabricated in an amperometric or voltammetric fashion. Furthermore, we demonstrate the efficacy of both these circuit designs by integrating them together with high performance electrochemical implantable glucose and pH sensors. The low power consumption and miniature size of the amperometric and voltammetric signal processing units (0.25 mm 2 and 18 μW / 0.045 mm 2 and 122 μW, respectively) presents an ideal design for signal processing in implantable continuous metabolic monitoring devices.

关键词： Monitoring Biomedical monitoring Educational institutions CMOS integrated circuits Microelectronics Current measurement Sugar

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A wearable real-time BCI system based on mobile cloud computing

A wearable real-time BCI system based on mobile cloud comput...

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International IEEE/EMBS Conference on Neural engineering, CNE

作者： Maria V. Ruiz Blondet Adarsha Badarinath Chetan Khanna Zhanpeng Jin Binghamton University Binghamton NY US Department of Computer Science State University of New York Binghamton NY USA Departments of Electrical and Computer Engineering and Bioengineering State University of New York Binghamton NY USA

Pervasive and wearable brain-computer interface (BCI) systems show great potential for effectively understanding human mental activities and intentions in their daily life. In this paper, we propose a real-time BCI system based on mobile devices and cloud computing to detect and recognize the user's mental states. A proof-of-concept prototype is developed based on a wearable, commercially available EEG headset, an Android smartphone, and a multi-core computing server. We demonstrate an integrated Android app containing three built-in functional modules. Specifically, a graphical window can receive and display continuous EEG data acquired from the headset in a real-time manner; a facial expression interface can indicate the user's mental states according to the analysis of EEG data on the server; and a retrospective analysis tool to investigate the mental behaviors over a long period of time.

关键词： Electroencephalography Servers Headphones Mobile communication Mobile handsets Real-time systems Humanoid robots

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Towards Template-Assisted Assembly of Nematic Colloids

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Physical Review Letters 2014年第22期112卷 225501-225501页

作者： Nuno M. Silvestre Qingkun Liu Bohdan Senyuk Ivan I. Smalyukh Mykola Tasinkevych Departamento de Física da Faculdade de Ciências Universidade de Lisboa Avenida Professor Gama Pinto 2 P-1649-003 Lisboa Portugal Centro de Física Teórica e Computacional Universidade de Lisboa Avenida Professor Gama Pinto 2 P-1649-003 Lisboa Portugal Department of Physics University of Colorado Boulder Colorado 80309 USA Liquid Crystal Materials Research Center University of Colorado Boulder Colorado 80309 USA Department of Electrical Computer and Energy Engineering and Materials Science and Engineering Program University of Colorado Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA Max-Planck-Institut für Intelligente Systeme Heisenbergstrasse 3 D-70569 Stuttgart Germany Institut für Theoretische Physik IV Universität Stuttgart Pfaffenwaldring 57 D-70569 Stuttgart Germany

Colloidal crystals belong to a new class of materials with unusual properties in which the big challenge is to grow large-scale structures of a given symmetry in a well-controlled and inexpensive way. Recently, template-assisted crystallization was successfully exploited experimentally in the case of colloidal particles dispersed in isotropic fluids. In liquid crystal (LC) colloids, particles are subjected to long-range anisotropic elastic forces originating from the anisotropic deformation of the underlying order parameter. These effective interactions are easily tunable by external electric or magnetic fields, light, temperature, or confinement and, thus, provide additional handles for better control of colloidal assembly. Here we use the coupling between microsculptured bounding surfaces and LC elasticity in order to guide the self-assembly of large-scale colloidal structures. We present explicit numerical calculations of the free energy landscape of colloidal particles in the presence of convex protrusions modeled as squared pyramids comparable to the size of the particles. We show the existence of strong trapping potentials that are able to efficiently localize the colloidal particles and withstand thermal fluctuations. Three-dimensional optical imaging experiments support the theoretical predictions.

关键词： COLLOIDAL crystals SYMMETRY (Physics) NEMATIC liquid crystals CRYSTALLIZATION COUPLING constants (Nuclear physics) OPTICAL imaging sensors

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