bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanocomposite Conductive Elastomer: Microfabrication Processes and Applications in Soft-Matter MEMS Sensors
Authors: Liu Chang 
Published: April 2011

ABSTRACT3D micro-molded PDMS (polydimethylsiloxane) elastomer is widely used in MEMS. However, traditional PDMS is non-conductive and as a result is used in mostly structural applications. It is difficult to embed elastomeric, “stretchy” conductors and transduction elements in molded PDMS matrix. We report general methods for monolithic fabrication of multi-layer PDMS structures with embedded conductive and non-conductive elastomer elements. Conductive PDMS parts, made of carbon-nanotube-filled composite PDMS, can form internal elastomer wires, electrodes, heaters, and sensors. The process uses a series of PDMS patterning, micromolding, and bonding techniques. In this work we demonstrate elastomer strain gauges, capacitive pressure sensors, as well as microfluidic channels with integrated heaters and sensors.
Interactions, Dynamics and Self-assembly of Magnetic Holes
Authors: de lang Kristiansen Kai , Svåsand Eldrid , Helgesen Geir , Skjeltorp Arne T. 
Published: April 2011

ABSTRACTNonmagnetic microspheres dispersed in a ferrofluid are denoted magnetic holes. When the spheres are confined to a monolayer between two plane, parallel plates and subjected to AC magnetic fields, they show a variety of dynamical behaviors and assemblages. The magnetic interactions between the particles and their dynamical behavior are influenced by the boundaries and the degree of confinement. We have derived analytical results for the pair-wise competing interactions, and these compare favorably with experimental results.It is also possible to characterize the self-assembly and dynamics of the spheres by the theory of braids. It involves classifying different ways of tracing curves in space. The essentially two-dimensional motion of a sphere can be represented as a curve in a three-dimensional space-time diagram, and so several spheres in motion produce a set of braided curves. The dynamical modes can then be described in terms of braid-words. We also present a few other examples on how this system can be used to study dynamical processes.
Electronic Transport Measurements in Tin Oxide Microfibers Created From a Polymer Solution
Authors: Taku Maria , Rodd Chris , Santiago Jorge 
Published: April 2011

ABSTRACTTin oxide microfibers were created through electrospinning using a precursor solution consisting of poly(ethylene oxide) (PEO) and chloroform (CHCl3) which was then mixed with its tin precursor, dimethyldineodecanoatin (C22H44O4Sn). Since the conductivity of SnO2 is affected by any chemisorbed oxygen molecules on its surface, this semiconductor has high potential for use as a gas sensor for both oxidizing and reducing gases. Due to the fact that a greater surface area will produce gas sensors with improved sensitivity, work is underway to reduce the fibers size into the nanoscale range. Thus, this study explores various electronic transport characteristics—such as the conductivity and magnetoresistance—of the tin oxide microfibers. Additionally, the composition and phase of the fibers were characterized through XRD and Raman spectroscopy.
Taking Advantage of Supramolecular Structure in Melt and Solution Electrospinning
Authors: Hunley Matthew T. , McKee Matthew G. , Gupta Pankaj , Wilkes Garth L. , Long Timothy E. 
Published: April 2011

ABSTRACTElectrospinning, a polymer processing technique to create nanofibrous membranes, has been used to fabricate fibrous membranes from solution and melt phases showing supramolecular order. Wormlike micellar phases of low molar mass amphiphiles, including the phospholipid mixture asolectin, were electrospun under normal conditions to form micron-sized fibers. From the melt, well defined phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine was electrospun into a similar fibrous membrane. Additionally, thermoreversible physical crosslinks were used to prepare fibers from low molecular weight, star-shaped poly(D,L-lactide) under melt electrospinning conditions.
Micropatterned Polythiophene Nanofibers via Electrostatic Spinning and Photolithography
Authors: Asemota Chris Ik , Kumar Arvind , Sotzing Gregory A 
Published: April 2011

ABSTRACTHerein we report the patterning of large conducting polymer nanofiber mats of the polyterthiophene precursor, into regular micron scale arrays of smaller mats each of which has the potential of being independently addressed. These fiber grids, micro mats of conducting polymer fibers, were prepared by the combined techniques of electrospinning, soft photolithography, and solid state electrochemical crosslinking. The micro size mats are shown to retain their electrochromic behavior, subject to expected degradation in air as reported in the literature. Our contribution to the investigation of conducting polymers in display technology is oriented towards processibility and preparation of regular conducting polymer structures.
Characterization of Fibers Electrospun from Organometallic Tin Precursors in a Polymer Binder
Authors: Rodd Christopher , Santiago-Avilés Jorge J. 
Published: April 2011

ABSTRACTElectrospinning has been thought of as an effective, low cost technique for producing nanofibers for use in gas sensor applications with nanofibers of tin oxide showing particular promise in this area. Critical to the success of tin oxide in these applications are nanowires with a rutile phase structure and well defined current-voltage characteristics which requires controlled fiber diameters. This paper reports on the characterization of the pre and post sintered fibers deposited via electrospinning of two different tin precursor chemicals, dimethyl dineodecanoate tin and dimethyl dichloro tin, both spun within a polyethylene oxide / chloroform binder system. Both tin precursor systems were evaluated at different concentration levels to investigate morphological changes due to concentration. Mats of fibers were spun on silicon wafers and sintered at 600°C for 2 hours. Morphology was characterized by optical microscope while chemical composition was determined via Raman spectrometry. Fibers of dimethyl dineodecanoate tin were found be ∼30μm in diameter and to have considerable component separation upon deposition. After sintering, SnO2 islands were found but there was no fiber appearance. Fibers of dimethyl dichloro tin were found to be ∼10μm in diameter and lacked the component separation seen in the other tin precursor system with some SnO2 domains found directly inline with initial fiber deposition. Comparison of results from both systems shows that the interaction of the polymer and tin precursor is of paramount importance for development of micro- or nanosized ceramic wires deposited by electrospinning.
Effect of Molecular Structure of Scavengers on Copper Diffusion Deterrence in Low k Film
Authors: Nomura Yutaka , Ryuzaki Daisuke , Koyanagi Mitsumasa 
Published: April 2011

ABSTRACTLow k material with high deterrence ability of copper diffusion has been proposed to reduce the effective electrical resistance of copper wirings. Providing organic low k material with deterrence ability was attempted by adding a chemical agent that chemically combines with copper. The insulation lifetime of the low k film with benzotriazole (BTA) as the copper scavenger was about two orders of magnitude higher than that of BTA-free low k film, at the practical electric field strength of 0.1 MV/cm. The copper diffusion deterrence ability was clearly dependent on the ability of the copper scavenger.
Multiple Relaxations in Poly (p-hydroxybenzoic acid-CO-ethylene terephthalate) Liquid Crystal Polymer: TSD Current Investigations
Authors: Quamara Jitendra Kumar , Yarramaneni Sridharbabu , Goyal Geetika 
Published: April 2011

ABSTRACTThe PET/x.PHB samples were polarized at different temperatures (30-250°C) under various biasing fields ranging from 40 to 200 kV/ cm. The TSD currents were obtained at a heating rate of 2 °C/min in the temperature range (15-250)°C. The TSD current spectra in general comprise of three maxima namely β, α and δ in ascending order of temperature. However number of peaks actually appearing in these spectra, their location, height and sharpness are governed by polarization/depolarization parameters as well as the value of ‘x’ in a particular sample. The β peak appearing around (110-140°C) has been recognized as a dipolar relaxation process and is due to PET rich phase. The α- peak (160-180°C) recognized as space charge process is due to PHB rich phase and cold crystallization of PET rich phase. The δ peak (190-210°C) is a melting process due to the movement of large segments leading to Smectic-E like phase. In addition PET/x.PHB also exhibit a weak low temperature dipolar relaxation process β′ peak around (30-40)°C. In the vicinity of α-relaxation a rigid amorphous phase dipolar relaxation process γ relaxation is also observed.
Microstructure-Based Simulation of the Dielectric Properties of Polymer-Ceramic Composites for Capacitor Applications
Authors: Calame Jeffrey P. 
Published: April 2011

ABSTRACTResearch on the microstructure-based modeling of composite dielectrics for capacitor applications is described. Methods for predicting the composite dielectric permittivity and internal electric field distributions within the microstructure using finite difference quasi-electrostatic modeling are described, along with methods of generating realistic model spaces of particulate microstructures. An existing algorithm for generating random, monosized spheres-in-a-dielectric matrix model spaces is modified to allow the treatment of bimodal composites in which small particles are deliberately segregated into the spaces between large particles. Such composites can have substantially higher total volumetric filling fractions of particles, leading to higher composite permittivity. The variations in permittivity with the filling fractions of bimodal inclusions are studied with the new model, with cases covering three different types of polymer matrix material. The effect of the small particle additions on the electric field statistics within the polymer matrix is also explored.
Hydrophobic Dielectrics of Fluoropolymer / BaTiO3 Nanocomposites for Low-Voltage and Charge Storing Electrowetting Devices
Authors: Kilaru Murali K. , Lin Gui , Mark James E , Heikenfeld Jason C 
Published: April 2011

ABSTRACTA hydrophobic fluoropolymer:BaTiO3 nanocomposite is presented for achieving lower-voltage electrowetting operation. The composite fluoropolymer film exhibits as much as a 10X increase in measured dielectric constant. Increased surface roughness with BaTiO3 content increased the sessile drop contact angle from θ∼104° to 121° with compositions ranging from 0 to 97 vol. % of BaTiO3 in the fluoropolymer. A larger change in electrowetted contact angle is observed for the 50 vol. % of BaTiO3 nanocomposite (delta theta∼60°) compared to a standard fluoropolymer film of 1 um thickness (delta theta∼30°). Furthermore, required operating voltage for electrowetting decreases by ∼30V for films with high BaTiO3 content. Strong charge storage in the nanocomposite was observed via a new bistable electrowetting effect. For samples with strong charge storage, the droplet remains wetted (>2 minutes) even after removing the applied voltage. Rapid (< 1s) droplet de-wetting could be achieved by briefly applying a reverse polarity voltage to remove the stored charge in the nanocomposite.
A Novel Method To Prepare Cysteine Capped Cadmium Selenide Nanoparticles
Authors: Oluwafemi Oluwatobi Samuel , Revaprasadu Neerish 
Published: April 2011

ABSTRACTWater dispersable and potentially biocompatible L-cysteine-capped CdSe nanoparticles with a narrow size distribution and blue fluoresence have been synthesized by a facile method without using any additional stabilizer. FTIR study shows that CdSe nanoparticles are capped through mercapto-group of the amino acid cysteine whilst its free amino and carboxylate groups make it amenable to bio-conjugation establishing the possibility of using these as fluorescent biomarkers.
Investigation of Cantilever Resonance Applied to Potentiometric Sensing
Authors: Koley Goutam , Lakshmanan Lakshminarayanan 
Published: April 2011

ABSTRACTWe demonstrate a highly sensitive potentiometric gas sensor based on a resonating Si microcantilever. Using a scanning probe microscope based set up in non-contact mode, the microcantilever was made to oscillate at its resonance frequency with periodically changing amplitude, using simultaneous mechanical and electrical excitation sources. The variation of the oscillation amplitude was found to be extremely sensitive to changes in surface potential, and served as a linear indicator for surface work function changes caused by molecular adsorption. The microcantilever sensor was found to be able to detect changes in surface potential down to 50 microvolt, which is basically limited by the system noise. When applied to sensing hydrogen using platinum coated cantilevers, it was observed that the microcantilever sensor can detect 1000 ppm hydrogen with an estimated lower limit of the detection time of 70 ms, at a cantilever-ground electrode distance of ∼10 micron. Several parameters, such as ac signal amplitude, cantilever – reference electrode distance, quality factor, area, and spring constant of the cantilever, can be adjusted to significantly enhance the sensitivity, possibly by orders of magnitude. Excitation of the cantilever at subharmonic resonance frequencies was also performed to study possible parametric resonance effects. In this system it was possible to observe sub-harmonic resonance of order more than 50 (i.e. lower than one-fiftieth the resonance frequency).
Detection of Bacillus Anthracis Spores Using Magnetostrictive Microcantilever-based Biosensor
Authors: Fu Liling , Li Suiqiong , Zhang Kewei , Cheng Z.-Y. 
Published: April 2011

ABSTRACTRecently, the magnetostrictive microcantilever (MSMC) as a high performance biosensor platform was introduced. The MSMC is a wireless acoustic wave (AW) sensor and exhibits a high Q value. More importantly, the MSMC works well in liquid. In this paper, the detection of Bacillus anthracis spores using MSMCs with filamentous phage as the bioprobe is reported. The phased-coated MSMC biosensors were exposed to cultures containing target spores with increasing concentrations ranging from 5 × 104 to 5 × 108 spores/mL. By monitoring the shift in the resonance frequency of the MSMCs, the spores were detected in a real-time manner and a detection limit of 105 spores/mL was obtained for the MSMCs used in this research. Higher sensitivity is expected for the MSMCs with smaller size.
Post-processing of Commercial CMOS Chips for the Fabrication of DNA Bio-FET Sensor Arrays
Authors: Jiang Weihong , Landheer D. , Lopinski G. , Rankin A. , Tarr N. G. , Deen M. J. 
Published: April 2011

ABSTRACTA BioFET array can be fabricated by post-processing of a standard CMOS chip if temperatures are kept below 450 ° and radiation or ion-bombardment damage is minimized. The processing starts with encapsulation by deposition of a low stress, electrolyte-impermeable silicon nitride layer by PECVD at 375 °C. Anisotropic reactive ion etching with an inductively coupled plasma using C4F8 and Ar was used to remove the silicon nitride and oxide layers above the poly-silicon gates. The poly-silicon was then etched off using a selective wet etch. The effect of the processing was characterized by making current-voltage and capacitance-voltage measurements with MOS capacitor structures at each stage of processing and results showed that trapped charges or interface states could be annealed out at low temperatures. Scanning electron microscopy was used to examine the cross-section of the gate areas after the etching. The results of current-voltage measurements with a Ag/AgCl reference electrode on devices in electrolyte solutions were compared to the results of charge-sheet model calculations including the effect of amphoteric charging sites on the oxide and the potential drops in the electrolyte. Measurements showing the threshold shifts subsequently produced by DNA probe attachment and hybridization will also be presented.
Increased Stem Cell Adhesion on Carbon Nanotubes Grown from Anodized Titanium
Authors: Ercan Batur , Webster Thomas 
Published: April 2011

ABSTRACTStem cells are the source of all differentiated cells in the body. However, the stimuli that control stem cell differentiation into other cell types is still not well understood. In order to investigate this, novel carbon nanotubes (CNT's) were synthesized on anodized titanium substrates by chemical vapor deposition. Human mesenchymal stem cell (HMCS) adhesion was investigated on this nano-structured surface. The results showed significant evidence for the enhancement of HMSC adhesion on carbon nanotubes with respect to the template they were synthesized on, specifically, anodized titanium. Such evidence provides promise for the use of carbon nanotubes grown from anodized titanium to serve as novel stem cell differentiation devices.
Hydrothermal Synthesis of Nanorods/Nanoparticles TiO2 for Photocatalytic Activity and Dye-sensitized Solar Cell Applications
Authors: Pavasupree Sorapong , Ngamsinlapasathian Supachai , Suzuki Yoshikazu , Yoshikawa Susumu 
Published: April 2011

ABSTRACTNanorods/nanoparticles TiO2 with mesoporous structure were synthesized by hydrothermal method at 150 °C for 20 h. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. The nanorods had diameter about 10-20 nm and the lengths of 100-200 nm, the nanoparticles had diameter about 5-10 nm. The prepared material had average pore diameter about 7-12 nm. The BET surface area and pore volume of the sample are about 203 m2/g and 0.655 cm3/g, respectively. The nanorods/nanoparticles TiO2 with mesoporous structure showed higher photocatalytic activity (I3− concentration) than the nanorods TiO2, nanofibers TiO2, mesoporous TiO2, and commercial TiO2 (ST-01, P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using nanorods/nanoparticles TiO2 with mesoporous structure was about 7.12 % with Jsc of 13.97 mA/cm2, Voc of 0.73 V and ff of 0.70; while η of the cell using P-25 reached 5.82 % with Jsc of 12.74 mA/cm2, Voc of 0.704 V and ff of 0.649.
Process Characterization of Ultra-fine Tin Oxide Fibers Synthesis
Authors: Wang Yu , Ramos Idalia , Santiago-Avilés Jorge J. 
Published: April 2011

ABSTRACTTin oxide (SnO2) with rutile structure is a wide-band gap semiconductor that has been used extensively in optoelectronic devices and sensors. A fibrous shape is especially favorable for the sensor applications. The authors synthesized micro-/nano- SnO2 fibers from a precursor solution of poly (ethylene oxide) (PEO), chloroform (CHCl3) and dimethyldineodecanoate tin (C22H44O4Sn) using electrospinning and metallorganics decomposition techniques. This paper uses Fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, and x-ray diffraction to reveal a series of chemical and physical changes from the starting chemicals to the final product of ultra-fine SnO2 fibers: the solvent CHCl3 evaporates during the electrospinning; the organic groups in PEO and C22H44O4Sn decompose with Sn-C bond in C22H44O4Sn replaced by Sn-O between 220 and 300°C, and transform into rutile structure between 300 and 380°C; the incipient rutile lattice develops into a relatively complete degree after sintering at higher temperatures up to 600°C.
Effect of anodization conditions on the synthesis of TiO2 nanopores
Authors: Chatterjee Subhasish , Ginzberg Miriam , Gersten Bonnie 
Published: April 2011

ABSTRACTNanoporous structures play a promising role in the development of nanomechanical, nanoelectrical and biosensing devices. In addition, nanopores can be utilized as chemical and gas sensors. TiO2 is a semiconductor material, which can have a wide range of applications in nanopore-based sensors. In this study, TiO2 nanopores were prepared by electrochemical anodization. Titanium was used as the anode, while platinum was used as the cathode in an electrochemical cell filled with a hydrofluoric acid electrolyte solution. During the preparation process, titanium was converted to its oxide form. Nanostructures were synthesized under varying physical conditions, including HF concentrations of 0.5-10% and anodization times of 5-30 minutes. The resulting nanopore structures were characterized by scanning electron microscopy (SEM). With a progressive increase in HF concentration (from 0.5% to 10%), the diameter of the nanopores decreased, from approximately 100 nm in diameter to 50 nm. The nanopores showed a transformation from tube-like structures to pore networks with increased HF concentration or anodization time. The results show that the dimensions and morphology of the nanopores can be controlled by alteration of the anodization conditions.
Fabrication and Luminescence Properties of Monoclinic Gallium Oxide (β-Ga2O3) Nanostructures
Authors: Khan Aurangzeb , Jadwisienczak Wojciech M. , Lozykowski Henryk J. , Kordesch Martin E. 
Published: April 2011

ABSTRACTβ-Ga2O3 nanostructures including nanowires, nanorods, nano and micro-pillars, nanosheets and nanobelts were successfully fabricated by simple and efficient thermal evaporation and condensation technique under argon flow.. The structures have been investigated by the electron microscope, XRD and EDX techniques and shown that nanostructures are predominatly β-Ga2O3 without other crystallographic phases. Cathodouminescence of as-grown nanostructures was investigated in the 10-300 K temperature range and exhibit luminescence band centered at 485 nm at 300 K due to donor-acceptor pair recombination. A new luminescence band centered at 387 nm developes at temperature below 150 K due to self-trapped exciton recombination.
Fabrication of Porous Nanostructured Thin Films For Microfluidic and Microarray Applications
Authors: Bezuidenhout Louis Wentzel , Brett Michael J. 
Published: April 2011

ABSTRACTThe functionality of microfluidic and microassay devices could be enhanced through further development of porous engineered microstructures. New structural elements fabricated with porous nanostructured thin films deposited by the glancing angle deposition (GLAD) technique have been developed for these devices, and are reviewed here. With the GLAD technique, engineered structures such as vertical posts, slanted posts, helices, and square spirals can be directly grown inside microfluidic channels. A high surface area channel (517cm2/cm2) was made by depositing a silicon oxide porous film in glass microchannels (up to 4.5μm deep and 50μm wide). Similar channels were also fabricated by patterning channels in a photoresist-coated porous film. Self-sealed microchambers and channels were made by growing a SiO2 porous film on 14μm high silicon mesas (2.5×2.5μm, 7×7μm, and 25×25μm) and lines (2.5 to 50μm wide). Devices with channels containing periodic arrays of Si pillars with controllable porosity and architecture were fabricated with only one lithography and deposition cycle. The entire device was made by depositing a single GLAD porous film with areas of different porosity defining the channels. The channels, 200μm wide and 10.5μm deep, contained helical pillars with pore sizes ranging from 100nm-2μm, while a more dense nanofibrous helical film made up the remainder of the device. Fluid flow activated by negative pressure was demonstrated in this device, using both a dye solution and a 50nm microsphere solution. Material selection is not limited to silicon or silicon oxide, but may include a wide range of semiconductors, insulators and metals. A GLAD film was used to separate a test dye solution, demonstrating its potential for use in thin layer chromatography. The reported elements are suitable for a range of applications, including – but not limited to – chromatography, nano-assays and capillary electrophoresis.