Optical bio-sensing devices based on etched fiber Bragg gratings coated with carbon nanotubes and graphene oxide along with a specific dendrimer

We demonstrate that etched fiber Bragg gratings (eFBGs) coated with single walled carbon nanotubes (SWNTs) and graphene oxide (GO) are highly sensitive and accurate biochemical sensors. Here, for detecting protein concanavalin A (Con A), mannose-functionalized poly(propyl ether imine) (PETIM) dendrimers (DMs) have been attached to the SWNTs (or GO) coated on the surface modified eFBG. The dendrimers act as multivalent ligands, having specificity to detect lectin Con A. The specificity of the sensor is shown by a much weaker response (factor of similar to 2500 for the SWNT and similar to 2000 for the GO coated eFBG) to detect non specific lectin peanut agglutinin. DM molecules functionalized GO coated eFBG sensors showed excellent specificity to Con A even in the presence of excess amount of an interfering protein bovine serum albumin. The shift in the Bragg wavelength (Delta lambda(B)) with respect to the lambda(B) values of SWNT (or GO)-DM coated eFBG for various concentrations of lectin follows Langmuir type adsorption isotherm, giving an affinity constant of similar to 4 x 10(7) M-1 for SWNTs coated eFBG and similar to 3 x 10(8) M-1 for the GO coated eFBG. (C) 2014 Elsevier B.V. All rights reserved.

Performance of an ionomer blend-nanocomposite as an effective gas barrier material for organic devices

A new, flexible, gas barrier material has been synthesized by exfoliating organically modified nano-clays (MMT) in the blends of Surlyn (PEMA) using a copolymer of vinyl alcohol (EVOH) and demonstrated as a gas barrier material. The materials were characterized by Fourier transform infra red (FTIR) and UV-visible spectroscopy, differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and tensile studies. The oxygen and water-vapor permeabilities of the fabricated films were determined by calcium degradation test and a novel permeability setup based on cavity ring down spectroscopy, respectively. Hierarchical simulations of these materials helped us to understand the effect of intermolecular interactions on diffusivities of oxygen and water molecules in these materials. Schottky structured poly(3-hexylthiophene) based organic devices were encapsulated with the fabricated films and aging studies were carried under accelerated conditions. Based on permeability test results and accelerated aging studies, the fabricated PEMA/EVOH/MMT composites were found to be effective in decreasing the permeabilities for gases by about two orders of magnitude and maintaining the lifetime of organic devices.

A MatLAB Based Virtual Phantom for 2D Electrical Impedance Tomography (MatVP2DEIT): Studying the Medical Electrical Impedance Tomography Reconstruction in Computer

Electrical Impedance Tomography (EIT) is a computerized medical imaging technique which reconstructs the electrical impedance images of a domain under test from the boundary voltage-current data measured by an EIT electronic instrumentation using an image reconstruction algorithm. Being a computed tomography technique, EIT injects a constant current to the patient's body through the surface electrodes surrounding the domain to be imaged (Omega) and tries to calculate the spatial distribution of electrical conductivity or resistivity of the closed conducting domain using the potentials developed at the domain boundary (partial derivative Omega). Practical phantoms are essentially required to study, test and calibrate a medical EIT system for certifying the system before applying it on patients for diagnostic imaging. Therefore, the EIT phantoms are essentially required to generate boundary data for studying and assessing the instrumentation and inverse solvers a in EIT. For proper assessment of an inverse solver of a 2D EIT system, a perfect 2D practical phantom is required. As the practical phantoms are the assemblies of the objects with 3D geometries, the developing of a practical 2D-phantom is a great challenge and therefore, the boundary data generated from the practical phantoms with 3D geometry are found inappropriate for assessing a 2D inverse solver. Furthermore, the boundary data errors contributed by the instrumentation are also difficult to separate from the errors developed by the 3D phantoms. Hence, the errorless boundary data are found essential to assess the inverse solver in 2D EIT. In this direction, a MatLAB-based Virtual Phantom for 2D EIT (MatVP2DEIT) is developed to generate accurate boundary data for assessing the 2D-EIT inverse solvers and the image reconstruction accuracy. MatVP2DEIT is a MatLAB-based computer program which simulates a phantom in computer and generates the boundary potential data as the outputs by using the combinations of different phantom parameters as the inputs to the program. Phantom diameter, inhomogeneity geometry (shape, size and position), number of inhomogeneities, applied current magnitude, background resistivity, inhomogeneity resistivity all are set as the phantom variables which are provided as the input parameters to the MatVP2DEIT for simulating different phantom configurations. A constant current injection is simulated at the phantom boundary with different current injection protocols and boundary potential data are calculated. Boundary data sets are generated with different phantom configurations obtained with the different combinations of the phantom variables and the resistivity images are reconstructed using EIDORS. Boundary data of the virtual phantoms, containing inhomogeneities with complex geometries, are also generated for different current injection patterns using MatVP2DEIT and the resistivity imaging is studied. The effect of regularization method on the image reconstruction is also studied with the data generated by MatVP2DEIT. Resistivity images are evaluated by studying the resistivity parameters and contrast parameters estimated from the elemental resistivity profiles of the reconstructed phantom domain. Results show that the MatVP2DEIT generates accurate boundary data for different types of single or multiple objects which are efficient and accurate enough to reconstruct the resistivity images in EIDORS. The spatial resolution studies show that, the resistivity imaging conducted with the boundary data generated by MatVP2DEIT with 2048 elements, can reconstruct two circular inhomogeneities placed with a minimum distance (boundary to boundary) of 2 mm. It is also observed that, in MatVP2DEIT with 2048 elements, the boundary data generated for a phantom with a circular inhomogeneity of a diameter less than 7% of that of the phantom domain can produce resistivity images in EIDORS with a 1968 element mesh. Results also show that the MatVP2DEIT accurately generates the boundary data for neighbouring, opposite reference and trigonometric current patterns which are very suitable for resistivity reconstruction studies. MatVP2DEIT generated data are also found suitable for studying the effect of the different regularization methods on reconstruction process. Comparing the reconstructed image with an original geometry made in MatVP2DEIT, it would be easier to study the resistivity imaging procedures as well as the inverse solver performance. Using the proposed MatVP2DEIT software with modified domains, the cross sectional anatomy of a number of body parts can be simulated in PC and the impedance image reconstruction of human anatomy can be studied.

Stable and low resistive zinc contacts for SnS based optoelectronic devices

The contact behavior of tin mono sulfide (SnS) nanocrystalline thin films with zinc (Zn) and silver (Ag) contacts was studied. SnS films have been deposited on glass substrates by thermal evaporation technique at a growth temperature of 300 degrees C. The as-grown SnS films composed of vertically aligned nanocrystallites with a preferential orientation along the < 010 > direction. SnS films exhibited excellent chemical stoichiometry and direct optical band gap of 1.96 eV. These films also exhibited excellent Ohmic characteristics and low electrical resistivity with Zn contacts. The observed electrical resistivity of SnS films with Zn contacts is 22 times lower than that of the resistivity with Ag contacts. The interfacing analysis reveals the formation of conductive Zn-S layer between SnS and Zn as interfacial layer. (C) 2014 Elsevier B. V. All rights reserved.

Aminosilane Functionalized Cenosphere in Poly(vinyl butyral) Composite Films: Moisture Resistant Encapsulated Schottky Devices

Functionalized cenosphere in PVB composite films were fabricated by melt processing. The composites show higher tensile strength with lower failure strain with increased filler ratio in the matrix. Fractographic images of the samples and DMA studies indicate brittle failure of the matrix. Moisture permeation and water contact angle studies reveal improved hydrophobicity of the matrix, while the factor of surface roughness increases the wettability at higher filler content. Schottky-structured devices encapsulated with functionalized cenosphere indicate enhanced resistance to moisture and increased life time for the devices.

Detection of Target DNA using Photo-Reactive Protoporphyrin Moeity on a Nanocomposite Substrate

Detection of pathogens from infected biological samples through conventional process involves cell lysis and purification. The main objective of this work is to minimize the time and sample loss, as well as to increase the efficiency of detection of biomolecules. Electrical lysis of medical sample is performed in a closed microfluidic channel in a single integrated platform where the downstream analysis of the sample is possible. The device functions involve, in a sequence, flow of lysate from lysis chamber passed through a thermal denaturation counter where dsDNA is denatured to ssDNA, which is controlled by heater unit. A functionalized binding chamber of ssDNA is prepared by using ZnO nanorods as the matrix and functionalized with bifunctional carboxylic acid, 16-(2-pyridyldithiol) hexadecanoic acid (PDHA) which is further attached to a linker molecule 1-ethyl-3-(3-dimethylaminopropyl) (EDC). Linker moeity is then covalently bound to photoreactive protoporphyrin (PPP) molecule. The photolabile molecule protoporphyrin interacts with -NH2 labeled single stranded DNA (ssDNA) which thus acts as a probe to detect complimentary ssDNA from target organisms. Thereafter the bound DNA with protoporphyrin is exposed to an LED of particular wavelength for a definite period of time and DNA was eluted and analyzed. UV/Vis spectroscopic analysis at 260/280 nm wavelength confirms the purity and peak at 260 nm is reconfirmed for the elution of target DNA. Quantitative and qualitative data obtained from the current experiments show highly selective detection of biomolecule such as DNA which have large number of future applications in Point-of-Care devices.

Modelling of optical transport behavior of organic photovoltaic devices with nano-pillar transparent conducting electrodes

Optical transport behavior of organic photo-voltaic devices with nano-pillar transparent electrodes is investigated in this paper in order to understand possible enhancement of their charge-collection efficiency. Modeling and simulations of optical transport due to this architecture show an interesting regime of length-scale dependent optical characteristics. An electromagnetic wave propagation model is employed with simulation objectives toward understanding the mechanism of optical scattering and waveguide effects due to the nano-pillars and effective transmission through the active layer. Partial filling of gaps between the nano-pillars due to the nano-fabrication process is taken into consideration. Observations made in this paper will facilitate appropriate design rules for nano-pillar electrodes. (C) 2014 AIP Publishing LLC.

High-quality ZnO nanorod based flexible devices for electronic and biological applications

Vertically aligned zinc oxide nanorods (ZnO NRs) were synthesized on kapton flexible sheets using a simple and cost-effective three-step process (electrochemical seeding, annealing under ambient conditions, and chemical solution growth). Scanning electron microscopy studies reveal that ZnO NRs grown on seed-layers, developed by electrochemical deposition at a negative potential of 1.5 V over a duration of 2.5 min and annealed at 200 degrees C for 2 h, consist of uniform morphology and good chemical stoichiometry. Transmission electron microscopy analyses show that the as-grown ZnO NRs have single crystalline hexagonal structure with a preferential growth direction of < 001 >. Highly flexible p-n junction diodes fabricated by using p-type conductive polymer exhibited excellent diode characteristics even under the fold state.

A Brief Overview of the Recent Bio-Medical Applications of Fiber Bragg Grating Sensors

Fiber Bragg Grating (FBG) sensors have become one of the most widely used sensors in the recent times for a variety of applications in the fields of aerospace, civil, automotive, etc. It has been recently realized that FBGs and etched FBGs can play an important role in biomedical applications. This article provides a brief overview of the recent advancements in the application of FBG sensors in bio-mechanical, bio-sensing and bio-medical fields.

Field dependent and disorder-induced nonlinear charge transport in electrochemically doped polypyrrole devices

Electric field activated charge transport is studied in the metal/polymer/metal device structure of electropolymerized polypyrrole down to 10 K with varying carrier density and disorder. Disorder induced nonlinear behaviour is observed in polypyrrole devices grown at room temperature which is correlated to delocalization of states. The slope parameter of currentvoltage characteristics (in log-log scale) increases as the temperature decreases, which indicates the onset of stronger field dependence. The field dependence of mobility becomes dominant as the carrier density decreases. The sharp dip in differential conductance indicates the localization of carriers at low temperatures which reduces the effective number of carriers involved in the transport.

ZnO/ITO core/shell nanostructure electrodes for future prototype solar cell devices

The impact of indium tin oxide (ITO) layers over vertically aligned zinc oxide nanorods (ZnO NRs) has been investigated to consider ITO nanolayers as transparent conducting oxide electrodes (TCOE) for hierarchical heteronanostructure solar cell devices that have ZnO nanostructures as branches. ZnO/ITO core/shell nanostructures were prepared in two- steps using vapor-liquid-solid and evaporation processes, and further the structures were annealed at various temperatures. Transmission electron microscopic studies show that the as-grown ZnO/ITO structures consist of an amorphous ITO shell on single crystalline ZnO cores, whereas the structures annealed above 300 degrees C consist of a single crystalline ITO shell. ITO layer deposited ZnO NRs exhibit a small red-shift in ZnO near-band-edge emission as well as optical band gap. The electrical measurements carried out on single ZnO/ITO core/shell NR under dark and UV light showed excellent thermionic transport properties. From these investigations it is emphasized that ITO nanolayers could be used as TCO electrodes for prototype ZnO based hierarchical solar cell devices.

Nanocomposite Based Organic-Inorganic Cu3BiS3 High Sensitive Hybrid Photonic Devices

We report the synthesis and application Cu3BiS3 nanorods in infrared photodectection. Cu3BiS3 nano rods were characterized structurally, optically and electrically. The detailed IR photodectection properties in terms of photo response were demonstrated with IA lamp and 1064 nm laser illuminations. The rapid photocurrent time constants followed by the slower components, resulting due to the defect states. The photo detecting properties for different concentrations of nanorods blended with the conjugate polymer devices were demonstrated. Further the photocurrent was enhanced to threefold increase from 3.47 x 10(-7) A to 2.37 x 10(-3) A at 1 V for 10 mg nanorods embedded in the polymer device. Responsivity of hybrid device was enhanced from 0.0158 NW to 102 NW. The detailed trap assisted space charge transport properties were studied considering the different regimes. Hence Cu3BiS3 can be a promising candidate in the nano switchable near IA photodetectors.

Sparse Representation Based Acoustic Rangefinders: From Sensor Platforms to Mobile Devices

Acoustic rangerfinders are a promising technology for accurate proximity detection, a critical requirement for many emerging mobile computing applications. While state-of-the-art systems deliver robust ranging performance, the computational intensiveness of their detection mechanism expedites the energy depletion of the associated devices that are typically powered by batteries. The contribution of this article is fourfold. First, it outlines the common factors that are important for ranging. Second, it presents a review of acoustic rangers and identifies their potential problems. Third, it explores the design of an information processing framework based on sparse representation that could potentially address existing challenges, especially for mobile devices. Finally, it presents mu-BeepBeep: a low energy acoustic ranging service for mobile devices, and empirically evaluates its benefits.

Optically transparent polymer devices for in situ assessment of cell electroporation

In order to study cell electroporation in situ, polymer devices have been fabricated from poly-dimethyl siloxane with transparent indium tin oxide parallel plate electrodes in horizontal geometry. This geometry with cells located on a single focal plane at the interface of the bottom electrode allows a longer observation time in both transmitted bright-field and reflected fluorescence microscopy modes. Using propidium iodide (PI) as a marker dye, the number of electroporated cells in a typical culture volume of 10-100 mu l was quantified in situ as a function of applied voltage from 10 to 90 V in a series of 2-ms pulses across 0.5-mm electrode spacing. The electric field at the interface and device current was calculated using a model that takes into account bulk screening of the transient pulse. The voltage dependence of the number of electroporated cells could be explained using a stochastic model for the electroporation kinetics, and the free energy for pore formation was found to be kT at room temperature. With this device, the optimum electroporation conditions can be quickly determined by monitoring the uptake of PI marker dye in situ under the application of millisecond voltage pulses. The electroporation efficiency was also quantified using an ex situ fluorescence-assisted cell sorter, and the morphology of cultured cells was evaluated after the pulsing experiment. Importantly, the efficacy of the developed device was tested independently using two cell lines (C2C12 mouse myoblast cells and yeast cells) as well as in three different electroporation buffers (phosphate buffer saline, electroporation buffer and 10 % glycerol).

Absence of systemic toxicity in mouse model towards BaTiO3 nanoparticulate based eluate treatment

One of the existing issues in implant failure of orthopedic biomaterials is the toxicity induced by the fine particles released during long term use in vivo, leading to acute inflammatory response. In developing a new class of piezobiocomposite to mimic the integrated electrical and mechanical properties of bone, bone-mimicking physical properties as well as in vitro cytocompatibility properties have been achieved with spark plasma sintered hydroxyapatite (HA)-barium titanate (BaTiO3) composites. However, the presence of BaTiO3 remains a concern towards the potential toxicity effect. To address this issue, present work reports the first result to conclusively confirm the non-toxic effect of HA-BaTiO3 piezobiocomposite nanoparticulates, in vivo. Twenty BALB/c mice were intraarticularly injected at their right knee joints with different concentrations of HA-BaTiO3 composite of up to 25 mg/ml. The histopathological examination confirmed the absence of any trace of injected particles or any sign of inflammatory reaction in the vital organs, such as heart, spleen, kidney and liver at 7 days post-exposure period. Rather, the injected nanoparticulates were found to be agglomerated in the vicinity of the knee joint, surrounded by macrophages. Importantly, the absence of any systemic toxicity response in any of the vital organs in the treated mouse model, other than a mild local response at the site of delivery, was recorded. The serum biochemical analyses using proinflammatory cytokines (TNF-alpha and IL-1 beta) also complimented to the non-immunogenic response to injected particulates. Altogether, the absence of any inflammatory/ adverse reaction will open up myriad of opportunities for BaTiO3 based piezoelectric implantable devices in biomedical applications.