Electrical and electronics engineering

This work reports on the behavior of piezoresistive microcantilever sensors under optimizing conditions of ac electroosmotic enhancement. Piezoresistive microcantilevers are used as sensor elements for detection of concentrated bio-particles. Without preconcentrating the samples, using ac electroosmosis, these bio-particles have been manipulated onto the piezoresistive microcantilever. A piezoresistive microcantilever senses the dimensional changes upon particle exposure as a resistance change. This paper represents the integration of ac electroosmosis with a piezoresistive micro-cantilever sensor for the detection of bio-particles. A working prototype is presented here, and the experiments are conducted on Herpes Simplex type-1 virus (HSV-1) and Escherichia Coli (E. coli) bacteria.

The authors present a structure for coupler type narrow-band infrared filter and a wavelength de-multiplexer that is tunable by device parameters. Numerical simulation is realized in a two-dimensional (2D) plasmon polariton metal using finite difference time domain (FDTD) method with a perfectly matched layers (PMLs) boundary conditions. The filter can be used as a selective and rejection type plasmonic filter simultaneously; this is a unique feature of this filter structure. The tunable characteristics of the central wavelength of the filter are discussed. By using the filter, design of a 1x3 wavelength de-multiplexer is also outlined.

Deep brain stimulation is an effective surgical treatment for advanced Parkinson’s disease in patients whose symptoms are not well controlled by drugs. The subthalamic nucleus (STN), the globus pallidus pars externa (GPe), and the globus pallidus pars interna (GPi) are the targets for DBS. Despite over a decade of the practical clinical experience, the selections of DBS parameters are still challenging. DBS affects the local cells within the target site as well as the passing axons within neighboring regions. A computational model of basal gangliathalamic network is formed to analyze the performance of DBS at STN, GPe, and GPi in terms of error index. In addition to single-site stimulation, multiple-site stimulation is also analyzed for DBS of STN-GPe and STN-GPi in terms of error index. The goal of this work is to use computational modeling to analyze the effect of DBS of single-site stimulation (STN, GPe, or GPi) and multiple-site stimulation (STN-GPe or STN-GPi) with respect to stimulation amplitude and frequency.

This work represents active DNA concentration on piezoresistive microcantilever using biased AC electroosmosis. Two different sizes of DNA molecules, \alpha -phage DNA (48.5 kbp) and single-strand DNA of 20 nucleotides are concentrated on separate piezoresistive microcantilever sensor for detection. Before concentration, mixing of DNA molecules is performed using the same device for efficient concentration. During concentration of DNA molecules, biased and unbiased AC electroosmosis are needed to concentrate single-strand DNA and -phage DNA, respectively. Moreover, dielectrophoresis is induced by biased AC electroosmosis that can generate attractive force to transport negatively charged single-strand DNA. This paper represents a device configuration to integrate biased and unbiased AC electroosmosis and dielectrophoresis with piezoresistive microcantilever sensors for the detection of \alpha -phage DNA and single-strand DNA.

We have developed a micro-scale chip-based pH sensing system, which can effectively measure the changes in pH ranging from 1 to 4 and 10 to 12. This method relies on fringing field capacitive measurements. A change in pH of the medium results in a permittivity change for the fringing electric field, which in turn affects the capacitance values. Capacitance changes are then converted to resonant frequency shifts via a readout circuit. This technique provides high sensitivity, low hysteresis, and low noise as well as low fabrication cost. Very importantly, the device and the corresponding measurement circuitry have the potential to be integrated in an electronic pill for continuous non-invasive measurement within the body.

This work presents a technique for the chirality (n, m) assignment of semiconducting single wall carbon nanotubes by solving a set of empirical equations of the tight binding model parameters. The empirical equations of the nearest neighbor hopping parameters, relating the term (2n − m) with the first and second optical transition energies of the semiconducting single wall carbon nanotubes, are also proposed. They provide almost the same level of accuracy for lower and higher diameter nanotubes. An algorithm is presented to determine the chiral index (n, m) of any unknown semiconducting tube by solving these empirical equations using values of radial breathing mode frequency and the first or second optical transition energy from resonant Raman spectroscopy. In this paper, the chirality of 55 semiconducting nanotubes is assigned using the first and second optical transition energies. Unlike the existing methods of chirality assignment, this technique does not require graphical comparison or pattern recognition between existing experimental and theoretical Kataura plot.

Necessity for improved calculation of bandgap energies of semiconducting single wall carbon nanotubes is discussed. An effective empirical equation for nearest neighbor hopping parameter (γ0) in tight binding model of carbon nanotube is proposed in terms of nanotube diameter and chiral index combination. Bandgap energies of all semiconducting single-wall carbon nanotubes in between theoretical minimum and maximum diameter range are calculated from simplest tight binding model using this empirical γ0. Calculated bandgap values excellently match with experimental results over the full diameter range. The proposed hopping parameter greatly improves tight binding model, and remove its quantitative failure in predicting bandgap energy of nanotube.