Nrashant Singh

Multiple approaches to evaluate the toxicity of the biomass fuel cow dung (kanda) smoke.

Cow dung (Kanda) is a major source of energy in rural and urban population of developing countries and is burnt in traditional open stoves in confined space of kitchen without proper ventilation. In epidemiological studies, biomass fuel smoke has been reported to be responsible for several respiratory disorders in exposed population. In a laboratory experiment, female wistar rats were exposed to kanda smoke for 60 min/day over a period of 12 weeks. Chemical analysis of smoke showed the presence of PAHs. The increase in CYP1A1, GST-ya, GST-yc expression was found in 12 week exposed lung tissues as compared with controls. The exposure to smoke resulted in significant alteration in the BALF cells in the form of clustering of alveolar macrophages and giant cell formation with vacuolated cytoplasm. The macrophages also showed thickness and villi like projections on the cell surface thus reducing their phagocytic activities. Histopathological changes in lung tissue were manifested in the form of damage to bronchiolar epithelium, edema and thickening of alveolar septa and emphysema after 4 and 8 week of exposure. These findings suggest that exposure to kanda smoke increases pulmonary tissue damage and may result in various forms of respiratory infections in the exposed popultion.

Silicon Nanowire Array Bio-Sensor using Top-Down CMOS Technology

The paper elaborates the Silicon Nanowire arrays fabrication using standard CMOS compatible technologies (top-down) with each array consisting of 100 wires, which are individually electrically measurable for their conductance and facilitating statistical analysis. The arrays are integrated with micro-fluidics for the delivery of various chemicals for surface modification, buffer solutions, biomolecules/ analytes, etc. Biotinylated-ssDNA is detected electrically, label-free by the nanowire sensors modified by streptavidin; further DNA hybridization is also observed similarly on sensors modified by complementary DNA probes. Our approach paves way for realizing high-density, highly sensitive biological and chemical sensors using mass fabrication technologies and thus has the potential to achieve multiplexed detection which is essential for understanding and curing of complex diseases.

Transport Characteristics of Si Nanowires in Bulk Silicon and SOI Wafers

Silicon nanowires (SiNW) were fabricated on bulk Silicon and SOI wafers by means of conventional Si process technology. The nanowires were formed by stress-limited oxidation of Si beams pre-patterned on the wafer. Single or double vertically self-aligned wires were obtained depending on the bulk or SOI wafer used and also on the depth of silicon beam etched. The resulting nanowires exhibit triangular cross-section that can be converted to circular shape by annealing at high temperatures, exploiting the visco-elastic properties of SiO2and Si. Electrical measurements on single nanowire show that the resistance scales with length demonstrating consistent cross-sectional dimension in wires of different length. The nanowires formed on SOI wafers were also characterized as channels in FET configuration, using substrate as gate electrode. This technique can be exploited for realizing several nano-electronics, NEMS and biosensor applications in bulk silicon or SOI wafers, all in a CMOS compatible manner.

Silicon Nanowire Field Effect Devices By Top-Down CMOS Technology

There has been tremendous advancement in the development of novel nano-technologies for future CMOS nanoelectronics. The challenges and opportunities have been widely discussed with the focus on the choice of materials, processes of implementation and innovative non-classical device architectures to continuously meet the scaling requirements. Among the non-classical device architectures, Gate All Around (GAA) FET with nanowire (NW) channel body offers the ultimate electro-static control and thus has the potential to push the gate length to few nanometers. The key challenge for NWs to be widely adopted in semiconductor industry is that they have to be formed by large scale manufacturing methods. Especially, for CMOS applications, the methods should not lead to contamination issues.