Showing papers by "Enakshi Bhattacharya published in 2011"

Potentiometric estimation of blood analytes—triglycerides and urea: Comparison with clinical data and estimation of urea in milk using an electrolyte–insulator–semiconductor–capacitor (EISCAP)

Abstract: A modified electrolyte–insulator–semiconductor–capacitor (EISCAP) developed in-house was used for the determination of triglycerides and urea in blood, in addition to urea in milk. The sensitivity of the sensor was 55 ± 0.5 mV per unit change of pH. The EISCAP was optimized to operate at 25 °C in 0.25 mM phosphate buffer (pH 6), 1 M KCl and 1 mg lipase for triglycerides and in 1 mM Tris–HCl buffer (pH 7.4), 0.5 M KCl and 0.5 U urease for urea. Comparisons of the results obtained from the developed biosensor and clinical records gave correlation coefficients of 0.979 and 0.974 for blood triglycerides and blood urea respectively. Similarly, estimation of milk urea determined using the sensor in comparison with the spectrophotometric method gave a correlation coefficient of 0.992. The sensor gave reproducible and reliable results up to six months.

Nanoporous silicon membrane for biomolecular separation

Abstract: Separation of biomolecules based on their size and charge is an important procedure employed in biomolecular analysis. Nanosieve comprising of a semi-permeable membrane with nanometer-sized pores is used for this purpose. Described here is the fabrication of ultra thin nanoporous silicon membrane, which can be used as nanosieve, making use of standard microelectronics fabrication techniques. Lithography and bulk silicon etching is used to initially create a 10 μm thick sacrificial membrane in the center of a 200 μm thick silicon substrate. A three-layer stack of SiO2, amorphous silicon (a-Si) and SiO2 is then deposited using chemical vapor deposition technique. The sample is subjected to rapid thermal annealing during which pores are formed in the a-Si layer. Finally, the 15 nm thick nanoporous silicon membrane is released using reactive ion etching of the sacrificial membrane. The formation of the pores is confirmed by transmission and scanning electron microscope images. At present the pore formation is random; our future work will focus on controlled nucleation of silicon nanocrystals so as to get pores at desired locations.

Design and Fabrication of a Micro-Mirror for Low-Resolution Spectroscopy

Abstract: A wide variety of MEMS micro-mirrors are being developed for various optical applications. One such application is Fourier transform spectroscopy (FTS). The design, process optimization, and fabrication of a micro-mirror for this application are presented. Large, nontilting displacements of mirrors are required to achieve high FTS resolution. Although, certain applications require lower resolution, the mirror still needs to be nontilting. In order to obtain this without using deep reactive ion etching (DRIE), the micro-mirrors were fabricated on silicon using bulk micromachining with wet chemical etching. This paper presents the process developed for fabrication of the mirror with the required specifications. In addition, results of the FTS experiments conducted with the micro-mirror will also be presented.