Showing papers by "Enakshi Bhattacharya published in 2010"

Dynamic response of polysilicon microcantilevers to enzymatic hydrolysis of urea

Abstract: Micromolar levels of urea [1–20 mM] on surface micromachined polysilicon cantilever beams immobilized with the enzyme urease was studied. Urea hydrolyses to ammonia and carbon dioxide which are volatile in nature. Monitoring the change in resonance frequency of a urease immobilized cantilever beam during the course of urea hydrolysis, mediated by the immobilized enzyme can give us information on the reaction rates. The change in the resonance frequency of the cantilever beams as a result of urea hydrolysis was measured using Doppler Vibrometry. The reaction kinetics of the enzyme urease was studied by analyzing the dynamic response of the enzyme immobilized microcantilevers for various concentrations of urea.

Packaged bulk micromachined triglyceride biosensor

Abstract: Estimation of triglyceride concentration is important for the health and food industries. Use of solid state biosensors like Electrolyte Insulator Semiconductor Capacitors (EISCAP) ensures ease in operation with good accuracy and sensitivity when compared to conventional sensors. In this paper we report on packaging of miniaturized EISCAP sensors on silicon. The packaging involves glass to silicon bonding using adhesive. Since this kind of packaging is done at room temperature, it cannot damage the thin dielectric layers on the silicon wafer unlike the high temperature anodic bonding technique and can be used for sensors with immobilized enzyme without denaturing the enzyme. The packaging also involves a teflon capping arrangement which helps in easy handling of the bio-analyte solutions. The capping solves two problems. Firstly, it helps in the immobilization process where it ensures the enzyme immobilization happens only on one pit and secondly it helps with easy transport of the bio-analyte into the sensor pit for measurements.

Design and fabrication of a micro-mirror for spectroscopy

Abstract: A wide variety of MEMS micro-mirrors are being developed for various optical applications. One such application is Fourier Transform Spectrometry (FTS). The design, process optimization and fabrication of a micro-mirror for this application is presented. Large, non-tilting displacements of mirrors are required to achieve high FTS resolution. In order to obtain this without using Deep Reactive Ion Etching (DRIE), the micro-mirrors were fabricated on silicon using bulk micromachining techniques. This paper will present 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.

Mitigating the irreversible deformation with pressure in silicon / porous silicon composite membranes

Abstract: Due to the low Young's Modulus of porous silicon (PS), Si/PS composite membranes - where the silicon membrane is converted into PS to a certain depth - deform more than silicon membranes and hence MEMS pressure sensors with composite membranes have higher sensitivity. But the Si/PS composite membranes exhibit a smaller range of linear response with applied pressure than silicon membranes with the linear range being less for Si/microPS as compared to Si/macroPS composite membranes. In addition, while the composite membrane deformation saturates at high pressures like silicon membranes, the deformation is irreversible unlike that seen with silicon membranes within reasonable limits. With the possibility that the irreversible deformation could be due to stiction force between the collapsed pore walls at high pressure, we investigate the effect of formation of self-assembled monolayer (SAM) antistiction coating on the performance of Si/PS composite membranes.