Anju Chadha

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. © 2010 Copyright SPIE - The International Society for Optical Engineering.

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. © 2011 Elsevier B.V. All rights reserved.

Electrolyte insulator semiconductor capacitors (EISCAPs) show a shift in the measured capacitance-voltage (C-V) characteristics with changes in the pH of the electrolyte and has the potential to be used as biosensors. The choice of an electrode to the EISCAP is important for reliable measurements. Here, we discuss a silicon-based EISCAP sensor bonded to a glass wafer with an embedded electrode. Three noble metal electrodes (Pt, Au, Ag) are studied for the ease of integration and performance and it is found that the chloridized Ag electrodes exhibit the highest pH sensitivity and the lowest electrode potential drift with time. A readout system that measures the pH of the electrolyte under test is developed and implemented in a programmable system on chip. Calibration of the EISCAP to account for sensor process variations is also incorporated. The pH measurement data on the miniaturized EISCAPs is presented. © 2001-2012 IEEE.