Metal oxide semiconductor (MOX) gas sensors are one of the most popular types of electronic noses due to their high sensitivity and affordability. MOX sensors detect gases by sensing the change in resistance of the sensing material, while being exposed to gases at elevated temperatures between 300ºC to 500ºC, which is achieved by applying electrical power to a microhotplate (&mgr;HP) that should be thermally insulated from the substrate to provide low power consumption as well as quick response time. The conventional method to deliver insulation is to micromachine the silicon wafer to suspend the &mgr;HP in air. That has some disadvantages, such as the low mechanical stability of the thin suspended membranes, the large sacrificed chip area to create the air gap for a single &mgr;HP, and the impossibility of lithographic processing of sensing material on top of the suspended layers. In this dissertation, a novel idea is proposed to use silica aerogel films as heat insulator rather than creating air gaps. The proposed idea is implemented practically and is demonstrated to offer power-efficient and area-efficient &mgr;HPs. Moreover, our state-of-the-art sol-gel processing (patent pending) suggests an easy method to prepare aerogel films avoiding the conventional supercritical drying and/or solvent exchange steps.
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