Enhanced Response of Co-Planar MEMS Microheater-Based Methane Gas Sensor

A high performance coplanar MEMS microheater based gas sensor, in respect of its portability and power consumption, with enhanced response, has been designed, fabricated and characterized. Pt microheater, along with interdigitated electrodes (IDE) and Methane sensing layer were deposited on micro machined silicon substrates. Performance of the microheater was analyzed in terms of power consumption and heat distribution uniformity. Existence of a leakage voltage was detected which was found to reduce the overall sensor performance. Source of this leakage voltage was theoretically and experimentally investigated. To reduce the effect of such leakage voltage on sensor performance, a low drift OPAmp based high gain cancellation circuit was subsequently designed, implemented and an enhanced response of about 70% was observed as against 40% for uncompensated coplanar sensors. An exhaustive sensor characterization study was carried out for different concentrations of methane and performance was analyzed in terms of sensitivity, response, recovery time etc. A sensitivity of about 73% was observed for 5000ppm methane concentration with a moderate response (110 sec) and good recovery (30 sec) time.