Hot-wire-type micromachined chemiresistive gas sensors for battery-powered city gas alarms

Abstract Metal oxide semiconductor (MOX) chemiresistive gas sensors used in gas alarms have contributed to the safe use of city gas and liquid petroleum gas. In this study, we successfully fabricated hot-wire-type MOX sensors using micro-electro-mechanical systems (MEMS) technology. The hot-wire type structure, in which an electrode plays dual roles in detecting and heating, was adopted for efficient production. Owing to the miniaturization together with the thermal insulation, the sensors exhibited a fast thermal response. The average power consumption of the sensor in the pulsed operation was less than 100 μ W. The sensor exhibited high sensitivity of more than 100 mV to 3000 ppm methane and showed low cross-sensitivity to interference gases such as ethanol and hydrogen. These sensing properties were retained for more than five years, demonstrating excellent long-term stability of the sensors.