MEMS Differential Thermopiles for High-Sensitivity Hydrogen Gas Detection

We report a MEMS differential thermopile sensor for high-sensitivity hydrogen (H
2
) gas detection. By exploiting the single-sided microhole inter-etch and sealing (MIS) process, pairs of MEMS single-crystalline silicon thermopiles are batch fabricated into 2×1mm
²
dies. Each suspended thermopile is integrated with high-density thermocouples, allowing us to achieve a temperature sensitivity of ~27.8mV/°C. Such design ensures the detection of tiny temperature changes (down to ~1mK) caused by catalytic combustion of H
2
-air mixture at 120°C when the sensing thermopile is loaded with platinum nanoparticles-decorated aluminum oxide (Pt NPs@Al
2
O
3
) nanosheets. The sensors exhibit a linear response to H
2
concentration from 1.0% down to 5ppm with a response time of ~2.5s and a recovery time of ~1.7s (in 1% H
2
), which are more sensitive than the previously reported MEMS thermopile H
2
sensors. The proposed sensors are also selective against other combustible gases and remain stable after 30 days. Our highly-sensitive, cost-effective MEMS differential thermopile sensors hold promise for H
2
leakage detection in industrial applications.