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 2x1mm(2) dies. Each suspended thermopile is integrated with high-density thermocouples, allowing us to achieve a temperature sensitivity of similar to 27.8mV/degrees C. Such design ensures the detection of tiny temperature changes (down to similar to 1mK) caused by catalytic combustion of H-2-air mixture at 120 degrees C when the sensing thermopile is loaded with platinum nanoparticles-decorated aluminum oxide (Pt NPs@Al2O3) nanosheets. The sensors exhibit a linear response to H-2 concentration from 1.0% down to 5ppm with a response time of similar to 2.5s and a recovery time of similar to 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.