High Heat Transfer Efficiency MEMS Thermal Conductivity Gas Sensor for Hydrogen

In this paper, a high heat transfer efficiency MEMS thermal conductivity gas sensor based on three suspended bridges is demonstrated. The sensor is composed of three platinum thermistors of which one is as the heater element and the other two are as the temperature-sensing elements. The heater provides a stable heat source, and the temperature-sensing elements reflect the gas signal. To improve the temperature detection ability of the temperature-sensing elements, the heater is designed into a serpentine-shaped structure, and the temperature-measuring elements are also adapted to a serpentine shape. In addition, the temperature-measuring elements are close enough to the heater to reduce the heat transfer distance and improve the heat transfer efficiency. Simulations and experiments compared two complementary structures of suspension bridge gas sensors including a shuttle-shaped heater (Design 1) and a dumbbell-shaped heater (Design 2). The results show that the sensor of Design 2 has higher heat transfer efficiency and higher sensitivity to hydrogen, and exhibits a low detection limit of 0.2%. Furthermore, the gas sensor realizes excellent reproducibility for 2% Hydrogen in long-term tests.