Heat transfer control of micro-thermoelectric gas sensor for breath gas monitoring

- Catalyst on the micro-TGS lowers the temperature and induces a biased voltage.
- Additive process of alumina dots changed the heat balance to controls the voltage.
- Heat transfer analysis by FEM modeling is performed to control the heat balance.

A micro-thermoelectric gas sensor (micro-TGS) uses thermoelectric voltage induced by the catalytic combustion of hydrogen or methane for selective gas detection in breath. This is accomplished under an elevated temperature using a micro-heater built on the same membrane as a hotplate, which enables selective combustion of the target gas. A temperature differential built by the catalyst on the membrane induces the offset voltage (Voff) of the micro-TGS, which limits the amplifier circuit application. In this study, we strived to suppress Voff by an additive integration process of heat dissipation dots prepared using α-Al2O3 paste. In this paper, we discuss the effects of these α-Al2O3 dots on the thermal balance over the micro-TGS membrane by finite element method (FEM) modeling. When the dots were deposited in a symmetrical position to the combustion catalyst, Voff was compensated depending on the size, numbers, and locations of the dots. The micro-TGS heat transfer control by the dots was additionally verified by 3-D FEM modeling. The changes in Voff by the α-Al2O3 dots in FEM modeling were greater than those of the experiments, suggesting the high thermal conductivity of the micro-TGS membrane. The deviation of the membrane thermal conductivity due to the process non-uniformity significantly influenced the Voff; however, it was effectively reduced by the additive integration of dots.