Monolithic CMOS-MEMS Thermal Conductivity Detector with On-Chip Integrated Microchannel for Rapid and Flow-Insensitive Gas Identification

We present a CMOS-MEMS micro thermal conductivity detector ($\mu$TCD) that integrates a suspended microheater within an on-chip microchannel, enabling rapid and flow-insensitive gas mixture identification. The$5.32 \mu ~\mathrm{m}$thick microchannel operates in a diffusion-dominated regime that shields the microheater from flow disturbance. Consequently, the$\mu$TCD achieves a normalized flow interference (NFI) as low as 0.22 % under an$\mathrm{N}_{2}$flow up to 7000 sccm. In$\mathrm{N}_{2}$-He mixtures, the measured heating power of$\mu$TCD increases from 2 mW to 6 mW as He concentration rises to 100 %, with the output trend closely matching theory and yielding a maximum sensitivity of$4.38 \text{mV} / \%$. Benefiting from a noise floor below$12 \mu ~\mathrm{V}$even under flow conditions, the$\mu \text{TCD}$achieves a resolution of 54.3 ppm. Moreover, it exhibits rapid response/recovery times of$0.55 / 0.53 ~\mathrm{s}$, along with good repeatability (RSD$