A CMOS MEMS Thermal Flow Sensor for Gas and Liquid With Parylene-C Coating

This brief presents a self-heated thermoresistive flow (SHTF) sensor for both gas and liquid with Parylene-C coating using a 0.35- \mu \text{m} CMOS MEMS technology. For N 2 flow, the developed SHTF sensor can achieve the highest normalized sensitivity ( S^{ \ast }{ =}\,\, {S}_{c} / {P} ) of 171 mV/(m/s)/W with its power consumption {P} of less than 18.3 mW. Meanwhile, the SHTF sensor has an accuracy of ±0.04 m/s within the linear flow range of 0-2.5 m/s, which is capable of indoor airflow measurement even in humid environment. For water flow, the SHTF sensor gains a sensitivity {S}_{W} ^{ \ast } of 6.42 V/(m/s)/W with the configured calorimetric setup, while its sensitivity increased by more than 4X as it assigned as anemometric for a Nusselt number Nu of 0-9. Therefore, this highly sensitive CMOS MEMS SHTF sensor with the coated Parylene-C will be a very useful device for both gas and liquid flow measurement in heating, ventilation, and air conditioning (HVAC) and microfluidic applications.