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.