Development of a High-Sensitive MEMS Calorimetric Flow Sensor Based on NTC/Mica Films

Calorimetric flow sensors are preferred for low-flow detection owing to their superior sensitivity. However, the conventional designs exhibit certain limitations, i.e., low measurement accuracy and fabrication complexity. This study introduces an innovative sensor architecture by integrating negative temperature coefficient (NTC) films with ultrathin mica substrates. The high-sensitivity NTC film (B =3720 K and TCR =4.3%) achieved precise temperature differential detection via enhanced on-chip monitoring. It is further supported by the thin mica substrate ( $40~\mu $ m thickness) exhibiting exceptionally low thermal mass (heat capacity <0.85> $\cdot $ K and thermal conductivity <0.55> $\cdot $ K). This optimized design and process significantly improved the resolution and sensitivity of the sensor. Based on the segmented fitting results of the velocity– $\Delta T$ relationship, it was observed that the optimized calorimetric flow sensor achieved a high sensitivity of up to 1.93 m/s over a flow range of 0.01–0.1 m/s ( ${R}^{{2}} =0.998$ ), with a resolution accuracy of 0.01 m/s. The response time of the flow sensor was measured to be 0.49 s. The repeatability and stability were also verified with a standard deviation that was lower than 2%. The flow sensor herein exhibited superior performance with a simple fabrication process relative to conventional silicon-based heat flow sensors. Furthermore, it also exhibited good application potential in respiratory monitoring, indicating strong suitability for wearable health devices and medical monitoring systems that require high-precision flow measurements.