Fabrication and characterization of high-sensitivity, wide-range, and flexible MEMS thermal flow velocity sensors.

With the rapid development of various fields, including aerospace, industrial measurement and control, and medical monitoring, the need to quantify flow velocity measurements is increasing. It is difficult for traditional flow velocity sensors to fulfill accuracy requirements for velocity measurements due to their small ranges, susceptibility to environmental impacts, and instability. Herein, to optimize sensor performance, a flexible microelectromechanical system (MEMS) thermal flow sensor is proposed that combines the working principles of thermal loss and thermal temperature difference and utilizes a flexible cavity substrate made of a low-thermal-conductivity polyimide/SiO (PI/SiO) composite porous film to broaden the measurement range and improve the sensitivity. The measurement results show that the maximum measurable flow velocity can reach 30 m/s with a resolution of 5.4 mm/s. The average sensitivities of the sensor are 59.49 mV/(m s) in the medium-to-low wind velocity range of 0-2 m/s and 467.31 mV/(m s) in the wind velocity range of 2-30 m/s. The sensor proposed in this work can enable new applications of flexible flow sensors and wearable devices.