Fabrication and Characterization of Dual Coordinate Self Examined Thermal Flow Sensor Arrays based on Longitudinal Heat Conduction

Thermal flow sensors have been widely used in wind energy utilization, dangerous chemicals detection, automobiles, intelligent robots and unmanned aerial vehicles (UAV). New applications put forward higher requirements for detecting parameters of a two-dimensional (2-D) gas-flow vector over a full range of 360°. A novel thermal flow sensor on Si/SiO2/Pt/AlN substrate is presented to optimize sensor parameters. Eight thermal elements patterned as equally divided sectors of a regular octagon compose the sensor probe. Dual coordinate systems are created based on the regular octagon distribution to realize the self examined function. The longitudinal heat conduction mode shortens the heat transfer distance from mm level to micron level. And the a-axis oriented AlN film improves the heat transfer efficiency due to its high thermal conductivity. Dual coordinate self examined method is proven through experiments for the first time. Measurement results show that the maximum measurement flow velocity is up to 37m/s, with an output voltage sensitivity of 28.1 mV/(m/s). Flow direction was measured over a full range of 360° with an accuracy of 0.5 m/s at low velocity and 5% at high velocity. We believe that the sensor presented in this work will pave the way for novel applications in calorimetric sensors and array sensors.