Flexible MEMS shear stress sensor with improved performance for wind tunnel measurements

This paper describes a flexible micro-electro-mechanical system (MEMS) shear stress sensor, fabricated on a polyimide substrate using sputtering and a lift-off technique. The width of the nickel thermistor is minimized to several microns by an optimized manufacture process. The performance of the nickel thermistor is notably enhanced by heat-treatment during the fabrication. The sensor’s characteristics are tested, including the temperature coefficient of resistance (TCR), time constant (cutoff frequency), and sensitivity. As a result of the optimized fabrication and the appropriate annealing heat-treatment, the TCR of the nickel thermistor is high, which has a considerable effect on the sensitivity; these techniques and results are an improvement on results in literature. The cutoff frequency test and sensitivity calibrations of the sensor were performed in a wind tunnel. The results show that the improved sensor with higher TCR and smaller size can be used in wind tunnel measurements effectively.