A Novel MEMS Sensor with a Floating Cover Plate for Wall-Shear Stress Measurement in the Harsh Supersonic Flow

This work presents a novel capacitance MEMS sensor with a floating cover plate for robust wall-shear stress measurements in the harsh environment of supersonic flow field. Based on a Dual Silicon-On-Insulator (DSOI) wafer, the specific microfabrication technology is developed to achieve the combination of the floating cover plate and sensing structure, which features the accurate etching, anodic bonding, and backside TGVs' lead wire. A two-dimensional Poiseuille channel was established to carry out the sensor calibration. Moreover, the enormous reduction of damaging possibilities of the sensor in practical applications is experimentally verified. Wall-shear stress measuring experiments were performed at a Mach 2.0 supersonic wind-tunnel facility. The entire period of the supersonic flow from beginning and stabilization to end was observed by the proposed sensor, where shear stress fluctuations caused by the near-wall flow field structure were acquired. Additionally, the experimental results matched the pattern of changes in the wall pressure, and indicated the agreement with the model predictions for fully developed boundary layers.