A MEMS surface fence for wall shear stress measurement with high sensitivity

In this paper, an optimized micro-fabricated surface fence with high sensitivity is presented for measurement of wall shear stress. In order to improve the bending stress and thereby enhance the sensitivity of the sensor, the cantilever structure of sensor (the sensing element) is designed and optimized by optimization analysis and orthogonal experimental design. Several sensors are fabricated using the micromachining technology with the sensing element having a width of 5 mm, a thickness of 20 μm and a height of either 2,200 or 1,700 μm. Calibration against a Preston Tube over a range of approximately ±0.7 Pa demonstrates that the sensors have sensitivity extended up to 2.3 mV/(V·Pa), at least 13 % improvement in sensitivity compared to the previous MEMS surface fence with the same thickness of sensing element. The paper also introduces an acoustic excitation method to detect the resonant frequency of the MEMS surface fence, which features a very little deviation compared with the modal FE-analysis.