Characterization of microfabricated shear stress sensors

This paper reports a dual effort to fabricate and calibrate micromachined shear stress sensors for wind tunnel instrumentation. Our team at CWRU has designed and fabricated both active and passive shear stress sensors based on microfabricated polysilicon lateral resonant structures. In addition to this effort, we have collaborated with Analog Devices to develop shear stress sensors with integrated electronics based on existing accelerometer devices and process technology. Sensors from both efforts have been tested in a macroscopic flow channel for characterization in compressible flow. The sensors from CWRU were optically calibrated at 9 Pa/μm of floating element deflection. The integrated sensors demonstrated a nominal sensitivity of 6 Pa/V. Packaging issues were found to be critical for proper sensor design and calibration. Misalignment of a few degrees from parallel to the fluid flow results in an order of magnitude difference in integrated sensor output