MEMS-based shear-stress sensor for skin-friction measurements

A new MEMS-based shear-stress sensor has been developed for skin-friction measurements in wind tunnel tests. This new sensor design utilizes polysilicon bridges on silicon substrate as heating and sensing elements, greatly simplifying the fabrication process and increases the yield by eliminating the silicon nitride diaphragm and vacuum cavity in conventional MEMS shear-stress sensors. Since the bridge structure is totally exposed to the medium, its sensitivity to the fluid flow is also improved. By aligning two sets of the sensing elements in orthogonal directions in the new shear-stress sensor design, both the magnitude and direction of air flows can be determined, which has been confirmed by lab tests with a mini wind tunnel.