A new height-adjustable AeroMEMS surface fence probe fabricated in SOI technology for high resolution wall shear stress measurement in turbulent flows

A sophisticated sensor design of the AeroMEMS surface fence probe for wall shear stress measurements in turbulent flow is presented. The fence deflection (proportional to the wall shear stress) is directly measured by a piezoresistive Wheatstone bridge. The fence is 5 mm wide, max. 700 mu m high and 7 mu m and 13 mu m thick, respectively. The cantilever height is 1700 mu m or 2200 mu m. The sensing element rests on a 2 silicon body of 5200 x 7500 mu m(2). A sensitivity up to 6 mW(V-N/m(2)), a resolution of up to 10(-4) N/m(2) and a symmetrical behavior for bi-directional measurements were obtained in a measurement range of +/- 0.3 N/m(2). Two pn-diodes were implemented for temperature monitoring (sensitivity: -2 mV/K @ 100 mu A).