A flexible MEMS technology and its first application to shear stress sensor skin

A new microfabrication technology that enables the integration of MEMS devices on a flexible polyimide skin has been developed. Mechanically, the flexible skin consists of many individual Si islands (necessary for silicon MEMS/electronics devices) that are connected together by a thin/thick polyimide film (typically 1-100 mu m thick). To create the islands, Si diaphragms are first formed with a desirable thickness (10-500 mu m) by Si wet etching and then patterned from the back side by reactive ion etching (RIE). As a first application, flexible shear-stress sensor skins for aerodynamics study have been fabricated. The finished skin is 3 cm long and 1 cm wide, and it consists of about 100 sensors. The skin polyimide is 17 mu m thick and the silicon islands are 75 mu m thick. These skins have been successfully taped on a semi-cylindrical (1.3 cm diameter) delta wing leading edge to perform real-time 2-D shear stress profiling.