Development of a microelectromechanical system pressure sensor for rehabilitation engineering applications

Based on computer finite-element analysis ANSYS 5.3 and microelectromechani cal systems (MEMS) technologies, a micropressure sensor was designed and fa bricated. The sensor can be used to measure the distribution of normal stre ss between soft tissues on an above-knee amputee's skin and the contacting surface of a rehabilitation device. A square membrane with dimensions 2400 mu m x 2400 mu m x 80 mu m is formed by backside photolithography and wet e tching of an n-type [100] monolithic silicon wafer. On the middle of the me mbrane edge, an X-shaped silicon wafer was implanted with boron ions and th en enhanced by diffusion to form a piezoresistive strain gauge. In the desi gn process, a finite-element method is used to analyse the effects of press ure sensitivity and its temperature coefficients. The developed micropressu re sensors, which have smaller weight and volume than a conventional machin e type, perform well and fit our design specifications.