DESIGN AND CHARACTERIZATION OF A MINIATURE THREE-AXIAL MEMS FORCE SENSOR

Abstract

This paper reports the design, fabrication and calibration results of a miniature cross-shaped three-axial piezoresistive force sensor, which can simultaneously detect three force components in orthogonal directions. MEMS technology was used to fabricate the sensor structure and deposit a phosphosilicate layer on the silicon wafer to form piezoresistive resistors. Using the finite element simulation, the developed sensor performance characteristics, such as linearity, repeatability, sensitivity, and hysteresis, are analyzed for different arrangements of eight piezoresistors on the silicon beam surface. The sensor performance was experimentally validated by monitoring the voltage variation of Wheatstone bridge when a load-bearing rigid rod was loaded in three different directions by a set of weights. Calibration results exhibited linear output responses with the maximum linearity of 0.98 and small crosstalk below 7%. The MEMS sensor repeatability was tested with a commercial stepper motor by measuring a step function-varying profile force was applied to the sensor. Further optimization of the sensor design for sensing six degrees of freedom movement is envisaged with its sensitivity enhancement by the silicon substrate reduction.