Design of a high sensitivity capacitive force sensor

This paper presents the design and development of a MEMS based, capacitive sensor for micro-force measurement. The sensor has an overall dimension of 3600 mum times 1000 mum times 10 mum and was fabricated using the Micragem fabrication process. A displacement reduction mechanism is incorporated in this sensor design to increase the sensitivity of the sensor. Analysis from Finite Element software, COMSOL, confirms that a 10:1 displacement reduction ratio is achievable with this mechanism. Simulation results show that the sensor is capable of measuring a maximum force input of 11 milli-Newton, resulting from a 20-mum displacement on the sensing structure. A 6-DOF manipulator and an evaluation board were used to experimentally verify the performance the sensor. Experimental results show that a capacitance change of approximately 175 to 200 fF can be observed from a 20-mum displacement.