Design, modeling, and characterization of a MEMS micro-gripper with an integrated electrothermal force sensor

With growing developments in biomedical research and micro industrial applications, there is a demand for micro-grippers that are reliable and can operate with high precision. This paper presents a MEMS micro-gripper with an integrated electrothermal force sensors. The microgripper is actuated by electrostatic comb-drives. Electrothermal resistive sensors are used to measure the gripping force. In this arrangement, the sensing arms deflection induces a temperature difference between two identical resistive sensors, biased at the same voltage, which results in current variation in the resistors. The currents are then converted to an output voltage using a half Wheat-stone bridge and an instrumentation amplifier. With the sensing displacement information available, the gripping force can be calculated. The device was designed and fabricated in a commercial Silicon-On Insulator MEMS foundry (MEMSCAP). A pick-and-place operation on 85 μm micro-beads on 3-axis micro-positioner is performed to evaluate the performance of the device. The experiment shows that the micro-gripper is able to handle a wide range of micro-sample sizes with biocompatibility and gentle handling forces.