Design and Fabrication of a Four-Arm-Structure MEMS Gripper

This paper is focused on the design and fabrication of a four-arm-structure microelectromechanical systems gripper integrated with sidewall piezoresistive force sensors. Surface and bulk micromachining technologies are employed to fabricate the microgripper from a single-crystal silicon wafer (i.e., no silicon-on-insulator wafer is used). A vertical sidewall surface piezoresistor etching technique is used to form the side direction force sensors. The end effector of this gripper is a four-arm structure: two fixed cantilever arms integrated with piezoresistive sensors are designed to sense the gripping force. The resolution of the force sensor is in the micronewton range and, therefore, provides feedback of the forces that dominate the micromanipulation processes. An electrostatically driven microactuator is designed to provide the force to operate the other two movable arms. In this way, it creates a deflection of 25 mu m at the arm tip, and the range of the operation is 30-130 mu m. Experimental results show that it can successfully provide force sensing and play a main role in preventing the damage of microparts in micromanipulation and microassembly tasks.