This paper proposes a novel microgripper with two working modes. The microgripper is designed with symmetric structure and each part is actuated by one piezoelectric actuator, respectively. To achieve desired output displacement, each part of the microgripper is designed with three-stage amplification mechanism to amplify the displacement of the PZT actuator. According to the size of the microobjects, the grasping operation can be completed by one finger moving or two fingers moving simultaneously. Then, the theoretical analysis is carried out to calculated the key characteristics, including amplification, input stiffness and frequency. Finite element analysis (FEA) is conducted to optimize the structural parameters and investigate the performance of the microgripper. Finally, a prototype is machined by wire electro-discharge machining (WEDM) method and experiments are carried out to verify the performance of the microgripper. The results indicate that the amplification is 10.41 and the motion stroke of one jaw is 118.34 µm when the input voltage is 100 V. The first natural frequency is 746.56 Hz. By picking and placing the wires with different diameters and slices with different thickness, the grasping stability is verified.
Keywords: bridge type mechanism; mechanism design; microgripper; micromanipulation.