Design, simulation and testing of polymeric microgrippers with V-shaped electrothermal actuators and encapsulated heaters

This paper presents the design, simulation, fabrication, and characterisation of polymeric microgrippers based on V-shaped electrothermal actuators for bio-micromanipulation and microassembly applications. The microgrippers were simulated using FEM in order to determine the electro-thermo-mechanical behavior. The microgrippers were fabricated using the SU-8 biocompatible polymer as structural material. The metallic microheaters were encapsulated in the polymeric structural layers of the microgrippers to improve thermal efficiency and to reduce the undesirable out-of-plane displacement of the gripper. Electro-mechanical testing and characterisation have been performed to determine the openings of the microgripper tips as function of electrical current. For the evaluation of the microgripper displacement, a measurement based on an optical image approach was used. A displacement of 40 μm can be obtained for an electrical current of around 25 mA. Over 26 mA the heaters are still working but a softening and a damaging status in the polymer were observed. A comparison between the simulation results and the displacement measurements is presented.