A polymeric microgripper with integrated thermal actuators

Abstract

This paper describes the design, simulation, fabrication and characterization of a polymeric microgripper with integrated thermal actuators. The microgripper was fabricated by a polymeric surface micromachining process, which utilizes SU-8 as the functional material and silicon as the sacrificial material. A thin double layer of titanium and platinum was evaporated on the gripper structure and served as the electrically conducting and heat dissipating material. The polymeric microgripper offers the advantage of large displacement and gentle handling forces, which may be ideal for handling bioparticles such as cells. Furthermore, an operating temperature below 100 °C allows the handling of living cells and tissues. The unique characteristic that SU-8 does not soften at elevated temperature allows the use of thermal actuation for the microgripper. To the best knowledge of the authors, the presented device is the first polymeric microgripper with integrated actuators. Each thermal actuator consists of two thin arms and one thick arm. Heat is generated by electrical current passing through the thin titanium/platinum on top of the 100 µm thick SU-8 structure. Based on an electrical/thermal/structural coupled simulation, the gripper can operate in both normally closed mode and normally open mode. The different electrical configurations of the gripper arms allow this flexibility. Results of the simulation and the measurement are also presented in this paper.