A Submerged Freeze Microgripper for Micromanipulations

Efficient, reliable and flexible handling is still very challenging in micromanipulation and micro-assembly. In this paper, we propose an original thermally actuated gripper based on the use of ice to manipulate submerged artificial micro-objects sized under 100 mum. Manipulating in liquid surroundings can indeed be more interesting than in dry conditions. A comparative analysis on the impact of dry and liquid media on surface forces, contact forces and hydrodynamic forces shortly given first shows it. Concerning the use of ice for micromanipulation, cryogenic grippers are a flexible solution. Nevertheless, as they currently work in air, water must be provided by an external device and capillary force occurs during the release. Our submerged freeze microgripper takes advantages of the aqueous surroundings for the handling process as explained. The thermal principle, based on the Peltier effect, the characteristics of the microgripper prototype and the first micromanipulation tests are also presented. To control and optimize the heat exchanges in the developed gripper, a static thermal model using electrical analogy has been developed and validated for the Peltier elements and a 3D heat sink of the gripper. Further work will focus on the dynamic equivalent electric model.