Principle of a Submerged Freeze Gripper for Microassembly

The development of reliable and repeatable strategies to manipulate and assemble microobjects lies in the efficiency, reliability, and precision of the handling processes. In this paper, we propose a thermal-based microgripper working in an aqueous medium. Manipulating and assembling in liquid surroundings can indeed be more efficient than in dry conditions. A comparative analysis of the impact of dry and liquid media on surface forces, contact forces, and hydrodynamic forces is shown. In addition, ice grippers represent flexible manipulation solutions. Nevertheless, when micromanipulation tasks are performed in air, capillary forces can drastically perturb the release. Our submerged freeze microgripper exploits the liquid surroundings to generate an ice droplet to catch microobjects, and to avoid capillary forces during the release. The thermal principle, the first microgripper prototype, an ice generation simulation, and the first tests are presented. The main objective is to validate the manipulation principle. Further research will be focused on control and optimization of the ice generation and the miniaturization of the system.