Capillary Force Gripper for Complex-Shaped Micro-Objects With Fast Droplet Forming by On–Off Control of a Piston Slider

In this letter, we describe the newly proposed capillary force gripper that combines fast water refilling via the capillary phenomenon and fast droplet forming via the ON-OFF control of a piston slider. The capillary force is suitable for capturing and releasing heterogeneous and complex-shaped micro-objects because it is one of the most dominant forces in the microscopic world and acts on any shaped objects by the water flexible deformation. However, a water droplet easily evaporates and loses during every pick-and-place operations. To solve this problem, we developed a gripper that can quickly form droplets with simple control. In the experiments, we confirm that the gripper can generate a sufficient capillary force to grip a 1-mm3 micro-object for over 100 s. Furthermore, we realize the automatic pick-and-place of cube, cone, and semicylinder samples. We compare the positioning errors among them to discuss the feasibility, future prospects, and applications in electronics and MEMS fields.