Double-Nozzle Capillary Force Gripper for Cubical, Triangular Prismatic, and Helical 1-mm-Sized-Objects

In this letter, we describe a novel capillary force gripper with two nozzles for the manipulation of complex-shaped micro-objects. These nozzles rapidly form constant-volume droplets and have two primary functions: fast water refilling by capillary action and fast droplet formation by the on-off control of a diaphragm pump. Capillary force is a dominant microscopic force acting on objects of all shapes owing to the fluidity of water. Therefore, it is suitable for the capture and release of heterogeneous and complex-shaped micro-objects. In the experiments, we picked and placed 1-mm cubes, triangular prisms, and helical micro springs. The positioning errors ±SD for each shape were 54 ± 36 μm, 85 ± 32 μm, and 162 ± 74 μm, respectively. These prisms and springs are difficult to control using conventional air nozzles, which have a typical positioning accuracy of approximately ± 40 μm for rectangular prismatic objects. In addition, by setting the distance between the nozzles to an appropriate value, we reduced the deviation of the attitude angle around the vertical axis to ±2.6° using self-alignment phenomena for the 1-mm cubes. The proposed method is feasible for manipulating complex-shaped and fragile micro-objects in the micro-electro-mechanical systems field.