A study of capillary forces as a gripping principle

Purpose - This work aimed at studying the use of capillary forces as a gripping principle in the handling of sub-millimetric sized components. The goal was to present the results as design rules of so-called capillary grippers. Design/methodology/approach - Each parameter (surrounding environment, materials, volume of liquid, separation distance, gripper geometry and gripper size, relative orientation of the gripper with respect to the component) has been quantified, either numerically or experimentally. In some validation cases, both means have been used. Findings - The capillary forces can be modified between a maximum F-max and a minimum F-min so that a component with any mass m between F-min/g and F-max/g can be picked up and released. Research limitations/implications - By comparison with some existing capillary grippers prototypes, this work is only a theoretical and experimental study. Nevertheless, its originality lies in the exhaustive study and quantification of all parameters so that-most of the capillary grippers of the literature can be explained or improved with these results. Practical implications - The main implication of the capillary gripping is that it provides an alternative to existing gripping principles (vacuum grippers, tweezers). This principle is strong enough (a few mN) and well adapted to pick up components with only one free accessible surface. The scaling laws are the most favorable (F similar to L). It provides a soft picking, avoiding high contact forces. Originality/value - The originality lies in the exhaustive quantification of the role of each parameter. These results can be used by researchers and designers.