One-finger gripper based on the variable van der Waals force used for a single nano/micro-sized object

This article presents the development of a one-finger gripper that uses a variable van der Waals force to grip, transport and actively release a single SiO2 spherical-like nano/micro-sized object. The diameters of the objects used (spheres) were between 800 nm to 50 μm. The van der Waals force becomes the dominant force for such objects (from 60 nN to 8 μN) if the materials are not electrically charged or have magnetic characteristics, and if the medium between the object and the one-finger gripper is a vacuum. Furthermore, the van der Waals force is several times greater than the gravitational force for such objects, so a two-finger gripper becomes unreliable when actively releasing a nano/micro object. Usually, the nano/micro object remains attached to one of the fingers at an unknown position and orientation. Our newly developed one-finger gripper does not have such problems. The van der Waals force between the gripper and the nano/micro object is increased by the deposition of H2O crystals on the gripper's tip (gripping procedure), and decreased by sublimation of H2O crystals on the gripper's tip (releasing procedure). This article presents both the theoretical conditions for the gripping/releasing of rigid spherical-like objects and experimental proof of these conditions. The results of our practical experimentation show that the gripping/releasing method can be applied to any shape of object and also to different materials.