On the Forces between Micro and Nano Objects and a Gripper

The authors study the van der Waals force FvdW, between the gripper jaw and an object – cubical, spherical and conical in shape, situated at a distance L of closest approach from it. The generic and most general case is considered, when the materials of the working jaw of the gripper and the particle are made of different materials strongly preferring the liquid phase of the fluid being at temperature T and chemical potentialm. The contributions due to the standard van der Waals, as well as of the retarded (Casimir) van der Waals interactions are considered. They concluded that FvdW strongly depends on the contrast, at given fixed T and m, between the physical properties of the fluid and the material of the arms of the gripper and the particle. In addition, as expected, FvdW strongly depends on the shape of the object, its size, and the distance L between it and the working jaw of the gripper. Their approach can be applied to any nonpolar fluid.