Finite Element Simulation and Analysis of Nano-Scale Adhesive Contacts

Abstract

A finite element method for analysis of adhesive contact is developed to model adhesive contact of an elastic hemisphere with a rigid plane, in which the adhesive pressure is derived from the interatomic interaction Lennard-Jones 12-6 potential. Contact forces during retraction and the pull-off force are analyzed and compared with the analytical results of JKR and DMT models. Adhesive contact models with different geometrical shape in the contact zone are also set up. It has been revealed that pull-off force increases while pull-off distance decreases when the contact zone is patterned by hole. The method of equivalent radius only applies for Hertz contact and does not apply for adhesive contact. Higher pull-off strength is get from smaller radius of contact tip, as predicted by experiment. Also, the tip geometry plays an important role in pull-off strength. It is anticipated that this numerical method can be applied in surface profile design for MEMS to reduce adhesion and tip design for the sticky feet in bionics to increase adhesion.