Modeling of Air Relative Humidity Effect on Adhesion Force in Manipulation of Nano-Particles and its Application in AFM

In this paper, the effect of air relative humidity and capillary force on contact geometry of surfaces based on JKR model by Atomic force microscopy was investigated in order to manipulate nano-particles. With transition from macro to nano-scale, the effect of surface forces becomes more significant in comparison with inertial force. Because contact mechanics models are based on surface energy and there is a permanent humidity in surrounded environment. In order to precisely determine the forces in AFM dynamics equations and different environments and also their application in contact modeling, the effect of capillary forces must exactly be specified. Experimental results showed that the air relative humidity percentage affects the adhesion force. So, as AFM is used for fine and nano-scale particles. These forces have significant effect on operation accuracy and should not be neglected. In this paper, the effect of capillary forces has been modeled based on JKR contact mechanics model. The results obtained from this modeling have been compared with experimental data.