Colloidal Interactions for Nanopatterned Surfaces Based on Surface Element Integration (SEI) Approach

Abstract

In this study, van der Waals and electrostatic interaction energies on a nanopatterned rough surface was investigated. Surface element integration method (SEI) was applied to determine the interaction between a nanostructured substrate and an infinite flat plate. Hemispherical protrusions or depressions were mathematically generated on a square lattice to represent the rough surface. The size of the asperities and the pitch (separation) between their centers were varied. From the above calculations, we have analyzed the coupling between the range of the interactions and the roughness features of the substrate by comparing the ratios of the rough surface to smooth surface interaction energies per unit area. At small separations, the rough surface van der Waals interaction is seriously attenuated in the presence of protruding asperities. This attenuation is less pronounced for depressions. The attenuation of the van der Waals interaction due to asperities diminishes at large separations. In contrast, attenuation of the electrostatic interaction is independent of the separation.