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Shan Hu, Ahmed Busnaina and Jin-Goo Park

Accurate Calculation of the Double Layer Force in Particle Removal and Assembly

The removal of nano-scale particles is a challenge to semiconductor manufacturing and other industries. On the other hand, the assembly of nanotemplate requires nanoelements such as nanoparticles and carbon nanotubes to adhere to predetermined precise locations. Therefore, adhesion and removal of small particles from surfaces is of great importance to directed self assembly. Based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, there are two main forces here: van der Waals force and electrical double layer force. Although the fundamental theory for the electrical double layer interaction between colloidal particles has been established for more than half a century, analytic expressions for the forces and free energies of interaction, even for spherical particles, are only available as approximate expressions. Each approximate expression is derived under certain assumptions and conditions. By comparing with experimental results, the “Compression” approximation under constant charge assumption is found to be suitable to the case of a sphere in contact with a flat surface.