Different from the short-range van der Waals interactions, the electrostatic forces can exert their influence across a much longer distance, which cause profound changes in the structure of a particulate system and offer the ability to manipulate particles at the microscales. One of these electrokinetic phenomena related to the packing of charged particles is electrophoretic deposition (EPD), which has been widely applied to the fabrication of wear resistant coatings as well as functional nanostructured films for electronic, biomedical and electrochemical applications.

In this work, the packings of charged micron-sized particles are investigated using discrete element simulations based on adhesive contact dynamic model. It is found that increasing the charge on particles causes a remarkable decrease of the packing fraction and the mean coordination number. The long-range Coulomb repulsion changes the packing structures by decelerating the impacting particles before they are bonded into the force networks. Once the contact networks are formed, the short-range adhesion will dominate over the repulsive Coulomb forces. A modified adhesion parameter  is proposed to successfully scale the packing results for charged micro-particles.

Publication: Chen S, Li SQ*, Liu SQ, Makse HA. Effect of long-range repulsive Coulomb interactions on packing structure of adhesive particles. Soft Matter, 12(6), 1836-1846 (2016).