Numerical investigation of colloid-transport in nonpolar solvents for electronic paper displays

Electrophoresis (EP) is the movement of charged particles relative to a stationary liquid, induced by an applied electric field. Electroosmosis (EO), on the other hand, is the movement of a liquid relative to a stationary charged surface caused by an external electric field. In nonpolar systems, charges are generated in the form of charged inverse micelles (CIMs). The addition of surfactants helps disperse particles in nonpolar systems and makes it possible for Electrophoresis (EP) and Electroosmosis (EO) to take place. A detailed 2D model is proposed to numerically study the combination of EP and EO in nonpolar solvents, in which the Navier-Stokes equation, Nernst-Planck equation, and Poisson equation are coupled together to solve the fluid and particle motion, and the electroosmotic boundary condition is utilized to investigate the influence of the zeta potential. The comparable results between experiments and simulations imply that the particle motion is dominated by both EP and EO. Based on the gained insight, the idea of increasing the zeta potential of the substrate is proposed, which we show can significantly improve the speed at which colloidal particles migrate across the fluid cell. This work may benefit the fundamental understanding of EP and EO in nonpolar systems and help develop improved, fast-switching electrokinetic displays.