Colloidal dynamics in the presence of oscillatory electrophoretic forces

Abstract

The understanding of self-assembly and self-organization processes of colloidal particles are topics that in recently years have received greater attention in physics, in materials science, and in biology. Colloidal systems are often used as "big atoms" to study the fundamental physics of formation of crystals. In this thesis, electric fields at varying frequencies and amplitudes were applied to a charged colloidal system. Variation of the electric field amplitude will change the strength of the self-assembly and self-organization processes. At high frequencies and field strengths, the colloids experience a dipolar inter-particle interaction that will affect the equilibrium structure. At low frequencies, however, the colloids will experience both dipolar and non-equilibrium time-dependent electrophoretic forces. The main purpose of this work was to explore this interplay between dipolar interactions and electrophoretic forces, and study how self-assembly and dynamics is affected by this interplay. From this study, we found a dynamical phase diagram that demonstrates the relationship between structure formation and particle dynamics as the frequency and field strength changes.