(64d) Assembly of Particles Under Orthogonally Applied Electric and Magnetic Fields

Colloids can be used either as model systems for directed assembly or as the necessary building blocks for making functional materials. Previous work primarily focused on assembling colloids under a single external field, where controlling particle-particle interaction is limited. This talk will present results under a combination of electric and magnetic fields. When these two fields are orthogonally applied, we can independently tune the magnitude and direction of the dipolar attraction and repulsion between the particles. As a result, we can obtain well-aligned, highly dense, but individually separated linear chains at intermediate particle concentrations for isotropic microspheres, or chiral colloidal clusters with tunable handedness when the building blocks are anisotropic colloidal dimers. We will report our experimental observations, underlying mechanisms, and tunability of the assembled structures. In addition, we have also performed Monte Carlo and Brownian Dynamics simulations in which the electric and magnetic dipolar interactions and electrohydrodynamic interactions are involved to gain a more fundamental understanding of our experimental results. Our method provides a convenient route for producing complex and hierarchical structures that are challenging to make using one field only.