Anisotropic self-assembly of polarizable colloidal mixtures

Particles with directional interactions represent promising building blocks for new functional materials and are often realized by particles with anisotropic shape or with patchy directional bonds. Here we demonstrate that binary suspensions of oppositely charged size-asymmetric colloids robustly self-assemble into a variety of anisotropic superstructures, resulting from the many-body dielectric effects which impart effective directionality to the inter-particle interactions. Via simulations, we illustrate how both local coordination number (connectivity) and fractal dimension can be well controlled through variation of the size ratio and the mismatch in relative permittivity. The mechanism we have identified offers a potential avenue to designing materials with controllable structural properties.