Numerical simulations of electric-field-driven assembly of binary colloids into colloidal molecules and crystals.

Colloidal molecules (CMs)-clusters of colloidal particles with directional interactions-offer a versatile platform for the programmable assembly of complex soft materials. While both static and dynamic CMs have been synthesized to mimic molecular geometries, assembling them from simple colloidal building blocks via controllable interactions remains a challenge. Here, we employ Brownian dynamics simulations with experimentally realizable interaction models to investigate the electric-field-directed assembly of binary colloidal mixtures. By modulating electrohydrodynamic attraction and dipolar repulsion between particles and leveraging particle size ratios, we demonstrate the formation of two-dimensional and pseudo-two-dimensional CMs with various valences and geometric shapes. This valence-assisted strategy further supports the bottom-up construction of open colloidal lattices, including square and honeycomb arrangements. It also enables the simultaneous stabilization of both square packing and triangular packing at high particle concentrations. Our findings present a reversible and tunable approach to designing colloidal architectures with programmable interactions, offering new opportunities for the development of photonic materials, reconfigurable metamaterials, and functional soft-matter systems.