Numerical Simulations of Colloidal Dimer Assembly into Chiral Clusters and Crystals under Combined Electric and Magnetic Fields.

The directed assembly of colloidal particles into ordered structures is crucial for developing advanced functional materials. In this study, we perform Brownian dynamics simulations to investigate the active assembly of self-propelling dimers under orthogonally applied electric and magnetic fields. We systematically explore the effects of dimer geometry, electrohydrodynamic interactions, and field strengths on the formation of chiral clusters and their hierarchical assemblies. By tuning these parameters, we can achieve precise control over cluster size and chirality, providing a method for assembling monodisperse chiral clusters with defined handedness. Furthermore, we utilize the assembled clusters to construct hierarchical structures and chiral colloidal crystals, where global chirality emerges from local packing arrangements, even when individual clusters are achiral. This ability to dynamically manipulate chiral structures using external fields presents a promising route toward designing programmable colloidal architectures, with potential applications in optical metamaterials, microrobotics, and reconfigurable soft matter systems.