Colloids with anisotropic interactions could assemble into much more diversified structures than isotropic particles. Here, we specifically investigate the impact of geometric anisotropy on colloidal dimers' assembly on conducting substrates under electric fields. By systematically tuning the size ratio between two lobes on dimers, we have found the interactions between dimers are strongly dependent on their relative orientations. For example, attractive interactions exist between lying and standing dimers on the substrate. When all dimers stand on the substrate, the interactions between neighboring dimers with alternating orientations are attractive. Otherwise, the interactions are repulsive. Such orientation-dependent interactions generate various new structures, such as chiral clusters and dimers crystals with alternating orientations. The physical origin of those orientation-dependent interactions and the impacts of experimental conditions such as the ionic concentrations and surface charges will be discussed. Our numerical model based on electrostatics agrees well with experimental results and provide further insights on electric-field assisted assembly of anisotropic particles.

Impact of geometric anisotropy on the assembly of colloidal dimers under electric fields

246th National Meeting (2013)

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