The ability to dictate the trajectories and docking sites of microscopic objects has far-reaching implications in fields ranging from reconfigurable materials to intelligent systems.  Diverse approaches have been developed, ranging from the use of external fields or of active colloids near structured boundaries. Here, we exploit confined nematic liquid crystals (NLCs) near undulating boundaries to embed energy landscapes. Related concepts have been widely explored for NLCs that create defects that trap colloids. Here, we take a different approach, and design a director field that, in the absence of the colloids, is defect-free. This field gently guides colloid motion, avoiding trapped metastable states. Since the field is related to NLC orientation, the interactions are reconfigurable, either by reorientation of the NLC under applied fields, or by reconfiguration of the boundary shape. We show that a simple boundary of alternating hills and wells embeds energetic cues that dictate particle paths and multi-stable equilibrium loci. Furthermore, we demonstrate remarkable control over the defect structure associated with the colloid, a significant outcome, since such defects attract surfactants and nanoparticles. This means of directing colloid motion is readily combined with other fields to afford additional control with promise in reconfigurable systems and in microrobotics applications.<br/>

Directing colloid motion in nematic liquid crystals near wavy boundaries

256th National Meeting (2018)

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