Deck the walls by tunable energy fields for colloidal particles (Data)

The ability to dictate colloid motion is an important challenge in fields ranging from materials science to living systems. Here, by embedding energy landscapes in conned nematic liquid crystals, we design a versatile platform to dene colloidal migration. This is achieved by placing a wavy wall with alternating hills and wells in a nematic liquid crystal to impose a smooth elastic energy field with alternating splay and bend distortions. This domain generates (meta) stable loci that act as attractors and unstable loci that repel colloids over distances large compared to the colloid radius. Energy gradients in the vicinity of these loci are exploited to dictate colloid trajectories. We demonstrate several aspects of this control, by studying transitions between defect configurations, propelling particles along well defined paths and exploiting multistable systems to send particles to particular sites within the domain. Finally, we demonstrate the ability of a colloid in motion, like \Goldilocks", to select from wells of different sizes for preferred docking. Such tailored landscapes have promise in reconfigurable systems and in microrobotics applications.