Are there lock and key interactions for bulk nematic defects?

Nematic liquid crystals are fluids capable of maintaining ordered structures, making them ideal for reconfigurable metamaterials. A notable example is the elastic interaction between a colloid and a topographic substrate with well-defined anchoring conditions and matching curvature radius. Colloids are attracted to wells when the anchoring conditions match and to hills when they do not—reminiscent of the key-lock interaction in proteins. Here, we ask if lock and key can be extended to topological defects in nematics confined by homeotropic boundaries. Unlike colloids, nanoscopic defects can change structure or escape from confinement. We combine simulations and experiments to explore conditions that stabilize point defects near curved walls. Our experimental platform consists of homeotropic cells with pore topographies fabricated via photolithography. Wells stabilize several configurations with distinct topologies, with or without a bulk defect. Although defects are not required in this setup, they are stabilized by vertical sidewalls and sharp pore edges. We also design multilobe pores that offer multistable defect locations and test the relocation of defects using a DC electric field.