Dislocation and grain boundary motion in buckled colloidal monolayers

Dislocation and grain boundary motions critically impact properties of crystalline materials, and have been studied in colloidal monolayers where particle-scale mechanisms are directly observable. We study a buckled colloidal monolayer in which spherical particles confined between two flat surfaces spaced by ~1.5 particle diameters buckle up or down to act as "spins". Particles self organize into maze-like stripes of alternating spins to minimize free volume. Compared to a planar colloidal crystal, grain boundary motion in these spin domains is not well understood. Our preliminary results indicate that dislocation motion is affected by the local spin domain configuration, suggesting that grain boundary motion may be restricted in certain directions depending on the orientation of the surrounding spin stripes. We use optical tweezers to create grain boundaries and dislocations in the buckled crystal and compare their subsequent relaxation to that observed in planar crystals.