Curvature Instability of Chiral Colloidal Membranes on Crystallization

Crystallization is a well understood disorder-order phase transition in bulk three-dimensions. Faceted and flat single crystals appear during seeded growth from a melt. However, crystal morphology changes dramatically when the same transition is confined to two-dimensions. We show the existence of a curvature instability that arises during the crystallization of finite-sized monolayer membranes of chiral colloidal rods. While the bulk of the membrane crystallizes, its edge remains fluid like and exhibits chiral ordering. The resulting internal stresses cause the flat membrane to buckle macroscopically and wrinkle locally. Our results demonstrate an alternate pathway based on intrinsic stresses instead of the usual external ones to assemble non-Euclidean sheets at the colloidal length scale.