Membrane tension and bending alter the morphology of solid domains on curved membranes

Compared with crystal growth in a planar geometry, crystal growth on surfaces having non-zero Gaussian curvature is poorly understood, where calculations reveal the possibility that curvature-induced stress may lead to anisotropic crystal growth. However, there are very few experimental examples available so far. In this study, we demonstrate that the crystal formation resulting from the solidification of lipid membrane domains in giant unilamellar vesicles is altered by the membrane tension that pulls on the edge of a growing crystal, creating new morphologies. The scaling of this behavior with curvature acts in opposition to the curvature-induced stress effect seen for colloidal deposition on a curved template. During nucleation and growth, experimental parameters, such as cooling rate and water transport, affect the tension history of individual vesicles. The outcome is that flat compact domains are repeatedly found on small vesicles whereas flower shaped domains grow as the vesicle diameter increases. Quantitative micropipette experiments as well as theoretical modeling suggests that the emergence of flowers is due to higher membrane tension on larger vesicles and the interplay between bending energies and line tension.