Fractal Growth of Crystalline Phospholipid Domains in Monomolecular Layers

Self-similar structures of single-crystalline domains in lipid monolayers at the air-water interface are observed after a stepwise increase of the surface pressure. It is shown that these fractal structures with Hausdorff dimensions of $d\ensuremath{\approx}1.5$ anneal because of the influence of edge tension on time scales of minutes. The results can be understood within the framework of diffusion-limited aggregation taking into account constitutional supercooling due to different miscibilities for impurities in solid and in fluid lipid phases.