Observation of Spatially Rhythmic Patterns from Evaporating Collagen Solution Droplets

Spatially rhythmic (i.e., concentric ring and symmetric radial band) patterns appeared from droplets of collagen solutions during evaporation. A morphology diagram representing the pattern generation and bifurcation versus collagen concentration and evaporation time was determined. The pattern structures were examined using an atomic force microscope and polarizing optical microscope. The characteristic width of the radial bands (40−200 μm) showed stepwise increases toward the pattern center because of a systematic generation of fusing and dislocation. The spatiotemporal evolution of the patterns involved an oscillatory motion toward the droplet center (for the ring patterns) and a periodic segmentation along the droplet edge (for the radial patterns), suggesting the onset of distinct interfacial instabilities coupled with evaporation.