Crack patterns in drying protein solution drops

A deposited drop of bovine serum albumin salt solution experiences both gel ation and fracturation during evaporation. The cracks appearing at the edge of the gelling drop are regularly spaced, due to the competition between t he evaporation-induced and relaxation-induced stress evolution. Subsequentl y, the mean crack spacing evolves in an unexpected way, being inversely pro portional instead of proportional to the deposit thickness. This evolution has been ascribed to the change with time of the average shrinkage stress, the crack patterning being purely elastic instead of evaporation-controlled .