Crack patterns in drying protein solution drops

TL;DR

This paper investigates crack pattern formation in drying protein solution drops, revealing that crack spacing is governed by elastic stress evolution rather than evaporation rate, with unexpected inverse proportionality to deposit thickness.

Contribution

It uncovers the elastic nature of crack patterning and the inverse relationship between crack spacing and deposit thickness during drying.

Findings

Crack spacing is due to stress competition during gelation.

Crack patterning is elastic, not evaporation-controlled.

Inverse proportionality of crack spacing to deposit thickness.

Abstract

A deposited drop of bovine serum albumin salt solution experiences both gelation and fracturation during evaporation. The cracks appearing at the edge of the gelling drop are regularly spaced, due to the competition between the evaporation-induced and relaxation-induced stress evolution. Subsequently, the mean crack spacing evolves in an unexpected way, being inversely proportional 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.