Buckling of a drying colloidal drop.

Abstract

It is well known that drying drops of colloidal dispersions undergo complex morphological transitions involving buckling of a particle-packed outer shell during drying. Although capillary stresses generated during drying have been identified as the cause for buckling, the exact conditions for buckling and its relation to the particle size, rigidity, and nature of packing have not been understood. Here, we derive explicit expressions for the critical capillary pressure for buckling of droplets based on the mechanical properties of the particle network formed during drying and the conditions under which buckling can be avoided. We anticipate our results to form the basis for design of formulations for the pharmaceutical, food and ceramics industry.