Delamination of drying nanoparticle suspensions

Abstract

Colloidal dispersions dried in thin capillaries exhibit a fascinating array of cracks. Here, we present experiments where the cracks are preceded by delamination in which the particle packed region debonds from the walls of the capillary before cracking. Experiments over a varying range of evaporation rates and with two differently sized capillaries show that there exists an upper critical capillary pressure at which the delamination occurs spontaneously and a lower critical pressure at which the propagating delamination front is arrested. Measurements reveal sub-micron deflection of the capillary walls during drying. We model the delamination process as a competition between the elastic energy stored in the stressed particle network and the deformed walls of the capillary, and the surface energy increase when the delamination front advances. The predicted deformation of the capillary walls and the critical capillary pressure for delamination are in fair agreement with the observations.