Mechanisms of depinning accompanying evaporation of colloidal dispersion droplets

Resumo

Experiments have been performed to clarify the mechanism of depinning, i.e., the onset of the movement of the menisci of evaporating dispersion droplets under the conditions of the formation of ringshaped deposits (the coffee-ring effect). The influence of the nature and concentration of dispersed particles on depinning has been studied. It has been shown that there are three main effects responsible for depinning. The first effect is due to the hysteresis of droplet contact angle, the second one results from the influence of the particles on the surface tension of a dispersion, and the third effect is caused by the formation of a dense gel in the meniscus region. A relation has been revealed between the mechanisms being realized and scenarios of droplet evaporation.