Predicting coffee ring formation upon drying in droplets of particle suspensions.

Pattern formation is a common occurrence in drying colloidal systems. The most common in droplets, is a ring distribution where the constituents have relocated to the edge, which is referred to as a coffee ring. This deposit is unfavourable in many manufacturing processes and is of fundamental interest. In this study, we present a model capable of predicting when a coffee ring will be observed in hard spherical particle systems. Ring profiles are found to be formed at low contact angles with the specific angle predicated upon the initial concentration of the suspension. Modelling results are in agreement with experiments using latex suspensions.