Self-pinning colloids on rough surface

Abstract

Self-pinning colloids are integral to multiple applications from ink-jet printing to diagnostic platforms. The commercial surfaces involved in these applications are inherently rough and to mimic the same, we probe the self-pinning mechanistic using a model system of colloidal (sessile) droplet desiccating over a homogeneously rough surface having root-mean-square roughness, Sqnm∼0.36nm;(0<Sq<1). Further, the interplay of the particle diameter dnm∼460;30)with the substrate roughness induced length-scale on the evaporation modes of these desiccating colloidal droplets has been investigated with extensive experiments. The second parametric variation outlined the effect of varied particle concentration (ϕ,ww%∼0.05,0.1,1) on the pinning-de-pinning transition of the contact line during evaporation. These are characterised and quantified by contact angle goniometry and a general map of evaporation modes is proposed for such evaporating colloidal droplets induced by self-pinning of the dispersed colloids.