Enhanced Coffee-Ring Effect via Substrate Roughness in Evaporation of Colloidal Droplets

Figure 1

Surface roughness and contact angle of PTFE droplets on glass substrates. (a)–(d) Substrates with different roughness, polished using sandpaper with different mesh sizes. Larger sandpaper grain size increased the surface roughness. (e)–(h) Contact angle of the PTFE suspension on the substrate. The contact angle decreased as the substrate become rougher.