Dynamic evaporating evolution of profiles for micro droplets on flat surfaces with hydrophilic and hydrophobic treatments

We report the experimental and analysis results of evaporation rates for micro droplets deposited onto flat surfaces that exhibit various hydrophobic and hydrophilic properties. These droplets are pure water regularly used as solvents of evaporative liquid solutions, in which different solid solutes can form versatile microstructures for patterning after dried. Evaporation tests have demonstrated that these micro droplets show significantly different evolution of profiles over time when the surface hydrophobicity varies. Cross-sectional profiles are acquired by a high-performance digital camera that enables all the dimensional changes of the geometries such as heights and radii to be recorded and analyzed during complete evaporation. The pinning/de-pinning effects of those droplets on the evaporation rates have been particularly highlighted and compared by those observations of geometries.