Nanoparticle-induced morphology and hydrophilicity of structured surfaces.

Nanoparticles have been applied into the construction of micro- and nanoscaled surface structures with extreme wettability over the past few years. However, the details of processing and employing colloidal nanosuspensions for this purpose have not yet been fully investigated. In this work, we study the surface structures formed via nanosuspensions, in which nanoparticles of solid phase are presented, and the caused surface wettability. We disperse silica nanoparticles with different sizes into pure ethanol to prepare nanosuspensions with a series of concentrations. The suspensions are ultrasonically processed to prompt uniform distribution of nanoparticles before application. The deposited nanosuspensions are thermally treated to assist the regulation of surface patterns based on nanoparticles. Hence, the investigation explores a variety of experimental conditions that will lead to distinctive surface structures and wettabilities. Accordingly, the wettability of the induced surfaces is investigated using contact angle measurement, and the structures of those surfaces are mainly revealed by atomic force microscopy (AFM). Superhydrophilicity is observed on many of such formed surfaces, and the pattern of surface structures in micro- and nanoscale is closely related to the processing conditions and the size of nanoparticles. Thus, we report the characteristics of the surface patterns based on nanoparticles and the formed wettability.