Interaction of liquids with nanostrucured surfaces

Abstract

The study and characterization of wetting properties is a crucial first step in achieving a fundamental understanding and specific development of superhydrophobic and superamphiphobic surfaces. In this context, static and dynamic contact angle measurements are the main techniques widely used to characterize wetting behavior of surfaces. However, these macroscopic techniques leave a lack of knowledge of what is happening at the surface itself at the submicroscopic level. Here, repellent surfaces (superhydrophobic and superamphiphobic) have been prepared and their adhesion force with micron-sized droplets have been measured using Atomic Force Microscopy (AFM). In this way, AFM has allowed us to measure forces of nN of resolution, thereby making it possible to determine the adherence of micro-sized drops with the surface. We achieved this by attaching a liquid drop to the end of a tip-less cantilever (droplet probe) and performed force spectroscopy. For this we have used ionic liquids and water-glycerol mixtures to obtain droplets with microscopic radius and little loss of mass due to evaporation. Moreover, Confocal microscopy has been combined with AFM to visualize the droplet behaviour during the force measurement, this powerful tool allows us to observe the drop deformation, the contact angle and the pinning area of the drop. Also, we can determine if there is some remnant of the droplet left on the surface, due to the quality of the repellent surface