Evaluating the resilience of superhydrophobic materials using the slip-length concept

Abstract

The drive to introduce superhydrophobic materials into real-world applications requires the development of robust and effective surfaces. Efforts to formulate a collective understanding of the design approaches required to engineer resilience are hindered significantly by inconsistencies in the evaluation methods used throughout the literature. Herein, we report a technique that accurately quantifies both the superhydrophobicity, and superhydrophobic resilience under fluid shear stress, using slip-length measurements. Two types of superhydrophobic surface are used (micro-rough PTFE, and nano/micro-rough nanoparticle coatings), in order to demonstrate the different mechanisms of superhydrophobic degradation, in addition to the versatility of the slip-length technique to study the phenomena. The shear stress testing is symptomatic of real-world conditions (applied fluid stress), an environment where superhydrophobic materials are relatively vulnerable due to their comparative fragility. The technique is both a comprehensive, sensitive and quantitatively reproducible, assessment method of superhydrophobic interfaces, which if widely adopted, would accelerate progress in this area.