Force‐Based Wetting Characterization of Stochastic Superhydrophobic Coatings at Nanonewton Sensitivity. Issue 42 (1st September 2021)

• Record Type: Journal Article
• Authors: Hokkanen, Matti J.; Backholm, Matilda; Vuckovac, Maja; Zhou, Quan; Ras, Robin H. A.
• Is Part Of: Advanced materials. Volume 33:Issue 42(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-01
• Subjects: contact angle -- droplet adhesion -- superhydrophobicity -- wetting; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adma.202105130
• Languages: English
• ISSNs: 0935-9648

Abstract

Abstract: Superhydrophobic coatings have extraordinary properties like self‐cleaning and staying dry, and have recently appeared on industrial and consumer markets. The stochastic nature of the coating components and coating processes (e.g., spraying, painting) affects the uniformity of the water repellency across the coated substrate. The wetting properties of those coatings are typically quantified on macroscale using contact angle goniometry (CAG). Here, highly sensitive force‐based methods, scanning droplet adhesion microscopy (SDAM), and micropipette force sensor (MFS), are used, to quantify the microscale heterogeneity in the wetting properties of stochastic superhydrophobic coatings with irregular surface topography that cannot be investigated by CAG. By mapping the wetting adhesion forces with SDAM and friction forces with MFS, it is demonstrated that even the best coatings on the market are prone to heterogeneities that induce stick–slip motion of droplets. Thus, owing to their high spatial and force resolution, the advantages of these techniques over CAG are demonstrated. Abstract : Scanning droplet adhesion microscopy and micropipette‐based droplet friction measurements are used for quantitative evaluation of the wetting properties of stochastic superhydrophobic coatings. These novel force‐based characterization techniques provide a detailed picture of the wetting performance and heterogeneity of super‐repellent surfaces, far beyond what is afforded by traditional contact angle measurements.