Mapping micron-scale wetting properties of superhydrophobic surfaces

TL;DR

This paper introduces a high-resolution method using an AFM cantilever with micrometric droplets to directly map and analyze the micron-scale wetting properties and dynamic behaviors of superhydrophobic surfaces.

Contribution

It presents a novel approach for spatially resolving wetting properties at micron scale, surpassing traditional contact angle measurements in quantitative detail.

Findings

Direct measurement of adhesion and friction forces at nanonewton resolution.

Observation of time-resolved pinning-depinning dynamics.

Spatial mapping of wetting heterogeneity on superhydrophobic surfaces.

Abstract

There is a huge interest in developing super-repellent surfaces for anti-fouling and heat transfer applications. To characterize the wetting properties of such surfaces, the most common approach is to place a millimetric-sized droplet and measure its contact angles. The adhesion and friction forces can then be indirectly inferred from the Furmidge's relation. While easy to implement, contact angle measurements are semi-quantitative and cannot resolve wetting variations on a surface. Here, we attach a micrometric-sized droplet to an Atomic Force Microscope cantilever to directly measure adhesion and friction forces with nanonewton force resolutions. We spatially map the micron-scale wetting properties of superhydrophobic surfaces and observe the time-resolved pinning-depinning dynamics as a droplet detaches from or moves across the surface.