A suspension-based micro-etching technique to create gradient wettable phosphor bronze surfaces for droplet transport

Precise regulation of surface wettability is critical for achieving efficient droplet transport. However, traditional surface preparation methods often suffer from process complexity, high costs, and difficulties associated with large-scale production. In this paper, we propose a suspension-based micro-etching technique for phosphor bronze surfaces, enabling the precise tailoring of droplet transport. First, micro- and nanoscale structures with gradient wettability were constructed on the surface, and then, the adhesion force of droplets was precisely controlled. An in-depth analysis based on a range of characterization methods, including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM), indicated that the superhydrophobic surfaces constructed using the proposed suspension micro-etching technique exhibited more homogeneous microstructures, allowing also for the better control of the surface characteristics, and confirming the extraordinary potential of the proposed technique. Furthermore, the anti-icing and bouncing performance, as well as the self-cleaning ability of the created gradient-based surface, were investigated. The observed performance was consistent with the surface wettability. Overall, we present a cost-efficient, straightforward, and innovative approach to the fabrication of gradient wettability surfaces, which not only expands the palette of preparation techniques but also establishes a foundation for advancing the related fields.