Wenshuai Xu,Yu Liu,Boya Xiao,Heng Jiang,Meng Chen,Yuren Wang
Controllable wetting transition on artificial microtextured surfaces has significant applications in many industrial fields. In this work, the droplet spreading and the directional wetting transition are investigated on the substrate surface with the patterned microcavities. The results show that the macroscopic inward wetting transition from the periphery to the center of the droplet strongly depends on the mesoscopic sequential transition from Cassie to Wenzel state in the microcavities on the substrate surfaces. The semiquantitative relationship between sagging depth of meniscus in the microcavities and the droplet spreading velocity is set up by utilizing scaling-law analysis in terms of mechanical equilibrium of the meniscus. This finding is expected to help to clarify the issues on the mechanism and main affecting factors of the wetting transition on the patterned surface.
We report evaporation of ethanol/water mixture droplets on both pillar-arrayed and micro-holed polydimethylsiloxane (PDMS) surfaces. Analysis of wettability shows that (i) when the pillar-to-pillar spacing is 5 μm, the pillar-arrayed PDMS surfaces are Cassie-Baxter-wetted; (ii) when the pillar-to-pillar spacing is 20 or 50 μm, part of each pillar-arrayed surface is Cassie-Baxter-wetted while the other part Wenzel-wetted; (iii) all micro-holed PDMS surfaces are Cassie-Baxter-wetted; (iv) the advancing and receding contact angles increase with the increase of the pillar-to-pillar spacing, while they decrease with the increase of the hole-to-hole spacing. The investigation on evaporation of mixture droplets demonstrates that (i) evaporation on pillar-arrayed PDMS first proceeds with constant contact radius mode (CCR) due to the strong adhesion between the surface and the droplet; (ii) on micro-holed surfaces CCR stage is also observed for the surface with the hole-to-hole spacing of 5 μm, while it is not found at high ethanol concentration for surfaces with the hole-to-hole spacings of 20 μm and 50 μm, which is attributed to the weak adhesion between the micro-holed surfaces and the droplet. Finally, the evolution of droplet volume and its two-third power are discussed.
Hong An,Yongfeng Qian,Xinzhe Xu,Haolin Guo,Bo Wang,Zhiyu Zhang,Minqiang Jiang,Hu Huang,Jiwang Yan
The wetting state is a fundamental property of a material surface, yet achieving precise control over this property remains a formidable challenge. Mastery of wetting behavior can impart tailored functionalities to surfaces, such as liquid repellency, anti-fouling, and directional liquid transport. Despite the potential benefits, strategies for rapid and reliable modulation of various wetting states have remained elusive until now. In this study, an innovative one-step laser-based strategy that enables precise and rapid manipulation of surface wetting states on carbon fiber reinforced plastic (CFRP) is presented. This approach allows for the creation of hydrophilic surfaces characterized by the Wenzel state, hydrophobic surfaces with a mixed Cassie-Baxter/Wenzel state, and robust superhydrophobic surfaces featuring a stable Cassie-Baxter state. The realization of a stable Cassie-Baxter state stems from the concurrent formation of hierarchical micro/nanostructures and the enrichment of low surface energy components. Critically, the resulting superhydrophobic CFRP surfaces with the Cassie-Baxter state exhibit exceptional stability, minimized adhesion, and superior anti-icing and de-icing properties. These findings provide both fundamental insights and a practical platform for the rapid development of non-wetting, multifunctional surfaces, significantly expanding the applicability of CFRP across diverse engineering domains.
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