Controllable Water Adhesion and Anisotropic Sliding on Patterned Superhydrophobic Surface for Droplet Manipulation

Abstract

Superhydrophobic surfaces with hydrophilic patterns have wide applications in biomedical and chemical analysis domains. In this work, a rapid, simple and top-down micro-milling method was proposed for fabricating hydrophilic patterns such as micro dots, line and circle grooves on superhydrophobic surfaces. This method could be extended to construct various linear patterns on diverse substrates on account of its mechanical material-removal mechanism. Hydrophilic micro dots, line and circle grooves were milled on the superhydrophobic Al alloy surface. The milled micro dots demonstrate great adhesion towards water droplets without changing the contact angles whereas the pre-wetted line grooves exhibit strong anisotropic water adhesion, that is, the resistance force that restricts the droplet from detaching in directions parallel and perpendicular to the grooves is significantly different due to the different stress state of the droplet on the grooves. The adhesion force perpendicular to the groove, together with the sliding resistance that is generated by the milled dot, was investigated through experiments. The results show that the relationship between the adhesion force and the droplet-pattern interfacial widths could be well described using the classical Furmidge equation. This research could possibly be employed in such biomedical and chemical analysis domains as water harvesting, droplet storage and droplet transport.

Bioinspired Special Wettability Surfaces: From Fundamental Research to Water Harvesting Applications

“…Additionally, Yang et al adopted a rapid, facile and top‐down method consisting of electrochemical processing, modification, and micromilling to fabricate diverse patterns such as microdots, lines, and circle grooves as shown in Figure . They used this method to construct diverse hydrophilic patterns on the superhydrophobic Al alloy surface.…”

“…E) Parallel and perpendicular SAs of various volume droplets on groove patterns with different widths. Reproduced with permission . Copyright 2016, American Chemical Society.…”

Femtosecond Laser Fabricated Elastomeric Superhydrophobic Surface with Stretching-Enhanced Water Repellency

“…The wetting modes of diverse artificial water-repellent surfaces are based on the surface morphology inspired by biomineral materials [26]. Low adhesion (LA) superhydrophobic surfaces mimicking lotus leaves are endowed with low sliding angles below 10° [27], and high adhesion (HA) superhydrophobic surfaces derived from rose petals [28] have distinct characteristics that water drops cannot slide from the surface at any titled angle. In this paper, the two kinds of surface morphology were both fabricated by laser texturing the elastomer with different processing parameters [29].…”

Fabrication of biomimetic multi-scale surface of rice leaf and anisotropic superhydrophobic properties

“…Yang等人 [20,21] 在铝合金表面上采用光刻辅助电化学 刻蚀、 阳极氧化反应和氟化反应制备类水稻叶三级微 观结构表面, 发现对于不同的液滴体积所对应的各 向异性不同; 还利用自上而下的微铣削方法制备了 微点、线和圆凹槽超疏水表面模型, 不同的模型具有 不同的黏附性和各向异性, 可以应用在生物医学和 化学分析领域, 例如液体集聚和存储. 姚佳等人 [22] 采用二次转写的方法制备出仿生水稻叶表面, 此技 With the continuous exploration of the special morphologies and properties of skin of some animals and plant leaf surfaces in the nature, new hydrophobic surfaces are developed through imitation of the observed surface effects.…”