Surface wettability regulation on the miniaturized V-shaped channels fabricated by hot-embossing

The combination of functional microstructure and surface wettability regulation is an advanced strategy to achieve greatly enhanced functions such as heat transfer, drag reduction and corrosion resistance, and has broad application prospects in aerospace, microelectronics, biomedical and other fields. This study proposes a cost-effective and environmental-friendly method to fabricate miniaturized V-shaped channels, and the surface wettability and droplet behavior of fabricated channels are investigated. Miniaturized V-shaped channels are fabricated by hot-embossing, and the wetting transitions to the Cassie state as the scale of the embossed channels increases. After subsequent modification with ultrafast laser and fluorine-free stearic acid, V-shaped channels with superhydrophilic and hydrophobic properties are obtained. Rough nanotextures are formed on channels after laser scanning, and the inherent anisotropic wetting could be alleviated by combining with stearic acid modification. The droplet spreading captured by the high-speed camera shows that the droplet can completely spread on the superhydrophilic channels fabricated by the ultrafast laser, and the larger the dimension of the channels, the stronger the spreading anisotropy and the smaller the spreading ratio. By contrast, the droplet on the hydrophobic channels spreads first and then shrinks, and the anisotropy of droplet spreading or shrinking decreases. Interestingly, the hydrophobic channel dimension is found to have a significant effect on the droplet behaviors. The droplet could full bouncing or form satellite droplet when it impacts the hydrophobic channels with smaller dimension, whereas the droplet on the larger channels tends to be pinned or breakup. The relationship between miniaturized channel dimension and droplet wetting should be appreciated in practical engineering applications, which will facilitate the development of novel functionally enhanced surfaces.