Water droplets bouncing on superhydrophobic soft porous materials†
Creating superhydrophobic soft porous materials, such as cotton and cloths is an important area of research as these materials have important practical applications such as water repellent clothing. In this paper, a generic method is reported to fabricate superhydrophobic surfaces on soft porous substrates, which were treated with crystalline copper chloride-hydroxide, followed by a fluorinated polymer. Water droplets can be supported as a perfect sphere and even bounce on the prepared surfaces, which demonstrate superior superhydrophobicity. For many soft porous materials, it is difficult to identify superhydrophobicity using water droplet contact angles. This is because water droplets may be trapped in the concave structures, making the necessary contact line to define the contact angle unobtainable. To solve this problem, water bouncing was used as a sufficient and necessary identification for superhydrophobic soft porous materials, and a model was also made to discuss how a water droplet can bounce on soft materials.