Directional transport of droplets on wettability patterns at high temperature

• Published in: Applied surface science 2018-01, Vol.428, p.432-438
• Main Authors: Huang, Shuai, Yin, Shaohui, Chen, Fengjun, Luo, Hu, Tang, Qingchun, Song, Jinlong
• Format: Article
• Language: English
• Subjects: Directional transport; Electrochemical etching; Superhydrophobic surface
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2017.09.158

•The wettability pattern composed of the superhydrophobic (S-phobic) region and superhydrophilic (S-philic) region was fabricated by a simple twice-electrochemical-etching approach.•With the increase of substrate temperature, droplet on surface with wettability pattern will change from contact boiling to Leidenfrost state.•By designing a wettability pattern in which S-phobic region and S-philic region were alternately arranged, when the substrate temperature Ts is 250°C, a controlled directional transport of droplet can be achieved. Directional transport of liquid has attracted increasing interest owing to its potential of application in lab-on-a-chip, microfluidic devices and thermal management technologies. Although numerous strategies have been developed to achieve directional transport of liquid at low temperature, controlling the directional transport of liquid at high temperature remains to be a challenging issue. In this work, we reported a novel strategy in which different parts of droplet contacted with surface with different wettability patterns, resulting in a discrepant evaporative vapor film to achieve the directional transport of liquid. The experimental results showed that the state of the liquid on wettability patterned surface gradually changed from contact boiling to Leidenfrost state with the increase of substrate temperature Ts, and liquid on superhydrophilic surface was in composite state of contact boiling and Leidenfrost when Ts was higher than 200°C. Inspired by the different evaporation states of droplet on the wettability boundary, controlling preferential motion of droplets was observed at high temperature. By designing a surface with wettability pattern on which superhydrophobic region and superhydrophilic region are alternately arranged, a controlled directional transport of droplet can be achieved at high temperature.