Superhydrophobic interface materials, especially for the applications in the microfluidic systems and lab on a chip, have attracted many researchers’ attention in chemistry, biology and material science. But most of the developments focused on the research of the relation between the charter of surfaces and the wettablity in normal environment. There are few reports on the research of temperature/pressure-dependant Cassie state on textured surfaces. However, the droplet control, especially for the self-propelled Leidenfrost droplet, is a big challenge in applied and fundamental fields.

The research group led by Professor Xuedong WU at the Ningbo Institute of Materials technology and Engineering (NIMTE), the Chinese Academy of Sciences (CAS), has been engaged in dealing with the issues of external stimulus induced Cassie state on micro/nano-textured surfaces since 2009. Their recent investigation revealed that ratchet composite thin film with designed surface wettability and parameters of the substrate with micro/nano-textures were found to be effective in adjusting the Leidenfrost point (LFP) of self-propelled droplets and obtaining low-temperature self-propelled droplets.

It was also found that, the more hydrophobic surface might have a higher LFP than the less one. The sawtooth width should be smaller than the droplet radius to keep the direction effect strong. The self-propelled LFP droplets were initiated on the ratchet composite hydrogenated carbon surface at a temperature lower than before, which is suitable for many practical applications.

These composite thin films and the preparation technology can be expanded to the microintelligent thermal management system and microfluidic systems. The novel self-propelled interfacial material and preparation technology can be used to the manufacture process and constructed a temperature-dependent tubule for microfluidic systems.

The related research has been published by Journal of Colloids and Interface Science, 2012; 14: 2631-2636 and Chinese Science Bulletin, 2011, 56, 1930-1934, respectively.

Images by NIMTE
Prof. Xuedong Wu xdwu@nimte.ac.cn