Thermal stability of micro-nano structures and superhydrophobicity of polytetrafluoroethylene films formed by hot embossing via a picosecond laser ablated template

We report here a simple and efficient hot embossing process capable of mass fabricating superhydrophobic and self-cleaning polytetrafluoroethylene (PTFE) film surfaces. Adding superhydrophobicity to hydrophobic polytetrafluoroethylene (PTFE) significantly enhances their application potential in industry as well as in daily life. We applied a picosecond laser to fabricate regular array of micro-holes companied with submicron structures on high strength steel substrate to form a lotus-leaf-like template. Then the hot embossing process was performed on flat PTFE films to introduce a dual-scale structure composed of the micro-scale protrusions and nano-scale fibril structures on the top of protrusions. The hot embossing parameters such as the embossing pressure and time were optimized to achieve required micro-and nano-scale dual structure on PTFE film very closed to the similar dual structure of the lotus leaf surface. The PTFE films then exhibited superhydrophobicity with contact angle up to 154.6 degrees. and sliding angle of as low as 5.5 degrees. The thermal stability of the superhydrophobic PTFE films was investigated from room temperature up to 430 degrees C. We demonstrate that the micro-nano dual structure on PTFE films and their superhydrophobicity is thermally stable up to 340 degrees C. The micro-scale protrusions will collapse and the superhydrophobicity will lose when the temperate is over 370 degrees C. (C) 2015 Elsevier B.V. All rights reserved.