Highly Robust and Durable Superhydrophobic Coating through Soft Thermo-molding of Perfluorinated Thermoplastics for Self-cleaning and Anti-icing Li Wanbo 15485188 Supervisor: Prof. Ren Kangning Co-supervisor: Prof. Ong Beng

Superhydrophobicity (SH) – Bioinspired b. Salvinia SH leaves with hydrophilic pins collect air underwater a. Peanut SH leaves self-cleaning c. Lupin SH leaves with superhydrophilic channels collect water in very dry and hot media d. Butterfly structural color of wings warn predators f. Candida Superoleophobic surface structures anti-wetting e. Water strider slip on water g. Gecko walk on vertical surfaces Superhydrophobicity is a natural ability that is found on the skins of many live beings, such as lotus leaf and water strider h. Cicada anti-bacterial and self-cleaning wings Also, moth/mosquito anti-reflective and anti-fogging eyes J Mater Chem A Mater energy Sustain, 2014, 2, 16319.

potential applications and impact of SH 5 ℃ -10 ℃ Superhydrophobic coating are drawing much attention recent years in many areas such as…… Textiles Anti-corrosion Floating properties Optical devices Anti-fouling Anti-icing Anti-bacteria Oil–water separation

Current methods for preparing SHS and their limitations Applied Surface Science 257 (2010) 1540 Applied Physics A, 2015, 119(1): 75 Etching or anodizing substrate Al Cu Journal of Adhesion Science and Technology 23 (2009) 1215–1237 Science, 2015, 347(6226): 1132-1135. Crystallizing or embedding nanoparticles Energy/reagent-demanding; unstable and not hydrophobic enough Fragile structures could not stand mechanical/chemical/ thermal disturbance Expensive and unsuitable for large-scale application Loss of liquid layer Oil or water Lubricant film Nature, 2011, 477(7365): 443 ACS applied materials & interfaces, 2013, 5(10): 4026

Feasible to process, low cost, widely used in our life Plastic—materials play an essential role in social evolution and civilization in modern times In the present work, we turn to polymers to generate superhydrophobic coating, because they are feasible to process and low cost. Feasible to process, low cost, widely used in our life

Hypothesis The fluorine of Teflon prefer their own kind, drawing to each other, while repelling other kind of molecules, i.e. water. Teflon Material Extremely low surface energy Self-lubricating, Extremely inert, Stable from -200 to 250 °C, Anti-sticking. Performance of coating? Repellent to liquid Anti-abrasion, Chemically robust Thermally stable Anti-fouling In our work, we use Teflon materials to fabricate SH coating. Perfluorinated polymer often refer to Teflon. The carbon-fluorine bonds in Teflon are very strong, and pack closely to protect the carbon atoms from other molecules to enable substitution reaction.

Fabrication of SH Teflon surface. The two steps involved in the method are both cycled to generate soft intermediate master and the daughter replica. A continuous piece of engineered Teflon surface not only provides solid surface structures, but also protects the bonding layer from external invasion.

water droplets bouncing on bended Teflon SHS

Bonding Teflon with substrates. we did water contact angle measurements after the Teflon coating was peeled off forcibly oth glasses and fabrics bonded by Teflon could not be separated, instead, they were broken along the side of the bonding area; also there were Teflon residuals on the side of the bonded area on the aluminum plate. Displacement

Fabrication of Teflon SH coating on desired substrate.

3.4. Mechanical robustness. 100 thousand times along both its front and back sides 1500 g on a 1-cm2 area, = 3×ground pressure of a adult. Abrasion under weight (100-500 g) for 150 times

Chemical stability Outdoor environments: rainy for 4 days and sunny for 3 days; temperature ranged from 30 to 35 ℃ Strong chemicals

Anti-fouling ability Micro particles nanoparticles

Icing problems Transportation Energy Industry Daily life Communication Power lines Industry Daily life Superhydrophobic Surface coatings have wide arrange of applications in many areas

Mechanism of Anti-icing using SH coating Timely removal of impacting water droplet; Delay ice formation, Weaken the adhesion strength between the ice and the substrate. Superhydrophobic coating could be an effective solution to icing problem. Despite these efforts, the nucleation of ice on superhydrophobic surface is still unknow.

Anti-icing setup Three modulus: dehumidification, supercooling, and icing.

De-frosting by impacted super-cooled water droplets

Conclusion Developed robust SH coatings composed of a continuous piece of micro/nano structure made from Teflon by soft thermo-molding; Robust against severe thermal, mechanical, chemical, and photo-radiation invasions, Provides reliable bonding strength between various substrates, e.g. fabric, glass, and metal. the SH coatings are promising for anti-icing even in humid environment.

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