TiO₂-based slippery liquid-infused porous surfaces with excellent ice-phobic performance

Ice formation and accretion on surfaces of instruments such as infrastructures, power lines and aircrafts can trigger serious social danger, economic loss and threaten the safety of lives. It is of practical significance to develop functionalized passive anti-icing surfaces. Herein, we synthesized titanium dioxide nanotube arrays on titanium substrate through anodic oxidation method. The TiO₂ nanotube arrays were further modified and infused with perfluoropolyether (PFPE) lubricant to form slippery liquid-infused porous surfaces (SLIPS). The relationship of the nanostructures and the slippery performance, the liquid holding property and anti-icing property of TiO₂ based SLIPS was investigated in details. The contact angle hysteresis (CAH) and sliding angles of water droplets on the TiO₂ SLIPS are as low as 1° and 4°, respectively, indicating the excellent slippery property of the SLIPS. The CAH of water droplets on TiO₂ SLIPS could be still as low as 5° after being treated with 100 mL of flowing water, which show the long term stability and superior liquid holding property of the TiO₂ SLIPS. We propose that the excellent slippery property and long term stability for holding liquid of TiO₂ SLIPS attribute to the uniform nanostructures, the small diameter of the nanotubes, the smooth surface and high capillary force of TiO₂ nanotube arrays. Both the icing delay tests and the ice adhesion force tests conducted on TiO₂ SLIPS indicate that the long-term ice-phobic stability is strongly correlated with the surface smoothness and uniformity of nanostructures. The results show that large water droplets with size about 15 μL on TiO₂ NT based SLIPS can keep as liquid phase at very low temperature (–15 ℃) for up to 24 h, which exhibits much longer icing delay time at –15 ℃ than most of the reported superhydrophobic surfaces and SLIPS. And the TiO₂ SLIPS exhibit very good icing delay effect even after being reused for 17 times at –15 ℃, indicating the superior long-term stability and anti-icing effect of TiO₂ SLIPS as passive ice-phobic surfaces. The ice adhesion force of icicles on TiO₂ SLIPS was as low as ∼50 kPa after the tenth test, further indicating their long-term stability as anti-icing surfaces. In summary, the TiO₂ nanotube arrays based SLIPS obtained in this work exhibit superior slippery property, anti-biofouling, excellent anti-icing property and long term stability after being treated with a large amount of flowing water or reused for many times under very low temperature. This work shows that SLIPS can be applied as ice-phobic surfaces with long term stability at low temperature, potentially useful for their practical applications as anti-icing and ice-phobic surfaces.