Effect of the texture geometry on the slippery behavior of liquid-infused nanoporous surfaces

Slippery liquid-infused porous surfaces (SLIPS) achieve non-wetting properties through surfaces containing pockets of a lubricating liquid rather than of delicate air. Although studies have demonstrated the potential of SLIPS, such as self-cleaning, anti-icing, biomedical devices and non-fouling marine vessels, the effect of multiple phase structures on the motion of drops has not been thoroughly addressed. The present work was focused on the effect of texture geometry on the slipperiness of liquid-infused nanoporous surfaces. We fabricated a set of surfaces with liquid phase and solid phase coexistence using silicone oil as a lubricant and well-ordered nanoporous anodic alumina plates with various pore diameters and interpore distances. The non-wetting state on the fabricated SLIPS is a full Cassie–Baxter state. The results showed that static water contact angles on the SLIPS were mainly dependent on the non-wetting ability of the lubricant retained in the pores. However, a water droplet sliding angle (WSA) was sensitive to the texture geometry and exhibited a strong correlation with the area ratio of the lubricant phase on the SLIPS. A proposed equation in which the cosine of WSA was a negative linear correlation with the critical factor porosity (P) is a good model for the relationship between the WSA and texture geometry. This suggests that the water droplet slippery property can be altered by changing the porosity of the substrate for fabricating specific SLIPS.