Optical analysis of a transparent slippery surface by controlling the refractive index of the porous structure

This report demonstrates the fabrication of a transparent slippery surface and an investigation of its transparent property by systematically controlling the refractive index. The slippery surface, fabricated by a simple method, was shown to have a water-repellent property similar to those of captured insects sliding into the pitcher of Nepenthes. The as-fabricated opaque porous structures were covered by a siloxane lubricant and showed high optical transmittance in the visible light region. In particular, the difference in the refractive indices between the lubricant and porous structure served as a crucial variable for obtaining a transparent surface. Slippery surfaces were fabricated by using various kinds of nanoparticles (SiO2, Al2O3, ZrO2, and TiO2), and the mechanism behind the transparency of these surfaces was investigated by comparing their transmittances using a UV spectrophotometer. The results show that SiO2 nanoparticle, with a refractive index of 1.46, is the most suitable material for use with the siloxane lubricant. The average transmittance of the slippery surface composed of SiO2 nanoparticle is approximately 80% in the visible light region. Through this study, the transparency of slippery surfaces can be further understood.