Influence of Roughness on a Transparent Superhydrophobic Coating

Abstract

A novel fabrication process is presented using monodisperse PMMA latex particles to facilitate controlled microvoid formation. This results in hierarchically rough surfaces exhibiting ∼90% optical transmission while retaining water contact angle (θ) of 170°. Synchrotron small angle X-ray scattering, AFM roughness measurements, and theoretical modeling suggests that a surface morphology with fractal dimension of ∼2.6 and R a < 400 nm allows for the optimum coupling of roughness-induced superhydrophobicity and optical transparency. Interestingly, surfaces of vastly different roughness (R rms) exhibited similar water contact angles, highlighting a limitation of traditional AFM roughness measurements in quantifying multiscale rough surfaces. An alternate method considering fractal dimension is presented as a more complete quantifier of hierarchical surface morphology in relation to surface wetting behavior.

Diatom attachment inhibition: limiting surface accessibility through air entrapment

“…420 nm, 0.5 g) was added to the silica dispersion and further sonicated for 10 min. Methyltrimethoxysilane (MTMS) (98%, Sigma-Aldrich, 0.6 g) and concentrated HCl (36% w/v, AR, 60 μL) were added to the solution and allowed to react under sonication for 3 h to form the solgel solution [25].…”

“…All surfaces were fabricated by aggregating silica nanoparticles in a hydrophobic gel around PMMA latex particles, which were removed thermally during the curing process, leaving behind pores [25]. The resulting structure resembles a honeycomb constructed using nanoparticles ( Figure 1).…”

“…Further details and structural characterization of these surfaces can be found elsewhere [25]. The pore size was varied by incorporating latex particles of different sizes during the sol-gel reaction, which were then thermally removed.…”

Superhydrophobic and Omnidirectional Antireflective Surfaces from Nanostructured Ormosil Colloids

“…29 However, the challenge in preparing such multifunctional surfaces is to balance the high surface roughness requirement of superhydrophobic coatings with the low surface roughness requirement of antireflection coatings. 30 Therefore, to prepare antireflective and superhydrophobic surfaces, roughness must be optimized; it must be small enough to avoid diffuse reflection from the surface and high enough to provide superhydrophobicity. Although some groups have prepared surfaces combining the superhydrophobicity and high light transmission, 31−39 there are still several drawbacks that hinder the practical outdoor applications of such multifunctional coatings.…”

Chemical and Physical Pathways for Fabricating Flexible Superamphiphobic Surfaces with High Transparency

“…In addition to mechanical durability, optical transparency with both self-cleaning and antireflection features would be very beneficial in many applications, such as solar cells, LEDs, and optical lenses, since highly-transparent and water-repellent surfaces can improve the device performance by eliminating the reflection losses and lower the maintenance cost due to the self-cleaning property. However, the challenge in preparing such multifunctional surfaces is to balance both surface roughness and transparency of the antireflection coatings [56,57].…”