Effect of Structure Hierarchy for Superhydrophobic Polymer Surfaces Studied by Droplet Evaporation

Abstract

Super-hydrophobic natural surfaces usually have multiple levels of structure hierarchy. Here, we report on the effect of surface structure hierarchy for droplet evaporation. The two-level hierarchical structures studied comprise micro-pillars superimposed with nanograss. The surface design is fully scalable as structures used in this study are replicated in polypropylene by a fast roll-to-roll extrusion coating method, which allows effective thermoforming of the surface structures on flexible substrates. As one of the main results, we show that the hierarchical structures can withstand pinning of sessile droplets and remain super-hydrophobic for a longer time than their non-hierarchical counterparts. The effect is documented by recording the water contact angles of sessile droplets during their evaporation from the surfaces. The surface morphology is mapped by atomic force microscopy (AFM) and used together with the theory of Miwa et al. to estimate the degree of water impregnation into the surface structures. Finally, the different behavior during the droplet evaporation is discussed in the light of the obtained water impregnation levels.

Biobased superhydrophobic coating enabled by nanoparticle assembly

“…36 Surface treatments oen refer to silane vapor deposition or liquid cast. [37][38][39][40][41] Surface roughness can be fabricated via colloidal lithography, 42 hot press, [43][44][45] mould, [46][47][48] and selective evaporation. 49 In addition, switchable hydrophilic and hydrophobic patterns have been designed for lotus-like self-cleaning capabilities.…”

Three-Dimensional Soft Material Micropatterning via Grayscale Photolithography for Improved Hydrophobicity of Polydimethylsiloxane (PDMS)

“…Many researchers have used the SU8-10 microhole mold to fabricate PDMS micropillars in their studies, as mentioned in Section 3.2 [7,[18][19][20]. We carried out the second experiment with the fabrication of the PDMS micropillar array by replicating the microhole pattern on the PDMS mold which is also referred to as PDMS-PDMS pattern transfer.…”

Micro 3D Printing by Two-Photon Polymerization: Configurations and Parameters for the Nanoscribe System

“…Microscale replication is often made with molds made from hard materials, such as electroformed Ni [39,40], but may also be formed using soft resins [41,42]. Therefore, 3D printing of soft structures could be very valuable for producing master molds that can be used for subsequent replication.…”