Biomimetic Random Arrays of Nanopillars and Nanocones with Robust Antiwetting Characteristics

Abstract

The presence of random arrays of elongated nanostructures with dimensional nonuniformity on the cuticular surfaces of insects endows them with antiwetting characteristics, as exemplified by nanopillar arrays on dragonfly wings and nanocone arrays on cicada wings. But the roles of the nanostructure shape and dimensional nonuniformity, as well as of the randomness of placement, on antiwetting characteristics are difficult to delineate because of the different chemical compositions of the surfaces of dragonfly and cicada wings. Therefore, biomimetic random arrays of nanopillars and nanocones with a similar tip diameter, placement irregularity, and chemical composition were fabricated on polypropylene substrates by plasma etching and polymerization. Gaussian nonuniformity of the nanopillar/nanocone dimensions as well as the irregularity of their placement were considered in determining the antiwetting capillary pressure and the adhesion energy. The gradient of the antiwetting capillary pressure normal to the substrate plane is the reason for nanocone arrays to resist wetting by water droplets impacting at high speeds much better than nanopillar arrays. The tapered shape of nanocones also promotes the dewetting transition of droplets from the sticky Wenzel state to the slippery Cassie state.

Hydrophobicity in clearwing Lepidoptera: impact of scale micro and nanostructure, and trade-off with optical transparency

“…(iv) Erect transparent lamellar scales are densely packed, as shown in Gomez et al (30), which can also increase their mechanical resistance. Further experiments are needed to elucidate these aspects, and clarify the role of nanostructures, as not only their presence, but their topography and its randomness have been recently suggested to play a role in determining antiwetting properties (51).…”

Long-Lived T-Shaped Micropillars with Submicron-Villi on PP/POE Surfaces with Grinding-Enhanced Water Repellency Fabricated via Hot Compression Molding

“…At present, superhydrophobic polymer surfaces have been extensively studied due to their broad application prospects in the fields of self-cleaning for protection strategies against fomites, 1 waterproof, 2,3 anti-icing, 4,5 superoleophobic, 6 and shape-memory materials. 7 Previous research studies have demonstrated that superhydrophobic properties are derived from the roughness of the surface and low-surface-energy materials.…”

“…At present, superhydrophobic polymer surfaces have been extensively studied due to their broad application prospects in the fields of self-cleaning for protection strategies against fomites, waterproof, , anti-icing, , superoleophobic, and shape-memory materials . Previous research studies have demonstrated that superhydrophobic properties are derived from the roughness of the surface and low-surface-energy materials. − What is more, enhanced superhydrophobic and self-cleaning effects appear on the animal epidermis and plant surfaces due to their submicron-villi as secondary structures on the papillae. − Bioinspired superhydrophobic surfaces were quite versatile but easy to damage.…”