Tunable nano-replication to explore the omniphobic characteristics of springtail skin

Abstract

Springtails (Collembola) are wingless arthropods adapted to cutaneous respiration in temporarily rain-flooded and microbially contaminated habitats by a non-wetting and antiadhesive skin surface that is mechanically rather stable. Recapitulating the robust and effectively repellent surface characteristics of springtail skin in engineered materials may offer exciting opportunities for demanding applications, but it requires a detailed understanding of the underlying design principles. Towards this aim and based on our recent analysis of the structural features of springtail skin, we developed a tunable polymer replication process to dissect the contributions of different structural elements and surface chemistry to the omniphobic performance of the cuticle. The Cassie-Wenzel transition at elevated pressures was explored by in situ plastron collapse experiments and by numerical FEM simulations. The results obtained unravel the decisive role of nanoscopic cuticle structures for the protection of springtails against wetting, and explain how the evolved nanotopography enables the production of omniphobic surfaces even from intrinsically hydrophilic polymer materials.

Turning a surface superrepellent even to completely wetting liquids

“…For low energy liquids such as oils or organic solvents, a roughness with overhanging topology was necessary to make the hydrophobic material superoleophobic (13,14) or so-called omniphobic (15) or superomniphobic (16,17). Despite the use of prefix omni- (6,(15)(16)(17)(18), however, no natural or man-made surface has been reported to repel liquids of extremely low surface tension/energy (i.e., γ < 15 mJ/m 2 ), such as fluorinated solvents, which completely wet existing materials (10,(19)(20)(21). Departing from the prevailing approach of roughening a hydrophobic material, we first propose the material's inherent wettability, depicted by the intrinsic contact angle θ Y , is irrelevant when dealing with a completely wetting liquid (θ Y = 0°).…”

“…For θ Y < 90°, such as oils and organic solvents on a hydrophobic material or water on a slightly hydrophilic material, a re-entrant microstructure (Fig. 1B) is required to suspend the liquid and resist it from wetting into the cavity (3,8,10,(13)(14)(15)(16)(17)(18)25). From simple force balance, the re-entrant topology of Fig.…”

Combining the lotus leaf effect with artificial photosynthesis: regeneration of underwater superhydrophobicity of hierarchical ZnO/Si surfaces by solar water splitting

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] In recent years, the non-wetting property of superhydrophobic surfaces submerged in water has attracted much attention because it has potential applications in drag reduction, anti-fouling, anti-corrosion, waterproof devices, microchannels, anti-icing and other non-wetting related applications. [16][17][18][19][20][21][22][23][24][25] Practical applications of non-wetting surfaces, however, have been impeded by the limited stability of their underwater superhydrophobicity.…”

The multi-layered protective cuticle of Collembola: a chemical analysis

“…acid sample derivatization using o-phthalaldehyde for primary amino acids and 9-fluorenylmethyl chloroformate for secondary amino acids [46]. Measurements were performed by analytical HPLC Zorbax Eclipse-AAA column (4.6 Â 150 mm, 3.5 mm, Agilent Technologies, USA) for 40 min and a flow rate of 0.8 ml min 21 for the analytical column. A linear gradient of 0.1 M phosphate buffer ( pH7.8) and acetonitrile/methanol/ water 45/45/10 was used as the mobile phase.…”

“…Consequently, the collembolan cuticle is adapted to the soil habitat by a robust and repellent surface consisting of nanoscopic, comb-like structures (figure 1a) [14,20]. Polymer replication methods were applied to demonstrate that the particular structures enable a robust non-wetting state, even with low-surface-tension liquids, and, thus, protect the animals against suffocation, even when immersed [21,22].…”