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. The wetting behavior of a material's surface is a property of fundamental interest to material scientists. Springtails, also known as collembola, are soil-dwelling arthropods that typically respire through their skin. To avoid suffocating in wet conditions, springtails have evolved a complex, hierarchically nanostructured skin surface that repels water with remarkable efficiency. Carsten Werner at the Leibniz Institute of Polymer Research Dresden, Germany, and his colleagues have carried out numerical simulations and made accurate polymer-based replicas of this skin surface in order to understand better its anti-wetting behavior. Their results show that tiny overhangs in the nanostructure help to trap air against the surface in the wet, providing an effective barrier against wetting. The researchers further showed that even intrinsically hydrophilic materials will repel water when structured in this way. An improved understanding of springtail skin behaviour provides valuable insights that will aid scientists to design engineered materials with improved anti-wetting properties. Springtails, wingless arthropods, are adapted to cutaneous respiration in temporarily rain-flooded habitats by a hierarchically structured skin surface. A tunable polymer replication process was applied to dissect the contributions of different structural elements and surface chemistry to the omniphobic performance of the skin.