Wetting Resistance at Its Topographical Limit: The Benefit of Mushroom and Serif T Structures

Abstract

Springtails (Collembola) are wingless arthropods adapted to cutaneous respiration in temporarily rain-flooded habitats. They immediately form a plastron, protecting them against suffocation upon immersion into water and even low-surface-tension liquids such as alkanes. Recent experimental studies revealed a high-pressure resistance of such plastrons against collapse. In this work, skin sections of Orthonychiurus stachianus are studied by transmission electron microscopy. The micrographs reveal cavity side-wall profiles with characteristic overhangs. These were fitted by polynomials to allow access for analytical and numerical calculations of the breakthrough pressure, that is, the barrier against plastron collapse. Furthermore, model profiles with well-defined geometries were used to set the obtained results into context and to develop a general design principle for the most robust surface structures. Our results indicate the decisive role of the sectional profile of overhanging structures to form a robust heterogeneous wetting state for low-surface-tension liquids that enables the omniphobicity. Furthermore, the design principles of mushroom and serif T structures pave the way for omniphobic surfaces with a high-pressure resistance irrespective of solid surface chemistry.

Unraveling the Salvinia Paradox: Design Principles for Submerged Superhydrophobicity

“…More complex geometries, such as the doubly re-entrant "serif T" ( φ 1 = 90° and φ 2 ≈ 0°), [ 32 ] can be designed in order to repel liquids with low contact angles ( θ in = θ top ≈ 0°). [ 33 ] In this case, the meniscus is pinned at the innermost corner for Δ P > 0 (see Figure 3 b and the Supporting Information).…”

Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

“…M otivated by a broad potential impact on science and technology, the design of liquid-repellent surfaces has been the subject of intense research that has led to the development of superhydrophobic [1][2][3][4] and, more recently, superomniphobic [5][6][7][8][9] surface coatings, which show resistance to water and organic liquids, respectively. The design of such surfaces has been adapted from nature's famously self-cleaning lotus leaves 10 .…”

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

“…The epicuticle contains the distinctive surface features of Collembola in displaying a comb-like mesh covering the entire body. Cavities inside the epicuticular mesh allow for respiration [12,13]. The nanoscopic tubercles at the intersections of the mesh structure prevent liquids wetting these cavities facilitating respiration under wet conditions and preventing suffocation in temporarily rain-flooded habitats.…”