Hierarchically Sculptured Plant Surfaces and Superhydrophobicity

Abstract

More than 400 million years of evolution of land plants led to a high diversity of adapted surface structures. Superhydrophobic biological surfaces are of special interest for the development of biomimetic materials for self-cleaning, drag reduction, and energy conservation. The key innovation in superhydrophobic biological surfaces is hierarchical sculpturing. In plants, a hydrophobic wax coating creates water-repelling surfaces that in combination with two or more levels of sculpturing leads to superhydrophobicity. Hierarchical structuring is of special interest for technical "biomimetic" materials with low adhesion and self-cleaning properties. Here we introduce hierarchical surface sculptures of plants with up to six levels. The article gives an overview of the composition of hierarchical surfaces for superhydrophobicity and their use as models for the development of artificial self-cleaning or drag-reducing surfaces.

A superoleophobic textile repellent towards impacting drops of alkanes

“…The air layer between solid and water is visible as a shiny silvery layer due to total internal reflection of light. This effect is well known for natural and artificial surfaces [19,31,32]. The existence of a plastron layer between our superoleophobic textile samples and alkanes is demonstrated in figure 3.…”

Plant surfaces with cuticular folds are slippery for beetles

“…We hypothesize that both high cuticular folds and hierarchical structuring with cuticular folds enable plant surfaces to keep a thin film of air due to their dimensions, reducing the contact area between water and the surface and leading to a Cassie and Baxter air-trapping wetting regime [25]. Both adhesion ability of male L. decemlineata and wettability have been found to be strongly affected by cuticular folds of different structuring.…”

Unraveling the Salvinia Paradox: Design Principles for Submerged Superhydrophobicity

“…The maximum ( t ransition s tate) separating two minima defi nes two free energy barriers, a "forward" and a "backward" one: Inspired by nature, [1][2][3] the study of superhydrophobicity has fl ourished in the last two decades allowing for an improved control of the wetting properties of surfaces of technological interest. [ 4,5 ] In particular, submerged superhydrophobicity is emerging as a means to reduce drag and prevent biofouling: such applications require robust gas-trapping inside surface asperities.…”