Superhydrophobic and superhydrophilic plant surfaces: an inspiration for biomimetic materials

Abstract

The diversity of plant surface structures, evolved over 460 million years, has led to a large variety of highly adapted functional structures. The plant cuticle provides structural and chemical modifications for surface wetting, ranging from superhydrophilic to superhydrophobic. In this paper, the structural basics of superhydrophobic and superhydrophilic plant surfaces and their biological functions are introduced. Wetting in plants is influenced by the sculptures of the cells and by the fine structure of the surfaces, such as folding of the cuticle, or by epicuticular waxes. Hierarchical structures in plant surfaces are shown and further types of plant surface structuring leading to superhydrophobicity and superhydrophilicity are presented. The existing and potential uses of superhydrophobic and superhydrophilic surfaces for self-cleaning, drag reduction during moving in water, capillary liquid transport and other biomimetic materials are shown.

‘Insect aquaplaning’ on a superhydrophilic hairy surface: howHeliamphora nutansBenth. pitcher plants capture prey

“…The discovery of a superhydrophilic hairy surface is interesting as many hairy plant surfaces are highly water-repellent [4][5][6][7][8], in particular when the hair density exceeds 25 mm 22 as is the case in H. nutans [4]. Water-absorbing trichomes occur in several plant families but they are morphologically specialized, e.g.…”

“…Trichomes usually render leaf surfaces water-repellent [4][5][6][7][8], although some are wettable and absorb water [9,10]. In carnivorous plants, they often have special functions, such as secretion (e.g.…”

Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

“…The self-cleaning action on hydrophobic surfaces is a consequence of their high water contact angles where almost spherical droplets form, which can easily roll away carrying foreign particles off the surface (Blossey 2003;Bhushan and Jung 2011;Liu and Jiang 2011). This form of selfcleaning via rolling droplets is thought to be one of the principle mechanism for removing contaminants from natural and artificial surfaces (Blossey 2003;Bhushan et al 2009;Koch and Barthlott 2009;Bhushan and Jung 2011;Liu and Jiang 2011).…”

“…These leaves possess a micro/nano architecture which reduces the contact area of particles with the surface and thus physical adhesion forces via van der Waals are also reduced. As the water droplet rolls over the surface, particles/contaminants are absorbed into or adhered to the water droplet surface via the interaction of stronger capillary forces (Koch and Barthlott 2009).…”

Biofouling: lessons from nature

“…Bioadhesion is the adhesion strength of biofouling on a hard surface. This depends on the organism type, substrate and separating fluid [84] owing to influences of electrostatic forces and surface wettability [85][86][87][88][89]. Biofilm bioadhesion is a two-stage process, starting with the initial attachment and then the irreversible attachment.…”