Biomimetics on the micro- and nanoscale – The 25th anniversary of the lotus effect

• Matthias Mail,
• Kerstin Koch,
• Thomas Speck,
• William M. Megill and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2023, 14, 850–856, doi:10.3762/bjnano.14.69

• Zoology, Christian-Albrechts-University of Kiel, Am Botanischen Garten 1–9, D-24118 Kiel, Germany 10.3762/bjnano.14.69 Keywords: biomimetic surfaces; hydrophobicity; lotus effect; Salvinia effect; superhydrophobicity; wettability; In 1997, Wilhelm Barthlott and Christoph Neinhuis published the paper

• repellency, but also on the capability of some surfaces to keep stable air layers under water – the so-called Salvinia Effect. Such air layers are of great importance for drag reduction (passive air lubrication), antifouling, sensor applications, or oil–water separation. Up to now, based on the

Dry under water: air retaining properties of large-scale elastomer foils covered with mushroom-shaped surface microstructures

• Matthias Mail,
• Stefan Walheim,
• Thomas Schimmel,
• Wilhelm Barthlott,
• Stanislav N. Gorb and
• Lars Heepe

Beilstein J. Nanotechnol. 2022, 13, 1370–1379, doi:10.3762/bjnano.13.113

• air lubrication; Salvinia effect; superhydrophobicity; Introduction Superhydrophobicity is one of the key innovations in the biological evolution of organisms for the conquest of land [1]. Recently it was shown that this fascinating surface property evolved already in the cyanobacterium Hassallia [2

• superhydrophobic surfaces and self-cleaning properties are available on the market [1][6][7]. A most interesting feature of certain superhydrophobic surfaces is their ability to maintain a persistent air layer submerged under water. This ability is called Salvinia effect [5][8][9][10]. Due to the hydrophobic

• chemistry of the hierarchically structured surfaces water cannot penetrate and air remains trapped in between the structures [1], which is indicated by a silvery shine of the submerged surface (See Figure 1a). For technical applications, the Salvinia effect bears an immense potential, as air layers kept

Straight roads into nowhere – obvious and not-so-obvious biological models for ferrophobic surfaces

• Wilfried Konrad,
• Christoph Neinhuis and
• Anita Roth-Nebelsick

Beilstein J. Nanotechnol. 2022, 13, 1345–1360, doi:10.3762/bjnano.13.111

• (Figure 2). These are able to hold the resulting air layer for extended periods of time upon immersion. The interface is also resilient against perturbations. The “Salvinia effect” has considerable biomimetic potential, for instance, with respect to fuel reduction in maritime shipping [24][25] because an

A new bioinspired method for pressure and flow sensing based on the underwater air-retaining surface of the backswimmer Notonecta

• Matthias Mail,
• Adrian Klein,
• Horst Bleckmann,
• Anke Schmitz,
• Torsten Scherer,
• Peter T. Rühr,
• Goran Lovric,
• Robin Fröhlingsdorf,
• Stanislav N. Gorb and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2018, 9, 3039–3047, doi:10.3762/bjnano.9.282

• . Keywords: mechanoreceptor; Notonecta sensor; pressure sensor; Salvinia effect; superhydrophobic surfaces; Introduction The surfaces of animals and plants are interfaces between the organisms and the environment. Since animals and plants inhabit many different environments, it is not surprising that over

• adhesive pads [6] or the structural colors of Morpho menelaus [7]. Superhydrophobic surfaces are also important in the above context. Several plants and animals, which can maintain stable air layers while submerged (Salvinia effect [8]), have been analyzed. Especially the floating ferns of the genus

Air–water interface of submerged superhydrophobic surfaces imaged by atomic force microscopy

• Markus Moosmann,
• Thomas Schimmel,
• Wilhelm Barthlott and
• Matthias Mail

Beilstein J. Nanotechnol. 2017, 8, 1671–1679, doi:10.3762/bjnano.8.167

• of increasing interest for technical applications. Persistent air layers (the Salvinia effect) are known from biological species, for example, the floating fern Salvinia or the backswimmer Notonecta. The use of this concept opens up new possibilities for biomimetic technical applications in the

• years, the Salvinia effect – the long term stabilization of an air layer on a submerged surface – has gained increasing interest. There is great potential for various technical applications utilizing this effect, for example, drag reduction, antifouling or anticorrosion applications, and underwater

• sputter-coated onto the surface to enhance their conductivity. Biological role models of air-retaining Salvinia effect surfaces. a) The floating fern Salvinia molesta has one of the most complex surface structures in plants. Reproduced with permission from [5], copyright 2010 Wiley-VCH Verlag GmbH & Co

Biological and biomimetic materials and surfaces

• Stanislav Gorb and
• Thomas Speck

Beilstein J. Nanotechnol. 2017, 8, 403–407, doi:10.3762/bjnano.8.42

• fields of basic and applied research, as can be seen in some articles of this Thematic Series. A second type of surface structure that has been observed is the so-called Salvinia effect that has been quantitatively characterized in collaboration with Thomas Schimmel from the Karlsruhe Institute of

• diving. The main interest in biomimetic products lies in the potential friction reduction and in antifouling properties. For example, this could be practically implemented by covering the underwater parts of ship hulls with Salvinia effect coatings. Ongoing projects with ship builders aim to realize this

The capillary adhesion technique: a versatile method for determining the liquid adhesion force and sample stiffness

• Daniel Gandyra,
• Stefan Walheim,
• Stanislav Gorb,
• Wilhelm Barthlott and
• Thomas Schimmel

Beilstein J. Nanotechnol. 2015, 6, 11–18, doi:10.3762/bjnano.6.2

• cantilevers, reproducing the spring constants calibrated using other methods. Keywords: adhesion; AFM cantilever; air layer; capillary forces; hairs; measurement; micromechanical systems; microstructures; Salvinia effect; Salvinia molesta; sensors; stiffness; superhydrophobic surfaces; Introduction Surface

• ], it is interesting to study the properties of the hairs of Salvinia molesta as a model for future developments. The key factors are the high water adhesion of the trichome tips (the “Salvinia effect”, [1]) and the high elasticity of the trichomes [2][3], which allows the pinning of the air–water

• permanent layer of air under water. As demonstrated, Salvinia molesta maintains this persistent air layer with a unique combination of hydrophobic hairs (trichomes) exhibiting hydrophilic, water-attracting tips (the Salvinia effect) [1]. The hydrophobic properties of the trichome surface prevent water from

Measuring air layer volumes retained by submerged floating-ferns Salvinia and biomimetic superhydrophobic surfaces

• Matthias J. Mayser,
• Holger F. Bohn,
• Meike Reker and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2014, 5, 812–821, doi:10.3762/bjnano.5.93

• of Freiburg, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany 10.3762/bjnano.5.93 Abstract Some plants and animals feature superhydrophobic surfaces capable of retaining a layer of air when submerged under water. Long-term air retaining surfaces (Salvinia-effect) are of high interest for

• also allows to measure decrease or increase of air layers with high accuracy in real-time to understand dynamic processes. Keywords: air layer; biomimetic; drag reduction; functional surfaces; plastron; Salvinia effect; volume measurement; Introduction Since the description of hierarchically

• perpendicular to the surface [33][34][35]. As special characteristic of S. molesta the topmost cells of its hairs lack the wax cover and are thereby hydrophilic while the remaining part is hydrophobic. The resulting pinning of the water to these hydrophilic tips 'Salvinia-effect' has been proven to increase the

Hierarchically structured superhydrophobic flowers with low hysteresis of the wild pansy (Viola tricolor) – new design principles for biomimetic materials

• Anna J. Schulte,
• Damian M. Droste,
• Kerstin Koch and
• Wilhelm Barthlott

Beilstein J. Nanotechnol. 2011, 2, 228–236, doi:10.3762/bjnano.2.27

• (“Lotus effect”) [4][5][6] or cause air retention under water (“Salvinia effect”) [7][8]. Superhydrophobic, self-cleaning surfaces possess a static contact angle (CA) equal to or above 150°, and a low hysteresis angle, where water droplets roll-off at surface inclinations equal to or below 10° [6][9]. One