Beyond biomimicry – next generation applications of bioinspired adhesives from microfluidics to composites

• Dan Sameoto

Beilstein J. Nanotechnol. 2024, 15, 965–976, doi:10.3762/bjnano.15.79

• composites are highlighted in this article. It is time for a next generation of research to look beyond biomimicry and look towards re-engineering applications to make use of these materials’ unique properties in economically viable ways. Keywords: adhesion; biomimicry; composites; gecko; robotics, soft

• lithography; Perspective As of the time of this writing, it has been 24 years since the seminal work by Kellar Autumn and his colleagues demonstrated how a single gecko foot hair could generate adhesion [1]. Autumn’s discovery that van der Waals forces were the primary mechanism behind the extraordinary

• traditional microfluidics liquids like oil and water, another student in 2017 demonstrated its utility for integrating liquid metal electronics. Mersedeh Zandvakili showed in 2017 that eutectic gallium–indium could be injected into microfluidic channels, and the gecko pillars not only provided adhesion for

The effect of age on the attachment ability of stick insects (Phasmatodea)

• Marie Grote,
• Stanislav N. Gorb and
• Thies H. Büscher

Beilstein J. Nanotechnol. 2024, 15, 867–883, doi:10.3762/bjnano.15.72

• system to statically hold the insect’s weight on the ceiling. Apart from insects, roughness plays a role in adhesion of non-arthropods as well. Roughnesses of 100–300 nm had the largest attachment-reducing effect for both single setae and whole geckos in experiments with the species Gekko gecko (Linnaeus

Functional fibrillar interfaces: Biological hair as inspiration across scales

• Guillermo J. Amador,
• Brett Klaassen van Oorschot,
• Caiying Liao,
• Jianing Wu and
• Da Wei

Beilstein J. Nanotechnol. 2024, 15, 664–677, doi:10.3762/bjnano.15.55

• , which branch into spatulae at the tips [60]. The branching ensures a high density of hairs to generate high adhesive forces [61]. With advances in fabrication techniques at the micrometer scale, gecko-inspired adhesive hairs have been developed, which are capable of generating adhesion without the use

• twist.glyph (bacteria). Locomotion enhanced by hairs. Schematics showing (A) an array of hairs (or setae and spatulae) on the toe pad of a climbing gecko, (B) hairs (or setae) on the body of a burrowing earthworm for anchoring when pushing through soil, (C) hairs (or bristles) on the wing of a thrip, instead

• attributed to the following creators: Hey Rabbit (gecko) and DracoVisions (earthworm). Sensing via hairs. Schematics showing (A) whiskers on cats sensing objects through mechanical interactions, (B) hairs on the antennae of ants detecting the odor of molecules, and (C) hairs on the labial palps of cave

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

• tune and then scale up the fabrication of tools to handle nanofibres in industrial processes. Fibre–surface interactions are also the main theme in “Growing up in a rough world: scaling of frictional adhesion and morphology of the Tokay gecko (Gekko gecko)” by Cobos and Higham [15]. In the excitement

• of the biomimetic abstraction and development process, in particular when it looks like it is leading to a product, one can sometimes miss some of the important secondary features of the biological archetypes. This paper reminds us of this as it explores the relationship of gecko foot pad adhesion

• example of a light-weight structure. b) A gecko – one of the best-known archetypes for biomimetic adhesion. c) An example of the curiosities that nature holds – a slime mould whose spores exhibit superhydrohobic properties. d) A pitcher plant, which has on the edges a special and very slippery surface to

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

• and that the biomimetic elastomer foil is a promising base for the development of an economically and efficient biomimetic air retaining surface for a broad range of technical applications. Keywords: adhesive tape; air layer; air retention; bionics; fouling; gecko tape; mushroom structures; passive

Growing up in a rough world: scaling of frictional adhesion and morphology of the Tokay gecko (Gekko gecko)

• Anthony J. Cobos and
• Timothy E. Higham

Beilstein J. Nanotechnol. 2022, 13, 1292–1302, doi:10.3762/bjnano.13.107

• ability to adhere to surfaces in nature. Using Tokay geckos (Gekko gecko), we examined the post-hatching scaling of morphology and frictional adhesive performance in animals ranging from 5 to 125 grams in body mass. We quantified setal density, setal length, and toepad area using SEM. This was then used

• relevant variables. The ability of geckos to adhere to smooth surfaces has fascinated scientists since Aristotle, and has been followed by countless studies focused on uncovering the mechanisms of gecko adhesion, from as early as the 1800’s [6][7][8][9][10] to modern investigations (reviewed in [3]). Like

• the Lotus Effect [11], the Gecko Effect has seen a surge in attention over the past couple of decades [12]. There are over 1000 species of geckos with adhesive capabilities, with multiple origins of the system [13][14]. However, much of what is known about gecko adhesion and its associated structures

Physical constraints lead to parallel evolution of micro- and nanostructures of animal adhesive pads: a review

• Thies H. Büscher and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2021, 12, 725–743, doi:10.3762/bjnano.12.57

• asymmetry of micro- and nanostructural features (scheme is given in the inset) in animal attachment pads, leading to functional anisotropy upon contact. Longitudinal sections of pads are visualised in SEM (A,B,D) and in light microscope (C). (A,B) Tokay Gekko gecko (hairy pad). (C) Fly Calliphora vicina

Contact splitting in dry adhesion and friction: reducing the influence of roughness

• Jae-Kang Kim and
• Michael Varenberg

Beilstein J. Nanotechnol. 2019, 10, 1–8, doi:10.3762/bjnano.10.1

• more easily to the surface waviness and by reducing the effective average peeling angle. These findings can be used to guide the development of biomimetic shear-actuated adhesives suitable for operation not only on smooth but also on rough surfaces. Keywords: biomimetics; contact splitting; gecko

• biological adhesives is to achieve efficient and easily controllable adhesion on any surface, it is important to understand how to overcome the negative effects of roughness on attachment of thin films. It was shown that gecko adhesion is lower if the substrate waviness wavelength is comparable to the

The effect of flexible joint-like elements on the adhesive performance of nature-inspired bent mushroom-like fibers

• Elliot Geikowsky,
• Serdar Gorumlu and
• Burak Aksak

Beilstein J. Nanotechnol. 2018, 9, 2893–2905, doi:10.3762/bjnano.9.268

• : bent fibers; bioinspired dry adhesives; gecko adhesion; joint-like element; mushroom-like fibers; Introduction Most natural organisms that rely on temporary adhesion to surfaces for survival do so using tiny, densely packed fibers [1][2]. These fibers vary in dimension and material properties

• micrometer-scale setae, to the nanometer-scale spatulae at the contact level, fibers are made from beta keratin [8] which has an elastic modulus of 1–4 GPa [9]. To enhance performance, given the high elastic modulus, all of the hierarchical levels forming the adhesive patch of the gecko are tilted rather

• than vertically aligned [10]. This tilt, in addition to enhanced performance [11], equips the gecko with directional adhesion properties as shown by Autumn et al. [12]. When they tested setae using a load–drag–pull (LDP) experiment, they found that setae exhibit very high interfacial shear and tension

Biomimetic surface structures in steel fabricated with femtosecond laser pulses: influence of laser rescanning on morphology and wettability

• Camilo Florian Baron,
• Alexandros Mimidis,
• Daniel Puerto,
• Evangelos Skoulas,
• Emmanuel Stratakis,
• Javier Solis and
• Jan Siegel

Beilstein J. Nanotechnol. 2018, 9, 2802–2812, doi:10.3762/bjnano.9.262

• surface structures; laser rescanning; steel; wettability; Introduction Complex structures found in nature often present properties that are attractive for applications in science and technology. The hydrophobicity found at the lotus leaf surface [1], the exceptional adhesion capability of gecko feet [2

Adhesive contact of rough brushes

• Qiang Li and
• Valentin L. Popov

Beilstein J. Nanotechnol. 2018, 9, 2405–2412, doi:10.3762/bjnano.9.225

• gecko feet and structured biomimetic materials. For rigid brushes, the contact splitting does not enhance adhesion even if all pillars of the brush are positioned at the same height. Introducing statistical scatter of height leads to a further decrease of the maximum adhesive strength. At the same time

Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations

• Jaison Jeevanandam,
• Ahmed Barhoum,
• Yen S. Chan,
• Alain Dufresne and
• Michael K. Danquah

Beilstein J. Nanotechnol. 2018, 9, 1050–1074, doi:10.3762/bjnano.9.98

• force in the physical form contribute to their adhesion. In recent reports, the reason for adhesion of gecko setae is due to van der Waals interaction through strong evidence [237] and rejects the capillary adhesion mechanisms. It was predicted that application of contact mechanics may help in smaller

• design. The nacreous effect is caused by the thin layer of a rough surface with groovy nanostructures [240]. Other than the nacreous effect, gecko feet have the capability to walk on ceilings against gravity and even on wet or slippery surfaces. This property is linked to the nanometer-sized hair-like

• structures in their feet that are aligned in a series of a small ridges with a projection of 200 nm width in each hair. This increases the total surface area of gecko feet and leads to a van der Waals interaction mediated strong surface adhesion [241]. Similarly, the crystalline composite of CaCO3 crystals

Dry adhesives from carbon nanofibers grown in an open ethanol flame

• Christian Lutz,
• Julia Syurik,
• C. N. Shyam Kumar,
• Christian Kübel,
• Michael Bruns and
• Hendrik Hölscher

Beilstein J. Nanotechnol. 2017, 8, 2719–2728, doi:10.3762/bjnano.8.271

• nearly every surface and adhere to it due to van der Waals forces, allowing the gecko to stick and climb nearly every surface [19][20][21]. Mimicking these nanostructures can lead to high performance dry adhesives with a great range of possible applications in attachment systems of climbing robots [22

• GPa [30]. CNTs act similarly to the hairs of a Gecko, due to their diameters in the nanometer-range, they can bend quite easily when getting in contact with a rough surface. This effect enables effective contact splitting [31], which leads to an increased contact area, resulting in a high adhesion

• . Calculated from the touching area of the spherical cantilever (projected area), which is approximately 42 μm2, the adhesion strength corresponds to 0.66 N/cm2. This is considerably lower as the adhesion of real gecko footpads (10 N/cm2) [19], but the adhesion strength might be improved by smaller CNF

Biological and biomimetic materials and surfaces

• Stanislav Gorb and
• Thomas Speck

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

• exaggeration one can say that Lotus-Effect® surfaces, together with fasteners inspired by gecko attachment structures, can be considered as “flagships” of contemporary surface-related biomimetic research. Still today questions related to these effects are the topic of novel state-of-the-art studies in the

Influence of ambient humidity on the attachment ability of ladybird beetles (Coccinella septempunctata)

• Lars Heepe,
• Jonas O. Wolff and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2016, 7, 1322–1329, doi:10.3762/bjnano.7.123

• ) humidity-dependent material properties of insect cuticle and β-keratin (main constituent of gecko setae) [41][42][43][44]. In geckos, the effect of a RH on viscoelastic properties of the setal shaft was shown [13]. It was argued that with an increasing humidity the viscoelastic bulk energy dissipation

Aquatic versus terrestrial attachment: Water makes a difference

• Petra Ditsche and
• Adam P. Summers

Beilstein J. Nanotechnol. 2014, 5, 2424–2439, doi:10.3762/bjnano.5.252

• , lock, clamp and spacer) significant differences have to be considered under water. For example, the main principles of dry adhesion, van der Waals forces and chemical bonding, which make a gecko stick to the ceiling, are weak under submerged conditions. Capillary forces are very important for wet

• attachment forces in these disparate arenas. The difference between a submerged attachment event and one that is dry is neither clear-cut nor simple. Consider the classic example of a toe of a gecko adhered to a leaf. On its face, this is a case of terrestrial adhesion, but depending on humidity there could

Equilibrium states and stability of pre-tensioned adhesive tapes

• Carmine Putignano,
• Luciano Afferrante,
• Luigi Mangialardi and
• Giuseppe Carbone

Beilstein J. Nanotechnol. 2014, 5, 1725–1731, doi:10.3762/bjnano.5.182

• fact that they are usually constituted mainly of a relatively stiff material, namely β-keratin. The study of the mechanism of detachment of thin films can also help to elucidate some aspect of insects and, in particular, gecko adhesion. To avoid toe detachment, the gecko often employs the use of

From sticky to slippery: Biological and biologically-inspired adhesion and friction

• Stanislav N. Gorb and
• Kerstin Koch

Beilstein J. Nanotechnol. 2014, 5, 1450–1451, doi:10.3762/bjnano.5.157

• theoretical studies which range from insect adhesion, bacterial adhesion and skin friction to artificial biomimetic systems, e.g., snake-skin inspired polymer patterns or gecko tape. The Thematic Series does not attempt to give a comprehensive overview of the emerging field of biological contact mechanics

Dry friction of microstructured polymer surfaces inspired by snake skin

• Martina J. Baum,
• Lars Heepe,
• Elena Fadeeva and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2014, 5, 1091–1103, doi:10.3762/bjnano.5.122

• been previously shown that the attachment ability of insects [62][63][64][65] and geckos [66] is strongly dependent on the surface roughness. Yu et al. [67] demonstrated that surface roughness also strongly affects the performance of gecko-inspired adhesives. All these authors have shown that there is

Direct observation of microcavitation in underwater adhesion of mushroom-shaped adhesive microstructure

• Lars Heepe,
• Alexander E. Kovalev and
• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2014, 5, 903–909, doi:10.3762/bjnano.5.103

• in predominantly liquid environments. Keywords: bio-inspired; biomimetic; cavitation; contact mechanics; gecko; interface; negative pressure; pull-off; surface; tribology; Introduction During the past two decades, bio-inspired microstructured adhesives became a new class of adhesive materials with

The optimal shape of elastomer mushroom-like fibers for high and robust adhesion

• Burak Aksak,
• Korhan Sahin and
• Metin Sitti

Beilstein J. Nanotechnol. 2014, 5, 630–638, doi:10.3762/bjnano.5.74

• , USA 10.3762/bjnano.5.74 Abstract Over the last decade, significant effort has been put into mimicking the ability of the gecko lizard to strongly and reversibly cling to surfaces, by using synthetic structures. Among these structures, mushroom-like elastomer fiber arrays have demonstrated promising

• performance on smooth surfaces matching the adhesive strengths obtained with the natural gecko foot-pads. It is possible to improve the already impressive adhesive performance of mushroom-like fibers provided that the underlying adhesion mechanism is understood. Here, the adhesion mechanism of bio-inspired

• adhesives. Keywords: gecko; mushroom-like fibers; adhesion; Introduction We need to look no further than nature to find inspiration for many of the technologies we work on today. One such field that observations on natural systems have impacted significantly in the recent years is adhesive technologies

Functionalization of vertically aligned carbon nanotubes

• Eloise Van Hooijdonk,
• Carla Bittencourt,
• Rony Snyders and
• Jean-François Colomer

Beilstein J. Nanotechnol. 2013, 4, 129–152, doi:10.3762/bjnano.4.14

• demonstration of writing, using patterned aligned nanotubes (Figure 4) [63]. An interesting example of patterned aligned carbon nanotubes is the engineering of gecko-foot-mimetic dry adhesives. Patterning is employed to effectively reproduce the setae of gecko composed of many lobes, aimed at obtaining the

• with abilities to controllably release objects trapped within the systems. For example, we can imagine the production of antifouling devices, gecko-like artificial devices, functional membranes, or sensors. Wardle et al. [152] assessed the density of VA-CNTs that it is possible to insert in a PM with a

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

• Jiang [16] proposed five different states for superhydrophobic surfaces, where the lotus and gecko states are treated as special cases in the Cassie–Baxter model. Feng et al. [17] proposed a sixth superhydrophobic state, called the “Cassie impregnating wetting state” or “petal effect”. Both describe

Review of "Contact Mechanics and Friction: Physical Principles and Applications" by Valentin L. Popov

• Stanislav N. Gorb

Beilstein J. Nanotechnol. 2011, 2, 57–58, doi:10.3762/bjnano.2.7

• impact on the performance of the system [6]. Since biological examples are increasingly used to design novel technical systems (biomimetics), such as friction-induced worm-like motion, artificial joints for medical applications, gecko-inspired sticky tapes, etc., the book might aid in guiding such