A comparative analysis of clinging ability among pad-bearing lizards

Irschick, Duncan J.; Austin, Christopher C.; Petren, Kenneth; Fisher, Robert N.; Losos, Jonathan B.; Ellers, Olaf

doi:10.1111/j.1095-8312.1996.tb01451.x

Cited by 345 publications

(189 citation statements)

References 44 publications

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“…It should be noted that clean foot force measurements quantify the maximum force that the outer layer of integument can withstand, not the maximum force of attachment by the setae. Shear force is strongly correlated with pad area (12), which differs among digits, so we standardized digit measurements by pad area. Force of attachment of clean toes on glass was measured for every digit on the left side of each animal.…”

Section: Methodsmentioning

confidence: 99%

Evidence for self-cleaning in gecko setae

Hansen

Autumn

2005

Proc. Natl. Acad. Sci. U.S.A.

548

411

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A tokay gecko can cling to virtually any surface and support its body mass with a single toe by using the millions of keratinous setae on its toe pads. Each seta branches into hundreds of 200-nm spatulae that make intimate contact with a variety of surface profiles. We showed previously that the combined surface area of billions of spatulae maximizes van der Waals interactions to generate large adhesive and shear forces. Geckos are not known to groom their feet yet retain their stickiness for months between molts. How geckos manage to keep their feet clean while walking about with sticky toes has remained a puzzle until now. Although self-cleaning by water droplets occurs in plant and animal surfaces, no adhesive has been shown to self-clean. In the present study, we demonstrate that gecko setae are a self-cleaning adhesive. Geckos with dirty feet recovered their ability to cling to vertical surfaces after only a few steps. Self-cleaning occurred in arrays of setae isolated from the gecko. Contact mechanical models suggest that self-cleaning occurs by an energetic disequilibrium between the adhesive forces attracting a dirt particle to the substrate and those attracting the same particle to one or more spatulae. We propose that the property of self-cleaning is intrinsic to the setal nanostructure and therefore should be replicable in synthetic adhesive materials in the future.adhesion ͉ contact mechanics ͉ locomotion ͉ reptilia ͉ nanotechnology

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Section: Methodsmentioning

confidence: 99%

Evidence for self-cleaning in gecko setae

Hansen

Autumn

2005

Proc. Natl. Acad. Sci. U.S.A.

548

411

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“…This structure allows the animal to adhere to almost any surface topography. To date, adhesion experiments were performed on the level of a whole foot (4,8) or of a single seta (still consisting of 100-1,000 spatulae). Recently, atomic force microscopy (AFM) was used to determine the pull-off force of even a single spatula (10).…”

mentioning

confidence: 99%

Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements

Huber

Mantz

Spolenak

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

586

494

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“…A number of biological studies (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) have found that arrays of setae are a common feature on the adhesion surfaces of many lizards and insects. In the biological literature, the shape, dimensions, and composition of setae from various species are described (1)(2)(3)(4)(5)(9)(10)(11)(12)(13)(14)(15)(16).…”

mentioning

confidence: 99%

Biologically inspired crack trapping for enhanced adhesion

Glassmaker

Jagota

Hui

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

244

270

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We present a synthetic adaptation of the fibrillar adhesion surfaces found in nature. The structure consists of protruding fibrils topped by a thin plate and shows an experimentally measured enhancement in adhesion energy of up to a factor of 9 over a flat control. Additionally, this structure solves the robustness problems of previous mimic structures and has preferred contact properties (i.e., a large surface area and a highly compliant structure). We show that this geometry enhances adhesion because of its ability to trap interfacial cracks in highly compliant contact regimes between successive fibril detachments. This results in the requirement that the externally supplied energy release rate for interfacial separation be greater than the intrinsic work of adhesion, in a manner analogous to lattice trapping of cracks in crystalline solids.interface ͉ fracture ͉ fibrillar ͉ lattice trapping ͉ biomechanics T he ability to adhere two surfaces strongly together and then reversibly separate them, repeatedly, is a desirable capability that is rarely achievable using conventional fabrication techniques and materials. Nevertheless, fibrillar surfaces with these properties have evolved in nature on the adhesive surfaces of the feet of many lizards and insects. With such natural surfaces as inspiration, we have developed a fibrillar structure that produces a robust, reusable material with strongly enhanced adhesion compared with a flat control of the same material, with the enhancement resulting only from the modification of surface geometry.The essential feature that our surfaces borrow from biology is the seta, a hair-like bristle having a diameter of 0.5-10 m and terminating in one or more flattened, expanded tips (''spatulas'') at its contacting end. A number of biological studies (1-16) have found that arrays of setae are a common feature on the adhesion surfaces of many lizards and insects. In the biological literature, the shape, dimensions, and composition of setae from various species are described (1-5, 9-16). Also, the mechanical properties and adhesion force of a single gecko seta (7) and even a single spatula (17,18) were the subjects of recent investigations. An important conclusion to emerge from these two studies is that setal arrays use noncovalent surface forces to achieve adhesion, and evidence suggests that geckos rely primarily on van der Waals and capillary forces (8, 18). As a result, the surface architecture is the primary design variable that has been adjusted in biological systems by evolution.Because of the extraordinary adhesion ability of animals that possess setal arrays, several researchers have recently made an effort to mimic the biological setal geometry by using synthetic materials (19)(20)(21)(22)(23)(24)(25)(26). It has been established theoretically that a fibrillar interface can increase both strength and interfacial toughness, compared with a flat control (21, 27-30). However, simple arrays of micropillars (19-21) have not exhibited stronger adhesion than flat control surfaces o...

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A comparative analysis of clinging ability among pad-bearing lizards

Cited by 345 publications

References 44 publications

Evidence for self-cleaning in gecko setae

Evidence for self-cleaning in gecko setae

Evidence for capillarity contributions to gecko adhesion from single spatula nanomechanical measurements

Biologically inspired crack trapping for enhanced adhesion

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