D-119 Characterization of the Structure and Composition of Gecko Adhesive Setae: A Microdiffraction Study

Rizzo, Nancy; Walls, Dennis J.; Hallahan, David L.; Davidson, R. D.; Londono, J. D.; Gardner, K. H.

doi:10.1154/1.2754446

Cited by 5 publications

(7 citation statements)

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“…Applying this principle magnifies the slight force differences between the N and T substrates to the point that they can be resolved macroscopically. Tokay geckos possess %14 000 setae mm 22 [46] and there are % 100 terminal spatulae on each seta [21].…”

Section: Discussionmentioning

confidence: 99%

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Macroscale adhesion of gecko setae reflects nanoscale differences in subsurface composition

Loskill

Puthoff

Wilkinson

et al. 2013

J. R. Soc. Interface.

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Surface energies are commonly used to determine the adhesion forces between materials. However, the component of surface energy derived from long-range forces, such as van der Waals forces, depends on the material's structure below the outermost atomic layers. Previous theoretical results and indirect experimental evidence suggest that the van der Waals energies of subsurface layers will influence interfacial adhesion forces. We discovered that nanometre-scale differences in the oxide layer thickness of silicon wafers result in significant macroscale differences in the adhesion of isolated gecko setal arrays. Si/SiO 2 bilayer materials exhibited stronger adhesion when the SiO 2 layer is thin (approx. 2 nm). To further explore how layered materials influence adhesion, we functionalized similar substrates with an octadecyltrichlorosilane monolayer and again identified a significant influence of the SiO 2 layer thickness on adhesion. Our theoretical calculations describe how variation in the SiO 2 layer thickness produces differences in the van der Waals interaction potential, and these differences are reflected in the adhesion mechanics. Setal arrays used as tribological probes provide the first empirical evidence that the 'subsurface energy' of inhomogeneous materials influences the macroscopic surface forces.

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Section: Discussionmentioning

confidence: 99%

“…The underside of each toe is divided into lamellar structures that terminate in arrays of densely packed hair-like protrusions, called seta [19,20]. Individual setae are bundles of b-keratin fibrils several hundred micrometres long [21]. These fibrils terminate in triangular, wedge-shaped pads about 150 nm wide at the tip, called spatulae.…”

Section: Introductionmentioning

confidence: 99%

Macroscale adhesion of gecko setae reflects nanoscale differences in subsurface composition

Loskill

Puthoff

Wilkinson

et al. 2013

J. R. Soc. Interface.

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“…These keratins constitute a large part of the material of setae and form long bundles oriented along the main axes of setae. Previous studies on gecko epidermal proteins have indicated that ␤-keratins with a molecular weight of 10 -22 kDa are present and that they resemble those of normal scales (Thorpe and Giddings, 1981;Alibardi and Toni, 2005;Rizzo et al, 2006).…”

Section: Fig 2 A-cmentioning

confidence: 99%

Cloning and characterization of scale β‐keratins in the differentiating epidermis of geckoes show they are glycine‐proline‐serine–rich proteins with a central motif homologous to avian β‐keratins

Valle

Nardi

Toffolo

et al. 2006

Developmental Dynamics

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“…These structures, setae, are made primarily of -keratin (Alibardi, 2003) and in many species the setae are a highly branched hierarchical structure (Maderson, 1964;Ruibal and Ernst, 1965;Williams and Peterson, 1982). Setae, whether branched or not, terminate in flexible flattened tips approximately 200nm wide called spatulae (Ruibal and Ernst, 1965;Rizzo et al, 2006), which make intimate contact with rough and even dirty surfaces (Hansen and Autumn, 2005;Huber et al, 2007;Russell and Johnson, 2007). The van-der-Waals-based system is not without drawbacks, however; specifically, as a consequence of their intermolecular nature, van der Waals interactions are non-zero over only very small distances.…”

Section: Introductionmentioning

confidence: 99%

The effect of surface water and wetting on gecko adhesion

Stark

Sullivan

Niewiarowski

2012

Journal of Experimental Biology

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SUMMARYDespite profound interest in the mechanics and performance of the gecko adhesive system, relatively few studies have focused on performance under conditions that are ecologically relevant to the natural habitats of geckos. Because geckos are likely to encounter surfaces that are wet, we used shear force adhesion measurements to examine the effect of surface water and toe pad wetting on the whole-animal performance of a tropical-dwelling gecko (Gekko gecko). To test the effect of surface wetting, we measured the shear adhesive force of geckos on three substrate conditions: dry glass, glass misted with water droplets and glass fully submerged in water. We also investigated the effect of wetting on the adhesive toe pad by soaking the toe pads prior to testing. Finally, we tested for repeatability of the adhesive system in each wetting condition by measuring shear adhesion after each step a gecko made under treatment conditions. Wetted toe pads had significantly lower shear adhesive force in all treatments (0.86±0.09N) than the control (17.96±3.42N), as did full immersion in water (0.44±0.03N). Treatments with droplets of water distributed across the surface were more variable and did not differ from treatments where the surface was dry (4.72±1.59N misted glass; 9.76±2.81N dry glass), except after the gecko took multiple steps. These findings suggest that surface water and the wetting of a geckoʼs adhesive toe pads may have significant consequences for the ecology and behavior of geckos living in tropical environments.

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D-119 Characterization of the Structure and Composition of Gecko Adhesive Setae: A Microdiffraction Study

Cited by 5 publications

References 0 publications

Macroscale adhesion of gecko setae reflects nanoscale differences in subsurface composition

Macroscale adhesion of gecko setae reflects nanoscale differences in subsurface composition

Cloning and characterization of scale β‐keratins in the differentiating epidermis of geckoes show they are glycine‐proline‐serine–rich proteins with a central motif homologous to avian β‐keratins

The effect of surface water and wetting on gecko adhesion

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