Orientation angle and the adhesion of single gecko setae

Hill, Ginel C.; Soto, Daniel; Peattie, Anne M.; Full, Robert J.; Kenny, Thomas W.

doi:10.1098/rsif.2010.0720

Cited by 21 publications

(18 citation statements)

References 47 publications

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“…It is also possible that the local angle of the surface features determines clinging ability, and this has been demonstrated at the setal size scale (Autumn et al, 2000;Gravish et al, 2008;Hill et al, 2011). During contact, the lamella can be seen bending to an angle in order to conform to the surface, and this angle may be determined by the ratio of lamella to surface feature size.…”

Section: Research Articlementioning

confidence: 99%

Gecko toe and lamellar shear adhesion on macroscopic, engineered rough surfaces

Gillies

Henry

Lin

et al. 2013

Journal of Experimental Biology

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The role in adhesion of the toes and lamellae -intermediate-sized structures -found on the gecko foot remains unclear. Insight into the function of these structures can lead to a more general understanding of the hierarchical nature of the gecko adhesive system, but in particular how environmental topology may relate to gecko foot morphology. We sought to discern the mechanics of the toes and lamellae by examining gecko adhesion on controlled, macroscopically rough surfaces. We used live Tokay geckos, Gekko gecko, to observe the maximum shear force a gecko foot can attain on an engineered substrate constructed with sinusoidal patterns of varying amplitudes and wavelengths in sizes similar to the dimensions of the toes and lamellae structures (0.5 to 6 mm). We found shear adhesion was significantly decreased on surfaces that had amplitudes and wavelengths approaching the lamella length and inter-lamella spacing, losing 95% of shear adhesion over the range tested. We discovered that the toes are capable of adhering to surfaces with amplitudes much larger than their dimensions even without engaging claws, maintaining 60% of shear adhesion on surfaces with amplitudes of 3 mm. Gecko adhesion can be predicted by the ratio of the lamella dimensions to surface feature dimensions. In addition to setae, remarkable macroscopic-scale features of gecko toes and lamellae that include compliance and passive conformation are necessary to maintain contact, and consequently, generate shear adhesion on macroscopically rough surfaces. Findings on the larger scale structures in the hierarchy of gecko foot function could provide the biological inspiration to drive the design of more effective and versatile synthetic fibrillar adhesives.

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Section: Research Articlementioning

confidence: 99%

Gecko toe and lamellar shear adhesion on macroscopic, engineered rough surfaces

Gillies

Henry

Lin

et al. 2013

Journal of Experimental Biology

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“…Setae that are hydrated in water are likely to also decrease in modulus, perhaps even more than in high humidity environments. The gecko adhesive system is also extremely directionally dependent: setae must be oriented and loaded correctly for successful adhesion (Autumn et al, 2000;Autumn and Hansen, 2006;Hill et al, 2011). A significant drop in setal modulus from extreme hydration likely increases disorder in the setal mat and causes setae to self-tangle and buckle more readily, thus lowering adhesive contact area and performance.…”

Section: Initialmentioning

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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“…This could be again owing to local surface angle reducing the effective peel angle of the fibre. It has been verified experimentally that local orientation of the seta has a large impact on the adhesive forces [44]. As the surface amplitude increases, so does the wavelength at which this spike in adhesion occurs.…”

Section: Arrays On Sinusoidal Surfacesmentioning

confidence: 99%

Simulation of synthetic gecko arrays shearing on rough surfaces

Gillies

Fearing

2014

J. R. Soc. Interface.

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To better understand the role of surface roughness and tip geometry in the adhesion of gecko synthetic adhesives, a model is developed that attempts to uncover the relationship between surface feature size and the adhesive terminal feature shape. This model is the first to predict the adhesive behaviour of a plurality of hairs acting in shear on simulated rough surfaces using analytically derived contact models. The models showed that the nanoscale geometry of the tip shape alters the macroscale adhesion of the array of fibres by nearly an order of magnitude, and that on sinusoidal surfaces with amplitudes much larger than the nanoscale features, spatula-shaped features can increase adhesive forces by 2.5 times on smooth surfaces and 10 times on rough surfaces. Interestingly, the summation of the fibres acting in concert shows behaviour much more complex that what could be predicted with the pulloff model of a single fibre. Both the Johnson-Kendall-Roberts and Kendall peel models can explain the experimentally observed frictional adhesion effect previously described in the literature. Similar to experimental results recently reported on the macroscale features of the gecko adhesive system, adhesion drops dramatically when surface roughness exceeds the size and spacing of the adhesive fibrillar features.

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Orientation angle and the adhesion of single gecko setae

Cited by 21 publications

References 47 publications

Gecko toe and lamellar shear adhesion on macroscopic, engineered rough surfaces

Gecko toe and lamellar shear adhesion on macroscopic, engineered rough surfaces

The effect of surface water and wetting on gecko adhesion

Simulation of synthetic gecko arrays shearing on rough surfaces

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