Effects of Digit Orientation on Gecko Adhesive Force Capacity: Synthetic and Behavioral Studies.

In this study we developed an analytical relationship between adhesive digit orientation and adhesive force capacity to describe the tendencies of climbing organisms that use adhesion for climbing to align their toes in the direction of loading, maximizing adhesive force capacity. We fabricated a multi-component adhesive device with multiple contact surfaces, or digits, to act as a model system mimicking the angular motion of a foot and found the synthetic experiments agree with the developed analytical relationship. In turn, we find that observations of gekkonid lizards climbing on vertical substrates correlate well with our analytical relationship; a reduction in toe spacing is seen on the forelimbs when the animals are facing up. Interestingly, the toes on the hindlimbs tend to have an increase in spacing, possibly a mechanism for stabilization rather than load-bearing.

[1]  Robert N. Fisher,et al.  A comparative analysis of clinging ability among pad‐bearing lizards , 1996 .

[2]  R. Full,et al.  Adhesive force of a single gecko foot-hair , 2000, Nature.

[3]  Eduard Arzt,et al.  Hierarchical Gecko‐Like Adhesives , 2009 .

[4]  Marleen Kamperman,et al.  Functional Adhesive Surfaces with “Gecko” Effect: The Concept of Contact Splitting , 2010 .

[5]  D. Bramble,et al.  Functional vertebrate morphology , 1985 .

[6]  Kevin W Eliceiri,et al.  NIH Image to ImageJ: 25 years of image analysis , 2012, Nature Methods.

[7]  Daniel R. King,et al.  Optimizing Adhesive Design by Understanding Compliance. , 2015, ACS applied materials & interfaces.

[8]  Duncan J. Irschick,et al.  Looking Beyond Fibrillar Features to Scale Gecko‐Like Adhesion , 2012, Advanced materials.

[9]  Daniel R. King,et al.  Creating Gecko‐Like Adhesives for “Real World” Surfaces , 2014, Advanced materials.

[10]  Alfred J. Crosby,et al.  Designing Bio‐Inspired Adhesives for Shear Loading: From Simple Structures to Complex Patterns , 2012 .

[11]  Lei Ren,et al.  Biomechanics of gecko locomotion: the patterns of reaction forces on inverted, vertical and horizontal substrates , 2015, Bioinspiration & biomimetics.

[12]  Chung-Yuen Hui,et al.  Biologically inspired crack trapping for enhanced adhesion , 2007, Proceedings of the National Academy of Sciences.

[13]  A. Bauer,et al.  Morphological correlates of the secondarily symmetrical pes of gekkotan lizards , 1997 .

[14]  A. Russell,et al.  Limb and digit orientation during vertical clinging in Bibron's gecko, Chondrodactylus bibronii (A. Smith, 1846) and its bearing on the adhesive capabilities of geckos , 2016 .

[15]  A. Zuur,et al.  Mixed Effects Modelling for Nested Data , 2009 .

[16]  R. Full,et al.  Dynamics of geckos running vertically , 2006, Journal of Experimental Biology.

[17]  S. Gorb,et al.  Biomimetic mushroom-shaped fibrillar adhesive microstructure , 2007, Journal of The Royal Society Interface.

[18]  Bieke Vanhooydonck,et al.  Whole-organism studies of adhesion in pad-bearing lizards: creative evolutionary solutions to functional problems , 2006, Journal of Comparative Physiology A.

[19]  A. Russell.  Integrative Functional Morphology of the Gekkotan Adhesive System (Reptilia: Gekkota)1 , 2002, Integrative and comparative biology.

[20]  M. Barquins.  Influence of the stiffness of testing machines on the adherence of elastomers , 1983 .

[21]  K. Shull.  Contact mechanics and the adhesion of soft solids , 2002 .

[22]  Michael D. Bartlett,et al.  High Capacity, Easy Release Adhesives From Renewable Materials , 2014, Advanced materials.

[23]  Alyssa Y Stark,et al.  Run don't walk: locomotor performance of geckos on wet substrates , 2015, The Journal of Experimental Biology.

[24]  A. Russell.  A contribution to the functional analysis of the foot of the Tokay, Gekko gecko (Reptilia: Gekkonidae) , 1975 .

[25]  Kahp Y. Suh,et al.  Stooped Nanohairs: Geometry‐Controllable, Unidirectional, Reversible, and Robust Gecko‐like Dry Adhesive , 2009 .

[26]  Eduard Arzt,et al.  Design parameters and current fabrication approaches for developing bioinspired dry adhesives. , 2007, Macromolecular bioscience.

[27]  A. Russell,et al.  The morphological basis of weight-bearing in the scansors of the tokay gecko (Reptilia: Sauria) , 1986 .

[28]  Aleksandra V. Birn-Jeffery,et al.  Geckos significantly alter foot orientation to facilitate adhesion during downhill locomotion , 2014, Biology Letters.

[29]  Duncan J. Irschick,et al.  Evolutionary correlations among morphology, habitat use and clinging performance in Caribbean Anolis lizards , 2004 .

[30]  A. Russell,et al.  Ontogenetic scaling of scansorial surface area and setal dimensions of Chondrodactylus bibronii (Gekkota: Gekkonidae): testing predictions derived from cross‐species comparisons of gekkotans , 2009 .

[31]  T. Higham,et al.  Geckos decouple fore- and hind limb kinematics in response to changes in incline , 2016, Frontiers in Zoology.

[32]  S. Gorb,et al.  From micro to nano contacts in biological attachment devices , 2003, Proceedings of the National Academy of Sciences of the United States of America.

[33]  F. Azarmi,et al.  Compliance switching for adhesion control , 2015 .

[34]  Duncan J. Irschick,et al.  Geckos as Springs: Mechanics Explain Across-Species Scaling of Adhesion , 2015, PloS one.

[35]  Timothy E Higham,et al.  Adaptive simplification and the evolution of gecko locomotion: Morphological and biomechanical consequences of losing adhesion , 2014, Proceedings of the National Academy of Sciences.

[36]  A. Bauer,et al.  Repeated Origin and Loss of Adhesive Toepads in Geckos , 2012, PloS one.