When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs

Crawford, N., Endlein, T., Pham, J. T., Riehle, M. and Barnes, W. J. P. (2016) When the going gets rough – studying the effect of surface roughness on the adhesive abilities of tree frogs. Beilstein Journal of Nanotechnology, 7, pp. 2116-2131. (doi: 10.3762/bjnano.7.201) (PMID:28144558) (PMCID:PMC5238669)

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Abstract

Tree frogs need to adhere to surfaces of various roughnesses in their natural habitats; these include bark, leaves and rocks. Rough surfaces can alter the effectiveness of their toe pads, due to factors such as a change of real contact area and abrasion of the pad epithelium. Here, we tested the effect of surface roughness on the attachment abilities of the tree frog Litoria caerulea. This was done by testing shear and adhesive forces on artificial surfaces with controlled roughness, both on single toe pads and whole animal scales. It was shown that frogs can stick 2–3 times better on small scale roughnesses (3–6 µm asperities), producing higher adhesive and frictional forces, but relatively poorly on the larger scale roughnesses tested (58.5–562.5 µm asperities). Our experiments suggested that, on such surfaces, the pads secrete insufficient fluid to fill the space under the pad, leaving air pockets that would significantly reduce the Laplace pressure component of capillarity. Therefore, we measured how well the adhesive toe pad would conform to spherical asperities of known sizes using interference reflection microscopy. Based on experiments where the conformation of the pad to individual asperities was examined microscopically, our calculations indicate that the pad epithelium has a low elastic modulus, making it highly deformable.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Endlein, Dr Thomas and Riehle, Dr Mathis and Barnes, Dr W.Jon.P
Authors: Crawford, N., Endlein, T., Pham, J. T., Riehle, M., and Barnes, W. J. P.
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Beilstein Journal of Nanotechnology
Publisher:Beilstein-Institut
ISSN:2190-4286
ISSN (Online):2190-4286
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Beilstein Journal of Nanotechnology 7: 2116-2131
Publisher Policy:Reproduced under a Creative Commons License

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