Tree frog adhesion biomimetics: opportunities for the development of new, smart adhesives that adhere under wet conditions
- 10 June 2019
- journal article
- review article
- Published by The Royal Society in Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
- Vol. 377 (2150), 20190131
- https://doi.org/10.1098/rsta.2019.0131
Abstract
Enlarged adhesive toe pads on the tip of each digit allow tree frogs to climb smooth vertical and overhanging surfaces, and are effective in generating reversible adhesion under both dry and wet conditions. In this review, we discuss the complexities of the structure of tree frog toe pads in relation to their function and review their biomimetic potential. Of particular importance are the (largely) hexagonal epithelial cells surrounded by deep channels that cover the surface of each toe pad and the array of nanopillars on their surface. Fluid secreted by the pads covers the surface of each pad, so the pads adhere by wet adhesion, involving both capillarity and viscosity-dependent forces. The fabrication and testing of toe pad mimics are challenging, but valuable both for testing hypotheses concerning tree frog toe pad function and for developing toe pad mimics. Initial mimics involved the fabrication of hexagonal pillars mimicking the toe pad epithelial structure. More recent ones additionally replicate the nanostructures on their surface. Finally we describe some of the biomimetic applications that have been developed from toe pad mimics, which include both bioinspired adhesives and friction-generating devices. This article is part of the theme issue ‘Bioinspired materials and surfaces for green science and technology (part 2)’.Keywords
Funding Information
- Longjian Xue (National Key R&D Program of China (2018YFB1105100), National Natural Science Foundation of China (5150)
This publication has 78 references indexed in Scilit:
- Sticking under Wet Conditions: The Remarkable Attachment Abilities of the Torrent Frog, Staurois guttatusPLOS ONE, 2013
- Adhesion Failure at 180 000 Frames per Second: Direct Observation of the Detachment Process of a Mushroom-Shaped AdhesivePhysical Review Letters, 2013
- Insights into the Adhesive Mechanisms of Tree Frogs using Artificial MimicsAdvanced Functional Materials, 2012
- Synthesis and Self-Assembly of Perylenetetracarboxylic Diimide Derivatives with Helical Oligo(l-lactic acid)n SegmentsLangmuir, 2012
- Elastic modulus of tree frog adhesive toe padsJournal of Comparative Physiology A, 2011
- Capillarity-based switchable adhesionProceedings of the National Academy of Sciences of the United States of America, 2010
- Wet Self-Cleaning of Biologically Inspired Elastomer Mushroom Shaped Microfibrillar AdhesivesLangmuir, 2009
- Ultrastructure and physical properties of an adhesive surface, the toe pad epithelium of the tree frog, Litoria caerulea WhiteJournal of Experimental Biology, 2009
- Wet but not slippery: boundary friction in tree frog adhesive toe padsJournal of The Royal Society Interface, 2006
- Biomimetics: its practice and theoryJournal of The Royal Society Interface, 2006