Frontiers and perspectives in the design of tree-frog-inspired adhesives

Langowski, J. (Speaker)

Activity: Talk or presentationOral presentationAcademic

Description

The ‘smooth’ adhesive pads of tree frogs are an important vertebrate source of inspiration for
the design of bioinspired adhesives. Numerous bioinspired adhesives mimic in particular the
hierarchical pattern of micro- to nanoscopic pillar-like structures found on the toe pads of tree
frogs. Other functionally relevant pad components, however, have barely been considered in
the design of tree-frog-inspired adhesives. In this talk, I will present recent research beyond
the surface of tree frog’s toe pads, and discuss the functional relevance and biomimetic potential of previously undescribed pad components. Using synchrotron-micro-computertomography, we identified an anisotropic network of keratinous and collagenous fibres that
connects the adhesive pad surface with the digital skeleton. Finite-element-analysis suggests
that such fibre-reinforcement strengthens the toe pad mechanically against high mechanical
loads, which arise from rapid manoeuvres such as jumping. Furthermore, tree frog toe pads
contain smooth muscle fibre bundles, which to our knowledge is unique among bioadhesive
systems. These muscular structures may provide tree frogs with pad-intrinsic control mechanisms to regulate their attachment to the substrate. A comparative analysis of the digital mucus gland morphology and mucus chemistry does not support a specialisation towards attachment. Instead, an analysis of experimental work on bioinspired adhesives indicates that interstitial liquids such as the mucus secreted by tree frogs play a role in detachment. Overall, tree
frogs are fascinating models for the design of strong adhesives with fine-tuneable control of
attachment strength that function under challenging conditions.
Period6 Jul 2020