Activity: Talk or presentation › Oral presentation › Academic
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.