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Effect of shear forces and ageing on the compliance of adhesive pads in adult cockroaches.


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Authors

Zhou, Yanmin 
Robinson, Adam 
Viney, Christine 

Abstract

The flexibility of insect adhesive pads is crucial for their ability to attach on rough surfaces. Here, we used transparent substrates with micropillars to test in adult cockroaches (Nauphoeta cinerea) whether and how the stiffness of smooth adhesive pads changes when shear forces are applied, and whether the insect's age has any influence. We found that during pulls towards the body, the pad's ability to conform to the surface microstructures was improved in comparison to a contact without shear, suggesting that shear forces make the pad more compliant. The mechanism underlying this shear-dependent increase in compliance is still unclear. The effect was not explained by viscoelastic creep, changes in normal pressure, or shear-induced pad rolling, which brings new areas of cuticle into surface contact. Adhesive pads were significantly stiffer in older cockroaches. Stiffness increased most rapidly in cockroaches aged between 2.5 and 4 months. This increase is probably based on wear and repair of the delicate adhesive cuticle. Recent wear (visualised by Methylene Blue staining) was not age dependent, whereas permanent damage (visible as brown scars) accumulated with age, reducing the pads' flexibility.

Description

Keywords

Adhesion, Biomechanics, Insect cuticle, Material properties, Surface roughness, Wear, Adhesiveness, Aging, Animals, Biomechanical Phenomena, Cockroaches, Extremities, Friction, Locomotion, Surface Properties, Video Recording

Journal Title

J Exp Biol

Conference Name

Journal ISSN

0022-0949
1477-9145

Volume Title

218

Publisher

The Company of Biologists
Sponsorship
Biotechnology and Biological Sciences Research Council (BB/E004156/1)
Biotechnology and Biological Sciences Research Council (BB/I008667/1)
Human Frontier Science Program (HFSP) (RGP0034/2012)
This study was supported by a studentship from the Cambridge Overseas Trust (to Y.Z.) and research grants from the UK Biotechnology and Biological Sciences Research Council [BB/I008667/1], the Human Frontier Science Programme [RGP0034/2012] and AkzoNobel.