Effect of shear forces and ageing on the compliance of adhesive pads in adult cockroaches
Journal of Experimental Biology
Company of Biologists
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Zhou, Y., Robinson, A., Viney, C., & Federle, W. (2015). Effect of shear forces and ageing on the compliance of adhesive pads in adult cockroaches. Journal of Experimental Biology, 218 2775-2781. https://doi.org/10.1242/jeb.124362
The flexibility of insect adhesive pads is crucial for their ability to attach on rough surfaces. Here we use 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. The increase in stiffness is likely 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.
biomechanics, adhesion, insect cuticle, material properties, ageing, wear
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.
Human Frontier Science Program (HFSP) (RGP0034/2012)
External DOI: https://doi.org/10.1242/jeb.124362
This record's URL: https://www.repository.cam.ac.uk/handle/1810/248723