Meeting Abstract

23.2  Monday, Jan. 5  comparison of attachment performance in the hairy and smooth adhesive pads of insects BULLOCK, J.M.R.*; FEDERLE, W.; University of Cambridge; University of Cambridge jmrb3@cam.ac.uk

Despite a strong interest in biomimetic adhesives, the biomechanics of natural adhesive systems are still poorly characterised. Many insects can cling to surfaces via thin films of secreted fluid and can dynamically control adhesion during locomotion; however they achieve this using two fundamentally different designs. While smooth pads possess a very soft cuticle to allow close surface contact, ‘hairy’ adhesives compensate surface roughness with arrays of fine micro-metre sized hairs. The hairy design is thought to offer a number of functional advantages over smooth systems, but no study has yet directly compared their performance. As such we used a 2-D strain gauge to record the adhesion and friction forces of single tarsal pads of beetles and stick insects, whilst simultaneously recording contact area. Sliding experiments showed that forces strongly increased with decreasing amounts of fluid secretion in both systems. Shear stresses were also strikingly similar between hairy and smooth pads and strong dependence on direction was observed. Hairs readily detached when moved distally (against their natural angled orientation) and in both systems tarsal buckling caused peeling and loss of contact. This directional dependence of forces is achieved both at the level of the whole tarsus and for hairy systems, at the level of the single hairs.