Insects are skilful climbers and are a good example of adhesion in biological systems. They manage to strongly attach to surfaces - even upside down, during a storm or a heatwave -  but also rapidly detach from them when escaping from predators.

What is the secret of this reversible attachment & can it be mimicked in human-made systems?

We zoom into the insects' adhesive devices, their footpads, and study their interaction with smooth surfaces that cannot be aided by the insect's claws. This interfacial system is comprised of a soft, viscoelastic footpad, a stiff surface of known properties and a liquid secreted from the pad that mediates the contact.

While the existence of the secretion has been known for ~200 years and its chemical composition - an emulsion of long chain hydrocarbons in water - has also been described in literature, its functional role remains elusive. This is mostly due to the minuscule volume of the secretion (10^-13 L) that makes it challenging to quantify even simple physical properties, such as its surface tension and viscosity.

Together with students & collaborators, I have worked to develop an experimental approach of quantifying the physical properties of the secretion in situ and have addressed the following questions:

1. Is the secretion responsible for the sustained attachment of insects that grow by multiple orders of magnitude in mass?
2. How do the secretion's properties change with temperature & how does that affect attachment?
3. How does surface wettability influence attachment & what is the implication for theoretical models used in literature?

References:

Kaimaki D-M, Andrew CNS, Attipoe AEL and Labonte D. 2022 The physical properties of the stick insect pad secretion are independent of body size J. R. Soc. Interface.19:20220212. (doi:10.1098/rsif.2022.0212)