Elastic behaviour of dock beetle adhesive structures

The adhesion of many insects is mediated by liquid capillary bridges formed at the tips of multiple hair like structures (called setae) under their feet. Resulting adhesion forces can exceed a hundred times the insect’s body weight and they are effective on a large variety of substrates, controllable in very short times and self cleaning.
The underlying mechanism leading to these properties involves a complex coupling between the high aspect-ratio structures and the dynamic evolution of the liquid meniscus. In this experimental work, we concentrate on the role played by the compliance of seta tips. We analyse in detail their surface contact and deflection for perpendicular loading using interference microscopy. Challenges related to the micrometric scale of the phenomenon and the tiny amount of liquid are addressed. The results are rationalized through the lens of elasto-capillarity theory.