Bio-Inspired capillary capture of viscous fluids with soft structures.
Capturing fluids at small scales is a challenge that nectarivores have solved by developing various type of specialized tongues, which consist of a complex assembly of flexible structures of small size compared to the capillary length. Most of the physicochemical mechanisms allowing some of those animals to quickly feed on nectar are not yet fully understood. This project aims to understand the physical mechanisms underlying the efficient capture of nectar by bees and hummingbirds which results from the dynamical coupling between viscous flows, capillary forces and elasticity in hierarchical soft tongues. 
To achieve this objective, model experiments are proposed. Mimicking hummingbirds’ tongues, I will first characterise the static closing of soft open tubes in contact with a specific amount of liquid. I will then study the dynamics when the same structure is dipped and removed from a fluid bath. In a second step, I will study the equilibrium shape and the dynamics of soft brushes and hairy surfaces dipped into a fluid bath, mimicking bumblebee’s tongue. The study of these systems will allow us to develop general physical models. The relevance of these models for describing the biological systems will be assessed by the direct comparison between the theoretical predictions and in-vivo measurements by setting the control parameters of the model systems to values compatible with the biological systems. This project will thus provide general models for the capture of viscous fluid through elastocapillary effects in some geometries inspired by biological systems.
Based on the insights gained from these model experiments and the comparison with in-vivo data, optimal soft structures will be designed to passively capture precise amount of viscous fluids at a controlled rate. The BioCapSoft project will thus contribute to a better understanding of the dynamical coupling between viscous flows, capillary forces and elasticity in soft impregnated structures.