Metasoft 2025 - Gelling non-Newtonian drops impacting on liquids

Project leader : Anselmo PEREIRA and et Loren JØRGENSEN

Schools involved : ESPCI Paris - PSL et Mines Paris - PSL

Project summary :

The impact of non-Newtonian drops (polymer solutions, suspensions, emulsions etc.) on a chemically reactive Newtonian liquid inducing drop gelation is a challenging and scarcely explored topic in Soft Matter related to critical situations, such as ceramic beads and non-spherical particle production and encapsulation processes. Typically, a falling millimetric polymer-based elasto-viscoplastic drop passes through a liquid-air interface and forms an air cavity. The cavity then retracts due to pressure and surface tension effects while the drop penetrates the liquid containing reactive compounds. The latter diffuses inside the drop, giving rise to a gelled elastic membrane (shell) in the outer part of the impacting object. These compounds ultimately turn the drop into a strong gel. Hence, during the penetration, the drop undergoes both chemical-induced solidification (gelation) and deformation (impact/penetration), which leads to different final solid-like shapes: pears, hats, bowls, capsules etc. Nevertheless, since elasto-viscoplastic fluids present an extremely rich rheological behaviour, and the gelation kinetics are poorly understood, the mentioned final shapes are difficult to predict and control. This project seeks to highlight the physical mechanisms driving the impact of elasto-viscoplastic drops on a reactive liquid containing gelling agents. More specifically, the physical link between the hydrodynamic drop-liquid interactions, the gelation effects on the rheological properties of the drops, and their final solid-like shapes will be studied through experiments and numerical simulations for idealised setups and materials, allowing for developing and implementing a new rheological constitute model coupling elasto-viscoplasticy to gelation.