GENNIAL

The impact of gelling non-Newtonian drops on a chemically reactive Newtonian liquid represents a fundamental and scarcely explored topic in Soft Matter Rheology 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 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, Mexican hats, bowls, capsules etc. Nevertheless, since elasto-viscoplastic fluids present an extremely rich rheological behaviour and the gelation kinetics is poorly understood, the mentioned final shapes are difficult to predict and control. Our project will be divided into two main steps. First, we will 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. To fulfil this objective, we will perform key controlled experiments and numerical simulations for idealised setups and materials, allowing for developing and implementing a new rheological constitute model coupling elasto-viscoplasticy to gelation. Secondly, the depicted physicochemical hydrodynamics will be injected into learning algorithms, targeting the control of the drop final shapes.