The study conducted by Raphael Saiseau and his collaborators at the University of Bordeaux, France, focuses on the role of gravity in Ostwald ripening, a thermodynamic process responsible for various effects such as the recrystallization of ice cream. This process involves the growth of larger domains at the expense of smaller ones, driven by surface tension.
In their experiment, the researchers used a transparent pseudobinary liquid mixture to create a liquid interface that they could perturb using a laser beam. By destabilizing the interface inside a sealed container, they were able to create a liquid jet that penetrated a heavier phase below, which eventually broke down into smaller droplets. The decay rate of the droplet’s radius was then directly measured and compared with the predicted dynamics.
The presence of gravity in the experiment introduced a dependence of the droplet decay rate on height within the column. To account for this, the researchers developed a model to identify the conditions under which the effect of solute stratification on the droplet decay becomes negligible. They found that the droplet had to be small compared with the gravitational capillary length, it had to be far from criticality, and it had to be positioned close to the meniscus separating the two phases. Only when these conditions were met could the 1/3 decay exponent predicted by theory be recovered.
This study demonstrates that evaporation–condensation mechanisms can be more complex than the universal scaling laws predicted by theory, as the presence of gravity introduces additional forces competing with capillary forces and results in richer dynamics. Integrating the effect of gravitation into phase-transition dynamics is expected to bring new insights to domain-coarsening phenomena in soft matter physics and materials science.
The research was conducted by Séverine Atis, a researcher at the French National Centre for Scientific Research (CNRS). Her research interests include disordered systems, evolutionary dynamics, and out-of-equilibrium phenomena. She received her PhD from Sorbonne University, France, for her studies of universal behavior in reaction waves.
