The article Pure hydrodynamic instabilities in active jets of puller microalgae by Isabelle Eisenmann, published during her PhD at LPENS under the supervision of Nicolas Desprat and Raphaël Jeanneret, has just been selected as one of the best articles of the year 2025 in the journal Physical Review Letters. Congratulations to them!
In this study, light is used to precisely control the movement of phototactic microalgae, organizing them into a “jet” and destabilizing it into droplets or zig-zag patterns. The two types of structures develop depending on the microalgae’s preferential orientation relative to the jet axis: if the algae swim parallel to the jet, it destabilizes into droplets, whereas if they swim perpendicular to the jet, it destabilizes into a zig-zag pattern. By combining analytical and numerical approaches with collaborators at the University of Cambridge and Tohoku University, it was demonstrated that these phenomena can be fully explained by considering only the hydrodynamic interactions between the microalgae.
Droplet (left) and zig-zag instabilities in jets of puller active particles.