Pattern formation in isothermal miscible protein-sugar systems driven by Marangoni effects and evaporation

Pattern formation is crucial for controlling fluid motion and spatiotemporal organization in living and synthetic active systems. While pattern formation in miscible fluid systems is typically driven by reaction-diffusion processes or thermal gradients, we show pattern formations in an isothermal miscible fluid system involving simple protein and sugar solutions. Upon introducing a less dense urease solution into higher density glucose or sucrose solutions, the protein initially spreads at the air-water interface, then forms spiral patterns after several minutes. The mechanism involves an interplay between Marangoni effects, evaporation, and airflow. Our work suggests that reaction-diffusion pattern formation can be replicated by replacing the reaction-induced inhomogeneous solute distribution by evaporation-induced inhomogeneity. In both cases, the fast diffusive or Marangoni spreading is counteracted by a slower step that reverses the solute homogenization. These insights enable the manipulation of fluid motion and surface morphology, with implications in coating technologies, materials science, and microfluidics. (Figure presented.)