Emerging patterns of phoretic active matter: from crystalline solids to active turbulence

Phoretic microswimmers, such as Janus colloids and isotropic active droplets, are promising constituents for self-organized active materials. However, the underlying mechanisms governing their self-organization remain unclear, despite numerous experimental observations in various regimes. Here, we perform large-scale simulations to investigate a paradigmatic suspension of isotropic phoretic disks representing active droplets, explicitly resolving their many-body, long-range hydrochemical interactions. We observe that they exhibit diverse collective phenomena, including the formation of crystalline solids resembling Wigner crystals, melting, gas-like chain formation, active transition and turbulence. Our work reproduces and reconciles seemingly conflicting experimental observations on chemically active systems, emphasizing the importance of incorporating full physicochemical hydrodynamics. Remarkably, altering activity alone induces solid-fluid phase transition and, subsequently, the laminar-turbulent transition of the fluid. These two progressively emerging transitions, hitherto unreported, bring us closer to understanding the parallels between active matter and traditional matter. Our findings will help enhance the understanding of long-range, many-body interactions among phoretic agents, offer new insights into non-equilibrium collective behaviors, and provide potential guidelines for designing reconfigurable materials.