Recently, a collaborative research paper titled "Simultaneous emergence of active turbulence and odd viscosity in a colloidal chiral active system" was published in Communications Physics (Q1; IF 6.5) by a joint team led by Prof Yongxiang Gao from Shenzhen University, Prof Gerhard Gompper and Marisol Ripoll from Forschungszentrum Jülich and Dirk Aarts from Oxford University. Prof Yongxiang Gao is the co-first author and co-corresponding author of the paper.

Though continuous energy injection and consumption at the individual scale, active fluids composed of an ensemble of self-propelling or rotating entities exhibit non-equilibrium and exotic collective phenomena. Among them, active turbulence and odd viscosity are particularly noteworthy, corresponding to spontaneous complex flow and dissipation-less transverse flow, which have been reported separately in different systems.

Here we developed a chiral active fluid composed of a carpet of standing and rotating magnetic Janus rods. Experiments and simulations reveal that multi-scale eddies emerge, a hallmark of active turbulence, with a power-law decay of the kinetic-energy spectrum, a feature of self-similar dynamics. Moreover, the particles are dragged to the center of the vortices, creating density inhomogeneity due to odd viscosity. The weak compressibility of the system enables an explicit measurement of the odd viscosity in bulk via the relation between local vorticity and excess density. Our findings are relevant for establishing the correlation between active turbulence and odd viscosity, understanding peculiar behaviors of chiral active fluids including biological systems and designing collective self-organization in micro-robotics.

This research was supported by the general program of Natural Science Foundation of China (11774237) and the general program of Natural Science Foundation of Guangdong Province (2022A1515011800).