Fig. 1: Hydrodynamic pair interactions.
From: Simultaneous emergence of active turbulence and odd viscosity in a colloidal chiral active system
a–d Trajectories of two interacting colloidal rotors at various separations, with lines colour coding time evolution, and scale bars 2 μm in experiments and 2σ in simulations (see Supplementary Movie 1); a and b experimental trajectories for a duration of Ωt = 30, where t = 3 s, c and d simulated trajectories with Ωt = 5, with background points illustrating solvent positions. e Flow field of two colloids placed at a fixed distance, as calculated from hydrodynamic simulations. All simulation data is time-averaged over tav steps and a number nav of realizations. For averages of the fluid, there are δav = 10 MPC collisions in between each measuring step, and here tav = 3 × 105 and nav = 54. f Co-rotation angular velocity Ωpair as a function of the separation of the two rotors: red, experimental results; blue, simulations. For averages of the colloids δav = 103, and here with tav = 3 × 104 and nav = 240. The dashed line is the theoretical prediction Ωpair/Ω = σ2/(2r2). g Forces perpendicular to the line connecting two rotors in units of Fs = 4π2ησΩ. The dashed-dotted line is the analytical prediction from the Stokes equation in ref. 42, blue squares correspond to the explicitly measured forces in simulations, and circles are estimates obtained from the angular velocity in f via F⊥ = (kBT/D)πσΩ, with up to tav = 6 × 106 and nav = 108 for the largest separations.
