上海科技大学知识管理系统

Understanding the propulsion of a swimmer in a large group of individuals holds the
key to unraveling the intriguing dynamics of active matter collective motion. Here, we
develop a 2D self-assembled rotor, powered by bacterial flagella. At a water-air interface,
the average direction of rotation of a rotor is fixed. When the chiral rotor is put into a 2D
bacterial suspension, we examine the average and fluctuation of the angular velocity of
the rotor. Remarkably, the average angular velocity of a rotor is found to increase up to
3 times when the density of surrounding bacterial suspension increases and the increase
is nonlinear. In a dense suspension of bacteria, the existence of a rotor disrupts vortices
in surrounding active turbulence, and the acceleration of the rotor is independent of the
activity level of the surrounding free bacteria. The nonlinear acceleration thus results
from hydrodynamic interaction with surrounding crowdedness that can be quantitatively
explained by hydrodynamic simulation. The simultaneity between the acceleration of
rotor and free bacteria in active turbulence suggests that crowding-induced acceleration
may promote the onset of instability. The result will inspire new active-matter-based
microfluidic devices with improved transport properties.