Tunable Memory and Activity of Quincke Particles in Micellar Fluid

Memory can remarkably modify the collective behaviors of active particles. We show that in a micellar fluid, Quincke particles driven by a square-wave electric field exhibit a frequency-dependent memory. Upon increasing the frequency, a memory of directions emerges whereas the activity of particles decreases. As the activity is dominated by interaction, Quincke particles aggregate and form dense clusters in which the memory of the direction is further enhanced due to the stronger electric interactions. The density-dependent memory and activity result in dynamic heterogeneity in flocking and offer new opportunity for study of collective motions.