Activity waves in binary active colloids of Quincke rollers

Activity waves are popular in excitable systems. Here, we show that binary active colloids of Quincke rollers driven by an alternating electric field can also form activity waves. In the activity waves, Quincke rollers exhibit a memory of the direction of motion. This memory occurs at frequencies much smaller than that in monodisperse systems. It is found that the enhanced memory arises from the paired distinct rollers which break the dynamic symmetry because of the configuration-dependent dipole–dipole interactions. This finding demonstrates that dipole–dipole interactions between distinct active agents can significantly modify the collective dynamics of polydisperse active systems.