Emergent patterns in Snowman Quincke rollers

Quincke rollers are dielectric particles suspended in a weakly conducting liquid, activated to move under DC electric fields. Mechanism: If the conductivity of the liquid is slightly more than the particle, the particle dipole is directed opposite to that of the electric field. Any slight perturbation results in a rotation of the particle from the unstable equilibrium position. It induces a charge relaxation process on the particle to align the charge distribution with the initial configuration of the dipole. However, the higher conductivity of the fluid competes with this relaxation, effectively orienting the dipole at an angle with the field, generating a continuous rotation of the particles.

This study investigates the Quincke rolling phenomenon of snowman-shaped colloidal particles. These chiral rollers exhibit individual and collective dynamic states that depend upon the population and driving field strength. In addition to the previously identified dynamic states, such as spinning and vortex states, we identify the standing and bounded motion of the particles. The bounded motion involves the confined orbiting of particles around the center of mass due to hydrodynamic interactions at low particle area fractions. Our findings provide valuable insights into the behavior of active systems and the fabrication of active materials, emphasizing emergent order and adaptability as key guiding principles.