  Designing protocols to dynamically direct the self-assembly of colloidal
particles has become an important direction in soft matter physics because of
the promising applications in fabrication of dynamic responsive functional
materials. Here using computer simulations, we found that in the mixture of
passive colloids and eccentric self-propelled active particles, when the
eccentricity and self-propulsion of active particles are high enough, the
eccentric active particles can push passive colloids to form a large dense
dynamic cluster, and the system undergoes a novel dynamic demixing transition.
Our simulations show that the dynamic demixing occurs when the eccentric active
particles move much faster than the passive particles such that the dynamic
trajectories of different active particles can overlap with each other while
passive particles are depleted from the dynamic trajectories of active
particles. Our results suggest that this is in analogy to the entropy driven
demixing in colloid-polymer mixtures, in which polymer random coils can overlap
with each other while deplete the colloids. More interestingly, we find that by
fixing the passive colloid composition at certain value, with increasing the
density, the system undergoes an intriguing re-entrant mixing, and the demixing
only occurs within certain intermediate density range. This suggests a new way
of designing active matter to drive the self-assembly of passive colloids and
fabricate dynamic responsive materials.
