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