Ratchet transport powered by chiral active particles.

Bao-Quan Ai

doi:10.1038/srep18740

Abstract

We numerically investigate the ratchet transport of mixtures of active and passive particles in a transversal asymmetric channel. A big passive particle is immersed in a ‘sea’ of active particles. Due to the chirality of active particles, the longitudinal directed transport is induced by the transversal asymmetry. For the active particles, the chirality completely determines the direction of the ratchet transport, the counterclockwise and clockwise particles move to the opposite directions and can be separated. However, for the passive particle, the transport behavior becomes complicated, the direction is determined by competitions among the chirality, the self-propulsion speed, and the packing fraction. Interestingly, within certain parameters, the passive particle moves to the left, while active particles move to the right. In addition, there exist optimal parameters (the chirality, the height of the barrier, the self-propulsion speed and the packing fraction) at which the rectified efficiency takes its maximal value. Our findings could be used for the experimental pursuit of the ratchet transport powered by chiral active particles.

Highlights

Ratchet effects have been observed in the absence of an external drive for systems of self-propelled particles[5]
For very small values of Ω (e.g. Ω = 0.01), the passive and active particles move to the opposite directions
A big passive particle was immersed in the ‘sea’ of active particles

Summary

Model and Methods

)of its active center and the orientation θi particles and ai = ap for the of the polar axis n i ≡ passive particle). With μ the mobility and vi[0] the self-propulsion The translational and rotational noise terms, lations 〈ξiαT (t)ξjTβ (s)〉 = δijδαβδ (t − s) (α, β speed ξiT (t) labels (vi0 = v0 for active particles and vi0 = 0 for the passive particle). We define the ratio between the area occupied by particles and the total available area as the packing fraction ( ) φ. The other parameters h^in=theah0a.bForvoemeqnuoawtioonns, .we can will be rewritten as ^v0

Dθ μk

Results and Discussion

Concluding remarks

Additional Information