Emergence of macroscopic directional motion of deformable active cells in confined structures
       Bao-quan Ai ,1,2,* Jian Ma,1 Chun-hua Zeng,3,† and Ya-feng He4,‡
1Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials,
School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China
2Guangdong-Hong Kong Joint Laboratory of Quantum Matter, South China Normal University, Guangzhou 510006, China
3Faculty of Science, Kunming University of Science and Technology, Kunming 650500, China
4College of Physics Science and Technology, Hebei University, Baoding 071002, China
(Received 7 November 2022; accepted 31 January 2023; published 10 February 2023)

There is now growing evidence of collective turbulentlike motion of cells in dense tissues. However, how
to control and harness this collective motion is an open question. We investigate the transport of deformable
active cells in a periodically asymmetric channel by using a phase-field model. We demonstrate that collective
turbulent-like motion of cells can power and steer the macroscopic directional motion through the ratchet
channel. The active intercellular forces proportional to the deformation of cells can break thermodynamical
equilibrium and induce the directional motion. This directional motion is caused by the ratchet effect rather
than the spontaneous symmetry breaking. The motion direction is determined by the asymmetry of the channel.
Remarkably, there exits an optimal nonequilibrium driving (depending on the active strength, the elasticity, and
the packing fraction) at which the average velocity reaches the maximum. In addition, the optimized packing
fraction and the optimized minimum width of the channel can facilitate the directional motion of cells. Our
findings are relevant to understanding how macroscopic directional motion relates to the local force transmission
mediated by cell-cell contacts in cellular monolayers.

DOI: 10.1103/PhysRevE.107.024406