Microrotor of a chain-grafted colloidal disk immersed in the active bath: The impact of particle concentration, grafting density, and chain rigidity.

In an earlier work, we discussed the possibility to realize a microrotor by immersing a chain-grafted colloidal disk in a thin film of active-particle suspension. Under certain conditions, the colloidal disk rotates unidirectionally driven by the bath active particles. Here we systematically study the role of active-particle concentration, grafting density, and chain rigidity in the phenomenon of the spontaneous symmetry breaking of the chain configurations and the unidirectional rotation of the disk. We find that high chain rigidity can help stabilize both the collective asymmetric chain configurations and the rotation of the disk, while it has a weak impact on the rotational speed/efficiency. Increasing the number of grafted chains can also stabilize the rotation but has a negative impact on the rotational speed/efficiency. Active particles power the rotation of the colloidal disk, yet their contribution saturates beyond a certain concentration. Our work provides new insights into the active systems with chain-structured objects and the design of soft/deformable micromachines. [ABSTRACT FROM AUTHOR]