Polarization of active particles under asymmetrical boundaries

In this paper, we use the non-equilibrium molecular dynamics method to investigate the polarization effect of dumbbell-shaped active particles. It is reported that the asymmetric boundary can induce the polarization of active dumbbell-shaped molecules. In contrast to the previous research, the polarization is independent of both the temperature gradient and the concentration gradient. The analytical and numerical results also suggested that the polarization is attributed to the difference in the interaction between particles and the left or right boundaries. Additionally, the strength of the polarization depends on the active force as well as the concentration. According to the linear response theory, both temperature and concentration gradients are considered thermodynamic forces. The asymmetric interaction between the system and its boundaries can also generate a thermodynamic force. Therefore, it is proposed that there exists a thermodynamic force within the system, which is the most fundamental cause of polarization.