Migration of an active particle in mixtures of rigid and flexible rings.

The migration of active particles in slowly moving, crowded, and heterogeneous media is fundamental to various biological processes and technological applications. In this study, we numerically investigate the dynamics of a single active particle in a multicomponent medium composed of mixtures of rigid and flexible rings. We observe a nonmonotonic dependence of diffusivity on the relative fraction of rigid to flexible rings, leading to the identification of an optimal composition for enhanced diffusion. This long-time nonmonotonic diffusion, resulting from the different responses of the active particle to rigid and flexible rings, is coupled with transient short-time trapping. The probability distribution of trapping durations is well described by the herein-proposed extended entropic-trap model. We further theoretically establish a universal relationship between particle activity and the optimal rigid-to-flexible ring ratio for diffusion, which aligns closely with our numerical results.