Study of Active Brownian Particle Diffusion in Polymer Solutions (1801.03279v1)

Abstract: The diffusion behavior of an active Brownian particle (ABP) in polymer solutions is studied using Langevin dynamics simulations. We find that the long time diffusion coefficient $D$ can show a non-monotonic dependence on the particle size $R$ if the active force $F_{a}$ is large enough, wherein a bigger particle would diffuse faster than a smaller one which is quite counterintuitive. By analyzing the short time dynamics in comparison to the passive one, we find that such non-trivial dependence results from the competition between persistence motion of the ABP and the length-scale dependent effective viscosity that the particle experienced in the polymer solution. \textcolor{black}{We have also introduced an effective viscosity $\eta_{\text{eff}}$ experienced by the ABP phenomenologically. Such an active $\eta_{\text{eff}}$ is found to be larger than a passive one and strongly depends on $R$ and $F_{a}$}\textcolor{magenta}{.} In addition, we find that the dependence of $D$ on propelling force $F_{a}$ presents a well scaling form at a fixed $R$ and the scaling factor changes non-monotonically with $R$. Such results demonstrate that active issue plays rather subtle roles on the diffusion of nano-particle in complex solutions.