Driven transport of fluid vesicles through narrow pores

The driven transport of fluid vesicles through narrow, cylindrical pores in a linear external potential is studied using Monte Carlo simulations, scaling arguments, and mean-field theory. The mobility of the vesicles increases sharply when the strength f of the driving field exceeds a threshold value ${\mathit{f}}^{\mathrm{*}}$. For f>${\mathit{f}}^{\mathrm{*}}$, the mobility saturates at a value that is essentially independent of the strength of the driving field. The threshold field strength ${\mathit{f}}^{\mathrm{*}}$ is found to scale with the membrane bending rigidity κ, the vesicle area ${\mathit{A}}_0$, and the pore size ${\mathit{r}}_{\mathit{p}}$ as ${\mathit{f}}^{\mathrm{*}}$/${\mathit{k}}_{\mathit{B}}$T∼ (κ/${\mathit{k}}_{\mathit{B}}$T${)}^{1+\mathrm{\beta }}$${\mathit{A}}_0^{\mathrm{-}3/2+\mathrm{\eta }}$${\mathit{r}}_{\mathit{p}}^{\mathrm{-}2\mathrm{\eta }}$. An analysis of the zero-temperature limit yields the exponents β=0 and η=1.55, while the Monte Carlo simulations of low-bending-rigidity vesicles are well described by the (effective) exponents β≃0.2 and η≃2.4.