Role of stall forces and entropic barriers in geometry-dependent polymer translocation

We investigate the role of stall forces and entropic barriers in geometry-dependent polymer translocation through narrow pores. We consider two distinct geometrical constraints: forced translocation through a small pore in a flat membrane separating two semi-infinite three-dimensional spaces, and translocation from a confined region into an unconfined space, where the confinement is provided by a square-pyramidal geometry in three dimensions. The translocation dynamics is described within a lattice-based framework by mapping the process onto the diffusion of an effective virtual particle governed by a Fokker-Planck equation, with the underlying free-energy landscape obtained from exact enumeration of polymer configurations. This approach enables us to study the effects of external driving forces from entropic resistance arising due to geometry. Under their respective stall forces, translocation is markedly faster through a square pyramidal pore than through a flat membrane, demonstrating that confinement-induced changes in the entropic free-energy barrier can enhance driven polymer transport. Our results reveal the importance of a stall force in controlling polymer translocation, suggesting potential applications in nanopore-based manipulation, filtration, and sequencing technologies.