Confinement-driven states and activity-induced escape of semiflexible polymers in soft traps

Abstract

We investigate the dynamics of an actively driven semiflexible polymer confined by a soft harmonic potential. Our study is inspired by in-vitro motility assays where cytoskeletal filaments are propelled by motor proteins under controlled confinement. Using coarse-grained simulations that couple polymer elasticity with stochastic motor attachment, detachment, and force generation, we obtain distinct dynamical regimes ranging from fully confined to freely escaping states, separated by a region of intermittent coexistence. The transitions between these regimes are governed by the combined effects of activity, filament stiffness, confinement strength, and motor processivity. Moderate confinement stabilizes compact spiral conformations through a balance between active forcing and bending elasticity. Stronger activity promotes escape. The motion of the center-of-mass of the polymer exhibits diffusive–ballistic–localized crossovers and oscillations characteristic of trapped chiral active Brownian particles. Our results establish a minimal physical framework for understanding how activity and geometric confinement interact to regulate the transport and morphology of active filaments.

A diagram depicting the model setup: a polymer in a harmonic trap embedded on a motor assay, followed by a time series showing three di9erent states of the system.