Forced translocation of a polymer: Dynamical scaling versus molecular dynamics simulation

Area of Science:

• Soft Matter Physics
• Polymer Physics
• Nanotechnology

Background:

• Polymer translocation through nanopores is crucial for biological processes and nanotechnology applications.
• Understanding the dynamics of force-induced translocation is essential for controlling and optimizing these processes.
• Previous models often simplify the complex interplay of forces acting on the polymer chain.

Purpose of the Study:

• To develop a theoretical framework for describing the force-induced translocation of a polymer through a nanopore.
• To investigate the influence of driving force strength on polymer motion regimes and translocation dynamics.
• To derive scaling laws for translocation time and compare theoretical predictions with simulation data.

Main Methods:

• Theoretical modeling based on the tensile (Pincus) blob picture and a propagating tensile force front.
• Derivation of an equation of motion for the tensile front position under quasistatic approximation.
• Validation of theoretical predictions using molecular-dynamics simulations.

Main Results:

• Identified distinct polymer motion regimes (e.g., trumpet, stem-trumpet) dependent on driving force strength.
• Derived scaling laws for average translocation time, showing a transition with increasing dimensionless force.
• Molecular dynamics simulations confirmed that the translocation scaling exponent increases with pulling force, though systematically lower than theoretical values.

Conclusions:

• The theoretical model provides a robust description of force-induced polymer translocation dynamics.
• The study highlights the significant impact of driving force on translocation scaling laws.
• Discrepancies between theory and simulation suggest the role of fluctuations neglected in the quasistatic approximation.