Forced translocation of a polymer: Dynamical scaling versus molecular dynamics simulation.
We suggest a theoretical description of the force-induced translocation dynamics of a polymer chain through a nanopore. Our consideration is based on the tensile (Pincus) blob picture of a pulled chain and the notion of a propagating front of tensile force along the chain backbone, suggested by Sakaue [Phys. Rev. E 76, 021803 (2007); Phys. Rev. E 81, 041808 (2010); Eur. Phys. J. E 34, 135 (2011)]. The driving force is associated with a chemical potential gradient that acts on each chain segment inside the pore. Depending on its strength, different regimes of polymer motion (named after the typical chain conformation: trumpet, stem-trumpet, etc.) occur. Assuming that the local driving and drag forces are equal (i.e., in a quasistatic approximation), we derive an equation of motion for the tensile front position X(t). We show that the scaling law for the average translocation time 〈τ〉 changes from <τ> ∼ N2ν/f1/ν to <τ> ∼ N^1+ν/f (for the free-draining case) as the dimensionless force f[over ̃]R=aNνf/T (where a, N, ν, f, and T are the Kuhn segment length, the chain length, the Flory exponent, the driving force, and the temperature, respectively) increases. These and other predictions are tested by molecular-dynamics simulation. Data from our computer experiment indicate indeed that the translocation scaling exponent α grows with the pulling force f[over ̃]R, albeit the observed exponent α stays systematically smaller than the theoretically predicted value. This might be associated with fluctuations that are neglected in the quasistatic approximation.
Delft Institute of Applied Mathematics, 2628CD Delft, The Netherlands.
J L A
JL
Dubbeldam
V G
VG
Rostiashvili
A
A
Milchev
T A
TA
Vilgis
D003198:Computer Simulation; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D008958:Models, Molecular; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D013314:Stress, Mechanical
D011108:Polymers