Polymer linear transport in steady convergent microfluidics

Abstract

Combining the Langevin Dynamics method and the Computational Fluid Dynamics method, under the conditions of Knudsen number K_n ≤ 10⁻¹, we investigated the dynamics of a linear polymer transported into a channel of width D = 4σ embedded in two dimensions, driven by force-mimicked steady convergent microfluidics. We have proven that a critical volume-flow rate J_c ∼ k_BT/η ∼ 1/η exists in polymer transport, independent of chain length. Once the polymer has found the pore entrance in advance, we find that linear transport time, τ, is proportional to chain length N, but inversely proportional to volume-flow rate J; otherwise, if the polymer does not find the pore entrance in advance, we find that with regard to the linear transport probability, P, the law of P ∼ N^0.25J_cexp(−k′/J) exists, where k′ is a positive constant dependent only on channel geometry, friction coefficient and the position fixing polymer head outside the channel before the transport process starts, indicating that polymer initial conformations can affect the polymer transport probability.