Simulation on the translocation of polymer through compound channels

Simulation study on the migration of diblock copolymers in periodically patterned slits

The forced migration of diblock copolymers (A_NAB_NB) in periodically patterned slits was investigated by using Langevin dynamics simulation. The lower surface of the slit consists of stripe α and stripe β distributed in alternating sequence, while the upper one is formed only by stripe β. The interaction between block A and stripe α is strongly attractive, while all other interactions are purely repulsive. Simulation results show that the migration of the diblock copolymer is remarkably dependent on the driving force and there is a transition region at moderate driving force. The transition driving force f_t, where the transition region occurs, decreases monotonously with increasing length of block B (N_B) but is independent of the polymer length and the periodic length of the slit, which is interpreted from the free energy landscape of diblock copolymer migration. The results also show that periodic slits could be used to separate diblock polymers with different N_B by tuning the external driving force.

Simulation on the translocation of homopolymers through sandwich-like compound channels

The forced translocation of homopolymers through αβα sandwich-like compound channels was investigated by Monte Carlo simulation. The interaction between polymer and part α is strongly attractive, whereas that between polymer and part β is purely repulsive. Simulation results show that the translocation is influenced obviously by the length of part β (Lβ) and the starting position of part β (Lα1). For small Lβ, the translocation is mainly governed by the escaping process, and polymer is trapped near the exit of the channel. However, the translocation time can be tuned by varying Lα1 and the fastest translocation can be achieved at relatively large Lα1. Whereas for large Lβ and small Lα1, the translocation is mainly controlled by the filling process. It is difficult for polymer to enter the channel, and polymer is trapped at the first αβ interface. Finally, the dynamics for the filling process and the escaping process are discussed from the view of free-energy landscape, respectively.

Driven polymer transport through a periodically patterned channel

We study the driven transport of polymers in a periodically patterned channel using Langevin dynamics simulations in two dimensions. The channel walls are patterned with periodically alternating patches of attractive and non-attractive particles that act as trapping sites for the polymer. We find that the system shows rich dynamical behavior, observing giant diffusion, negative differential mobility, and several different transition mechanisms between the attractive patches. We also show that the channel can act as an efficient high-pass filter for polymers longer than a threshold length Nthr, which can be tuned by adjusting the length of the attractive patches and the driving force. Our findings suggest the possibility of fabricating polymer filtration devices based on patterned nanochannels.