Flow-induced polymer translocation through a nanopore from a confining nanotube

Inertial migration of polymer micelles in a square microchannel

Using a hybrid simulation approach that combines a lattice-Boltzmann method for fluid flow and a molecular dynamics model for polymers, we investigate the inertial migration of star-like and crew-cut polymer micelles in a square microchannel. It is found that they exhibit two types of equilibrium positions, which shift further away from the center of the microchannel when the Reynolds number (Re) increases, as can be observed for soft particles. What differs from the behaviors of soft particles is that here, the blockage ratio is no longer the decisive factor. When the sizes are the same, the star-like micelles are always relatively closer to the microchannel wall as they gradually transition from spherical to disc-like with the increase of Re. In comparison, the crew-cut micelles are only transformed into an ellipsoid. Conversely, when the hydrophobic core sizes are the same, the equilibrium position of the star-like micelles becomes closer to that of the crew-cut micelles. Our results demonstrate that for polymer micelles with a core-shell structure, the equilibrium position is no longer solely determined by their overall dimensions but depends on the core and shell's specific dimensions, especially the hydrophobic core size. This finding opens up a new approach for achieving the separation of micelles in inertial migration.

Flow-Driven Translocation of a Diblock Copolymer through a Nanopore

Using a hybrid molecular dynamic and lattice Boltzmann simulation method, we investigate the flow-driven translocation of a diblock copolymer which is composed of a hydrophilic block and a hydrophobic block through a nanopore. Our results illustrate the nontrivial translocation dynamics of diblock copolymers. We find that the increase in the number of hydrophobic segments requires a larger critical flow rate and a reduced translocation time, which implies that the separation of diblock copolymers with different fractions of hydrophobic segments can be achieved by adjusting the flow rate. Our work deepens the understanding of copolymer translocation through a nanopore and provides an insight into designing related microscaled separation devices.

Flow-Induced Translocation of Star Polymers through a Nanopore

The flow-induced translocation of star polymers through a cylindrical nanopore has been studied using dissipative particle dynamics (DPD) simulations. The number of arms, f, was varied with the total number of monomers, N, kept constant. The effect of simulating the capture of the polymer into the pore upon the mean translocation time, <τ_t>, has been investigated by varying the chain's initial location. The results indicate that the incorporation of the capture process results in a reduction of <τ_t> by up to 15%. This is because the chain's initial location affects the extent of its stretching along the flow direction during translocation. <τ_t> exhibits nonmonotonic variation with f, in agreement with recently reported results for electric field-driven translocation of star polymers. Its value is larger and shows greater variation with f when the solvent quality is better. For the same value of f, the capture occurs faster in a good solvent. In addition, <τ_t> is greater for a semiflexible chain than its flexible counterpart as the time required for the branch point to enter the nanopore is longer in the former case.

Flow-induced polymer separation through a nanopore: effects of solvent quality

Using a hybrid simulation method that combines a lattice-Boltzmann approach for the flow and a molecular dynamics model for the polymer, we investigated the effect of solvent quality on the flow-induced polymer translocation through a nanopore. We demonstrate the nontrivial dependence of the translocation dynamics of polymers on the solvent quality, i.e., the enhancement in the polymer insolubility increases the critical velocity flux and shortens the translocation time. Accordingly, we propose a new strategy to separate polymers with different solubilities via their translocations in the nanopore by adjusting the velocity flux of the flow, which appears to be promising for the design of micro-scaled polymer separation devices.

Effects of nanopore size on the flow-induced star polymer translocation

We study the effects of the nanopore size on the flow-induced capture of the star polymer by a nanopore and the afterward translocation, using a hybrid simulation method that couples point particles into a fluctuating lattice-Boltzmann fluid. Our simulation demonstrates that the optimal forward arm number decreases slowly with the increase of the length of the nanopore. Compared to the minor effect of the length of the nanopore, the optimal forward arm number obviously increases with the increase of the width of the nanopore, which can clarify the current controversial issue for the optimal forward arm number between the theory and experiments. In addition, our results indicate that the critical velocity flux of the star polymer is independent of the nanopore size. Our work bridges the experimental results and the theoretical understanding, which can provide comprehensive insights for the characterization and the purification of the star polymers.