Inertial migration of polymer micelles in a square microchannel

Abstract

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.