Cross-Stream Migration of Flexible Molecules in a Nanochannel

Molecular dynamics simulations are used to examine the cross-stream chain migration phenomenon in dilute polymer solutions that are flowing in nanochannels. In particular, both uniform planar shear (Couette) and pressure driven (Poiseuille) flows of a dilute polymer solution are studied using a bead-spring representation of polymer chains and a coarse grained model for the solvent. Our results show that three mechanisms govern the migration of deformable molecules in a nanochannel: (1) chain-wall hydrodynamic interactions, (2) thermal diffusion, and (3) gradient in chain mobility. These results are discussed in the context of recent experimental, numerical and theoretical work.