Molecular Dynamics study of the hydrodynamics in a polymeric slit pore with graphitic wall coating*

Lab-On-a-Chip units are often designed to transport water solutions through nanopores. High resolution separations of solvated species and reduction of flow resistance are required in such systems encouraging the design of more efficient nanomembranes. Recently, scalable techniques to deposit graphene coatings on polymeric substrates have been developed. In this work, we propose to achieve drag reduction in polymeric nanochannels by using 2D graphitic materials as wall coating. Atomistic simulations are conducted to study water flow through polyamide nanoslits coated with layers of graphene and graphene oxide. We perform a detailed characterization of the effects that the polymeric matrix has on water transport through the nanoslits. The force fields describing interactions between the polyamide, graphene layers and water were calibrated by reproducing experimental contact angles. From the simulations, we extract density and velocity profiles, shear stress and orientation of water molecules at interfaces. The relation between fluid structure, flow enhancement and slip lengths is examined. Data are then used to evaluate drag reduction capabilities of graphitic coatings in polymeric nanochannels.