Abstract
Understanding of the diffusio-osmosis, the flow induced by a solute gradient acting in narrow interfacial layers at nanoscale solid-liquid interface, is of great value in view of the increasing importance of micro- and nano-fluidic devices and self-propelling particle. Here, using molecular dynamics simulations, we develop a numerical method for direct simulation of diffusio-osmosis flows mimicking the realistic experiment without any assumed external forces. It allows us to obtain reliable flow details which is however hard to get in experiments. We found that the solvent-wall interaction, previously overlooked in classical paradigm, plays a critical role in diffusio-osmosis process. In particular, diffusio-osmosis is controlled by the interaction difference between solute-wall and solvent-wall. When solute-than solvent-wall, a surface excess (depletion) of solute particles on solid-liquid interface is formed which induces diffusio-osmosis flow towards low (high) concentration. We modified the classical Derjaguin expression to include the effect of nanoscale hydrodynamics boundary conditions for the accurate prediction of diffusio-osmosis characteristics. Overall, our results provide the clear guidance for controlling fluids flow and manipulating motion of colloids under tunable solute concentrations.
A nanofilter for fluidic devices by pillar-assisted self-assembly microparticles