Resonant osmosis across active switchable membranes

Abstract

To overcome the traditional paradigm of filtration, where separation is essentially performed upon steric sieving principles, we explore the concept of dynamic osmosis through active membranes. A partially permeable membrane presents a time-tuneable feature that changes the effective pore interaction with the solute and thus actively changes permeability with time. In general we find that slow flickering frequencies effectively decrease the osmotic pressure, and large flickering frequencies do not change it. In the presence of an asymmetric membrane, we find a resonant frequency where pumping of solute is performed and can be analyzed in terms of ratchet transport. We discuss and highlight the properties of this resonant osmotic transport. Furthermore, we show that dynamic osmosis allows to pump solute at the nanoscale using less energy than reverse osmosis. This opens new possibilities to build advanced filtration devices and design artificial ionic machinery.