Research On Liquid Gating Asymmetric Deformable Membrane With The Unidirectional Gas Transport

In practical applications,transport and separation of gas in multiphase mixtures through membranes,such as gas-involved chemical reactions,fuel cells,and multiphase microreactors,is of great significance.The smart gating membrane is one of the most significant and promising fields in membrane science and technology.Among them,the liquid gating membranes,which can control gas transport in a simple way with micron-scale membranes,is a breakthrough in the transport of multiphase including gas.But it is still a difficult problem to achieve different gas flowability in two directions on a single membrane.Although the Janus membrane with unidirectional transport property can control the flow direction of bubbles,the existing work should be carried out in water environment,and the ability to control gas transport is limited by the small transportation volume.In this work,we present a liquid gating asymmetric deformable membrane for controlling the gas flowability in different directions through a unique reversible asymmetric deformation mechanism.The asymmetric deformation of the membranes causes the change of critical pressure for gas transport though the membranes,which controls over the gas flowability.Based on this mechanism,the design of directional valve with different critical pressure for gas can be realized by simply folding a membrane in various ways.This method is beneficial to control the transmembrane transport of gas-liquid with excellent antifouling performance and lays a foundation for the application of liquid gating membranes.The main contents are shown as follows:(1)The asymmetric deformable membranes composed of polyvinylidene fluoride(PVDF)layer and polyvinylidene fluoride/polyacrylonitrile(PAN)layer can be prepared by a simple sequential electrospinning technique,and the liquid gating asymmetric membranes were prepared by combining functional liquid.The stability of this membrane was proved by theory and experiment.(2)Deformations of the two layers of asymmetric deformable membrane are different under the same pressure that PVDF/PAN layer with small elastic modulus deforms significantly,while the PVDF layer with large elastic modulus almost remains unchanged.The deformation of PVDF/PAN layer reduces the average pore size and increases the pressure of gas flowing through in the direction where the gas first contact PVDF/PAN layer of liquid gating asymmetric deformable membranes,which leads to different critical pressures for gas transport though the membrane in two directions.In addition,by folding the membrane in different ways,the critical pressures for gas will be different,which is of great significance to the design of gas directional valves with different thresholds.(3)The unidirectional separation of gas-liquid under a constant pressure can be realized in independently designed separation device based on the liquid gating asymmetric deformable membranes with excellent anti-fouling performance.It endows the membrane a new platform for the application of multiphase flow control.