Liquid-based gating mechanism with tunable multiphase selectivity and antifouling behaviour

A rapid, reversible, non-fouling gating mechanism is created by infusing a porous membrane with a capillary-stabilized liquid that reconfigures under pressure to form a liquid-lined pathway, enabling selective multiphase transport with rationally tunable differential response profiles for a variety of liquids and gases. The impressive performance of biological pores in selectively coordinating multiphase transport between different environments without clogging has inspired attempts to construct synthetic pores that mimic this behaviour. But a single system capable of selectively handling and controlling complex multiphase transport has remained a distant prospect, and fouling is nearly inevitable. Xu Hou et al. show that capillary-stabilized fluids can reversibly seal pores in the closed state and can be rapidly reconfigured under pressure to create fluid-lined open pores. Because each transport substance has a distinct and rationally tunable gating threshold pressure, one system can be dynamically modulated for gas–liquid sorting and to separate a three-phase air–water–/oil mixture in a microfluidic flow. The liquid gating strategy enables efficient and fouling-resistant long-term operation with micro- as well as macro-scale fluid systems, which should prove useful in a wide-range of applications. Living organisms make extensive use of micro- and nanometre-sized pores as gatekeepers for controlling the movement of fluids, vapours and solids between complex environments. The ability of such pores to coordinate multiphase transport, in a highly selective and subtly triggered fashion and without clogging, has inspired interest in synthetic gated pores for applications ranging from fluid processing to 3D printing and lab-on-chip systems1,2,3,4,5,6,7,8,9,10. But although specific gating and transport behaviours have been realized by precisely tailoring pore surface chemistries and pore geometries6,11,12,13,14,15,16,17, a single system capable of controlling complex, selective multiphase transport has remained a distant prospect, and fouling is nearly inevitable11,12. Here we introduce a gating mechanism that uses a capillary-stabilized liquid as a reversible, reconfigurable gate that fills and seals pores in the closed state, and creates a non-fouling, liquid-lined pore in the open state. Theoretical modelling and experiments demonstrate that for each transport substance, the gating threshold—the pressure needed to open the pores—can be rationally tuned over a wide pressure range. This enables us to realize in one system differential response profiles for a variety of liquids and gases, even letting liquids flow through the pore while preventing gas from escaping. These capabilities allow us to dynamically modulate gas–liquid sorting in a microfluidic flow and to separate a three-phase air–water–oil mixture, with the liquid lining ensuring sustained antifouling behaviour. Because the liquid gating strategy enables efficient long-term operation and can be applied to a variety of pore structures and membrane materials, and to micro- as well as macroscale fluid systems, we expect it to prove useful in a wide range of applications.