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

摘要

生物小孔在选择性地协调不同环境之间的多相运输不致发生堵塞方面给人印象深刻的表现，启发人们去构建模仿这种行为的合成小孔。但构建单独一个能够选择性处理和控制复杂多相运输的系统仍是一个遥远的愿望，污染几乎不可避免。Xu Hou等人发现，通过毛细管稳定的流体能够可逆地将小孔密封在闭合状态，并可在压力下迅速重新配置，以生成内壁上有流体的开启小孔。因为每种运输物质都有一个不同的、可以合理调节的门控阈限压力，所以一个系统能够为气-液分选以及为对一个"微流体流"中的一种气-水-油三相混合物进行分离而动态地被调制。这种液体门控方式能够对微观以及宏观流体系统进行高效的、防污染的长期操作，这在一系列不同应用中将会被证明是有用的。%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 systems. But although specific gating and transport behaviours have been realized by precisely tailoring pore surface chemistries and pore geometries, 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.