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.
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This work was supported in part by the Advanced Research Projects Agency-Energy (ARPA-E), US Department of Energy, under award number DE-AR0000326. We thank M. Aizenberg, R. T. Blough and X. Y. Chen for discussions; A. B. Tesler for assistance with the scanning electron microscopy; and T. S. Wong, B. D. Hatton and R. A. Belisle for assistance with antifouling experiments.
The authors declare no competing financial interests.
This file contains Supplementary Methods, Supplementary Tables 1-4, Supplementary Figures 1-16, Supplementary Text & Data and Supplementary Results & Discussion. (PDF 3145 kb)
A liquid-gated membrane incorporated into a port along a microfluidic channel enables a series of distinct pressure-dependent scenarios for a mixed air/water flow. Below both Pcritical(air) and Pcritical(water), nothing crosses the port. Above Pcritical(air)) and below Pcritical(water), only air flows through the port and degassed water continues through the channel beyond the port. Above both Pcritical(air) and Pcritical(water), both phases cross the port and only water continues through the channel. Above both critical pressures, the water:air ratio that crosses the port increases with increasing pressure. This behavior remains robust for at least six days of continuous operation (flow rates 5-1000 µL/min). (MP4 12677 kb)
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Hou, X., Hu, Y., Grinthal, A. et al. Liquid-based gating mechanism with tunable multiphase selectivity and antifouling behaviour. Nature 519, 70–73 (2015). https://doi.org/10.1038/nature14253
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