Switchable smart porous surface for controllable liquid transportation

Controllable liquid transportation through a smart porous membrane is realized by manipulating the surface wetting properties and external stimuli, and has been intensively studied. However, the liquid transportation, e.g., permeation and moving process, at the interface is generally uninterrupted, i.e., the opening and closing of the interface is irreversible. Herein, we present a new strategy to achieve magnetic adaptive switchable surfaces, i.e., liquid-infused micro-nanostructured porous composite film surfaces, for controllable liquid transportation, via modulation of the magnetic field. The liquid transportation process can be interrupted and restarted on the porous composite film because its pore structure can be quickly closed and opened owing to the adaptive morphological transformation of the magnetic liquid with a varying magnetic field. That is, the liquid permeation process occurs due to the open pore structure of the composite film when the external magnetic field is added, while the permeation process can be interrupted owing to the self-repairing closure of the pore when the magnetic field is removed, and the moving process can be achieved. Thus a magnetic field induced switchable porous composite film can serve as a valve to control liquid permeation based transportation, which opens new avenues for artificial liquid gating devices for flow, smart separation, and droplet microfluidics.