“Liquid diode” with “gating” based on shape memory sponge

Superwetting Janus membranes with unique ability in unidirectional liquid transportation, known as “liquid diode”, have attracted much attention. Recently, endowing the Janus membranes with smart controllability becomes a new research hotspot. However, related reports are still rare and limited in regulating surface wettability, which can hardly avoid some imperfections such as the necessary constant external stimuli and change of water solution. Herein, we advanced an unprecedented strategy to smartly control the liquid permeation on Janus membrane by regulating the pore structure of the material, and report a smart Janus sponge (SJS) that is constructed from a super-hydrophilic sponge (SHS) and a hydrophobic shape memory sponge (HSMS). The pore size and thickness of the HSMS can be reversibly changed as it is pressed/recovered based on the excellent shape memory effect. With the variation of the HSMS, the water permeation performance can be smartly controlled, which is embodied in that only when the HSMS is in the pressed state, SJS acts as a “liquid diode”, otherwise it can prevent liquid from penetrating on either side. Finally, based on the smart controllability of the SJS, we simulated the scene of drug administration and demonstrated its potential application in the field of wound dressing. This work firstly reports a shape memory Janus membrane and provides a new way to control the liquid permeation, which can successfully avoid those shortcomings existing in current wetting-responsive Janus membranes. Given its excellent controllability, we believe it has potential applications in intelligent manipulation of liquid.