Preperation And Multifunctional Applications Of Novel Janus Membranes

3-D porous Janus membranes exhibits unidirectional liquid-transport property from one side across to the other side driven by the asymmetric surface wetting property, viz. liquid “diode”,which has a tremendous potential in the field of liquid manipulation, fog or water harvesting, lab-on-a-chip, etc. Nevertheless, many obstacles such as complicated fabrication process and high cost have to be overcome to enable the Janus membranes with more practical applications. Moreover, it is attractive, but still a challenge to explore novel application of Janus membranes, as well as develop multifunctional, intelligent and responsive Janus membranes. Thus to develop simple preparation techniques and explore the multifunctional response come first in the field of Janus membrane.Based on the distinct structures and surface property of the commercial polytetrafluoroethylene(PTFE) composite microfiltration membranes, hydrophobic type and highly hydrophilic type of that membranes were utilized to fabricate Janus membranes with unidirectional water or oil transport behaviors in this study. For the hydrophilic ones, two strategies were applied to prepare Janus membranes with unidirectional water transport behavior via directly peeling off the selective layers or stepwise peeling after multifunctional response surface modification. For the hydrophobic ones, floating membranes on dopamine solution can fabricate another type of Janus membranes with thin hydrophilic layer and unidirectional oil transport behavior. The surficial microstructure, chemical properties and extended applications towards Janus membranes were investigated on the multifunctional response surface modification, tape peel-off management and floating modification on dopamine solution. The membrane microstructure before and after modification can be observed by scanning electron microscope(SEM), the surficial chemical composition and relative contents by energy dispersive X-ray spectroscopy(EDX) and X-ray photoelectron spectroscopy(XPS), the dye adsorption behaviors through UV-vis spectrophotometer(UV-vis) analysis, membrane surface wettability by contact angle(CA), test of unidirectional liquid transport behaviors by interfacial liquid penetration. To exploit the Janus membrane with unidirectional oil transport behaviors for separation of the oil-in-water emulsion, to exploit the capacity to collect and lock liquids of Janus membranes and compared hydrophilic or hydrophobic membranes and the corresponding mechanism. By using the method of proof of concept, exploring the combination of the surface morphology, chemical composition, wettability, responsiveness and the Janus performance towards Janus membranes.The results show that the tape peel off can tear the PTFE skin layer, make the membrane surface hydrophobicity that comes from the nature of the PTFE hydrophobic property and its microstructure. Single surface modification of dopamine can endow hydrophobic membrane with a thin hydrophilic layer. Pre-wetting of the thin layers of the corresponding Janus membranes can reduce the channel sizes, the Laplace pressure will be enhanced, and resulting in much higher hydrostatic pressures of liquids can penetrate the Janus film, which can achieve the locking behaviors. Magnetic Janus membrane can be controlled by magnetic field to collect and purify the dye waste water, pH response Janus membrane can be control by adjusting the pH of water or aqueous phase on the unidirectional water transport behavior, which proves the favorable compatibility of the surface modification technology and Janus performance.