(288g) Surface Functionalization and Peeling-Off Manipulation Generating Diversified Janus Membranes Toward Multifunctional Applications

Janus membranes (JMs) exhibit cross-sectional unidirectional liquid transportation feature with the aid of the asymmetric surface wetting property, viz. liquid “diode”. It demonstrates tremendous potential for applying in liquid manipulation, lab-on-a-chip, etc. Nevertheless, many barriers such as complicated fabrication process and high cost have to be removed to endow as-prepared JMs with more practical applications. Herein, surface functionalization and peeling-off manipulation was used to generate diversified JMs toward multifunctional applications. As a proof of concept, based on the structure and hydrophobicity of the commercial-available polytetrafluoroethylene (PTFE) composite microfiltration membranes, hydrophobic type of membranes were used to fabricate JMs with unidirectional water or oil transport behaviors in this study. Totally hydrophilic treatments on pristine membranes were conducted to prepare water unidirectional transport JMs via directly peeling off top layer or subsequent peeling after multifunctional surface treatment. On the other hand, floating substrates on dopamine solution resulted in another type of oil unidirectional transport JMs with thin hydrophilic layer and unidirectional oil transport behavior. Afterwards, the corresponding asymmetric chemistry and morphology, and extended applications were studied. We exploited JMs with unidirectional oil transport behaviors for separation of the oil-in-water emulsion, and exploited the feasibility on collection and lock of liquids using JMs, explored mechanism based on the contrast hydrophilic or hydrophobic membranes. As proof of concept, the combination of the surface morphology, chemical composition, wettability, responsiveness and the Janus performance towards Janus membranes were explored. It exhibited that the tape peeling-off could tear the PTFE skin layer to generate new hydrophobic surface derived from the nature of the exposed PTFE. Unilateral deposition of polydopamine could endow hydrophobic membrane with a thin hydrophilic layer. Pre-wetting of the thin layers of JMs could reduce the channel sizes, the Laplace pressure would be enhanced. It resulted in much higher hydrostatic pressures of liquids to penetrate the Janus film, which can achieve the locking behaviors. Magnetic JMs can be tuned by magnetic field to collect and purify the dye waste water, pH response JMs can be controlled via adjusting the pH of droplet or aqueous environment on the unidirectional water transport behavior, which demonstrates the benign controllability of multi-functionalization technology and Janus performance.