Figure 4. The DCMD results of Janus membranes fabricated using hydrophilic PVDF support; the pressure and time of deposition were 1200 mTorr and 15 minutes. The feed solution included 35 g/L sodium chloride. The reported porosity, thickness, and pore size of pristine PVDF supports were 70%, 125 μm, and 220 nm, respectively. The feed and distillate temperatures were kept at 70 and 20 oC, respectively. The feed and distillate flowrates also were 0.2 and 0.15 L/min, respectively.
Conclusion
We developed a scalable method for the fabrication of Janus membranes through initiated chemical vapor deposition (iCVD) of fluoropolymers on porous media. We showed that the asymmetric wettability in the hydrophilic porous substrates is created by limiting the PTFE deposition to the surface of the porous domain. This objective was achieved by filling the substrates with non-volatile liquid (glycerol) mixtures. Also, we found that the presence of a free radical inhibitor in the liquid mixtures delays the deposition of PTFE on the surface of the mixture. The characterization of the developed membranes using sessile drop contact angle measurements and membrane distillation proved the effectiveness of our approach in fabricating Janus membranes.