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.