Electrospun Bead-On-String Hierarchical Fibers for Fog Harvesting Application

Quest for efficient fog harvesting methods has drawn immense attention in recent times. In this study, electrospinning is used to fabricate three different sets of membranes that are based on pristine poly(N-isopropylacrylamide) (PNIPAM) fibers, pristine polyvinylidene fluoride (PVDF) fibers, and PNIPAM-PVDF bead-on-string fibers. The wettability of these membranes is investigated as a function of temperature and the effect of their wettability on the fog collection efficiency is determined. Membranes based on pristine PNIPAM and pristine PVDF fibers are fabricated using conventional electrospinning and are shown to have a smooth surface morphology. On the other hand, PNIPAM-PVDF bead-on-string fibers are fabricated using core-shell electrospinning. Water collection efficiency of the membranes is compared to investigate the influence of microstructures and wettability gradient on fog harvesting ability of the samples. Among the three samples, the bead-on-string hierarchical fibrous membrane demonstrates the highest fog harvesting rate of 1150 +/- 28 mg cm(-2) h(-1) at 25 degrees C and 909 +/- 31 mg cm(-2) h(-1) at 40 degrees C. Furthermore, the results demonstrate that the presence of microstructures on the nanofibers improve the fog harvesting efficiency of PNIPAM-PVDF bead-on-string fibers.