Biomimetic Fabrication of Janus Fabric with Asymmetric Wettability for Water Purification and Hydrophobic/Hydrophilic Patterned Surfaces for Fog Harvesting.

The long-term shortage of freshwater resources has drawn increasing research attention for water purification and collection. This work reports a facile method to prepare Janus fabrics with asymmetric wettability for on-demand oil/water separation and hydrophobic/hydrophilic patterned fabrics for efficient fog harvesting. Here, the superhydrophobic fabric was prepared by in situ polymerization of polydivinylbenzene (PDVB) on cotton fabric. By regulating the polymerization time, the PDVB polymer content was changed, thereby achieving the regulation of the surface structure and wettability of the prepared fabric. Meanwhile, the superhydrophobic fabric exhibited excellent self-cleaning and antifouling performance, mechanical abrasion and chemical resistance, and environmental durability. Moreover, the photocatalytic degradation properties of PDVB were utilized to prepare the Janus fabric with asymmetric wettability. Water droplets could spontaneously penetrate from the hydrophobic side to the hydrophilic side, while not vice versa, achieving unidirectional transport of water. In addition, the prepared Janus fabric could be used for on-demand oil/water separation, including the heavy oil/water mixture and light oil/water mixture. The separation efficiency and collected oil purity of each mixture were higher than 99.00 and 99.94%, respectively. Furthermore, the hydrophobic/hydrophilic patterned fabrics were prepared by using the lithographic masks with different apertures under UV light irradiation. Based on the fog-capturing ability of the hydrophilic areas and the water transport performance of the hydrophobic regions, efficient fog harvesting was achieved. For the patterned fabric with larger hydrophobic/hydrophilic areas, the water collection rate reached 224.7 mg cm-2 h-1. Therefore, this simple strategy to achieve controllable gradient wettability by adjusting the surface structure and chemical composition of the fabric shows great potential in the filtration of purification of oily sewage and the efficient condensed collection of water.