Zhecun Wang,Jianlin Yang,Xiadong Dai,Jing Guo,Shenghai Li,Tauqir A. Sherazi,Suobo Zhang
Directional liquid transport driven by the interface or surface property of Janus porous membrane owes great significance to many applications such as separation technology, fog collection, and energy devices. The Janus porous membranes have successfully demonstrated an efficient oil self-transport in water and also enable directional water transport in air or oil-water interface. However, the directional water transport in oil environment is a challenge because of the relatively low surface tension of oil. In this work, a novel integrated Janus porous membrane is developed for the first time to construct self-propelled energy free directional water transport in oil system that successfully demonstrated to be a facile “water diode” for under-oil water one-way regulation. Additionally, this Janus porous membrane exhibits an interesting tunable fluid-gating behavior for either water or oil, using optimized conditions. The current findings may promote the innovation towards directional liquid transport science and will open up new avenues for diverse on-demand liquids manipulation scenarios such as water-in-heavy oil emulsion separation.
The scarcity of freshwater is one of the challenges faced by humanity today. Solar desalination technology is gaining increasing attention due to its environmental friendliness and sustainability. However, the service life of the evaporator is significantly reduced by the problem of salt deposition during the evaporation process. In this work, a porous Janus evaporator with asymmetric wettability was fabricated using an atomization-assisted non-solvent induced phase separation method. The bottom surface of the Janus evaporator was fabricated with polyacrylonitrile and polyvinylpyrrolidone, working as capillary "pumps" to ensure adequate water supply. The upper surface was made of polyvinylidene fluoride which endows the evaporator with self-floating properties and the addition of CNTs improves its solar-to-vapor conversion efficiency. The micro-nano composite continuous porous structure of the Janus evaporator is beneficial to the enhancement of the capillary action, leading to good salt-repellent performance. The solar-to-vapor efficiency of the seawater desalination experiment under 1 kW·m −2 of sunlight was 81.61%, and the water evaporation rate was 1.30 kg·m −2 ·h −1 . In addition, the evaporator exhibited excellent stability under multiple cycles. It also functioned well in the treatment of organic wastewater. This work provides a novel method for preparing solar desalination materials.
Directional liquid transport on the surface is of great significance in liquid collection, transfer, and separation. Despite extensive research on surface wetting control, achieving unidirectional liquid permeation on material surfaces under water remains a challenge. Here, we demonstrate that electric field-induced unidirectional oil permeation can be achieved on a Janus-porous ion-doped polypyrrole membrane (Janus-PIPM). The results indicate that the competition between the liquid spread and permeation is crucial for achieving unidirectional liquid permeation. By designing and adjusting the dimensions of the pore structure and integrated mode, Janus-PIPM can be used to regulate the liquid transport behavior, i.e., spread or permeation. Furthermore, with the cooperation of an electric field, the Janus-PIPM with a specific pore size can realize the unidirectional oil permeation, which can be used as an electric field-responsive underwater–oil diode. Therefore, Janus-PIPM can serve as a valve for smart unidirectional liquid transportation and has broad prospects for applications in areas such as gate control switches, microreactors, microfluidic transport, and so on.
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