Beetle-Inspired Dual-Directional Janus Pumps with Interfacial Asymmetric Wettability for Enhancing Fog Harvesting

Fog-harvesting devices (FHDs) have been widely explored and applied to alleviate the shortage of fresh water. However, during the fog collection process, how to maintain a balance between fog capture and water removal behaviors to enhance the water collection rate still remains a challenge. Herein, inspired by the Stenocara beetle, we combined a beetle-like Janus surface and the conventional cross-sectional Janus structure together, developed a simple spray-and-dry strategy to obtain three types of biomimetic asymmetric meshes, and explored the working modes for atmospheric fog collection. The surface wettability could be carefully controlled, and various asymmetric meshes with different water transportation behaviors were obtained. Through a detailed study of the fog collection process, we concluded that there existed three main working modes: Janus mode, hybrid mode, and Janus and hybrid mode. It was noted that the dual-directional Janus pump with the Janus and hybrid working mode balanced the fog capture and water removal ability and exhibited the highest water collection rate of 2478.73 mg m^-2 h^-1, which was 2.61 times more than that of the corresponding superhydrophilic mesh. Furthermore, the prepared dual-directional Janus pump showed superior mechanical durability and antibacterial ability. In general, this work was considered instrumental in the reasonable design of biomimetic asymmetric meshes and could provide references for efficient atmospheric fog harvesting.