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

Abstract

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.

Thermodynamically Induced Interfacial Condensation for Efficient Fog Harvesting

“…At 532.4 eV, there was a typical metal‐oxygen bond (Ni/Co─O), and at 533 eV, there was a carbonyl group. [ 13 ] These findings indicated that the stearic acid anion was attached to the surface of the cobalt‐nickel hydroxide via metal‐oxygen bonds, giving the fabric hydrophobicity.…”

Overview of the design of bionic fine hierarchical structures for fog collection

“…Inspired by lotus leaves and beetles, Li's group developed a hydrophilic-hydrophobic/superhydrophilic unpaired lattice with a Janus structure for directional water transport. 144 Their test results showed that this HS (with alternating hydrophilic and hydrophobic surfaces and different wettability on both sides) can achieve a balance between fog capture and fog removal efficiency, and the maximum FC efficiency was measured to be 2478.73 mg m À2 h À1 .…”

“…The name Janus membrane is derived from the ''two-faced god'' in ancient Roman mythology. 121,128,129 This design was inspired by the difference in wettability between the two sides of the lotus leaf. One of the most important properties of these membranes is their ability to manipulate and control fluid transport.…”

Designing Janus Two-Dimensional Porous Materials for Unidirectional Transport: Principles, Applications, and Challenges

“…(b) Surface nonuniformity in the hydrophobic layer causes unidirectional transport. Reproduced from ref . Copyright 2022, American Chemical Society.…”