Elastic Textile Threads for Fog Harvesting

Biomimetic Leaf-Shaped Wedge Structure with Mixed Wettability for Fog Harvesting

Water scarcity is a pressing issue in arid and semi-arid regions, making fog harvesting a promising method for water collection. However, enhancing the rate of fog harvesting remains a challenge. Controlling the movement of droplets on functional surfaces is crucial for the development of effective water-harvesting devices. In this study, a three-dimensional (3D) fog-harvesting device with mixed wettability is fabricated using a combination of physical and chemical techniques. With inspiration drawn from natural organisms, such as the desert beetle and Nephrolepis cordifolia, which can both live in low humidity, a copper substrate with a leaf-shaped wedge superhydrophilic structure and flat superhydrophobic regions is fabricated for fog harvesting. The modified surface results in a maximum 49.89% improvement in fog-harvesting efficiency compared to the original copper substrate. The synergistic effect of the 3D structure and mixed wettability of this study offers an idea for improving fog collection efficiency, with potential implications for energy sustainability water resources.

Gradient-Janus Wires for Simultaneous Fogwater Harvesting and Electricity Generation

A Gradient-Janus wire (GJW) with a diameter of 0.3 mm has been fabricated on a large scale through liquid confined modification, enabling the opposite conical wetting phenomenon along the same orientation of the GJW, characterized by an increasing superhydrophilic region and a decreasing hydrophobic region. This property allows the GJW to exhibit controllable water hovering, transport, and pinning during fog harvesting, i.e., at a large tilting angle α of 60° (mass increased with decreased α), the GJW can hover 0.6 mg of harvested fogwater in 30 s, can transport 3 mg of fogwater along the gradient in 30 s at α = 4° (with maximal mass reaching up to 4.3 mg at α = -10°), and finally, pin the water droplet at the end of the GJW. Such ability generates an effective torque that serves as the driving force for rotation. We designed a GJWs-wheel by radially arranging 60 GJWs together, resulting in an extremely lightweight structure weighing only 1.9 g. The cumulative torque generated during fog harvesting activates the rotation of the GJWs-wheel. When loaded with a coil within a magnetic field, electricity is generated as output power peaks at around 0.25 μW while maintaining a high water harvesting efficiency averaging approximately 38 ± 2.12 mg/min. This finding is significant as it provides valuable insights into designing materials capable of efficiently harnessing both energy and water resources.

Bionic Surfaces for Fog Collection: A Comprehensive Review of Natural Organisms and Bioinspired Strategies

Water scarcity has become a critical global threat, particularly in arid and underdeveloped regions. However, certain insects and plants have evolved the capability to obtain water from fog under these arid conditions. Bionic fog collection, characterized by passive harvesting, minimal energy requirements, and low maintenance costs, has proven to be an efficient method for water harvesting, offering a sustainable water source. This review introduces two superwettable surfaces, namely, superhydrophilic and superhydrophobic surfaces, detailing their preparation methods and applications in fog collection. The fog collection mechanisms of three typical natural organisms, Namib Desert beetles, spider silk, and cactus, along with their bionic surfaces for fog collection devices, are discussed. Additionally, other biological surfaces exhibiting fog transport properties are presented. The main challenges regarding the fabrication and application of bionic fog collection are summarized. Furthermore, we firmly believe that environmentally friendly, low-cost, and stable fog collection materials or devices hold promising prospects for future applications.