Enhancing Fog Harvest Efficiency by 3D Filament Tree and Elastic Space Fabric

Due to its multidimensional multilayer structure, elastic 3D space fabric (3D@SF) has a large fog capture area. However, it is constrained by droplet clogging. To solve the droplet clogging challenge, we created a new tree structure (Tree 3D@SF) that is almost similar to the branch of the Swamp Foxtail flower and to the two edges of a Shorebird's beaks. The filament surface of Tree 3D@SF's was modified by a simple bilayer method using silica nanoparticles and a hydrophobic adhesive to form hydrophobic bumps that periodically alternated highly hydrophobic sites. This formed the Hydrophobic/High Hydrophobic Bump-Tree 3D@SF. In addition, we adopted the sol–gel (polyurethane, tetraethyl orthosilicate and methyltriethoxysilane) and electrospray (PVAc) methods to develop High Hydrophobic-Tree 3D@SF and High Hydrophilic Knot-Tree 3D@SF. Specially, a novel-potential Auto 3D@SF fog collector was also developed by taking advantage of elasticity and change in the V-thread angle of 3D@SF, which was controlled by an automatic compression–relaxation system. Auto 3D@SF can be used in complex windy environments. Our results revealed that water harvesting rates using Auto 3D@SFs (4.31 g/cm2/h) and Tree 3D@SFs (4.29 g/cm2/h) were twice that of Original 3D@SF. This was attributed to improved synergistic effects of fog capturing, droplet growing and droplet shedding. These findings will inform the development of suitable designs of improved fog harvesters, particularly those that are based on elasticity of 3D space fabrics and textiles.