Fabrication of hydrophilic and hydrophobic membranes inspired by the phenomenon of water absorption and storage of cactus

Abstract

Water shortage has become one of the most severe practical problems facing humans. Thus, an efficient and economic water-harvesting technology is urgent to develop. In this work, to prepare samples of hydrophilic and hydrophobic bilayer structures, three kinds of hydrophobic polyethylene terephthalate (PET) fibers with different pore diameters were dip coated to fabricate hydrophobic surfaces, which showed different hydrophobic effects. TiO2 was then sprayed onto the hydrophobic surface to form irregular protrusions and to increase surface roughness and surface energy. The distribution amount of TiO2 was controlled by adjusting the spraying distance of TiO2. Finally, ultraviolet irradiation was performed. The light response made the protrusions super hydrophilic and improved the capture of mist and moisture by increasing the surface wettability and Laplace pressure. Water-collection test was performed for samples with different spraying distances irradiated by ultraviolet rays. The spraying distance with the best water-collection efficiency was achieved. The hydrophilic surface (particles) was attached to a hydrophobic membrane, which quickly and effectively captured the mist and converted it to water, thereby easily discharging a large amount of water. This study is expected to promote the development of fogging drainage and alleviate the problem of water shortage.

Environmentally Responsive Materials for Building Envelopes: A Review on Manufacturing and Biomimicry-Based Approaches

“…Some well-known examples of species that have inspired biomimetic approaches that could develop water harvest systems recently are: different species of cactus [ 57 , 75 , 76 , 77 , 78 , 79 ], spiders and spider silks [ 80 ], Triarrhena sacchariflora [ 81 ], pitcher plants [ 82 ], such as the Nepenthes alata [ 83 ], cicadas [ 74 ], and beetles [ 56 , 79 , 84 , 85 ]. According to Li et al [ 83 ], even if cactus and spider silk have been well-studied, their gradient surfaces can only move the harvested water droplets over a limited drop-sized distance, which leads to a slow speed and limited practical use.…”