Fog Collection Efficiency Research Articles

High efficiency and fog flow direction-independent fog collector with pentagram bulges

Water scarcity is a global problem that has a great impact on people's production and life, and how to get as much fresh water as possible is an urgent problem to be solved nowadays. Inspired by umbrellas, corrugated paper, and desert beetles, this paper presents an efficient fog collector that combines macrostructures and surface wettability gradients. This fog collector has an overall inverted umbrella-like structure and a corrugated structure on the umbrella surface. Pentagram-shaped hydrophilic bulges are evenly distributed on the umbrella surface. When the number of hydrophilic bulges was 176 and the lower prong of the corrugated structure was at an angle of 30° to the horizontal, the fog collector reached an optimum fog collection efficiency of 231.5 % of the original copper sheet. In addition, sand impact tests and UV resistance tests were carried out to test the samples for practical application. After a long time of UV irradiation and many sand impacts, the contact angle remained above 150° Moreover, the fog collector not only uses materials which are abundant and easy to obtain, but also simple and efficient to prepare, which provides a new idea for the design of high-efficiency fog collectors in the future.

Three-dimensional framework of Cu2O micro/nano structure injected with lubricant for efficient fog harvesting

Fog harvesting is one of the most effective, direct, and low-cost methods to achieve sustainable development of freshwater resources. In recent years, slippery surfaces infused with lubricants have received much attention in terms of mist collection. Inspired by the lubrication characteristics of Nepenthes and guided by previous work experience, more slippery surfaces with structural features need to be studied. In this study, we successfully fabricated the Cu2O micro/nano thin wire structure on the surface of the copper foam three-dimensional framework by a simple two-step method. After the injection of dimethylsilicone oil, the smooth surface of the three-dimensional framework with lubricant injection was successfully designed. The fog collection efficiency can reach 0.277 g min−1 cm−2.

A nc-titania modified cellulose Janus membrane for unidirectional water penetration and fog collection

Janus membranes are ideal devices for sustainable fog collection to help alleviate the global water shortage. However, it remains challenging to obtain Janus membranes with sufficient flexibility, low cost, chemical stability and anti-pollution properties. In this work, flexible Janus membranes based on cellulose substrate were fabricated for effective fog collection. We undertook a detailed study of the formation mechanisms of the Janus membranes, which contain an asymmetric growth of titania and a single-side hydrophobic modification. The proper thickness and discontinuity of the hydrophobic layer allow unidirectional water penetration, and the punched holes provide rapid water conveyance channels. The perforated Janus membranes showed the highest fog collection efficiency (∼3 times as much as that of a totally hydrophilic membrane) of the various types that were prepared. Furthermore, the Janus membranes exhibit desirable anti-acid, anti-pollution and reusability properties, which demonstrate application potential in complicated practical settings.

Bionic collection system for fog-dew harvesting inspired from desert beetle

Obtaining clean water resources from the air is an important method to solve the water shortage problem in arid and semi-arid areas. Improving the efficiency of material water collection from the air remains a huge challenge that needs to be overcome. Inspired by natural creatures, a new combined mist dew collector is proposed. The collecting part of the system has a gradient structure with alternating convexity and endows it with different chemical wettability. Janus sponge will be used as the storage part and mechanically assembled together to form a fog/dew collection system. This combination approach can improve collection efficiency by adjusting the liquid behavior throughout the entire fog collection process, including nucleation of droplets during the capture process, high-speed transmission on conical channels, and separation and storage of droplets from Janus sponge. The synergistic effect of conical capture and sponge separation collection improves the efficiency of fog collection. Compared with traditional fog collection structures, our proposed collection system significantly improves the efficiency of fog collection. Meanwhile, our collection system can effectively collect dew under conventional subcooling conditions. The readily available low-cost raw materials, easy to assemble and disassemble, and easy to carry, our proposed fog/dew collection system combines fog and dew collection as a promising solution to alleviate freshwater shortages in many underdeveloped, arid, and island areas.

Origami-like 3D Fog Water Harvestor with Hybrid Wettability for Efficient Fog Harvesting.

Collecting water in fog has also become a breakthrough to solve the hidden danger of water shortage in some arid areas. The three-dimensional (3D) structure fog collection material can increase the surface area in direct contact with the fog flow and reduce the quick flow of fog, which can effectively improve the fog collection efficiency. Imitating the three-dimensional structure of corrugated paper, the 3D fog collecting material with hybrid wettability was prepared by chemical and physical means. We discuss the influence of different wettability combinations on the fog collection efficiency of 3D structures and study the influence of spraying times and illumination times on the surface wettability during the construction of wettability. We also study the influence of the concavity and tip as well as the bending angle on the fog collection in the 3D structure and obtain the most reasonable concavity and convex ratio and bending angle. The superhydrophilic and superhydrophobic 3D structure fog harvesting material prepared by us performs well in the fog harvesting process, and the fog harvesting efficiency reaches 1.442 g cm-2 h-1. The fog collection efficiency is 418% of the original zinc sheet. At the same time, compared with the superhydrophilic and superhydrophobic hybrid two-dimensional (2D) plane, the increase is 168%, and compared with the superhydrophobic 3D structure, the increase is 150%.

An efficient fog collector inspired by Tillandsia and cactus spines

When the direction of the fog flow changes, the fog collection efficiency of the common fog collector relying on Janus will be affected. Inspired byTillandsia and cacti, three kinds of fog collectors with different bifurcation structures that are not affected by the direction of fog flow are designed. The fog collecting efficiency of sample 3 can reach 2.26 times that of the modified cylinder, and the fog collecting efficiency is even close to 0.9 g·h−1·cm−2. In addition, the fog collecting efficiency of sample 3 can reach 12.17 times that of the unmodified cylinder. In addition, the sample can still maintain a high fog collecting level after ten fog collecting cycles.

Biomimetic surfaces with patterned wettability for high-efficiency dehumidification and fog harvesting

In this paper, by studying the characteristics of the bionic surface with pattern wettability, the process of its efficient dehumidification and atomization is explored. This paper briefly introduces the importance of dehumidification and physicochemical and the market demand, and also introduces the properties of superhydrophobic materials. The theoretical part mainly describes the basic principle of superhydrophobicity and the Wenzel and Cassie-Baxter models. Subsequently, natural and synthetic superhydrophobic surfaces are introduced, involving Namib beetles, butterfly wings, and so on. The final article points out that superhydrophobic surfaces can be used in numerous fields, especially in fog collection. However, the improvement of durability is the focus of attention for superhydrophobic surfaces. In future research, attention needs to be paid to the use of materials and the efficiency of fog collection.

Wettability contrast on the surface of CuO nanostructures for highly efficient fog harvesting

Fog collection can provide a sustainable and efficient method for solving the shortage of water resources. In this article, CuO nanostructures were designed and synthesized on the Cu mesh by a one-step oxidation method and used to collect water from fog. Their morphology and surface wettability are characterized through scanning electron microscopy and dynamic contact angle measuring device, while the process of fog collection is investigated by a high-speed camera. The fog collection efficiency depends on the microstructure of the sample surface, which could be well controlled by adjusting the reaction temperature. Compared with CuO nanoneedles and CuO nanowire clusters, CuO nanosheets promote the rapid falling of liquid droplets, improving the fog harvesting efficiency, which can achieve 3168 mg/cm2 within 120 s. CuO nanosheets have ultra-low adhesion due to high roughness and high air restraint ability, accelerating the transport of water droplets and reducing the re-evaporation of water droplets.

Design and optimization of an electrostatic fog collection system for water harvesting: Modeling and experimental investigation

Electrostatic fog collection presents a promising solution for addressing water scarcity by recovering water from fog. This study proposed a multi-channel electrostatic fog collector that utilizes multiwire-to-plate electrodes. Through numerical simulations, the charging and migration mechanisms of fog droplets were revealed. Additionally, the influence of electrode structure parameters on the electrostatic fog collection process was analyzed. Results show that during the charging process, droplet charge rapidly approaches saturation near the wire electrodes. Moreover, the fog collection efficiency increases with an increase in working voltage, but the growth rate decreases gradually at high voltage. The wire interval and wire-plate gap determine the electric field distribution, which in turn affects the collection efficiency. The effect of wire interval and wire-plate gap on the electric field distribution could be categorized into three zones: the insensitive region, the weak influence region, and the strong influence region. The simulation results show that the optimal range of the dimensionless wire interval falls in the weak influence region, specifically in the range of 0.8 ≤ S/G ≤ 1.6, where S/G represents the ratio of wire interval to wire-plate gap. The experimental results demonstrate that the electrostatic fog collector within this range can achieve a water collection rate of 123.7 g/min at 20 kV. The corresponding performance coefficient is 388.7 kg/kWh, which exceeds the 200–333.3 kg/kWh performance coefficient of commonly used commercial reverse osmosis desalination technology. These findings provide direction for the practical application of electrostatic fog collection technology.

Development of gradient-wetting Janus wood membrane with high-efficiency fog collection and oil-water separation

Conventional preparation of Janus membranes with asymmetric wettability focuses on the preparation of extreme hydrophilic side and hydrophobic side, but suffers from pore clogging, low liquid transfer and collection efficiency and short service life. In this study, Janus wood (JW) with a continuous wettability gradient was created throughunidirectional vacuum impregnation of a hydrophobic solvent after the delignification of wood. Digital image correlation (DIC) and layer-by-layer contact angle assessment were utilized to examine the thickness-dependent wettability gradient of the JW membrane. The JW membrane completed the modification of the cell walls without blocking the cell lumens. The presence of wettability gradient in the JW membrane effectively reduced the capillary force of liquid penetration, resulting in decreased adhesion and stagnation of liquid on the membrane surface, and increased flow rate and transport efficiency. Based on the continuous wettability change of the JW membrane, the JW membrane was endowed with the ability to act as a “unidirectional valve” to enable continuous and rapid directional transport of liquids. The mechanical properties of the JW membrane prepared by the unidirectional introduction method were significantly improved, rendering them highly stable and environmentally durable. The fog collection efficiency of the JW membrane was maintained at 97.7% over 10 repeated use cycles. For light oil/water and heavy oil/water mixtures, JW membrane maintained an efficiency of 99.6% or higher. Unlike conventional surface modification methods, the unidirectional introduction method proved practical and effective for modifying the JW membrane in the thickness direction. Furthermore, the prepared JW membrane was sustainable, inexpensive, durable, and environmentally friendly. This study provides a wide range of potential applications in fields such as droplet manipulation, multi-liquid separation, industrial wastewater purification, and microfluidics.

Biomimetic 3D efficient fog harvester by synergistic wettability effect

By collecting water in the air, it is an important way to solve the problem of water shortage in arid and semi-arid areas. Improving the efficiency of fog harvesting is still a great challenge to be overcome. The use of 3D structure is an excellent strategy, here, a Multiple-biomimetic 3D hydrophilic and superhydrophobic fog harvester with a hump-valley structure was prepared by the combination of thermal processing and spraying. Inspired by biological water collection in nature, a 3D porous sponge surface with hydrophilic valley and superhydrophobic hump was obtained by two-step treatment. This surface structure showed excellent fog harvesting performance, which was 185 % higher than the original sponge. This structure accelerates the capture, transfer and transport of droplets during the fog harvesting process and greatly improves the efficiency of fog harvest. The results show that the chemical gradient and structural gradient actuation we constructed on the melamine sponge surface can effectively improve the fog collection efficiency. A surface with a linear hump-valley mixed wettability pattern is designed, and it is proved that fog collection efficiency can be effectively improved at the droplet capture and transfer stage and transport stage respectively. This study highlights a simple and cheap integrated fog harvester material design.

Super-Fast Fog Collector Based on Self-Driven Jet of Mini Fog Droplets.

Freshwater scarcity crisis threatens human life and economic security. Collecting water from the fog seems to be an effective method to defuse this crisis. Nonetheless, the existing fog collection methods have the limitations of the low fog collection rate and efficiency because of their gravity-based droplet shedding. Here, the aforementioned limitations are resolved by proposing a new fog collection method based on the self-driven jet phenomenon of the mini fog droplets. A prototype fog collector (PFC) composed of a square container that is filled with water is first designed. Both sides of the PFC are superhydrophobic but covered with superhydrophilic pore array. The mini fog droplets touching the side wall are easily captured and spontaneously and rapidly penetrate into the pores to form jellyfish-like jets, which greatly increases the droplet shedding frequency, guaranteeing a higher fog collection rate and efficiency compared with the existing fog collection methods. Based on this, a more practical super-fast fog collector is finally successfully designed and fabricated which is assembled by several PFCs. This work is hoping to resolve the water crisis in some arid but foggy regions.

Efficient fog collector with superhydrophobic coated surface

In this work, we developed a novel harp structure that collects water directly from fog in comparison with conventional Raschel mesh. Polyethylene (PE) monofilament was used as a collector’s element in the harp. The Raschel mesh in its particular design is quite anisotropic, shows elastic behavior breadth-wise while no stiffness is exhibited in transverse direction. A comparison of fog collection yield for the harp signifies that fog harvesting rate is four times higher than Raschel mesh, suggesting some alterations in monofilament diameter and collector element. Therefore, harp technology with cylindrical monofilaments can be deployed commercially to increase the efficiency of fog collectors, where mass and velocity of fog are inappropriate for Raschel mesh. In addition, silane-coated harp showed that surface hydrophobicity further enhances fog collection efficiency. The fog collector element (FCE) after silane coating significantly enhanced fog water collection yield. Samples were characterized by high resolution scanning electron microscope (HR-SEM), energy-dispersive x-ray (EDX) and atomic force microscope (AFM). Hydrophobicity was analyzed by static water contact angle and water collection yield.

Research progress of bionic fog collection surfaces based on special structures from natural organisms.

With the increasing shortage of water resources, people are seeking more innovative ways to collect fog to meet the growing need for production and the demand for livelihood. It has been proven that fog collection is efficient for collecting water in dry but foggy areas. As a hot research topic in recent years, bionic surfaces with fog collection functions have attracted widespread attention in practical applications and basic research. By studying natural organisms and bionic surfaces, more avenues are provided for the development of fog collection devices. Firstly, starting from biological prototypes, this article explored the structural characteristics and fog collection mechanisms of natural organisms such as spider silk, desert beetles, cactus, Nepenthes and other animals and plants (Sarracenia, shorebird and wheat awn), revealing the fog collection mechanism of the natural organisms based on microstructures. Secondly, based on the theory of interfacial tension, we would delve into the fog collection function's theoretical basis and wetting model, expounding the fog collection mechanism from a theoretical perspective. Thirdly, a detailed introduction was given to prepare bionic surfaces and recently explore fog collection devices. For bionic surfaces of a single biological prototype, the fog collection efficiency is about 2000-4000 mg cm-2 h-1. For bionic surfaces of multiple biological prototypes, the fog collection efficiency reaches 7000 mg cm-2 h-1. Finally, a critical analysis was conducted on the current challenges and future developments, aiming to promote the next generation of fog collection devices from a scientific perspective from research to practical applications.

Temperature-gradient-induced enhanced fog collection on polymer brush surfaces

Since the global water shortage, fog collection based on functional materials and surfaces has become one of the most potential ways to relieve the crisis. However, further improving the water collection efficiency through elaborate designs of material structures still encounters a bottleneck. Here, we present a temperature gradient-induced strategy for enhancing water collection from fog. Such a temperature modulation generates increases in the fog collection efficiency and surface-refreshing frequency by 25% and 217%, respectively. Scattering measurements show that the movement velocity of fog particles near cooling surfaces is increased by approximately 150%. Based on the theory of heat transfer and thermophoresis, the temperature field acting on fog particles is analyzed, deducing that the enhanced fog-collection performance results from thermophoretic forces generated by temperature gradients. This work offers a new approach for designing next-generation fog-collection devices and manipulating particle motions.

Integrative Bioinspired Surface with Annular Pattern and Three Dimension Wettable Gradient for Enhancement of Fog Collection

AbstractA novel integrative bioinspired surface with annular pattern and 3D wettable gradient (APWG) is proposed for fog collection via a simple needle‐face anodic oxidation strategy. The fog collection behaviors are studied on APWG with different pattern types. Such a surface can not only improve the fog droplet capture performance effectively owing to annular wettable gradient pattern, but also realize the fog droplet capture and convergence on different surfaces to accelerate the surface regeneration rate, leading to a further fog collection enhancement. The results of experiment observation and underlying mechanism analysis have certified that such a design can realize a continuous 3D fog collection model to enhance the fog collection efficiency, resulting in a 1345% increase compared to the original surface.

CuO nanomesh hierarchical structure for directional water droplet transport and efficient fog collection

Collecting water from fog is a promising approach to solve the shortage of water resources by micro-nano scale hierarchical structure material surface. Inspired by the structures of cactus and pine needles, CuO micro-nano scale structures attached to the surface of Cu foam are designed to increase the efficiency of fog collection and droplet transport. The structural evolution from CuO nanowires to CuO nanomesh and CuO nanosheets is achieved by regulating the synthesis conditions. The results show that the synthesized CuO nanomesh hierarchical structure is more favorable for fog collection, and the collection efficiency can achieve a rate of up to 34.6 mg/cm2 s. The tip structure can rapidly capture and coalesce small droplets in a foggy environment, which significantly improves the fog collection efficiency. In addition, the synthesized mesh structure and inter-neighborhood gaps have a strong ability to confine air, making the surface has small adhesion and enabling water droplets to fall quickly, which realizes the transport of the collected water efficiently and sustainably. The research work opens a new path for constructing surface structures to improve fog collection performance and has reference value and promotion for the design and development of fog collectors.

Efficient fabrication of desert beetle-inspired micro/nano-structures on polypropylene/graphene surface with hybrid wettability, chemical tolerance, and passive anti-icing for quantitative fog harvesting

Obtaining fresh water from the atmosphere by fog collectors is a promising way to meet the challenge of the water crisis. Bioinspired fog collectors have attracted widespread attention, but their application is limited by complex preparation processes and weak environmental adaptability. Herein, an efficient method that combines extrusion compression molding and surface modification is proposed for the large-scale fabrication of united superhydrophobic-hydrophilic polypropylene/graphene nanosheets (UPP/GNS) films for quantitative fog harvesting. Specifically, the desert beetle-inspired micro-pillars on the UPP/GNS surface exhibit a hydrophilic top and a superhydrophobic bottom and sidewall. A micro-nano/structure-induced hybrid wettability is acquired with a CA of 160 ± 3°. The hybrid wettability is excellent in accelerating droplet condensation and aggregation, which is beneficial for mass transfer in a fog harvesting system. Importantly, excellent chemical tolerance, passive anti-icing, active photothermal anti-icing, and sufficient durability enable the UPP/GNS film to maintain a stabilized fog collection efficiency under various external disturbances, such as salt, acid-/alkali solutions, and high temperature. Finally, the combination of hydrophilic and superhydrophobic wettability endows the UPP/GNS film with a fog collection efficiency of 1251 mg cm-2h−1. The economical and mass production method for the efficient fabrication of high-efficiency UPP/GNS fog collectors is a promising solution for mitigating the global water shortage.

A Superhydrophilic Silicon Surface Enhanced by Multiscale Hierarchical Structures Fabricated by Laser Direct Writing.

Many biological surfaces with hierarchical structures exhibit super wetting properties, but a multiscale hierarchical metal surface with superhydrophilic performance is difficult to be fabricated using a simple method. In this work, we report a large area micro/nanotextured superhydrophilic silicon surface fabricated by a laser direct writing technique. The combination of a microscale column structure and randomization-distributed nano-bumps decorated on the column enhances the superhydrophilic properties, with the contact angle reduced substantially from about 46° to 0°, where the droplets are able to spread rapidly within 591 ms. The water wetting orientation can be regulated by controlling the shape of microcolumns on the surface. Moreover, our results show that the fabricated surface with the hierarchical structure has better droplet shape control performance and higher fog collection efficiency compared to a smooth surface. These surfaces have potential applications in heat exchangers, biosensors, cell adhesives, and self-cleaning solar cells.

Hybrid wettability surfaces with hydrophobicity and hydrophilicity for fog harvesting

Fog harvesting has gained increasing attention because it can effectively alleviate the shortage of fresh water resources. In this study, a simple atomization-assisted nonsolvent induced phase separation combined with high pressure spraying method was used to fabricate a micro-nano composite porous membrane with hybrid wettability for fog collection. The driving force generated by the surface energy gradient between the superhydrophilic and superhydrophobic regions is beneficial to improve the fog collection efficiency. The fog collection efficiency was found to be dependent on the surface microstructure and the coverage of hydrophobic region, which could be well adjusted by tuning the atomization pretreatment and the high pressure PDMS spraying time. The optimized fog collection efficiency was 46.2 mg·cm−2·min−1 when the atomization pretreatment time was 30 s and the high pressure spraying time was 1 s. The membrane also exhibited excellent structural stability when being used for oil water separation. This work provides a new idea for the preparation of membranes with hybrid wettability surface and their application in the field of fog collection.