RESUMEN

Biomimetic engineering surfaces featuring heterogeneous wettability are vital for atmospheric water harvesting applications. Existing research predominantly focuses on the coordinated regulation of surface wettability through structural and chemical modifications, often overlooking the prevalent triboelectric charge effect at the liquid-solid interface. In this work, we designed a heterogeneous wettability surface by strategic masking and activated its latent triboelectric charge using triboelectric brushes, thereby enhancing the removal and renewal of surface droplets. By examining the dynamic evolution of droplets, the mechanism of triboelectric enhancement in the water collection efficiency is elucidated. Leveraging this inherent triboelectric charge interaction, fog collection capacity can be augmented by 29% by activating the system for 5 s every 60 s. Consequently, the advancement of triboelectric charge-enhanced fog collection technology holds both theoretical and practical significance for overcoming the limitations of traditional surface wettability regulation.

RESUMEN

Obtaining water and renewable energy from the atmosphere provides a potential solution to the growing energy shortage. Leveraging the synergistic inspiration from desert beetles, cactus spines, and rice leaves, here, a multibioinspired hybrid wetting rod (HWR) is prepared through simple solution immersion and laser etching, which endows an efficient water collection from the atmosphere. Importantly, benefiting from the bionic asymmetric pattern design and the three-dimensional structure, the HWR possesses an omnidirectional fog collection with a rate of up to 23 g cm-2 h-1. We further show that the HWR could be combined with a droplet-based electricity generator to convert kinetic energy from falling droplets into electrical energy with a maximum output voltage of 200 V and a current of 2.47 µA to light up 28 LEDs. Collectively, this research provides a strategy for synchronous fog collection and power generation, which is promising for environmentally friendly energy production.

RESUMEN

In this work, a superhydrophobic surface loaded with elliptical superhydrophilic patterns in a V-shaped arrangement has been fabricated with the help of shape memory membranes with uniform vertically penetrative channels (i.e., SMEUVs, as a mask). The special geometry (elliptical) and arrangement (V-shaped) of superhydrophilic patterns play important roles in the enhancement of fog collection. The former not only facilitates droplet detachment from superhydrophilic regions but also dominates its directional transport. The latter promotes the coalescence of tiny droplets based on directional flow pathway toward collection area, minimizing the risk of re-evaporation of them and providing fresh sites for subsequent nucleation and growth of droplets. The combination of them contributes to the synergistic effect of neighboring superhydrophilic patterns on the superhydrophobic surface. As a result, the optimal specimen (V-shaped arrangement of elliptical superhydrophilic patterns) in this work exhibits much higher fog collection efficiency (∼4 times) relative to the reference (superhydrophobic or superhydrophilic surface). Our results are significant for the design and fabrication of fog collection systems.

RESUMEN

Conventional fog collection efficiency is subject to the inherent inefficiencies of its three constituent steps: fog capture, coalescence, and transportation. This study presents a liquid bridge synergistic fog collection system (LSFCS) by synergistically utilizing a liquid bridge and interconnected porous superhydrophilic structures (IPHS). The results indicate that the introduction of liquid bridge not only greatly accelerates water droplet transportation, but also facilitates the IPHS in maintaining rough structures that realize stable and efficient fog capture. During fog collection, the lower section of the IPHS is covered by a water layer, however due to the effect of the liquid bridge, the upper section protrudes out, while covered by a connective thin water film that does not obscure the microstructures of the upper section. Under these conditions, a one-step fog collection mode is realized. Once captured by the IPHS, fog droplets immediately coalesce with the water film, and are simultaneously transported into a container under the effect of the liquid bridge. The LSFCS achieves a collection efficiency of 6.5 kg m-2 h-1, 2.3 times that of a system without a liquid bridge. This study offers insight on improving fog collection efficiency, and holds promise for condensation water collection or droplet manipulation.

RESUMEN

Various methods to solve water scarcity have attracted increasing attention. However, most existing water harvesting schemes have a high demand for preparation methods and costs. Here, a multi-biomimetic double interlaced wetting Janus surface (DIWJS) was prepared by laser for effective fog collection. The as-prepared surfaces are composed of superhydrophilic points/hydrophobic substrates on the A-side and superhydrophilic stripes/hydrophobic substrates on the B-side. The interlaced wettability and superhydrophilic points on the A side are conducive to capture and permeation of droplets. The superhydrophilic stripes and interlaced wettability on the B-side are conducive to transportation and shedding of droplets. Therefore, the overall fog collection process is accelerated. The proposal of smart farm model validates broad application prospects of DIWJS. This work provides an advanced and multi-biomimetic surface and provides important insights for green, low-cost, and versatile strategies to solve water scarcity issues.

RESUMEN

Fog collection serves as an efficient method to alleviate water scarcity in foggy, water-stressed regions. Recent research has focused on constructing a hybrid surface to enhance fog collection efficiency, with one approach being the prevention of liquid film formation at hydrophilic sites. Inspired by the desert beetle, a coating (10-MCC) made by partially acylating microcrystalline cellulose (MCC) exhibits hydrophilic sites alongside a hydrophobic skeleton enabling rapid droplet capture despite its overall hydrophobicity. The captured droplets quickly coalesce into a large droplet driven by the wetting gradient created by the hydrophobic backbone and hydrophilic sites. To achieve greater fog collection efficiency, a hydrophobic-superhydrophobic hybrid surface is formed by combining a coating of 10-MCC with a superhydrophobic surface. The construction of superhydrophobic surfaces typically involves creating a rough surface with a distinctive structure produced by the anodization technique and modifying it with stearic acid. The superhydrophobic surface exhibits excellent corrosion resistance and mechanical stability. Moreover, the hybrid surface shows high efficiency in fog collection, with a tested maximum efficiency of approximately 1.5092 g/cm2/h, 1.77 times that of the original Al sheets. The results demonstrate a remarkable enhancement in fog collection capacity. Furthermore, this work serves as an inspiration for the low-cost and innovative design of engineered surfaces for efficient fog collection.

RESUMEN

The efficient removal of droplets on solid surfaces holds significant importance in the field of fog collection, condensation heat transfer, and so on. However, on current typical surfaces, droplets are characterized by a passive and single removal mode, contingent on the traction force (e.g., capillary force, Laplace pressure, etc.) generated by the surface's physics and chemistry design, posing challenges for enhancing the efficiency of droplet removal. In this paper, an effective active strategy based on different removal modes is demonstrated on magnetic responsive polydimethylsiloxane (PDMS) superhydrophobic microplates (RM-MPSM). By regulating the parameters of microplates and droplet volume, different effective departure modes (top jumping and side departure) can be induced to facilitate the removal of droplets. Moreover, the removal volume of droplets through the side departure mode exhibits a significant reduction compared to that observed in the top jumping mode. The exceptional removal ability of RM-MPSM demonstrates adaptability to diverse functional applications: efficient fog collection, removal of condensation droplets and micro-particles. The efficient modes of droplet removal demonstrated in this work hold significant implications for broadening its application in many fields, such as droplet collection, heat transfer, and anti-icing.

RESUMEN

The shortage of freshwater resources is a serious problem faced by mankind in the 21st century. To maximize the acquisition of freshwater resources, numerous fog collectors have been constructed. In the process of fog collection accompanied by the movement of the wind, the mechanical energy brought about by the wind is often ignored. Based on this, inspired by beetles and origami art, we designed a windmill installation with a bump on the edge. Droplets nucleate at the windmill bulge and accelerate the transport process under the action of centrifugal force. This leads to quick fog collection and reduces the secondary evaporation rate of freshwater resources. The fog collection efficiency can reach 2.8 times that of the original sample. Moreover, the windmill can convert mechanical energy into electricity while collecting fog, and the operating voltage of a single windmill can reach 0.85 V. After the array, the amount of fog collected by the windmill and the power generation voltage can be increased by multiple times, which realizes the efficient use of energy and provides a new idea for the design of an efficient fog collector in the future.

RESUMEN

Efficient removal of droplets from solid surfaces is significant in various fields, including fog collection and condensation heat transfer. However, droplets removal on common surfaces with static structures often occurs passively, which limits the possibility of increasing removal efficiency and lacks intelligent controllability. In this paper, an active strategy based on extrusion ejection is proposed and demonstrated on the magnetic responsive polydimethylsiloxane (PDMS) superhydrophobic microplates (MPSM). The MPSM can reversibly transit between the upright and tilted state as the external magnetic field is alternately applied and removed. Under the magnetic field, the direction and trajectories of droplets departure can be intelligently controlled, demonstrating excellent controllability. More importantly, compared with the static structure where the droplet must reach a certain size before departure, droplets can be ejected at smaller sizes as the MPSM is tilted. These advantages are of great significance in many fields, such as a highly efficient fog harvesting system. This strategy of extrusion ejection based on dynamic surface structure control reported in this work may provide fresh ideas for efficient droplet manipulation.

RESUMEN

Harvesting freshwater from fog is one of the possible solutions to the global water scarcity crisis. Surfaces with both hydrophobic and hydrophilic regions are extensively employed for this purpose. Nevertheless, the longevity of these surfaces is still constrained by their delicate surface structures. The hydrophilic zones may become damaged or contaminated after repeated use, thereby compromising their effectiveness in fog collection. The preparation of generally applicable durable superhydrophobic coatings with self-generated Wenzel sites is reported here for long-term efficient and stable fog collection. The coatings are prepared by depositing the poly(tannic acid) coating as the primer layer on various substrates, self-assembly of trichlorovinylsilane into staggered silicone nanofilaments, and then thiol-ene click reaction with 1H,1H,2H,2H-perfluorodecanethiol. The coatings demonstrate remarkable static superhydrophobicity, robust impalement resistance, and stable self-generated Wenzel sites for water droplets. Therefore, the fog collection rate (FCR) of the coatings reaches 2.13 g cm-2 h-1 during 192 h continuous fog collection, which is triple that of bare substrate and outperforms most previous studies. Moreover, the systematic experiments and models have revealed that the key factors for achieving high FCR on superhydrophobic coatings are forming condensed droplets ≈1 mm in critical radius and a Wenzel site proportion of 0.3-0.4.

RESUMEN

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.

Asunto(s)

RESUMEN

Learning from nature, many bionic materials and surfaces have been developed for the directional transportation of water and fog collection. However, current research mainly focuses on the self-transportation behavior of droplets in air-phase environments, rarely concerning underoil environments. Herein, in this work, a liquid-assisted bionic copper needle was fabricated for the rapid self-transportation of water droplets in air and oil environments. The water droplet can be spontaneously transported on the as-prepared bionic copper needle from the tip to the base. More importantly, the water-prewetted bionic copper needle can achieve the ultrafast unidirectional transportation of a water droplet in an oil environment, showing a maximum transport velocity of 76.2 mm/s and a transport distance over 33 mm, which were ten times higher than those reported in the previous research. Additionally, the droplet transport mechanism was revealed. The effects of the apex angle and tilt angle of the as-prepared bionic needle and droplet volume on the self-transportation behavior of water droplets were systematically investigated. The results indicated that the transport velocity of the water droplet decreased with the increase of the apex angle of the conical needle, while it increased with the increase of the droplet volume and needle tilt angle. Furthermore, the as-prepared bionic copper needle exhibited excellent fog collection performance with a single copper needle fog collecting efficiency of up to 2220 mg/h, which was 9.7 times that of the original copper needle. In summary, this work provides a simple and novel method to fabricate bionic copper needles for the directional self-transportation of water droplets in air-phase and oil-phase environments as well as efficient fog collection. It shows great application potential in the fields of microfluidics, desalination, and freshwater collection.

RESUMEN

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.

RESUMEN

The integration of fog collection and solar-driven evaporation has great significance in addressing the challenge of the global freshwater crisis. Herein, a micro/nanostructured polyethylene/carbon nanotubes foam with interconnected open-cell structure (MN-PCG) is fabricated using an industrialized micro extrusion compression molding technology. The 3D surface micro/nanostructure provides sufficient nucleation points for tiny water droplets to harvest moisture from humid air and a fog harvesting efficiency of 1451 mg cm-2 h-1 is achieved at night. The homogeneously dispersed carbon nanotubes and the graphite oxide@carbon nanotubes coating endow the MN-PCG foam with excellent photothermal properties. Benefitting from the excellent photothermal property and sufficient steam escape channels, the MN-PCG foam attains a superior evaporation rate of 2.42 kg m-2 h-1 under 1 Sun illumination. Consequently, a daily yield of ≈35 kg m-2 is realized by the integration of fog collection and solar-driven evaporation. Moreover, the robust superhydrophobicity, acid/alkali tolerance, thermal resistance, and passive/active de-icing properties provide a guarantee for the long-term work of the MN-PCG foam during practical outdoor applications. The large-scale fabrication method for an all-weather freshwater harvester offers an excellent solution to address the global water scarcity.

RESUMEN

Fog collection is an effective method for addressing water shortages in arid areas. By constructing a Janus structure with asymmetric wettability on its two sides, flexible and efficient fog capture can be achieved. However, in situ detection and fog collection on a Janus surface are still challenging tasks. Herein, a novel method for producing a superhydrophilic-superhydrophobic Janus fog collector is proposed; the method utilizes a combined process in which a spatially shaped femtosecond laser treatment (superhydrophilic) is applied to one side of a copper foam and a chemical replacement reaction (superhydrophobic) is applied to the other side of the copper foam. Two configurations of the Janus structure were designed to study different water transport behaviors. Furthermore, the Au micro-nanoparticle prepared adhered to the Janus structure, indicating the effectiveness of surface-enhanced Raman spectroscopy detection. The Janus foam shows excellent sensitivity and stability on testing the fog mixed with rhodamine 6G. This surface allows for the simultaneous collection and detection of fog, which can provide insights into the preparation of Janus multifunction structures and how such structures can play a key role in the subsequent purification and usage of water resources.

RESUMEN

Water shortages are currently becoming more and more serious due to complicated factors such as the development of the economy, environmental pollution, and climate deterioration. And it is the best solution to the problems faced by people in today's world to investigate the bionic structure of nature and explore effective methods for fog collection. Herein, we've illustrated the bionic structures of the Namib desert beetle, cactus spines, and spider silk, and we imitate and further modify the respective bionic structures, as well as construct multifunctional bionic structures to improve fog collection. In addition, we also expound the fog collection behavior of a large fog collector, and an excellent fog capture effect was achieved through studying the mesh structure, the surface modification of the mesh, and the construction of the fog collector. The advantages and limitations of fog collection by a harp fog collector were also explored. We hope that through this review, relevant researchers can have a deeper understanding of this field and thus promote the development of fog collection.

Asunto(s)

RESUMEN

As the clean water shortage becomes a serious problem for mankind, atmospheric water harvesting has emerged as a viable solution. Two main approaches to collect water from the atmosphere exist: the first is to capture it from fog, whereas the second is through condensation of vapor on surfaces with a temperature below the dew point. The water collection mechanism in these two modes is completely different. In this work, we develop a deeper understanding of the effect of surface wettability on gravity-assisted atmospheric water harvesting and a comparative study of the two collection modes (fog and dew). First, we present theoretical estimates for the maximum water mass available in each mode and introduce an efficiency factor η which enables the direct comparison among surfaces in different setups and modes. Then we fabricate a series of micronanostructured surfaces with different surface wetting properties from hydrophilic to superhydrophobic. Our results demonstrate that drop mobility, derived from the surface superhydrophobic properties and micronanotopography, is the most important factor affecting fog collection: superhydrophobic surfaces show 40-65% higher fog collection rates compared to flat hydrophilic surfaces, with the more mobile among superhydrophobic surfaces (hysteresis 2°, and air-liquid fraction fA-L > 0.9) showing higher water collection. On the other hand, dew harvesting efficiency depends on the combination of drop mobility and nucleation rate, with superhydrophobic surfaces exhibiting 40% higher water collection rate compared to the flat hydrophilic or hydrophobic surfaces due to their low hysteresis as well as high surface area available for nucleation.

RESUMEN

Freshwater shortage is a critical global issue that needs to be resolved urgently. Efficient water collection from fog provides a promising and sustainable solution to produce clean drinking water, especially in the desert and arid regions. Nature has long served as our best source of inspiration for designing new structures and developing new materials. Herein, we report a strategy to design a novel Janus fog collector with a hydrophilic lizard-skin-like nanofibrous network upper surface and hydrophobic slippery lower surface using a simple and feasible method of coating and electrospinning. We analyze the forming law of the lizard-skin-like nanofibrous network structure on different substrates using electric field simulation. The resulting copper mesh-based Janus fog collector exhibits superior water-collecting efficiency (907 mg cm-2 h-1) and long-term durability, achieving directional transport of tiny droplets and high-efficiency water collection. However, there are few reports on the combination of the lizard-skin-like nanofibrous capillary network and slippery surface for efficient fog collection. Therefore, we believe that this work will open a new avenue to collect water efficiently and also provide clues to research on the lizard-skin-like nanofibrous network structure.

RESUMEN

HYPOTHESIS: The droplet manipulation behavior is affected by chemical structural driving force (including the superposition of electric, magnetic, optical and thermal fields), which directly determine transportation velocity. A lot of research has focused on a single driving force that induces the directional transportation behavior, which affects its performance. EXPERIMENTS: A simple method for preparing wettability gradient conical copper needles (WGCCN) combining structural gradient and chemical gradient was formulated. The effect of droplet volume and tilt angles on droplet transport velocity was systematically studied. The process of droplet transport was revealed through theoretical model and mechanical analysis. Finally, the application of WGCCN and its array model in fog collection were explored. FINDINGS: A continuous chemical gradient in the conical structure gradient induces the droplet directional transportation, and the transportation velocity depends on the droplet volume. In addition, under the cooperation effect of multiple driving force, the droplet can still be transported in a directional orientation even if it is tilted at a certain angle. The simple droplet manipulation behavior portends that the droplets directional transport behavior can be applied in microfluidic manipulation by cooperation of effective multiple driving force with satisfactory results.

Asunto(s)

RESUMEN

The outcomes of the study of plant surfaces, such as rice leaves or bamboo leaves, have led to extensive efforts being devoted to fabricating anisotropic arrays of micro/nanoscale features for exploring anisotropic droplet spreading. Nonetheless, precise engineering of the density and continuity of three-phase contact lines for anisotropic wetting remains a significant challenge without resorting to chemical modifications and costly procedures. In this work, we investigated secondary electrohydrodynamic instability in polymer films for producing secondary nanosized patterns between the micrometer-sized grooves by controlling the timescale parameter, 1/τm (>10-4 s-1). We experimentally demonstrated facile morphological control of anisotropic wettability without the use of any chemical modifications. Thus, anisotropic hydrophilic surfaces fabricated by the secondary phase instability of polymer films are advantageous for both droplet condensation and removal, thereby outperforming the water collection efficiency of conventional (isotropic) hydrophilic surfaces in water harvesting applications (∼200 mg·cm-2·h-1) with excellent durability.