Improved Liquid Collection on a Dual-Asymmetric Superhydrophilic Origami

Laser-Constructed Bionic Composite Fog-Collecting Surfaces with Efficient Nucleation Sites and Enhanced Water Transport

Fog collection effectively alleviates the current freshwater shortage; thus, enhancing its efficiency is crucial. Here, we report a novel bionic fog collection surface (Al@B-V) comprising composite superhydrophobic bumps integrated with superhydrophilic V-channel grooves. This surface, which has efficient fog nucleation points and enhanced water transport capabilities, effectively balances fog capture and water transport during the collection process, thereby achieving high-efficiency fog collection. Compared to ordinary aluminum-based surfaces, Al@B-V achieves a fog collection efficiency of up to 3.08 g·cm-2·h-1, three times higher than the original aluminum-based surface. Furthermore, the V-channel groove proposed in this study exhibits a water transport speed of up to 165 mm·s-1, which is remarkably approximately 80 times faster than the commonly used U-channel groove. Additionally, this V-channel groove can overcome gravity, transporting approximately 10 μL of liquid to the top even when placed at 90° inclination. It can directionally transport 10 μL of liquid over a distance of up to 151 mm on a plane. This novel microgroove design can be effectively applied in various fields, including liquid collection, directional transport, seawater desalination, microfluidics, and drug delivery.

Biomimetic Fog Collector with Hybrid and Gradient Wettabilities

Water scarcity is a global problem and collecting water from the air is a viable solution to this crisis. Inspired by Namib Desert beetle, leaf venation and spider silk, we designed an integrated biomimetic system with hybrid wettability and wettability gradient. The hybrid hydrophilic-hydrophobic wettability design that bionomics desert beetle's back can construct a three-dimensional topography with a water layer on the surface, expanding the contact area with the fog flow and thus improving the droplet trapping efficiency. The venation-like structure with wettability gradient not only provides a planned path for water transportation, but also accelerates water removal under the synergistic effect of gravity and wettability driving force, thus further improving the surface regeneration rate. The collector combines droplet capture, coalescence, transportation, separation, and storage capabilities, which provides new ideas for the design of future high-efficiency fog collectors.

Magnetically Driven Cactus Spinelike Superhydrophobic Fe3O4 Vertical Array for High-Performance Fog Harvesting

Cactus spinelike materials have attracted much attention due to high fog harvesting efficiency, but great challenges in structure fabrication and structural controllability still remain. In this study, we proposed a magnetically driven spray-coating method to fabricate a cactus spinelike superhydrophobic Fe3O4 vertical array on nonwoven cotton fabric. This method is simple and controllable; a mixture containing magnetic Fe3O4 particles and organosilicon resin was atomized into tiny droplets and arranged along the magnetic field lines. Different from the traditional method to prepare a cactus spinelike structure via liquid flow under magnet, which is usually accompanied with a big structure size and an unobvious structure feature due to the high viscosity of magnetic liquid. However, if the magnetic liquid is transformed into tiny magnetic droplets by a spraying method, it is promising to prepare micrometer-scale conical structures, and the reduction degree of bionic structures is high. When the fabricated structure is used for fog harvesting, it shows an extremely high efficiency of approximately 6.33 g cm-2 h-1, which is superior to most state-of-the-art fog harvesting materials. Considering the advantages of simplicity, structure controllability, and high fog harvesting rate, the reported strategy provides an avenue to build up high-performance fog harvesting materials.

Nature-Inspired Superhydrophilic Biosponge as Structural Beneficial Platform for Sweating Analysis Patch

Perspiration plays a pivotal role not only in thermoregulation but also in reflecting the body's internal state and its response to external stimuli. The up-to-date skin-based wearable platforms have facilitated the monitoring and simultaneous analysis of sweat, offering valuable physiological insights. Unlike conventional passive sweating, dynamic normal perspiration, which occurs during various activities and rest periods, necessitates a more reliable method of collection to accurately capture its real-time fluctuations. An innovative microfluidic patch incorporating a hierarchical superhydrophilic biosponge, poise to significantly improve the efficiency capture of dynamic sweat is introduced. The seamlessly integrated biosponge microchannel showcases exceptional absorption capabilities, efficiently capturing non-sensitive sweat exuding from the skin surface, mitigating sample loss and minimizing sweat volatilization. Furthermore, the incorporation of sweat-rate sensors alongside a suite of functional electrochemical sensors endows the patch of uninterrupted monitoring and analysis of dynamic sweat during various activities, stress events, high-energy intake, and other scenarios.

Effect of Droplet-Removal Processes on Fog-Harvesting Performance on Wettability-Controlled Wire Array with Staggered Arrangement

Development of freshwater resources is vital to overcoming severe worldwide water scarcity. Fog harvesting has attracted attention as a candidate technology that can be used to obtain fresh water from a stream of foggy air without energy input. Drainage of captured droplets from fog harvesters is necessary to maintain the permeability of harp-shaped harvesters. In the present study, we investigated the effect of the droplet-removal process on the amount of water harvested using a harvester constructed by wettability-controlled wires with an alternating and staggered arrangement. Droplet transfer from hydrophobic to hydrophilic wires, located upstream and downstream of the fog flow, respectively, was observed with a fog velocity greater than 1.5 m/s. The proportion of harvesting resulting from droplet transfer exceeded 30% of the total, and it reflected more than 20% increase of the harvesting performance compared with that of a harvester with wires of the same wettability: this value varied with the adhesive property of the wires and fog velocity. Scaled-up and multilayered harvesters were developed to enhance harvesting performance. We demonstrated certain enhancements under multilayered conditions and obtained 15.99 g/30 min as the maximum harvested amount, which corresponds to 13.3% of the liquid contained in the fog stream and is enhanced by 10% compared with that without droplet transfer.

In Situ Multi-Directional Liquid Manipulation Enabled by 3D Asymmetric Fang-Structured Surface

Decorating surfaces with wetting gradients or topological structures is a prevailing strategy to control uni-directional spreading without energy input. However, current methods, limited by fixed design, cannot achieve multi-directional control of liquids, posing challenges to practical applications. Here, a structured surface composed of arrayed three-dimensional asymmetric fang-structured units is reported that enable in situ control of customized multi-directional spreading for different surface tension liquids, exhibiting five novel modes. This is attributed to bottom-up distributed multi-curvature features of surface units, which create varied Laplace pressure gradients to guide the spreading of different-wettability liquids along specific directions. The surface's capability to respond to liquid properties for multimodal control leads to innovative functions that are absent in conventional structured surfaces. Selective multi-path circuits can be constructed by taking advantage of rich liquid behaviors with the surface; surface tensions of wetting liquids can be portably indicated with a resolution scope of 0.3-3.4 mN m-1 using the surface; temperature-mediated change of liquid properties is utilized to smartly manipulate liquid behavior and achieve the spatiotemporal-controllable targeted cooling of the surface at its heated state. These novel applications open new avenues for developing advanced surfaces for liquid manipulation.

Improved Fog Collection on a Hybrid Surface with Acylated Cellulose Coating

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.

Bioinspired Gas Manipulation for Regulating Multiphase Interactions in Electrochemistry

The manipulation of gas in multiphase interactions plays a crucial role in various electrochemical processes. Inspired by nature, researchers have explored bioinspired strategies for regulating these interactions, leading to remarkable advancements in design, mechanism, and applications. This paper provides a comprehensive overview of bioinspired gas manipulation in electrochemistry. It traces the evolution of gas manipulation in gas-involving electrochemical reactions, highlighting the key milestones and breakthroughs achieved thus far. The paper then delves into the design principles and underlying mechanisms of superaerophobic and (super)aerophilic electrodes, as well as asymmetric electrodes. Furthermore, the applications of bioinspired gas manipulation in hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), and other gas-involving electrochemical reactions are summarized. The promising prospects and future directions in advancing multiphase interactions through gas manipulation are also discussed.

Advanced Fog Harvesting Method by Coupling Plasma and Micro/Nano Materials

Harvesting fog is a potential and effective way to alleviate the crisis of water resource shortage. A highly efficient and economical fog harvesting method has always been a global and common goal. Here, a promising fog harvesting method by coupling plasma and micro/nano materials is proposed, which can achieve 93% fog collection efficiency with consuming power of only 0.76 W/0.04 m2. The basic method is to utilize nanoparticles to decorate both the discharge electrode and the collecting electrode of the micro/nano electrostatic fog collector. For the discharge electrode, the nanoparticles can achieve an order of magnitude higher electric field strength and a 28.6% decrease in the operating voltage (14 kV decreases to 10 kV). For the collecting electrode, a novel composite structure of hydrophobic/hydrophilic (HB/HL) is proposed. The core advantage is the directional droplet transport at the junction of HB and HL caused by surface tension can adjust the accumulated droplets on the two sides, which avoids the droplet residue and mesh blockage in the general structure. This technology provides an innovative approach for the collection of microdroplets and a new design idea for the fog collector to deal with the water crisis.

Magnetic-Actuated Jumping of Droplets on Superhydrophobic Grooved Surfaces: A Versatile Strategy for Three-Dimensional Droplet Transportation

On-demand droplet transportation is of great significance for numerous applications. Although various strategies have been developed for droplet transportation, out-of-surface three-dimensional (3D) transportation of droplets remains challenging. Here, a versatile droplet transportation strategy based on magnetic-actuated jumping (MAJ) of droplets on superhydrophobic grooved surfaces (SHGSs) is presented, which enables 3D, remote, and precise manipulation of droplets even in enclosed narrow spaces. To trigger MAJ, an electromagnetic field is utilized to deform the droplet on the SHGS with the aid of an attached magnetic particle, thereby the droplet acquires excess surface energy. When the electromagnetic field is quickly removed, the excess surface energy is partly converted into kinetic energy, allowing the droplet to jump atop the surface. Through high-speed imaging and numerical simulation, the working mechanism and size matching effect of MAJ are unveiled. It is found that the MAJ behavior can only be observed if the sizes of the droplets and the superhydrophobic grooves are matched, otherwise unwanted entrapment or pinch-off effects would lead to failure of MAJ. A regime diagram which serves as a guideline to design SHGSs for MAJ is proposed. The droplet transportation capacities of MAJ, including in-surface and out-of-surface directional transportation, climbing stairs, and crossing obstacles, are also demonstrated. With the ability to remotely manipulate droplets in enclosed narrow spaces without using any mechanical moving parts, MAJ can be used to design miniaturized fluidic platforms, which exhibit great potential for applications in bioassays, microfluidics, droplet-based switches, and microreactions.

Durable Janus membrane with on-demand mode switching fabricated by femtosecond laser

Despite their notable unidirectional water transport capabilities, Janus membranes are commonly challenged by the fragility of their chemical coatings and the clogging of open microchannels. Here, an on-demand mode-switching strategy is presented to consider the Janus functionality and mechanical durability separately and implement them by simply stretching and releasing the membrane. The stretching Janus mode facilitates unidirectional liquid flow through the hydrophilic micropores-microgrooves channels (PG channels) fabricated by femtosecond laser. The releasing protection mode is designed for the in-situ closure of the PG channels upon encountering external abrasion and impact. The protection mode imparts the Janus membrane robustness to reserve water unidirectional penetration under harsh conditions, such as 2000  cycles mechanical abrasion, 10 days exposure in air and other rigorous tests (sandpaper abrasion, finger rubbing, sand impact and tape peeling). The underlying mechanism of gridded grooves in protecting and enhancing water flow is unveiled. The Janus membrane serves as a fog collector to demonstrate its unwavering mechanical durability in harsh real-world conditions. The presented design strategy could open up new possibilities of Janus membrane in a multitude of applications ranging from multiphase separation devices to fog harvesting and wearable health-monitoring patches.

Velocity-Switched Droplet Rebound Direction on Anisotropic Superhydrophobic Surfaces

Droplet well-controlled directional motion being an essential function has attracted much interest in academic and industrial applications, such as self-cleaning, micro-/nano-electro-mechanical systems, drug delivery, and heat-transferring. Conventional understanding has it that a droplet impacted on an anisotropic surface tends to bounce along the microstructural direction, which is mainly dictated by surface properties rather than initial conditions. In contrast to previous findings, it demonstrates that the direction of a droplet's rebound on an anisotropic surface can be switched by designing the initial impacting velocity. With an increase in impacting height from 2 to 10 cm, the droplet successively shows a backward, vertical, and forward motion on anisotropic surfaces. Theoretical demonstrations establish that the transition of droplet bouncing on the anisotropic surface is related to its dynamic wettability during impacting process. Characterized by the liquid-solid interaction, it is demonstrated that the contact state at small and large impacting heights induces an opposite resultant force in microstructures. Furthermore, energy balance analysis reveals that the energy conversion efficiency of backward motion is almost three times as that of traditional bouncing. This work, including experiments, theoretical models, and energy balance analysis provides insight view in droplet motions on the anisotropic surfaces and opens a new way for the droplet transport.

High-Performance Waterproof, Breathable, and Radiative Cooling Membranes Based on Nanoarchitectured Fiber/Meshworks

Smart membranes with protection and thermal-wet comfort are highly demanded in various fields. Nevertheless, the existing membranes suffer from a tradeoff dilemma of liquid resistance and moisture permeability, as well as poor thermoregulating ability. Herein, a novel strategy, based on the synchronous occurrence of humidity-induced electrospinning and electromeshing, is developed to synthesize a dual-network structured nanofiber/mesh for personal comfort management. Manipulating the ejection, deformation, and phase separation of spinning jets and charged droplets enables the creation of nanofibrous membranes composed of radiative cooling nanofibers and 2D nanostructured meshworks. With a combination of a true-nanoscale fiber (∼70 nm) in 2D meshworks, a small pore size (0.84 μm), and a superhydrophobic surface (151.9°), the smart membranes present high liquid repellency (95.6 kPa), improved breathability (4.05 kg m-2 d-1), and remarkable cooling performance (7.9 °C cooler than commercial cotton fabrics). This strategy opens up a pathway to the design of advanced smart textiles for personal protection.

Accelerated Water Transportation Phenomenon through a Hydrophilic Metal Roll

Passive water transport by taking advantage of capillary forces is vital for various applications such as solar-driven interfacial evaporation, evaporative cooling, and atmospheric water harvesting. Surface engineering and structure design with a hydrophilic surface and enhanced capillary force will facilitate passive water transport. Herein, we demonstrate a hydrophilic Cu/CuO foil-based roll for accelerated water transportation. The roll was fabricated by rolling up a typical 2D Cu/CuO film, which transforms the water climbing behavior by significantly enhancing the capillary force between each Cu/CuO film layer. The simple spatial transformation for a 2D film, from planar foil to 3D structure, has extensively facilitated water transportation performance and broadened its practical application potential. The Cu/CuO film with a blade-like nanostructure and excellent hydrophilicity ensures water supply to a limited area, while the capillary effect between different layers of the Cu/CuO foil extends the water transportation height. Consequently, the Cu/CuO foil-based roll demonstrated a high fluidic transport velocity. This design derived from the 2D planar film can be potentially employed for a large range of applications such as evaporating in a confined space and evaporation-driven energy harvest.

Spontaneous Separation of Immiscible Organic Droplets on Asymmetric Wedge Channels with Hierarchical Microchannels

Spontaneous separation of immiscible organic droplets has substantial research implications for environmental protection and resource regeneration. Compared to the widely explored separation of oil-water mixtures, there are fewer reports on separating mixed organic droplets on open surfaces due to the low surface tension differences. Efficient separation of mixed organic liquids by exploiting the rapid spontaneous transport of droplets on open surfaces remains a challenge. Here, through the fusion of inspiration from the fast droplet transport capability of Sarracenia trichome and the asymmetric wedge channel structure of shorebird beaks, this work proposes a spine with hierarchical microchannels and wedge channels (SHMW). Due to the synergistic effect of capillary force and asymmetric Laplace force, the SHMW can rapidly separate mixed organic droplets into two pure phases without requiring additional energy. In particular, the self-spreading of the oil solution on the open channel surface is utilized to amplify the surface energy difference between two droplets, and SHMW achieves the pickup of oil droplets floating on the surface of the organic solution. The maximum separation efficiency on 3-SHMW can reach 99.63%, and it can also realize the antigravity separation of mixed organic droplets with a surface tension difference as low as 0.87 mN·m-1. Furthermore, SHMW performs controllable separation, oil droplet pickup, and continuous separation and collection of mixed organic droplets. It is expected that this cooperative structure composed of hierarchical microchannels and wedge channels will be realized in resource recovery or chemical reactions in industrial production processes.

Designing a slippery/superaerophobic hierarchical open channel for reliable and versatile underwater gas delivery

Achieving long-term and stable gas manipulation in an aqueous environment is necessary to improve multiphase systems relating to gas/liquid interaction. Inspired by the Pitcher plant and the hummingbird beak, we report a slippery/superaerophobic (SLSO) hierarchical fluid channel for continuous, durable, and flexible gas transport. The immiscible lubricant layer inside the SLSO channel promotes one-year stability of gas transport, and the maximum flux of this open channel can reach 3000 mL h-1. Further integration of a CO2 capturing microchip demonstrates the availability and potential of this gas-manipulating interface, which should provide a valuable platform to develop advanced materials and devices.

Enhanced water transportation on a superhydrophilic serial cycloid-shaped pattern

Spontaneous and directional water transportation (SDWT) is considered as an ideal water transportation method and has a great prospect in the aerospace and ship fields. Nonetheless, the existing SDWT has the limitation of a slow water transportation velocity because of its geometry structure configuration, which hinders the practical application of the SDWT. To overcome this limitation, we developed a new superhydrophilic serial cycloid-shaped pattern (SSCP) which was inspired by the micro-cavity shape of the Nepenthes. First, we experimentally found that the water transportation velocity on the SSCP was faster than that on the superhydrophilic serial wedge-shaped pattern (SSWP) and analyzed the faster water transportation mechanism. Then, the influence of the SSCP parameters on the transportation velocity was investigated by a single-factor experiment. In addition, the water transportation velocity on the SSCP was enhanced to 289 mm s^-1 by combining the single-factor experiment, orthogonal optimization design, streamline junction transition optimization, and pre-wet pattern, which was the fastest in the SDWT. Moreover, the SSCP demonstrated its superior capability in long-distance water transportation, gravity resistant water transportation, heat transfer, and fog collection. This finding shows remarkable application prospects in the high-performance fluid transportation system.

Manufacture of a modular fog harvesting system combining 3D printing and wettability-contrasting patterns

A modular fog harvesting system consisting of a water collection module and a water tank module is designed and manufactured with 3D printing technology and can be assembled like Lego bricks within a reasonable range. Combined with a Namib-beetle-inspired hybrid-patterned surface, this system shows a significant capacity for fog harvesting.

Unidirectional Moisture Delivery via a Janus Photothermal Interface for Indoor Dehumidification: A Smart Roof

Rational control of the humidity in specific environments plays an important role in green building, equipment protection, etc. A smart apparatus that can actively expel inner moisture and largely prevent outer liquid penetration can be highly desirable. Through the integration of the Janus interface with unidirectional liquid manipulation and the solar evaporating layer, here, a Janus solar dehumidifying interface (JSDI) is designed for the switchable moisture management of an indoor environment. By covering with the JSDI roof, the continuous elimination of inner water is achieved via outward condensate delivery and solar evaporation on sunny days. On rainy days, JSDI with a hydrophobic lower surface can largely hamper inward liquid leakage and then spontaneously drain the accumulated water via a siphoning structure. The real-world water evaporation rate via the JSDI is ≈0.38 kg m^-2 h^-1 on an autumn day, showing a promising function of in situ moisture expelling. In addition, the JSDI is made of natural materials that are easy to scale up with a cost of four dollars per square meter. It is envisioned that the JSDI may meet the wide requirements of indoor dehumidification and update the understanding of the integration of Janus interfaces and solar steam generation.

Designing Versatile Superhydrophilic Structures via an Alginate-Based Hydrophilic Plasticene

The rational design of superhydrophilic materials with a controllable structure is a critical component in various applications, including solar steam generation, liquid spontaneous transport, etc. The arbitrary manipulation of the 2D, 3D, and hierarchical structures of superhydrophilic substrates is highly desirable for smart liquid manipulation in both research and application fields. To design versatile superhydrophilic interfaces with various structures, here we introduce a hydrophilic plasticene that possesses high flexibility, deformability, water absorption, and crosslinking capabilities. Through a pattern-pressing process with a specific template, 2D prior fast spreading of liquids at speeds up to 600 mm/s was achieved on the superhydrophilic surface with designed channels. Additionally, 3D superhydrophilic structures can be facilely designed by combining the hydrophilic plasticene with a 3D-printed template. The assembly of 3D superhydrophilic microstructure arrays were explored, providing a promising route to facilitate the continuous and spontaneous liquid transport. The further modification of superhydrophilic 3D structures with pyrrole can promote the applications of solar steam generation. The optimal evaporation rate of an as-prepared superhydrophilic evaporator reached ~1.60 kg·m^-2·h^-1 with a conversion efficiency of approximately 92.96%. Overall, we envision that the hydrophilic plasticene should satisfy a wide range of requirements for superhydrophilic structures and update our understanding of superhydrophilic materials in both fabrication and application.

On-Chip Liquid Manipulation via a Flexible Dual-Layered Channel Possessing Hydrophilic/Hydrophobic Dichotomy

The hydrophilic/hydrophobic cooperative interface provides a smart platform to control liquid distribution and delivery. Through the fusion of flexibility and complex structure, we present a manipulable, open, and dual-layered liquid channel (MODLC) for on-demand mechanical control of fluid delivery. Driven by anisotropic Laplace pressure, the mechano-controllable asymmetric channel of MODLC can propel the directional slipping of liquid located between the paired tracks. Upon a single press, the longest transport distance can reach 10 cm with an average speed of ∼3 cm/s. The liquid on the MODLC can be immediately manipulated by pressing or dragging processes, and versatile liquid-manipulating processes on hierarchical MODLC chips have been achieved, including remote droplet magneto-control, continuous liquid distributor, and gas-producing chip. The flexible hydrophilic/hydrophobic interface and its assembly can extend the function and applications of the wettability-patterned interface, which should update our understanding of complex systems for sophisticated liquid transport.