A robust and 3D-printed solar evaporator based on naturally occurring molecules

Natural-inspired hierarchic double-Janus solar evaporator for stable clean water production from high-salinity emulsions

Interfacial solar evaporation shows great potential in clean water production, emulsions separation, and high-salinity brine treatment. However, it remains challenging for the evaporators to maintain a high evaporation rate in the high-salinity emulsions due to the co-pollution of salt and oil. Herein, we first proposed a hierarchic double-Janus solar evaporator (HDJE) with a hydrophobic salt-rejecting top layer and oil-rejecting bottom layer. Compared to the traditional one, HDJE could treat industrial high-salinity oil-in-water emulsions stably for over 70 h, with a stable average evaporation rate of 1.73 kg m-2 h-1 and a high purification efficiency of up to 99.8 % for oil and ions. It was also verified that HDJE could be used for high-efficiency purification of oily concentrated seawater outdoor. An average water production rate of 3.59 kg m-2 d-1 and a TOC removal ratio of over 98 % was obtained. In conclusion, this study provides a novel way to effectively dispose of high-salinity oily wastewater.

Bioinspired 1T-MoS2-based aerogel beads for efficient freshwater harvesting in harsh environments

Freshwater scarcity is one of the most critical issues worldwide, particularly in arid regions, stemming from population growth and climate change. Inspired by the hydrophilic bump structures of desert beetles, 1T-MoS2-based aerogel beads with porous structures and CaCl2-crystal loading (termed as MoAB-m@CaCl2-n) were prepared for freshwater harvesting. Metallic-phase MoS2 nanospheres exhibit excellent photothermal conversion abilities, facilitating solar-driven water desorption and evaporation. Owing to the synergistic effect of its localized surface features, hydrophilic groups, and dispersive CaCl2 particles, MoAB-2@CaCl2-2 efficiently harvests water from atmosphere with a superior moisture adsorption capacity (0.18-0.82 g g-1) at a wide range of relative humidity (10 %-70 %). Under one-sun illumination, MoAB-2@CaCl2-2 demonstrates an outstanding solar-driven water evaporation rate of 2.25 kg m-2h-1. The water evaporation rate from soil (water content = 20 %) is 1.19 kg m-2h-1, which is sufficient for sustainable freshwater generation from the soil in arid regions. More importantly, the multifunctional MoAB-2@CaCl2-2-based homemade freshwater generation prototype delivers a certain amount of water harvesting (0.99 g g-1 day-1) on a rainy day and provides an impressive daily freshwater yield (53.7 kg m-2) under natural sunlight. The integrated device exhibits excellent efficiency and practicality and offers a feasible method for freshwater harvesting in harsh environments.

Biomimic Design of Solar Steam Generation Devices Enabled by the Tannin-Iron Complex

Solar-powered steam generation equipment has experienced considerable advancement in recent years as it offers a cleaner and greener method for freshwater production. However, the devices always suffer from a complicated process, high cost, and salt accumulation, which hinder their further application. Here, inspired by the water lily, a highly efficient and antisalt accumulation interfacial solar-driven steam generation device was designed by using the tannic acid-Fe3+ complex as photothermal material. The designed evaporator could be quickly unfolded within 24 s after being irradiated with light and then produce fresh water. It folded within 10 s and then sank into water for removing the accumulated salt after removing the irradiation sources. In addition, the tannic acid-Fe3+ complex on the evaporator surface and the angle of the evaporator allowed light to be reflected several times within the evaporator, effectively increasing the solar energy conversion efficient (2.22 kg/(m2·h)), and apparently, the overall evaporation efficiency of 139.18% was achieved under 1 sun illumination. Moreover, it exhibited an extraordinary antisalt accumulation capacity (by working continuously for 7 days in 10 wt % saline water and 80% reduction in salt accumulation) as well as a low price ($ 1.11/m2). This design would provide a strategy to prepare an antisalt accumulation solar steam devices.

Well-designed lamellar reduced graphene oxide-based foam for high-performance solar-driven water purification

Although solar steam generation is promising for seawater desalination, it is less effective in purifying wastewater with both salt/heavy metal ions and organic contaminants. It is thus imperative to develop multifunctional integrated solar-driven water purification systems with high solar-thermal evaporation and photocatalytic degradation efficiencies. Herein, a lamellar reduced graphene oxide (L-RGO) foam with the vertical lamellar structure is fabricated by bidirectional-freezing, lyophilization, and slight chemical reduction for water purification. The unique vertical lamellar structure not only accelerates upward transport of water for facilitating water evaporation but also endows the L-RGO foam with superb high elasticity for tuning the interlayer distance and varying interactions between the oxygen-containing groups and water molecules to adjust water energy state. As a result, the L-RGO foam achieves a superb water evaporation rate of 2.40 kg m-2 h-1 along with an energy efficiency of 95.3 % under the compressive strain of 44.7 % under 1-sun irradiation. Equally importantly, the decoration of L-RGO foam with polypyrrole is capable of efficiently degrading organic pollutants while retaining high solar steam generation performances, exhibiting great potential in the comprehensive treatment of various water sources for relieving freshwater crisis.

Bioinspired cytomembrane coating besieges tumor for blocking metabolite transportation

The metabolite transport inhibition of tumor cells holds promise to achieve anti-tumor efficacy. Herein, we presented an innovative strategy to hinder the delivery of metabolites through the in-situ besieging tumor cells with polyphenolic polymers that strongly adhere to the cytomembrane of tumor cells. Simultaneously, these polymers underwent self-crosslinking under the induction of tumor oxidative stress microenvironment to form an adhesive coating on the surface of the tumor cells. This polyphenol coating effectively obstructed glucose uptake, reducing metabolic products such as lactic acid, glutathione, and adenosine triphosphate, while also causing reactive oxygen species to accumulate in the tumor cells. The investigation of various tumor models, including 2D cells, 3D multicellular tumor spheroids, and xenograft tumors, demonstrated that the polyphenolic polymers effectively inhibited the growth of tumor cells by blocking key metabolite transport processes. Moreover, this highly adhesive coating could bind tumor cells to suppress their metastasis and invasion. This work identified polyphenolic polymers as a promising anticancer candidate with a mechanism by impeding the mass transport of tumor cells.

Salt-rejecting 3D cone flowing evaporator based on bilayer photothermal paper for high-performance solar seawater desalination

Solar energy-driven water evaporation technology is a promising, low-cost and sustainable approach to alleviate the global clean water shortage, but usually suffers from low water evaporation rate and severe salt deposition on the water evaporation surface. In this work, a hydrophilic bilayer photothermal paper-based three-dimensional (3D) cone flowing evaporator was designed and prepared for stable high-performance seawater desalination with excellent salt-rejecting ability. The as-prepared bilayer photothermal paper consisted of MXene (Ti3C2Tx) and HAA (ultralong hydroxyapatite nanowires, poly(acrylic acid), and poly(acrylic acid-2-hydroxyethyl ester)). The accordion-like multilayered MXene acted as the efficient solar light absorber, and ultralong hydroxyapatite (HAP) nanowires served as the thermally insulating and supporting skeleton with a porous networked structure. A siphon effect-driven unidirectional fluid transportation unit in the 3D cone flowing evaporator could guide the concentrated saline flowing away from the evaporating surface to prevent salt deposition on the evaporation surface, avoiding severe deterioration of the performance in solar water evaporation. Furthermore, combining high solar light absorption and high photothermal conversion efficiencies, low water evaporation enthalpy (1838 ± 11 J g-1), and additional energy taken from the ambient environment, the as-prepared cone flowing evaporator exhibited a high water evaporation rate of 3.22 ± 0.20 kg m-2 h-1 for real seawater under one sun illumination (1 kW m-2), which was significantly higher than many values reported in the literature. This study provides an effective approach for designing high-performance solar energy-driven water evaporators for sustainable seawater desalination and wastewater purification.

Magnetically driven Janus conical vertical array for all-weather freshwater collection

The engineering of multifunctional structures with special surface wettability is highly desirable for all-weather freshwater production, but relevant research is scarce. In this study, a Janus conical vertical array was designed and fabricated via a magnetically driven spray-coating method for the first time. Benefiting from the special structure and wettability enhancement of the array in terms of solar absorption, fog capture and merging, droplet movement and evaporation area, all-weather freshwater production consisting of high-quality daytime solar vapor generation (water evaporation rate approximately 2.43 kg m-2 h-1, 1 kW m-2) and nighttime fog collection (water collection rate approximately 3.536 g cm-2 h-1) can be realized concurrently. When the designed array is employed for outdoor environments (114°35'E, 30°38'N, average daily temperature 34.9 °C, average daily humidity 64.0%), reliable and efficient daily pure water yields of 19.13 kg m-2-26.09 kg m-2 are obtainable. We believe that the proposed strategy for fabricating a Janus conical vertical array is novel in the integration of solar vapor generation and fog collection, which has great significance for all-weather freshwater production.

Recent Advances of Green Electricity Generation: Potential in Solar Interfacial Evaporation System

Solar-driven interfacial evaporation (SDIE) has played a pivotal role in optimizing water-energy utilization, reducing conventional power costs, and mitigating environmental impacts. The increasing emphasis on the synergistic cogeneration of water and green electricity through SDIE is particularly noteworthy. However, there is a gap of existing reviews that have focused on the mechanistic understanding of green power from water-electricity cogeneration (WEC) systems, the structure-activity relationship between efficiency of green energy utilization in WEC and material design in SDIE. Particularly, it lacks a comprehensive discussion to address the challenges faced in these areas along with potential solutions. Therefore, this review aims to comprehensively assess the progress and future perspective of green electricity from WEC systems by investigating the potential expansion of SDIE. First, it provides a comprehensive overview about material rational design, thermal management, and water transportation tunnels in SDIE. Then, it summarizes diverse energy sources utilized in the SDIE process, including steaming generation, photovoltaics, salinity gradient effect, temperature gradient effect, and piezoelectric effect. Subsequently, it explores factors that affect generated green electricity efficiency in WEC. Finally, this review proposes challenges and possible solution in the development of WEC.

3-Dimentional printing of polysaccharides for water-treatment: A review

Biological polysaccharides such as cellulose, chitin, chitosan, sodium alginate, etc., serve as excellent substrates for 3D printing due to their inherent advantages of biocompatibility, biodegradability, non-toxicity, and absence of secondary pollution. In this review we comprehensively overviewed the principles and processes involved in 3D printing of polysaccharides. We then delved into the diverse application of 3D printed polysaccharides in wastewater treatment, including their roles as adsorbents, photocatalysts, biological carriers, micro-devices, and solar evaporators. Furthermore, we assessed the technical superiority and future potential of polysaccharide 3D prints, envisioning its widespread application. Lastly, we remarked the challenging scientific and engineering aspects that require attention in the scientific research, industrial production, and engineering utilization. By addressing these key points, we aimed to advance the field and facilitate the practical implementation of polysaccharide-based 3D printing technologies in wastewater treatment and beyond.

Waste Tea-Derived Theabrownins for Solar-Driven Steam Generation

Solar-driven seawater desalination has been considered an effective and sustainable solution to mitigate the global freshwater crisis. However, the substantial cost associated with photothermal materials for evaporator fabrication still hinders large-scale manufacturing for practical applications. Herein, we successfully obtained high yields of theabrownins (TB), which were oxidation polymerization products of polyphenols from waste and inferior tea leaves using a liquid-state fermentation strategy. Subsequently, a series of photothermal complexes were prepared based on the metal-phenolic networks assembled from TB and metal ions (Fe(III), Cu(II), Ni(II), and Zn(II)). Also, the screened TB@Fe(III) complexes were directly coated on a hydrophilic poly(vinylidene fluoride) (PVDF) membrane to construct the solar evaporation device (TB@Fe(III)@PVDF), which not only demonstrated superior light absorption property and notable hydrophilicity but also achieved a high water evaporation rate of 1.59 kg m-2 h-1 and a steam generation efficiency of 90% under 1 sun irradiation. More importantly, its long-term stability and exceptionally low production cost enabled an important step toward the possibility of large-scale practical applications. We believe that this study holds the potential to pave the way for the development of sustainable and cost-effective photothermal materials, offering new avenues for utilization of agriculture resource waste and solar-driven water remediation.

Exploring the Potentials of Chitin and Chitosan-Based Bioinks for 3D-Printing of Flexible Electronics: The Future of Sustainable Bioelectronics

Chitin and chitosan-based bioink for 3D-printed flexible electronics have tremendous potential for innovation in healthcare, agriculture, the environment, and industry. This biomaterial is suitable for 3D printing because it is highly stretchable, super-flexible, affordable, ultrathin, and lightweight. Owing to its ease of use, on-demand manufacturing, accurate and regulated deposition, and versatility with flexible and soft functional materials, 3D printing has revolutionized free-form construction and end-user customization. This study examined the potential of employing chitin and chitosan-based bioinks to build 3D-printed flexible electronic devices and optimize bioink formulation, printing parameters, and postprocessing processes to improve mechanical and electrical properties. The exploration of 3D-printed chitin and chitosan-based flexible bioelectronics will open new avenues for new flexible materials for numerous industrial applications.

3D-Printed Liquid Metal-in-Hydrogel Solar Evaporator: Merging Spectrum-Manipulated Micro-Nano Architecture and Surface Engineering for Solar Desalination

Solar desalination driven by interfacial heating is considered a promising technique to alleviate the freshwater shortage crisis. However, its further extension and application are confined by factors such as highlighted salt accumulation, inferior energy efficiency, and poor durability. Herein, a microsized eutectic gallium-indium (EGaIn) core-shell nanodroplet (denoted as LMTE) with photo-cross-linking and photothermal traits, stabilized by allyl glycidyl ether (AGE)-grafting tannic acid (TA), is explored as the solar absorber for broadband light absorbing and localized micro-nano heat channeling. The LMTE nanodroplets are formulated directly with highly hydrated polymers and photosensitive species to successfully develop a water-based photothermal ink suitable for digital light processing (DLP) 3D printing. As a demonstration, the LMTE composite hydrogel-forged milli-conical needle arrays with metal-phenolic network (MPN)-engineered wettability and photothermal enhancement can be printed by the digital light processing (DLP) technique and designed rationally via a bottom-up strategy. The 3D-printing hydrogel evaporator is composed of spectrum-tailored EGaIn nanodroplets for efficient photon harvesting and MPN-coated milli-cone arrays for water supplying with micro-nano channeling, which function cooperatively to bestow the 3D solar evaporator with superior solar-powered water evaporation (2.96 kg m-2 h-1, 96.93% energy efficiency) and excellent solar desalination (salt cycle and site-specific salt crystallization). Furthermore, a robust steam generating/collecting system of the 3D solar evaporator is demonstrated, providing valuable guidance for building a water-energy-agriculture nexus.

Bioinspired Graphene Aerogels with Hybrid Wettability for Solar-Driven Purification of Complex Wastewater

Salt deposition and pollutant enrichment greatly hamper efficient and sustainable water production for a solar evaporator. Inspired by the desert beetle, a dual-region hydrophobic graphene/hydrophilic titanium dioxide (TiO2) aerogel (GTA) with internal hydrophilic-hydrophobic hybrid wettability structure is prepared via a facile freeze-drying and thermal reduction method. The evaporator shows adjustable wettability, optimized water content, and a low energy loss in the evaporation process. Simultaneously, the hybrid wetting structure in aerogel subjects salt to a dynamic crystallization-dissolution process to prevent salt deposition. The GTA solar evaporator achieves an evaporation rate of 1.52 kg·m-2·h-1 with a 91.02% efficiency under 1 sun irradiation. Furthermore, GTAs achieve a stable evaporation rate in high salinity brine (25 wt % NaCl) under 1 sun irradiation for 100 h, which could compete well with other most advanced photothermal evaporation materials. Moreover, the synergistic effect of graphene and TiO2 endows GTAs with excellent photocatalytic degradation and self-cleaning properties, which can effectively reduce the enrichment of contaminants on the evaporator. Therefore, GTA evaporators can efficiently and stably obtain clean water from seawater and wastewater, which provides a feasible strategy for the purification of complex wastewater.

All-in-one self-floating porous foams as robust heat-blocking layers for efficient photothermal conversion and solar desalination

Solar-driven interfacial evaporation is a highly efficient and ecofriendly technology for producing freshwater. Herein, self-floating plasmon Ag/black TiO2/carbon porous layered foams (Ag-BTCFs) were demonstrated as efficient solar-thermal convectors using freeze-drying cast-molding and high-temperature surface hydrogenation strategies. This all-in-one three-dimensional (3D) cross-linked self-floating porous layered foam material with full-spectrum absorption can fully harvest sunlight (∼95.45%) and effectively block heat transfer to its sublayer. The synergy of sufficient utilization of absorbed ultraviolet radiation by black TiO2 (b-TiO2), visible light absorption by Ag nanoparticles (Ag NPs) via localized surface plasmon resonance, and near-infrared absorption by layered-amorphous carbon can achieve full-solar-spectrum absorption to concentrate thermal energy. In addition to their synergistic effect, they are conducive to the relaxation of hot electrons when utilizing photogenerated holes to degrade pollutants in domestic wastewater. The steam generation efficiency of Ag-BTCFs is up to 1.79 kg m-2h-1 due to their solar energy conversion efficiency of 81.74% under 1 sun irradiation, which is five times higher than the evaporation rate of pure water. Notably, the material's efficient ion removal rate of 99.80% for solar desalination indicates its high potential for various applications. This strategy provides new insights for fabricating recyclable heat-blocking layer systems against thermal loss to enhance solar steam generation.

A Multifunctional Asymmetric Fabric for Sustained Electricity Generation from Multiple Sources and Simultaneous Solar Steam Generation

Harvesting electrical energy from water and moisture has emerged as a novel ecofriendly energy conversion technology. Herein, a multifunctional asymmetric polyaniline/carbon nanotubes/poly(vinyl alcohol) (APCP) that can produce electric energy from both saline water and moisture and generate fresh water simultaneously is developed. The constructed APCP possesses a negatively charged porous structure that allows continuous generation of protons and ion diffusion through the material, and a hydrophilicity-hydrophobic interface which results in a constant potential difference and sustainable output. A single APCP can maintain stable output for over 130 h and preserve a high voltage of 0.61 V, current of 81 µA, and power density of 82.4 µW cm-3 with 0.15 cm3 unit size in the water-induced electricity generation process. When harvesting moisture energy, the APCP creates dry-wet asymmetries and triggers the spontaneous development of electrical double layer with a current density of 1.25 mA cm-3 , sufficient to power small electronics. A device consisting of four APCP can generate stable electricity of 3.35 V and produce clean water with an evaporation rate of 2.06 kg m-2  h-1 simultaneously. This work provides insights into the fabrication of multifunctional fabrics for multisource energy harvesting and simultaneous solar steam generation.

Waterwheel-inspired rotating evaporator for efficient and stable solar desalination even in saturated brine

Solar desalination is one of the most promising technologies to address global freshwater shortages. However, traditional evaporators encounter the bottleneck of reduced evaporation rate or even failure due to salt accumulation in high-salinity water. Inspired by ancient waterwheels, we have developed an adaptively rotating evaporator that enables long-term and efficient solar desalination in brines of any concentration. The evaporator is a sulphide-loaded drum-type biochar. Our experiments and numerical simulations show that this evaporator, thanks to its low density and unique hydrophilic property, rotates periodically under the center-of-gravity shift generated by salt accumulation, achieving self-removal of salt. This allows it to maintain a high evaporation rate of 2.80 kg m-2 h-1 within 24 h even in saturated brine (26.47%), which was not achieved previously. This proof-of-concept work therefore demonstrates a concentration- and time-independent, self-rotation-induced solar evaporator.

An injectable all-small-molecule dynamic metallogel for suppressing sepsis

All-small-molecule dynamic hydrogels have shown great promise in cell culture, tissue engineering, and controlled drug release. The further development of more kinds of all-small-molecule dynamic hydrogels is severely hindered by the lack of enough commensurate building blocks from nature and on the market. Inspired by the widely developed metal-organic framework structures, herein we report a facile fabrication of metallogels by direct gelation of small molecular compounds including aminoglycosides (AGs), 2,2'-bipyridine-4,4'-dicarboxaldehyde (BIPY), and metal ions via coordination interactions and Schiff base reactions. These prepared metallogels exhibited good biodegradability and biosafety, excellent conductivity, tunable mechanical properties and potent antibacterial activities both in vitro and in vivo. This study provides a new strategy for expanding the scope of all-small-molecule dynamic metallogels for various biomedical applications.

Dual-Functional Solar-to-Steam Generation and SERS Detection Substrate Based on Plasmonic Nanostructure

Solar-to-steam (STS) generation based on plasmonic materials has attracted significant attention as a green method for producing fresh water. Herein, a simple in situ method is introduced to fabricate Au nanoparticles (AuNPs) on cellulose filter papers as dual-functional substrates for STS generation and surface-enhanced Raman spectroscopy (SERS) sensing. The substrates exhibit 90% of broadband solar absorption between 350 and 1800 nm and achieve an evaporation rate of 0.96 kg·m^-2·h^-1 under 1-sun illumination, room temperature of 20 °C, and relative humidity of 40%. The STS generation of the substrate is stable during 30 h continuous operation. Enriched SERS hotspots between AuNPs endow the substrates with the ability to detect chemical contamination in water with ppb limits of detection for rhodamine 6G dye and melamine. To demonstrate dual-functional properties, the contaminated water was analyzed with SERS and purified by STS. The purified water was then analyzed with SERS to confirm its purity. The developed substrate can be an improved and suitable candidate for fresh water production and qualification.

Introducing Semi-Interpenetrating Networks of Chitosan and Ammonium-Quaternary Polymers for the Effective Removal of Waterborne Pathogens from Wastewaters

The present work aims to study the influence of ammonium-quaternary monomers and chitosan, obtained from different sources, upon the effect of semi-interpenetrating polymer network (semi-IPN) hydrogels upon the removal of waterborne pathogens and bacteria from wastewater. To this end, the study was focused on using vinyl benzyl trimethylammonium chloride (VBTAC), a water-soluble monomer with known antibacterial properties, and mineral-enriched chitosan extracted from shrimp shells, to prepare the semi-IPNs. By using chitosan, which still contains the native minerals (mainly calcium carbonate), the study intends to justify that the stability and efficiency of the semi-IPN bactericidal devices can be modified and better improved. The new semi-IPNs were characterized for composition, thermal stability and morphology using well-known methods. Swelling degree (SD%) and the bactericidal effect assessed using molecular methods revealed that hydrogels made of chitosan derived from shrimp shell demonstrated the most competitive and promising potential for wastewater (WW) treatment.