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A Bionic‐Gill 3D Hydrogel Evaporator with Multidirectional Crossflow Salt Mitigation and Aquaculture Applications

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Advanced Functional Materials
Authors:
Lidian Zhang
Lidian Zhang
Lidian Zhang
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Yu Zhang at Tianjin University
Yu Zhang
Miaomiao Zou at University of Cambridge
Miaomiao Zou
Cunlong Yu at Beihang University (BUAA)
Cunlong Yu
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Abstract and Figures

In recent years, interfacial solar‐driven steam generation has gained huge attention as a sustainable and energy‐efficient technology. However, salt scaling on and inside the evaporator structure induced by insufficient ion distribution control will lower the evaporation performance and hinder the stability and durability of evaporators. Herein, inspired by the highly efficient salt‐expelling property of the gill filaments of large yellow croaker, a bionic‐gill 3D hydrogel evaporator is proposed with fabulous multidirectional ion migration controllability. A 3D structure composed of arrayed beaded hollow columns with beaded hollow holes inspired by gill filaments ensuring longitudinal ion backflow and the peristome‐mimetic arrayed grooves of microcavities ensuring lateral ion advection is designed and constructed to achieve fabulous multidirectional crossflow salt ion migration, which ensures high evaporation performance for pure water (an evaporation rate of 2.53 kg m⁻² h⁻¹ with an energy efficiency of 99.3%) as well as for high salinity brine (2.11 kg m⁻² h⁻¹ for 25.0 wt.% NaCl solution), with no salt crystallizing after long‐term use. Furthermore, the 3D hydrogel evaporator has excellent chemical stability, mechanical properties, folding‐irrelevant evaporation performance, and portability so that it can be used for the preliminary desalination of breeding wastewater through the proposed self‐circulation koi aquaculture system.
Design of the bionic‐gill evaporators. a) Scheme and Micro‐CT images of the gill filaments of the large yellow croaker showing corresponding surface morphology and internal morphology. b) Schematic demonstration of the biomimetic fish gill structures with arrayed beaded hollow columns consisting of inner beaded hollow holes and outer beaded profiles. c) Schematic demonstration of the peristome morphology of the Nepenthes alata. d) Scheme of the bionic peristome surface of the pitcher plant based on arrayed grooves of microcavities. e) Schematic demonstration of the 3D morphology of the bionic‐gill evaporator.
Design of the bionic‐gill evaporators. a) Scheme and Micro‐CT images of the gill filaments of the large yellow croaker showing corresponding surface morphology and internal morphology. b) Schematic demonstration of the biomimetic fish gill structures with arrayed beaded hollow columns consisting of inner beaded hollow holes and outer beaded profiles. c) Schematic demonstration of the peristome morphology of the Nepenthes alata. d) Scheme of the bionic peristome surface of the pitcher plant based on arrayed grooves of microcavities. e) Schematic demonstration of the 3D morphology of the bionic‐gill evaporator.
… 
Fabrication and characterization of the bionic‐gill evaporators. a) Schematic demonstration of the preparation procedures of the bionic‐gill evaporator. b) Optical image of the bottom surface of the bionic‐gill evaporator which is composed of beaded hollow columns. c) Optical image of the top surface of the bionic‐gill evaporator which is composed of arrayed grooves of microcavities structure. d) SEM image of the beaded hollow columns of the bionic‐gill evaporator displaying sparse microscale pores. e) SEM image of the arrayed grooves of microcavities structure of the bionic‐gill evaporator displaying sparse microscale pores. f) SEM image of the beaded hollow columns of the bionic‐gill evaporator showing dense nanoscale pores. g) SEM image of the arrayed grooves of microcavities structure of the bionic‐gill evaporator showing dense nanoscale pores. h) Micro‐CT images of the external surface and the cross sectional morphology of a hollow column with a beaded profile. i) Time sequence optical images of highly‐concentrated (25.0 wt.%) salty water infiltrating process on the bionic‐gill evaporator proving its super‐hydrophilicity. j) FTIR spectra of the PVA/CNFs, PVA, and CNFs showing the chemical composition. Red, blue, and black lines represent the IR absorption spectra of PVA/CNFs, CNFs, and PVA, respectively. k) UV–vis NIR spectra of the bionic‐gill evaporator. Black and red lines represent the absorbance of the evaporator and the spectrum of solar irradiation, respectively.
Fabrication and characterization of the bionic‐gill evaporators. a) Schematic demonstration of the preparation procedures of the bionic‐gill evaporator. b) Optical image of the bottom surface of the bionic‐gill evaporator which is composed of beaded hollow columns. c) Optical image of the top surface of the bionic‐gill evaporator which is composed of arrayed grooves of microcavities structure. d) SEM image of the beaded hollow columns of the bionic‐gill evaporator displaying sparse microscale pores. e) SEM image of the arrayed grooves of microcavities structure of the bionic‐gill evaporator displaying sparse microscale pores. f) SEM image of the beaded hollow columns of the bionic‐gill evaporator showing dense nanoscale pores. g) SEM image of the arrayed grooves of microcavities structure of the bionic‐gill evaporator showing dense nanoscale pores. h) Micro‐CT images of the external surface and the cross sectional morphology of a hollow column with a beaded profile. i) Time sequence optical images of highly‐concentrated (25.0 wt.%) salty water infiltrating process on the bionic‐gill evaporator proving its super‐hydrophilicity. j) FTIR spectra of the PVA/CNFs, PVA, and CNFs showing the chemical composition. Red, blue, and black lines represent the IR absorption spectra of PVA/CNFs, CNFs, and PVA, respectively. k) UV–vis NIR spectra of the bionic‐gill evaporator. Black and red lines represent the absorbance of the evaporator and the spectrum of solar irradiation, respectively.
… 
Evaporation performance of the bionic‐gill evaporators with different paraments. a) Schematic diagram of the system for measuring the evaporation performance of the bionic‐gill evaporators under laboratory conditions. b) Optical image of the experimental set‐up for solar‐driven water evaporation evaluation. c) Scheme of the structural parameters of the beaded hollow columns of the bionic‐gill evaporators including the hole radius and wall thickness. d) Mass change of pure water on the bionic‐gill evaporators with different hole radii under one sun illumination, with the bare liquid surface as control. Green, red, blue, and black lines represent mass change curves of the bionic‐gill evaporators with the hole radius of 0.375, 0.5, and 0.625 mm and the bare liquid surface, respectively. e) Mass change of pure water on the bionic‐gill evaporators with different wall thickness to hole radius ratios under one sun illumination, with the bare liquid surface as control. Purple, green, red, blue, and black lines represent mass change curves of the bionic‐gill evaporators with the hole radius to wall thickness ratios of 1:1, 2:1, 3:1, and 4:1 and the bare liquid surface, respectively. f) The evaporation rates and energy efficiencies of pure water on the bionic‐gill evaporators with different hole radii. Black, blue, and red lines represent the water evaporation rate in darkness, the solar steam generation rate under one sun illumination, and the energy efficiency under one sun illumination, respectively. g) The evaporation rates and energy efficiencies of pure water on the bionic‐gill evaporators with different wall thickness to hole radius ratios. Black, blue, and red lines represent the water evaporation rate in darkness, the solar steam generation rate under one sun illumination, and the energy efficiency under one sun illumination, respectively. h) Top and bottom temperatures of the bionic‐gill evaporators with different hole radii under one sun illumination. Red and black lines represent the top and the bottom temperatures, respectively. The insets are the IR images of corresponding bionic‐gill evaporators. i) Top and bottom temperatures of bionic‐gill evaporators different wall thickness to hole radius ratios under one sun illumination. Red and black lines represent the top and the bottom temperatures, respectively. The insets are the IR images of corresponding bionic‐gill evaporators.
Evaporation performance of the bionic‐gill evaporators with different paraments. a) Schematic diagram of the system for measuring the evaporation performance of the bionic‐gill evaporators under laboratory conditions. b) Optical image of the experimental set‐up for solar‐driven water evaporation evaluation. c) Scheme of the structural parameters of the beaded hollow columns of the bionic‐gill evaporators including the hole radius and wall thickness. d) Mass change of pure water on the bionic‐gill evaporators with different hole radii under one sun illumination, with the bare liquid surface as control. Green, red, blue, and black lines represent mass change curves of the bionic‐gill evaporators with the hole radius of 0.375, 0.5, and 0.625 mm and the bare liquid surface, respectively. e) Mass change of pure water on the bionic‐gill evaporators with different wall thickness to hole radius ratios under one sun illumination, with the bare liquid surface as control. Purple, green, red, blue, and black lines represent mass change curves of the bionic‐gill evaporators with the hole radius to wall thickness ratios of 1:1, 2:1, 3:1, and 4:1 and the bare liquid surface, respectively. f) The evaporation rates and energy efficiencies of pure water on the bionic‐gill evaporators with different hole radii. Black, blue, and red lines represent the water evaporation rate in darkness, the solar steam generation rate under one sun illumination, and the energy efficiency under one sun illumination, respectively. g) The evaporation rates and energy efficiencies of pure water on the bionic‐gill evaporators with different wall thickness to hole radius ratios. Black, blue, and red lines represent the water evaporation rate in darkness, the solar steam generation rate under one sun illumination, and the energy efficiency under one sun illumination, respectively. h) Top and bottom temperatures of the bionic‐gill evaporators with different hole radii under one sun illumination. Red and black lines represent the top and the bottom temperatures, respectively. The insets are the IR images of corresponding bionic‐gill evaporators. i) Top and bottom temperatures of bionic‐gill evaporators different wall thickness to hole radius ratios under one sun illumination. Red and black lines represent the top and the bottom temperatures, respectively. The insets are the IR images of corresponding bionic‐gill evaporators.
… 
Multidirectional crossflow salt mitigation of the bionic‐gill evaporators. a) Comparison of the evaporation performance of evaporators reported by the recent literatures at different salinities. The red flower represents the performance of our bionic‐gill evaporator. The above references are presented in the Supporting Information. b) Evaporation performance and salt endurance of the bionic‐gill evaporator during the 140 h continuous solar desalination with the 25.0 wt.% NaCl solution as the bulk water. The blue dots, the green line, and the red columns represent the temperatures, relative humidity, and evaporation rates, respectively. c) Scheme of the control evaporator structure without inner beaded hollow holes. d) Scheme of the structure of the bionic‐gill evaporator with inner beaded hollow holes. e) Time sequence optical images of the insufficient salt mitigation process on the evaporator without inner beaded hollow holes. f) Time sequence optical images of the sufficient salt mitigation process on the bionic‐gill evaporator. g) The water transport rate and the half‐swollen time of the bionic‐gill evaporator with hollow holes, the bionic‐gill evaporator without hollow holes, and the plane film evaporator. h) Scheme of the distribution of salt concentration measurement sites on the surface of the bionic‐gill evaporator floating on the 25.0 wt.% NaCl solution. Blue and red dots represent the upper hollow hole sites and their surrounding selected test sites on the upper surface of the bionic‐gill evaporator, respectively. Solid square area and dotted ellipse area represent the measured region in (i) and Figure S17 (Supporting Information), respectively. i) Selected areal upper surface salinity distribution of the bionic‐gill evaporator floating on the 25.0 wt.% NaCl solution. j) Numerical simulation result of salt concentration distribution of the bionic‐gill evaporator floating on the 25.0 wt.% NaCl solution. k) The schematic diagram of the mechanism of the multidirectional crossflow salt mitigation of the bionic‐gill evaporator induced by the longitudinal ion backflow and lateral ion advection.
Multidirectional crossflow salt mitigation of the bionic‐gill evaporators. a) Comparison of the evaporation performance of evaporators reported by the recent literatures at different salinities. The red flower represents the performance of our bionic‐gill evaporator. The above references are presented in the Supporting Information. b) Evaporation performance and salt endurance of the bionic‐gill evaporator during the 140 h continuous solar desalination with the 25.0 wt.% NaCl solution as the bulk water. The blue dots, the green line, and the red columns represent the temperatures, relative humidity, and evaporation rates, respectively. c) Scheme of the control evaporator structure without inner beaded hollow holes. d) Scheme of the structure of the bionic‐gill evaporator with inner beaded hollow holes. e) Time sequence optical images of the insufficient salt mitigation process on the evaporator without inner beaded hollow holes. f) Time sequence optical images of the sufficient salt mitigation process on the bionic‐gill evaporator. g) The water transport rate and the half‐swollen time of the bionic‐gill evaporator with hollow holes, the bionic‐gill evaporator without hollow holes, and the plane film evaporator. h) Scheme of the distribution of salt concentration measurement sites on the surface of the bionic‐gill evaporator floating on the 25.0 wt.% NaCl solution. Blue and red dots represent the upper hollow hole sites and their surrounding selected test sites on the upper surface of the bionic‐gill evaporator, respectively. Solid square area and dotted ellipse area represent the measured region in (i) and Figure S17 (Supporting Information), respectively. i) Selected areal upper surface salinity distribution of the bionic‐gill evaporator floating on the 25.0 wt.% NaCl solution. j) Numerical simulation result of salt concentration distribution of the bionic‐gill evaporator floating on the 25.0 wt.% NaCl solution. k) The schematic diagram of the mechanism of the multidirectional crossflow salt mitigation of the bionic‐gill evaporator induced by the longitudinal ion backflow and lateral ion advection.
… 
Purification characterization and practical applications of the bionic‐gill evaporators. a) Concentrations of four primary ions of seawater sample from the Bohai Sea before and after desalination. Pink and blue columns represent the ion concentrations before and after desalination, respectively. The dotted blue line refers to the World Health Organization's (WHO) standards of ion concentrations for drinkable water. b) Concentrations of heavy ion solutions before and after purification. Pink and blue columns represent the ion concentrations before and after desalination, respectively. c) Scheme of the experimental setup for the self‐circulation aquaculture system. d) Concentrations of chroma, turbidity, and salinity of the breeding wastewater sample from the fish tank before and after purification. Green and red regions represent corresponding ion concentrations before and after purification, respectively. e) Concentrations of phosphate, nitrite, nitrate, total nitrogen, and sulfide of the breeding wastewater sample from the fish tank before and after purification, with corresponding ion concentrations of the Chinese national standard as references. Green, red, and orange regions represent corresponding ion concentrations before purification, after purification, and the Chinese national standard, respectively. f) The total mass of koi fishes in two tanks along with aquaculture time. Black and red lines represent the total mass of koi fishes refreshed by the pure water and the purified breeding wastewater, respectively. Insets are optical images of living situations of koi fishes. g) Cell viability test of mouse breast cancer (4T1) cells after culturing in the pure water and the purified breeding wastewater (Sample size n = 11 per group). Comparisons between two groups were analyzed using the unpaired Student's t‐test with one tail at the 95% confidence interval. The obtained data were expressed as the mean values ± standard deviations. Blue and green columns represent the cell viability in the pure water and the purified breeding wastewater, respectively. After culturing, there is no significant (ns) cell viability change in the purified water group compared with the pure water group. h) Optical images of the characterization of the large‐area bionic‐gill evaporator with foldable storage property. i) Mass change curve of the dry and wet evaporators after multiple cycles of hydration and dehydration. Insets are optical images displaying the corresponding evaporator state. j) Chemical stability characterization of the evaporator through elemental analysis. Red, green, and blue columns are the contents of hydrogen, oxygen, and carbon elements of the evaporators, respectively.
Purification characterization and practical applications of the bionic‐gill evaporators. a) Concentrations of four primary ions of seawater sample from the Bohai Sea before and after desalination. Pink and blue columns represent the ion concentrations before and after desalination, respectively. The dotted blue line refers to the World Health Organization's (WHO) standards of ion concentrations for drinkable water. b) Concentrations of heavy ion solutions before and after purification. Pink and blue columns represent the ion concentrations before and after desalination, respectively. c) Scheme of the experimental setup for the self‐circulation aquaculture system. d) Concentrations of chroma, turbidity, and salinity of the breeding wastewater sample from the fish tank before and after purification. Green and red regions represent corresponding ion concentrations before and after purification, respectively. e) Concentrations of phosphate, nitrite, nitrate, total nitrogen, and sulfide of the breeding wastewater sample from the fish tank before and after purification, with corresponding ion concentrations of the Chinese national standard as references. Green, red, and orange regions represent corresponding ion concentrations before purification, after purification, and the Chinese national standard, respectively. f) The total mass of koi fishes in two tanks along with aquaculture time. Black and red lines represent the total mass of koi fishes refreshed by the pure water and the purified breeding wastewater, respectively. Insets are optical images of living situations of koi fishes. g) Cell viability test of mouse breast cancer (4T1) cells after culturing in the pure water and the purified breeding wastewater (Sample size n = 11 per group). Comparisons between two groups were analyzed using the unpaired Student's t‐test with one tail at the 95% confidence interval. The obtained data were expressed as the mean values ± standard deviations. Blue and green columns represent the cell viability in the pure water and the purified breeding wastewater, respectively. After culturing, there is no significant (ns) cell viability change in the purified water group compared with the pure water group. h) Optical images of the characterization of the large‐area bionic‐gill evaporator with foldable storage property. i) Mass change curve of the dry and wet evaporators after multiple cycles of hydration and dehydration. Insets are optical images displaying the corresponding evaporator state. j) Chemical stability characterization of the evaporator through elemental analysis. Red, green, and blue columns are the contents of hydrogen, oxygen, and carbon elements of the evaporators, respectively.
… 
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2300318 (1 of 12)
A Bionic-Gill 3D Hydrogel Evaporator with Multidirectional
Crossflow Salt Mitigation and Aquaculture Applications
Lidian Zhang, Yu Zhang, Miaomiao Zou, Cunlong Yu, Chuxin Li, Can Gao,
Zhichao Dong,* Lei Wu,* and Yanlin Song*
In recent years, interfacial solar-driven steam generation has gained huge
attention as a sustainable and energy-ecient technology. However, salt
scaling on and inside the evaporator structure induced by insucient ion
distribution control will lower the evaporation performance and hinder the
stability and durability of evaporators. Herein, inspired by the highly e-
cient salt-expelling property of the gill filaments of large yellow croaker, a
bionic-gill 3D hydrogel evaporator is proposed with fabulous multidirectional
ion migration controllability. A 3D structure composed of arrayed beaded
hollow columns with beaded hollow holes inspired by gill filaments ensuring
longitudinal ion backflow and the peristome-mimetic arrayed grooves of
microcavities ensuring lateral ion advection is designed and constructed
to achieve fabulous multidirectional crossflow salt ion migration, which
ensures high evaporation performance for pure water (an evaporation rate of
2.53kgm−2h−1 with an energy eciency of 99.3%) as well as for high salinity
brine (2.11kgm−2h−1 for 25.0wt.% NaCl solution), with no salt crystallizing
after long-term use. Furthermore, the 3D hydrogel evaporator has excel-
lent chemical stability, mechanical properties, folding-irrelevant evapora-
tion performance, and portability so that it can be used for the preliminary
desalination of breeding wastewater through the proposed self-circulation koi
aquaculture system.
DOI: 10.1002/adfm.202300318
L. Zhang, Y. Zhang, M. Zou, L. Wu, Y. Song
Key Laboratory of Green Printing
Beijing National Laboratory for Molecular Sciences (BNLMS)
Institute of Chemistry
Chinese Academy of Sciences
Beijing 100190, P. R. China
E-mail: wulei1989@iccas.ac.cn; ylsong@iccas.ac.cn
L. Zhang, Y. Zhang, M. Zou, L. Wu, Y. Song
University of Chinese Academy of Sciences
Beijing 100049, P. R. China
C. Yu, C. Gao, Z. Dong
CAS Key Laboratory of Bio-inspired Materials and Interfacial Sciences
Technical Institute of Physics and Chemistry
Chinese Academy of Sciences
Beijing 100190, P. R. China
E-mail: dongzhichao@mail.ipc.ac.cn
C. Li
Suzhou Institute for Advanced Research
University of Science and Technology of China
Suzhou 215123, P. R. China
C. Li
School of Chemistry and Materials Science
University of Science and Technology of China
Hefei 230026, P. R. China
which are two key factors to evaluate the
solar evaporation performance, the salt-
resistant property is arousing the attention
of researchers coping with the demand
for practical implementation in recent
years. As salt ions gradually concentrate
and eventually crystallize in specific areas,
the evaporation rate and energy eciency
will be decreased leading to poor evapora-
tion performance.[18] The salt crystallization
method[19–21] that relies on regional satura-
tion concentration on evaporation surface
with the requirement of crystallized salt
prompt removal, and the salt ion control
method[22–24] that demands uniform ion
concentration distribution and sucient
salt discharge into the bulk water, are two
pivotal solutions to realizing salt resistance.
As they both involve the control of the salt
ion distribution in the whole system not
only on the evaporation surface but also
inside the bulk water, the manipulation of
salt ion flow is critical for realizing a stable
and durable evaporation process in prac-
tical applications.
The salt ion control method[25] can
actually provide a clean evaporation envi-
ronment for maintaining a sustainable evaporation process
and eliminate the post-treatment processes for salt removal.
It mainly involves the control of water and vapor trans-
port pathways through wettability regulations,[26–28] and the
pathway morphology regulations both on macroscale[9,23,29]
and microscale[30–32] for salt discharge based on salt ion diu-
sion or convection. However, the balance among the regional
salt ion concentration distribution controlled by the pathway
ReseaRch aRticle
1. Introduction
With the growth of the world population, freshwater scarcity is
increasingly seen as a global challenge.[1–3] Interfacial solar-driven
steam generation has gained huge attention[4–7] with solar sources
as the only energy input and low carbon footprint when treating
the seawater or wastewater.[8–11] Along with the extreme promo-
tion of the evaporation rate[12–15] and energy eciency,[8,15–17]
The ORCID identification number(s) for the author(s) of this article
can be found under https://doi.org/10.1002/adfm.202300318.
Adv. Funct. Mater. 2023, 33, 2300318
... This feature enables the evaporation system to maintain a consistent water evaporation rate exceeding 1.45 kg·m −2 ·h −1 in saline water, across a salinity range of 35-200 g·kg −1 . Dong et al. [100], inspired by the excellent salt resistance property of the gill filaments of large yellow croakers and the rapid liquid transport property of the peristome surface of Nepenthes alata, designed a bionic-gill 3D hydrogel ISDE system. This system comprises arrayed beaded hollow columns and an upper surface with arrayed grooves of microcavities (Figure 7b). ...
... (b) Inspired by the large yellow croaker and Nepenthes alata, the bionic-gill 3D hydrogel ISDE system was designed with multidirectional crossflow salt mitigation. Reprinted with permission from ref [100]. Copyright 2023 Wiley-VCH Verlag GmbH. ...
... (b) Inspired by the large yellow croaker and Nepenthes alata, the bionic-gill 3D hydrogel ISDE system was designed with multidirectional crossflow salt mitigation. Reprinted with permission from ref[100]. Copyright 2023 Wiley-VCH Verlag GmbH. ...
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Interfacial evaporation using porous hydrogels has demonstrated highly effective solar evaporation performance under natural sunlight to ensure an affordable clean water supply. However, it remains challenging to realize scalable and ready‐to‐use hydrogel materials with durable mechanical properties. Here, self‐assembled templating (SAT) is developed as a simple yet effective method to fabricate large‐scale elastic hydrogel evaporators with excellent desalination performance. The highly interconnected porous structure of the hydrogels with low tortuosity and tunable pore size enables high level of tunability on the water transport rate. With superior elasticity, the porous hydrogels are easy to process with a rapid shape recovery after being rolled, folded, and twisted over hundred times, and exhibit highly effective and stable evaporation with an evaporation rate of ≈2.8 kg m⁻² h⁻¹ and ≈90 % solar‐to‐vapor efficiency. It is anticipated that this SAT strategy, without the typical need for freeze‐drying, will accelerate the industrialization of hydrogel solar evaporators for practical applications.
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Rational Design of a High Performance and Robust Solar Evaporator via 3D‐Printing Technology
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Utilizing the broad-band solar spectrum for sea water desalination is a promising method that can provide fresh water without sophisticated infrastructures. However, the solar-to-vapour efficiency has been limited due to the lack of a proper design for the evaporator to deal with either a large amount of heat loss or salt accumulation. Here, these issues are addressed via two cost-effective approaches: I) a rational design of a concave shaped supporter by 3D-printing that can promote the light harvesting capacity via multiple reflections on the surface; II) the use of a double layered photoabsorber composed of a hydrophilic bottom layer of a polydopamine (PDA) coated glass fiber (GF/C) and a hydrophobic upper layer of a carbonized poly(vinyl alcohol)/polyvinylpyrrolidone (PVA/PVP) hydrogel on the supporter, which provides competitive benefit for preventing deposition of salt while quickly pumping the water. The 3D-printed solar evaporator can efficiently utilize solar energy (99%) with an evaporation rate of 1.60 kg m–2 h–1 and efficiency of 89% under 1 sun irradiation. The underlying reason for the high efficiency obtained is supported by the heat transfer mechanism. The 3D-printed solar evaporator could provide cheap drinking water in remote areas, while maintaining stable performance for a long term.
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Molecular Engineering of Hydrogels for Rapid Water Disinfection and Sustainable Solar Vapor Generation
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Consumption of unsafe water is a major cause of morbidity and mortality in developing regions. Pasteurizing or boiling water to remove pathogens is energy‐intensive and often impractical to off‐grid communities. Therefore, low capital cost, rapid and energy‐efficient water disinfection methods are urgently required to address global challenges of safe water access. Here, anti‐bacterial hydrogels (ABHs) with catechol‐enabled molecular‐level hydrogen peroxide generators and quinone‐anchored activated carbon particles are designed for effective water treatment. The bactericidal effect is attributed to the synergy of hydrogen peroxide and quinone groups to attack essential cell components and disturb bacterial metabolism. ABHs can be directly used as tablets to achieve >99.999% water disinfection efficiency within 60 min without energy input. No harmful byproducts are formed during the treatment process, after which the ABH tablets can be easily removed without residues. Taking advantage of their excellent photothermal and biofouling‐resistant properties, ABHs can also be applied as solar evaporators to achieve stable water purification under sunlight (≤1 kW m−2) after months of storage and operation in bacteria‐containing river water. The ABH platform offers reduced energy and chemical demands for point‐of‐use water treatment technologies in remote areas and emergency rescue applications. Anti‐bacterial hydrogels (ABHs) are designed as tablets for rapid water disinfection (>99.999%) and can be easily removed from the water without leaving chemical impurities. With excellent photothermal and biofouling‐resistant properties, ABHs can also be functional in solar water purification technologies to enable stable distillate production after months of storage and operation in bacteria‐containing river water.
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3D Printing a Biomimetic Bridge‐Arch Solar Evaporator for Eliminating Salt Accumulation with Desalination and Agricultural Applications
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Solar‐driven water evaporation has been considered a sustainable method to obtain clean water through desalination. However, its further application is limited by the complicated preparation strategy, poor salt rejection, and durability. Herein, inspired by superfast water transportation of the Nepenthes alata peristome surface and continuous bridge‐arch design in architecture, a biomimetic 3D bridge‐arch solar evaporator is proposed to induce Marangoni flow for long‐term salt rejection. The formed double‐layer 3D liquid film on the evaporator is composed of a confined water film for water supplementation and a free‐flowing water film with ultrafast directional Marangoni convection for salt rejection, which functions cooperatively to endow the 3D evaporator with all‐in‐one function including superior solar‐driven water evaporation (1.64 kg m‐2 h‐1, 91% efficiency for pure water), efficient solar desalination, and long‐term salt‐rejecting property (continuous 200 h in 10 wt% saline water) without any post‐cleaning treatment. The design principle of the 3D structures is provided for extending the application of Marangoni‐driven salt rejection and the investigation of structure‐design‐induced liquid film control in the solar desalination field. Furthermore, excellent mechanical and chemical stability is proved, where a self‐sustainable and solar‐powered desalination–cultivation platform is developed, indicating promising application for agricultural cultivation. A novel biomimetic 3D solar evaporator for efficient interfacial water evaporation is constructed inspired by the superfast liquid transportation property of the peristome surface of Nepenthes alata and an arch bridge design. With peristome‐mimetic microstructures as water transportation channels, a double‐layer water film is formed to eliminate salt accumulation, ensure long‐term evaporation, and develop self‐sustainable agricultural cultivation.
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All-day fresh water harvesting by microstructured hydrogel membranes
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  • May 2021
Solar steam water purification and fog collection are two independent processes that could enable abundant fresh water generation. We developed a hydrogel membrane that contains hierarchical three-dimensional microstructures with high surface area that combines both functions and serves as an all-day fresh water harvester. At night, the hydrogel membrane efficiently captures fog droplets and directionally transports them to a storage vessel. During the daytime, it acts as an interfacial solar steam generator and achieves a high evaporation rate of 3.64 kg m−2 h−1 under 1 sun enabled by improved thermal/vapor flow management. With a homemade rooftop water harvesting system, this hydrogel membrane can produce fresh water with a daily yield of ~34 L m−2 in an outdoor test, which demonstrates its potential for global water scarcity relief. Solar steam water purification and fog collection are two independent processes that could enable abundant fresh water generation. Here, the authors develop a hydrogel membrane that contains microstructures and combines both functions and serves as an all-day fresh water harvester.
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Best practices for solar water production technologies
Article
  • Apr 2022
We need consensus to accurately evaluate the performance and potential of emerging water production technologies, such as solar evaporation and atmospheric water harvesting. Here we recommend practices that would allow a fair basis to compare different studies, and help to align research input with actual demand.
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Sustainable off-grid desalination of hypersaline waters using Janus wood evaporators
Article
  • Jan 2021
A sustainable Janus wood evaporator with asymmetric surface wettability shows persistent salt-resistance for off-grid hypersaline waters desalination.
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