3D-Printed Anti-Fouling Cellulose Mesh for Highly Efficient Oil/Water Separation Applications

Direct Ink Writing 3D Printing Polytetrafluoroethylene/Polydimethylsiloxane Membrane with Anisotropic Surface Wettability and Its Application in Oil-Water Separation

Biological surfaces with physical discontinuity or chemical heterogeneity possess special wettability in the form of anisotropic wetting behavior. However, there are several challenges in designing and manufacturing samples with anisotropic wettability. This study investigates the fabrication of PTFE/PDMS grid membranes using Direct Ink Writing (DIW) 3D printing for oil-water separation applications. The ink's rheological properties were optimized, revealing that a 60% PTFE/PDMS composite exhibited the ideal shear-thinning behavior for 3D printing. Our research investigated the interplay between various printing parameters like the extrusion air pressure, layer thickness, feed rate, and printing speed, which were found to influence the filament dimensions, pore sizes, and hydrophobic properties of the grid membrane. Two distinct grid structures were analyzed for their wettability and anisotropic hydrophobic characteristics. The grid membranes achieved up to 100% oil-water separation efficiency in specific configurations. Separation efficiency was shown to be dependent on factors like intrusion pressure, grid architecture, and the number of layers. This study underscores the potential of DIW 3D printing in creating specialized surfaces with controlled wettability, particularly superhydrophobicity and anisotropy, paving the way for advanced environmental applications such as efficient oil-water separation.

Digital Light Processing (DLP) 3D Printing Fabrication of Hydrophobic Meshes Incorporating Fluorinated and Silicone-Based Acrylates Combined with Surface Engineering: Comparison of Their Oil-Water Separation Efficiency

Hydrophobic materials have been fabricated by DLP vat photopolymerization of isobornyl acrylate-based resins with chemical modification and/or surface geometry engineering. Fluorinated and polydimethylsiloxane (PDMS)-based acrylic monomers are used for chemical modification and are incorporated into the printed materials. The water wettability was significantly reduced and plateaued with as low as 5% (w/w) of the auxillary hydrophobic monomer. Regarding surface geometry, meshes with different pore sizes are 3D printed, and the surface hydrophobicity increased with the pore size. We compare the oil-water separation efficiency of the 3D-printed meshes hydrophobized by these three approaches. It was found that the isobornyl acrylate-based resin already demonstrated separation at the optimum pore size. Modification with PDMS showed a further improvement in separation efficiency, whereas no significant increase was observed by use of the fluorinated monomer. This highlights that careful design of surface geometry should be considered to avoid the use of environmentally unfriendly and potentially toxic chemicals when making hydrophobic materials.

An overview of cellulose aerogels and foams for oil sorption: Preparation, modification, and potential of 3D printing

Sorption is one of the most efficient methods to remediate the increasing oil spill incidents, but the currently available absorbents are inadequate to tackle such a global threat. Recently, numerous researchers have attempted to develop sustainable oil sorbents. Cellulose aerogels and foams, a type of lightweight porous material with excellent sorption performance, are one of the most promising candidates. Significant progress has been made in the past decade towards the development of cellulose porous materials as effective oil sorbents, with improvements in their oil sorption capacity, reusability, and enhanced multifunctionality, indicating their potential for oil spill remediation. This article reviews recent reports and provides a comprehensive overview of the preparation and modification strategies for cellulose porous materials, with a specific emphasis on their oil sorption performance and structure control. We also focus on the burgeoning 3D printing technology within this field, summarizing the latest advances with a discussion of the potential for using 3D printing to customize and optimize the structure of cellulose porous materials. Lastly, this review addresses current limitations and outlines future directions for development.

Low vaporization enthalpy of modified chitosan hydrogel for high performance solar evaporator

The high vaporization enthalpy of water attributed to the strong hydrogen bonds between water molecules is limiting the performance of solar evaporators. This work demonstrates a deliberate attempt to significantly reduce the vaporization enthalpy of water through the introduction of weak water-amine hydrogen bond interactions in hydrogel evaporators. In this article, bio-based chitosan-agarose/multiwalled carbon nanotube hydrogel film evaporators (CAMFEs) exhibit larger vaporization enthalpy reduction with the presence of primary amine groups in chitosan. An interplay between vaporization enthalpy reduction and water diffusivity leads to an optimal ratio of chitosan to agarose = 7:1 (CAMFE7) showing an impressive evaporation rate of 4.13 kg m-2 h-1 under 1 sun irradiation. CAMFE7 also exhibits excellent salt resistance, with a stable water evaporation rate, using brine water of up to 10 % salinity under continuous 1 sun irradiation. The high mechanical robustness together with its scalability makes CAMFE7 a highly promising material for practical drinking water production.

Reprogrammable, Sustainable, and 3D-Printable Cellulose Hydroplastic

Modern human societies are highly dependent on plastic materials, however, the bulk of them are non-renewable commodity plastics that cause pollution problems and consume large amounts of energy for their thermal processing activities. In this article, a sustainable cellulose hydroplastic material and its composites, that can be shaped repeatedly into various 2D/3D geometries using just water are introduced. In the wet state, their high flexibility and ductility make it conducive for the shaping to take place. In the ambient environment, the wet hydroplastic transits spontaneously into rigid materials with its intended shape in a short time of <30 min despite a thickness of hundreds of microns. They also possess humidity resistance and are structurally stable in highly humid environments. Given their excellent mechanical properties, geometry reprogrammability, bio-based, and biodegradable nature, cellulose hydroplastic poses as a sustainable alternative to traditional plastic materials and even "green" thermoplastics. This article also demonstrates the possibility of 3D-printing these hydroplastics and the potential of employing them in electronics applications. The demonstrated hydroshapable structural electronic components show capability in performing electronic functions, load-bearing ability and geometry versatility, which are attractive features for lightweight, customizable and geometry-unique electronic devices.

A bibliometric analysis of cellulose anti-fouling in marine environments

Marine biofouling poses significant challenges to maritime industries worldwide, affecting vessel performance, fuel efficiency, and environmental sustainability. These challenges demand innovative and sustainable solutions. In this review, the evolving landscape of cellulose-based materials for anti-fouling applications in marine environments is explored. Through a comprehensive bibliometric analysis, the current state of research is examined, highlighting key trends, emerging technologies, and geographical distributions. Cellulose, derived from renewable resources, offers a promising avenue for sustainable anti-fouling strategies due to its biodegradability, low toxicity, and resistance to microbial attachment. Recent advancements in cellulose-based membranes, coatings, and composites are discussed, showcasing their efficacy in mitigating biofouling while minimizing environmental impact. Opportunities for interdisciplinary collaboration and innovation are identified to drive the development of next-generation anti-fouling solutions. By harnessing the power of cellulose, progress towards cleaner, more sustainable oceans can be facilitated, fostering marine ecosystems and supporting global maritime industries.

Bio-Inspired Functional Materials for Environmental Applications

With the global population expected to reach 9.7 billion by 2050, there is an urgent need for advanced materials that can address existing and developing environmental issues. Many current synthesis processes are environmentally unfriendly and often lack control over size, shape, and phase of resulting materials. Based on knowledge from biological synthesis and assembly processes, as well as their resulting functions (e.g., photosynthesis, self-healing, anti-fouling, etc.), researchers are now beginning to leverage these biological blueprints to advance bio-inspired pathways for functional materials for water treatment, air purification and sensing. The result has been the development of novel materials that demonstrate enhanced performance and address sustainability. Here, an overview of the progress and potential of bio-inspired methods toward functional materials for environmental applications is provided. The challenges and opportunities for this rapidly expanding field and aim to provide a valuable resource for researchers and engineers interested in developing sustainable and efficient processes and technologies is discussed.

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.

Programmable and Modularized Gas Sensor Integrated by 3D Printing

The rapid advancement of intelligent manufacturing technology has enabled electronic equipment to achieve synergistic design and programmable optimization through computer-aided engineering. Three-dimensional (3D) printing, with the unique characteristics of near-net-shape forming and mold-free fabrication, serves as an effective medium for the materialization of digital designs into usable devices. This methodology is particularly applicable to gas sensors, where performance can be collaboratively optimized by the tailored design of each internal module including composition, microstructure, and architecture. Meanwhile, diverse 3D printing technologies can realize modularized fabrication according to the application requirements. The integration of artificial intelligence software systems further facilitates the output of precise and dependable signals. Simultaneously, the self-learning capabilities of the system also promote programmable optimization for the hardware, fostering continuous improvement of gas sensors for dynamic environments. This review investigates the latest studies on 3D-printed gas sensor devices and relevant components, elucidating the technical features and advantages of different 3D printing processes. A general testing framework for the performance evaluation of customized gas sensors is proposed. Additionally, it highlights the superiority and challenges of programmable and modularized gas sensors, providing a comprehensive reference for material adjustments, structure design, and process modifications for advanced gas sensor devices.

Hierarchically Structured Metal-Organic Framework Polymer Composites for Chemical Warfare Agent Degradation

Metal-organic frameworks (MOFs) have captured the imagination of researchers for their highly tunable properties and many potential applications, including as catalysts for a variety of transformations. Even though MOFs possess significant potential, the challenges associated with processing of these crystalline powders into usable form factors while retaining their functional properties limit their end use applications. Herein, we introduce a new approach to construct MOF-polymer composites via 3D photoprinting to overcome these limitations. We designed photoresin composite formulations that use polymerization-induced phase separation to cause the MOF catalysts to migrate to the surface of the printed material, where they are accessible to substrates such as chemical warfare agents. Using our approach, MOF-polymer composites can be fabricated into nearly any shape or architecture while retaining both the excellent catalytic activity at 10 wt % loading of the MOF components and the flexible, elastomeric mechanical properties of a polymer.

Integrated Three-Dimensional Microdevice with a Modified Surface for Enhanced DNA Separation from Biological Samples

Functional interfaces and devices for rapid adsorption and immobilization of nucleic acids (NAs) are significant for relevant bioengineering applications. Herein, a microdevice with poly(acrylic acid) (PAA) photosensitive resin was integrated by three-dimensional (3D) printing, named DPAA for short. Precise microscale structures and abundant surface carboxyl functional groups were fabricated for fast and high-throughput deoxyribonucleic acid (DNA) separation. Surface modification was then done using polydopamine (PDA) and poly(ethylene glycol) (PEG) to obtain modified poly(acrylic acid) (PAA)-based devices DPDA-PAA and DPEG-PAA rich in amino and hydroxyl groups, respectively. The fabricated device DPAA possessed superior printing accuracy (40-50 μm). Functionalization of amino and hydroxyl was successful, and the modified devices DPDA-PAA and DPEG-PAA maintained a high thermal stability like DPAA. Surface potential analysis and molecular dynamics simulation indicated that the affinity for DNA was in the order of DPDA-PAA > DPEG-PAA > DPAA. Further DNA separation experiments confirmed the high throughput and high selectivity of DNA separation performance, consistent with the predicted affinity results. DPDA-PAA showed relatively the highest DNA extraction yield, while DPEG-PAA was the worst. An acidic binding system is more favorable for DNA separation and recovery. DPDA-PAA showed significantly better DNA extraction performance than DPAA in a weakly acidic environment (pH 5.0-7.0), and the average DNA yield of the first elution was 2.16 times that of DPAA. This work validates the possibility of modification on integrated 3D microdevices to improve their DNA separation efficiency effectively. It also provides a new direction for the rational design and functionalization of bioengineering separators based on nonmagnetic methods. It may pave a new path for the highly efficient polymerase chain reaction diagnosis.

3D-Printed Materials for Wastewater Treatment

The increasing levels of water pollution pose an imminent threat to human health and the environment. Current modalities of wastewater treatment necessitate expensive instrumentation and generate large amounts of waste, thus failing to provide ecofriendly and sustainable solutions for water purification. Over the years, novel additive manufacturing technology, also known as three-dimensional (3D) printing, has propelled remarkable innovation in different disciplines owing to its capability to fabricate customized geometric objects rapidly and cost-effectively with minimal byproducts and hence undoubtedly emerged as a promising alternative for wastewater treatment. Especially in membrane technology, 3D printing enables the designing of ultrathin membranes and membrane modules layer-by-layer with different morphologies, complex hierarchical structures, and a wide variety of materials otherwise unmet using conventional fabrication strategies. Extensive research has been dedicated to preparing membrane spacers with excellent surface properties, potentially improving the membrane filtration performance for water remediation. The revolutionary developments in membrane module fabrication have driven the utilization of 3D printing approaches toward manufacturing advanced membrane components, including biocarriers, sorbents, catalysts, and even whole membranes. This perspective highlights recent advances and essential outcomes in 3D printing technologies for wastewater treatment. First, different 3D printing techniques, such as material extrusion, selective laser sintering (SLS), and vat photopolymerization, emphasizing membrane fabrication, are briefly discussed. Importantly, in this Perspective, we focus on the unique 3D-printed membrane modules, namely, feed spacers, biocarriers, sorbents, and so on. The unparalleled advantages of 3D printed membrane components in surface area, geometry, and thickness and their influence on antifouling, removal efficiency, and overall membrane performance are underlined. Moreover, the salient applications of 3D printing technologies for water desalination, oil-water separation, heavy metal and organic pollutant removal, and nuclear decontamination are also outlined. This Perspective summarizes the recent works, current limitations, and future outlook of 3D-printed membrane technologies for wastewater treatment.

Nanocelluloses as sustainable membrane materials for separation and filtration technologies: Principles, opportunities, and challenges

Membrane technology is of great interest in various environmental and industrial applications, where membranes are used to separate different mixtures of gas, solid-gas, liquid-gas, liquid-liquid, or liquid-solid. In this context, nanocellulose (NC) membranes can be produced with predefined properties for specific separation and filtration technologies. This review explains the use of nanocellulose membranes as a direct, effective, and sustainable way to solve environmental and industrial problems. The different types of nanocellulose (i.e., nanoparticles, nanocrystals, nanofibers) and their fabrication methods (i.e., mechanical, physical, chemical, mechanochemical, physicochemical, and biological) are discussed. In particular, the structural properties of nanocellulose membranes (i.e., mechanical strength, interactions with various fluids, biocompatibility, hydrophilicity, and biodegradability) are reviewed in relation to membrane performances. Advanced applications of nanocellulose membranes in reverse osmosis (RO), microfiltration (MF), nanofiltration (NF), and ultrafiltration (UF) are highlighted. The applications of nanocellulose membranes offer significant advantages as a key technology for air purification, gas separation, and water treatment, including suspended or soluble solids removal, desalination, or liquid removal using pervaporation membranes or electrically driven membranes. This review will cover the current state of research, future prospects, and challenges in commercializing nanocellulose membranes with respect to membrane applications.

Biopolymers as a versatile tool with special emphasis on environmental application

Water sources are becoming highly unsuited as potable sources due to the presence of impurities and hazardous chemicals. Although there are many conventional methods available, the development of innovative technologies is essential for the treating and recycling of wastewater. Owing to their unique and excellent qualities, polymers have recently seen extensive use across various industries. By joining the monomeric components covalently, biopolymers resemble a more natural alternative to synthetic polymers. The biopolymer and biopolymer composites integrate into many sections of the treatment process easily, making them effective, affordable, and environmentally beneficial. Due to their distinct features, biopolymers can replace traditional adsorbents. The biopolymers and composites discussed in this chapter are ideal adsorbent materials for eliminating contaminants from the environment. Based on their sources, methods of preparation, and uses, biopolymers, and their composites are categorized. This chapter also includes different research perspectives on biopolymers, especially from an ecological and financial standpoint.

Presence, origins and effect of stable surface hydration on regenerated cellulose for underwater oil-repellent membranes

HYPOTHESIS

Underwater oil-repellency of polyelectrolyte brushes has been attributed mainly to electric double-layer repulsion forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Many non-polyelectrolyte materials also exhibit oil-repellent behaviour, but it is not clear if there exist similar electric double-layer repulsion and if it is the sole mechanism governing their underwater oil-repellency.

EXPERIMENTS/SIMULATIONS

In this article, the oil-repellency of highly amorphous cellulose exhibiting is investigated in detail, through experiments and molecular dynamics simulations (MDS).

FINDINGS

It was found that the stable surface hydration on regenerated cellulose was due to a combination of long-range electrostatic repulsions (DLVO theory) and short-range interfacial hydrogen bonding between cellulose and water molecules (as revealed by MDS). The presence of a stable water layer of about 200 nm thick (similar to that of polyelectrolyte brushes) was confirmed. Such stable surface hydration effectively separates cellulose surface from oil droplets, resulting in extremely low adhesion between them. As a demonstration of its practicality, regenerated cellulose membranes were fabricated via electrospinning, and they exhibit high oil/water separation efficiencies (including oil-in-water emulsions) as well as self-cleaning ability.

Oil/Water Mixtures and Emulsions Separation Methods-An Overview

Catastrophic oil spill accidents, oily industrial wastewater, and other types of uncontrolled release of oils into the environment are major global issues since they threaten marine ecosystems and lead to a big economic impact. It can also affect the public health of communities near the polluted area. This review addresses the different types of oil collecting methods. The focus of this work will be on the different approaches to materials and technologies for oil/water separation, with a special focus on water/oil emulsion separation. Emulsified oil/water mixtures are extremely stable dispersions being, therefore, more difficult to separate as the size of the droplets in the emulsion decreases. Oil-absorbent materials, such as sponges, foams, nanoparticles, and aerogels, can be adjusted to have both hydrophobic and oleophilic wettability while displaying a porous structure. This can be advantageous for targeting oil spills in large-scale environmental and catastrophic sets since these materials can easily absorb oil. Oil adsorbent materials, for example, meshes, textiles, membranes, and clays, involve the capture of the oily material to the surface of the adsorbent material, additionally attracting more attention than other technologies by being low-cost and easy to manufacture.

Stainless Steel Screen Modified with Renatured Xerogel for Efficient and Highly Stable Oil/Water Separation via Gravity

The application of hydrogel coatings to surface-modified metallic materials has gained considerable attention in engineering practice such as water-oil separation. However, the low coating adhesion and poor coating stability restrict its application. In this study, to obtain special wettability and durable filter materials, polyacrylamide (PAM)/sodium alginate (SA) xerogel particles were first prepared and adhered to a stainless steel screen by using an epoxy resin as a linker. Subsequently, the xerogel particles of the screen rehydrates in water to form a PAM-SA double-network hydrogel. The results show that the screen modified by PAM-SA xerogel of 20-30 μm particle size and a linker concentration of 0.1 g/mL resulted in a chimeric structure and subsequently transformed a uniform double-network hydrogel coating in water. According to the experimental results, the rough hydrogel coating exhibits superhydrophilicity and superoleophobicity under water; in particular, it has excellent wear resistance as well as physical and chemical stability. Under gravity-driven action, the PAM-SA-modified screen demonstrates high separation efficiency values of up to 99% in separating a wide range of oil/water mixtures and maintaining a water flux of (2-6) × 10⁴ L·m^-2·h^-1. There was no significant reduction in efficiency of separation and water flux after 10 cycles, indicating that the PAM-SA-modified screen is capable of offering outstanding separation performance and durability. Moreover, the hydrogel-modified screen demonstrated corrosion and swelling resistance in some extreme environments, paving a way for practical applications in water treatment. The novel hydrogel-coating-modified screen with ease of preparation holds great promise for oil/water separation and other engineering applications.

Biopolymer - A sustainable and efficacious material system for effluent removal

Undesired discharge of various effluents directly into the aquatic ecosystem can adversely affect water quality, endangering aquatic and terrestrial flora and fauna. Therefore, the conceptual design and fabrication of a sustainable system for alleviating the harmful toxins that are discharged into the atmosphere and water bodies using a green sustainable approach is a fundamental standpoint. Adsorptive removal of toxins (∼99% removal efficacy) is one of the most attractive and facile approaches for cleaner technologies that remediate the environmental impacts and provide a safe operating space. Recently, the introduction of biopolymers for the adsorptive abstraction of toxins from water has received considerable attention due to their eclectic accessibility, biodegradability, biocompatibility, non-toxicity, and enhanced removal efficacy (∼ 80-90% for electrospun fibers). This review summarizes the recent literature on the biosorption of various toxins by biopolymers and the possible interaction between the adsorbent and adsorbate, providing an in-depth perspective of the adsorption mechanism. Most of the observed results are explained in terms of (1) biopolymers classification and application, (2) toxicity of various effluents, (3) biopolymers in wastewater treatment and their removal mechanism, and (4) regeneration, reuse, and biodegradation of the adsorbent biopolymer.

3D printing titanium dioxide-acrylonitrile-butadiene-styrene (TiO2-ABS) composite membrane for efficient oil/water separation

The oily water treatment is becoming one of the hottest topics due to that increase of offshore oil transportation and the various accident oil leakages. In this study, a functional TiO₂-ABS composite membrane was generated through the three-dimensional (3D) printing strategy for the first time and was conducted to simulated oily water treatment. The TiO₂-ABS composite membrane demonstrated a significant promotion in hydrophilicity and oleophobicity which were evidenced by the water contact angle of 14.8° and the underwater oil contact angle of 144.7°, respectively. The optimal modified membrane had both exceedingly high flux (1.8 × 10⁵ L m^-2·h^-1) and oil rejection rate (99.5%). Moreover, the results of filtration cycles of 10 days and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory demonstrated that the modified membranes took possession of excellent stability and antifouling property. What was more, the TiO₂-ABS composite membrane revealed over 99% rejection to all five types of oil/water systems. The interestingly experimental results indicated that the prepared membrane possessed a broad development trend and application prospect in the field of oily water treatment.

Dynamic Wetting of Ionic Liquid Drops on Hydrophobic Microstructures

Ionic liquids (ILs)─salts in a liquid state─play a crucial role in various applications, such as green solvents for chemical synthesis and catalysis, lubricants, especially for micro- and nanoelectromechanical systems, and electrolytes in solar cells. These applications critically rely on unique or tunable bulk properties of ionic liquids, such as viscosity, density, and surface tension. Furthermore, their interactions with different solid surfaces of various roughness and structures may uphold other promising applications, such as combustion, cooling, and coating. However, only a few systematic studies of IL wetting and interactions with solid surfaces exist. Here, we experimentally and theoretically investigate the dynamic wetting and contact angles (CA) of water and three kinds of ionic liquid droplets on hydrophobic microstructures of surface roughness (r = 2.61) and packing fraction (ϕ = 0.47) formed by micropillars arranged in a periodic pattern. The results show that, except for water, higher-viscosity ionic liquids have greater advancing and receding contact angles with increasing contact line velocity. Water drops initially form a gas-trapping, CB wetting state, whereas all three ionic liquid drops are in a Wenzel wetting state, where liquids penetrate and completely wet the microstructures. We find that an existing model comparing the global surface energies between a CB and a Wenzel state agrees well with the observed wetting states. In addition, a molecular dynamic model well predicts the experimental data and is used to explain the observed dynamic wetting for the ILs and superhydrophobic substrate. Our results further show that energy dissipation occurs more significantly in the three-phase contact line region than in the liquid bulk.

Prospects of Polymeric Nanocomposite Membranes for Water Purification and Scalability and their Health and Environmental Impacts: A Review

Water shortage is a major worldwide issue. Filtration using genuine polymeric membranes demonstrates excellent pollutant separation capabilities; however, polymeric membranes have restricted uses. Nanocomposite membranes, which are produced by integrating nanofillers into polymeric membrane matrices, may increase filtration. Carbon-based nanoparticles and metal/metal oxide nanoparticles have received the greatest attention. We evaluate the antifouling and permeability performance of nanocomposite membranes and their physical and chemical characteristics and compare nanocomposite membranes to bare membranes. Because of the antibacterial characteristics of nanoparticles and the decreased roughness of the membrane, nanocomposite membranes often have greater antifouling properties. They also have better permeability because of the increased porosity and narrower pore size distribution caused by nanofillers. The concentration of nanofillers affects membrane performance, and the appropriate concentration is determined by both the nanoparticles' characteristics and the membrane's composition. Higher nanofiller concentrations than the recommended value result in deficient performance owing to nanoparticle aggregation. Despite substantial studies into nanocomposite membrane manufacturing, most past efforts have been restricted to the laboratory scale, and the long-term membrane durability after nanofiller leakage has not been thoroughly examined.

Mechanically Tough and Regenerable Antibacterial Nanofibrillated Cellulose-Based Aerogels for Oil/Water Separation

Nanofibrillated cellulose (NFC)-based aerogels have been widely used for various applications. However, the disadvantages of poor structural stability, low mechanical toughness, and easy contamination by bacteria hinder their large-scale application. In this work, 3-(3'-acrylicacidpropylester)-5,5-dimethyl hydantoin (APDMH) was grafted on oxidized NFC (ONC) to prepare antibacterial poly(APDMH)-g-ONC (PAC). PAC and poly(ethyleneimine) (PEI) were chemically cross-linked using 3-glycidoxypropyltrimethox (GPTMS), aiming at constructing a PAC-g-PEI aerogel with multiple network structures. The mechanical behaviors of composite aerogel and oil/water separation performances under different conditions were investigated. PAC-g-PEI aerogel exhibits outstanding fatigue resistance (>50 cycles of compression) and superior elasticity (96.76% height recovery after five compression-release cycles at 50% strain). The obtained superhydrophilic and underwater-oleophobic properties endow the aerogel with excellent oil/water separation performances, achieving a satisfactory separation efficiency of over 99% and flux of over 9500 L·m^-2·h^-1. Furthermore, the chlorinated aerogel of PAC-g-PEI-Cl shows highly efficient and rechargeable antibacterial properties, can inactivate 6.72-log Escherichia coli and 6.60-log Staphylococcus aureus within 10 min, and can still kill all inoculated bacteria after 50 cycles. In addition, PAC-g-PEI-Cl aerogel can inhibit biofilm formation, making it a promising candidate for highly efficient oil/water separation applications in diverse harsh conditions.

Slippery, Water-Infused Membrane with Grooved Nanotrichomes for Lubricating-Induced Oil Repellency

Water, abundant and ubiquitous in nature, is an easy yet powerful resource for the creatures to survive by putting together with their topologies interfacing their living environment. Here, a slippery, water-infusing surface (SWIS) that retains a thick and stable water layer on the membrane is presented, robustly maintaining the oil repellency against the pressure and friction of immiscible liquids. Inspired by the plant trichome structures and their function, grooved nanotrichome, formed on the fibrous membrane by the oxygen plasma etching, induces robust water lubrication on the SWIS. SWIS membrane repels and separates highly viscous and adhesive oils in air and underwater by preventing oils from adhering to the lubricating surface. Repeated tests both in air and underwater confirm the antiadhesion and self-cleaning properties of the SWIS. The SWIS oil scooper, fixed on a frame with a handle, successfully collects spilled oil on a pilot-scale oil spill site and a real ocean oil spill site by simply scooping and recovering the oil. In addition, SWIS membrane is expected to help protect environments with further applications such as oil-wastewater treatment and oil separation in food.

Evaporation Dynamics of Surfactant-Laden Droplets on a Superhydrophobic Surface: Influence of Surfactant Concentration

Surfactant-laden sessile droplet evaporation plays a crucial role in a variety of omnipresent natural and technological applications, such as drying, coating, spray, and inkjet printing. Surfactant molecules can adsorb easily on interfaces and, hence, destructively ruin the useful gas-trapping wetting state (i.e., Cassie-Baxter, CB) of a drop on superhydrophobic (SH) surfaces. However, the influence of surfactant adsorption or concentration on evaporation modes has been rarely investigated so far. Here, we investigate the evaporation dynamics of aqueous didodecyldimethylammonium bromide (DDAB) sessile droplet on SH surfaces made of regular hydrophobic micropillars, with various dimensionless surfactant concentrations (C_S), primarily using experiments. We find that all drops initially form a CB state with a pinned base radius and evaporate in a mode of constant contact radius (CCR). Water and low-C_S (=0.02) drop subsequently evaporate with a constant contact angle (CCA) mode, followed by a CCR mode and, eventually, a mixed-mode. By contrast, high-C_S (of 0.25-1) droplets undergo a complex mixed mode, with rapidly increasing base radius, and finally a mixed mode, with slowly decreasing base radius and contact angle. The experimental data reveal that contact-angle-dependent evaporative mass flux, ṁ, collapses onto a nearly universal curve depending on C_S. For the low-C_S (of 0-0.25) drops, ṁ is lower and consistent with an evaporative cooling model, whereas high-C_S (of 0.5-1) droplets are consistent with a pure vapor-diffusive model. We further show that the critical C_S delineating these two evaporative models correlates with saturated surfactant adsorption on both liquid-solid and liquid-vapor interfaces.

Highly Efficient Self-Repairing Slippery Liquid-Infused Surface with Promising Anti-Icing and Anti-Fouling Performance

Smart slippery liquid-infused porous surfaces (SLIPSs) have aroused remarkable attention owing to tremendous application foreground in biomedical instruments and industry. However, challenges still remain in fabricating durable SLIPSs. In this work, a fast and highly efficient self-repairing slippery surface (SPU-60M) was fabricated based on a polyurethane membrane and silicone oil. By introducing a great quantity of reversible disulfide bonds into the polymer backbone and hydrogen bonds in the polymer interchain, this SLIPS material could be quickly repaired in 15 min with 97.8% healing efficiency. Moreover, the self-healing efficiency could be maintained at 42.75% after the 10th cutting-healing cycle. Notably, SPU-60M showed excellent self-repairing ability not only in an ambient environment but also in an underwater environment and at ultralow temperatures. Besides, the icing delay time (DT) of SPU-60M could be prolonged to 1182 s at -15 °C, and the ice adhesion strength was only 10.33 kPa at -30 °C. In addition, SPU-60M had excellent anti-fouling performance with BSA adsorption of 2.41 μg/cm² and Escherichia coli CFU counts of 41 × 10⁴. These findings provide a facile way to design highly efficient self-repairing SLIPSs with multifunctionality.

Current Status of Cellulosic and Nanocellulosic Materials for Oil Spill Cleanup

Recent developments in the application of lignocellulosic materials for oil spill removal are discussed in this review article. The types of lignocellulosic substrate material and their different chemical and physical modification strategies and basic preparation techniques are presented. The morphological features and the related separation mechanisms of the materials are summarized. The material types were classified into 3D-materials such as hydrophobic and oleophobic sponges and aerogels, or 2D-materials such as membranes, fabrics, films, and meshes. It was found that, particularly for 3D-materials, there is a clear correlation between the material properties, mainly porosity and density, and their absorption performance. Furthermore, it was shown that nanocellulosic precursors are not exclusively suitable to achieve competitive porosity and therefore absorption performance, but also bulk cellulose materials. This finding could lead to developments in cost- and energy-efficient production processes of future lignocellulosic oil spillage removal materials.

Shape-Deformed Mushroom-like Reentrant Structures for Robust Liquid-Repellent Surfaces

Artificial liquid-repellent surfaces inspired by biomimetic structures provide a wide range of functional surfaces for various practical applications, such as self-cleaning, antisticking, oil/water separation, and droplet manipulation. However, functional biomimetic structures cannot be fabricated using conventional techniques. For example, mushroom-like topologies on the skin of springtails, which are referred to as "doubly reentrant structures," have attracted significant attention owing to their extraordinary liquid-repellent properties. Current methods of fabricating these reentrant structures have several limitations, such as complex material systems, processing steps, and additional chemical treatments. This study proposed a simple micro-shape-deformed approach to fabricate mushroom-like reentrant structures by digital light processing, a three-dimensional (3D) printing technique, with volumetric shrinkage. The nonuniform cross-linking process and light propagation during photopolymerization caused the deformation of the topological patterns atop the micropillar arrays, resulting in bent structures for mushroom-like shape-deformed microarchitectures. This 3D-printed shape-deformed microstructure exhibits a highly stable liquid repellency without perfluorinated coatings.

Chiral Photonic Liquid Crystal Films Derived from Cellulose Nanocrystals

As a nanoscale renewable resource derived from lignocellulosic materials, cellulose nanocrystals (CNCs) have the features of high purity, high crystallinity, high aspect ratio, high Young's modulus, and large specific surface area. The most interesting trait is that they can form the entire films with bright structural colors through the evaporation-induced self-assembly (EISA) process under certain conditions. Structural color originates from micro-nano structure of CNCs matrixes via the interaction of nanoparticles with light, rather than the absorption and reflection of light from the pigment. CNCs are the new generation of photonic liquid crystal materials of choice due to their simple and convenient preparation processes, environmentally friendly fabrication approaches, and intrinsic chiral nematic structure. Therefore, understanding the forming mechanism of CNCs in nanoarchitectonics is crucial to multiple fields of physics, chemistry, materials science, and engineering application. Herein, a timely summary of the chiral photonic liquid crystal films derived from CNCs is systematically presented. The relationship of CNC, structural color, chiral nematic structure, film performance, and applications of chiral photonic liquid crystal films is discussed. The review article also summarizes the most recent achievements in the field of CNCs-based photonic functional materials along with the faced challenges.

Cellulose-based special wetting materials for oil/water separation: A review

Oil spill accidents and oily wastewater discharged by petrochemical industries have severely wasted water resources and damaged the environment. The use of special wetting materials to separate oil and water is efficient and environment-friendly. Cellulose is the most abundant renewable resource and has natural advantages in removing pollutants from oily wastewater. The application and modification of cellulose as special wetting materials have attracted considerable research attention. Therefore, we summarized cellulose-based superlipophilic/superhydrophobic and superhydrophilic/superoleophobic materials exhibiting special wetting properties for oil/water separation. The treatment mechanism, preparation technology, treatment effect, and representative projects of oil-bearing wastewater are discussed. Moreover, cellulose-based intelligent-responsive materials for application to oil/water separation and the removal of other pollutants from oily wastewater have also been summarized. The prospects and potential challenges of all the materials have been highlighted.

Solar-Assisted, Fast, and In Situ Recovery of Crude Oil Spill by a Superhydrophobic and Photothermal Sponge

Development of a functional sorbent for effective crude oil absorption is essential to address large-scale spilling incidents. Herein, we demonstrate a facile method for preparing a superhydrophobic and photothermal PDMS/CuS/PDA@MF sponge through sequential depositions of PDA, CuS nanoparticles, and a PDMS layer onto a melamine sponge. The optimized composite sponge exhibits a superhydrophobic surface property, high absorption capacity for oils, robust recycling, and excellent photothermal conversion performance. Under sunlight irradiation, the sponge can be rapidly heat up for effectively reducing the viscosity of the surrounding crude oil in order to enhance its fluidity. As a result, uptake of crude oil can be achieved continuously at approximately 5.3 g/min using a peristaltic pump. Overall, we believe that a simple fabrication method from low-cost reagents and excellent crude oil remediation performance render the PDMS/CuS/PDA@MF sponge as an excellent sorbent candidate for remediating crude oil spill.

Highly antifouling, biocompatible and tough double network hydrogel based on carboxybetaine-type zwitterionic polymer and alginate

Because of resistance to bio-macromolecular adhesion, antifouling hydrogels have attracted great attention in biomedical field. But traditional antifouling hydrogels made by hydrophilic polymers are always poor of mechanical properties. Herein, a new hybrid ionic-covalent cross-linked double network (DN) hydrogel was prepared by a simple one-pot method based on sodium alginate and the zwitterionic material carboxybetaine acrylamide (CBAA). The DN hydrogel has good mechanical properties, including high elastic modulus (0.28 MPa), high tensile strength (0.69 MPa), as well as good self-recovery capability. More importantly, the DN hydrogel is highly resistance to the adsorption of non-specific protein, cells, bacteria and algae, exhibiting an outstanding antifouling property. The in vitro and in vivo experiments prove that the DN hydrogel is highly biocompatible. This study provides a new strategy for the preparation of antifouling DN hydrogels with good mechanical properties for different needs, such as tissue scaffolds, wound dressings, implantable devices, and other fields.

One-Step Versatile Fabrication of Superhydrophilic Filters for the Efficient Purification of Oily Water

As industrial oily wastewater can seriously damage ecosystems, the use of filtration technology with functional filters has emerged as an effective approach for purifying oily wastewater and protecting the environment. Although several methods for preparing functional filters with specific wettability have been reported, most methods are complicated, expensive, and time-consuming. Furthermore, these methods are only applicable to specific substrates, which hinder their practical applications. Here, a simple and versatile method for the fabrication of a superhydrophilic filter on any substrate using a one-step dipping process is reported. The method is easily scaled-up to fabricate large-area superhydrophilic filters; moreover, mass production is possible using a roll-to-roll process. The resulting filter is durable, stable, and, due to its stable hydrophilic layer, shows no deterioration in wetting behavior; it also exhibits self-cleaning properties. Based on its selective wetting characteristics, oil/water mixtures and oil-in-water emulsions stabilized by surfactants can be purified in a highly efficient manner. Importantly, owing to its self-cleaning properties, the filter can be reused after simply immersing and washing in water. This easy, cost-effective, fast, and versatile method for fabricating superhydrophilic filters can be practically applied in industries that need to purify oily water.

Durable super-hydrophobic PDMS@SiO2@WS2 sponge for efficient oil/water separation in complex marine environment

The robust and eco-friendly super-hydrophobic sponge with remarkable performances has been potential adsorption material for the treatment of offshore oil spills. In this work, the durable PDMS@SiO₂@WS₂ sponge was fabricated via a green and facile one-step dipping method. The mixed tungsten disulfide (WS₂) microparticles and hydrophobic SiO₂ nanoparticles were immobilized on the sponge by non-toxic polydimethylsiloxane (PDMS) glue tier, which featured the hierarchical structure and extreme water repellency with the water contact angle of 158.8 ± 1.4°. The obtained PDMS@SiO₂@WS₂ sponge exhibits high oil adsorption capacity with 12-112 times of its own weight, and oil/water selectivity with separation efficiency over 99.85%. Notably, when subjected to the complex marine environment including high temperature, corrosive condition, insolation, and strong wind and waves, the modified sponge can maintain sable super-hydrophobicity with water contact angle over 150°. Moreover, it possesses superior mechanical stability for sustainable reusability and oil recovery. The sponge fabricated by non-toxic modifiers along with its sable super-hydrophobicity in complex marine environment makes it a potential material for practical applications.

Fabrication of Transparent and Microstructured Superhydrophobic Substrates Using Additive Manufacturing

We report facile one- and two-step processes for the fabrication of transparent ultrahydrophobic surfaces and three-dimensional (3D)-printed superhydrophobic (SH) microstructures, respectively. In the one-step method, polydimethylsiloxane (PDMS) solution is treated thermally at 350 °C for 4 h, while PDMS-soot is generated and deposited on a glass slide to obtain a transparent SH surface without further chemical modification. For the two-step approach, SH surfaces are obtained by incorporating a 3D printing technique with a convenient hydrophobic coating method. Herein, we first 3D-print microstructured substrates with particular surface parameters, which are designed to facilitate a stable gas-trapping Cassie-Baxter (CB) wetting state based on a thermodynamic calculation. We subsequently coat the 3D-printed microstructures with candle soot (CS) or octadecyltrichlorosilane (OTS) solution to make superhydrophobic surfaces with mechanical durability. These surfaces exhibit an ultrahigh static water contact angle (CA, θ ≃ 158 ± 2 and 147 ± 2° for the CS and OTS coating, respectively) and a low roll-off angle for water droplets. Both static and dynamic (in terms of the advancing and receding) contact angles of a water droplet on the fabricated SH surfaces are in good agreement with the theoretical prediction of Cassie-Baxter contact angles. Furthermore, after a one-year-long shelf time, the SH substrates fabricated sustain good superhydrophobicity after ultrasonic water treatment and against several chemical droplets. All of these methods are simple, cost-effective, and highly efficient processes. The processes, design principle, and contact angle measurements presented here are useful for preparing transparent and superhydrophobic surfaces using additive manufacturing, which enables large-scale production and promisingly expands the application scope of utilizing self-cleaning superhydrophobic material.

Wood-Nanotechnology-Based Membrane for the Efficient Purification of Oil-in-Water Emulsions

With increasing amounts of oily water discharged from industrial and domestic sources, purifying oily emulsions using effective and eco-friendly methods is of great significance. Although functional membranes with selective wettabilities have been extensively explored for the efficient purification of oil-in-water emulsions, the development of functional membranes that use green and inexpensive materials, are simple to fabricate, and are easy to scale up remains very challenging. Herein, we report a simple approach that uses biomass to prepare a membrane for the purification of emulsions. A simple top-down approach was used to partially remove lignin and hemicellulose fractions in wood sheets, resulting in a highly porous and flexible wood membrane. The obtained wood membrane shows excellent water-absorbing and underwater anti-oil adhesion properties due to the removal of the hydrophobic lignin. The wood membrane is durable and stable, thereby maintaining its selective wettability in harsh environments. Selective wetting properties along with a porous structure enable the wood membrane to purify surfactant-stabilized oil-in-water emulsions. Such a biomass-derived membrane, which is green, inexpensive, easy to fabricate, and scalable, along with its selective wettability and durability, shows great potential for use as a substitute for existing filter media in diverse industries.