Nanotechnology Transition Roadmap toward Multifunctional Stimuli-Responsive Face Masks

Functionalized Face Masks as Smart Wearable Sensors for Multiple Sensing

Wearable sensors provide continuous physiological information and measure deviations from healthy baselines, resulting in the potential to personalize health management and diagnosis of diseases. With the emergence of the COVID-19 pandemic, functionalized face masks as smart wearable sensors for multimodal and/or multiplexed measurement of physical parameters and biochemical markers have become the general population for physiological health management and environmental pollution monitoring. This Review examines recent advances in applications of smart face masks based on implantation of digital technologies and electronics and focuses on respiratory monitoring applications with the advantages of autonomous flow driving, enrichment enhancement, real-time monitoring, diversified sensing, and easily accessible. In particular, the detailed introduction of diverse respiratory signals including physical, inhalational, and exhalant signals and corresponding associations of health management and environmental pollution is presented. In the end, we also provide a personal perspective on future research directions and the remaining challenges in the commercialization of smart functionalized face masks for multiple sensing.

Multifunctional FFP2 Face Mask for White Light Disinfection and Pathogens Detection using Hybrid Nanostructures and Optical Metasurfaces

A new generation of an FFP2 (Filtering Face Piece of type 2) smart face mask is achieved by integrating broadband hybrid nanomaterials and a self-assembled optical metasurface. The multifunctional FFP2 face mask shows simultaneously white light-assisted on-demand disinfection properties and versatile biosensing capabilities. These properties are achieved by a powerful combination of white light thermoplasmonic responsive hybrid nanomaterials, which provide excellent photo-thermal disinfection properties, and optical metasurface-based colorimetric biosensors, with a very low limit of pathogens detection. The realized system is studied in optical, morphological, spectroscopic, and cell viability assay experiments and environmental monitoring of harmful pathogens, thus highlighting the extraordinary properties in reusability and pathogens detection of the innovative face mask.

Antimicrobial activity of metal-based nanoparticles: a mini-review

The resistance of pathogenic microorganisms to antibiotics is one of the main problems of world health. Of particular concern are multidrug-resistant (MDR) bacteria. Infections caused by these microorganisms affect the appearance of acute or chronic diseases. In this regard, modern technologies, such as nanomaterials (NMs), especially promising nanoparticles (NPs), can possess antimicrobial properties or improve the effectiveness and delivery of known antibiotics. Their diversity and characteristics, combined with surface functionalization, enable multivalent interactions with microbial biomolecules. This article presents an overview of the most current research on replacing antibiotics with NPs, including the prospects and risks involved.

Electrospun Polymeric Nanofibers: Current Trends in Synthesis, Surface Modification, and Biomedical Applications

Electrospun polymeric nanofibers are essential in various fields for various applications because of their unique properties. Their features are similar to extracellular matrices, which suggests them for applications in healthcare fields, such as antimicrobials, tissue engineering, drug delivery, wound healing, bone regeneration, and biosensors. This review focuses on the synthesis of electrospun polymeric nanofibers, their surface modification, and their biomedical applications. Nanofibers can be fabricated from both natural and synthetic polymers and their composites. Even though they mimic extracellular matrices, their surface features (physicochemical characteristics) are not always capable of fulfilling the purpose of the target application. Therefore, they need to be improved via surface modification techniques. Both needle-based and needleless electrospinning are thoroughly discussed. Various techniques and setups employed in each method are also reviewed. Furthermore, pre- and postspinning modification approaches for electrospun nanofibers, including instrument design and the modification features for targeted biomedical applications, are also extensively discussed. In this way, the remarkable potential of electrospun polymeric nanofibers can be highlighted to reveal future research directions in this dynamic field.

Nanofiberous facemasks as protectives against pandemic respiratory viruses

INTRODUCTION

Wearing protective face masks and respirators has been a necessity to reduce the transmission rate of respiratory viruses since the outbreak of the coronavirus (COVID-19) disease. Nevertheless, the outbreak has revealed the need to develop efficient air filter materials and innovative anti-microbial protectives. Nanofibrous facemasks, either loaded with antiviral nanoparticles or not, are very promising personal protective equipment (PPE) against pandemic respiratory viruses.

AREAS COVERED

In this review, multiple types of face masks and respirators are discussed as well as filtration mechanisms of particulates. In this regard, the limitations of traditional face masks were summarized and the advancement of nanotechnology in developing nanofibrous masks and air filters was discussed. Different methods of preparing nanofibers were explained. The various approaches used for enhancing nanofibrous face masks were covered.

EXPERT OPINION

Although wearing conventional face masks can limit viral infection spread to some extent, the world is in great need for more protective face masks. Nanofibers can block viral particles efficiently and can be incorporated into face masks in order to enhance their filtration efficiency. Also, we believe that other modifications such as addition of antiviral nanoparticles can significantly increase the protection power of facemasks.

Self-Sanitization in a Silk Nanofibrous Network for Biodegradable PM0.3 Filters with In Situ Joule Heating

In the contemporary way of life, face masks are crucial in managing disease transmission and battling air pollution. However, two key challenges, self-sanitization and biodegradation of face masks, need immediate attention, prompting the development of innovative solutions for the future. In this study, we present a novel approach that combines controlled acid hydrolysis and mechanical chopping to synthesize a silk nanofibrous network (SNN) seamlessly integrated with a wearable stainless steel mesh, resulting in the fabrication of self-sanitizable face masks. The distinct architecture of face masks showcases remarkable filtration efficiencies of 91.4, 95.4, and 98.3% for PM0.3, PM0.5, and PM1.0, respectively, while maintaining a comfortable level of breathability (ΔP = 92 Pa). Additionally, the face mask shows that a remarkable thermal resistance of 472 °C cm2 W-1 generates heat spontaneously at low voltage, deactivating Escherichia coli bacteria on the SNN, enabling self-sanitization. The SNN exhibited complete disintegration within the environment in just 10 days, highlighting the remarkable biodegradability of the face mask. The unique advantage of self-sanitization and biodegradation in a face mask filter is simultaneously achieved for the first time, which will open avenues to accomplish environmentally benign next-generation face masks.

Engineering surgical face masks with photothermal and photodynamic plasmonic nanostructures for enhancing filtration and on-demand pathogen eradication

The shortage of face masks and the lack of antipathogenic functions has been significant since the recent pandemic's inception. Moreover, the disposal of an enormous number of contaminated face masks not only carries a significant environmental impact but also escalates the risk of cross-contamination. This study proposes a strategy to upgrade available surgical masks into antibacterial masks with enhanced particle and bacterial filtration. Plasmonic nanoparticles can provide photodynamic and photothermal functionalities for surgical masks. For this purpose, gold nanorods act as on-demand agents to eliminate pathogens on the surface of the masks upon near-infrared light irradiation. Additionally, the modified masks are furnished with polymer electrospun nanofibrous layers. These electrospun layers can enhance the particle and bacterial filtration efficiency, not at the cost of the pressure drop of the mask. Consequently, fabricating these prototype masks could be a practical approach to upgrading the available masks to alleviate the environmental toll of disposable face masks.

Two-Dimensional Nanofibrous Networks by Superspreading-Based Phase Inversion for High-Efficiency Separation

Two-dimensional (2D) nanomaterials have been widely applied as building blocks of nanoporous materials for high-precision separations. However, most existing 2D nanomaterials suffer from poor continuity and a lack of interior linking, resulting in deteriorated performance when assembled into macroscopic bulk structures. Here, a unique superspreading-based phase inversion technique is proposed to directly construct 2D nanofibrous networks (NFNs) from a polymer solution. By tailoring capillary behavior, polymer solution droplets evolve into ultrathin liquid films through superspreading; manipulating phase instability, subsequently, enables the liquid film to phase invert into continuous nanostructured networks. The assembled single-layered NFNs possess integrated structural superiorities of 1D nanoscale fiber diameter (∼40 nm) and 2D lateral infinity, exhibiting a weblike nanoarchitecture with extremely small through-pores (∼100 nm). Our NFNs show remarkable performances in air filtration (PM0.3 removal) and water purification (microfiltration level). This creation of such attractive 2D fibrous nanomaterials can pave the way for versatile high-performance separation applications.

Heat-conducting elastic ultrafine fiber sponges with boron nitride networks for noise reduction

Industrial and traffic noise has become increasingly serious with the progress of industrialization. Most existing noise-absorbing materials suffer from poor heat dissipation and insufficient low-frequency (<1000 Hz) noise absorption, which not only reduces working efficiency but also leads to safety risks. Herein, heat-conducting elastic ultrafine fiber sponges with boron nitride (BN) networks were prepared by integrating direct electrospinning and impregnation method. The large acoustic contact area of ultrafine fibers and the vibration effect of BN nanosheets in a three-dimensional direction endow fiber sponges with good noise reduction, which can reduce white noise by 28.3 dB with a high noise reduction coefficient of 0.64. Moreover, thanks to good heat-conducting networks composed of BN nanosheets and porous structures, the obtained sponges exhibit superior heat dissipation with thermal conductivity of 0.159 W m-1 K-1. Besides, the introduction of elastic polyurethane and following crosslinking endow the sponges with good mechanical properties, which have almost no plastic deformation after 1000 compressions, and the tensile strength and strain are as high as 0.28 MPa and 75%. The successful synthesis of heat-conducting elastic ultrafine fiber sponges overcomes poor heat dissipation and low-frequency noise reduction of noise absorbers.

A Fiber Sliding-Orientation Based Micromechanics Failure Model for Melt-Blown Nonwovens

The mechanical model of melt-blown nonwovens (MNs) serves as the foundation for performance optimization, which can offer helpful guidance for product material selection, structural design, and cost control. However, it is challenging to describe the micromechanics failure mechanism of MNs using the traditional mechanical model, which aims to match the model curve with the experimental result at the macrolevel. Herein, a micromechanics failure model for MNs based on sliding-orientation competition is developed. Through in situ observations of fiber position changes and the fluctuation of stress-strain curves, fiber sliding and orientation are introduced into the failure process of MNs. Due to fiber bonding and static friction, only orientation happens during the first stage of stretching. In dramatic contrast, the fibers will slide and orient in the second stage of stretching to change their positions in response to the external force. Sliding friction, fiber bonding, and static friction make up the stress of MNs, and the conflict of fiber sliding and orientation causes variations in the stress. The model has been successfully applied to polylactic acid (PLA) MNs, which proves the effectiveness of the model in MNs.

Janus Dual Self-Strengthening Structure of Bi2 O3 /Gd2 O3 Nanofibrous Membranes for Superior X-Ray Shielding

Bi2 O3 /rare earth oxide biphasic absorbers are attractive for high-efficiency X-ray shielding due to the complementary X-ray absorption effects. However, its application is severely hindered by poor interphasic contact. Here, a new Janus interface engineering strategy is reported for the construction of continuous and flexible Bi2 O3 /Gd2 O3 crystal nanofibrous membranes (FJNMs) with micro/nano dual self-strengthening interphasic adhesion. This strategy facilitates online micro-interlocking between Bi2 O3 /Gd2 O3 nanofibers and in situ nano-grain fusion between Bi2 O3 /Gd2 O3 crystals, significantly enhancing the adhesive strength at the Bi2 O3 /Gd2 O3 interface. Additionally, the synergistic shielding effect from Bi2 O3 /Gd2 O3 absorption and multiple reflections in Bi2 O3 and Gd2 O3 crystal lattices make the nanofibrous membranes a superior X-ray radiation barrier. The FJNMs demonstrate integrated features of exceptional X-ray shielding efficiency (91%-100%), robust interfacial adhesion (lap-shear strength >3.8 MPa), prominent flexibility, lightweight, and outstanding breathability. The design concepts of fibrosing biphasic absorber assemblies pave the way for asymmetrically assembling biphasic materials, setting the stage for a fundamental shift in next-generation radiation shielding materials.

Constructing Hierarchical Polymer Nanocomposites with Strongly Enhanced Thermal Conductivity

The rapid advancement of communication technology has substantially increased the demand for advanced electronic packaging materials with high thermal conductivity and outstanding electrical insulation properties. In this study, we design polyvinyl alcohol/polydopamine-modified boron nitride nanosheet (PVA/BNNS@PDA) nanocomposites with hierarchical structures by combining electrospinning, vacuum filtration deposition, and hot pressing. The modified BNNS@PDA improves the interaction between the filler and the polymer matrix while reducing the interfacial thermal resistance, resulting in superior thermal conductivity, excellent insulation, and perfect flexibility. The PVA/BNNS@PDA nanocomposites possess an ultrahigh in-plane thermal conductivity of 16.6 W/(m·K) at 35.54 wt % BNNS@PDA content. Even after 2000 folds, the nanocomposites do not undergo any crack, showing their ultrahigh thermal conductivity behavior. Furthermore, the nanocomposites exhibit a volume resistivity above 1014 Ω·cm, which is well above the standard for insulating materials. Based on these results, this work provides a novel method to produce nanocomposites with high thermal conductivity, offering a new perspective to design advanced thermal management materials.

Single-Layer and Double-Layer Filtration Materials Based on Polyvinylidene Fluoride-Co-hexafluoropropylene Nanofibers Coated on Melamine Microfibers

In this work, we demonstrate selected optimization changes in the simple design of filtration masks to increase particle removal efficiency (PRE) and filter quality factor by combining experiments and numerical modeling. In particular, we focus on single-layer filters fabricated from uniform thickness fibers and double-layer filters consisting of a layer of highly permeable thick fibers as a support and a thin layer of filtering electrospun nanofibers. For single-layer filters, we demonstrate performance improvement in terms of the quality factor by optimizing the geometry of the composition. We show significantly better PRE performance for filters composed of micrometer-sized fibers covered by a thin layer of electrospun nanofibers. This work is motivated and carried out in collaboration with a targeted industrial development of selected melamine-based filter nano- and micromaterials.

A facile spray-pressing synthesis approach for reusable photothermal masks

Certain types of face masks are highly efficient in protecting humans from bacterial and viral pathogens, and growing concerns with high safety, low cost, and wide market suitability have accelerated the replacement of reusable face masks with disposable ones during the last decades. However, wearing these masks creates countless problems associated with personnel comfort as well as more significant issues related to the cost of fabrication, the generation of medical waste, and environmental contaminants. In this work, we present a facile spray-pressing technique for the production of P-masks with a potential scale-up prospect by adding a graphene layer on one side of meltblown fabric and a functional layer on the other side. In principle, this technique could be easily integrated into the present automatic mask production process and the masks have self-cleaning and/or self-sterilizing properties when it is exposed to solar or simulated solar irradiation.

Plant Extract-Based Fabrication of Silver Nanoparticles and Their Effective Role in Antibacterial, Anticancer, and Water Treatment Applications

Ammi visnaga is a biennial or annual herbaceous plant belonging to the family Apiaceae. For the first time, silver nanoparticles were synthesized using an extract of this plant. Biofilms are a rich source of many pathogenic organisms and, thus, can be the genesis of various disease outbreaks. In addition, the treatment of cancer is still a critical drawback for mankind. The primary purpose of this research work was to comparatively analyze antibiofilms against Staphylococcus aureus, photocatalytic activity against Eosin Y, and in vitro anticancer activity against the HeLa cell line of silver nanoparticles and Ammi visnaga plant extract. The systematic characterization of synthesized nanoparticles was carried out using UV-Visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), dynamic light scattering (DLS), zeta potential, and X-ray diffraction microscopy (XRD). The initial characterization was performed with UV-Vis spectroscopy, where a peak appeared at 435 nm, which indicated the SPR band of the silver nanoparticles. AFM and SEM were performed to determine the morphology and shape of the nanoparticles, while EDX confirmed the presence of Ag in the spectra. The crystalline character of the silver nanoparticles was concluded with XRD. The synthesized nanoparticles were then subjected to biological activities. The antibacterial activity was evaluated by determining the inhibition of the initial biofilm formation with Staphylococcus aureus using a crystal violet assay. The response of the AgNPs against cellular growth and biofilm formation was found to be dose dependent. Green-synthesized nanoparticles showed 99% inhibition against biofilm and bacteria, performed excellent anticancer assay with an IC₅₀ concentration of 17.1 ± 0.6 µg/mL and 100% inhibition, and photodegradation of the toxic organic dye Eosin Y up to 50%. Moreover, the effect of the pH and dosage of the photocatalyst was also measured to optimize the reaction conditions and maximum photocatalytic potential. Therefore, synthesized silver nanoparticles can be used in the treatment of wastewater contaminated with toxic dyes, pathogenic biofilms, and the treatment of cancer cell lines.

Polylactic Acid/Calcium Stearate Hydrocharging Melt-Blown Nonwoven Fabrics for Respirator Applications

Non-biodegradable polypropylene, which poses a serious threat to the environment, is the most utilized material in air filtration systems. Moreover, under conditions of high temperature and high humidity, the electrostatic charge in melt-blown nonwoven fabrics treated with traditional corona electrets will quickly dissipate. Here, biodegradable polylactic acid, calcium stearate, and an innovative hydrocharging technique are reported to develop environmentally friendly polylactic acid/calcium stearate hydrocharging melt-blown nonwoven fabrics with high charge stability. Compared with polylactic acid melt-blown nonwoven fabrics, the crystallization structure and charge storage of polylactic acid/calcium stearate melt-blown nonwoven fabrics have been greatly improved due to the presence of calcium stearate. In PM0.3, it exhibited a high filtration efficiency (96.78%), a low pressure drop (65.20 Pa), and a good quality factor (0.053 Pa-1), which can meet the N95 respirator standard. Furthermore, it is worth mentioning that the filtration performance remained at a high level (>95.00%) after 2 months. Importantly, based on the test and analysis of surface electrostatic potential, crystallization, and charge storage and distribution, we proposed plausible charge generation and stable storage mechanisms. It demonstrated more potential for electret air filtration and smart respirators as the further possible step of research in the field.

Electrospun nanofibers for medical face mask with protection capabilities against viruses: State of the art and perspective for industrial scale-up

Face masks have proven to be a useful protection from airborne viruses and bacteria, especially in the recent years pandemic outbreak when they effectively lowered the risk of infection from Coronavirus disease (COVID-19) or Omicron variants, being recognized as one of the main protective measures adopted by the World Health Organization (WHO). The need for improving the filtering efficiency performance to prevent penetration of fine particulate matter (PM), which can be potential bacteria or virus carriers, has led the research into developing new methods and techniques for face mask fabrication. In this perspective, Electrospinning has shown to be the most efficient technique to get either synthetic or natural polymers-based fibers with size down to the nanoscale providing remarkable performance in terms of both particle filtration and breathability. The aim of this Review is to give further insight into the implementation of electrospun nanofibers for the realization of the next generation of face masks, with functionalized membranes via addiction of active material to the polymer solutions that can give optimal features about antibacterial, antiviral, self-sterilization, and electrical energy storage capabilities. Furthermore, the recent advances regarding the use of renewable materials and green solvent strategies to improve the sustainability of electrospun membranes and to fabricate eco-friendly filters are here discussed, especially in view of the large-scale nanofiber production where traditional membrane manufacturing may result in a high environmental and health risk.

Application of Inorganic Nanomaterials in Cultural Heritage Conservation, Risk of Toxicity, and Preventive Measures

Nanotechnology has allowed for significant progress in architectural, artistic, archaeological, or museum heritage conservation for repairing and preventing damages produced by deterioration agents (weathering, contaminants, or biological actions). This review analyzes the current treatments using nanomaterials, including consolidants, biocides, hydrophobic protectives, mechanical resistance improvers, flame-retardants, and multifunctional nanocomposites. Unfortunately, nanomaterials can affect human and animal health, altering the environment. Right now, it is a priority to stop to analyze its advantages and disadvantages. Therefore, the aims are to raise awareness about the nanotoxicity risks during handling and the subsequent environmental exposure to all those directly or indirectly involved in conservation processes. It reports the human-body interaction mechanisms and provides guidelines for preventing or controlling its toxicity, mentioning the current toxicity research of main compounds and emphasizing the need to provide more information about morphological, structural, and specific features that ultimately contribute to understanding their toxicity. It provides information about the current documents of international organizations (European Commission, NIOSH, OECD, Countries Normative) about worker protection, isolation, laboratory ventilation control, and debris management. Furthermore, it reports the qualitative risk assessment methods, management strategies, dose control, and focus/receptor relationship, besides the latest trends of using nanomaterials in masks and gas emissions control devices, discussing their risk of toxicity.

Mimicking natural electrical environment with cellulose acetate scaffolds enhances collagen formation of osteoblasts

The medical field is continuously seeking new solutions and materials, where cellulose materials due to their high biocompatibility have great potential. Here we investigate the applicability of cellulose acetate (CA) electrospun fibers for bone tissue regeneration. For the first time we show the piezoelectric properties of electrospun CA fibers via high voltage switching spectroscopy piezoresponse force microscopy (HVSS-PFM) tests, which are followed by surface potential studies using Kelvin probe force microscopy (KPFM) and zeta potential measurements. Piezoelectric coefficient for CA fibers of 6.68 ± 1.70 pmV^-1 along with high surface (718 mV) and zeta (-12.2 mV) potentials allowed us to mimic natural electrical environment favoring bone cell attachment and growth. Importantly, the synergy between increased surface potential and highly developed structure of the fibrous scaffold led to the formation of a vast 3D network of collagen produced by osteoblasts only after 7 days of in vitro culture. We clearly show the advantages of CA scaffolds as a bone replacement material, when long-lasting structural support is needed.

Fibrous MXene Aerogels with Tunable Pore Structures for High-Efficiency Desalination of Contaminated Seawater

The seawater desalination based on solar-driven interfacial evaporation has emerged as a promising technique to alleviate the global crisis on freshwater shortage. However, achieving high desalination performance on actual, oil-contaminated seawater remains a critical challenge, because the transport channels and evaporation interfaces of the current solar evaporators are easily blocked by the oil slicks, resulting in undermined evaporation rate and conversion efficiency. Herein, we propose a facile strategy for fabricating a modularized solar evaporator based on flexible MXene aerogels with arbitrarily tunable, highly ordered cellular/lamellar pore structures for high-efficiency oil interception and desalination. The core design is the creation of 1D fibrous MXenes with sufficiently large aspect ratios, whose superior flexibility and plentiful link forms lay the basis for controllable 3D assembly into more complicated pore structures. The cellular pore structure is responsible for effective contaminants rejection due to the multi-sieving effect achieved by the omnipresent, isotropic wall apertures together with underwater superhydrophobicity, while the lamellar pore structure is favorable for rapid evaporation due to the presence of continuous, large-area evaporation channels. The modularized solar evaporator delivers the best evaporation rate (1.48 kg m-2 h-1) and conversion efficiency (92.08%) among all MXene-based desalination materials on oil-contaminated seawater.

Electrospun transparent nanofibers as a next generation face filtration media: A review

The development of fascinating materials with functional properties has revolutionized the humankind with materials comfort, stopped the spreading of diseases, relieving the environmental pollution pressure, economized government research funds, and prolonged their serving life. The outbreak of Coronavirus Disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has triggered great global public health concern. Face masks are crucial tools to impede the spreading of SARS-CoV-2 from human to human. However, current face masks exhibit in a variety of colors (opaque), like blue, black, red, etc., leading to a communication barrier between the doctor and the deaf-mute patient when wearing a mask. High optical transparency filters can be utilized for both personal protection and lip-reading. Thus, shaping face air filter into a transparent appearance is an urgent need. Electrospinning technology, as a mature technology, is commonly used to form nanofiber materials utilizing high electrical voltage. With the alteration of the diameters of nanofibers, and proper material selection, it would be possible to make the transparent face mask. In this article, the research progress in the transparent face air filter is reviewed with emphasis on three parts: mechanism of the electrospinning process and light transmission, preparation of transparent face air filter, and their innovative potential. Through the assessment of classic cases, the benefits and drawbacks of various preparation strategies and products are evaluated, to provide general knowledge for the needs of different application scenarios. In the end, the development directions of transparent face masks in protective gear, particularly their novel functional applications and potential contributions in the prevention and control of the epidemic are also proposed.

Scalable Fabrication of Electrospun True-Nanoscale Fiber Membranes for Effective Selective Separation

Electrospun fibers have received wide attention in various fields ranging from the environment and healthcare to energy. However, nearly all electrospun fibers suffer from a pseudonanoscale diameter, resulting in fabricated membranes with a large pore size and limited separation performance. Herein, we report a novel strategy based on manipulating the equilibrium of stretch deformation and phase separation of electrospun jets to develop true-nanoscale fibers for effective selective separation. The obtained fibers present true-nanoscale diameters (∼67 nm), 1 order of magnitude less than those of common electrospun fibers, which endows the resultant membranes with remarkable nanostructural characteristics and separation performances in areas of protective textiles (waterproofness of 113 kPa and breathability of 4.1 kg m^-2 d^-1), air filtration (efficiency of 99.3% and pressure drop of 127.4 Pa), and water purification (flux of 81.5 kg m^-2 h^-1 and salt rejection of 99.94%). This work may shed light on developing high-performance separation materials for various applications.

Development of In Vitro and Ex Vivo Biofilm Models for the Assessment of Antibacterial Fibrous Electrospun Wound Dressings

Increasing evidence suggests that the chronicity of wounds is associated with the presence of bacterial biofilms. Therefore, novel wound care products are being developed, which can inhibit biofilm formation and/or treat already formed biofilms. A lack of standardized assays for the analysis of such novel antibacterial drug delivery systems enhances the need for appropriate tools and models for their characterization. Herein, we demonstrate that optimized and biorelevant in vitro and ex vivo wound infection and biofilm models offer a convenient approach for the testing of novel antibacterial wound dressings for their antibacterial and antibiofilm properties, allowing one to obtain qualitative and quantitative results. The in vitro model was developed using an electrospun (ES) thermally crosslinked gelatin-glucose (GEL-Glu) matrix and an ex vivo wound infection model using pig ear skin. Wound pathogens were used for colonization and biofilm development on the GEL-Glu matrix or pig skin with superficial burn wounds. The in vitro model allowed us to obtain more reproducible results compared with the ex vivo model, whereas the ex vivo model had the advantage that several pathogens preferred to form a biofilm on pig skin compared with the GEL-Glu matrix. The in vitro model functioned poorly for Staphylococcus epidermidis biofilm formation, but it worked well for Escherichia coli and Staphylococcus aureus, which were able to use the GEL-Glu matrix as a nutrient source and not only as a surface for biofilm growth. On the other hand, all tested pathogens were equally able to produce a biofilm on the surface of pig skin. The developed biofilm models enabled us to compare different ES dressings [pristine and chloramphenicol-loaded polycaprolactone (PCL) and PCL-poly(ethylene oxide) (PEO) (PCL/PEO) dressings] and understand their biofilm inhibition and treatment properties on various pathogens. Furthermore, we show that biofilms were formed on the wound surface as well as on a wound dressing, indicating that the demonstrated methods mimic well the in vivo situation. Colony forming unit (CFU) counting and live biofilm matrix as well as bacterial DNA staining together with microscopic imaging were performed for biofilm quantification and visualization, respectively. The results showed that both wound biofilm models (in vitro and ex vivo) enabled the evaluation of the desired antibiofilm properties, thus facilitating the design and development of more effective wound care products and screening of various formulations and active substances.

Biodegradable Electrospun Nanofiber Membranes as Promising Candidates for the Development of Face Masks

Aerosol particles, such as the widespread COVID-19 recently, have posed a great threat to humans. Combat experience has proven that masks can protect against viruses; however, the epidemic in recent years has caused serious environmental pollution from plastic medical supplies, especially masks. Degradable filters are promising candidates to alleviate this problem. Degradable nanofiber filters, which are developed by the electrospinning technique, can achieve superior filtration performance. This review focuses on the basic introduction to air filtration, the general aspects of face masks, and nanofibers. Furthermore, the progress of the state of art degradable electrospun nanofiber filters have been summarized, such as silk fibroin (SF), polylactic acid (PLA), chitosan, cellulose, and zein. Finally, the challenges and future development are highlighted.

Air-Conditioned Masks Using Nanofibrous Networks for Daytime Radiative Cooling

Face masks, as effective measures for passive air pollution control, are of fundamental importance, especially with the outbreak of emerging infectious diseases. Most existing masks are dense or thick, resulting in a lack of thermal/humidity comfort level; despite being worn tightly, they show limited PM_0.3/pathogen removal. Here, we use a facile strategy to create air-conditioned masks using heterogeneous nanofibrous networks, based on an electrospinning/netting technique. Manipulation of the phase separation and self-assembly of charged jet/droplets by control of humidity-induced double diffusion and Taylor cone instability allows for the generation of air-conditioned masks consisting of radiative cooling wrinkled nanofibers and 2D nanostructured networks. Our masks show desirable microenvironment with high-efficiency PM_0.3 removal (>99.988%), low air resistance (0.07% of atmospheric pressure), and remarkable radiative cooling capacity (∼2.8 °C temperature and ∼10% humidity drop), making high-performance filtration and temperature/humidity management "always online". This work should make possible the development of high-performance, energy-saving, and scalable fiber textiles for various applications.