Wide Range Of Relative Humidity Research Articles

Microwave humidity sensor based on shorted split ring resonator with interdigital capacitance and α-Al2O3 nanoflakes/chitosan sensitive film for respiration monitoring

A microwave relative humidity (RH) sensor based on shorted split ring resonator with interdigital capacitance (SSRR-IDC) as a test platform and α-Al2O3 nanoflakes/chitosan (CS) composite as sensitive film is proposed for the detection of human respiration. The SSRR-IDC was designed by optimizing the finger spacing and width of the IDC. Electromagnetic simulation of the designed SSRR-IDC confirms a strong electric field distribution and high dielectric sensitivity in the IDC region. The porous α-Al2O3 nanoflakes/CS composite was coated onto the IDC region of the SSRR to obtain a microwave humidity sensor. Abundant hydrophilic groups and large specific surface area of the α-Al2O3 nanoflakes/CS contribute to the adsorption of water molecules. The proposed microwave humidity sensor shows excellent sensitivity in wide RH range, especially at high humidity condition. The working principle and the sensitivity enhancement mechanism of the proposed microwave sensor were explained by combining a circuit model analysis and the dielectric property and surface microstructure changes of the sensitive materials. Furthermore, the microwave sensor also demonstrates short response/recover time and outstanding repeatability, long-term stability, temperature stability, and selectivity. Additionally, the prepared microwave humidity sensor successfully records respiratory data from different volunteers. Changes in respiratory depth before and after drinking water of the volunteers can also be distinguished by this sensor.

Sulfonated PEEK-based IPMC actuators: Exploring environmental influences

Ionomeric Polymer-Metal Composites (IPMCs) with a layered metal/polymer/metal structure are innovative biomimetic materials widely used in applications such as actuators, sensors, artificial muscles, and robotics due to their dynamic response to electrical stimuli. Nafion® is commonly used for these applications but is associated with high costs, low water retention, and poor performance at elevated temperatures. To address this, sulfonated poly(ether ether ketone) (SPEEK) is a promising and cost-effective alternative. This study focuses on evaluating the viability of SPEEK in IPMCs under varying environmental conditions, specifically a wide range of relative humidity (RH) levels (30%, 60%, and 90%) and two different counterions (H+ and Li+). FTIR tests confirmed the successful sulfonation of SPEEK, and sulfonation degrees (SD) of 44%, 72%, and 91% were determined by titration. Results indicate that increased SD leads to higher hydration levels, enhancing performance as actuators. Regarding electromechanical performance, SPEEK-based IPMCs demonstrated results comparable or superior to Nafion. Higher RH positively influenced electromechanical performance, increasing displacement and displacement rate values. Additionally, electrochemical/mechanical tests confirmed that, for the H+ counterion, SPEEK exhibited superior performance. In conclusion, SPEEK-based IPMCs, especially with H+ as the counterion, can potentially replace Nafion, offering a cost-effective alternative with favorable electromechanical performance under varying environmental conditions.

Autonomous Atmospheric Water Harvesting over a Wide RH Range Enabled by Super Hygroscopic Composite Aerogels.

Sorption-based atmospheric water harvesting (SAWH) offers a sustainable strategy to address the global freshwater shortage. However, obtaining sorbents with excellent performance over a wide relative humidity (RH) range and devices with fully autonomous water production remains challenging. Herein, magnesium chloride (MgCl2) is innovatively converted into super hygroscopic magnesium complexes(MC), which can effectively solve the problems of salt deliquescence and agglomeration. The MC are then integrated with photothermal aerogels composed of sodium alginate and carbon nanotubes (SA/CNTs) to form composite aerogels, which showed high water uptake over a wide RH range, reaching 5.43 and 0.27kg kg-1 at 95% and 20% RH, respectively. The hierarchical porous structure enables the as-prepared SA/CNTs/MC to exhibit rapid absorption/desorption kinetics with 12 cycles per day at 70% RH, equivalent to a water yield of 10.0 L kg-1 day-1. To further realize continuous and practical freshwater production, a fully solar-driven autonomous atmospheric water generator is designed and constructed with two SA/CNTs/MC-based absorption layers, which can alternately conduct the water absorption/desorption process without any other energy consumption. The design provides a promising approach to achieving autonomous, high-performance, and scalable SAWH.

Machine learning‐assisted wearable sensor array for comprehensive ammonia and nitrogen dioxide detection in wide relative humidity range

AbstractThe fast booming of wearable electronics provides great opportunities for intelligent gas detection with improved healthcare of mining workers, and a variety of gas sensors have been simultaneously developed. However, these sensing systems are always limited to single gas detection and are highly susceptible to the inference of ubiquitous moisture, resulting in less accuracy in the analysis of gas compositions in real mining conditions. To address these challenges, we propose a synergistic strategy based on sensor integration and machine learning algorithms to realize precise NH3 and NO2 gas detections under real mining conditions. A wearable sensing array based on the graphene and polyaniline composite is developed to largely enhance the sensitivity and selectivity under mixed gas conditions. Further introduction of backpropagation neural network (BP‐NN) and partial least squares (PLS) algorithms could improve the accuracy of gas identification and concentration prediction and settle the inference of moisture, realizing over 99% theoretical prediction level on NH3 and NO2 concentrations within a wide relative humidity range, showing great promise in real mining detection. As proof of concept, a wireless wearable bracelet, integrated with sensing arrays and machine‐learning algorithms, is developed for wireless real‐time warning of hazardous gases in mines under different humidity conditions.image

Ultra Responsive NO2 silicon nanowires gas sensor

Nitrogen dioxide (NO2) is a hazardous gas emitted primarily from burning fossil fuels. When inhaled, it can have severe health implications, particularly for individuals with respiratory conditions such as asthma. It contributes to ground-level ozone formation, which can cause reduced lung function and increased susceptibility to respiratory infections. When in contact with water moisture in the air, NO2 is easily oxidized into nitric acid (HNO3), causing acid rain. Detection of NO2 levels is therefore important for monitoring air quality and protecting public health. Among the possible technical solutions for gas sensing, silicon nanowires (SiNWs) have proven to be a promising candidate, partly due to their high sensitivity, low manufacturing cost, and ability to perform in various air qualities. This paper presents using SiNWs, fabricated by metal-assisted chemical etching, as a fast, accurate, sensitive, robust, and cost-effective NO2 gas sensor. Our SiNWs gas sensor can experimentally detect 20 parts per billion (ppb) of NO2 under a wide range of relative humidity. Our sensor shows ultra-high sensitivity with fast response and recovery time.

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

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

Polydopamine-modified MXene/cellulose nanofibers composite film for self-powered humidity sensing and humidity actuating

Humidity sensors are of great significance in the domains of wearable electronic products, environmental and food quality monitoring, and human healthcare. In general, they necessitate an external power source in the form of a battery. Despite considerable efforts, developing self-powered sensing systems without reliance on an external power supply remains a major challenge. Herein, an electrochemical humidity sensor with primary battery structure based on redox reaction was designed, in which polydopamine (PDA)-modified MXene/TEMPO-oxidized cellulose nanofibers/LiCl (PDMM/TOCNFs/LiCl) composite film serves as electrolyte layer. The introduction of TOCNFs confers outstanding structural stability and superior tensile strength upon the composite film. Importantly, the hygroscopic and ionic conductivity properties of the PDMM/TOCNFs/LiCl electrolyte allow the sensor to generate spontaneous voltage over a wide relative humidity (RH) range of 11 – 91%. In addition, the developed sensor exhibits excellent humidity-sensing performances, including high voltage response, fast response/recovery time, and superior humidity-sensing stability. Moreover, mussel-inspired PDA improves the ambient stability of MXene by engineering interfacial interactions, which imparts the hygroscopic PDMM/TOCNFs/LiCl composite film with desirable stability for practical applications. Finally, the potential applications of the sensor and the composite film in human respiration, non-contact sensing, and humidity actuating are demonstrated. This work paves the way for the development of an innovative self-powered humidity sensing system.

Synthesis and Characterization of Indium-Doped SnO2-Based Impedance Spectroscopy Sensor for Real-Time Humidity Sensing Applications

Metallic transition-metal dichalcogenides are emerging as promising electrode materials for applications such as 2D electronic devices owing to their good electrical conductivity. In this study, a high-performance humidity sensor based on NbTe2 electrode material and an indium-doped SnO2 thin film sensing layer was fabricated using a pulsed laser deposition system. The morphology, structural, elemental compositions, and electrical properties of the as-deposited samples were characterized. Additionally, the humidity sensing response of the fabricated sensor with In-doped SnO2 (8:92 wt%) sensing film was evaluated in a wide range of relative humidity at room temperature. The results demonstrated that the humidity sensor based on In-doped SnO2 exhibited a high sensitivity of 103.1 Ω/%RH, fast response and recovery times, a low hysteresis value, good linearity, and repeatability. In addition, the sensor had good long-term stability, with a variation in impedance of less than 3%. The results indicated that the humidity sensor could be suitable for practical humidity sensing applications.

Facile Preparation of a Photo-Cross-Linked Silk Fibroin-Poly Ionic Liquid Hydrogel with Antifreezing and Ion Conductive Properties.

The silk fibroin (SF)/ionic liquid (IL) based hydrogel is a kind of remarkable substrate for flexible devices because of its subzero-temperature elasticity, electrical conductivity, and water retention, although the procedure of the gelation is considered complex and time-consuming. In this work, we introduced an approximate method for the development of novel photo-cross-linked SF/IL hydrogel, that is, SF-IMA/PIL hydrogel via the modification of silk fibroin chain with 2-isocyanatoethyl methacrylate (SF-IMA) in a certain ionic liquid with an unsaturated double bond. The chemical cross-linking between methacrylated SF and IL was triggered by UV light, while the physical cross-linking of the hydrogel was attributed to the β-sheet formation of SF in SF-IMA/IL mixed solution. In addition to being a UV-induced three-dimensional (3D) printable one, the SF-IMA/PIL hydrogel performed significant ionic conductivity between room temperature and -50 °C and water retention within a wide range of relative humidity, which were the featured advantages as the ionic liquid involved. Moreover, the static and dynamic mechanical tests demonstrated that the hydrogel reserved its great elasticity at -50 °C and displayed its stiffness transition temperatures between -100 and -70 °C.

Thermo-Mechanical Stability of Hydrocarbon-Based Pemion® Proton Exchange Membranes

Considering the environmental concerns about the disposal of perfluorosulfonic acid (PFSA) membranes as well as the growing interest in higher temperature operability of polymer electrolyte membrane fuel cells (PEMFCs), non-fluorinated hydrocarbon-based proton exchange membranes (PEMs) with aromatic backbones have become an increasingly active area of research. Low reactant cross-over, tunable electrochemical properties, and differentiated chemistries and potentially safer and cost-reducing synthesis procedures, are additional favourable features of hydrocarbon-based PEMs for prospective use in PEMFCs [1]. Vulnerable linking units, however, are known to be the main disadvantages of these polymers in the oxidative environment of fuel cells. During PEMFC operation, destructive radical species such as hydroxyl (HO•) are produced, causing polymer degradation and thinning in the membrane [2]. Recently, sulfo-phenylated polyphenylenes (sPPPs) have shown outstanding oxidative stability due to a polymer backbone comprising only aryl-aryl bonds, with mitigated chemical degradation in ex-situ and in-situ durability studies [3, 4]. Another concern is regarding the thermo-mechanical stability of PEMs. Thus, a systematic thermo-mechanical stability study is required to confirm the potential of sPPP-based PEMs to replace conventional PFSAs, especially for high temperature PEMFC, i.e., 110-120 °C.The present research objective is to assess the thermo-mechanical stability of a commercial reinforced hydrocarbon-based PEM, Pemion® (PF1-HLF8-15-X, 15 µm thick, reinforced), as well as a mechanically-reinforced PFSA-based reference membrane, across a wide range of temperature (30-120 °C) and relative humidity (RH) (10-90%) conditions that includes the crucial high temperature window of interest for future PEMFCs [6]. To this end, a comprehensive design of experiment yielded 19 tensile tests at various hygrothermal conditions with dynamic mechanical analyzer (DMA 850; TA Instruments) equipped with an external environmental chamber accessory (TA Instruments, RH Accessory). Important mechanical properties such as Young’s modulus, ultimate tensile stress, yield stress, maximum elongation at break, strain hardening, and modulus of resilience were extracted and discussed as well. Datapoints were fitted for empirical model development and mechanical properties were estimated for high temperature and RH conditions beyond the capability of the instrument. This method can be employed to assess if the mechanical properties of membrane materials can be retained at higher temperatures, regardless of polymer chemistry and type. Storage modulus and loss modulus were separately measured in a dynamic mode to observe the impact of temperature on the mechanical response of the hydrophobic backbone and hydrophilic ionic clusters, respectively.Overall, Pemion® demonstrates tough tensile properties in the stress-strain tests due to its sterically encumbered polyphenylene backbone (Figure 1a), whereas the reference PFSA (Figure 1b) shows elastomer-like behavior with much lower Young’s modulus, yield stress, and strain hardening (slope of the curve in the plastic deformation region). Figure 1c-f show the main viscoelastic properties extracted from the tensile tests at room (30 °C, 50% RH) and high temperature fuel cell conditions (110 °C, 50% RH). The modulus of elasticity and strain hardening of Pemion® membrane are almost temperature-independent, whereas these properties for the reinforced PFSA material undergo a significant decay at high-temperature ambience. Pemion® maintains good yielding strength even at high temperature and RH conditions (110-120 °C and 80% RH). Nevertheless, small mechanical stress values as low as 1 MPa can cause spontaneous yielding in the PFSA reference material above 110 °C. The modulus of resilience for the reinforced PFSA is also predicted to be zero at elevated hygrothermal conditions (i.e., 90 °C and 70% RH). This is interpreted as an approach to the material’s glass transition condition, where it loses its mechanical integrity and therefore, is potentially unsuitable for higher temperature PEMFC operation. Moreover, the dynamic mechanical thermal analysis revealed that Pemion® retains its robustness at hygrothermal ambience close to high-temperature PEMFCs, i.e., 110-120 °C and 40-50% RH, whereas the backbone of the PFSA material gradually loses its strength. Acknowledgements This project was financially supported by Natural Sciences and Engineering Research Council of Canada (NSERC), Ionomr Innovations Inc, Canada Foundation for Innovation (CFI), British Columbia Knowledge Development Fund (BCKDF), Western Economic Diversification Canada (WD), and Canada Research Chairs (CRC).

Ternary nanocomposite comprising MnO2, GQDs, and PANI as a potential structure for humidity sensing applications

Humidity sensing has been offering a noticeable contribution in different industrial, medical, and agricultural activities. Here, graphene quantum dots doped with polyaniline (PANI) and MnO2 were successfully prepared. The synthesized system is exposed to a set of structural, morphological, and optical investigations. The apparent crystallite size is less than 30 nm, reflecting the nanoscale of the structure, and thus validating the preparation route as evident on XRD pattern. SEM images show a fibrous structure where polyaniline dominates and covers most of the structure’s surface. The evident bands of the FTIR spectrum are designated to the component used in synthesis confirming the chemical structure of the fabricated system. The humidity sensing study of the synthesized structure is carried out through a wide range of relative humidity (RH) levels range of 11–97%. The response and recovery times of the fabricated structure are found to be around 120 and 220s, respectively.

Sulfonated hypercross-linked porous organic polymer based humidity sensor

Humidity sensors are of great significance in industry, agriculture and human activities, and many nanomaterials are already used for humidity sensing. Linear ionic polymers with hydrophilic groups have exhibited good humidity detection performance because they can adsorb water and then dissociate charged carriers. However, it suffers from the instability under high relative humidity that caused by polymer chain swelling and disengagement. To overcome this shortage, in this work, a new sensor based on hypercross-linked porous organic polymer (POP) with sulfonic acid group was fabricated to humidity detection in wide humidity range. The POP with strong covalent bonds exhibits remarkable chemical and thermal stability, and sulfonic acid group in the pore can act as fully accessible active site to enhance its ability to adsorb water. The obtained sensor shows high response (∼77) in a wide relative humidity range (11%−95% RH), short response/recovery time (9 s/21 s) and good stability. Complex impedance curves and density functional theory have been carefully investigated to understand its sensing mechanism. This work provides a new direction for the development of the impedance-type humidity sensitive materials in subsequent research and practical applications.

Self-Powered, Highly Sensitive, and Flexible Humidity Sensor Based on Carboxymethyl Cellulose for Multifunctional Applications.

Self-powered humidity sensors based on friction electric and piezoelectric principles have been proposed in recent years. However, the complicated structure and preparation processes usually involved in these power generation humidity sensors limit their wider application. Herein, we developed a self-powered flexible humidity sensor with a simple structure and facile preparation process based on the primary battery principle. The self-powered humidity sensor consists of copper conductive tape as the positive electrode, nickel conductive tape as the negative electrode, and a carboxymethyl cellulose film dissolved with lithium chloride and sodium chloride as the sensing layer. The sensor exhibits good sensing linearity (R2 = 0.99791) in a wide relative humidity range (11-95%) with a satisfying response voltage of 41 mV (RH 95%) and excellent flexibility. Furthermore, the conduction mechanism of the sensing film was investigated by the complex impedance and phase angle-frequency spectral measurement and analysis. Multifunctional applications of human respiration monitoring to determine the respiratory rate and type, noncontact sensing, diaper and soil moisture detection, and power generation were demonstrated. The low-cost and facile preparation method in this work could provide a useful strategy for developing a self-powered, flexible, and multifunctional humidity sensor.

PEMFC-Performance of Unsupported Pt-Ni Aerogel Cathode Catalyst Layers under Automotive-Relevant Operative Conditions

Unsupported, Pt-based electrocatalysts hold great potential for implementation in polymer electrolyte membrane fuel cell (PEMFC-) cathodes owing to their enhanced durability under startup/shutdown conditions entailing high potential excursions. Among such materials, the recently developed Pt-Ni aerogel consisting of tridimensional nanochains of interconnected nanoparticles has already been shown to feature an initial PEMFC–performance comparable to that of C-supported Pt-nanoparticles (Pt/C) along with a much better startup/shutdown durability. However, all PEMFC characterization of this materials has been carried out at 80 °C and using fully humidified gases, and its behavior under more demanding conditions concomitant to its potential implementation for automotive applications remains unexplored. Thus, in this work aerogel catalyst layers (CLs) are characterized under a wide range of temperatures and relative humidities, as well as submitted to fast current up-transients. These extensive tests showed that the performance of the aerogel CLs is comparable to that of a commercial Pt/C benchmark, except at high current densities and low temperatures at which the thin aerogel layers suffer from a low water storage capacity.

Highly efficient and stable NiSe2-rGO composite-based room temperature hydrogen gas sensor

The widespread consumption of hydrogen in commercial and industrial applications has resulted in the development of different hydrogen gas sensors. However, their practical application is restricted due to their non-cost efficiency, low sensitivity, poor selectivity and high temperature sensing properties. Thus, the development of a sensor capable of overcoming the aforementioned limitations is critical for commercial deployment. As a result, a NiSe2-rGO composite-based H2 gas sensor has been prepared for the first time using a simple hydrothermal technique. The developed material has been systematically characterized for its morphological properties and thoroughly investigated for H2 gas sensing applications. The findings show that the developed NiSe2-rGO composite exhibited enhanced H2 gas sensing properties, besides possessing appreciable selectivity, repeatability as well as long-term stability. Furthermore, the results demonstrate a stable sensor response of 254% within 43 s and 13 s of response and recovery time respectively at a hydrogen concentration of 500 ppm which is 8 and 500 times higher than that of its individual counterparts (NiSe2 and rGO) over a wide relative humidity range, indicating the material's potential for application in industrial environments. Thus, this work paves the way for the development of stable, effective, fast-responding, and selective hydrogen gas sensors that are functional at room temperature.

Thermally Insulating and Moisture-Resilient Foams Based on Upcycled Aramid Nanofibers and Nanocellulose.

Low-density foams and aerogels based on upcycled and bio-based nanofibers and additives are promising alternatives to fossil-based thermal insulation materials. Super-insulating foams are prepared from upcycled acid-treated aramid nanofibers (upANFA ) obtained from Kevlar yarn and tempo-oxidized cellulose nanofibers (CNF) from wood. The ice-templated hybrid upANFA /CNF-based foams with an upANFA content of up to 40wt% display high thermal stability and a very low thermal conductivity of 18-23mW m-1 K-1 perpendicular to the aligned nanofibrils over a wide relative humidity (RH) range of 20% to 80%. The thermal conductivity of the hybrid upANFA /CNF foams is found to decrease with increasing upANFA content (5-20wt%). The super-insulating properties of the CNF-upANFA hybrid foams are related to the low density of the foams and the strong interfacial phonon scattering between the very thin and partially branched upANFA and CNF in the hybrid foam walls. Defibrillated nanofibers from textiles are not limited to Kevlar, and this study can hopefully inspire efforts to upcycle textile waste into high-performance products.

Characterization of an Impedance-Type Humidity Sensor Based on Porous SnO2/TiO2 Composite Ceramics Modified with Molybdenum and Zinc.

In this study, we report on the room-temperature characteristics of an impedance-type humidity sensor based on porous tin oxide/titanium oxide (SnO2/TiO2) composite ceramics modified with Mo and Zn. The SnO2/TiO2-based composites synthesized in the solid-state processing technique have been structurally characterized using X-ray diffraction, scanning electron microscopy, energy dispersive, and Raman spectroscopy. Structural analysis indicated the desired porous nature of the synthesized ceramics for sensing applications, with an average crystallite size in the nano range and a density of about 80%. The humidity-sensing properties were evaluated within a wide relative humidity range from 15% to 85% at room temperature, and the results showed that a better humidity response had a sample with Mo. This humidity-sensing material exhibits a linear impedance change of about two orders of magnitude at the optimal operating frequency of 10 kHz. Furthermore, fast response (18 s) and recovery (27 s), relatively small hysteresis (2.8%), repeatability, and good long-term stability were also obtained. Finally, the possible humidity-sensing mechanism was discussed in detail using the results of complex impedance analysis.

High-Barrier, Biodegradable Films with Polyvinyl Alcohol/Polylactic Acid + Wax Double Coatings: Influence of Relative Humidity on Transport Properties and Suitability for Modified Atmosphere Packaging Applications.

Polyvinyl alcohol (PVOH) exhibits outstanding gas-barrier properties, which favor its use as a biodegradable, high-barrier coating on food-packaging films, possibly in combination with modified atmospheres. Nonetheless, its high sensitivity to water can result in a severe loss of barrier properties, significantly limiting its applications with fresh foods and in high-humidity conditions. In this work, the water vapor (PWV) and oxygen permeability (PO2) of high-barrier biodegradable films with PVOH/PLA + wax double coatings were extensively characterized in a wide range of relative humidity (from 30 to 90%), aimed at understanding the extent of the interaction of water with the wax and the polymer matrices and the impact of this on the permeation process. What is more, a mathematical model was applied to the PWV data set in order to assess its potential to predict the permeability of the multilayer films by varying storage/working relative humidity (RH) conditions. The carbon dioxide permeability (PCO2) of the films was further evaluated, and the corresponding permselectivity values were calculated. The study was finally augmented through modified atmosphere packaging (MAP) tests, which were carried out on double-coated films loaded with 0 and 5% wax, and UV-Vis analyses. The results pointed out the efficacy of the PLA + wax coating layer in hampering the permeation of water molecules, thus reducing PVOH swelling, as well as the UV-shielding ability of the multilayer structures. Moreover, the MAP tests underlined the suitability of the double-coated films for being used as a sustainable alternative for the preservation of foods under modified atmospheres.

Self-Powered TENG with High Humidity Sensitivity from PVA Film Modified by LiCl and MXene.

Triboelectric nanogenerators (TENGs) are promising for a variety of applications that require a reliable output performance and stability. In this work, by utilizing the synergistic effect of lithium chloride (LiCl) and MXene, poly(vinyl alcohol) (PVA) based composite films with humidity-sensitive properties were prepared and employed as a friction layer to achieve self-powered TENGs with enhanced output performance under high humidity. The composite material demonstrates exceptional and stable output performance in the humidity range of 30-95% while exhibiting a strong linear correlation with increasing relative humidity (RH). At 95% RH, its short-circuit current increases up to 31.91 μA, which is three times the output of the TENG fabricated by PVA and PTFE (P-TENG). The rich hydroxyl group in PVA, the strong hygroscopicity of LiCl, and the microcapacitor network provided by MXene nanosheets significantly improve the water absorption capacity and surface roughness of the composite material, resulting in an excellent triboelectric output of TENG. Short-circuit current of the TENG in a wide range of RH (from 50% to 98%) responds very sensitively to humidity fluctuations in the environment and superior adsorption-desorption performance as humidity decreases. Furthermore, TENG regarded as a power supply in high humidity conditions was realized and it can light up 240 LEDs instantaneously with the transfer charge density of TENG reaching 194.37 μC m-2. This technology presents an effective method for stable energy harvesting and self-powered sensing in fog, the ocean, and other high-humidity environments.

Phase Behavior and Viscosity in Biomass Burning Organic Aerosol and Climatic Impacts.

Smoke particles generated by burning biomass consist mainly of organic aerosol termed biomass burning organic aerosol (BBOA). BBOA influences the climate by scattering and absorbing solar radiation or acting as nuclei for cloud formation. The viscosity and the phase behavior (i.e., the number and type of phases present in a particle) are properties of BBOA that are expected to impact several climate-relevant processes but remain highly uncertain. We studied the phase behavior of BBOA using fluorescence microscopy and showed that BBOA particles comprise two organic phases (a hydrophobic and a hydrophilic phase) across a wide range of atmospheric relative humidity (RH). We determined the viscosity of the two phases at room temperature using a photobleaching method and showed that the two phases possess different RH-dependent viscosities. The viscosity of the hydrophobic phase is largely independent of the RH from 0 to 95%. We use the Vogel-Fulcher-Tamman equation to extrapolate our results to colder and warmer temperatures, and based on the extrapolation, the hydrophobic phase is predicted to be glassy (viscosity >1012 Pa s) for temperatures less than 230 K and RHs below 95%, with possible implications for heterogeneous reaction kinetics and cloud formation in the atmosphere. Using a kinetic multilayer model (KM-GAP), we investigated the effect of two phases on the atmospheric lifetime of brown carbon within BBOA, which is a climate-warming agent. We showed that the presence of two phases can increase the lifetime of brown carbon in the planetary boundary layer and polar regions compared to previous modeling studies. Hence, the presence of two phases can lead to an increase in the predicted warming effect of BBOA on the climate.