Air Permeability Research Articles

Dual-Mode Stretchable Emitter with Programmable Emissivity and Air Permeability.

Materials with anisotropic emission characteristics have attracted considerable attention for thermal management. Although many dual-mode emitters have been developed for this purpose in the form of textiles, multilayer films, and photonic structures, multiple functionalities are essential for their versatile applications. Herein, a highly stretchable dual-mode emitter with programmable emissivity and air permeability is presented. The emitter comprises a planar Ge2Sb2Te5 (GST) cavity on one side of a perforated elastomer substrate and an infrared-reflecting metal layer on the other side. With a laser-induced phase transition from amorphous to crystalline GST, the emitter exhibits a large emissivity difference of 0.52 between both sides. The dual-mode emitter remains highly stable without mechanical failure after repeated stretching cycles to a strain of 50%. This air-permeable and stretchable emitter can be attached to any curved surface, including the human body. The GST-side emissivity can be programmed into an arbitrary emissivity pattern using a spatially modulated laser beam, ultimately enabling the printing of mutually independent visible and thermal images in a single emitter. This study provides a promising structure for multispectral optical security as well as thermal management.

Lignin microparticle coatings for enhanced wet resistance in lignocellulosic materials.

The widespread use of synthetic plastics in packaging materials poses significant environmental challenges, prompting the search for biobased, biodegradable, and non-toxic alternatives. This study focuses on improving high-yield pulps (HYPs) as sustainable materials for packaging. Enhancing wet strength and barrier properties of papers from bleached chemi-thermomechanical pulps (BCTMPs) is crucial for their application in water- and air- resistant wrappers. Traditional wet strength agents raise environmental and health concerns; therefore, this research explores the use of lignin, in the form of microparticles (LMPs), as a natural biopolymer that offers a safer alternative. However, the low viscosity of LMPs hampers their dispersion as a coating, requiring thickening agents (such as cationic starch (CS), chitosan (CH) or sodium alginate) for an effective coating formulation. Results demonstrate a synergistic effect of LMP coatings with CH or CS, enhanced by hot-pressing at 260 °C for 30 s, which improves dry and wet mechanical properties and decreases air permeability. The use of LMPs as a water-resistant interlayer between BCTMP paper sheets further improves the wet tensile index to 40 kN·m/kg for CH + LMPs and 23 kN·m/kg for CS + LMPs interlayer, representing 55 and 38 % of their respective dry tensile indices.

Lowland Integrated Crop–Livestock Systems with Grass Crops Increases Pore Connectivity and Permeability, Without Requiring Soil Tillage

Enhancing integrated crop–livestock systems (ICLSs) to improve land-use efficiency is a critical goal. Understanding the ICLS impacts on lowland soils is key to sustainable agricultural practices. Our objective was to test whether adopting ICLSs in lowlands improves soil structure, pore connectivity, and water and air permeability. This study was conducted in a long-term field trial, consisting of the following production systems with flood-irrigation rice: rice–fallow–rice, under conventional tillage and absence of grazing (RFR-ct); rice-grazed ryegrass–rice, under no-tillage and grazing (RGrR-nt); rice-grazed ryegrass–soybean-grazed ryegrass–rice, under no-tillage and grazing (RGrS/RGrR-nt); and a grazed pasture-consortium (winter) and succession field (summer), with no-till rice every 4 years (P4R-nt). Core samples were collected after grazing (October 2018), harvesting (March 2019), and grazing (October 2019). We analyzed soil air permeability, saturated hydraulic conductivity, pore connectivity by computed tomography. Soil tillage in a semi-direct system generated discontinuous porosity. Systems with intense trampling or less surface protection are affected by shearing on topsoil, reducing pore continuity. ICLSs are mainly composed of ryegrass–rice mitigated the harmful effects of trampling, and improved soil structure and functioning. Systems without soil tillage exhibited higher pore connectivity and pores with vertical orientation. Finally, soil tillage is not required to improve structural quality in ICLSs.

A Plantar Pressure Detection and Gait Analysis System Based on Flexible Triboelectric Pressure Sensor Array and Deep Learning.

Gait detection is essential for the assessment of human health status and early diagnosis of diseases. The current gait analysis systems are bulky, limited in the scope of use, and cause interference with the movement of the measured person. Hence, it is necessary to develop a wearable gait detection system that is soft, breathable, lightweight, and self-powered. Here, a plantar pressure sensor array and gait analysis system based on a flexible triboelectric pressure sensor (FTPS) array is developed. Soft, breathable, and wearable electrospinning nanofiber film with excellent triboelectric properties is used as the plantar pressure sensor, achieving a high sensitivity of 45.1 mVkPa-1 in the range of 40-200 kPa and 19.4 mVkPa-1 in the range of 200-400 kpa. 32 FTPSs are integrated into an intelligent insole, which has the characteristics of soft, easy production, good air permeability, long-time stability, no external power supply, and etc. Based on the long short-term memory artificial neural network deep learning model, the accuracy of gait judgment can reach 94.23%. This work provides a feasible solution for real-time gait detection, which will have potential applications in human health assessment and early diagnosis of disease.

Electrospinning as a Method for Fabrication of Nanofibrous Photocatalysts Based on Gallium Oxide

Photocatalysts are currently widely used in various research and industrial fields, from water and air purification to solar energy, from self‐cleaning surfaces to wearable biosensors and electronic devices. Among semiconductors, the growing interest is attracted to gallium oxide, especially β‐Ga2O3, due to the unique physical, chemical (especially acid‐resistance), physical–chemical, photochemical properties, and redox potential. These photocatalysts can be used not only as suspended mixture, but also in the form of films, nanoparticles, and nanofibers. The last one is more challenging due to the high level of surface‐to‐volume ratio, porousness, air and water permeability, and excellent morphological and physical–mechanical properties. Moreover, electrospinning techniques, in comparison with fabrication of nanoparticles, allow to obtain photocatalytic devices without usage of additional carrying base, which simplify the industrial process. However, to date there are limited publications related to the Ga2O3 electrospun nanofibers. The aim of this review is to summarize current results of gallium oxide electrospun nanofibers preparation. Special attention is given to the technological parameters of the electrospinning, the polymer solution receipts, and the properties of such nanomaterials and its potential application. Despite the limited number of publications related to Ga2O3 fibers fabrications, that data collected in this review article demonstrate great potential for practical applications.

Development of Technology for Providing Antimicrobial Properties to Medical Disposable Masks

Wearing masks to protect against communicable diseases is an effective tool used in many countries affected by the COVID-19 pandemic. The antibacterial activity, antibacterial efficiency, microbial purity, and breathability properties of medical disposable masks are very important. Ag is most commonly applied to antimicrobial textiles. In this work, three antimicrobial additives were used. Four compositions of the binders with antimicrobial additives were prepared and applied to one-layer non-woven PP material. The influence of the binder antimicrobial polymer coating on the breathability and antibacterial activity of the non-woven PP material was evaluated. The results show that the composition of the polyacrylic acid binder had the least effect on their breathability and samples with the silver chloride formulation showed the best antimicrobial response. Based on the microbiological and air permeability results of the samples of the one-layer non-woven material with coating, the samples of two layers and three layers of the medical mask model were prepared. Microbiological studies have shown that a three-layered medical mask model with silver chloride composition in the middle layer, on both sides of the model, has antibacterial efficiency against three pathogens (E. Coli, K. Pneumoniae, and S. Aureus). The performance of this medical mask model has been found to meet the requirements for type I medical masks according to the EN 14863 standard. Studies have shown that the microbial purity of the mask model is CFU/g < 3.

Study on the effect of structural parameters of a thermal liner on its thermal protective performance under radiant heat exposure

To comprehend the impact of elementary construction parameters of nonwoven thermal liners on their thermal protective performance, the current research primarily emphasizes on studying the effect of needle penetration depth and needle punch density of the thermal liner. Nonwoven fabrics with three different punch densities and three needling depths were prepared. The air permeability and thermal resistance of the thermal liner were investigated through regression analysis to determine the influence of needle penetration depth and needle punch density. It was observed that both factors had a notable impact on the air permeability and thermal resistance of the thermal liner. An increase in needle penetration depth and needle punch density resulted in a decrease in the air permeability and thermal resistance of the thermal liner. An experiment was carried out utilizing the 33 Box-Behnken designing approach; the factors employed were the radiant heat flux intensity, needle punch density, and needle penetration depth of the thermal liner. The thermal protective performance of thermal liners was measured at three discrete intensities of radiant heat exposures. To investigate the effect of the test and construction parameters and their interaction, an analysis of variance study was carried out. It was observed that protection time rises with the decrease in needling depth and needle punch density at every level of heat flux. With the rise in incident radiant heat flux, protection time declines, irrespective of needle penetration depth and punch density levels.

Predictive analysis of electroconductive material parameters for system optimisation

This paper presents mathematical modelling based on predictive and correlation analysis of independent and dependent variables of conductive materials to develop sensors or actuators. The resulting analysis and optimisation develop improved systems based on sensors or actuators, including selecting the appropriate conductive materials for development. Toward this purpose, 46 materials with electroconductive properties were selected and analysed. The independent variables considered were mass, air permeability and thickness, and the dependent variable was defined as the electrical surface resistance of the conductive fabric used.

Advanced X/γ-Ray-Shielding Materials Enabled by the In Situ Generation of Cerium-Tungsten Nanoparticles Within Regenerated Collagen Fibers.

Advanced X- and γ-ray-shielding materials are conventionally designed and fabricated via the uniform dispersion of high-Z elements into the substrate. These soluble high-Z elements considerably reduced the particle size of functional components; however, the as-obtained composites exhibited weak absorption region at 40-80keV and poor water resistance. To address these issues, such materials are fabricated by introducing cerium and tungsten into regenerated collagen fibers (RCFs) using a "dual impregnation-desolvation" strategy. The uniform dispersion of functional components is achieved via the in situ generation of cerium-tungsten nanoparticles (CeW NPs) under multiple impregnating and desolvating cycles; as a result, the CeW NPs achieved an ultrasmall particle size of 17.15nm. Benefiting from the ultrasmall particle size and uniform dispersion of CeW NPs, the fabricated CeW-RCF composites exhibit satisfactory X- and γ-ray-shielding capabilities with an ultrahigh mass attenuation coefficient (MAC) of 5.9cm2g-1 at 83keV, higher than that of lead plates. The CeW-RCF composites also exhibit outstanding mechanical strength, low density, and high air permeability, demonstrating their superior wearability. This work provides novel insights into the design and fabrication of advanced X- and γ-ray-shielding materials with high radiation-shielding performance and enhanced wearability.

The influence of unconventional assembly techniques on the comfort indicators of waterproof materials

The present paper aims to highlight the correlations between the comfort indicators of waterproof cotton-based fabrics, and the specific parameters of unconventional assembly technology. The materials considered include layers of Gore-Tex film, serving as substitutes for waterproof materials, intended to manufacture outerwear products such as protective equipment (jackets and overalls), which are breathable waterproof membranes. The comfort indicator values were obtained through standardised methods, and data processing and representation in two-dimensional (2D) and three-dimensional (3D) systems using correlation/graphing methods were carried out in Excel software, and using Jandel Table Curve 3D v2. Although experimental research can be extended to include specific functions related to durability indicators, this study focused theoretically and experimentally on how the variation in temperature of the low-pressure hot air jet can lead to changes in the vaporization coefficient, air permeability index, and thermal conductivity coefficient. The relationship between the comfort indicator values (thermal conductivity coefficient, air permeability index, and vapour permeability coefficient) of the considered materials and the treatment parameters of the installation (pressure, temperature, velocity) is expressed through statistically adequate mathematical models, highlighted by a correlation coefficient R = 0.983, with significance certified by the Fischer test. The study of comfort indicators was conducted under optimized treatment parameters, ensuring durability and presentation value functions in the treatment zone remain unchanged compared to those of the base materials.

Industrial workwear for hot workplace environments by coating with metal–organic framework NH2-MIL-125 (Ti): synthesis, characterization, coating, thermal conductivity coefficient and air permeability

Industrial workwear for hot workplace environments by coating with metal–organic framework NH2-MIL-125 (Ti): synthesis, characterization, coating, thermal conductivity coefficient and air permeability

Evaluation of alternative joining methods in softshell fabric types

Parameters such as high performance, durability and comfort are very important in protective and sports clothing produced to increase the technical or functional properties of clothing products, as well as aesthetic and decorative features. Fabrics that provide comfort to the user by regulating body temperature, protect against harsh weather conditions, and are waterproof and windproof, as well as breathable, are used for these purposes. One of the most important fabrics with these features is the fabric called ‘softshell’. Softshell is a fabric specially created to release moisture and regulate body temperature. Therefore, the outer layer of the softshell is not waterproof, but water-repellent, ensuring that it remains dry and protective while a person is wearing it. Creating a three-dimensional product from a two-dimensional fabric with these features is achieved through the sewing process. As traditional methods are used in the sewing process, an alternative joining method called ‘ultrasonic joining’ can also be used. While alternative joining methods provide joining without sewing thread, these methods do not create holes in the fabric surfaces since there is no sewing needle. Joining processes with thermal, laser and ultrasound energy are based on the principle of melting, fusing and cooling the joined surfaces. In this study, it was aimed to analyze the change in the physical properties of different softshell fabrics as a result of joining them with classical and innovative sewing/joining methods. In this context, lockstitch, lockstitch & tape welding, ultrasonic welding, and ultrasonic welding & tape welding are applied to the softshell, ripstop softshell and Lycra softshell fabrics used in the market. The thickness, air permeability, seam strength and elongation at break properties of the bonded fabrics were examined. Within the scope of this study, obtaining successful results in softshell fabric types, which is one of the bulky fabrics, contributes to the idea that the usage area of ultrasonic welding will expand day by day.

Effect of Cr content on the high temperature oxidation behavior of FeCoNiMnCrx porous high-entropy alloys

FeCoNiMnCr porous high-entropy alloys were prepared using the activation reaction sintering method with Fe, Co, Ni, Mn, and Cr as raw materials. The oxidation behaviors of FeCoNiMnCrx porous high-entropy alloys with different Cr contents, such as pore structure, the surface oxide film phase composition, structure, and morphology, were characterized by X-ray diffraction (XRD), electron probe micro analysis (EPMA), energy dispersive X-ray spectroscopy (EDS), and pore tester after high-temperature oxidation at 800–1000 °C. The results indicate that the initial porous high-entropy alloy comprises a single FCC solid solution phase. With the increase in Cr content, the average pore diameter, average porosity, and air permeability of the porous high-entropy alloy also increase. The oxidation kinetics of the porous high-entropy alloy after exposure to temperatures between 800 °C and 1000 °C follows a single-stage parabolic evolution law. At the same oxidation temperature, With the increase of Cr content, the oxidation gains gradually increased, at the same Cr content at different temperatures, the antioxidant performance of 1000 °C was the weakest, followed by 800 °C, and 900 °C showed excellent antioxidant performance. The oxidation products are mainly Mn2O3, Mn3O4, (Mn, Cr)3O4, Cr2O3and Fe2O3.

Sound environment design using flexible wood-based sound absorbers

A sound-absorbing material made of flexible wooden boards with air permeability was developed to improve the indoor sound environment of buildings. The flexible wood-based material has sound absorbing characteristics with the Helmholtz resonator by its air permeability. In other words, various sound absorption characteristics could be realized owing to the cross-sectional shape (flat or curved) and machining conditions (cut width, cut pitch, and plate thickness). In this paper, the application of flexible wood-based sound-absorbing materials to acoustic design in actual buildings (nursery schools and a church) where acoustic considerations are required is presented. In their application to a newly built nursery school, one of the considerations was to prevent the loss of design by installing sound-absorbing materials. In their application to acoustic renovation, the sound environment improvement effect was confirmed by measuring sounds before and after the installation, and it was also confirmed that the users were able to feel the improvement effect. These results will lead to the development of sound-absorbing wooden boards as an interior material and the promotion of the use of wood in buildings to contribute to the realization of a decarbonized society.

Low-frequency broadband acoustic ventilation meta-barrier based on consecutive multiple Fano resonances

Acoustic metamaterials utilizing Fano resonance provide the possibility of simultaneous airborne sound insulation and high-performance ventilation. However, the ultra-sharp line shape results in a narrow working frequency range, which is still insufficient for practical applications. In this work, we propose a low-frequency acoustic meta-barrier supporting consecutive multiple Fano resonances (CMFRs) with broadband (~75%) capability, efficient ventilation, and ultra-thin thickness, etc. The barrier features a binary metastructure, incorporating a chiral space coiling tunnel and a hollow pipe in a planar arrangement. This configuration offers discrete and continuous states within the composed Fano system, corresponding to the tunnel and the pipe, respectively. By means of superposition of multi-order Fano resonance modes, the destructive interference between the discrete and continuum states keeps effective in a broad frequency range, while simultaneously achieving high air permeability. Numerical results of transmission loss show significant attenuation of incident energy in the range of 479-1032 Hz. Our work lays the groundwork for next generation of Fano-based metamaterial applications, with far-reaching implications for noise control and related fields.

Life Cycle Assessment (LCA) of Single Jersey Knitted Fabrics Containing Recycled Cotton Fiber and Fabric Performance

This study investigates the life cycle assesment of single jersey knitted fabrics containing recycled cotton and their some performance properties. In the yarn production stage fibers obtained from waste through mechanical recycling (pre-consumer recycle) were used in blends at 10%, 15%, and 20% to produce knitted fabrics. Some performance properties such as fabric stiffness, air permeability, and dimensional change, which are important in the usage properties of jersey knitted fabrics, were compared. Within the scope of the study, the environmental impact of the use of recycled raw materials was evaluated with LCA. According to the Life Cycle Analysis (LCA) results, the use of recycled cotton with contributions ranging from 10% to 20% instead of 100% original cotton demonstrated significant improvements in resource depletion (fossil fuels), global warming, ozone layer depletion, toxic impact on human life, toxic impact on freshwater life, toxic impact on terrestrial life, and total water usage.

Fluorine-free biomimetic membranes with leaf vein-like and lotus leaf dual structure for high-performance waterproof and breathable textiles

Intelligent microporous membranes with excellent water resistance and moisture permeability have a huge market demand owing to their wide applications in personal protection, outdoor equipment and wearable electronics. However, the construction of such high-performance waterproof and moisture-permeable membranes (WBMs) based on a simple preparation process without post-coating treatment presents significant challenges. Herein, we present a simple strategy for constructing a fluorine-free polyethylene terephthalate (PET)-based WBM with a novel composite structure by combining a leaf vein-like nanofibrous substrate membrane and lotus leaf-inspired biomimetic nanofibrous skin using multi-needle electrospinning and heat treatment techniques. Surface hydrophobicity, along with the stable crosslinked structure of PET-based membranes, was achieved by in-suit doping of fluorine-free two-component reactive silicone rubber (PDMS). In addition, the small pore size and high porosity of the composite membranes were regulated by co-assembling PET/PDMS fibers and microspheres with different morphologies and structures. The resulting composite membranes based on substrate membrane-1:3 (BNFM-1:3) achieved excellent waterproof performance of 90.3 kPa, good moisture permeability of 5116 g m−2 d−1, and air permeability of 1.82 mm s−1. The WBMs based on novel composite structures are expected to be applied in various fields because of their ideal comprehensive performance.

Graphene oxide/polydopamine interface co-reinforced carbon paper: With comprehensive mechanical properties, electrical conductivity and air permeability

Proton Exchange Membrane Fuel Cell ( PEMFC) are characterised by their cleanliness, efficiency and lack of pollution. Carbon paper, the fundamental material for constructing gas-diffusion layer (GDL), plays a crucial role in electron transmission, supporting the electrode structure, and proton transport. However, the traditional carbon paper for GDL significantly limits the large-scale commercial application of PEMFC due to its low mechanical strength and poor conductivity. Based on this, in this paper, polydopamine is used to modify primary carbon fiber paper, a homogeneous mixed solution of graphene oxide and phenolic resin is used as the impregnating agent, and the effects of different GO concentrations on the properties of carbon paper are investigated. The results show that the graphitization degree and mechanical properties of carbon paper are improved with the increase of GO concentration. When the content of polydopamine is 2 g/L and the concentration of GO is 0.5 wt%, the carbon paper exhibits optimal performance. The air permeability of carbon paper is 12.18 L/min, the resistivity is 13.5 mΩ·cm, and the tensile strength is 19.3 MPa. This study provides a simple method for preparing highly breathable and highly conductive carbon paper, offering a reference for achieving low-cost and high-performance carbon paper production, and facilitating the large-scale commercial production of carbon paper.

Research on high-velocity ballistic impact of para-aramid sateen fabric with ZnO nanorods oriented to the development of soft body armor

This study introduces an innovative approach of utilizing ZnO nanorod growing technology to the sateen fabric in order to improve its ballistic performance. Through SEM, FTIR, XRD and XPS analyses, ZnO nanorods with majority length of 1000–1500 nm and fineness of 200–600 nm have been deposited on the surface of sateen fabric surface Compared the fabric with ZnO nanorods (S-11-Nrs) with its neat counterpart, the mechanical properties of S-11-Nrs are increased, especially the inter-filament friction and fabric tensile breaking strength. However, in the impact process, the number of filaments involved in the impact is reduced and the filaments are mainly failure by the shear action of the bullets. Due to these positive and negative effects, the energy absorption of S-11-Nrs displays inferior ballistic energy absorption. Nevertheless, at lower areal density, in the non-perforation test, S-11-Nrs presents less BFS and shows better resistance to the consecutive shotting process compared with the neat fabric. The reason is that the increase of inter-filament friction limits the movement of filaments and thus results in less BFS. In addition, the flexibility, air permeability and moisture permeability are still kept. This research offers valuable insights for the design and development of comfortable soft body armor.

Investigating energy performance of build-to-rent buildings in england

The domestic sector made up 16% of UK’s total greenhouse gas emissions in 2021. The build-to-rent market is experiencing a rapid expansion, but the energy performance and distinctiveness of this building sector are still generally undiscovered. Therefore, 423 build-to-rent flats from three build-to-rent developments in England were evaluated with top-down approach. Energy use intensities of flats were compared against domestic energy benchmarks and design targets. Possible determinants of energy consumption in build-to-rent flats, including EPC rating, number of bedrooms, air permeability, glazing area and glazing orientation were investigated through correlation analyses. Research discovers discrepancy between actual energy performance of the studied flats and design targets supporting UK’s 2050 net zero target. In this case study, number of bedrooms is identified as the most noticeable factor influencing energy consumption. Results of this study provide an introductory insight of the build-to-rent sector and serve as a starting point to encourage further exploration. Practical application This paper specifically focuses on build-to-rent buildings within the domestic sector. Energy use situations of build-to-rent flats in the UK were investigated with actual measured data provided by a build-to-rent developer. Results demonstrate the discrepancy between energy use in the build-to-rent flats being studied and existing domestic benchmarks. This paper provides insights to researchers, building developers and policymakers regarding the energy performance of this upsurging build-to-rent building sector and its associated influencing factors. It also contributes ideas on the importance of data sharing and development of energy benchmarking of the build-to-rent sector.