Fiber Mats Research Articles

Highly sensitive ratiometric fluorescent fiber matrices for oxygen sensing with micrometer spatial resolution

AbstractOxygen (O2)-sensing matrices are promising tools for the live monitoring of extracellular O2 consumption levels in long-term cell cultures. In this study, ratiometric O2-sensing membranes were prepared by electrospinning, an easy, low-cost, scalable, and robust method for fabricating nanofibers. Poly(ε-caprolactone) and poly(dimethyl)siloxane polymers were blended with tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) dichloride, which was used as the O2-sensing probe, and rhodamine B isothiocyanate, which was used as the reference dye. The functionalized scaffolds were morphologically characterized by scanning electron microscopy, and their physicochemical profiles were obtained by Fourier transform infrared spectroscopy, thermogravimetric analysis, and water contact angle measurement. The sensing capabilities were investigated by confocal laser scanning microscopy, performing photobleaching, reversibility, and calibration curve studies toward different dissolved O2 (DO) concentrations. Electrospun sensing nanofibers showed a high response to changes in DO concentrations in the physiological-pathological range from 0.5% to 20% and good stability under ratiometric imaging. In addition, the sensing systems were highly biocompatible for cell growth promoting adhesiveness and growth of three cancer cell lines, namely metastatic melanoma cell line SK-MEL2, breast cancer cell line MCF-7, and pancreatic ductal adenocarcinoma cell line Panc-1, thus recreating a suitable biological environment in vitro. These O2-sensing biomaterials can potentially measure alterations in cell metabolism caused by changes in ambient O2 content during drug testing/validation and tissue regeneration processes. Graphic abstract

Investigation of alignment and layup optimization of recycled carbon fiber mats on mechanical and electromagnetic shielding properties of composites

AbstractExcellent recycled carbon fiber (rCF) was obtained using a thermally activated oxide semiconductor process. An alignment device was manufactured based on wet‐laid technology. It was used to investigate the effect of various alignment nozzle parameters on the degree of alignment of rCF mats. The mechanical, electrical conductivity and EMI shielding properties of composites reinforced by rCF mats with different layup structures were analyzed. The results showed that the optimal alignment parameters for rCF aligned mats included a convex nozzle shape, a nozzle diameter of 3 mm, a nozzle channel length of 50 mm, a nozzle up‐and‐down diameter ratio of 7:1, a nozzle departure height of 20 mm. These settings achieved a preferential alignment degree (PAD) of 93.07%. The design of layup structures for rCF mats with optimized fiber alignment fully exploits the material's anisotropic characteristics. The rCF‐0/EP composite material exhibited the highest tensile strength (195.45 MPa), while the rCF‐04/EP composite material not only demonstrated the highest flexural strength (247.95 MPa) but also showed excellent electromagnetic interference (EMI) performance (47.97 dB). The results of the research laid a theoretical foundation and provides scientific guidance for high‐value reuse of rCF.Highlights Utilized rCF as a reinforcing material for CFRP composites. Preparation of rCF aligned mats with high PAD. Effect of different layup structures on rCF aligned mat reinforced composites. rCF aligned mats improve mechanical properties and EMI properties of composites.

A highly sensitive stretchable constraint fiber mat sensor with tailored near-zero Poisson’s ratio for very early stage of battery over charge/overdischarge monitoring

Battery state monitoring is crucial for safe operation and efficient management of lithium-ion battery (LIB) systems, but early stage of timely and accurate diagnosis remains challenging. Herein, we propose to utilize a highly sensitive stretchable strain sensor to in-situ monitor the slight strain variation of cells during charge and discharge, through which the state of the battery can be accurately reflected. The high sensing capability is realized by tailoring the Poisson’s ratio of low-modulus conductive fiber mats through a facile constraint manner. The non-uniform strain distribution together with the near-zero Poisson’s ratio synergistically result in the superior sensing performance, including ultralow strain detection limit (0.006%), high strain sensitivity particularly under small strains (gauge factor of 116.1 between 0 and 2% strain), and high strain resolution under large deformations. When being practically utilized for LIB monitoring, the constraint fiber mat sensor can produce instant resistance response reflecting the cell capacity, and offer timely warning signal once the cell is overcharged or overdischarged. The developed stretchable strain sensor possesses comprehensive advantages of low mechanical constraint, tailorable small size, easy integration and conformality to cells, and little temperature interference, which would serve as a promising candidate for future battery state analysis and safety monitoring.

Thermal degradation and fire retardant behaviour of natural fibre reinforced polymeric composites- A comprehensive review

In this comprehensive review, we dive into the potential of natural fibre composites, tracing their historical use spanning three millennia and their recent incorporation into polymer matrices. Various natural fibres, including flax, hemp, jute, and more, have been explored as potential reinforcements due to their renewable nature and environmental appeal. Moreover, these fibers are gaining traction in industries such as automotive and packaging. Leveraging abundant agricultural waste such as, wheat husk, rice husk, straw, and hemp fibre into commercially viable fibre-reinforced polymer composites. A thorough summary is given in this article of the diverse array of natural fibers, their current research status, encompassing properties, processing techniques, filler materials on structural factors, thermogravimetric analysis, dynamic mechanical performance under thermal loading, fire retardant behaviour, cone calorimetric analysis and various other applications, all while referencing the latest developments in the field, exploring a sustainable future with natural fibre composites. Furthermore, the difficulties associated with natural fibre-reinforced composites, including their vulnerability to humidity, fire retardancy and compliance with fibre matrices, are examined. This paper summarizes the complex field of natural fibre composites and covers several thermal stability-related appearance.

Mechanical properties and design of hybrid composites of carbon and jute fibers with polypropylene

Natural fibers have both environmentally friendly and ecological advantages in the fiber material industry. Improving the mechanical properties and durability of natural fiber composites is an important research approach. As one of the representatives of synthetic fibers, carbon fiber has excellent mechanical properties and chemical stability, but its high cost and low toughness limit further application. Combining environmentally friendly, low-cost natural fibers with carbon fibers can broaden the development of natural fiber-reinforced composites in industrial applications. In this paper, the composites made of jute fibers and polypropylene (PP) as well as carbon fibers coupled with KH550 modification were prepared and their properties were investigated. By introducing a macroscopic model similar to the core-shell structure, an environmentally friendly material with better mechanical properties was achieved, with carbon fiber woven fabric serving as the shell and jute fiber mat as the core. The results show that a low-cost hybrid composite was successfully prepared by using a small amount of carbon fiber woven fabric instead of jute fiber mat, and the tensile, flexural and impact properties of the composites were improved by 488.27%, 70.75% and 463.39%, respectively, compared with those of the pure jute fibers composites. This study provides a rapid and reliable approach to improve the mechanical properties of the natural fiber composites.

The investigation of flame-retardant fiber mats for high performance composites: flame retardancy and structure performance

The flame-retardant performance of carbon fiber reinforced composites serves as a critical metric for structural stability. Nonetheless, the prevalent methodologies for improving the flame retardancy of composites struggle to reconcile the dual objectives of flame retardancy and mechanical robustness, due in part to the constraints imposed by the conventional additive-based approach on the material interface. This study introduced a novel method involving a glass fiber mat, which was augmented with a polyurethane-based treatment integrated with flame-retardant substances, in particular ammonium polyphosphate and nickel hydroxide. This fiber mat was strategically applied to the composite surface, conferring both flame retardancy and enhanced structural resilience. The structure performance and flame retardancy of composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and the cone calorimeter test. Experimental comparisons with nontreated controls indicated that the innovative composites exhibited a reduction in total heat release and total smoke production by 13.7% and 18.8%, respectively. Concurrently, a notable enhancement in mechanical properties was observed, with increases of 20.9% and 23.1% for tensile and flexural strength. This well-balanced performance is attributable to the structure design, with toughened glass fiber mats to protect the composite surfaces from structural failure, and flame-retardant agent composition for combustion resistance and smoke suppression. Consequently, the proposed integrative flame-retardant structural design, enriched with specific flame-retardant treatments, offers a promising avenue for fabricating high-performance composite materials with potential utility in the aviation and aerospace sectors.

Influence of bio-based kenaf polymer composites on mechanical and acoustic properties for futuristic applications: An initiative towards net-zero carbon emissions

In the pursuit of net-zero carbon emissions, the development of sustainable materials like kenaf fiber composites is pivotal. This innovative approach, which harnesses eco-friendly properties and enhances material performance, holds promise in reducing carbon footprints across diverse industries. As ecological sustainability awareness continues to rise, there is a growing imperative to embrace biodegradable, lightweight, and recyclable materials to address existing limitations in conventional materials. Kenaf fiber, with its unique electromagnetic, acoustic, mechanical, and physical properties, presents a compelling solution. The production process involves impregnating kenaf fiber with bio-based materials, utilizing nanofillers of nickel (Ni), bamboo charcoal (BC), and carbon black (CB), which are blended with epoxy resin through magnetic agitation to ensure homogeneous dispersion. This resulting composite is fortified between two layers of kenaf fiber mats, creating a robust sandwich structure. Employing response surface methodology (RSM) and the central composite design (CCD), the study calculates the optimal weight percentages of nanofillers in various test specimens. Mechanical and acoustic property testing, conducted using appropriate equipment, reveals that a combination of 15 wt% BC, 9 wt% Ni, and 6 wt% CB exhibits the highest tensile strength at 42 MPa, while the blend of 10 wt% BC, 6 wt% Ni, and 4 wt% CB achieves a maximum noise reduction coefficient (NRC) of 0.524. These impressive findings underscore the potential of this suggested material as a superior substitute for conventional materials, further aligning it with the imperative for eco-conscious and sustainable solutions.

Charging Properties of Electrospun Poly(l‐lactic acid) Submicrofiber Mat and Its Electrical Applications

Wearable pressure sensors have attracted significant attention owing to their potential applications in health monitoring and connectivity to internet‐based apps. Polymers such as poly(vinylidene fluoride) have been used in sensors. However, being petroleum‐derived materials, they do not decompose and remain in the soil when disposed. Poly(l‐lactic acid) (PLLA) is a promising material because of its biodegradable nature and its derivation from plant‐based materials. In addition, the electrospun PLLA fiber mat contains real charges and exhibits electromechanical properties. However, the detailed charging properties of the PLLA fiber mats remain unclear. Herein, the charge distribution of these fiber mat is presented, and a charging model of the fiber mat and a numerical model of the output charges from the fiber mats with electrodes are proposed. Additionally, the retention properties of the stored charges are determined using surface potential measurements at different temperatures. In addition, a self‐power‐generating touch sensor and mask‐type sensor are developed using biodegradable materials produced from biomass. These studies contribute to the improvement in the charge properties of PLLA fiber mats and the resulting wearable biodegradable sensors.

Production of AlN/CNT reinforced PVA nanofibers as a thermal conductive net for thermal interface applications

The amount of heat generated by electronic components is increasing daily, in line with their growing power and performance. Consequently, there is a heightened demand for thermal interface materials for enhanced cooling of electronics. This study employs a novel approach to fabricate a nano composite thermal interface material on copper substrates to address this challenge. The thermal interface coatings, consisting of carbon nanotubes (CNT) and aluminum nitride (AlN)-reinforced polyvinyl alcohol (PVA) nanofibers with and without an epoxy resin matrix, are fabricated using the electrospinning technique. The findings demonstrate the successful fabrication of a 2.5 µm-thick CNT/AlN-PVA nanocomposite fiber mat coating with an average fiber diameter of 318 nm onto copper substrates. Scanning electron microscope (SEM) images revealed that the AlN particles and CNTs penetrated the fibers. The successful incorporation of AlN particles into PVA fibers was also verified by the Fourier-transform infrared spectroscopy (FT-IR) spectrum of CNT/AlN-PVA nanofibers. No major weight loss was observed in the thermogravimetric (TG) analysis curves up to 200 °C, indicating the thermal stability of coatings. The thermal diffusivity of the copper substrate coated with the CNT/AlN-PVA nanocomposite fiber mat was measured at 36.6 mm2/s. Moreover, the developed CNT/AlN-PVA nanocomposite fiber mat was also applied on top of the fire-retardant epoxy resin-coated copper substrate, which is conventionally used in electronic devices to provide electrical insulation. SEM images revealed that the existence of an epoxy layer on top of copper substrates did not alter the fiber formation during the electrospinning process, and an approximately 2.5 µm-thick CNT/AlN-PVA nanofiber mat was effectively embedded in the epoxy layer after a 1-hour electrospinning process. The thermal diffusivity of the resulting epoxy matrix CNT/AlN-PVA nanofiber reinforced nanocomposite coating is determined to be 7.792 mm2/s, which is 30-fold higher compared to the thermal diffusivity of neat epoxy resin coatings (0.254 mm2/s).

PENGEMBANGAN KOMPOSIT SERAT SABUT KELAPA SEBAGAI BAHAN PEMBUATAN RANGKA SURVEILLANCE DRONE

Coconut fiber is an alternative material to replace metal. Coconut fiber was chosen because it is easy and widely found in Indonesia and is easily decomposed naturally. Even though its strength is much lower than metal, coconut fiber can be used to make objects that do not require a lot of strength, one of which is drones. In this research, coconut fiber composites were made and tensile tested to determine their strength for use as a frame for small surveillance drones. The composite is made by mixing coconut fiber mat (as fiber) and Unsaturated Polyester (as resin) using the hand lay-up method. Coconut fiber composites are tested according to ASTM D-638 standards. Based on the tensile test results in this research, it was found that the coconut fiber composite had a tensile strength of 18 MPa. Then this number is used as a benchmark in determining the size of the surveillance drone frame to be designed. Based on the results of the calculations carried out, it was found that the thickness required for a drone frame made from coconut fiber is 4 mm

Electrospun fiber mats based on chitosan-carrageenan containing Malva sylvestris anthocyanins: Physic-mechanical, thermal, and barrier properties along with application as intelligent food packaging materials

This study aimed to encapsulate Malva sylvestris extract (MSE) into chitosan-carrageenan (CH-KC) fibers using the electrospinning technique and monitor the freshness of silver carp fillets during the refrigerated storage conditions for 8 days. The CH-KC + MSE 4 % fiber mats were red at pH values lower than 3, purple at pH 4–6, dark blue at pH 7, green at pH 8–10, and brown at pH 11–12. The tensile strength, elongation at break, water vapor permeability, oxygen transmission rate, moisture content, and water solubility of fabricated fiber mats were 7.71–11.02 MPa, 13.12 %–30.00 %, 7.35–20.01 × 10−4 g mm/m2 h Pa, 3.81–8.23 cm3/m2 h, 15.74 %–27.34 %, and 3.90 %–7.56 %, respectively. Regarding the potential application of a fabricated indicator for freshness monitoring of silver carp fillets, total viable count, psychrotrophic bacterial count, pH, and total volatile basic nitrogen reached 8.91 log CFU/g, 8.03 log CFU/g, 8.10, and 40.18 mg N/100 g at the end of the study, respectively. Meanwhile, the CH-KC + MSE 4 % fiber mat color changed from white to green. These findings suggest that CH-KC + MSE 4 % fiber mats can be further utilized in the food industry to control the freshness of refrigerated silver carp fillets.

Multifunctional and recyclable aerogel/fiber building insulation composites with sandwich structure

Fire, electromagnetic (EM) pollution, and sustainability require building insulation with fire resistance, EM interference shielding, and recyclability. However, fewer building insulation materials can fulfill these multifunctional requirements. Here, we report a multifunctional building thermal insulation material with a sandwich structure that uses SiO2 aerogel powder as the insulating filler phase, α-Al2O3 fiber as the refractory reinforcing phase, and carbon fiber mat (CFF) as the electromagnetic interference shielding layer prepared by the mixing-pressing-drying method. The effects of different SiO2 aerogel power contents on fire resistance, thermal insulation, and hydrophobicity, the effects of different carbon fiber contents on EMI performance, and the effects of CFF as an interlayer on compressive strength and recyclability were investigated. The results demonstrated exceptional fire resistance properties and low thermal conductivity (0.0529 W/m·K) with a SiO2 aerogel powder content of 11.2 wt%. Specifically, the structure of the aerogel/fiber composite remains intact and the temperature of the non-heated surface is lower than 75.8 ℃ after 4 min of continuous flame combustion. It can achieve a commercial shielding standard of 20 dB at a carbon fiber content of 5 wt%. In addition, CFF as interlayers can effectively improve the compression strength of the material and solve the problem of difficult recycling of carbon fiber. In conclusion, this sandwich structure of multifunctional aerogel/fiber composites provides new ideas for the manufacture of fire resistance, energy-saving, EM-protection, and recyclable building insulation materials.

In vitro evaluation and characterization of cisplatin loaded nanofibers for local chemotherapy

Cancer is a disease that affects the quality of life of the patients that are treated with Cisplatin (CDDP), which is needed for adjuvant therapy, however it leads to many secondary and adverse effects. In this study, we manufactured and characterized poly-(lactic acid) (PLA) non-woven fibers loaded with Cisplatin (CDDP) by electrospinning technique to evaluate their cytotoxicity in in vitro assays on HeLa cells (cervical carcinoma cell line). PLA–CDDP solutions with increasing concentrations of CDDP (0.5, 1 and 2% w/w) were used in a TL-01 electrospinning equipment with the same system parameters. We analyzed the chemical, thermal and morphological characteristics of PLA and PLA–CDDP fiber mats. Furthermore, hydrolytic degradation, hemolysis and toxicity in HeLa cells were evaluated. By adding the CDDP to the fibers, the degradation, glass transition and melting temperatures were modified; the 3 µm fiber diameter of pristine PLA fibers was decreased in half the size and the degradation time was extended over 5 months. However, the hemocompatibility of the material with and without CDDP was maintained, while cytotoxicity in HeLa cells increased in the three concentrations of fiber mats of PLA–CDDP compared to the intravenous drug at 24 h (p < 0.01). We concluded that the fiber mats PLA–CDDP could be used for localized therapy in the adjuvant treatment when resection panels are expose after a surgical extirpation of solid tumors.

Utilization of response surface methodology to optimize the mechanical behaviour of flax/nano TiO2/Epoxy based hybrid composites under liquid nitrogen environment

Linum usitatissimum commonly known as flax fibers, emerges as a promising reinforcement phase for artificial polymer resins, boasting ecological benefits, low density, and easy accessibility. However, the mechanical behavior of such composites hinges crucially on factors such as fiber mat thickness, nanoTiO2 filler content, and the application of cryogenic treatment. Addressing this complex interplay, this study employs a hand lay-up technique for composite construction, subjecting nanocomposite plates to the challenging liquid nitrogen conditions at 77 K post-manufacture. Recognizing the need for an optimized approach, Response Surface Methodology (RSM) based on Box-Benhken designs is employed to enhance the mixing features of linum usitatissimum polymer composites. The study calculates anticipated mechanical strength values through rigorous ANOVA inferential analysis, uncovering the pivotal roles played by fiber mat thickness, nanofiller content, and cryogenic treatment in the two feature interactions (2FI) model components. The methodology proves robust with high R2 values (0.9670 for tensile, 0.9845 for flexural, and 0.9670 for interlaminar shear strength) consistently aligning with experimental findings. The study culminates in identifying optimized parameters for maximal mechanical properties—300 gsm flax fiber thickness, 5 wt.% nano TiO2 concentration, and a 15-min cryogenic treatment—a result that advances our understanding of fundamental factors influencing composite performance and provides practical guidelines for applications in fields requiring superior mechanical strength in challenging environments.

Predicting the tensile and compressive modulus of electrospun fiber mat‐reinforced hydrogels using the Halpin–Tsai equations

AbstractThe reinforcement of mechanically‐weak hydrogels to yield composites with increased stiffness, strength, or toughness is a well‐established approach. In particular, introducing electrospun nanofibers into hydrogels is a common strategy for biomedical applications, as the resulting hierarchical structure mimics biology and allows for control over fiber diameter and alignment and tuning of mechanical properties. However, further study of the link between the constituent materials and the mechanical properties of the composite is uncommon. One potential model to understand the mechanical properties of fiber‐reinforced hydrogels involves the Halpin–Tsai equations, which relate the modulus values of the fibers and hydrogel matrix and the fiber volume fraction, to the modulus of the composite. To assess the application of this model to fiber‐reinforced hydrogels, predicted values were compared with experimental values from mechanical testing of a poly(ethylene glycol) (PEG) matrix reinforced with an electrospun polycaprolactone (PCL) fiber mat. Although the equations described these systems well in tension, providing a facile approach to identify a fiber volume fraction that will achieve a desired modulus, the Halpin–Tsai approach was less successful under compression. This study motivates additional investigation of the role of structural features of hydrogel composites in determining mechanical properties to enable design of materials for specific applications.

Development of eco-friendly and robust structural materials via binder-free lamination of waste biomass with help of finite element method

To alleviate the environmental pressure, it is of great significance to develop the green and sustainable structural materials by utilization of waste biomass. In this work, an eco-friendly, high-strength, superhydrophobic, and thermally stable material was fabricated through a scalable binder-free lamination method using waste biomass (e.g., wood residues, crop straw, and waste paperboard). The waste biomass was separated and molded into fiber mats by a clean pulping process, and then laminated without adhesives. The finite element method (FEM) was adopted to visually observe fracture behaviors and detect the weakest zones. The utilization of FEM to enhance the mechanical strength is unique in productions of traditional biomass composites. The weakest zones were reinforced by the H2O2 spraying approach, and the flexural strength (FS) was improved from 80.12 to 120.35 MPa. The moisture content (MC) in the mat was used for regulating the softening of cellulosic fibers. In virtue of the water-induced plasticization, the laminated materials showed a high internal bonding strength (IBS) of 2.24 MPa and excellent FS of 134.81 MPa. Being benefitted from the silica modification, the materials exhibited a superhydrophobic surface with the high water contact angle (154.1°), good dimensional stability (a thickness swelling of 14.8%), and superior mechanical stability (remained 94.3% FS after two months of ultraviolet radiation). This work provides a new strategy to develop green and sustainable structural materials for buildings, furniture, and related applications.

Tailorable mechanical and degradation properties of KCl-reticulated and BDDE-crosslinked PCL/chitosan/κ-carrageenan electrospun fibers for biomedical applications: Effect of the crosslinking-reticulation synergy

The development of intricated and interconnected porous mats is desired for many applications in biomedicine and other relevant fields. The mats that comprise the use of natural, bioactive, and biodegradable polymers are the focus of current research activities. In the present work, crosslinked fibers with improved characteristics were produced by incorporating 1,4-butanediol diglycidyl ether (BDDE) into a polymer formulation containing polycaprolactone (PCL), chitosan (CS), and κappa-carrageenan (κ-C). A slight variation of formic acid (FA)/acetic acid (AA) ratio used as a solvent system, significantly affected the characteristics of the produced fiber mats. Both polysaccharides and BDDE played a major role in tailoring mechanical properties when fibrous scaffolds were reticulated under KCl-mediated basic conditions for determined periods of time at 50 °C. In vitro biological assessment of the electrospun fiber mats revealed proliferation of MC3T3-E1 cells when incubated for 1 and 7 days. After staining the cells with 4′,6-diamidino-2-phenylindole (DAPI)/rhodamine phalloidin an autofluorescence response was observed by fluorescence microscopy in the scaffold manufactured using a solvent with higher FA/AA ratio due to the formation of microfibers. The results demonstrated the potential of the BDDE-crosslinked PCL/CS/κ-C electrospun fibers as promising materials for biomedical applications that may include soft and bone tissue regeneration.

Socio-ecological risk factors associated with human flea infestations of rural household in plague-endemic areas of Madagascar.

Plague is a flea-borne fatal disease caused by the bacterium Yersinia pestis, which persists in rural Madagascar. Although fleas parasitizing rats are considered the primary vectors of Y. pestis, the human flea, Pulex irritans, is abundant in human habitations in Madagascar, and has been found naturally infected by the plague bacterium during outbreaks. While P. irritans may therefore play a role in plague transmission if present in plague endemic areas, the factors associated with infestation and human exposure within such regions are little explored. To determine the socio-ecological risk factors associated with P. irritans infestation in rural households in plague-endemic areas of Madagascar, we used a mixed-methods approach, integrating results from P. irritans sampling, a household survey instrument, and an observational checklist. Using previously published vectorial capacity data, the minimal P. irritans index required for interhuman bubonic plague transmission was modeled to determine whether household infestations were enough to pose a plague transmission risk. Socio-ecological risk factors associated with a high P. irritans index were then identified for enrolled households using generalized linear models. Household flea abundance was also modeled using the same set of predictors. A high P. irritans index occurred in approximately one third of households and was primarily associated with having a traditional dirt floor covered with a plant fiber mat. Interventions targeting home improvement and livestock housing management may alleviate flea abundance and plague risk in rural villages experiencing high P. irritans infestation. As plague-control resources are limited in developing countries such as Madagascar, identifying the household parameters and human behaviors favoring flea abundance, such as those identified in this study, are key to developing preventive measures that can be implemented at the community level.

Heat‐Resistant Air Filters Based on Self‐Sustained Electrostatic and Antibacterial Polyimide/Silver Fiber Mats

AbstractAir pollution containing microorganisms poses a major hazard to human health. It is critical to develop air filters that are both highly efficient for indoor use and suitable for use in industrial settings. Developing long‐lasting electrostatic force‐assisted filtration while keeping high‐temperature resistance and antibacterial qualities is still challenging. Here, centrifugal spinning is used to fabricate fiber mats consisting of polyimide with silver incorporation (PI/Ag). The electrostatic force remained over –700 V after 330 days. The strong electrostatic effect improves the filtration efficiency, resulting in a high PM0.3 removal efficiency of 99.1% with a low‐pressure drop of 103.67 Pa. The high filtration efficiency remains above 91.3% for PM0.3 after placing it for 330 days and heating it at 280 °C. The PI/Ag fiber mats also show antimicrobial properties against the E. coli (Gram‐negative) and S. aureus (Gram‐positive) with prominent bacteriostatic zones &gt;1.2 mm. The PI/Ag fiber mat filters are expected to have great potential for multi‐scenario air filtration.

Stress-strain behavior of square concrete columns confined with hybrid B-CSM composites and development of novel prediction models

This paper presents a comprehensive investigation into the behavior of concrete confined with hybrid Basalt and Chopped Strand Mat (B-CSM) fibers. The newly proposed B-CSM confinement technique substantially enhances the brittle compressive stress-strain behavior, leading to a noteworthy increase in peak strength (approximately 90%) and ultimate strain (approximately 461 %). The efficiency of B-CSM confinement is affected by the strength of plain concrete, with lower-strength specimens indicating a more pronounced enhancement. The performance of existing analytical models for FRP confinement in predicting ultimate strength and strain in B-CSM confined concrete is assessed, highlighting the need for tailored models. Regression-based equations are proposed for characteristic points along the stress-strain curve, enabling accurate prediction of material behavior. The predicted stress-strain curves exhibit a high level of agreement with experimental results. These findings provide valuable insights for the design and application of B-CSM confinement techniques in structural engineering, facilitating improved performance and ductility of concrete structures under compressive loading conditions.