Electrospun nanofibres can outperform their melt-blown counterparts in many applications, especially air filtration. The different filtration mechanisms of nanofibres are particularly important when it comes to the air filtration of viruses (such as COVID-19) and bacteria. In this work, we present an electrospun nanofibre filter media, FilterLayr^TM by NanoLayr Ltd., containing poly(methyl methacrylate)/ethylene vinyl alcohol nanofibres. The outstanding uniformity of the nanofibres was indicated by the good correlation between pressure drop (ΔP) and areal weight with R2 values in the range of 0.82 to 0.98 across various test air velocities. By adjusting the nanofibre areal weight (basis weight), the nanofibre filter media was shown to meet the particle filtration efficiency and breathability requirements of the following internationally accepted facemask and respirator standards: N95 respirator facemask performance in accordance with NIOSH 42CFR84 (filtration efficiency of up to 98.10% at a pressure drop of 226 Pa and 290 Pa at 85 L·min⁻¹ and 120 L·min⁻¹, respectively), Level 2 surgical facemask performance in accordance with ASTM F2299 (filtration efficiency of up to 99.97% at 100 nm particle size and a pressure drop of 44 Pa at 8 L·min⁻¹), and Level 2 filtration efficiency and Level 1 breathability for barrier face coverings in accordance with ASTM F3502 (filtration efficiency of up to 99.68% and a pressure drop of 133 Pa at 60 L·min⁻¹), with Level 2 breathability being achievable at lower nanofibre areal weights. Full article

Chitosan has garnered much interest due to its properties and possible applications. Every year the number of publications and patents based on this polymer increase. Chitosan exhibits poor solubility in neutral and basic media, limiting its use in such conditions. Another serious obstacle is directly related to its natural origin. Chitosan is not a single polymer with a defined structure but a family of molecules with differences in their composition, size, and monomer distribution. These properties have a fundamental effect on the biological and technological performance of the polymer. Moreover, some of the biological properties claimed are discrete. In this review, we discuss how chitosan chemistry can solve the problems related to its poor solubility and can boost the polymer properties. We focus on some of the main biological properties of chitosan and the relationship with the physicochemical properties of the polymer. Then, we review two polymer applications related to green processes: the use of chitosan in the green synthesis of metallic nanoparticles and its use as support for biocatalysts. Finally, we briefly describe how making use of the technological properties of chitosan makes it possible to develop a variety of systems for drug delivery. Full article

This study proposed a dynamic forming mechanism development of the negative Poisson’s ratio elastomer molds—plate to plate (P2P) forming process. To dynamically stretch molds and control the microstructural shape, the proposal is committed to using the NPR structure as a regulatory mechanism. The NPR structural and dynamic parallel NPR-molds to control microstructure mold-cores were simulated and analyzed. ANSYS and MATLAB were used to simulate and predict dynamic NPR embossing replication. The hot-embossing and UV-curing dynamic NPR P2P-forming systems are designed and developed for verification. The results illustrated that the dynamic forming mechanism of the negative Poisson’s ratio elastomer molds proposed by this study can effectively control microstructure molds. This can effectively predict and calculate the geometrical characteristics of the microstructures after embossing. The multi-directional dynamic NPR microstructural replication process can accurately transfer microstructures and provide high transfer rate-replication characteristics. Full article

This paper investigates the use of a Magnetite Polydimethylsiloxane (PDMS) Graphene array sensor in ultra-wide band (UWB) spectrum for microwave imaging applications operated within 4.0–8.0 GHz. The proposed array microwave sensor comprises a Graphene array radiating patch, as well as ground and transmission lines with a substrate of Magnetite PDMS-Ferrite, which is fed by 50 Ω coaxial ports. The Magnetite PDMS substrate associated with low permittivity and low loss tangent realized bandwidth enhancement and the high conductivity of graphene, contributing to a high gain of the UWB array antenna. The combination of 30% (ferrite) and 70% (PDMS) as the sensor’s substrate resulted in low permittivity as well as a low loss tangent of 2.6 and 0.01, respectively. The sensor radiated within the UWB band frequency of 2.2–11.2 (GHz) with great energy emitted in the range of 3.5–15.7 dB. Maximum energy of 15.7 dB with 90 × 45 (mm) in small size realized the integration of the sensor for a microwave detection system. The material components of sensor could be implemented for solar panel. Full article

The thermally conductive structural film adhesive not only carries large loads but also exhibits excellent heat-transfer performance, which has huge application prospects. Herein, a novel epoxy (Ep) thermally conductive structural film adhesive was prepared using polyphenoxy (PHO) as the toughening agent and film former, boron nitride (BN) nanosheets as the thermally conductive filler, and polyester fabric as the carrier. When the amount of PHO in the epoxy matrix was 30 phr and the content of nano-BN was 30 wt.% (Ep/PHO30/nBN30), the adhesive resin system showed good film-forming properties, thermal stability, and thermal conductivity. The glass transition temperature of Ep/PHO30/nBN30 was 215 °C, and the thermal conductivity was 209.5% higher than that of the pure epoxy resin. The Ep/PHO30/nBN30 film adhesive possessed excellent adhesion and peeling properties, and the double-lap shear strength at room temperature reached 36.69 MPa, which was 21.3% higher than that of pure epoxy resin. The double-lap shear strength reached 15.41 MPa at 150 °C, demonstrating excellent high temperature resistance. In addition, the Ep/PHO30/nBN30 film adhesive exhibited excellent heat-aging resistance, humidity, and medium resistance, and the shear strength retention rate after exposure to the complicated environment reached more than 90%. The structural film adhesive prepared showed excellent fatigue resistance in the dynamic load fatigue test, the double-lap shear strength still reached 35.55 MPa after 1,000,000 fatigue cycles, and the strength retention rate was 96.9%, showing excellent durability and fatigue resistance. Full article

Flexible piezoelectric nanogenerators have attracted great attention due to their ability to convert ambient mechanical energy into electrical energy for low-power wearable electronic devices. Controlling the microstructure of the flexible piezoelectric materials is a potential strategy to enhance the electrical outputs of the piezoelectric nanogenerator. Three types of flexible polyvinylidene fluoride (PVDF) piezoelectric nanogenerator were fabricated based on well-aligned nanofibers, random oriented nanofibers and thick films. The electrical output performance of PVDF nanogenerators is systematically investigated by the influence of microstructures. The aligned nanofiber arrays exhibit highly consistent orientation, uniform diameter, and a smooth surface, which possesses the highest fraction of the polar crystalline β phase compared with the random-oriented nanofibers and thick films. The highly aligned structure and the large fraction of the polar β phase enhanced the output performance of the well-aligned nanofiber nanogenerator. The highest output voltage of 14 V and a short-circuit current of 1.22 µA were achieved under tapping mode of 10 N at 2.5 Hz, showing the potential application in flexible electronic devices. These new results shed some light on the design of the flexible piezoelectric polymer-based nanogenerators. Full article

The dependence of the conductivity and electric modulus of silver/polyacrylonitrile nanocomposites on the frequency of an alternating electric field has been studied at different temperatures and starting mixture AgNO₃ contents. The frequency dependences on the conductivity of the nanocomposites in the range of 10³–10⁶ Hz are in good agreement with the power law f^0.8. The observed relaxation maxima in the relation of the imaginary part of the electric modulus on the frequency can be explained by interfacial polarization. It was shown that the frequency dispersions of conductivity and electric modulus were well described by the Dyre and Cole-Davidson models, respectively. Using these models, we have estimated the relaxation times and the activation energies of these structures. A mechanism of charge transport responsible for the conductivity of nanocomposites is proposed. An assumption is made regarding the presence of Ag₄²⁺ and Ag₈²⁺ silver clusters in the polymer. Full article

Previous studies have reported that poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymers can exhibit large electrostrictive strains depending on the filler. This work examines the electrostrictive and structural properties of P(VDF-HFP) nanofibers modified with conductive polymer polyaniline (PANI). The P(VDF-HFP)/PANI composite nanofibers were prepared by an electrospinning method with different PANI concentrations (0, 0.5, 1, 1.5, 3 and 5 wt.%). The average diameter, water contact angle and element were analyzed by SEM, WCA and EDX, respectively. The crystalline, phase structure and mechanical properties were investigated by XRD, FTIR and DMA, respectively. The dielectric properties and electrostrictive behavior were also studied. The results demonstrated that the composite nanofibers exhibited uniform fibers without any bead formation, and the WCA decreased with increasing amount of PANI. However, a high dielectric constant and electromechanical response were obtained. The electrostrictive coefficient, crystalline, phase structure, dielectric properties and interfacial charge distributions increased in relation to the PANI content. Moreover, this study indicates that P(VDF-HFP)/PANI composite nanofibers may represent a promising route for obtaining electrostrictive composite nanofibers for actuation applications, microelectromechanical systems and sensors based on electrostrictive phenomena. Full article

The wide availability and diversity of dangerous microbes poses a considerable problem for health professionals and in the development of new healthcare products. Numerous studies have been conducted to develop membrane filters that have antibacterial properties to solve this problem. Without proper protective filter equipment, healthcare providers, essential workers, and the general public are exposed to the risk of infection. A combination of nanotechnology and biosorption is expected to offer a new and greener approach to improve the usefulness of polysaccharides as an advanced membrane filtration material. Nanocellulose is among the emerging materials of this century and several studies have proven its use in filtering microbes. Its high specific surface area enables the adsorption of various microbial species, and its innate porosity can separate various molecules and retain microbial objects. Besides this, the presence of an abundant OH groups in nanocellulose grants its unique surface modification, which can increase its filtration efficiency through the formation of affinity interactions toward microbes. In this review, an update of the most relevant uses of nanocellulose as a new class of membrane filters against microbes is outlined. Key advancements in surface modifications of nanocellulose to enhance its rejection mechanism are also critically discussed. To the best of our knowledge, this is the first review focusing on the development of nanocellulose as a membrane filter against microbes. Full article

There have been considerable recent technological developments for implant overdenture attachments. This study presents an overview of the biomechanical and biomolecular aspects of various attachments for implant overdenture. Available articles on attachments for implant overdenture were reviewed from January 1980 to August 2021 in the ScienceDirect, MEDLINE/PubMed, and Web of Science resources, and relevant studies were included in this study. We focused on the following topics: attachment systems, retention of various attachments, stress distribution with different attachments, the design and fabrication of attachments, digital techniques in overdenture attachments, and the effects of attachments in peri-implant health. We found that plastic resin is commonly used for ball and bar attachments, whereas nylon resin is commonly used in locator attachments. The locator system offers a valuable attachment option for implant-retained overdenture. Attachment retention reduces while lateral force increases with implant inclination in overdenture. The higher the retention of an overdenture attachment, the higher the transferred stresses. Additionally, clip loading produces more stress in implants and precision elements than bar-retained dentures. As such, we conclude that the ball and locator systems the best overdenture systems due to their superior tissue response, survival rate, and patient satisfaction. Full article

Nanocellulose, typically cellulose nanocrystals (CNCs), has excellent properties and is widely used. In particular, CNC has a small dimension, high chemical reactivity, and high sustainability, which makes it an excellent candidate as a starting material to be converted into nanocellulose derivatives. Chemical modification is essential for obtaining the desired products; the modifications create different functional attachment levels and generate novel microstructures. Recent advances on nanocellulose derivatives have not yet been reviewed and evaluated for the last five years. Nanocellulose derivative materials are being used in a wide variety of high-quality functional applications. To meet these requirements, it is essential for researchers to fully understand CNCs and derivative materials, precisely their characteristics, synthesis methods, and chemical modification approaches. This paper discusses CNC and its derivatives concerning the structural characteristics, performance, and synthesis methods, comparing the pros and cons of these chemical modification approaches reported in recent years. This review also discusses the critical physicochemical properties of CNC derivative products, including solubility, wetting performance, and associated impacts on properties. Lastly, this paper also comments on the bottlenecks of nanocellulose derivatives in various applications and briefly discusses their future research direction. Full article

This work aimed to research the efficiency of gamma irradiation and shielding characteristics on the lead oxide (PbO) doped the crosslinked polystyrene-b-polyethyleneglycol (PS-b-PEG) block copolymers and polystyrene-b-polyethyleneglycol-boron nitride (PS-b-PEG-BN) nanocomposites materials. The crosslinked PS-b-PEG block copolymers and PS-b-PEG-BN nanocomposites mixed with different percentage rates of PbO were used to research gamma-ray shielding characteristics. The synthesis of the copolymer was done by emulsion polymerization methods. The characterization and morphological analyses of irradiated samples were explored handling with the Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared Spectroscopy (FTIR), Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA), and Scanning Electron Microscope (SEM) methods. The gamma-rays that were emitted from the $E_{ }^{152}u$ source were observed with a High Purity Germanium (HPGe) detector system and examined with a GammaVision computer program. Our samples, including the different percentage rates of the PS-b-PEG (1000, 1500, 10,000), BN, and PbO, were irradiated in various gamma-ray photon energy regions (from 121.78 keV to 1408.01 keV). Then, Linear-Mass Attenuation Coefficients (LACs-MACs), Half-Tenth Value Layer (HVL), Mean Free Path (MFP), and Radiation Protection Efficiency (RPE) values of the samples were calculated. Via crosschecking the acquired data from samples with and without PbO and BN, it was observed that, if the different percentage rates by weight nano-powder of PbO and BN are added in the polymer mixture, it can be used as a convenient shielding material against gamma rays. Full article

Poly (lactic acid) (PLA)-Poly (propylene carbonate) (PPC) block copolymer compatibilizers are produced in incompatible 70wt%PLA/PPC blend by initiating transesterification with addition of 1% of tetra butyl titanate (TBT) or by chain extension with addition of 2% of 2,4-toluene diisocyanate (TDI). The above blends can have much better mechanical properties than the blend without TBT and TDI. The elongation at break is dramatically larger (114% with 2% of TDI and 60% with 1% of TBT) than the blend without TDI and TBT, with a slightly lower mechanical strength. A small fraction of the copolymer is likely formed in the PLA/PPC blend with addition of TBT, and a significant amount of the copolymer can be made with addition of TDI. The copolymer produced with TDI has PPC as a major content (~70 wt%) and forms a miscible interphase with its own Tg. The crystallinity of the blend with TDI is significantly lower than the blend without TDI, as the PLA blocks of the copolymer in the interphase is hardly to crystallize. The average molecular weight increases significantly with addition of TDI, likely compensating the lower mechanical strength due to lower crystallinity. Material degradation can occur with addition of TBT, but it is very limited with 1% of TBT. However, compared with the blends without TBT, the PLA crystallinity of the blend with 1%TBT increases sharply during the cooling process, which likely compensates the loss of mechanical strength due to the slightly material degradation. The added TDI does not have any significant impact on PLA lamellar packing, but the addition of TBT can make PLA lamellar packing much less ordered, presumably resulted from much smaller PPC domains formed in the blend due to better compatibility. Full article

In this study, a series of crosslinked membranes were prepared as solid polymer electrolytes (SPEs) for all-solid-state lithium ion batteries (ASSLIBs). An epoxy-containing copolymer (glycidyl methacrylate-co-poly(ethylene glycol) methyl ether methacrylate, PGA) and two amine curing agents, linear Jeffamine ED2003 and hyperbranched polyethyleneimine (PEI), were utilized to prepare SPEs with various crosslinking degrees. The PGA/polyethylene oxide (PEO) blends were cured by ED2003 and PEI to obtain slightly and heavily crosslinked structures, respectively. For further optimizing the interfacial and the electrochemical properties, an interlocking bilayer membrane based on overlapping and subsequent curing of PGA/PEO/ED2003 and PEO/PEI layers was developed. The presence of this amino/epoxy network can inhibit PEO crystallinity and maintain the dimensional stability of membranes. For the slightly crosslinked PGA/PEO/ED2003 membrane, an ionic conductivity of 5.61 × 10⁻⁴ S cm⁻¹ and a lithium ion transference number (tLi⁺) of 0.43 were obtained, along with a specific capacity of 156 mAh g⁻¹ (0.05 C) acquired from an assembled half-cell battery. However, the capacity retention retained only 54% after 100 cycles (0.2 C, 80 °C), possibly because the PEO-based electrolyte was inclined to recrystallize after long term thermal treatment. On the other hand, the highly crosslinked PGA/PEO/PEI membrane exhibited a similar ionic conductivity of 3.44 × 10⁻⁴ S cm⁻¹ and a tLi⁺ of 0.52. Yet, poor interfacial adhesion between the membrane and the cathode brought about a low specific capacity of 48 mAh g⁻¹. For the reinforced interlocking bilayer membrane, an ionic conductivity of 3.24 × 10⁻⁴ S cm⁻¹ and a tLi⁺ of 0.42 could be achieved. Moreover, the capacity retention reached as high as 80% after 100 cycles (0.2 C, 80 °C). This is because the presence of the epoxy-based interlocking bilayer structure can block the pathway of lithium dendrite puncture effectively. We demonstrate that the unique interlocking bilayer structure is capable of offering a new approach to fabricate a robust SPE for ASSLIBs. Full article

Edible coatings have recently been developed and applied to different food matrices, due to their numerous benefits, such as increasing the shelf life of foods, improving their appearance, being vehicles of different compounds, such as extracts or oils of various spices that have antioxidant and antimicrobial activity, as well as being friendly to the environment. The objective of this research was to develop a new edible coating based on chitosan enriched with peppermint extract and to evaluate its effectiveness to inhibit microbial development in vitro and improve both the quality and shelf life of common carp (Cyprinus carpio) during refrigerated storage (4 ± 1 °C). Three treatments were used: edible coating (C + EC), edible coating +, 5% chitosan (C + ECCh) and edible coating + 1.5% chitosan + 10% peppermint (C + ECChP). Prior the coating carp fillets; the antibacterial activity and antioxidant capacity were evaluated in the peppermint extract and coating solutions. After coating and during storage, the following were determined on the fillet samples: microbiological properties, observed for ECP, an inhibition halo of 14.3 mm for Staphylococcus aureus, not being the case for Gram-negative species, for ECCh, inhibition halos of 17.6 mm, 17.1 mm and 16.5 mm for S. aureus, Salmonella typhimurium and Escherichia coli, respectively; for the ECChP, inhibition halos for S. aureus, S. typhimurium and E. coli of 20 mm, 17 mm and 16.8 mm, respectively. For the physicochemical characteristics: an increase in solubility was observed for all treatments during storage, reaching 46.7 mg SN protein/mg total protein for the control, and values below 29.1 mg SN protein/mg total protein (p < 0.05), for fillets with EC (C + EC > C + ECCh > C + ECChP, respectively at the end of storage. For the pH, maximum values were obtained for the control of 6.4, while for the fillets with EC a maximum of 5.8. For TVB-N, the fillets with different CE treatments obtained values (p < 0.05) of 33.3; 27.2; 25.3 and 23.3 mg N/100 g (control > C + E C > C + ECCh > C + ECChP respectively). Total phenolic compounds in the aqueous peppermint extract were 505.55 mg GAE/100 g dried leaves, with 98.78% antioxidant capacity in the aqueous extract and 81.88% in the EC. Biomolecule oxidation (hydroperoxide content) had a significant increase (p < 0.05) in all treatments during storage, 1.7 mM CHP/mg protein in the control, to 1.4 in C + EC, 1.27 in C + ECCh and 1.16 in C + ECChP; TBARS assay values increased in the different treatments during refrigerated storage, with final values of 33.44, 31.88, 29.40 and 29.21 mM MDA/mg protein in the control; C + EC; C + ECCh and C + ECChP respectively. In SDS -PAGE a protective effect was observed in the myofibrillar proteins of fillets with ECChP). The results indicate that the C + ECCh and C + ECChP treatments extend the shelf life of 3–5 days with respect to microbiological properties and 4–5 days with respect to physicochemical characteristics. A reduction in lipid and protein oxidation products was also observed during refrigerated storage. With these findings, this is considered a promising method to increase the shelf life of fish fillets combined with refrigeration and we are able to recommend this technology for the fish processing industry. Full article