Comparative Study of Dielectric Properties of Hybrid Natural Fiber Composites

N-S co-doping lignin-based carbon magnetic nanoparticles as high performance supercapacitor and electromagnetic wave absorber

Recently, multifunctional lignin-based materials are gaining more and more attention due to their great potential for low-cost and sustainability. In this work, to obtain both an excellent supercapacitor electrode and an outstanding electromagnetic wave (EMW) absorber, a series of multifunctional nitrogen-sulphur (N-S) co-doped lignin-based carbon magnetic nanoparticles (LCMNPs) had been successfully prepared through Mannich reaction at different carbonization temperature. As compared with the directly carbonized lignin carbon (LC), LCMNPs had more nano-size structure and higher specific surface area. Meanwhile, with the increase of carbonization temperature, the graphitization of the LCMNPs could also be effectively improved. Therefore, LCMNPs-800 displayed the best performance advantages. For the electric double layer capacitor (EDLC), the optimal specific capacitance of LCMNPs-800 reached 154.2 F/g, and the capacitance retention after 5000 cycles was as high as 98.14 %. When the power density was 2204.76 W/kg, the energy density achieved 33.81 Wh/kg. In addition, N-S co-doped LCMNPs also exhibited strong electromagnetic wave absorption (EMWA) ability, whose the minimum reflection loss (RL) value of LCMNPs-800 was realized -46.61 dB at 6.01 GHz with an thickness of 4.0 mm, and the effective absorption bandwidth (EAB) was up to 2.11 GHz ranging from 5.10 to 7.21 GHz, which could cover the C-band. Overall, this green and sustainable approach is a promising strategy for the preparation of high-performance multifunctional lignin-based materials.

Advances in Biodegradable Electronic Skin: Material Progress and Recent Applications in Sensing, Robotics, and Human-Machine Interfaces

The rapid growth of the electronics industry and proliferation of electronic materials and telecommunications technologies has led to the release of a massive amount of untreated electronic waste (e-waste) into the environment. Consequently, catastrophic environmental damage at the microbiome level and serious human health diseases threaten the natural fate of the planet. Currently, the demand for wearable electronics for applications in personalized medicine, electronic skins (e-skins), and health monitoring is substantial and growing. Therefore, "green" characteristics such as biodegradability, self-healing, and biocompatibility ensure the future application of wearable electronics and e-skins in biomedical engineering and bioanalytical sciences. Leveraging the biodegradability, sustainability, and biocompatibility of natural materials will dramatically influence the fabrication of environmentally friendly e-skins and wearable electronics. Here, the molecular and structural characteristics of biological skins and artificial e-skins are discussed. The focus then turns to the biodegradable materials, including natural and synthetic-polymer-based materials, and their recent applications in the development of biodegradable e-skin in wearable sensors, robotics, and human-machine interfaces (HMIs). Finally, the main challenges and outlook regarding the preparation and application of biodegradable e-skins are critically discussed in a near-future scenario, which is expected to lead to the next generation of biodegradable e-skins.

Recent Development in the Processing, Properties, and Applications of Epoxy-Based Natural Fiber Polymer Biocomposites

Growing environmental concerns have increased the scientific interest in the utilization of natural fibers for the development of epoxy biocomposite materials. The incorporation of one or more fibers in the production of hybrid epoxy polymer composites has been a subject of discussion. It is interesting to acknowledge that natural/synthetic fiber hybridized epoxy composites have superior properties over natural/natural fiber hybridized epoxy composites. Significant efforts have been devoted to the improvement of natural fiber surface modifications to promote bonding with the epoxy matrix. However, to achieve sufficient surface modification without destroying the natural fibers, optimization of treatment parameters such as the concentration of the treatment solution and treatment time is highly necessary. Synthetic and treated natural fiber hybridization in an epoxy matrix is expected to produce biocomposites with appreciable biodegradability and superior mechanical properties by manipulating the fiber/matrix interfacial bonding. This paper presents a review of studies on the processing of epoxy natural fiber composites, mechanical properties, physical properties such as density and water absorption, thermal properties, biodegradability study, nondestructive examination, morphological characterizations, and applications of epoxy-based natural fiber biocomposites. Other aspects, including a review of variables that enhance the mechanical and functional performance of epoxy/natural fibers composites while also increasing the biodegradability of the composite material for environmental sustainability, were presented. The future research focus was elucidated. It is hoped that this review will stimulate and refocus research efforts toward advancing the manufacture of epoxy/natural fiber composites to meet the growing demand for biocomposite materials in the global world.

Recent Progress on Natural Fibers Mixed with CFRP and GFRP: Properties, Characteristics, and Failure Behaviour

Research on natural-fiber-reinforced polymer composite is continuously developing. Natural fibers from flora have received considerable attention from researchers because their use in biobased composites is safe and sustainable for the environment. Natural fibers that mixed with Carbon Fiber and or Glass Fiber are low-cost, lightweight, and biodegradable and have lower environmental influences than metal-based materials. This study highlights and comprehensively reviews the natural fibers utilized as reinforcements in polyester composites, including jute, bamboo, sisal, kenaf, flax, and banana. The properties of composite materials consisting of natural and synthetic fibers, such as tensile strength, flexural strength, fatigue, and hardness, are investigated in this study. This paper aims to summarize, classify, and collect studies related to the latest composite hybrid science consisting of natural and synthetic fibers and their applications. Furthermore, this paper includes but is not limited to preparation, mechanism, characterization, and evaluation of hybrid composite laminates in different methods and modes. In general, natural fiber composites produce a larger volume of composite, but their strength is weaker than GFRP/CFRP even with the same number of layers. The use of synthetic fibers combined with natural fibers can provide better strength of hybrid composite.

Scalable Polyimide-Poly(Amic Acid) Copolymer Based Nanocomposites for High-Temperature Capacitive Energy Storage

The developments of next-generation electric power systems and electronics demand for high temperature (≈150 °C), high energy density, high efficiency, scalable, and low-cost polymer-based dielectric capacitors are still scarce. Here, the nanocomposites based on polyimide-poly(amic acid) copolymers with a very low amount of boron nitride nanosheets are designed and synthesized. Under the actual working condition in hybrid electric vehicles of 200 MV m^-1 and 150 °C, a high energy density of 1.38 J cm^-3 with an efficiency higher than 96% is achieved. This is about 2.5 times higher than the room temperature energy density (≈0.39 J cm^-3 under 200 MV m^-1 ) of the commercially used biaxially oriented polypropylene, the benchmark of dielectric polymer. Especially, the energy density and efficiency at 150 °C show no sign of degradation after 20 000 cycles of charge-discharge test and 35 days' high-temperature endurance test. This research provides an effective and low-cost strategy to develop high-temperature polymer-based capacitors.

Dielectric, Thermal and Water Absorption Properties of Some EPDM/Flax Fiber Composites

This paper deals with the dielectric and sorption properties of some flax fiber-reinforced ethylene-propylene-diene monomer (EPDM) composites containing different fiber loadings as well as their behavior after exposure to different doses of electron beam irradiation. Three relaxation processes were evinced, a weak relaxation β at sub-Tg temperatures and two α-type relaxations above the Tg. The EPDM/flax composites exhibited higher values of dielectric constant, dielectric loss and conductivity as compared to a pristine EPDM sample. Using thermogravimetric analysis (TG) coupled with Fourier transform infrared spectroscopy (FTIR) and mass spectrometry (MS) (TG/FTIR/MS system), the degradation products can be identified. The water uptake increased as the flax fiber level increased in composites. The water uptake tests of irradiated composites showed that the highest water content was obtained for a flax fiber level of 20 phr.

Biomedical and Tissue Engineering Strategies to Control Foreign Body Reaction to Invasive Neural Electrodes

Neural-interfaced prostheses aim to restore sensorimotor limb functions in amputees. They rely on bidirectional neural interfaces, which represent the communication bridge between nervous system and neuroprosthetic device by controlling its movements and evoking sensory feedback. Compared to extraneural electrodes (i.e., epineural and perineural implants), intraneural electrodes, implanted within peripheral nerves, have higher selectivity and specificity of neural signal recording and nerve stimulation. However, being implanted in the nerve, their main limitation is represented by the significant inflammatory response that the body mounts around the probe, known as Foreign Body Reaction (FBR), which may hinder their rapid clinical translation. Furthermore, the mechanical mismatch between the consistency of the device and the surrounding neural tissue may contribute to exacerbate the inflammatory state. The FBR is a non-specific reaction of the host immune system to a foreign material. It is characterized by an early inflammatory phase eventually leading to the formation of a fibrotic capsule around intraneural interfaces, which increases the electrical impedance over time and reduces the chronic interface biocompatibility and functionality. Thus, the future in the reduction and control of the FBR relies on innovative biomedical strategies for the fabrication of next-generation neural interfaces, such as the development of more suitable designs of the device with smaller size, appropriate stiffness and novel conductive and biomimetic coatings for improving their long-term stability and performance. Here, we present and critically discuss the latest biomedical approaches from material chemistry and tissue engineering for controlling and mitigating the FBR in chronic neural implants.

Biodegradable Materials for Sustainable Health Monitoring Devices

The recent advent of biodegradable materials has offered huge opportunity to transform healthcare technologies by enabling sensors that degrade naturally after use. The implantable electronic systems made from such materials eliminate the need for extraction or reoperation, minimize chronic inflammatory responses, and hence offer attractive propositions for future biomedical technology. The eco-friendly sensor systems developed from degradable materials could also help mitigate some of the major environmental issues by reducing the volume of electronic or medical waste produced and, in turn, the carbon footprint. With this background, herein we present a comprehensive overview of the structural and functional biodegradable materials that have been used for various biodegradable or bioresorbable electronic devices. The discussion focuses on the dissolution rates and degradation mechanisms of materials such as natural and synthetic polymers, organic or inorganic semiconductors, and hydrolyzable metals. The recent trend and examples of biodegradable or bioresorbable materials-based sensors for body monitoring, diagnostic, and medical therapeutic applications are also presented. Lastly, key technological challenges are discussed for clinical application of biodegradable sensors, particularly for implantable devices with wireless data and power transfer. Promising perspectives for the advancement of future generation of biodegradable sensor systems are also presented.

Novel biodegradable low-κ dielectric nanomaterials from natural polyphenols

Biodegradable natural polymers and macromolecules for transient electronics have great potential to reduce the environmental footprint and provide opportunities to create emerging and environmentally sustainable technologies. Creating complex electronic devices from biodegradable materials requires exploring their chemical design pathways to use them as substrates, dielectric insulators, conductors, and semiconductors. While most research exploration has been conducted using natural polymers as substrates for electronic devices, a very few natural polymers have been explored as dielectric insulators, but they possess high dielectric constants. Herein, for the first time, we have demonstrated a natural polyphenol-based nanomaterial, derived from tannic acid as a low-κ dielectric material by introducing a highly nanoporous framework with a silsesquioxane core structure. Utilizing natural tannic acid, porous “raspberry-like” nanoparticles (TA-NPs) are prepared by a sol–gel polymerization method, starting from reactive silane unit-functionalized tannic acid. Particle composition, thermal stability, porosity distribution, and morphology are analyzed, confirming the mesoporous nature of the nanoparticles with an average pore diameter ranging from 19 to 23 nm, pore volume of 0.032 cm³ g⁻¹ and thermal stability up to 350 °C. The dielectric properties of the TA-NPs, silane functionalized tannic acid precursor, and tannic acid are evaluated and compared by fabricating thin film capacitors under ambient conditions. The dielectric constants (κ) are found to be 2.98, 2.84, and 2.69 (±0.02) for tannic acid, tannic acid-silane, and TA-NPs, respectively. The unique chemical design approach developed in this work provides us with a path to create low-κ biodegradable nanomaterials from natural polyphenols by weakening their polarizability and introducing high mesoporosity into the structure.

The first study on biodegradable low-κ dielectric nanomaterials with a silsesquioxane framework is demonstrated utilizing a natural polyphenol, tannic acid.

Preparation and Characterization of Semi-Flexible Substrates from Natural Fiber/Nickel Oxide/Polycaprolactone Composite for Microstrip Patch Antenna Circuitries for Microwave Applications

The study intended to utilizing waste organic fiber for low-cost semi-flexible substrate fabrication to develop microstrip patch antennas for low band communication applications. All the semi-flexible substrates (12.2 wt. % OPEFF/87.8 wt. % PCL, 12.2 wt. % NiO/87.8 wt. % PCL, and 25 wt. % OPEFF/25 wt. % NiO/50 wt. % PCL) were fabricated by oil palm empty fruit fiber (OPEFF) mixed with nickel oxide (NiO) nanoparticles reinforced with polycaprolactone (PCL) as a matrix using a Thermo Haake blending machine. The morphology and crystalized structure of the substrates were tested using Fourier transform infrared (FTIR) spectrometry, X-ray diffraction (X-RD) technique, and scanning electron microscopy (SEM), respectively. The thermal stability behavior of the substrates was analyzed using thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) thermogram. The dielectric properties were characterized by an open-ended coaxial probe (OEC) connected with Agilent N5230A PNA-L Network Analyzer included the 85070E2 dielectric software at frequency range of 8 to 12 GHz. The experimental results showed that NiO/OPEFF/PCL composites exhibit controllable permittivity dielectric constant εr′(f) between 1.89 and 4.2 (Farad/meter, (F/m)), with loss factor εr′′(f) between 0.08 and 0.62 F/m, and loss tangent (tan δ) between 0.05 and 0.18. Return losses measurement of the three patch antennas OPEFF/PCL, NiO/PCL, and OPEFF/NiO/PCL are −11.93, −14.2 and −16.3 dB respectively. Finally, the commercial software package, Computer Simulation Technology Microwave Studio (CSTMWS), was used to investigate the antenna performance by simulate S-parameters based on the measured dielectric parameters. A negligible difference is found between the measured and simulated results. Finally, the results obtained encourage the possibility of using natural fibers and nickel oxide in preparation of the substrates utilize at microwave applications.

Computational and Experimental Approaches for Determining Scattering Parameters of OPEFB/PLA Composites to Calculate the Absorption and Attenuation Values at Microwave Frequencies

This article describes attenuation and absorption measurements using the microstrip transmission line technique connected with a microwave vector network analyzer (Agilent 8750B). The magnitudes of the reflection (S₁₁) and transmission (S₂₁) coefficients obtained from the microstrip transmission line were used to determine the attenuation and absorption of oil palm empty fruit bunch/polylactic acid (OPEFB/PLA) composites in a frequency range between 0.20 GHz and 12 GHz at room temperature. The main structure of semi-flexible substrates (OPEFF/PLA) was fabricated using different fiber loading content extracted from oil palm empty fruit bunch (OPEFB) trees hosted in polylactic acid (PLA) using the Brabender blending machine, which ensured mixture homogeneity. The commercial software package, Computer Simulation Technology Microwave Studio (CSTMWS), was used to investigate the microstrip line technique performance by simulating and determine the S₁₁ and S₂₁ for microwave substrate materials. Results showed that the materials’ transmission, reflection, attenuation, and absorption properties could be controlled by changing the percentage of OPEFB filler in the composites. The highest absorption loss was calculated for the highest percentage of filler (70%) OPEFB at 12 GHz to be 0.763 dB, while the lowest absorption loss was calculated for the lowest percentage of filler 30% OPEFB at 12 GHz to be 0.407 dB. Finally, the simulated and measured results were in excellent agreement, but the environmental conditions slightly altered the results. From the results it is observed that the value of the dielectric constant (εr′) and loss factor (εr″) is higher for the OPEFB/PLA composites with a higher content of OPEFB filler. The dielectric constant increased from 2.746 dB to 3.486 dB, while the loss factor increased from 0.090 dB to 0.5941 dB at the highest percentage of 70% OPEFB filler. The dielectric properties obtained from the open-ended coaxial probe were required as input to FEM to calculate the S₁₁ and S₂₁ of the samples.

Jute Based Bio and Hybrid Composites and Their Applications

The popularity of jute-based bio and hybrid composites is mainly due to an increase in environmental concerns and pollution. Jute fibers have low cost, high abundance, and reasonable mechanical properties. Research in all-natural fibers and composites have increased exponentially due to the environment concerns of the hazards of synthetic fibers-based composites. Jute based bio and hybrid composites have been extensively used in number of applications. Hybrid jute-based composites have enhanced mechanical and physical properties, reasonably better than jute fiber composites. A detailed analysis of jute-based bio and hybrid composites was carried out in this review. The primary aim of this review paper is to provide a critical analysis and to discuss all recent developments in jute-based composites. The content covers different aspects of jute-based composites, including their mechanical and physical properties, structure, morphology, chemical composition, fiber modification techniques, surface treatments, jute based hybrid composites, limitations, and applications. Jute-based composites are currently being used in a vast number of applications such as in textiles, construction, cosmetics, medical, packaging, automobile, and furniture industries.

Materials and Devices for Biodegradable and Soft Biomedical Electronics

Biodegradable and soft biomedical electronics that eliminate secondary surgery and ensure intimate contact with soft biological tissues of the human body are of growing interest, due to their emerging applications in high-quality healthcare monitoring and effective disease treatments. Recent systematic studies have significantly expanded the biodegradable electronic materials database, and various novel transient systems have been proposed. Biodegradable materials with soft properties and integration schemes of flexible or/and stretchable platforms will further advance electronic systems that match the properties of biological systems, providing an important step along the path towards clinical trials. This review focuses on recent progress and achievements in biodegradable and soft electronics for biomedical applications. The available biodegradable materials in their soft formats, the associated novel fabrication schemes, the device layouts, and the functionality of a variety of fully bioresorbable and soft devices, are reviewed. Finally, the key challenges and possible future directions of biodegradable and soft electronics are provided.

Biodegradable Polymeric Materials in Degradable Electronic Devices

Biodegradable electronics have great potential to reduce the environmental footprint of devices and enable advanced health monitoring and therapeutic technologies. Complex biodegradable electronics require biodegradable substrates, insulators, conductors, and semiconductors, all of which comprise the fundamental building blocks of devices. This review will survey recent trends in the strategies used to fabricate biodegradable forms of each of these components. Polymers that can disintegrate without full chemical breakdown (type I), as well as those that can be recycled into monomeric and oligomeric building blocks (type II), will be discussed. Type I degradation is typically achieved with engineering and material science based strategies, whereas type II degradation often requires deliberate synthetic approaches. Notably, unconventional degradable linkages capable of maintaining long-range conjugation have been relatively unexplored, yet may enable fully biodegradable conductors and semiconductors with uncompromised electrical properties. While substantial progress has been made in developing degradable device components, the electrical and mechanical properties of these materials must be improved before fully degradable complex electronics can be realized.

A Review on Natural Fiber Reinforced Polymer Composite and Its Applications

Natural fibers are getting attention from researchers and academician to utilize in polymer composites due to their ecofriendly nature and sustainability. The aim of this review article is to provide a comprehensive review of the foremost appropriate as well as widely used natural fiber reinforced polymer composites (NFPCs) and their applications. In addition, it presents summary of various surface treatments applied to natural fibers and their effect on NFPCs properties. The properties of NFPCs vary with fiber type and fiber source as well as fiber structure. The effects of various chemical treatments on the mechanical and thermal properties of natural fibers reinforcements thermosetting and thermoplastics composites were studied. A number of drawbacks of NFPCs like higher water absorption, inferior fire resistance, and lower mechanical properties limited its applications. Impacts of chemical treatment on the water absorption, tribology, viscoelastic behavior, relaxation behavior, energy absorption flames retardancy, and biodegradability properties of NFPCs were also highlighted. The applications of NFPCs in automobile and construction industry and other applications are demonstrated. It concluded that chemical treatment of the natural fiber improved adhesion between the fiber surface and the polymer matrix which ultimately enhanced physicomechanical and thermochemical properties of the NFPCs.