Characterization of dielectric properties of nanocellulose from wood and algae for electrical insulator applications

Effects of the Charge Density of Nanopapers Based on Carboxymethylated Cellulose Nanofibrils Investigated by Complementary Techniques

Cellulose nanofibrils (CNFs) with different charge densities were prepared and investigated by a combination of different complementary techniques sensitive to the structure and molecular dynamics of the system. The morphology of the materials was investigated by scanning electron microscopy (SEM) and X-ray scattering (SAXS/WAXS). The latter measurements were quantitatively analyzed yielding to molecular parameters in dependence of the charge density like the diameter of the fibrils, the distance between the fibrils, and the dimension of bundles of nanofibrils, including pores. The influence of water on the properties and the charge density is studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and broadband dielectric spectroscopy. The TGA measurements reveal two mass loss processes. The one at lower temperatures was related to the loss of water, and the second process at higher temperatures was related to the chemical decomposition. The resulting char yield could be correlated to the distance between the microfibrils. The DSC investigation for hydrated CNFs revealed three glass transitions due to the cellulose segments surrounded by water molecules in different states. In the second heating scan, only one broad glass transition is observed. The dielectric spectra reveal two relaxation processes. At low temperatures or higher frequencies, the β-relaxation is observed, which is assigned to localized fluctuation of the glycosidic linkage. At higher temperatures and lower frequencies, the α-relaxation takes places. This relaxation is due to cooperative fluctuations in the cellulose segments. Both processes were quantitatively analyzed. The obtained parameters such as the relaxation rates were related to both the morphological data, the charge density, and the content of water for the first time.

A new strategy to improve the dielectric properties of cellulose nanocrystals (CNCs): Surface modification of small molecules

Nanocellulose finds various applications in advanced electrical devices due to its impressive mechanical properties, thermal stability, and degradability. Cellulose nanocrystals (CNCs) with excellent dielectric properties may act as a fresh dielectric plastic. In this study, a new strategy of small molecule modification was used to improve the dielectric constant, breakdown strength, and band gap of the CNCs. The dipole moments, dipole density, and the anisotropic impact of surface groups on the dielectric constant were studied. The number of sulfates in the CNCs showed a gradient due to alkali treatment and sulfonation, which allowed for a controlled range of the dielectric constant of nanocellulose between 4.9 and 11.9. TEMPO oxidation (2,2,6,6-tetramethylpiperidine-1-oxyl) and cyanoethylation of the CNCs further increased the dielectric constant to 11.1 and 13.2, respectively, and the dielectric loss 10-1. By understanding and innovating organic polymer dielectrics, we can provide significant benefits to the electronics and device industries.

Structural Color from Cellulose Nanocrystals or Chitin Nanocrystals: Self-Assembly, Optics, and Applications

Widespread concerns over the impact of human activity on the environment have resulted in a desire to replace artificial functional materials with naturally derived alternatives. As such, polysaccharides are drawing increasing attention due to offering a renewable, biodegradable, and biocompatible feedstock for functional nanomaterials. In particular, nanocrystals of cellulose and chitin have emerged as versatile and sustainable building blocks for diverse applications, ranging from mechanical reinforcement to structural coloration. Much of this interest arises from the tendency of these colloidally stable nanoparticles to self-organize in water into a lyotropic cholesteric liquid crystal, which can be readily manipulated in terms of its periodicity, structure, and geometry. Importantly, this helicoidal ordering can be retained into the solid-state, offering an accessible route to complex nanostructured films, coatings, and particles. In this review, the process of forming iridescent, structurally colored films from suspensions of cellulose nanocrystals (CNCs) is summarized and the mechanisms underlying the chemical and physical phenomena at each stage in the process explored. Analogy is then drawn with chitin nanocrystals (ChNCs), allowing for key differences to be critically assessed and strategies toward structural coloration to be presented. Importantly, the progress toward translating this technology from academia to industry is summarized, with unresolved scientific and technical questions put forward as challenges to the community.

The emergence of hybrid cellulose nanomaterials as promising biomaterials

Cellulose nanomaterials (CNs) are promising green materials due to their unique properties as well as their environmental benefits. Among these materials, cellulose nanofibrils (CNFs) and nanocrystals (CNCs) are the most extensively researched types of CNs. While they share some fundamental properties like low density, biodegradability, biocompatibility, and low toxicity, they also possess unique differentiating characteristics such as morphology, rheology, aspect ratio, crystallinity, mechanical and optical properties. Therefore, numerous comparative studies have been conducted, and recently, various studies have reported the synergetic advantages resulting from combining CNF and CNC. In this review, we initiate by addressing the terminology used to describe combinations of these and other types of CNs, proposing "hybrid cellulose nanomaterials" (HCNs) as the standardized classifictation for these materials. Subsequently, we briefly cover aspects of properties-driven applications and the performance of CNs, from both an individual and comparative perspective. Next, we comprehensively examine the potential of HCN-based materials, highlighting their performance for various applications. In conclusion, HCNs have demonstraded remarkable success in diverse areas, such as food packaging, electronic devices, 3D printing, biomedical and other fields, resulting in materials with superior performance when compared to neat CNF or CNC. Therefore, HCNs exhibit great potential for the development of environmentally friendly materials with enhanced properties.

Harnessing Nature's Ingenuity: A Comprehensive Exploration of Nanocellulose from Production to Cutting-Edge Applications in Engineering and Sciences

Primary material supply is the heart of engineering and sciences. The depletion of natural resources and an increase in the human population by a billion in 13 to 15 years pose a critical concern regarding the sustainability of these materials; therefore, functionalizing renewable materials, such as nanocellulose, by possibly exploiting their properties for various practical applications, has been undertaken worldwide. Nanocellulose has emerged as a dominant green natural material with attractive and tailorable physicochemical properties, is renewable and sustainable, and shows biocompatibility and tunable surface properties. Nanocellulose is derived from cellulose, the most abundant polymer in nature with the remarkable properties of nanomaterials. This article provides a comprehensive overview of the methods used for nanocellulose preparation, structure-property and structure-property correlations, and the application of nanocellulose and its nanocomposite materials. This article differentiates the classification of nanocellulose, provides a brief account of the production methods that have been developed for isolating nanocellulose, highlights a range of unique properties of nanocellulose that have been extracted from different kinds of experiments and studies, and elaborates on nanocellulose potential applications in various areas. The present review is anticipated to provide the readers with the progress and knowledge related to nanocellulose. Pushing the boundaries of nanocellulose further into cutting-edge applications will be of particular interest in the future, especially as cost-effective commercial sources of nanocellulose continue to emerge.

A Review on Sustainable Inks for Printed Electronics: Materials for Conductive, Dielectric and Piezoelectric Sustainable Inks

In the last decades, the demand for electronics and, therefore, electronic waste, has increased. To reduce this electronic waste and the impact of this sector on the environment, it is necessary to develop biodegradable systems using naturally produced materials with low impact on the environment or systems that can degrade in a certain period. One way to manufacture these types of systems is by using printed electronics because the inks and the substrates used are sustainable. Printed electronics involve different methods of deposition, such as screen printing or inkjet printing. Depending on the method of deposition selected, the developed inks should have different properties, such as viscosity or solid content. To produce sustainable inks, it is necessary to ensure that most of the materials used in the formulation are biobased, biodegradable, or not considered critical raw materials. In this review, different inks for inkjet printing or screen printing that are considered sustainable, and the materials that can be used to formulate them, are collected. Printed electronics need inks with different functionalities, which can be mainly classified into three groups: conductive, dielectric, or piezoelectric inks. Materials need to be selected depending on the ink's final purpose. For example, functional materials such as carbon or biobased silver should be used to secure the conductivity of an ink, a material with dielectric properties could be used to develop a dielectric ink, or materials that present piezoelectric properties could be mixed with different binders to develop a piezoelectric ink. A good combination of all the components selected must be achieved to ensure the proper features of each ink.

Fabrication of Advanced Cellulosic Triboelectric Materials via Dielectric Modulation

The rapid rise of triboelectric nanogenerators (TENGs), which are emerging energy conversion devices in advanced electronics and wearable sensing systems, has elevated the interest in high-performance and multifunctional triboelectric materials. Among them, cellulosic materials, affording high efficiency, biodegradability, and customizability, are becoming a new front-runner. The inherently low dielectric constant limits the increase in the surface charge density. However, owing to its unique structure and excellent processability, cellulose shows great potential for dielectric modulation, providing a strong impetus for its advanced applications in the era of Internet of Things and artificial intelligence. This review aims to provide comprehensive insights into the fabrication of dielectric-enhanced cellulosic triboelectric materials via dielectric modulation. The exceptional advantages and research progress in cellulosic materials are highlighted. The effects of the dielectric constant, polarization, and percolation threshold on the charge density are systematically investigated, providing a theoretical basis for cellulose dielectric modulation. Typical dielectric characterization methods are introduced, and their technical characteristics are analyzed. Furthermore, the performance enhancements of cellulosic triboelectric materials endowed by dielectric modulation, including more efficient energy harvesting, high-performance wearable electronics, and impedance matching via material strategies, are introduced. Finally, the challenges and future opportunities for cellulose dielectric modulation are summarized.

All-Carbon Thin-Film Transistors Using Water-Only Printing

Printing thin-film transistors (TFTs) using nanomaterials is a promising approach for future electronics. Yet, most inks rely on environmentally harmful solvents for solubilizing and postprint processing the nanomaterials. In this work, we demonstrate water-only TFTs printed from all-carbon inks of semiconducting carbon nanotubes (CNTs), conducting graphene, and insulating crystalline nanocellulose (CNC). While suspending these nanomaterials into aqueous inks is readily achieved, printing the inks into thin films of sufficient surface coverage and in multilayer stacks to form TFTs has proven elusive without high temperatures, hazardous chemicals, and/or lengthy postprocessing. Using aerosol jet printing, our approach involves a maximum temperature of 70 °C and no hazardous chemicals─all inks are aqueous and only water is used for processing. An intermittent rinsing technique was utilized to address the surface adhesion challenges that limit film density of printed aqueous CNTs. These findings provide promising steps toward an environmentally friendly realization of thin-film electronics.

A mini-review on the dielectric properties of cellulose and nanocellulose-based materials as electronic components

Cellulose-based materials have the advantages of renewable, non-toxic, flexible, and strong mechanical properties, so it of is great significance to study the dielectric properties of cellulose-based materials. In this paper, we summarized the factors influencing the dielectric properties of cellulose and nanocellulose-based dielectric and the ways to change the dielectric properties, mainly exploring the methods to improve the dielectric constant of cellulose-based dielectric materials. Cellulose and nanocellulose-based dielectric need to improve the hygroscopic property, increase the flexibility and reduce dielectric loss of the composite materials. This review summarizes the current state-of-art progress of new dielectric materials for green energy storage and flexible electronic devices.

Ionic dielectrics for fully printed carbon nanotube transistors: impact of composition and induced stresses

Printed carbon nanotube thin-film transistors (CNT-TFTs) are candidates for flexible electronics with printability on a wide range of substrates. Among the layers comprising a CNT-TFT, the gate dielectric has proven most difficult to additively print owing to challenges in film uniformity, thickness, and post-processing requirements. Printed ionic dielectrics show promise for addressing these issues and yielding devices that operate at low voltages thanks to their high-capacitance electric double layers. However, the printing of ionic dielectrics in their various compositions is not well understood, nor is the impact of certain stresses on these materials. In this work, we studied three compositionally distinct ionic dielectrics in fully printed CNT-TFTs: the polar-fluorinated polymer elastomer PVDF-HFP; an ion gel consisting of triblock polymer PS-PMMA-PS and ionic liquid EMIM-TFSI; and crystalline nanocellulose (CNC) with a salt concentration of 0.05%. Although ion gel has been thoroughly studied, e-PVDF-HFP and CNC printing are relatively new and this study provides insights into their ink formulation, print processing, and performance as gate dielectrics. Using a consistent aerosol jet printing approach, each ionic dielectric was printed into similar CNT-TFTs, allowing for direct comparison through extensive characterization, including mechanical and electrical stress tests. The ionic dielectrics were found to have distinct operational dependencies based on their compositional and ionic attributes. Overall, the results reveal a number of trade-offs that must be managed when selecting a printable ionic dielectric, with CNC showing the strongest performance for low-voltage operation but the ion gel and elastomer exhibiting better stability under bias and mechanical stresses.

Nanocellulose for Paper and Textile Coating: The Importance of Surface Chemistry

Nanocellulose has received enormous scientific interest for its abundance, easy manufacturing, biodegradability, and low cost. Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) are ideal candidates to replace plastic coating in the textile and paper industry. Thanks to their capacity to form an interconnected network kept together by hydrogen bonds, nanocelluloses perform an unprecedented strengthening action towards cellulose- and other fiber-based materials. Furthermore, nanocellulose use implies greener application procedures, such as deposition from water. The surface chemistry of nanocellulose plays a pivotal role in influencing the performance of the coating: tailored surface functionalization can introduce several properties, such as gas or grease barrier, hydrophobicity, antibacterial and anti-UV behavior. This review summarizes recent achievements in the use of nanocellulose for paper and textile coating, evidencing critical aspects of coating performances related to deposition technique, nanocellulose morphology, and surface functionalization. Furthermore, beyond focusing on the aspects strictly related to large-scale coating applications for paper and textile industries, this review includes recent achievements in the use of nanocellulose coating for the safeguarding of Cultural Heritage, an extremely noble and interesting emerging application of nanocellulose, focusing on consolidation of historical paper and archaeological textile. Finally, nanocellulose use in electronic devices as an electrode modifier is highlighted.

Physicochemical Properties of Nanocellulose Isolated from Cotton Stalk Waste

In recent years, nanocellulose has become an attractive and high-value-added product. The cotton stalk is a waste product with a high cellulose content. Therefore, nanocellulose can be isolated from the cotton stalk. Properties of nanocellulose are affected by its nanoscale. In this study, the characteristics of cellulose in nanoscale were investigated. A series of cotton stalk nanocelluloses were prepared by sulfuric acid hydrolysis to study their physicochemical properties and the differences of nanocelluloses on different nanoscales. The obtained nanocelluloses were analyzed by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TA), and X-ray diffractometry (XRD). From the morphology analysis, the mean length and width of nanocelluloses were decreased to 90.5 and 7.0 nm, respectively. From the FTIR analysis, with the particle size decreasing, hydrogen bonds were broken and recombined. Acid hydrolysis mainly acted on intramolecular hydrogen bonds of cellulose macromolecules, especially on O(3)H···O(5) bonds. The crystal arrangement model of nanocellulose was investigated. From the TA analysis, the thermal property was decreased with a reduction of nanocellulose particle size. The CrI of the cotton stalk nanocellulose was the highest at up to 87.10%. The differences of cotton stalk nanocelluloses give significant changes to physicochemical behaviors at the nanoscale. The research would provide a theoretical basis for the future application of nanocelluloses.

Present Status and Future Prospects of Jute in Nanotechnology: A Review

Nanotechnology has transformed the world with its diverse applications, ranging from industrial developments to impacting our daily lives. It has multiple applications throughout financial sectors and enables the development of facilitating scientific endeavors with extensive commercial potentials. Nanomaterials, especially the ones which have shown biomedical and other health-related properties, have added new dimensions to the field of nanotechnology. Recently, the use of bioresources in nanotechnology has gained significant attention from the scientific community due to its 100 % eco-friendly features, availability, and low costs. In this context, jute offers a considerable potential. Globally, its plant produces the second most common natural cellulose fibers and a large amount of jute sticks as a byproduct. The main chemical compositions of jute fibers and sticks, which have a trace amount of ash content, are cellulose, hemicellulose, and lignin. This makes jute as an ideal source of pure nanocellulose, nano-lignin, and nanocarbon preparation. It has also been used as a source in the evolution of nanomaterials used in various applications. In addition, hemicellulose and lignin, which are extractable from jute fibers and sticks, could be utilized as a reductant/stabilizer for preparing other nanomaterials. This review highlights the status and prospects of jute in nanotechnology. Different research areas in which jute can be applied, such as in nanocellulose preparation, as scaffolds for other nanomaterials, catalysis, carbon preparation, life sciences, coatings, polymers, energy storage, drug delivery, fertilizer delivery, electrochemistry, reductant, and stabilizer for synthesizing other nanomaterials, petroleum industry, paper industry, polymeric nanocomposites, sensors, coatings, and electronics, have been summarized in detail. We hope that these prospects will serve as a precursor of jute-based nanotechnology research in the future.

Leaf-inspired homeostatic cellulose biosensors

An incompatibility between skin homeostasis and existing biosensor interfaces inhibits long-term electrophysiological signal measurement. Inspired by the leaf homeostasis system, we developed the first homeostatic cellulose biosensor with functions of protection, sensation, self-regulation, and biosafety. Moreover, we find that a mesoporous cellulose membrane transforms into homeostatic material with properties that include high ion conductivity, excellent flexibility and stability, appropriate adhesion force, and self-healing effects when swollen in a saline solution. The proposed biosensor is found to maintain a stable skin-sensor interface through homeostasis even when challenged by various stresses, such as a dynamic environment, severe detachment, dense hair, sweat, and long-term measurement. Last, we demonstrate the high usability of our homeostatic biosensor for continuous and stable measurement of electrophysiological signals and give a showcase application in the field of brain-computer interfacing where the biosensors and machine learning together help to control real-time applications beyond the laboratory at unprecedented versatility.

TEMPO-oxidized nanocellulose films derived from coconut residues: Physicochemical, mechanical and electrical properties

The present work focuses on the development of cellulose nanofibrils (CNF) film that derived from sustainable biomass resources, which potentially to work as bio-based conductive membranes that assembled into supercapacitors. The chemically purified cellulose was isolated from different parts of coconut (coconut shell and its husk) and further subjected to 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation for CNF preparation. Physicochemical properties of prepared CNFs were studied in terms of chemical characteristics & crystallinity, surface functionalities, surface morphology, and thermal properties. Both coconut shell-derived CNF and coconut husk-derived CNF fulfilled with nanocellulose's characteristics with fibres width ranged of 70-120 nm and 150-330 nm, respectively. CNF films were further prepared by solvent casting method to measure the modulus elasticity, piezoelectric and dielectric properties of the films. Mechanical study indicated that coconut shell-derived CNF film showed a higher value of elastic modulus than the coconut husk-derived CNF film, which was 8.39 GPa and 5.36 GPa, respectively. The effectiveness of electrical aspects for CNF films are well correlated with the crystallinity and thermal properties, associated with it's composition of different coconut's part.

Physicochemical Characteristics of Cellulose Nanocrystals Derived from the Residue of Filamentous Microalga Tribonema utriculosum

Tribonema biomass is considered promising biorefinery feedstock for the co-production of biodiesel and valuable bioproducts; however, the extraction of these useful compounds produces large amounts of algal residues, which produce increased environmental concerns. Herein, cellulose was extracted from the waste residue of T. utriculosum via alkalization and bleaching, followed by the production of high-value-added cellulose nanocrystals (CNCs) via acid hydrolysis. The hydrolysis was performed with 60% (wt%) H₂SO₄ at a yield of 13.31%, resulting in the generation of rod-shaped nanoparticles averaging 39.5 nm in diameter and 239.2 nm in length. The structural characterization analysis revealed that the prepared CNCs had high crystallinity (73.0%) due to the removal of non-cellulose components and amorphous regions by chemical treatment, as well as possessing good aqueous suspension stability (zeta potential = - 40.1 mV). Although the CNCs showed lower thermal stability than extracted cellulose, they spanned a broader temperature range due to two-stage degradation behaviour, with higher residue weight (16.7%). This work represents the first report on the preparation of a high-value-added industrial product, CNCs, from the filamentous microalga T. utriculosum, aiming to maximize benefits from waste algal residue reutilization.

Nanocellulosics: Benign, Sustainable, and Ubiquitous Biomaterials for Water Remediation

Water is critical for all lives to thrive. Access to potable and safe water has been argued to rank top among the prerequisites for defining the standard of living of a nation. However, there is a global decline in water quality due to human activities and other factors that severely impact freshwater resources such as saltwater intrusion and natural disasters. It has been pointed out that the millions of liters of industrial and domestic wastewater generated globally have the potential to help mitigate water scarcity if it is appropriately captured and remediated. Among the many initiatives to increase access to clean water, the scientific community has focused on wastewater remediation through the utilization of bioderived materials, such as nanocellulosics. Nanocellulosics, derived from cellulose, have the advantages of being ubiquitous, nontoxic, and excellent adsorbents. Furthermore, the surface properties of nanocellulosic materials can easily be modified. These advantages make them promising materials for water remediation applications. This perspective highlights the most important new developments in the application of nanocellulosics in water treatment technologies, such as membrane, adsorption, sensors, and flocculants/coagulants. We also identify where further work is urgently required for the widespread industrial application of nanocellulosics in wastewater treatment.

Controlled Environment Neutron Radiography of Moisture Sorption/Desorption in Nanocellulose-Treated Cotton Painting Canvases

Nanocellulose-based materials have recently been used to consolidate degraded cotton painting canvases. Canvas-supported paintings consist of materials that are sensitive to moisture and especially susceptible to environmental fluctuations in temperature and relative humidity (RH). These environmental fluctuations occur in uncontrolled environments found in historic houses and palaces and can lead to hydrolytic degradation and mechanical damage to canvases. To simulate this situation in an experimental setting, canvas samples were mounted in a custom-made closed-cell and subjected to programmed cycles of RH at a controlled temperature while exposed to the neutron beam. Results are presented for both untreated samples and those treated with a polar consolidant, cellulose nanofibrils (CNF(aq)) in water, and an apolar consolidant, a composite of persilylated methyl cellulose with surface silylated cellulose nanocrystals (MC+CNC(h)) in heptane. They were then compared with changes in ionic conductivities as measured by dielectric analysis (DEA) with the same cyclic RH program and temperature. Although the samples were exposed to the same experimental conditions, they presented treatment-specific responses. CNF-treated canvas showed higher hygroscopicity than the untreated sample and facilitated moisture diffusion across the sample to areas not exposed to the environment. A sample treated with MC+CNC(h) retarded moisture diffusion during the increase in RH and could, therefore, afford protection to moisture absorption in uncontrolled environments. Thus, the experimental setup and resulting data provide a pilot study demonstrating the potential of neutron radiography in following and comparing real-time moisture diffusion dynamics in untreated and nanocellulose-consolidated cotton canvases and assisting in validating the overall benefit of the treatment.

Micro- and Nanocellulose in Polymer Composite Materials: A Review

The high demand for plastic and polymeric materials which keeps rising every year makes them important industries, for which sustainability is a crucial aspect to be taken into account. Therefore, it becomes a requirement to makes it a clean and eco-friendly industry. Cellulose creates an excellent opportunity to minimize the effect of non-degradable materials by using it as a filler for either a synthesis matrix or a natural starch matrix. It is the primary substance in the walls of plant cells, helping plants to remain stiff and upright, and can be found in plant sources, agriculture waste, animals, and bacterial pellicle. In this review, we discussed the recent research development and studies in the field of biocomposites that focused on the techniques of extracting micro- and nanocellulose, treatment and modification of cellulose, classification, and applications of cellulose. In addition, this review paper looked inward on how the reinforcement of micro- and nanocellulose can yield a material with improved performance. This article featured the performances, limitations, and possible areas of improvement to fit into the broader range of engineering applications.

Nanocellulose: From Fundamentals to Advanced Applications

Over the past few years, nanocellulose (NC), cellulose in the form of nanostructures, has been proved to be one of the most prominent green materials of modern times. NC materials have gained growing interests owing to their attractive and excellent characteristics such as abundance, high aspect ratio, better mechanical properties, renewability, and biocompatibility. The abundant hydroxyl functional groups allow a wide range of functionalizations via chemical reactions, leading to developing various materials with tunable features. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations (particularly for the reports of the past 3 years). We start with a concise background of cellulose, its structural organization as well as the nomenclature of cellulose nanomaterials for beginners in this field. Then, different experimental procedures for the production of nanocelluloses, their properties, and functionalization approaches were elaborated. Furthermore, a number of recent and emerging uses of nanocellulose in nanocomposites, Pickering emulsifiers, wood adhesives, wastewater treatment, as well as in new evolving biomedical applications are presented. Finally, the challenges and opportunities of NC-based emerging materials are discussed.

Morphological and Electrical Properties of Nanocellulose Compounds and Its Application on Capacitor Assembly

The rise for innovation in the electrical industry is strongly driven by development of new materials. Features of new materials are changing design paradigms for engineers. In this paper, the electrical properties of films of cellulose nanocrystals were measured. It was found that humidity affects the dielectric strength on the cellulose nanocrystals (CNCs). The dielectric strength was similar to the value of the industrial dielectric paper. The addition of plasticizer improved the flexibility of the material but lowered the dielectric strength. The films of CNC had an ordered arrangement, as suggested by the iridescence shown by them. The humidity content of the films was measured by thermogravimetric analysis. The CNC film was used for assembling a capacitor and compared to a capacitor assembled with dielectric paper.

Dielectric response of hydrated water as a structural component of nanofibrillated cellulose (NFC) from different plant sources

The current work illuminates the interplay between nanofibrillated cellulose (NFC) films and hydrated water. The NFC films from three sources of technological importance, i.e. cotton, wood and flax, are compared. It is shown that cellulose materials present slight variations in supramolecular structure depending on the plant origin. The structural differences determine both quantity and state of the water adsorbed by cellulose. Dielectric spectroscopy was employed to study the state of hydrated water as a probe of both the overall and specific marks of NFCs' structure. The measurements, carried out in the wide frequency (10^-2Hz -10⁶Hz) and temperature (123 K-293 K) ranges, revealed the formation of non-interactive water clusters at low water content. At high water content, additional states of water were identified: Water in saturated glass-forming solution and bulk. These water states were shown to be determined by the NFC's structure and morphology.

Recent advances in nanoengineering cellulose for cargo delivery

The recent decade has witnessed a growing demand to substitute synthetic materials with naturally-derived platforms for minimizing their undesirable footprints in biomedicine, environment, and ecosystems. Among the natural materials, cellulose, the most abundant biopolymer in the world with key properties, such as biocompatibility, biorenewability, and sustainability has drawn significant attention. The hierarchical structure of cellulose fibers, one of the main constituents of plant cell walls, has been nanoengineered and broken down to nanoscale building blocks, providing an infrastructure for nanomedicine. Microorganisms, such as certain types of bacteria, are another source of nanocelluloses known as bacterial nanocellulose (BNC), which benefit from high purity and crystallinity. Chemical and mechanical treatments of cellulose fibrils made up of alternating crystalline and amorphous regions have yielded cellulose nanocrystals (CNC), hairy CNC (HCNC), and cellulose nanofibrils (CNF) with dimensions spanning from a few nanometers up to several microns. Cellulose nanocrystals and nanofibrils may readily bind drugs, proteins, and nanoparticles through physical interactions or be chemically modified to covalently accommodate cargos. Engineering surface properties, such as chemical functionality, charge, area, crystallinity, and hydrophilicity, plays a pivotal role in controlling the cargo loading/releasing capacity and rate, stability, toxicity, immunogenicity, and biodegradation of nanocellulose-based delivery platforms. This review provides insights into the recent advances in nanoengineering cellulose crystals and fibrils to develop vehicles, encompassing colloidal nanoparticles, hydrogels, aerogels, films, coatings, capsules, and membranes, for the delivery of a broad range of bioactive cargos, such as chemotherapeutic drugs, anti-inflammatory agents, antibacterial compounds, and probiotics. SYNOPSIS: Engineering certain types of microorganisms as well as the hierarchical structure of cellulose fibers, one of the main building blocks of plant cell walls, has yielded unique families of cellulose-based nanomaterials, which have leveraged the effective delivery of bioactive molecules.

Trends in Advanced Functional Material Applications of Nanocellulose

The need to transition to more sustainable and renewable technology has resulted in a focus on cellulose nanofibrils (CNFs) and nanocrystals (CNCs) as one of the materials of the future with potential for replacing currently used synthetic materials. Its abundance and bio-derived source make it attractive and sought after as well. CNFs and CNCs are naturally hydrophilic due to the abundance of -OH group on their surface which makes them an excellent recipient for applications in the medical industry. However, the hydrophilicity is a deterrent to many other industries, subsequently limiting their application scope. In either light, the increased rate of progress using CNCs in advanced materials applications are well underway and is becoming applicable on an industrial scale. Therefore, this review explores the current modification platforms and processes of nanocellulose directly as functional materials and as carriers/substrates of other functional materials for advanced materials applications. Niche functional attributes such as superhydrophobicity, barrier, electrical, and antimicrobial properties are reviewed due to the focus and significance of such attributes in industrial applications.

Multilayer bacterial cellulose/resole nanocomposites: Relationship between structural and electro-thermo-mechanical properties

The aim of this research was to fabricate multilayer insulator nanocomposites using phenolic resin impregnated bacterial cellulose (BC) handsheets and investigate the relationships between their structural and electro-thermo-mechanical properties. G. xylinus was incubated in a static Hestrin-Schramm culture at 28 °C for 14 days. Then, BC aqueous suspension was added to kraft pulp aqueous suspension. The content of BC that was added to the pulp suspension was as follows: 5, 10 and 15%. The disintegrated BC was turned into handsheets by a vacuum method. Dried handsheets were immersed in phenolic resin. To obtain composites, 5 immersed handsheets from each treatment were laid-up and hot pressed at 150 °C under 100 MPa pressure for 10 min. The specimens were characterized by means of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) techniques and insulating tests as dielectric loss factor and breakdown voltage. The results of thermal analysis showed an improvement in the thermal stability and an increase in the evaporation enthalpy of prepared samples with higher BC content. The mechanical examinations indicated that by increasing BC content in nanocomposites, the loss modulus and tan delta increased and the storage modulus of specimens decreased. The coefficient of thermal expansion (CTE) of samples diminished with increase of BC content. FE-SEM characterization showed different qualities of resin impregnation of the papers. The results of insulating tests confirmed that dielectric loss tangent and dielectric breakdown voltage increased in the specimens with higher BC content.

Cellulose and nanocellulose-based flexible-hybrid printed electronics and conductive composites - A review

Flexible-hybrid printed electronics (FHPE) is a rapidly growing discipline that may be described as the precise imprinting of electrically functional traces and components onto a substrate such as paper to create functional electronic devices. The mass production of low-cost devices and components such as environmental sensors, bio-sensors, actuators, lab on chip (LOCs), radio frequency identification (RFID) smart tags, light emitting diodes (LEDs), smart fabrics and labels, wallpaper, solar cells, fuel cells, and batteries are major driving factors for the industry. Using renewable and bio-friendly materials would be advantageous for both manufacturers and consumers with the increased use of (FHPE) electronics in our daily lives. This review article describes recent developments in cellulose and nanocellulose-based materials for FHPE, and the necessary developments required to propagate their use in commercial applications. The aim of these developments is to enable the creation of FHPE devices and components made almost entirely of cellulose materials.

Nested seaweed cellulose fiber deposited with cuprous oxide nanorods for antimicrobial activity

Bird's nest type architectural network of cellulosic nanofibers was extracted, with nearly 34% yield, from green filamentous seaweed Chaetomorpha antennina using mild bleaching agent. Nanorods of cuprous oxide (Cu₂O) were grown over the porous sheet, prepared from the seaweed cellulose, by one step hydrothermal method. The seaweed cellulose and Cu₂O nanorods deposited seaweed cellulose sheets, were characterized by XRD, SEM-EDX, FT-IR, TGA and tensile test. XRD revealed that seaweed cellulose acted as reducing agent, reducing CuO to Cu₂O. Morphology showed that the average diameter of seaweed cellulose and deposited Cu₂O nanorods were 30 nm and 90 nm, respectively. Cuprous oxide nanorods deposited seaweed cellulose sheet gave very good antibacterial activity towards gram-positive (Staphylococcus aureus, Streptococcus thermophilis) and gram-negative (Pseudomonas aeruginous, Escherichia coli) microbes. The Cu₂O nanorods deposited seaweed cellulose sheet can be viewed to have great potential in biomedical, packaging, biotechnological, textile, water treatment and pharmaceutical applications.

Influence of Water on the Structure and Dielectric Properties of the Microcrystalline and Nano-Cellulose

Influence of water in the different states on a structure and dielectric properties of microcrystalline cellulose were studied by of X-ray, thermogravimetry, and dielectric spectroscopy. At research of microcrystalline cellulose (MCC) with different content of water, it is shown that the molecules of water are located in the macropores of MCC and in multimolecular hydrated layers. It is shown that at the increase of concentration of water in a hydrated shell, the reorganization of molecules of cellulose in the surface of crystallites takes place, and as a result, their transversal size and crystallinity increase. It is shown that during the concentration of water, more than 13% in a continuous hydrated shell of crystallites appears. Temperature dependences of actual and imaginary parts of complex dielectric permittivity were studied in the interval of temperatures [-180 ÷ 120] °C on frequencies of f = 5, 10, 20, and 50 kHz. A low-temperature relaxation process and high-temperature transition were observed. Low-temperature relaxation process which is related to transition of surface methylol groups of molecules of cellulose conformation from tg to tt is shifted toward low temperatures at the increase of concentration of water in microcrystalline cellulose.

Nanocellulose as a sustainable biomass material: structure, properties, present status and future prospects in biomedical applications

Nanocellulose, extracted from the most abundant biomass material cellulose, has proved to be an environmentally friendly material with excellent mechanical performance owing to its unique nano-scaled structure, and has been used in a variety of applications as engineering and functional materials. The great biocompatibility and biodegradability, in particular, render nanocellulose promising in biomedical applications. In this review, the structure, treatment technology and properties of three different nanocellulose categories, i.e., nanofibrillated cellulose (NFC), nanocrystalline cellulose (NCC) and bacterial nanocellulose (BNC), are introduced and compared. The cytotoxicity, biocompatibility and frontier applications in biomedicine of the three nanocellulose categories were the focus and are detailed in each section. Future prospects concerning the cytotoxicity, applications and industrial production of nanocellulose are also discussed in the last section.

Effect of Water Vapor Adsorption on Electrical Properties of Carbon Nanotube/Nanocrystalline Cellulose Composites

It has been long known that the electrical properties of cellulose are greatly influenced by adsorption of water vapor. Incorporating conductive nanofillers in a cellulose matrix is an example of an approach to tailor their characteristics for use in electronics and sensing devices. In this work, we introduce two new nanocomposites comprising carbon nanotubes (CNTs) and conventional or electrosterically stabilized nanocrystalline celluloses matrices. While conventional nanocrystalline cellulose (NCC) consists of a rigid crystalline backbone, electrosterically stabilized cellulose (ENCC) is composed of a rigid crystalline backbone with carboxylated polymers protruding from both ends. By tuning CNT loading, we can tailor a CNT/NCC composite with minimal electrical sensitivity to the ambient relative humidity, despite the fact that the composite has a high moisture uptake. The expected decrease in CNT conductivity upon water vapor adsorption, due to electron donation, is counterbalanced by an increase in the conductivity of NCC due to proton hopping at an optimum CNT loading (1-2%). Contrary to the CNT/NCC composite, a CNT/ENCC composite at 1% CNT loading shows insulating behavior for relative humidities up to 75%, after which the composite becomes conductive. This interesting behavior can be ascribed to the low moisture uptake of ENCC at low and moderate relative humidities due to the limited number of hydroxyl groups and hydrogen bond formation between carboxyl groups on ENCC, which endow ENCC with limited water molecule adsorption sites.