This study characterized the anisotropic thermal conductivity of clay/cellulose nanocomposites, an eco-friendly functional flame-retardant material exhibiting excellent mechanical properties, gas barrier properties, and biodegradability. Thermal conductivity anisotropy is important for flame-retardant materials. Low thermal conductivity in the through-thickness direction serves as a thermal barrier, whereas high thermal conductivity in the in-plane direction prevents local heat accumulation. We prepared a series of membranes of nanocomposites of montmorillonite clay platelets and cellulose nanofibrils via vacuum filtration/drying and measured their directional thermal conductivities as a function of the montmorillonite clay/cellulose nanofibril content. The results indicate that the through-thickness and in-plane thermal conductivities depend nonmonotonically on the clay content. The highest in-plane thermal conductivity reached 7.5 W m-1 K-1, exhibiting a maximum anisotropy of 30 for a clay content of 50%. Structural investigation via Raman spectroscopy revealed an enhanced planar alignment of the cellulose nanofibrils and indicated alignment of the clay platelets. The correlation between the degree of alignment and thermal conductivity anisotropy suggests that alignment increases the contact area between the cellulose nanofibrils and clay platelets, which enhances in-plane heat conduction by increasing the phonon transport path and impedes through-thickness heat conduction by enhancing phonon boundary scattering.

Accurate evaluation of electrophysiological and morphological characteristics of the skeletal muscles is critical to establish a comprehensive assessment of the human neuromusculoskeletal function in vivo. However, current technological challenges lie in unsynchronized and unparallel operation of separate acquisition systems such as surface electromyography (sEMG) and ultrasonography. Key problem is the lack of ultrasound transparency of current electrophysiological electrodes. In this work, ultrasound (US) transparent electrode based on cellulose nanofibrils (CNF) substrate are proposed to solve the issue. US transparency of the electrodes are evaluated using a standard US phantom. The effects of nanocellulose type and ion-bond introduction on electrode performance is investigated. Simultaneous US image and sEMG signal acquisition of biceps brachii during isometric muscle contraction are studied. Reliable correlation analysis of the US and sEMG signals is realized which is rarely reported in the previous literatures. Recyclability and biodegradability of the current electrode are evaluated. The reported technology opens up new pathways to provide coupled anatomical and electrical information of the skeletal muscles, enables reliable anatomical and electrical information correlation analysis and largely simplify the sensor integration for assessment of the human neuromusculoskeletal function.

Translucent wood fiber composites offer new functions to stiff composites. Most "eco-friendly" thermoset resins are only partially biobased. Poly(limonene acrylate), PLIMA, can be fully biobased and is combined with hot-pressed softwood fibers (WF) by liquid resin impregnation and curing. Fibers are random-in-plane or strongly oriented and have different lignin characteristics. Microstructure-mechanical property relationships are compared for hot-pressed WF networks and WF/PLIMA biocomposites from the same fibers. Stress transfer in WF/PLIMA biocomposites is enhanced with a modulus of up to 16.7 GPa and a tensile strength of up to 139 MPa, compared to transparent plastics like poly(methyl methacrylate) (modulus similar to 3 GPa, tensile strength similar to 70 MPa). Optical transmittance is high, even at 35 vol % fiber content, suggesting translucent panels or lighting applications. Eco-indicators show that the PLIMA matrix accounts for similar to 80% of biocomposite cumulative energy demand (CED, cradle to gate) of 60 MJ/kg, compared to similar to 120 MJ/kg for glass fiber/thermoset composites.

This study introduces a distributed electrified heating approach that is able to innovate chemical engineering involving endothermic reactions. It enables rapid and uniform heating of gaseous reactants, facilitating efficient conversion and high product selectivity at specific equilibrium. Demonstrated in catalyst-free CH4 pyrolysis, this approach achieves stable production of H2 (530 g h−1 L reactor−1) and carbon nanotube/fibers through 100% conversion of high-throughput CH4 at 1150 °C, surpassing the results obtained from many complex metal catalysts and high-temperature technologies. Additionally, in catalytic CH4 dry reforming, the distributed electrified heating using metallic monolith with unmodified Ni/MgO catalyst washcoat showcased excellent CH4 and CO2 conversion rates, and syngas production capacity. This innovative heating approach eliminates the need for elongated reactor tubes and external furnaces, promising an energy-concentrated and ultra-compact reactor design significantly smaller than traditional industrial systems, marking a significant advance towards more sustainable and efficient chemical engineering society.

Self-charging power systems (SCPSs) are envisioned as promising solutions for emerging electronics to mitigate the increasing global concern about battery waste. However, present SCPSs suffer from large form factors, unscalable fabrication, and material complexity. Herein, a type of highly stable, eco-friendly conductive inks based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are developed for direct ink writing of multiple components in the SCPSs, including electrodes for miniaturized spacer-free triboelectric nanogenerators (TENGs) and microsupercapacitors (MSCs), and interconnects. The principle of “one ink, multiple functions” enables to almost fully print the entire SCPSs on the same paper substrate in a monolithic manner without post-integration. The monolithic fabrication significantly improves the upscaling capability for manufacturing and reduces the form factor of the entire SCPSs (a small footprint area of ≈2 cm × 3 cm and thickness of ≈1 mm). After pressing/releasing the TENGs for ≈79000 cycles, the 3-cell series-connected MSC array can be charged to 1.6 V while the 6-cell array to 3.0 V. On-paper SCPSs are promising to serve as lightweight, thin, sustainable, and low-cost power supplies. 

Banana rachis is an abundant source of cellulose from agricultural waste. Fine-diameter cellulose nanofibrils (CNFs) should have a high capacity for heavy metal removal from wastewater based on a specific surface area. With nitro-oxidation and simple mechanical blending, the banana rachis resulted in individualized cellulose nanofibrils (NOCNFs) of length = 1231 nm, diameter = 5.26 nm, and negatively charged carboxylic groups at the C6 position with degrees of oxidation (DO) from 0.455 to 1.466 mmol/g. The NOCNFs were employed to remove Pb (II) from water and prepare films to investigate the mechanical performance. Increased Pb (II) removal efficiency was observed correlating to the increase in DO (0.455–1.466 mmol/g) and NOCNF concentration in support of a chemisorption mechanism. The NOCNFs showed a maximum adsorption capacity of 1667 mg/g at DO = 0.455 mmol/g, which is very high compared to adsorbents from literature and with the potential to increase at a DO of 1.466 mmol/g. NOCNF films showed impressive mechanical properties in support of high intrinsic NOCNF strength even at high DO: the tensile strength = 254 MPa, Young modulus = 10.7 GPa, and strain to failure = 5.7%. The nitro-oxidation also preserved the long-range cellulose order in the NOCNFs even at high DO with cellulose I crystalline index = 99.999%, essential to the remarkable Pb (II) removal capacity and mechanical performance. The study shows the potential of banana rachis from waste as a sustainable material for water purification and the possibilities of controlled banana rachis CNFs functionalization. Graphical abstract: (Figure presented.).

Nature has evolved elegant ways to alter the wood cell wall structure through carbohydrate-active enzymes, offering environmentally friendly solutions to tailor the microstructure of wood for high-performance materials. In this work, the cell wall structure of delignified wood is modified under mild reaction conditions using an oxidative enzyme, lytic polysaccharide monooxygenase (LPMO). LPMO oxidation results in nanofibrillation of cellulose microfibril bundles inside the wood cell wall, allowing densification of delignified wood under ambient conditions and low pressure into transparent anisotropic films. The enzymatic nanofibrillation facilitates microfibril fusion and enhances the adhesion between the adjacent wood fiber cells during densification process, thereby significantly improving the mechanical performance of the films in both longitudinal and transverse directions. These results improve the understanding of LPMO-induced microstructural changes in wood and offer an environmentally friendly alternative for harsh chemical treatments and energy-intensive densification processes thus representing a significant advance in sustainable production of high-performance wood-derived materials.

Recently, chitosan has become attractive due to being biodegradable, biocompatible and renewable. However, the weak mechanical properties of chitosan films limit their large-scale application. In this work, a strategy of blending TEMPO, oxidized CNF (TOCN) and chitosan was developed to fabricate nanocomposite films in order to improve the mechanical properties and maintain biocompatibility. The TOCN/chitosan nanocomposite films exhibited excellent optical transmittance (>85%) and extremely high tensile strength of 235 MPa. The good compatibility of TOCN and chitosan chains, good dispersion of chitosan aggregates and the presence of stiff TOCN crystal domains are the main reasons for getting improved mechanical strength of composite films. The films showed good biocompatible properties based on the cell activity assay results. Furthermore, they were stable in PBS buffer for more than 6 months without significant degradation. The TOCN/chitosan nanocomposite films with these excellent properties could be employed in medical applications.

The nature of mass transport in plants has recently inspired the development of low-cost and sustainable wood-based electronics. Herein, we report a wood electrochemical transistor (WECT) where all three electrodes are fully made of conductive wood (CW). The CW is prepared using a two-step strategy of wood delignification followed by wood amalgamation with a mixed electron-ion conducting polymer, poly(3,4-ethylenedioxythiophene)–polystyrene sulfonate (PEDOT:PSS). The modified wood has an electrical conductivity of up to 69 Sm−1 induced by the formation of PEDOT:PSS microstructures inside the wood 3D scaffold. CW is then used to fabricate the WECT, which is capable of modulating an electrical current in a porous and thick transistor channel (1 mm) with an on/off ratio of 50. The device shows a good response to gate voltage modulation and exhibits dynamic switching properties similar to those of an organic electrochemical transistor. This wood-based device and the proposed working principle demonstrate the possibility to incorporate active electronic functionality into the wood, suggesting different types of bio-based electronic devices.

Studtite and meta-studtite are the only two uranyl peroxides found in nature. Sparsely soluble studtite has been found in natural uranium deposits, on the surface of spent nuclear fuel in contact with water and on core material from major nuclear accidents such as Chernobyl. The formation of studtite on the surface of nuclear fuel can have an impact on the release of radionuclides to the biosphere. In this work, we have experimentally studied the formation of studtite as function of HCO₃- concentration and pH. The results show that studtite can form at pH = 10 in solutions without added HCO₃-. At pH <= 7, the precipitate was found to be mainly studtite, while at 8 = pH = 9.8, a mixture of studtite and meta-schoepite was found. Studtite formation from UO22+ and H₂O₂ was observed at [HCO3-] <= 2 mM and studtite was only found to dissolve at [HCO₃-] > 2 mM.