Carbon materials are widely investigated for electromagnetic (EM) shielding and absorption. However, designing sustainable and tunable architectures that span multiple EM functions remains challenging. Here, we present a renewable materials strategy based on biopolymer-derived carbon nanofiber sheets where both carbonization temperature and fiber alignment are used to tune EM attenuation. The sheets were fabricated via high-speed electrospinning followed by carbonization at 600–1000 °C, enabling systematic tuning of microstructure, anisotropy, porosity, electrical conductivity and dielectric response. The electrospinning process produced aligned nanofiber networks that upon carbonization developed into anisotropic conductive pathways. Carbonization at 1000 °C yielded highly porous sheets with a specific surface area of 926 m2g−1 without external activation. The temperature-driven structural evolution resulted in a distinct functional transition: dielectric transparency at 600 °C, broadband absorption at 700–800 °C, and highly conductive reflective-dominating shielding at 1000 °C. The optimized sheet achieved shielding effectiveness of 54 dB at 18.3  GHz and 44.5 dB at 1.0 THz. Electrical anisotropy further enabled orientation-dependent shielding differences of 16.4 dB (GHz) and 21.8 dB (THz). These results establish aligned, renewable carbon nanofiber sheets as scalable platforms for next generation microwave and terahertz technologies.

Hierarchically porous carbon aerogels offer significant potential for next-generation energy storage, yet controlling their structure and electrolyte infiltration remains a key challenge. Here, we develop fully biobased carbon aerogels (CAs) derived from a lignin-cellulose nanocrystal blend via ice-templating and carbonization. The resulting anisotropic hierarchical porous structures are infused with poly(vinyl alcohol)-potassium hydroxide gel polymer electrolyte to form semi-solid composite electrodes. Time-resolved synchrotron X-ray microtomography enables direct visualization of structural evolution during carbonization and three-dimensional electrolyte infiltration. Image-based pore-scale modeling performed directly on reconstructed synchrotron X-ray tomographic volumes reveals how the real hierarchical pore network governs gel electrolyte distribution, accessible porosity, and ion transport pathways. The results show that aligned and interconnected pore networks enable deep, uniform electrolyte penetration, reduce transport tortuosity, and increase electrochemically active volume. The structure-transport-performance relationship is validated by electrochemical testing of symmetric supercapacitors, demonstrating stable capacitance and reduced internal resistance. This work establishes a concept for renewable porous carbon electrodes and introduces a scalable CA-gel electrolyte system for high-performance solid-state energy storage.

Thin, high-performance separators are crucial for enhancing the volumetric energy density of electrochemical energy storage devices. Cellulose nanofibril networks are promising candidates due to their intrinsic hydrophilicity and ability to form thin, mechanically strong networks. In this study, wood particles were directly TEMPO-oxidized and fibrillated into nanofibrils (TOCNF) using a microfluidizer, and their resulting networks were tailored with kraft lignin via a simple mixing and casting approach. The influence of lignin content on separator properties and supercapacitor performance was systematically evaluated. The modified networks were compared with pristine TOCNF networks and commercial polyolefin separators. An optimal lignin content of 10 wt% provides the best balance of properties, combining high electrolyte uptake (∼280 wt%), good wet tensile strength (∼6 MPa), and sufficient thermal stability. Supercapacitors assembled with this separator delivered high specific capacitance (112.1 F g−1 at 0.5 A g−1), low series resistance (2.4 Ω), and stable, symmetric charge–discharge behavior. Increasing lignin content to 20 and 30 wt% led to reduced mechanical integrity and electrochemical performance. Overall, the bio-based separators outperformed the commercial reference, highlighting lignin-tailored TOCNF networks as sustainable and high-performance alternatives for next-generation energy storage applications.

Reconfigurable intelligent surfaces (RISs) are key enabling technologies for next-generation wireless telecommunication systems, offering dynamic control over electromagnetic (EM) wave propagation. However, most existing RIS demonstrations rely on conventional electronic or metallic platforms, raising concerns about resource availability, recyclability, and environmental sustainability. In this study, hybrid nanostructured RIS prototypes (Prototypes I–III) were designed and fabricated using sustainable, wood-derived materials, namely, cellulose nanofibers (CNFs), suberin, and biocarbon, in combination with thermoresponsive vanadium dioxide (VO₂) nanoparticles. The EM performance of these RIS architectures was first optimized through full-wave simulations and then validated experimentally by the cast-layer deposition of VO₂/CNF–suberin functional layers onto printed circuit board (PCB) substrates. Among the tested designs, Prototype I, comprising a functional layer of 95 wt % VO₂, 2.5 wt % nonderivatized CNF, and 2.5 wt % suberin, exhibited the most pronounced thermal response, showing resonance frequency shifts of up to 19 MHz at a 5 GHz center frequency and phase shifts of 83° with temperature variation. Prototype II, containing cationic CNFs, demonstrated improved mechanical stability but reduced electrical continuity due to microstructural cracking, whereas Prototype III, modified with biocarbon, displayed diminished conductivity arising from its lower VO₂ content. Degree of linear polarization (DOLP) analysis revealed early stage phase transitions that occurred prior to complete conductive pathway formation. Overall, the hybrid RIS architectures developed from VO₂ and wood-derived materials through a sustainable processing route exhibited highly tunable, temperature-triggered EM modulation, with sensitivity ranging from low to high, depending on the material composition and assembly configuration.

The realization of future holographic technologies, including extended reality, the Internet of Things, and autonomous transportation, enabled by next-generation telecommunications, demands sustainable, advanced components capable of operating at sub-terahertz (sub-THz) frequencies. Herein, fully bio-based Fresnel zone plate (FZP) lenses are fabricated as high-performance focusing elements for the sub-THz range using wood-derived cellulose nanofibers (CNFs) and biocarbon (BC) microparticles. The integration of mechanically robust, low dielectric loss CNF network with BC (0–50 wt.%) yields CNF–BC composite films exhibiting tunable thickness, electrical conductivity, and dielectric response, as well as stable structural integrity across a wide range of humidity and temperature conditions. At moderate BC loadings (5–10 wt.%), high tensile strength (>70 MPa) and enhanced ductility (>9%) are preserved, while controlled increases in permittivity and conductivity are achieved without compromising the low dielectric loss required for efficient sub-THz operation. Nested nine-ring FZP lenses constructed from laser-patterned CNF–BC integrated with ultralight CNF aerogel substrates deliver excellent focusing performance. Simulated and experimental results demonstrate high directivities exceeding 30 dBi at 0.3 THz, with gains comparable to or surpassing those of geometrically identical metallic lenses under low-gain waveguide excitation. The CNF–BC composites provide a scalable and sustainable platform for high-performance sub-THz electromagnetic applications.

This study investigates the use of X-ray microtomography (XMT) to reveal the structure of complex porous biological tissues and the fluid flow through them during wetting. It also evaluates fluid dynamical simulations based on XMT data to reproduce and analyse these flows, with a final aim of revealing fluid transport and void formation in such tissues. To fulfil the objectives, the wetting flow of a polymer liquid through an initially dry conditioned Norway spruce wood sample is visualised using XMT at the MAX IV synchrotron. The liquid flow front progression captured after 24 s and 48 s reveals uneven filling of longitudinal tracheids and flow between them via the tiny pits which connect tracheids. Most tracheids fill between 24 and 48 s, possibly due to removal of air inclusions. Large density gradients near cell walls suggest that the fluid followed and deposited along wall structures. Computational fluid dynamics simulations (CFD) of saturated flow through the tomography-based geometry indicate velocity profiles that resemble pipe flow in longitudinal tracheids and flow rate differences among them. The latter indicates that the geometry itself may cause the experimentally observed uneven flow. Streamlines show intra-tracheid flow development and clear flow direction change at the pits. Additionally, wetting simulations, using a constant contact angle, capture initial uneven filling between the tracheids on shorter time scales than could be capture by the experiments. These simulations furthermore show air entrapment during filling, consistent with experimental observations. Combining XMT with CFD enables detailed studies of flow in biological porous media. Faster X-ray scanning, incorporating dynamic contact angles and accounting for diffusion in simulations could further refine insights into fluid progression during capillary-driven flow into complex structures of porous biological tissues.