Cellulose has emerged as a promising sustainable material for advanced applications, including energy harvesting and sensing via triboelectric nanogenerators (TENGs). Despite significant progress in cellulosic TENGs, the role of carbonaceous nanomaterials with different morphologies and surface chemistries remains insufficiently understood. In this study, regenerated cellulose was used as a matrix to incorporate different carbon allotropes, including nanodiamonds, multi-walled carbon nanotubes (MWCNTs), and graphene nanoplatelets, to systematically evaluate their effect on triboelectric performance. Cellulose was dissolved in cold alkaline solution, and composites containing 2.5, 5, 7.5, 10, and 20 wt% of nanoparticles were prepared and tested as tribolayers against PTFE in a TENG configuration. The results showed that graphene-, MWCNT-, and nanodiamond-based composites improved power output by up to 76%, 51%, and 40%, respectively, compared to pure cellulose (34.3 W m−2). Physical and structural analyses, including dielectric spectroscopy, electrical conductivity measurements, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), FTIR, and Raman spectroscopy, were employed to investigate the structure-property relationships of regenerated cellulose‑carbon allotrope composites. The findings provide insight into the role of carbon nanomaterials in tuning the triboelectric behavior of regenerated cellulose and offer guidance for the design of high-performance, sustainable functional composites

Regenerated cellulose is a promising tribopositive material for sustainable triboelectric nanogenerators (TENGs), although its electrical output remains sensitive to surface and interfacial properties. In this study, regenerated cellulose was modified using atomic layer deposition (ALD) of Al2O3, TiO2, and ZnO to investigate how nanoscale oxide coatings influence triboelectric performance against a tribonegative PTFE counter layer. Two deposition regimes were examined: 7 ALD cycles, representing the early stage of ALD growth, and 200 cycles, representing a more developed coating regime. Triboelectric measurements, dielectric spectroscopy, structural characterization and contact angle analysis, were used to evaluate how ALD modification influences the electrical response of regenerated cellulose. All ALD-modified samples exhibited increased surface charge density and power output compared to unmodified cellulose, while also showing improved retention of triboelectric performance at elevated relative humidity. The 7-cycle samples consistently outperformed the corresponding 200-cycle coatings under low-humidity conditions, whereas the 200-cycle ZnO sample exhibited the highest humidity stability. No direct correlation between wettability and triboelectric output was observed. The results suggest that relatively small interfacial modifications introduced by ALD are sufficient to influence both the triboelectric response and humidity-dependent charge dissipation behavior of regenerated cellulose

Polymer-based organic mixed ion-electron conductors (OMIECs) are a class of materials offering unique coupled dual charge transport characteristics along with appealing properties including mechanical softness, biocompatibility, tunability, volumetric capacitance, and stability. These features have been exploited in devices including organic electrochemical transistors (OECTs), neuromorphic computing, energy storage, sensors, neural electrodes, and actuators. Conventionally, OMIEC polymers are prepared through chemical, vapor-phase, electrochemical, or enzymatic polymerization, typically relying on oxidants, metal catalysts, and/or organic solvents, significantly limiting their scalability, sustainability, and biocompatibility. Here, we introduce an initiator-free, visible-light-induced polymerization of water-soluble conducting polymer precursors, enabling facile formation of high-performance and inherently biocompatible OMIECs. This novel approach allows direct photopatterning and seamless film deposition and manufacturing of OECTs across rigid, flexible, and biological substrates, exemplified by glass, textiles, and mouse skin (in vivo). Through careful optimization of the photopolymerization process, resulting OMIECs possess state-of-the-art electrical, electrochemical, and device properties along with exceptional compatibility and conformability with various flexible and biological surfaces. Finally, we demonstrate the utility of these photopatterned electrodes, manufactured directly on mouse skin in vivo, where they significantly enhance the recording efficacy and signal-to-noise ratio of low-frequency brain activity in anesthetized mice

PEDOT:Tos is a promising conducting polymer for electronic and bioelectronic applications, yet its charge transport is affected by various factors and remains challenging to optimize. This study investigates the impact of solvent posttreatment on PEDOT:Tos thin films, exploring its influence on morphology and electrical conductivity. A combined experimental-theoretical approach is employed, integrating molecular dynamics, density functional theory, and transport calculations on one hand and conductivity, GIWAXS and XPS measurements on the other hand. Moreover, we developed a machine learning (ML) framework based on convolutional neural networks with the Coulomb matrix as the predictor, and transfer integrals for multiscale transport calculations as targets. Our results reveal that solvent-induced morphological changes strongly affect charge transport, with the ML model effectively reproducing observed conductivity. The developed ML model dramatically boosts the speed of mobility calculations, enabling the analysis of large-scale polymer films that were previously beyond computational reach

The electrified production of hydrogen peroxide (H2O2) by oxygen reduction reaction (ORR) is attractive to increase the sustainability of chemical industry. Here the same chains of intrinsically conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT) are utilized, as ORR electrocatalyst, while varying polymeric primary dopants (PSS and Nafion) and the level of secondary doping with DMSO. These changes modulate various properties of the film, such as its microscale organization and electronic conductivity. The aim here is to clearly decouple the rate of the heterogeneous electron transfer (HET) of ORR from the diffusion affected by electronic conductivity and the electrochemically available surface area. It is found that the rate of HET and the double layer capacitance are significantly affected by primary dopant. On the contrary, secondary doping shows very little effect on the rate of HET. However, such secondary doping resulted in the increase of both electrochemically available surface area and the diffusion through the polymer film. This effect is attributed to a few orders increase of the electronic conductivity in the film improving availability of the polymer for electron transfer. The enhancement of diffusion upon the secondary doping of conducting polymer is utilized to improve direct conversion of air into H2O2 on gas diffusion electrode. 

Stretchable circuits based on liquid metals are promising for wearables but the lack of scalable processes for sintering of printed liquid metal dispersions constitutes a challenge for large-area and high-volume manufacturing. In this work, materials and methods for fully screen printed stretchable liquid metal multilayer circuits have been developed. The ink is based on liquid metal droplets dispersed in the green solvent propylene glycol using the harmless dispersion agent polyvinylpyrrolidone. The development of a scalable water-spray sintering method in combination with ink optimization yielded highly conductive prints of ≈7.3 × 105S/m. Interestingly, the printed conductors experienced a resistance increase of less than 10% during 50% strain cycling, which is far below the expected 125% increase due to the geometry factor. The process allows for printing of high-performance multilayer circuits, which is demonstrated by the development of printed stretchable near-field communication tags. 

Energy storage devices, like redox-flow batteries and redox-supercapacitors, generate electrochemical potential by charging redox-active molecules. A key component in this class of devices is an ion-selective membrane that prevents redox-molecule crossover between half-cells, while allowing small ions to pass with minimal resistance. Conventional membranes often use ‘forever chemicals’ like Per-fluoroalkyl substances (PFAS), impacting their environmental footprint. This work introduces novel manufacturing methods for membranes made from coatings of cellulose nanofibril on kraft paper for use in these devices. The coating process is optimized to block redox-active molecules (e.g., alizarin red s and lignosulfonate) and enhance wet ionic conductivity. By refining the cellulose coating with chemical crosslinkers, leakage of redox molecules is reduced by an order of magnitude compared to uncoated kraft paper, without affecting conductivity. The goal is to pave the way for more environmentally friendly membranes in energy storage electrochemical cells. This innovation not only addresses environmental concerns but also the scalability of manufacturing, while maintaining the efficiency and functionality required for the envisioned applications.

Recent years have shown many advances in the development of tunable structural colors by combining nanostructures with electrochromic materials. One main goal is to develop energy saving color displays that rely on ambient light instead of being emissive. However, all displays need to be pixelated to show arbitrary images and few studies have addressed the challenge of preparing and controlling individual electrochromic pixels. Herein, a very simple method to reach this milestone by using passive matrix addressing is presented, which requires no additional electronic components in the pixels. It is shown that the common transparent conductor indium tin oxide (ITO) in non-aqueous electrolytes exhibits the diode-like behavior (threshold in voltage in relation to current and coloration) necessary to prevent significant cross-talk between pixels. The chemical nature of the redox activity that enables this behavior is attributed to omnipresent oxygen and the formation of superoxide ions. Additionally, it is shown that a gel-like electrolyte can be prepared by optical lithography, which makes the concept compatible with patterning of pixels at high resolution. This method for preparing pixelated displays should be compatible with practically any type of electrochromic surface in both reflective and transmissive configurations. Also, the counter electrode maintains excellent transparency since it simply consists of ITO. The results should prove very useful as the research field of tunable structural colors moves from proof-of-concept to real devices. © 2024 Wiley-VCH GmbH.

Stretchable electronics has received major attention in recent years due to the prospects of integrating electronics onto and into the human body. While many studies investigate how different conductive fillers perform in stretchable composites, the effect of different elastomers on composite performance, and the related fundamental understanding of what is causing the performance differences, is poorly understood. Here, we perform a systematic investigation of the elastomer influence on the electromechanical performance of gold nanowire-based stretchable conductors based on five chemically different elastomers of similar Young’s modulus. The choice of elastomer has a huge impact on the electromechanical performance of the conductors under cyclic strain, as some composites perform well, while others fail rapidly at 100% strain cycling. The lack of macroscopic crack formation in the failing composites indicates that the key aspect for good electromechanical performance is not homogeneous films on the macroscale but rather beneficial interactions on the nanoscale. Based on the comprehensive characterization, we propose a failure mechanism related to the mechanical properties of the elastomers. By improving our understanding of elastomer influence on the mechanisms of electrical failure, we can move toward rational material design, which could greatly benefit the field of stretchable electronics. 

Porous carbon materials are common materials used for sensor and absorbent applications. A novel approach for functionalizing porous carbons through the impregnation of porous carbon black with benzoxazine monomers, followed by thermal polymerization is introduced herein. The method not only establishes a new avenue for the functionalization of porous carbons but also endows the resulting material with both copper ion-binding and sensing properties. We showcase the versatility of the technique by illustrating that the polymerization of phenols with benzoxazine monomers serves as an extra tool to customize absorption- and sensing properties. Experimental validation involved testing the method on carbon black as a porous substrate, which was impregnated with both bisphenol-a benzoxazine and a combination of bisphenol-a benzoxazine and alizarin. The resulting materials were assessed for their dual functionality as both an absorbent and a sensor for copper ions by varied copper ion concentrations and exposure times. The dye absorption test demonstrated a notable capacity to accumulate copper ions from dilute solutions. Electrochemical characterization further confirmed the effectiveness of the modified carbons, as electrodes produced from inks were successful in detecting copper ions accumulated from 50 μM Cu2+ solutions. With this work, we aspire to set the steppingstone towards a facile functionalization of porous carbon materials towards water purification applications. © 2024 The Authors