Conductive Cellulose Research Articles

Multifunctional Highly Conductive Cellulose Nanopaper with Ordered PEDOT:PSS Alignment Enabled by External Surface Area-Promoted Phase Separation

Multifunctional Highly Conductive Cellulose Nanopaper with Ordered PEDOT:PSS Alignment Enabled by External Surface Area-Promoted Phase Separation

Mechanically robust and highly conductive bacterial cellulose hydrogels through synergy of directional freeze–thawing and salting-out for wearable sensors

It is urgent to develop high-performance conductive hydrogels that simultaneously exhibit high biocompatibility, mechanical robustness, exceptional conductivity and frost resistance to fulfil the requirements of wearable flexible sensors. Herein, we present a simple and integrated approach for designing iso/anisotropic bacterial cellulose (BC) hydrogels by immersing the as-prepared polyvinyl alcohol (PVA)–BC–Borax hydrogels in saturated NaCl solutions using a salting-out effect to assist the non–/directional freeze–thawing strategy. Benefitting from the synergistic strengthening of molecular interactions, including hydrogen, coordination, and boron ester bonds, as well as the enhanced PVA and BC crystallinity resulting from the salting-out effect, the tensile strength (0.8–3.2 MPa) and high ionic conductivity (61.5–136.2 mS/cm) of isotropic hydrogels (PVA–BC–Borax/NaCl) can be well tuned by adjusting the feeding mass fractions of PVA, borax and BC. The optimised hydrogel, PVA7.5%–BC0.45%–Borax0.375%/NaCl, demonstrated remarkable mechanical properties (3.2 MPa, 295.1 %), ionic conductivity (72.6 mS/cm) and good anti-freezing properties (–40.8 °C), maintaining excellent conductivity (61.8 mS/cm) even at –20 °C due to the introduction of NaCl. When subjected to directional freeze–thawing cycles, the D(Directional)-PVA7.5%–BC0.45%–Borax0.375%/NaCl hydrogel, with its organised layers and larger pore–sized structures, exhibited higher breaking elongation (609.2 %) and ionic conductivity (81.6 mS/cm) than its isotropic counterpart (295.1 %, 72.6 mS/cm). The D-PVA7.5%–BC0.45%–Borax0.375%/NaCl hydrogel was successfully used as a strain sensor for detecting a variety of human movements, showing excellent responsiveness to external stimuli, thereby demonstrating its potential applications in human–machine interaction, flexible sensing and bioelectronics.

Attapulgite-Reinforced Cellulose Hydrogels with High Conductivity and Antifreezing Property for Flexible Sensors.

Ionic conductive cellulose hydrogels are some of the most promising candidates for flexible sensors. However, it is difficult to simultaneously prepare cellulose hydrogels with high mechanical strength, good ionic conductivity, and antifreeze performance. In this work, a natural clay (attapulgite)-reinforced cellulose hydrogel was fabricated. Through a one-pot method, cellulose and attapulgite were dispersed in a concentrated ZnCl2 solution. The obtained hydrogel exhibited a dual network of hydrogen bonds and Zn2+-induced ionic interactions. Attapulgite serves as an inorganic filler that can regulate the hydrogen-bonding density among cellulose molecules and provides abundant channels for fast ion transport. By optimizing the attapulgite loading, a mechanically strong (compressive strength up to 1.10 MPa), tough (fracture energy up to 0.36 MJ m-3), highly ionic conductive (4.15 S m-1), and freezing-tolerant hydrogel was prepared. These hydrogels can be used for sensitive and stable human motion sensing, demonstrating their great potential for healthcare applications.

Machine learning powered CN-coordinated cobalt nanoparticles embedded cellulosic nanofibers to assess meat quality via clenbuterol monitoring

The World Anti-Doping Agency (WADA) has prohibited the use of clenbuterol (CLN) because it induces anabolic muscle growth while potentially causing adverse effects such as palpitations, anxiety, and muscle tremors. Thus, it is vital to assess meat quality because, athletes might have positive test for CLN even after consuming very low quantity of CLN contaminated meat. Numerous materials applied for CLN monitoring faced potential challenges like sluggish ion transport, non-uniform ion/molecule movement, and inadequate electrode surface binding. To overcome these shortcomings, herein we engineered bimetallic zeolitic imidazole framework (BM-ZIF) derived N-doped porous carbon embedded Co nanoparticles (CN-CoNPs), dispersed on conductive cellulose acetate-polyaniline (CP) electrospun nanofibers for sensitive electrochemical monitoring of CLN. Interestingly, the smartly designed CN-CoNPs wrapped CP (CN-CoNPs-CP) electrospun nanofibers offers rapid diffusion of CLN molecules to the sensing interface through amine and imine groups of CP, thus minimizing the inhomogeneous ion transportation and inadequate electrode surface binding. Additionally, to synchronize experiments, machine learning (ML) algorithms were applied to optimize, predict, and validate voltametric current responses. The ML-trained sensor demonstrated high selectivity, even amidst interfering substances, with notable sensitivity (4.7527 μA/μM/cm2), a broad linear range (0.002–8 μM), and a low limit of detection (1.14 nM). Furthermore, the electrode exhibited robust stability, retaining 98.07% of its initial current over a 12-h period. This ML-powered sensing approach was successfully employed to evaluate meat quality in terms of CLN level. To the best of our knowledge, this is the first study of using ML powered system for electrochemical sensing of CLN.

Preparation of Conductive Cellulose Coated with Conductive Polymer and Its Application in the Detection of pH and Characteristic Substances in Sweat.

Rich biological information in sweat provides great potential for health monitoring and management. However, due to the complexity of sweat, the development of environmentally friendly green electronic products is of great significance to the construction of ecological civilization. This study utilized a simple combination of polystyrene sulfonate sodium (PSS) and filter paper (FP) to prepare cellulose materials coated with conductive polymers, developing an electrochemical sensor based on the modified materials. The mechanical and electrochemical properties of the fabricated PSS/FP membrane were optimized by adjusting the feeding dosage of PSS. The realized PSS/FP composite containing 7% PSS displayed good conductivity (9.1 × 10-2 S/m), reducing electric resistance by 99.2% compared with the original FP membrane (6.7 × 10-4 S/m). The stable current of the membrane in simulated sweat under different pH environments is highly correlated with the pH values. Additionally, when the membrane is exposed to simulated sweat with varying ion concentrations, the current signal changes in real time with the concentration variations. The response time averages around 0.3 s.

Enhanced interfacial interaction of graphene nanoplatelets/cellulose nanofiber matrix driven by pyranine-based dispersant for efficient thermal managing materials

With the development of high-density electronics, polymer-based thermal conductive composites with excellent thermal and mechanical performance are receiving great attention. For the development of polymer-based thermal conductive composites with superior properties, it is essential to reduce the agglomeration of fillers and enhance the interfacial interactions between thermal conductive fillers and the polymer matrix. Among the several thermal conductive materials, graphene nanoplatelets (GNPs) and cellulose nanofiber (CNFs) are attracting attention. However, poor interfacial interaction between GNP and CNF leads to interfacial separation, which in turn, deteriorates its properties. Herein, we synthesized a pyranine-functionalized polyether dispersant (PyPE), which can significantly improve the interfacial interactions between GNPs and CNFs. The effect of PyPE on the dispersion behavior of GNPs and the thermomechanical properties of GNP-CNF composite were monitored. Furthermore, we also performed molecular dynamics (MD) simulations to investigate the impact of applying PyPE dispersant on the interfacial interactions between the GNPs and CNF matrix. The application of PyPE significantly enhanced the dispersibility of GNPs within the CNF matrix, resulting in a 15.5 % increase in-plane thermal diffusivity and a 24.5 % enhancement in tensile strength of the composite, demonstrating their potential applications in high power density electrical equipment and electronic devices.

Wet Spinning Fabrication of Robust and Uniform Intrinsically Conductive Cellulose Nanofibril/Silk Conductive Fibers as Bifunctional Strain/Humidity Sensor in Potential Smart Dressing

Wet Spinning Fabrication of Robust and Uniform Intrinsically Conductive Cellulose Nanofibril/Silk Conductive Fibers as Bifunctional Strain/Humidity Sensor in Potential Smart Dressing

Uniform and welded networks of silver nanowires surface-embedded on cellulose yarns with PEDOT:PSS passivation for sustainable E-textiles

Electronic textiles are critical for wearable electronics and real-time health care monitoring. The use of cellulose fibers with conductive components to construct optimized materials for enhanced performance remains an ongoing mission. We report the use of continuous dip-coating of hydrogel fibers to fabricate conductive cellulose yarns (CCYs). Uniform, interwelded and compact silver nanowire (AgNW) networks are embedded on the surfaces of the cellulose yarns, after which a PEDOT:PSS passivation layer is applied to ensure the reliability and practicality of the CCYs. This unique AgNW network provids high electrical conductivity of the CCYs, high strain sensitivities and good Joule heating. Wearable fabric devices embroidered with CCYs exhibit superior performance in strain sensing and electrothermal insulation. This CCY realizes the organic combination of manufacturing, practicability and functionality in sustainable E-textiles. The CCY has the potential to enable scalable manufacturing of low-cost wearable sensors integrated into everyday clothes.

Bioinspired Thermal Conductive Cellulose Nanofibers/Boron Nitride Coating Enabled by Co-Exfoliation and Interfacial Engineering.

Thermal conductive coating materials with combination of mechanical robustness, good adhesion and electrical insulation are in high demand in the electronics industry. However, very few progresses have been achieved in constructing a highly thermal conductive composites coating that can conformably coat on desired subjects for efficient thermal dissipation, due to their lack of materials design and structure control. Herein, we report a bioinspired thermal conductive coating material from cellulose nanofibers (CNFs), boron nitride (BN), and polydopamine (PDA) by mimicking the layered structure of nacre. Owing to the strong interfacial strength, mechanical robustness, and high thermal conductivity of CNFs, they do not only enhance the exfoliation and dispersion of BN nanoplates, but also bridge BN nanoplates to achieve superior thermal and mechanical performance. The resulting composites coating exhibits a high thermal conductivity of 13.8 W/(m·K) that surpasses most of the reported thermal conductive composites coating owing to the formation of an efficient thermal conductive pathway in the layered structure. Additionally, the coating material has good interface adhesion to conformably wrap around various substrates by scalable spray coating, combined with good mechanical robustness, sustainability, electrical insulation, low-cost, and easy processability, which makes our materials attractive for electronic packaging applications.

Photothermal, superhydrophobic, conductive, and anti-UV cotton fabric loaded with polydimethylsiloxane-encapsulated copper sulfide nanoflowers

Multifunctional textiles have attracted widespread attention with the improvement of awareness of health. Especially, the fluorine-free superhydrophobic and conductive cellulose fiber-based fabrics have received intensive interest due to their broad and high-value applications. Herein, the copper sulfide nanoflowers were in-situ deposited on cotton fabric followed by polydimethylsiloxane (PDMS) treatment for encapsulating CuS nanoflowers and obtaining superhydrophobicity, recorded as Cot@PTA@CuS@PDMS. Cot@PTA@CuS@PDMS possesses superhydrophobicity with contact angles of 153.0 ± 0.4°, photothermal effect, excellent UV resistance, good conductivity, and anti-fouling. Interestingly, the resistance of Cot@PTA@CuS@PDMS is significantly reduced from 856.4 to 393.1 Ω under simulated sunlight irradiation with 250 mW/cm2. Notably, the resistance can be slightly recovered after shutting off simulated sunlight. Besides, Cot@PTA@CuS@PDMS has efficient oil-water separation efficiency for corn germ oil and castor oil, respectively. Briefly, this work provides a novel, facile, and promising strategy to fabricate multifunctional fiber-based textiles with the reversible change of resistance under simulated sunlight irradiation, inspiring more scholars to control the resistance change of textiles by light irradiation.

Self-healing, environmentally stable and adhesive hydrogel sensor with conductive cellulose nanocrystals for motion monitoring and character recognition

Conductive hydrogel-based sensors offer diverse applications in artificial intelligence, wearable electronic devices and character recognition management. However, it remains a significant challenge to maintain their satisfactory performances under extreme climatic conditions. Herein, a stretchable, self-adhesive, self-healing and environmentally stable conductive hydrogel was developed through free radical polymerization of hydroxyethyl acrylate (HEA) and poly(ethylene glycol) methacrylate (PEG) as the skeleton, followed by the incorporation of polyaniline-coated cellulose nanocrystal (CNC@PANI) as the conductive and reinforced nanofiller. Encouragingly, the as-prepared hydrogel (CHP) exhibited decent mechanical strength, satisfactory self-adhesion, prominent self-healing property (95.04 % after 60 s), excellent anti-freezing performance (below −60 °C) and outstanding moisture retention. The assembled sensor derived from CHP hydrogel possessed a low detection limit (0.5 % strain), high strain sensitivity (GF = 1.68) and fast response time (96 ms). Remarkably, even in harsh environmental temperatures from −60 °C to 80 °C, it reliably detected subtle and large-scale human motion for a long-term process (>10,000 cycles), manifesting its exceptional environmental tolerance. More interestingly, this hydrogel-based sensor could be assembled into a “writing board” for accurate handwritten numeral recognition. Therefore, the as-obtained multifunctional hydrogel could be a promising material applied in human motion detection and character recognition platforms even in harsh surroundings.

Washable and anti-impact conductive cellulose yarn-based energy meta-textile against harsh environments

Flexible fiber-based zinc-ion batteries are highly regarded as potential for wearable electronic devices due to their high theoretical capacity and low redox potential. However, currently reported energy storage devices have limited practicality due to their inability to operate underwater or withstand mechanical stress. In this study, we present a multifunctional flexible fiber-based zinc-ion battery with exceptional durability, exhibiting high hammering resistance (maintaining 89.66 % capacity after 30 hammering cycles) and washing resistance (maintaining 77.97 % capacity after 30 min of washing). Moreover, the battery shows promising electrochemical performance, with a specific capacity 43.53 mAh g–1 and an energy density of 51.94 mWh g–1. Assembling and weaving multiple batteries into an energy meta-textile allows for normal mobile phone charging underwater and stable charge retention during mechanical stress, demonstrating potential for application in harsh environments.

High-sensitivity piezoresistive sensors based on cellulose handsheets using origami-inspired corrugated structures

Cellulose-based composites have attracted significant attention in the fabrication and advancement of wearable devices due to their sustainable, degradable, and cost-effective properties. However, achieving a cellulosic sensor with reliable sensory feedback remains challenging owing to the deficiency in reversible microstructures during response processes. In this study, we developed a piezoresistive sensor consisting of nearly pure cellulose handsheets using origami-inspired corrugated structures to achieve durable and sensitive piezoresistive responses. Multi-walled carbon nanotubes (MWCNTs) were used as conducting agents. With the addition of 7 wt% MWCNTs, 36.27 % of the cellulose fiber surface was covered and the conductivity of cellulose handsheets was increased to 8.7 S/m. The obtained conductive cellulose handsheets were transformed into corrugated structures and integrated orthogonally to construct the piezoresistive sensors with reversible electrical paths for electrons. The restorable corrugated structure endowed the sensors with a wide workable pressure range (0–10 kPa), high sensitivity (6.09 kPa−1 in a range of 0–0.92 kPa), fast response time (<280 ms), and good durability (>1000 cycles). Furthermore, the practical applications of the proposed sensors as wearable devices were demonstrated through phonation, real-time sports monitoring, and step pressure tests.

Conductive and Robust Cellulose Hydrogel Generated by Liquid Metal for Biomedical Applications

Conductive and Robust Cellulose Hydrogel Generated by Liquid Metal for Biomedical Applications

Application of cathodic protection method on steel structures using sacrificial anode and sodium polyacrylate-sodium carboxymethyl cellulose (PANa–CMC) hydrogel electrolyte

An ionically conductive sodium polyacrylate-sodium carboxymethyl cellulose (PANa–CMC) hydrogel electrolyte was developed for the sacrificial anode cathodic protection (SACP) of carbon steel in high-humidity environments. The incorporation of varying ratios of CMC into hydrogel formulation enhanced the water retention capacity, adhesion strength, and electrochemical performance, making it suitable for SACP applications. Particularly, PANa-5% CMC hydrogels demonstrated a current density of approximately 3 μA/cm², inhibited passive corrosion product formation, and sequestered metal ions from anodes, thus minimizing contamination. These findings highlight the substantial potential of PANa–CMC hydrogels as electrolytes, expanding the application of the SACP method to atmospheric environments.

Nucleation and property enhancement mechanism of robust and high-barrier PLA/CNFene composites with multi-level reinforcement structure

The demand for biopolymer-based green packaging has attracted growing attention because of its outstanding properties and consistency with clean environmental principle, unfortunately, its slow crystallization rate and narrow processing window are challenging. Inspired by combined functions in nanocellulose-based conductive hybrids, this work developed high-performance polylactic acid (PLA) composites using conductive cellulose nanofiber (CNFene). Interestingly, CNFene has multiple functions as highly graphitized carbon and abundant hydroxyl groups, delivering stimulating properties to PLA composites. As nucleating agents, 3 wt% CNFene has a carbon layer on the surface combined with a hydrogen bonding network synergistically enhancing the tensile and crystallization properties of PLA-C3, with a tensile strength of ∼ 53.7 MPa, crystallinity of ∼ 33.9 %, and 6.6 °C decrease in the cold crystallization temperature. Additionally, the compatibility between CNFene and PLA can form a multi-level “reinforcement” network structure, further improving thermal stability and barrier properties. The resultant PLA-C3 showed higher thermal decomposition onset temperature (T0), wider melt-processing window (197.6 °C) and extremely lower overall migration levels in ethanol (68.6 μg/kg) and isooctane (16.3 μg/kg), due to that improved interaction between CNFene and PLA positively affects crystallization ability and kinetic/mechanism of PLA to meet the requirements of industrial and green biopackaging applications.

Nano GeSe2/C anchored in carbon sponge skeleton for free-standing flexible lithium-ion battery electrodes

As a typical conversion alloyed anode material, Germanium selenide (GeSe2) exhibits isotropic lithiation behavior and high theoretical charge-discharge specific capacity. However, pure GeSe2 anode faces significant volume expansion (∼250 %−360 %) and further exploration is needed in the preparation of flexible electrode materials and structural design. Herein, a simple strategy is designed to load GeSe2/C-2 nanoparticles with porous carbon-coated structure on a flexible cross-networking substrate. The 3D network substrate is composed of highly conductive carbon nanotubes and adhesive cotton cellulose fibers. A two-step method involving coating and cross-linking is designed to achieve the fabrication of self-supporting flexible electrodes. As an anode for LIBs, the one layer GeSe2 discs with ∼0.65 mm thickness manifest capacities of 827.1, 744.4, 676.3, and 472.9 mAh g−1 at 0.1, 0.2, 0.5, and 1 A g−1, respectively. This superior Li+ storage performance can be attributed to the positive collective impact from the integration of nano-scale material, low crystalline properties, and carbon sponge skeleton. Furthermore, the GITT tests indicate that the diffusion coefficient of Li+ in the GeSe2-based electrodes ranged from 10−15 to 10−12 cm2/s, and the thickness of the flexible electrode (including two layers) has a negligible impact on its electrochemical performance.

Tough conductive cellulose organohydrogels with antifreezing capability, strain-sensitivity and for multi-functional sensors

The mechanical strength of traditional hydrogels is weak, and it is easy to freeze and harden below zero to lose the characteristics and conductivity of hydrogels, which seriously limits the application of hydrogels in sensors. To solve this problem, an organic hydrogel was prepared using a simple method. After testing, this organic hydrogel not only has good frost resistance but also has excellent mechanical properties. Cellulose-based hydrogels have received increasing attention as good materials for preparing flexible, wearable sensors due to their good biocompatibility, flexibility, and excellent mechanical strength. We polymerized 4-carboxy benzaldehyde (FBA) and polyvinyl alcohol (PVA) into gels under acid-catalyzed conditions, imparted freeze resistance to the hydrogels by introducing dimethyl sulfoxide (DMSO) into the hydrogels, and added water-soluble cellulose acetate (WSCA) to the hydrogels to enhance the mechanical properties of the hydrogels. The organic hydrogel prepared by this method is more stable than conventional hydrogel in low-temperature environments, even below − 80゜C can still maintain the soft state and good mechanical flexibility of the hydrogel, of which WSCA can enhance the mechanical properties, and the stress of the hydrogel can reach 0.85 MPa when the WSCA content is 2%, which is 2.5 times that of the hydrogel without WSCA. In addition, the prepared hydrogel also has good electrochemical performance, under the condition of − 80゜C, connected to the circuit, the small bulb can still maintain a weak brightness. Moreover, the sensor composed of hydrogels can distinguish vigorous movement and weak movement of the human body, which provides a new idea for the application of hydrogels on the sensor.

Constructing triple-network cellulose nanofiber hydrogels with excellent strength, toughness and conductivity for real-time monitoring of human movements

In recent years, there has been a lot of interest in developing composite hydrogels with superior mechanical and conductive properties. In this study, triple-network (TN) cellulose nanofiber hydrogels were prepared by using cellulose nanofiber as the first network, isotropic poly(acrylamide-co-acrylic acid) as the second network, and polyvinyl alcohol as the third network via a cyclic freezing-thawing process. The strong (9.43 ± 0.14 MPa tensile strength, (445.5 ± 7.0)% elongation-at-break), tough (15.12 ± 0.14 MJ/m3 toughness), and conductive (0.0297 ± 0.00021 S/cm ionic conductivity) TN cellulose nanofiber hydrogels were effectively created after being pre-stretched in an external force field, cross-linked by Fe3+ and added Li+. The produced composite TN cellulose nanofiber hydrogels were successfully used as a flexible sensor for real-time monitoring and detecting human movements, highlighting their potential for wearable electronics, medical technology, and human-machine interaction. Chemical compounds studied in this articleAcrylamide (PubChem CID: 6579); Acrylic acid (PubChem CID: 6581); Ammonium persulfate (PubChem CID: 6579); N, N′-methylene bisacrylamide (PubChem CID: 17956053); Sodium bromide (PubChem CID: 253881); Sodium hydroxide (PubChem CID: 14798); Sodium hypochlorite (PubChem CID: 23665760); Sodium chlorite (PubChem CID: 23668197); 2,2,6,6-tetramethylpiperidinyl-1-oxide (PubChem CID: 2724126); Polyvinyl alcohol (PubChem CID: 11199); Lithium chloride (PubChem CID: 433294); Iron nitrate nonahydrate (PubChem CID: 129774236)

Wood-inspired elastic and conductive cellulose aerogel with anisotropic tubular and multilayered structure for wearable pressure sensors and supercapacitors

Cellulose nanofiber (CNF) aerogels hold considerable potential in wearable devices as pressure sensors and flexible electrochemical energy storage. However, the undirectional assembly of CNFs results in poor mechanical performance, which limits their application in structural engineering. In this study, we propose an anisotropic aerogel with both elastic and conductive properties inspired by the micro-nanostructure of natural wood. One-dimensional TEMPO cellulose nanofibers (TOCNF) were utilized as structural building blocks, while two-dimensional reduced graphene oxide (rGO) served as the electron transfer platform, owing to their high mechanical strength. The directionally aligned tubular structure composed of multilayered sheets was formed through rapid unidirectional freezing and subsequent steam heating reduction. These structures efficiently transferred stress throughout the porous skeleton, resulting in TOCNF-rGO aerogels with high compressibility and excellent fatigue resistance (2000 cycles at 60 % strain). The aerogel also exhibited high sensitivity, wide detection range, relatively fast response, and excellent compression cycle stability, making it suitable for accurately detecting various human biological and motion signals. Additionally, TOCNF-rGO can be assembled into a flexible all-solid-state symmetric supercapacitor that delivers excellent electrochemical performance. It is expected that this biomass-derived aerogel will be a versatile material for flexible electronic devices for energy conversion and storage.