Polyaniline Hydrogel Research Articles

Sodium alginate supramolecular nanofibers in synergy with surface crack engineering to prepare tough and highly sensitive hydrogels

Soft and wet hydrogels often struggle to achieve both toughness and high sensitivity simultaneously, limiting their usefulness in flexible devices. To tackle this challenge, we devised a strategy that combines supramolecular sodium alginate nanofibers, utilizing Zr4+ as physical crosslinkers, with surface crack engineering via the micro-phase separation of polyaniline, to create a physically and chemically dual crosslinked polyacrylamide (PAM)/sodium alginate (SA)/polyaniline (PANI) hydrogel with exceptional toughness and high sensitivity. Owing to the supramolecular sodium alginate nanofibers, the dual crosslinked hydrogel exhibited a tensile strength of 0.391 MPa, an elongation at break of 568.9 %, and a toughness of 1.020 MJ/m3. The in-situ polymerized polyaniline layer, confined within the dense network, introduced micro-cracks onto the hydrogel surface, resulting in a high gauge factor of 11.4 for the fabricated hydrogel. Furthermore, integrating this hydrogel into a triboelectric nanogenerator transformed it into self-powered sensors capable of detecting external forces and generating various signals without power supply. These findings suggest that the developed hydrogel held great potential in diverse fields, including human motion detection, human-machine interaction, and wearable electronic devices.

A robust polyaniline hydrogel electrode enables superior rate capability at ultrahigh mass loadings

Simultaneously achieving high mass loading and superior rate capability in electrodes is challenging due to their often mutually constrained nature, especially for pseudocapacitors for high-power density applications. Here, we report a robust porous polyaniline hydrogel (PPH) prepared using a facile ice-templated in situ polymerization approach. Owing to the conductive, robust, and porous nanostructures suitable for ultrafast electron and ion transport, the self-supporting pure polyaniline hydrogel electrode exhibits superior areal capacitance without sacrificing rate capability and gravimetric capacitance at an ultrahigh mass loading and notable current density. It achieves a high areal capacitance (15.2 F·cm−2 at 500 mA·cm−2) and excellent rate capability (~92.7% retention from 20 to 500 mA·cm−2) with an ultrahigh mass loading of 43.2 mg cm−2. Our polyaniline hydrogel highlights the potential of designing porous nanostructures to boost the performance of electrode materials and inspires the development of other ultrafast pseudocapacitive electrodes with ultrahigh loadings and fast charge/discharge capabilities.

Conductive chitosan/polyaniline hydrogel: A gas sensor for room-temperature electrochemical hydrogen sensing

Hydrogen (H2) has been deemed a source of energy for both stationary and mobile applications to contribute to lowering carbon emissions due to its abundance (which can be extracted from various compounds), environmental friendliness, and high energy density. However, H2 gas is highly flammable and has a fast burning rate. Consequently, the need to ensure human safety and environmental preservation necessitates the development of hydrogen sensors that exhibit heightened sensitivity, a reduced detection threshold, and quick response times. Herein, we present the synthesis of a ternary hydrogel composite, chitosan-crosslinked poly(acrylic acid)-based polyaniline hydrogel (Cs-cl-pAA/PANI), which was developed to function as a cathode material in hydrogen sensing applications. The structural and optical properties of ternary cathode materials were evaluated using various analytical techniques, and hydrogen sensing was studied using electrochemical techniques. The electrochemical sensing characteristics of the hydrogel matrix were improved by including polyaniline (PANI) as a result of the overlapping of localised π-electrons in the p-orbitals. The sensitivity of the Cs-cl-pAA/PANI hydrogel was determined to be 48.7845 μA M, with a reaction time of 0.6s, recovery time of 2s, and detection limit of 3.682 μM. The sensor also exhibited outstanding restoration and repeatability.

Manipulation of Conducting Polymer Hydrogels with Different Shapes and Related Multifunctionality.

Maneuver of conducting polymers (CPs) into lightweight hydrogels can improve their functional performances in energy devices, chemical sensing, pollutant removal, drug delivery, etc. Current approaches for the manipulation of CP hydrogels are limited, and they are mostly accompanied by harsh conditions, tedious processing, compositing with other constituents, or using unusual chemicals. Herein, a two-step route is introduced for the controllable fabrication of CP hydrogels in ambient conditions, where gelation of the shape-anisotropic nano-oxidants followed by in-situ oxidative polymerization leads to the formation of polyaniline (PANI) and polypyrrole hydrogels. The method is readily coupled with different approaches for materials processing of PANI hydrogels into varied shapes, including spherical beads, continuous wires, patterned films, and free-standing objects. In comparison with their bulky counterparts, lightweight PANI items exhibit improved properties when those with specific shapes are used as electrodes for supercapacitors, gas sensors, or dye adsorbents. The current study therefore provides a general and controllable approach for the implementation of CP into hydrogels of varied external shapes, which can pave the way for the integration of lightweight CP structures with emerging functional devices.

Enhanced heterogeneous interface to construct intelligent conductive hydrogel gas sensor for individualized treatment of infected wounds

In this study, we developed an enhanced heterogeneous interface intelligent conductive hydrogel NH3 sensor for individualized treatment of infected wounds. The sensor achieved monitoring, self-diagnosis, and adaptive gear adjustment functions. The PPY@PDA/PANI(3/6) sensor had a minimum NH3 detection concentration of 50 ppb and a response value of 2.94 %. It also had a theoretical detection limit of 49 ppt for infected wound gas. The sensor exhibited a fast response time of 23.2 s and a recovery time of 42.9 s. Tobramycin (TOB) was encapsulated in a self-healing QCS/OD hydrogel formed by quaternized chitosan (QCS) and oxidized dextran (OD), followed by the addition of polydopamine-coated polypyrrole nanowires (PPY@PDA) and polyaniline (PANI) to prepare electrically conductive drug-loaded PPY@PDA/PANI hydrogels. The drug-loaded PPY@PDA/PANI hydrogel was combined with a PANI/PVDF membrane to form an enhanced heterogeneous interfacial PPY@PDA/PANI/PVDF-based sensor, which could adaptively learn the individual wound ammonia response and adjust the speed of drug release from the PPY@PDA/PANI hydrogel with electrical stimulation. Drug release and animal studies demonstrated the efficacy of the PPY@PDA/PANI hydrogel in inhibiting infection and accelerating wound healing. In conclusion, the gas-sensitive conductive hydrogel sensing system is expected to enable intelligent drug delivery and provide personalized treatment for complex wound management.

Tragacanth gum grafted polyaniline hydrogel as a biodegradable adsorbent for the removal of uranyl ions from water samples

Tragacanth gum grafted polyaniline hydrogel as a biodegradable adsorbent for the removal of uranyl ions from water samples

Mixed Ionic-Electronic Conducting Hydrogels with Carboxylated Carbon Nanotubes for High Performance Wearable Thermoelectric Harvesters.

Mixed ionic-electronic conducting (MIEC) thermoelectric (TE) materials offer higher ionic conductivity and ionic Seebeck coefficient compared to those of purely ionic-conducting TE materials. These characteristics make them suitable for direct use in thermoelectric generators (TEGs) as the charge carriers can be effectively transported from one electrode to the other via the external circuit. In the present study, MIEC hydrogels are fabricated via the chemical cross-linking of polyacrylamide (PAAM) and polydopamine (PDA) to form a double network. In addition, electrically conducting carboxylated carbon nanotubes (CNT-COOH) are dispersed evenly within the hydrogel via sonication and interaction with the PDA. Moreover, the electrical properties of the hydrogel are further improved via the in situ polymerization of polyaniline (PANI). The presence of CNT-COOH facilitates the ionic conductivity and enhances the ionic Seebeck coefficient via ionic-electronic interactions between sodium ions and carboxyl groups on CNT-COOH, which can be observed in X-ray photoelectron spectroscopy results, thereby promoting the charge transport properties. As a result, the optimum device exhibits a remarkable ionic conductivity of 175.3 mS cm-1 and a high ionic Seebeck coefficient of 18.6 mV K-1, giving an ionic power factor (PFi) of 6.06 mW m-1 K-2 with a correspondingly impressive ionic figure of merit (ZTi) of 2.65. These values represent significant achievements within the field of gel-state organic TE materials. Finally, a wearable module is fabricated by embedding the PAAM/PDA/CNT-COOH/PANI hydrogel into a poly(dimethylsiloxane) mold. This configuration yields a high power density of 171.4 mW m-2, thus highlighting the considerable potential for manufacturing TEGs for wearable devices capable of harnessing waste heat.

Core-alloyed shell structured Fe@FeCo di-atomic nanoclusters loaded in carbon aerogels as efficient bi-functional catalysts towards ORR and HER

In this work, core-alloyed shell structured (CAS) Fe@FeCo di-atomic nanoclusters loaded in carbon aerogels (CAS Fe@FeCo DA-NC/C catalysts) were successfully prepared by utilizing the spatial confinement effect of polyaniline (PANI) hydrogels led by strong chelation among Fe3+ ions, tannic acid (TA), and amino (or imino) groups of PANI polymer chains. The spatial confinement effect can guarantee the formation of CAS Fe@FeCo DA-NCs with sizes between 1.4 and 2.4 nm. Moreover, N4–Fe–O–Co–N4 units are composed of the alloyed shells of the CAS Fe@FeCo DA-NCs, which can act as bi-functional active sites. In addition, N4–Fe–O–Fe–N4 units are the main component of their cores (like Fe-SA-NCs), which would slightly help strengthen the adsorption ability of bi-functional active sites of the CAS Fe@FeCo DA-NCs to the reactants. The core-alloyed shell structure of the CAS Fe@FeCo DA-NCs are demonstrated by results of X-ray photoelectron spectra, X-ray absorption spectroscopy and control experiments. Thus, the CAS Fe@FeCo DA-NC is proposed as a new type of active species with bi-functional active sites for the first time, to the best of our knowledge. Thanks to their unique features as active species (proper size, core-alloyed shell structure, and bi-functional active sites), the as-prepared CAS Fe@FeCo DA-NC/C catalysts show excellent performance as bi-functional catalysts in the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.895 V (ΔE1/2 = 34 mV vs of Pt/C) in alkaline media and the hydrogen evolution reaction (HER, 133 mV @ 10 mA cm−2) in acidic media.

Development of Conducting Biopolymer-Based Biosensor for Heavy-Metal Ion Detection

The increasing concentration of heavy metals in the water ecosystems has been a noteworthy concern nowadays. This has accounted for various diseases, due to the bioaccumulation in the human body. We propose a biocompatible, non-toxic technique for the identification of heavy metal ions from the contaminated aquatic samples. A urease biosensor, having interpenetrating network of Katira-cl-Acrylic Acid (AAc)/Polyaniline (PANI) hydrogel composite deposited onto the indium tin oxide (ITO). Enhanced hydrogel conductivity due to the incorporation of PANI has been gained by the interfacial polymerization of katira gum and aniline monomer in the ratio of 2:1 using N,N′-MBA and APS as cross-linker and initiator respectively. Structural, morphological and electrochemical characterization of PANI/ITO, Katira-cl-AAc/PANI/ITO and Urease/Katira-cl-AAc/PANI/ITO electrode conducted using SEM, FT-IR, TGA, UV spectrometry, cyclic voltammetry. A comparative study of different concentrations of cadmium, cobalt and Mercury, has been done. The inhibition rates were found to be in the order of Hg2+ > Cd2+ > Co2+. Enzyme inhibition observed in the concentration range from 1.8 mM to 5 mM, 0.1 mM to 2 mM and 0.1 mM to 5 mM respectively. Urease/Katira-cl-AAc/PANI/ITO, exhibits greater stability, enhanced sensitivity and wide-range of detection limit (200 to 270 ng l−1) with a shelf life.

Solvent triggering assembly of self-supported MXene hydrogel for high performance asymmetric supercapacitors

Constructing 3D porous structure of MXene (Ti3C2Tx) is an efficient approach to prevent nanosheets restacking and realize prominent electrochemical functionality. However, the assembly of self-supported 3D Ti3C2Tx architecture is difficult due to the inherent rigidity and superior hydrophilicity of Ti3C2Tx nanosheets. Herein, a solvent-triggering gelation strategy is developed using polar aprotic N,N-Dimethylformamide and polar protic H2O as co-solvent to enhance hydrogen bonding and Ti-O-Ti covalent bonding between Ti3C2Tx nanosheets. Thereby, self-supported Ti3C2Tx hydrogel (MH12/5:5) in absence of any crosslinkers or substrates has been successfully fabricated. The MH12/5:5 hydrogel exhibits excellent specific capacitance of 384.4 F g1 and superb rate capability of 61 % in a broad current density range of 1–100 A g−1. Asymmetric supercapacitor has been assembled using MH12/5:5 hydrogel as negative electrode and a polyaniline hydrogel as positive electrode, which presents high energy density of 21.2 Wh kg−1. This solvent-triggering gelation strategy points toward a promising direction to develop self-supported MXene hydrogels for high performance energy storage devices.

Natural Phytic Acid-Assisted Polyaniline/Poly(vinyl alcohol) Hydrogel Showing Self-Reinforcing Features.

Polyaniline (PANi) hydrogels that combine advantages of hydrogels and conductive PANi have recently emerged in areas of wearable devices and personal healthcare. Nevertheless, their mechanical performance often gradually degrades after being used for a period, caused by destruction of the inner structures when external forces are applied. Inspired by biological structures with persistent durability, we develop here a phytic acid-assisted PANi/poly(vinyl alcohol) (PVA) hydrogel that shows self-reinforcing features. As a natural product holding plenty of phosphate groups, phytic acid (PA) plays two crucial roles when preparing this hydrogel: (1) aniline is salinized by PA in aqueous solution to promote in situ polymerization, making the resulting PANi conductive; (2) PA/PANi particles form hydrogen bonds with PVA, acting as stress concentration points to induce structure orientation. The optimal PVA/PA/PANi hydrogel displays dark green color with a uniform distribution of PA/PANi particles. After experiencing repetitive 4 × 100 stretching at a strain of 10%, the hydrogel exhibits an enhanced fracture strength (20.35 MPa), Young's modulus (22.66 MPa), and toughness (36.24 MJ·m-3) compared with the original hydrogel. This self-reinforcing feature is mainly attributed to the formation of anisotropic structures fixed by hydrogen bonds between PA/PANi particles and PVA chains upon repetitive external forces. Moreover, anisotropic structures can be disassembled by swelling the post-stretched hydrogel in water, and the swollen hydrogel shows similar self-reinforcing behaviors. The good mechanical durability and reusable characteristics make the PVA/PA/PANi hydrogel a reliable strain sensor. This work provides a structural growing-reviving approach for conductive hydrogels with persistent durability.

Electrochemiluminescent determination of sphingomyelin in milk based on polyaniline hydrogel coupled with enzyme-functionalized Au nanoparticles

In this paper, sphingomyelin (SM) is detected by a polyaniline hydrogel and Au nanoparticles with enzyme modified electrode (GCE/PAniH/AuNPs@enzyme). After a battery of enzymic degradation, SM can generate H2O2 and enhance the electrochemiluminescence (ECL) response of luminol, which endows the sensor with good sensitivity, specifiity and repeatability. Additionally, the proposed ECL biosensor displays good analytical performances with a wide range from 10.0 μg·mL−1 to 250.0 μg·mL−1 as well as a low detection limit of 3.50 μg·mL−1 (S/N = 3). When the ECL biosensor is used in the detection of SM in milk samples, satisfactory results are obtained, indicating that PAniH/AuNPs@enzyme will serve as a promising ECL material in the applications of H2O2-related bioassay in the future.

A Hybrid Stainless-Steel SPME Microneedle Electrode Sensor for Dual Electrochemical and GC-MS Analysis.

A mechanically robust in-tube stainless steel microneedle solid phase microextraction (SPME) platform for dual electrochemical and chromatographic detection has been demonstrated. The SPME microneedle was fabricated by layer-by-layer (LbL) in-tube coating, consisting of carbon nanotube (CNT)/cellulose nanocrystal (CNC) film layered with an electrically conductive polyaniline (PANI) hydrogel layer (PANI@CNT/CNC SPME microneedle (MN)). The PANI@CNT/CNC SPME MN showed effective analysis of caffeine by GC-MS with an LOD of 26 mg/L and excellent precision across the dynamic range. Additionally, the PANI@CNT/CNC SPME MN demonstrated a 67% increase in sensitivity compared to a commercial SPME fiber, while being highly robust for repeated use without loss in performance. For electrochemical detection, the PANI@CNT/CNC SPME MN showed excellent performance for the detection of 3-caffeoylquinic acid (3-CQA). The dynamic range and limits of detection (LOD) for 3-CQA analysis were 75-448 mg/L and 11 mg/L, respectively. The PANI@CNT/CNC SPME MN was demonstrated to accurately determine the caffeine content and 3-CQA in tea samples and dark roast coffee, respectively. The PANI@CNT/CNC SPME MN was used for semiquantitative antioxidant determination and composition analysis in kiwi fruit using electrochemistry and SPME-coupled GC-MS, respectively.

Prestretching‐Enhanced Conductive Hydrogel Electrode for Supercapacitors with High Areal Capacitance and Excellent Stretching Stability

The challenge to prepare conductive hydrogel electrodes for stretchable supercapacitors with high areal capacitance and excellent stability during stretching has attracted tremendous attention from researchers. Herein, a method to enhance the performance of a conductive hydrogel electrode is reported. The in situ oxidative polymerization of aniline monomer is performed in the prestretched polyacrylamide (PAAm) hydrogel. After releasing the hydrogel, the polyaniline (PANI) nanoparticles can shrink with the PAAm substrate to form a dense and continuous conductive network. Due to the enhanced conductive networks, the prestretched PAAm‐PANI conductive hydrogel with prestrain of 500% (PPCH5) electrode shows high areal capacitance of 509.9 mF cm−2 at 0.5 mA cm−2. The symmetrical stretchable supercapacitor based on PPCH5 electrodes exhibits a high areal capacitance of 219.7 mF cm−2. The device shows high capacitance retention of 68.5% even when stretched to 200% strain and noncapacitance decays after 2000 stretching cycles at 100% strain. This strategy can be expanded to the carbon nanotubes (CNT)‐filled hydrogel systems. The PAAm‐PANI‐CNT conductive hydrogel with prestrain of 500%‐based supercapacitor shows specific capacitance of 1429.87 mF cm−2. The results demonstrate that prestretching is a highly effective method to enhance capacitance and stretching stability of PANI hydrogel electrode for stretchable supercapacitors.

Application of poly (dimethyl diallyl ammonium chloride)−reinforced multifunctional poly (vinyl alcohol)/ polyaniline hydrogels as flexible sensor materials

The design of multifunctional hydrogel sensor materials with comprehensive properties such as frost resistance, good reusability, adhesion, and flexibility needs to be developed to meet the demands of complex environments. Herein, a conductive, semi-interpenetrating network hydrogel was constructed from poly (vinyl alcohol), polyaniline (PANI), and poly (dimethyl diallyl ammonium chloride) (PDDA), and the process assisted by the Hofmeister effect. A double conductive pathway hydrogel with types of PDDA and PANI polymers was formed simultaneously to provide excellent conductivity (1.217 S/m−1) for the hydrogel. With the increase in the concentration of PDDA from 0 to 16 wt%, the mechanical strength increased from 0.066 MPa to 0.34 MPa, and the modulus of elasticity and toughness increased by 684.9% and 748.8%, respectively. The hydrogel can be efficiently generated as a strain sensor material with excellent sensitivities of GF= 2.337 and S= 3.229%/KPa under tension and compression, respectively. The hydrogel could be used as an electronic skin and be used for the monitoring of even small strains in the skin caused by pulse beats. In addition, the hydrogel has excellent temperature sensitivity (1.575%/℃), frost resistance (−53.45 ℃), self-healing capability, and reusability. Data AvailabilityData will be made available on request.

Preparation of conductive polyaniline hydrogels co‐doped with hydrochloric acid/phytic acid and their application in Ag NPs@PA/GCE biosensor for H2O2 detection

AbstractAccurate measurement of hydrogen peroxide is of great significance in monitoring human diseases and environmental safety. At present, there are a variety of testing methods, among which the use of electrochemical sensors to accurately measure hydrogen peroxide has gradually become a research hotspot. In this article, phytic acid (PA) with dual functions of doping and cross‐linking and HCl with strong ionization capacity was introduced as dopants to co‐doping polyaniline, and polyaniline hydrogel with a three‐dimensional network structure was prepared. The influence of the HCl/PA co‐doping ratio on conductive polyaniline hydrogel (CPAniH) was explored. The synthesis process and mechanism of HCl/PA‐CPAniH were analyzed and explained. In addition, the conductivity and mechanism of HCl/PA‐CPAniH, as well as the hydrogel characteristics were characterized and studied. A new electrochemical sensor based on polyaniline hydrogel and silver nanoparticles was constructed to detect hydrogen peroxide. The sensor has a good linear relationship, a wide linear range, and a high‐detection limit for H2O2. In addition, it also shows that HCl/PA‐CPAniH is a good interface material for electrochemical sensors and has a certain application potential.

Recent advances in polyaniline-based micro-supercapacitors.

The rapid development of the Internet of Things (IoTs) and proliferation of wearable electronics have significantly stimulated the pursuit of distributed power supply systems that are small and light. Accordingly, micro-supercapacitors (MSCs) have recently attracted tremendous research interest due to their high power density, good energy density, long cycling life, and rapid charge/discharge rate delivered in a limited volume and area. As an emerging class of electrochemical energy storage devices, MSCs using polyaniline (PANI) electrodes are envisaged to bridge the gap between carbonaceous MSCs and micro-batteries, leading to a high power density together with improved energy density. However, despite the intensive development of PANI-based MSCs in the past few decades, a comprehensive review focusing on the chemical properties and synthesis of PANI, working mechanisms, design principles, and electrochemical performances of MSCs is lacking. Thus, herein, we summarize the recent advances in PANI-based MSCs using a wide range of electrode materials. Firstly, the fundamentals of MSCs are outlined including their working principle, device design, fabrication technology, and performance metrics. Then, the working principle and synthesis methods of PANI are discussed. Afterward, MSCs based on various PANI materials including pure PANI, PANI hydrogel, and PANI composites are discussed in detail. Lastly, concluding remarks and perspectives on their future development are presented. This review can present new ideas and give rise to new opportunities for the design of high-performance miniaturized PANI-based MSCs that underpin the sustainable prosperity of the approaching IoTs era.

3D Print Polyaniline/Gelatin Hydrogels as Wearable Multifunctional Sensors

AbstractGelatin is a good biocompatible material. Polyaniline is a polymer compound that can conduct electricity when doped with phytic acid (Ph). However, there are few reports on PANI and gelatin hydrogels. In this paper, a new synthesis method of polyaniline (PANI) was developed, which greatly improved the gas sensitivity while maintaining the excellent quality of PANI. PANI and gelatin were composited into a unified 3D network. ANI synthesized phytic acid‐doped PANI and then mixed gelatin with it to make wearable 3D printed sensors. Multilayer structures prepared by 3D printing with PANI ink are free of build‐up. A PANI hydrogel sensor was fabricated using a 3D printing method with a stress sensing range of 0–899.8 MPa, a strain sensing range of 0–764.4 % sensitivity GF=1.4, and a TCR=−1.3 for temperature 8.4–29 °C. The sensor can accurately detect the motion of large strains in human knee joints and small strains in finger bending. In this study, a simple “green” method was used to convert inexpensive gelatin into a high‐performance multifunctional wearable sensor, which can be recycled and provided application prospects for sustainable and environmentally friendly biocompatible materials in the future.

Natural Glycyrrhizic Acid-Tailored Homogeneous Conductive Polyaniline Hydrogel as a Flexible Strain Sensor.

Polyaniline (PANi) hydrogels often exhibit highly mechanical and electrochemical properties, which have received extensive attention in the fields of batteries, supercapacitors, and sensors. However, the shortcomings such as hydrophobicity and easy aggregation of PANi frequently result in deterioration of mechanical and electrochemical performance of PANi hydrogels. Here, a bifunctional natural product, glycyrrhizic acid (GL), is utilized to prepare the homogeneous conductive PANi hydrogel, because GL not only can assemble into supramolecular hydrogel as the biocompatible matrix but also can salinize aniline monomers to facilitate the polymerization in situ to form uniformly dispersed PANi within GL matrix. Accordingly, the resulting GL/PANi hydrogel shows the Tyndall effect caused by the nanoclusters entangled by nanofibers and exhibits an improved storage modulus G' (3.2 kPa) and loss modulus G″ (0.9 kPa), as well as the expected conductivity (0.17 S·m-1). In addition, the GL/PANi hydrogel is further reinforced by blending poly(vinyl alcohol) (PVA) for the required strength and stretchability as a flexible strain sensor. The results reveal that the obtained PVA/GL/PANi hydrogel has a fracture stress of 693 kPa at an elongation of 329%, with a fracture toughness of 82 MJ·m-3 and Young's modulus of 47.9 kPa. Its gauge factor (GF) is measured to be 2.5 at lower strain (<130%) and up to 4.3 at larger strain (>130%). This good sensitivity and sensing stability make the PVA/GL/PANi hydrogel effectively monitor relevant human motion detections. Our work provides an innovative strategy to manufacture the homogeneous conductive PANi hydrogel for high-performance soft electronic devices.

Unveiling the surface dominated capacitive properties in flexible ternary polyaniline/NiFe2O4/reduced graphene oxide nanocomposites hydrogel electrode for supercapacitor applications

The 3D ternary nanocomposites hydrogel have been effectively fabricated on carbon cloth using a two-step synthesis approach. Nickel ferrite nanoparticles (NiFe2O4) prepared by template method have been dispersed onto/within rGO nanosheets leading to the formation of NiFe2O4/rGO (NFG) nanocomposites. Afterward, polyaniline hydrogel has been polymerized on NFG nanosheets to prepare ternary polyaniline/NiFe2O4/rGO hydrogel (PNFG) nanocomposites on carbon cloth that can be further utilized as a binder-free supercapacitor electrode. The resulting 3D ternary nanocomposites hydrogel achieved maximum specific capacitance of 1134.28 F/g at a current density of 1 A/g and 76.46 % of capacitive retention at 10 A/g. The supercapacitor electrode exhibited outstanding rate capability and superior cyclic stability up to 5000 successive cycles. In addition, the symmetric supercapacitor cell delivered 0.61 kW/kg of specific power and 19.29 Wh/kg of specific energy. The excellent electrochemical characteristics of PNFG is ascribed to its well-designed 3D microstructure and the synergistic effect created by the capacitive mechanism due to electric double layer capacitance (EDLC) and pseudocapacitance (surface redox reactions) as well as diffusion-controlled mechanism (faradaic redox reactions). It has been revealed that the overall electrode reaction is dominated by surface-controlled processes, with a small contribution from diffusion-controlled faradaic processes.