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Flexible electrochromic devices (FECDs) are widely explored for diverse applications including wearable electronics, camouflage, and smart windows. However, the manufacturing process of patterned FECDs remains complex, costly, and non‐customizable. To address this challenge, a strategy is proposed to prepare integrated FECDs via multi‐material direct writing 3D printing. By designing novel viologen/polyvinyl alcohol (PVA) hydrogel inks and systematically evaluating the printability of various inks, seamless interface integration can be achieved, enabling streamlined manufacturing of patterned FECDs with continuous production capabilities. The resultant 3D‐printed FECDs exhibit excellent electrochromic and mechanical properties, including high optical contrast (up to 54% at 360 nm), nice cycling stability (less than 5% electroactivity reduction after 10 000 s), and mechanical stability (less than 19% optimal contrast decrease after 5000 cycles of bending). The potential applications of these 3D‐printed hydrogel‐based FECDs are further demonstrated in wearable electronics, camouflage, and smart windows. [ABSTRACT FROM AUTHOR]

This study presents the development of flexible piezoelectric nanogenerators (PENGs) utilizing graphitic carbon nitride (g-C3N4) nanoflakes (CNNFs) and polyvinylidene fluoride (PVDF) composites fabricated via the direct ink writing (DIW) 3D printing method. A novel approach of synthesizing CNNFs using the ethanol exfoliation method was demonstrated, which significantly reduces preparation time and cost compared to traditional acid exfoliation. The CNNFs are incorporated into PVDFs at varying weight percentages (5, 7.5, 10, and 15 wt.%) to optimize the β-phase content and piezoelectric properties. Characterization techniques including XRD, FTIR, and FESEM confirm the successful synthesis and alignment of nanoflakes inside the PVDF matrix. The film with 7.5% CNNF achieves the highest performance, exhibiting a peak output voltage of approximately 6.5 V under a 45 N force. This study also explores the effects of UV light exposure. Under a UV light, the film exhibits an output voltage of 8 V, indicating the device's durability and potential for practical applications. The fabricated device showed significant voltage outputs during various human motions, confirming its suitability for wearable self-powered IoT applications. This work highlights the efficacy of the ethanol exfoliation method and the DIW printing technique in enhancing the performance of flexible PENGs. [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries (AZIBs) based on vanadium oxides or sulfides are promising candidates for large‐scale rechargeable energy storage due to their ease of fabrication, low cost, and high safety. However, the commercial application of vanadium‐based electrode materials has been hindered by challenging problems such as poor cyclability and low‐rate performance. To this regard, sophisticated nanostructure engineering technology is used to adeptly incorporate VS2 nanosheets into the MXene interlayers to create a stable 2D heterogeneous layered structure. The MXene nanosheets exhibit stable interactions with VS2 nanosheets, while intercalation between nanosheets effectively increases the interlayer spacing, further enhancing their stability in AZIBs. Benefiting from the heterogeneous layered structure with high conductivity, excellent electron/ion transport, and abundant reactive sites, the free‐standing VS2/Ti3C2Tz composite film can be used as both the cathode and the anode of AZIBs. Specifically, the VS2/Ti3C2Tz cathode presents a high specific capacity of 285 mAh g−1 at 0.2 A g−1. Furthermore, the flexible Zn‐metal free in‐plane VS2/Ti3C2Tz//MnO2/CNT AZIBs deliver high operation voltage (2.0 V) and impressive long‐term cycling stability (with a capacity retention of 97% after 5000 cycles) which outperforms almost all reported Vanadium‐based electrodes for AZIBs. The effective modulation of the material structure through nanocomposite engineering effectively enhances the stability of VS2, which shows great potential in Zn2+ storage. This work will hasten and stimulate further development of such composite material in the direction of energy storage. [ABSTRACT FROM AUTHOR]

Before steel can be utilized, pickling is necessary to remove surface oxidation products. However, as the ferrous ion concentration in the pickling solution increases, the pickling rate significantly diminishes, necessitating the treatment of spent pickling solution (SPS) to mitigate its hazardous effects prior to disposal. Current industrial methods predominantly rely on neutralization and precipitation techniques, which are cost-prohibitive and generate substantial by-products, thus failing to meet environmental protection standards. In this study, a new method, which is based on the formation of FeC2O4·2H2O precipitate in a strong acid solution, is proposed to treat the SPS. Initially, the SPS undergoes a two-step impurity removal process, followed by the controlled addition of oxalic acid dihydrate (H2C2O4·2H2O) to precipitate iron. The resulting precipitate is filtered, washed, and vacuum-dried, and the regenerated acid is recycled back into the pickling tank. When 1 g/10 mL of H2C2O4·2H2O is used, the iron removal rate achieves 60%, and the acidity of the regenerated acid increases by 11.3%. X-ray diffraction pattern (XRD) and thermogravimetric–differential scanning calorimetry (TG-DSC) characterization showed that the precipitate was α-FeC2O4·2H2O, with an average particle size of about 3.19 μm and a purity of 95.24%. This process innovatively achieves efficient recycling of acid and iron resources, offering a potential solution to the industrial challenge of difficult SPS treatment in the steel industry and meeting the urgent need for sustainable development. [ABSTRACT FROM AUTHOR]

Electronic devices based on conducting polymer hydrogels have emerged as one of the most promising implantable bioelectronics for electrophysiological monitoring and diagnosis of a wide spectrum of diseases, in light of their distinct conductivity and biocompatibility. However, most conducting polymer hydrogels‐based bioelectronics are routinely fabricated through conventional techniques, which are challenged by its intrinsic poor processability of conducting polymers, as well as the essentially fragile biointerface, thus hampering their rapid innovation and application in advanced implantable bioelectronics. Here, 3D printable hydrogels based on poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is reported, featuring superior 3D printability for direct ink writing (DIW), tissue‐like mechanical compliance (Young's modulus of 650 kPa), instant and tough bioadhesion (interfacial toughness of 200 J m−2 and shear strength of 120 kPa), highly‐tunable electrical properties, as well as long‐term in vitro and in vivo structural and electrochemical robustness. Electro‐physiological studies rat heart models with normal or arrhythmic conditions highlight the capabilities of establishing conformal biointerface with the dynamic organs, allowing for long‐term and high‐precision spatiotemporary epicardial electrophysiological monitoring, as well as electrical modulation of acute myocardial infarction (MI) model. These advances provide a promising strategy to improve the tissue‐electronics interfacing, and could serve as the basis for the next generation bioelectronics toward healthcare monitoring, diagnosis and medical therapies. [ABSTRACT FROM AUTHOR]

High‐density surface electromyography (sEMG) electrode arrays enable the recording of tens to hundreds of channels of electromyographic signals, which have found wide applications in clinics and human‐machine interfaces. However, current manufacturing technologies of high‐density sEMG electrode arrays generally involve high‐cost equipments, complicated procedures, and insufficient programmability, severely hampering the rational design and practical applications of customized yet cost‐effective high‐density electrode arrays. Herein, the facile and efficient fabrication of novel 32‐channel soft high‐density sEMG electrode arrays by an all‐printed technique based on multimaterial direct ink writing 3D printing is presented. By employing rational four‐layer stacked structure designs with systematic ink printability evaluation, it can successfully realize seamless interfacial integration during the multimaterial printing, achieving reproducible, programmable, continuous fabrication of soft high‐density sEMG electrode arrays. The all 3D‐printed soft electrode arrays exhibit excellent stability, low impedance, and high signal‐to‐noise ratio superior to commercial products with an increase of 32.2%. Such intriguing properties enable this all 3D‐printed electrode arrays the unique capability of mapping muscle activation of the forearm, and the motor unit action potential trains can be precisely identified for varying hand gestures to effectively explore the innovative human‐machine interface toward diverse applications such as teleoperation and prosthetic control. [ABSTRACT FROM AUTHOR]

The development of asymmetric supercapacitors (ASCs) with high power and energy density is greatly restricted by the low capacitance of the anode materials. V2O5 is a promising anode material with high theoretical capacity, but its low conductivity and high dissolution are not conducive to applications in energy storage. Herein, oxygen-vacancy PEDOT/V2O5 ultrathin nanosheets with a thickness of about 4.4 nm are fabricated by the oxidative polymerization of EDOT monomers on V2O5 nanosheets in the absence of other oxidants. The results of XPS and EPR confirm that the polymerization of PEDOT increases the oxygen vacancy concentration of V2O5. The PEDOT/V2O5 nanosheets exhibit a specific capacitance of 406 F g−1 at 2 mV s−1 and excellent cyclic stability in the mixed organic electrolyte of dimethyl carbonate and ethylene carbonate. The energy density of ASCs composed of PEDOT/V2O5 as the anode and activated carbon as the cathode reaches 65 W h kg−1 at a power density of 1490 W kg−1. This means that PEDOT/V2O5 has enormous potential in high-energy storage. [ABSTRACT FROM AUTHOR]

Conducting polymer hydrogels are widely used as strain sensors in light of their distinct skin‐like softness, strain sensitivity, and environmental adaptiveness in the fields of wearable devices, soft robots, and human‐machine interface. However, the mechanical and electrical properties of existing conducting polymer hydrogels, especially fatigue‐resistance and sensing robustness during long‐term application, are unsatisfactory, which severely hamper their practical utilities. Herein, a strategy to fabricate conducting polymer hydrogels with anisotropic structures and mechanics is presented through a combined freeze‐casting and salting‐out process. The as‐fabricated conducting polymer hydrogels exhibit high fatigue threshold (>300 J m−2), low Young's modulus (≈100 kPa), as well as long‐term strain sensing robustness (over 10 000 cycles). Such superior performance enables their application as strain sensors to monitor the real‐time movement of underwater robotics. The design and fabrication strategy for conducting polymer hydrogels reported in this study may open up an enticing avenue for functional soft materials in soft electronics and robotics. [ABSTRACT FROM AUTHOR]

Soft electronics have emerged as a prominent research domain, with diverse applications from medical monitoring to soft robotics. Liquid metal (LM) has emerged as a promising material for soft electronics due to its high electrical conductivity (3.4 × 106 S m−1) and fluidity at room temperature. However, the dispersion of LM nanoparticles and the performance of LM composites in soft electronics applications have not been extensively explored. In this study, a novel approach for the direct dispersion of LM nanoparticles in biocompatible hyaluronic acid (HA) to create multifunctional LM/HA hydrogels is presented. The LM/HA hydrogel displays remarkable electromechanical properties, including high stretchability (2,700%) and conductivity (116 S m−1), as well as excellent sensitivity (GF = 4.8) as a sensing material. Specifically, a facial expression monitoring system is developed utilizing the LM/HA hydrogel as the sensing material, along with a microcontroller, signal‐processing circuits, and a Bluetooth transceiver. The LM/HA hydrogel adheres closely to the skin surface to ensure the accuracy of facial expression monitoring. In summary, this study not only advances the understanding of the properties of LM but also expands the potential application scenarios of multifunctional LM hydrogels in soft robotics and implantable sensors. [ABSTRACT FROM AUTHOR]