High Electrical Output Research Articles

Performance Enhancement of Thermoelectric Generator‐Radiative Cooling System With Thermal and Electrical Energy Storage

ABSTRACTA thermoelectric generator (TEG) converts thermal energy into electrical energy when temperature gradients are created across its two surfaces. Integrating the TEG with a phase change material (PCM) and radiative cooling (RC) can increase the temperature gradient across its two surfaces. In this study, a two‐layer RC paint has been developed and applied to the cold side of a TEG, and its performance was compared with TEG‐white paint and TEG‐no paint. The RC lowers the temperature of the cold side by 3.5°C and 4.7°C compared to TEGs with white paint and no paint, respectively. Integrating PCM with TEG–RC ensured a high electrical output, enabling continuous power for a typical weather sensor. The PCM–TEG–RC generated 2.7and 0.61 mW during summer and winter days in Istanbul, and nighttime outputs of 0.302 W and 0.395 mW, respectively. Despite similar costs, the electrical performance of TEG–RC was nearly double that of the TEG‐white paint. It has also been determined that a storage capacitor with a value of 0.5 F can provide 24‐h power backup to the typical weather sensor.

Effective rare-earth dielectric addition and gamma ray irradiation for achieving highly efficient PDMS triboelectric nanogenerator

This research aims to develop the flexible triboelectric nanogenerator (TENG) using PDMS polymer as the main tribo-material and composite with dielectric rare earth oxide, lanthanum chromite compound; LaCrO3, to enhance generated charge density, before add-on its higher electrical output with gamma ray irradiation. Upon study the effect of different amounts of the loaded LaCrO3 and various doses of gamma ray, the optimum condition can be obtained. The PDMS/LaCrO3 at 5 wt% can reach open-circuit voltage (VOC) and shot-circuit current (ISC) at 89 V and 448 μA. The impressive results of output further appear by additional irradiated gamma radiation. At 150 kGy dose of Irradiated gamma ray, VOC and ISC can jump to 161 V and 963 μA. These output signals, especially ISC, can be ∼34 times higher than that of the pristine PDMS. Scientific discussion regarding characterization, operating mechanism, dielectric properties and electrical output is provided. The practical application of being a small power source is also developed. Therefore, this research can show another useful application of gamma ray in the field of materials design for energy harvesting devices. The knowledge provided in this research can also serve as potential guidance in the field of specific TENG utilization.

Polymer-metal film induced ultrahigh output TVNG and self-powered intelligent sensor system assisted by EEMD

Tribovoltaic nanogenerators (TVNGs) based on tribovoltaic effect can output DC current directly, and has the advantages of high output current density and low internal resistance. While TVNGs have been restricted by its low output voltage and power. Herein, we have developed a metal-polymer film with a micro-uneven structure on the surface, much higher corrosion resistance and wear resistance than metal. On this basis, a centimeter-level sliding structure metal-EP/GaN-TVNG has been fabricated, which shows a high and stable long-term DC electrical output (a maximized power output of 4.19 W/m2 when matched with a 0.07 MΩ resistor, a stable output current of 2.25 A/m2 and a peak Voc of 27 V). Further, a TVNG vehicle travelling intelligent sensor and system which can integrate electrical signals collected by TVNG into digital signal processing algorithms and then feed backing to the driving system, has been designed and manufactured. As an effective method for deep analysis of signals, Ensemble Empirical Mode Decomposition (EEMD) has been used for the first time for deep processing of nanogenerator signals in this work. This work provides a new model of further development of high output TVNG and a new deep signal processing methods of TVNG/TENG signal.

Polypyrrole@TiO2 Composite Nanotube System with Enhanced Capillary Fluid and Charge Transfer for High‐Current Hydrovoltaic Energy Generation and Seawater Purification

AbstractHarnessing the energy generated from the evaporation of water has received considerable research attention in materials science; however, challenges such as poor conversion efficiency and low current output persist. Herein, an innovative synergistic material system based on titanium dioxide nanotubes coated with polypyrrole (PPy@TiO2NTs) is introduced for the simultaneous production of electricity and clean water from solar energy and seawater. The tubular structure of PPy@TiO2NT and the molecular interactions between TiO2 and PPy produce enhanced charge transfer, thereby providing the advantages of the hydrovoltaic effect, solar‐driven water evaporation (SWE), and photocatalysis. Consequently, PPy@TiO2NT‐loaded melamine foam can produce tens or more than a hundred microamperes of current in water of various salinities, which is an order of magnitude improvement over previously reported hydrovoltaic evaporation systems. In addition, under 1 sun irradiation, the system achieved an SWE rate of 2.13 kg m−2 h−1 and a methylene blue removal rate of more than 90% within 2 h. The proposed material system, featuring high electrical output and outstanding dual‐mechanism water treatment capabilities, shows high potential for synergistically harnessing solar energy and seawater, as well as for environmental management.

Advanced Design of Organic Ionic Materials for the Boost of Electricity Generation, Storage, and Utilization

AbstractIt is a great desire of advanced designed materials for electricity generation, storage, and utilization with boosted activity, multifunctionality, compatibility, stability, and durability. Organic ionic materials (OIMs) with superior conductivity, modifiability, and thermal/cold tolerance have great potential in meeting the demand. Ionic liquids, ionic polymers, polyelectrolytes, and new‐emerging composite materials like ionic gels, ionic woods, and metallated covalent organic frameworks have been boomingly developed in recent years, with elaborated design of which, enhanced performance of burgeoning energy materials such as higher electrical output, larger energy capacity, wider tolerance of temperature and/or humidity, and longer durability have been promoted. Despite a few reviews that have generalized the applications of single‐type OIMs in a certain field, there is a lack of comprehensive reviews focusing on advanced design of OIMs for boosting electricity generation, storage, and utilization. Herein, the new development of OIMs is timely and systematically reviewed focusing on electricity generation (generators), storage (batteries and supercapacitors), and utilization (sensors and actuators). Synthesis and modification strategies are summarized for material design, after which, fundamentals and mechanisms are illustrated as theoretical support. Then, advanced designs of OIMs are elaborated by taking electricity generation, storage, and utilization processes into consideration, followed by putting forward perspectives.

A Self-Assembled Multiphasic Thin Film as an Oxygen Electrode for Enhanced Durability in Reversible Solid Oxide Cells.

The implementation of nanocomposite materials as electrode layers represents a potential turning point for next-generation of solid oxide cells in order to reduce the use of critical raw materials. However, the substitution of bulk electrode materials by thin films is still under debate especially due to the uncertainty about their performance and stability under operando conditions, which restricts their use in real applications. In this work, we propose a multiphase nanocomposite characterized by a highly disordered microstructure and high cationic intermixing as a result from thin-film self-assembly of a perovskite-based mixed ionic-electronic conductor (lanthanum strontium cobaltite) and a fluorite-based pure ionic conductor (samarium-doped ceria) as an oxygen electrode for reversible solid oxide cells. Electrochemical characterization shows remarkable oxygen reduction reaction (fuel cell mode) and oxygen evolution activity (electrolysis mode) in comparison with state-of-the-art bulk electrodes, combined with outstanding long-term stability at operational temperatures of 700 °C. The disordered nanostructure was implemented as a standalone oxygen electrode on commercial anode-supported cells, resulting in high electrical output in fuel cell and electrolysis mode for active layer thicknesses of only 200 nm (>95% decrease in critical raw materials with respect to conventional cathodes). The cell was operated for over 300 h in fuel cell mode displaying excellent stability. Our findings unlock the hidden potential of advanced thin-film technologies for obtaining high-performance disordered electrodes based on nanocomposite self-assembly combining long durability and minimized use of critical raw materials.

Macroscopic liquid superlubric triboelectric nanogenerator: An in-depth understanding of solid-liquid interfacial charge behavior

Triboelectric nanogenerator (TENG) has been seen as one of the most promising energy harvesting technologies. However, there are an irreconcilable contradiction between low friction and high electrical output performance of the TENG. Here, we have devised a macroscale liquid superlubric triboelectric nanogenerator based on solid-liquid-solid structure, leveraging the concept of liquid superlubricity technology, resulting in a remarkable increase in both the open circuit voltage and short-circuit current by 53.0 % and 58.4 %, respectively. This huge increase in electrical output performance is accompanied by a 99.1 % reduction in friction coefficient (≈ 0.0025) and 99.993 % reduction in wear rate (≈ 0.76×10−7 mm3/N·m), when compared to those of a lubricant-free triboelectric nanogenerator. This work delves into the lubrication and charge transfer mechanisms. The liquid superlubricity technology achieves friction reduction through a hybrid mechanism combining boundary and hydrodynamic lubrication. And the high outputs arise from the charges transfer at solid-liquid interface. The triboelectric charges generated by the friction pair are transferred from solid to the lubricating liquid. Meanwhile, the lubricating liquid promotes electron transfer and contributes additional electrons. Our work provides profound insights into the lubrication and charge transfer mechanisms at solid-liquid interfaces, and addresses the paradox of high output and low friction in TENGs.

A novel tiny triboelectric acoustic sensor design based on nanocomposite enhancement for highly-sensitive, broadband, and self-powered multi-functional applications

This work proposes a novel acoustic nanocomposite fibrous membrane-based triboelectric nanogenerator (NFM-TENG) with excellent acoustical-to-electrical conversion performance. The optimal combination for the triboelectric pairs of NFM-TENG is identified: a polyvinylidene fluoride-multiwalled carbon nanotubes (PVDF-MWCNTs (1 wt%)) nanofibrous membrane as the tribo-positive layer, and a corona-charged fluorinated ethylene-propylene (FEP) solid membrane as the tribo-negative layer, resulting in higher electric output than single-friction-layered NFM-TENG (32 times). Under the acoustic excitation of 116 dB at 200 Hz, the acoustic NFM-TENG can generate a maximum areal power density of 3.78 W/m2. The NFM-TENG can be used not only as a acoustic energy harvester, but also as a self-powered triboelectric acoustic sensor (TAS) for real-time voice recording and control. For convenience, for the first time, an advanced tiny TAS (TTAS, diameter: only 9.7 mm) based on the NFM-TENG is developed and its sensitivity is calibrated as -50 dB according to the International standard IEC61094. Experimental results also verified that the TTAS with broadband response ability (20–20,000 Hz) is fully competent for commercial applications such as real-time voice control, HMI, and other multi-scenarios. The TTAS is smart, reliable and customizable, potentially leading to a new revolution in intelligent interaction.

Investigating the properties of nanoparticles from heveabrasiliensis shell for coolant application in PEMFCs

Extensive consumption of petroleum-based products, which has resulted in energy depletion, prompted a need to seek alternative and renewable means of transportation. PEMFCs can achieve high power density, low operating temperatures, rapid start-up, and clean energy, making them ideal for transportation. Several studies have demonstrated that conventional cooling agents, such as water or water with ethylene glycol, do not dissipate heat efficiently in PEMFCs, resulting in deteriorating performance and a shortened operational lifespan over time. The incorporation of bio-sourced nanofluids as an alternative coolant for Proton Exchange Membrane (PEM) fuel cells is the newest venture to take over PEM fuel cell development. Utilizing bio-sourced nanofluids is being evaluated for elevating the heat conduction and decreasing the electrical conductivity of proton exchange membrane fuel cells (PEMFCs). The objective of this article is to investigate Hevea brasiliensis Shell (HBS)-based nanofluids dispersed in water and Ethylene glycol (EG) at varying concentrations of 0.1 vol%, 0.3 vol%, and 0.5 vol% by paying attention to improving heat transfer, extracting high electrical output, reducing pump loss, and increasing the longevity of cells. As an adverse effect, incorporating HBS at a 0.5 % volume concentration within an 80:20 mixture of water and ethylene glycol (W:EG) resulted in an 8 % improvement in heat transfer and a 77 % increase in electrical conductivity when compared to W:EG (80:20), which is promising as a pertinent cooling technique for PEMFC stacks.

Phosphor‐Loaded Triboelectric Film‐Based Multipurpose Triboelectric Nanogenerators for Highly‐Efficient Energy Harvesting, Sensing, and Self‐Illumination Applications

AbstractA novel approach is proposed for combining phosphor materials with triboelectric nanogenerators (TENGs) for mechanical energy harvesting and illumination applications. For this purpose, strongly reddish‐orange‐emitting Ba0.5Sr0.5Nb2O6:0.25 mol Eu3+ (BSNb:0.25Eu) phosphor materials are synthesized. The photoluminescence properties of the synthesized BSNb:0.25Eu are analyzed. The synthesized BSNb:0.25Eu is utilized as a dielectric filler inside a polydimethylsiloxane polymeric film due to its high dielectric properties to improve the overall dielectric properties of the composite film (CF). TENG devices are fabricated using phosphor‐loaded CFs as the tribonegative layer, transparent polyvinyl alcohol as the tribopositive layer, and aluminum as the conductive electrode. All the TENGs operate in a contact‐separation mode, and the highest electrical output is attained by optimizing the phosphor filler concentration in the CF. The optimized TENG exhibits excellent stability in long‐term operational tests, under varying harsh ambient temperatures. Indium tin oxide sputtered on both triboelectric films as an electrode and combined with a transparent hard substrate to obtain a fully transparent TENG. A self‐illuminating TENG (SI‐TENG) is fabricated by integrating near‐ultraviolet light‐emitting diodes between two identical TENGs. The SI‐TENG can harvest the mechanical energy available in the surrounding environment and illuminate it as a light source. Additionally, the proposed phosphor‐loaded polymer films can be employed for optical thermometry and mechanical energy harvesting via SI‐TENG on a large scale.

Multifunctional electronic skins for ultra-sensitive strain, temperature, humidity sensing, and energy harvesting

Though gaining increasing attention in various portable and wireless electronic devices and sensors, flexible gels used in strain sensors and triboelectric nanogenerators (TENGs) still suffer from inferior mechanical properties and lack long-term stability. Herein, multifunctional electronic skins (e-skin) from oriented 2D nanosheets enhanced eutectogel were facilely fabricated via a one-step curing strategy with excellent transparency (96%), superb elasticity (1613%), toughness (17.22 MPa). Moreover, the multifunctional e-skin also exhibits temperature and humidity sensibility. Notably, the as-assembled TENG e-skin exhibits high and stable electrical output performances, including an open-circuit voltage of 224 V, short-circuit current of 7.1 μA, and short-circuit charge of 640 nC. Meanwhile, the TENG can easily light up 130 LEDs, charge capacitors to drive a calculator, and sustain a long service life (120 days). Furthermore, it can serve as a self-powered biomechanical sensor to realize the real-time monitoring of various human motions, showing application potentials in wearable electronics, human health management, and energy harvesting systems.

Sodium alginate/carbon nanotube energy harvesting fibers: Axial functional group gradient and moist-electric performance

Moist-electric generation, a green and environmentally friendly energy harvesting technology, is undoubtedly one of the effective methods to alleviate energy shortages and environmental damage. However, the lack of fiber-like moist-electric generators (MEGs) that combine continuous power generation and high electrical output performance has constrained the development of moist-electric in the fields of flexible wearable and self-power supplies. In this work, sodium alginate (SA)/multi-walled carbon nanotubes (MWCNT) fibers with axial heterogeneous (axi-he) of oxygen-containing functional groups (Ocfgs) are prepared through a mold forming method in assistance with the coagulation process. The interaction between axi-he MEG and moisture is investigated by analyzing the electrical signal changes of dried MEG under moisture stimulation. The maximum output voltage and current of axi-he MEG can reach 0.35 V and 1.92 μA under the stimulation of moisture. Based on the regulation of Ocfgs, axi-he MEG has a continuous high moist-electric performance and environmental adaptability. The maximum output power density (Pmo) of axi-he MEG with a length of only 2 cm can reach 27.37 μW cm–2 at RH = 90 %, which exceeds most of the MEGs reported in literature. Meanwhile, a continuous output voltage of 0.33–0.37 V for more than 15 h can be obtained from this axi-he MEG. Thus, the axi-he MEG from Ocfg distribution design and mold forming method provides a new way of clean energy generation using moisture from the ambient environment, exhibiting enormous potential in energy supply for Internet of Things (IoT) devices.

Polarity control of siloxane composite films for triboelectric nanogenerator based self-powered body temperature monitoring

Body temperature monitoring systems serve as key indicators for identifying potential patients with various illnesses such as influenza and COVID-19. Conventionally, these monitoring devices rely on batteries, limiting their long-term and widespread application. Self-powered thermometers are considered a sustainable solution that enable continuous monitoring. Among various self-charging power sources, triboelectric nanogenerators (TENGs) are a novel development, but suffer several critical drawbacks for medical applications. In this study, we present a high-performance TENG for self-powered body temperature monitoring systems by controlling the polarity of glass-fabric reinforced vinyl-thiol functionalized hybrid materials (GFR-VTHs) by varying the phenyl group contents. The effect of polarity modification on the performance of the developed TENG was confirmed by the high electrical output and stable operation under 10,000 cycles of repetitive pressing tests. Finally, self-powered body temperature monitoring systems were constructed by measuring human body temperature with a clinical thermometer powered by the GFR-VTH-based TENG, demonstrating device feasibility as a power source for self-powered healthcare systems.

Hydrogel-based flexible degradable triboelectric nanogenerators for human activity recognition

The development of Internet of Things (IoT) and Artificial Intelligence (AI) technologies has led to an increased demand for wearable electronic devices that can be used in a variety of contexts. Hydrogel sensors have been regarded as an ideal material for the fabrication of multifunctional flexible wearable devices. However, it is difficult to create hydrogel sensors with ideal electrical and mechanical properties. In this study, a conductive hydrogel prepared by a simple method has been introduced. The hydrogel was immersed in a binary solvent of glycerol, water and sodium citrate to form a transparent, long-term stable and highly conductive gelatin-NaCl organohydrogel (GNOH). A stretchable and durable gelatin Ecoflex triboelectric nanogenerator (GE-TENG) was created by combining an organic hydrogel with Ecoflex elastomer. It has high electrical and mechanical performance, with an open-circuit voltage of 142 V, current of 3.8 μA, power output of 19.36 μW and response time of 85 ms. Moreover, the single-electrode mode of the GE-TENG provides high electrical output for powering portable electronic devices and can capture biomechanical energy in temperatures as low as −20 °C. As a result of these capabilities, GE-TENG can effectively identify human movements with precision and transmit signals wirelessly, thereby broadening its potential applications. The GE-TENG-based self-powered intelligent sensing system (GSIS) for human-computer interaction demonstrates a wearable intelligent system for controlling the movement of a tank model and a manipulator by integrating the signal acquisition, signal processing and signal output components. The system achieves 100% signal recognition accuracy when combined with covariance matrix feature analysis and Convolutional Neural Network classification algorithms. This research demonstrates the potential of wearable hydrogel-based electronic devices for monitoring human motion, harvesting biomechanical energy and human-computer interaction.

Microelectronic printed chitosan/chondroitin sulfate/ZnO flexible and environmentally friendly triboelectric nanogenerator

The triboelectric nanogenerator (TENG) of natural biomaterials is a new type of energy harvesting device and can be used as a self-powered sensor, which has received extensive research and attention. In this paper, based on the biocompatibility of chitosan and chondroitin sulfate, ZnO-modified chitosan/chondroitin sulfate/ZnO TENG was prepared for research on wearable devices and sustainable power supply devices. This study employs molecular dynamics to compute the interaction energy between chitosan and ZnO molecules. Theoretical calculations have unequivocally substantiated the occurrence of a binding interaction between these two molecular entities. The effect of ZnO on chitosan/chondroitin sulfate morphology was investigated by atomic force microscopy. The chitosan/chondroitin sulfate/ZnO TENG has high flexibility and electrical output performance. It can reach 105 V and 3.3 µA of open-circuit voltage and short-circuit current. Chitosan/chondroitin Sulfate/ZnO TENG successfully converts the mechanical energy of human motion into electrical energy. Strong electrical signals are exhibited when making fists and waving fingers and wrists. The TENG is a self-powered source and lights up 70 blue light-emitting diodes (LEDs). The chitosan/chondroitin sulfate/ZnO TENG has demonstrated its capabilities in energy harvesting and wearable self-powered sensors.

Optimising fundamental knitting parameters for wearable triboelectric nanogenerators

During the past decade, Triboelectric Nanogenerators (TENG) have demonstrated their potential as an energy harvesting and self-powered sensing technology for future wearable applications. Among various TENG architectures, knitted textile TENGs have become increasingly popular in recent times, as they provide advantages such as high electrical outputs, very good mechanical properties and excellent wearability. However, there is still a lack of understanding on how to engineer the knitting parameters to maximize the electrical output generation of knitted textile TENGs. Herein, for the first time, we bridge this gap by mapping the relationship between basic knit parameters and the fundamental TENG parameters which govern their electrical outputs. In this work, the loop length, yarn count, number of yarns per loop and the loop structure of a knitted textile TENG are empirically varied and its impact on the charge, current and voltage outputs is studied. The observed output trends are then analysed in-depth using the distance-dependent electric field theory, thus, explaining the root causes of the observed output trends. Consequently, several new strategies on the design and optimisation of more efficient knitted textile TENGs are uncovered. Further, the impact of these optimisation strategies on the wearable properties of the knitted textile TENGs is studied, paving the way for practically applicable textile TENG designs with balanced electrical output generation and long-term wearability.

A Novel Mechano-Synthesized Zeolitic Tetrazolate Framework for a High-Performance Triboelectric Nanogenerator and Self-Powered Selective Neurochemical Detection.

Designing a high-performing triboelectric novel material with eco-friendly, rapid, and cost-effective synthesis is the future of material research in triboelectric nanogenerators (TENG). We report a mechanochemical ball mill synthesis of a zeolitic tetrazolate framework (ZTF-8) that is isostructural with the well-known zeolitic imidazolate framework ZIF-8. ZTF-8 is extremely stable in water, 0.1 M aqueous acid/base solutions for 75 days at 25 °C, and boiling water (100 °C) for 7 days. Kelvin probe force microscopy and molecular electrostatic surface potential computational analysis exhibited that ZTF-8 has a very high positive surface potential. Atomic force microscopy and three-dimensional digital microscopy studies reveal the high roughness profile in the ZTF-8 film. The unique structure, exceptional acid/base stability, good dielectric property, and high roughness profile combined with the extremely electropositive nature of ZTF-8 make it a suitable candidate as a polymer-free triboelectric positive material in TENG with outstanding performance (power density of 720 mW/m2). High triboelectric output was further validated using the COMSOL Multiphysics simulation tool. Simple mechanical hand tapping of the ZTF-based TENG (ZTF-TENG) device generates high electric output, which was practically used to power numerous low-powered devices like tally counter, clinical thermometer, and digital clock and also illuminates 125 light-emitting diodes. In addition, the efficiency of ZTF-TENG was utilized as a self-powered device for a selective dopamine (DA) sensor with good sensitivity (377.76 mV/μM/cm2), wide range linearity (5-120 μM), and excellent limit of detection (0.42 μM).

Environmental Impact of Enhanced Geothermal Systems with Supercritical Carbon Dioxide: A Comparative Life Cycle Analysis of Polish and Norwegian Cases

Low-carbon electricity and heat production is essential for keeping the decarbonization targets and climate mitigation goals. Thus, an accurate understanding of the potential environmental impacts constitutes a key aspect not only for the reduction in greenhouse gas emissions but also for other environmental categories. Life cycle assessment allows us to conduct an overall evaluation of a given process or system through its whole lifetime across various environmental indicators. This study focused on construction, operation and maintenance, and end-of-life phases, which were analyzed based on the ReCiPe 2016 method. Within this work, authors assessed the environmental performance of one of the renewable energy sources—Enhanced Geothermal Systems, which utilize supercritical carbon dioxide as a working fluid to produce electricity and heat. Heat for the process is extracted from hot, dry rocks, typically located at depths of approximately 4–5 km, and requires appropriate stimulation to enable fluid flow. Consequently, drilling and site preparation entail significant energy and material inputs. This stage, based on conducted calculations, exhibits the highest global warming potential, with values between 5.2 and 30.1 kgCO2eq/MWhel, corresponding to approximately 65%, 86%, and 94% in terms of overall impacts for ecosystems, human health, and resources categories, respectively. Moreover, the study authors compared the EGS impacts for the Polish and Norwegian conditions. Obtained results indicated that due to much higher electricity output from the Norwegian plant, which is sited offshore, the environmental influence remains the lowest, at a level of 11.9 kgCO2eq/MWhel. Polish cases range between 38.7 and 54.1 kgCO2eq/MWhel of global warming potential in terms of electricity production. Regarding power generation only, the impacts in the case of the Norwegian facility are two to five times lower than for the installation in the Polish conditions.

Self-adhesive, conductive, and multifunctional hybrid hydrogel for flexible/wearable electronics based on triboelectric and piezoresistive sensor

Flexible electronics are highly developed nowadays in human-machine interfaces (HMI). However, challenges such as lack of flexibility, conductivity, and versatility always greatly hindered flexible electronics applications. In this work, a multifunctional hybrid hydrogel (H-hydrogel) was prepared by combining two kinds of 1D polymer chains (polyacrylamide and polydopamine) and two kinds of 2D nanosheets (Ti3C2Tx MXene and graphene oxide nanosheets) as quadruple crosslinkers. The introduced Ti3C2Tx MXene and graphene oxide nanosheets are bonded with the PAM and PDA polymer chains by hydrogen bonds. This unique crosslinking and stable structure endow the H-hydrogel with advantages such as good flexibility, electrical conductivity, self-adhesion, and mechanical robustness. The two kinds of nanosheets not only improved the mechanical strength and conductivity of the H-hydrogel, but also helped to form the double electric layers (DELs) between the nanosheets and the bulk-free water phase inside the H-hydrogel. When utilized as the electrode of a triboelectric nanogenerator (TENG), high electrical output performances were realized due to the dynamic balance of the DELs between the nanosheets and the H-hydrogel's inside water molecules. Moreover, flexible sensors, including triboelectric, and strain/pressure sensors, were achieved for human motion detection at low frequencies. This hydrogel is promising for HMI and e-skin.

Triboelectrically active hydrogel drives self-charging zinc-ion battery and human motion sensing

The fast advancement of flexible electronic technology hastens an ever-growing demand for power sources that are adaptable and flexible, and the arrival of innovative energy harvesting technologies such as triboelectric nanogenerator (TENG) further endow the potable electronics with versatility and sustainability. Herein, polyvinyl alcohol/ polyacrylamide/ zinc sulfate (PPZ) hydrogel was synthesized via an one-step UV-initiated polymerization. The hydrogel demonstrates exceptional tensile properties (with a large strain of 915 % and a corresponding tensile strength of 231 KPa), excellent electrical conductivity and light transmittance. A highly flexible and easily adaptable single-electrode TENG was thus fabricated on the base of the as-synthetized PPZ (PPZ-TENG), where the PPZ hydrogel functions as both the charging layer and current collector. While promoting a high electrical output performance of the PPZ-TENG (an open circuit voltage of 176 V and a power density of 328 mW/m2), the PPZ hydrogel also serves as an efficient ion-conductive electrolyte to construct highly flexible self-charging zinc ion batteries (ZIBs). Besides, highly sensitive strain response toward environmental stimuli was also demonstrated, which makes the integration strategy a promising solution for future development self-powered flexible wearable electronics toward the sustainable monitoring of human vital signs such as pulse and limb movement.