High Output Stability Research Articles

Wearable self-powered motion sensor based on biomass carbon-dots/polyvinyl alcohol film

The functionalized polymer with scalable properties presents a promising option for flexible triboelectric nanogenerators designed for detecting human motion. In this study, a novel method to fabricate tribopositive composite film was proposed by incorporating high permittivity N-doped orange peel-based carbon dots (O-CDs) into the highly cross-linked polyvinyl alcohol (PVA). The O-CDs/PVA sensor showed elevated electrical output with the raised content of O-CDs until 1.5 wt. % with a peak voltage of 3.5 V. The response characteristics under various external force conditions were tested, and the maximum peak voltage and current reached 3.92 V and 28.6 A under the force of 50 N. Moreover, O-CDs/PVA sensors present superior high-output stability, durability, and accurate distinction to different movement states, even the vocal cord vibration. By introducing the support vector machine learning algorithm, intelligent gesture recognition was achieved. This work paves a facile, feasible, and scalable pathway to the self-powered human motion sensor device.

Reduced graphene oxide/TiO2 hybrid synergistically enhanced polyimide nanofibers with high triboelectric output and thermal charge stability

The output performance of triboelectric nanogenerators (TENGs) can drop dramatically in high temperature environments because of the thermionic emission effect. To enhance the thermal charge stability and expand the working temperature of TENG, polyimide nanofibers (PINF) were synergistically enhanced by the electron trapping mechanism of reduced graphene oxide (rGO) and interfacial polarization of TiO2. With the multiple enhancement effect of polyimide/rGO/TiO2 composite nanofibers (PRTNF) on triboelectric output, PRTNF-TENG generated an open circuit voltage of 228.26 V and a short circuit current of 5.22 μA, which were 3.80 and 3.48 times higher than those of PINF-TENG. The effective output of polymer-based TENG was investigated from 25 − 300 °C. Compared to room temperature, the PRTNF-TENG can maintain 19.45 % (44.39 V) and 18.20 % (0.95 μA) of the voltage and current at 300 °C, respectively, and still drive 50 commercial LEDs. Furthermore, PRTNF-TENGs were applied as self-powered sensors for firefighters to provide real-time motion monitoring and ambient temperature detection. This PRTNF-TENG has broad application prospects for energy harvesting and smart electronic monitor in harsh environments such as fire and space.

Metal Hydrogel‐Based Integrated Wearable Biofuel Cell for Self‐Powered Epidermal Sweat Biomarker Monitoring

AbstractWearable sensors for continuous monitoring of biomarkers in body fluids have gained significant attention for their potential in disease diagnostics and health management, but lack sustainable power supply and advanced sensing strategies. Herein, sweat wearable biofuel cells (w‐BFCs) based on metal hydrogels are demonstrated with high output and outstanding stability, which harvest energy directly from human sweat and simultaneously enable self‐powered sensing of epidermal biomarkers. Experimental and computational results elucidate that the highly porous and flexible metal hydrogels exhibit superior electrocatalytic capabilities for oxidizing ascorbic acid (AA), a sweat metabolite at the anode, and reducing O2 at the cathode. Consequently, the assembled AA/O2 BFC delivers a high and stable power output, with a maximum output power density of 35 µW cm−2 at an ultralow AA concentration and long‐term stability over 30 days, and a self‐powered, sensitive sensing for AA detection. When applied to the skin of the volunteers, this integrated w‐BFC powers the biosensor using human sweat AA as fuel and allowing real‐time monitoring of AA sensing signal via smartphone. This work not only advances energy harvesting for wearable sensors but also paves new avenues for real‐time, online monitoring of epidermal sweat biomarkers.

Textured CsPbI3 nanorods composite fibers for stable high output piezoelectric energy harvester

The utilization of piezoelectric nanogenerator (PENG) based on halide perovskite materials has demonstrated significant promise for energy harvesting applications. However, the challenge of synthesizing halide perovskite materials with both high output performance and stability using a straightforward process persists as a substantial obstacle. Herein, we present the fabrication of CsPbI3 nanorods (NRs) exhibiting highly uniform orientation within polyvinylidene fluoride (PVDF) fibers through a simple texture engineering approach, marking the instance of enhancing PENG performance in this manner. The resultant composite fibers showcase a short-circuit current density (Isc) of 0.78 ​μA ​cm−2 and an open-circuit voltage (Voc) of 81 ​V, representing a 2.5 fold increase compared to the previously reported highest value achieved without the electric poling process. This outstanding output performance is ascribed to the orientation of CsPbI3 NRs facilitated by texture engineering and dipole poling via the self-polarization effect. Additionally, the PENG exhibits exceptional thermal and water stability, rendering it suitable for deployment in diverse and challenging environmental conditions. Our findings underscore the significant potential of textured CsPbI3 NRs composite fibers for powering low-power consumer electronics, including commercial LEDs and electronic watches.

Research on Power Balance Control Method of Electronic Transformer

Aiming at the problem of poor output stability and power gain of the power electronic transformer of the microgrid energy storage system, a power balance control method for the power electronic transformer of the microgrid energy storage system based on parallel modular multi-level commutation control is proposed. The reactive power outer loop parameter fusion method is used to sample the power dynamic load parameters and information fusion processing for the transformers in the system. According to the static limit active power adjustment of the fuzzy parameter factors on the output voltage side of the DC port, the steady-state gain of the power electronic transformer of the microgrid energy storage system is calculated. The static current limiting adjustment method is used to construct the feedback compensation model of the power electronic transformer of the microgrid energy storage system. In the active power control loop, the optimal design of the power electronic transformer power balance control of the microgrid energy storage system is realized through transient stable power adjustment. The test results show that using this method to perform power balance control on the power electronic transformer of the microgrid energy storage system has high output stability and good active power balance, which improves the robustness and adaptability of the transformer balance control.

A Wrinkle‐Enhanced Porous Poly(lactic Acid) Electret‐based Nanogenerator for Self‐powered Wireless Temperature Measurement Systems

AbstractRecently, electret‐based triboelectric nanogenerator (E‐TENG) showssignificant advantages for energy harvesting applications, including a largeelectric current and high output stability. Inthis investigation, porous biocompatible polylactide (PLA) film is prepared for E‐TENG applications. They found that thesurface potential of the porous PLA‐based bioelectret film is maintained at2.1 kV after 86 days of decay,. The measurement data from theE‐TENG‐based cantilever beam showed that the E‐TENG reached an open‐circuitvoltage (Voc) of 184 V and a short circuit current (Isc)of 22.4 µAat 13.8 Hz. Furthermore, the E‐TENG and the PVDF‐based piezoelectric nanogenerator (PENG) are combined to create a hybridNG for energy harvesting applications. The data indicate that the maximumoutput power of the hybrid NG reached 73.5 µWat 6 MΩ,which is 30.7% and 1.91‐fold higher than that of the PENG and the E‐TENG,respectively. The hybrid NG is used as a powersource to drive a wireless temperaturetransmission system, which can receive a temperature transmission signal from 20 m away. The advantages of biocompatibility,softness and ease of processing make the porous PLA film a great candidate forwearable devices applications.

Alpha-ray imaging with alkali copper halide scintillator

Internal exposure for decommissioning workers at the Fukushima Daiichi Nuclear Power Plant must be prevented, and we have developed a monitoring system for alpha-ray emitting dust (alpha dust). When the dust size is less than several tens of micrometers, a dust protection maskdoes not work effectively to prevent internal exposure. Since no devices have been operated to observe alpha-dust images in real-time up to now, we have developed an alpha-ray imaging detector consisting of a scintillation material and imaging detector. Scintillators are required to have high light output and chemical stability. Cs3Cu2I5 (CCI) scintillator was found to be one of the candidates, and an imaging test was operated with this material. The CCI crystal was grown by the Bridgman-Stockberger method, and a scintillation sheet for alpha-ray imaging was prepared by CCI microcrystals with a thickness of approximately 70 μm on a 200-μm thickness transparent polyethylene terephthalate film as a first imaging test. The sheet was irradiated with 5.5-MeV alpha rays from an 241Am source, and scintillation photons were detected with a CMOS camera through an optical lens. We succeeded in visualizing alpha rays, and a position resolution of our system achieved approximately 16.2 ± 2.6 μm (10–90 %). This resolution was similar value to other imaging devices with Ag:ZnS powder scintillator, and a CCI single crystal sheet was expected to reach better resolution.

Flexible regenerated cellulose/ZnO based piezoelectric composites fabricated via an efficient one-pot method to load high-volume ZnO with assistance of crosslinking

Flexible piezoelectric film has broad application in the energy devices and sensor field. Herein, a highly effective “one-pot method” was proposed to fabricate regenerated cellulose/ZnO piezoelectric composites, in which the preparation of regenerated cellulose (RC), in-suit polymerization of ZnO in RC and its cross linking can be carried out simultaneously. ZnO were in-situ synthesized from Zn2+ reduced by alkali from the dissolve system of cellulose. Simultaneously, the added zinc salt accompanied with acid degradation has promoted the dissolution of cellulose, existing a synergistic effect. In this synthetic process, ECH was used to crosslink cellulose molecules to obtain cross-linked regenerated cellulose (CRC), which enhanced regenerated cellulose framework for more uniform hydroxyl groups as growth sites, thereby further elevate growth content of piezoelectric ZnO distributed uniformly in the composite film. Consequently, the piezoelectric constant (d33) of the developed piezoelectric composite film with excellent tensile strength and flexibility reaches 26.8 ± 6.4 pC N−1. Without external high-voltage polarization, its piezoelectric output open-circuit voltage (VOC) and short-circuit current (ISC) was increased to 6.98 V and 610.27 nA. After polydimethylsiloxane (PDMS) was immersed in the CRC/ZnO aerogel to be CRC/ZnO/PDMS PENG, the piezoelectric output performance was further enlarged to be 10.02 V and 1032.57 nA, respectively, even with a high output stability. It can drive a LED and a small electronic screen, as well as has high sensitivity to pressure excitation, displaying high VOC and ISC up to 17 V and 1300 nA under the trampled state, respectively. The strategy has brought highly efficient assembly and high performance for the piezoelectric nanogenerator (PENG), directly providing a reference to other nanocellulose based PENG.

Fabrication of YAG ceramics surface without damage and grain boundary steps using catalyzed chemical wet etching

Achieving an atomically smooth surface without damage or grain boundary steps is crucial for yttrium aluminum garnet (YAG) ceramics to deliver high-power laser oscillation and stable output. We propose a wet etching method that utilizes a thin-film catalyst, enabling the topmost crystal grain to be selectively removed through a catalyzed chemical reaction. This study demonstrates the effectiveness of the proposed method by polishing Nd- and Yb-doped YAG ceramic substrates. We realized damage-free surfaces having steps with a height of less than 1.0 nm. Such surfaces can effectively deliver high-power laser oscillation with high output stability.

Improvement of the SOFC System by Anode Recirculation

SOFC can utilize a variety of carbon-containing fuels stably and efficiently. Many studies have proved that anode recirculation can effectively improve the system fuel utilization, enhancing the system's electrical efficiency and lowering operating costs. More precisely, anode recirculation takes high power output, high efficiency, and high stability into account at the system level, while these three indexes are contradictory at the SOFC stack level. In this study, multiple SOFC system process models were built with MATLAB, which involved four anode recirculation modes, namely, "conventional low recirculating rate" mode, "conventional high recirculating rate" mode, "recirculation with water gas shift reaction reactor" mode and "recirculation with adiabatic reformer" mode. These modes were compared under different operating conditions. The key parameters that affect the system performance include fuel flow rate, recirculation rate, current per cell, and reformer temperature. Finally, the measured data of industrial-size fuel cells were used to make verification. It is found that the "recirculation with adiabatic reformer" mode can achieve high electrical efficiency while maintaining SOFC stacks working at low fuel utilization conditions. In other words, high power output, high electrical efficiency, and high stability are achieved at the same time. Moreover, it also has considerable feasibility in terms of system thermal balance. This study can provide powerful guidance for SOFC system design and construction.

A shape-adaptable and highly resilient aerogel assembled by poly(vinylidene fluoride) nanofibers for self-powered sensing

Flexible piezoelectric nanogenerators with high power output and superior mechanical stability that can respond to tiny human movements are essential for the development of portable power sources and smart sensors. Herein, a poly(vinylidene fluoride) (PVDF) nanofiber aerogel with a bionic cytoplasmic matrix structure and controllable super-elasticity is constructed by wet electrospinning for self-powered sensing. The PVDF-based aerogel exhibits remarkable elastic resilience with a high compressive stress of 2 MPa at 50% strain. The three-dimensional porous structure and high specific surface area endow the aerogel excellent electrical properties. The corresponding PVPU-NG device has an optimum output of 156 V and 34.9 μA with a power density of 5.5 W m−2, which can illuminate 50 light-emitting diodes. In addition, this PVPU-NG can respond to tiny human movements and convert mechanical energy into electrical energy to power miniature electronics. Specifically, the PVPU-NG can generate peak-to-peak voltages of approximately 1.8 V and 31 V during elbow bending and walking, respectively. As a result, the PVDF-based nanofiber aerogel, which exhibits high compressive strength and improved pressure sensitivity, demonstrates broad application prospects in wearable electronics and portable power sources.

A triboelectric nanogenerator coupled with internal and external friction for gesture recognition based on EHD printing technology

Surface charge density is a critical factor in determining the output performance of triboelectric nanogenerators (TENGs). However, enhancing the surface charge density is a relatively complex process characterized by high cost, fast charge dissipation, and inferior stability. Herein, a TENG with internal and external friction synergistic coupling enhancement that employed an electrohydrodynamic (EHD) printing technique for gesture recognition was proposed. Under the external force, the electrical performance of the triboelectric material could be improved via internal friction formed by the contact between the lines of silver nanowires (AgNWs) mixing with hydroxy propyl methyl cellulose (HPMC) (AgNWs (HPMC)) inside the tribolayer and the PDMS with microgrooves. The effects of dielectric layer thickness, micropore size, the number of micropore arrays, as well as the AgNWs content and the number of AgNWs (HPMC) lines on TENG output performance were analysed systematically. When the micropore arrays TENG (MA-TENG) size was 15 mm × 15 mm, the thickness of a dielectric layer was 240 µm, the number of micropore arrays was 36, and the number of AgNWs (HPMC) lines was 28, the charge transfer quantum of MA-TENG was 34.9 nC, which is about 5.8 times that of flat TENG. The peak power of the MA-TENG was 580 μW, which was about 10 times than that of the flat TENG. Finally, a self-powered gesture recognition was demonstrated successfully based on the developed MA-TENG and revealed its potential in the field of human-computer interaction. This work not only proposed a new method with the advantages of a simple process, low cost, and high output stability, to significantly increase the surface charge density, but also provided a new scheme for electronic skin and wearable devices.

A Magnetically Controlled Current Transformer for Stable Energy Harvesting

The magnetically controlled current transformer (MCCT) is proposed to harvest stable energy from the magnetic field induced by the transmission-line fluctuating current. Compared with the conventional current transformer (CT), the advance of the proposed MCCT originates from the so-called constant magnetic flux control, which is achieved by connecting an electronic load on the secondary side of MCCT, and adjust the load impedance to make it equivalent to the corresponding resistive-capacitive impedance for magnetization or demagnetization. Furthermore, the working principle and the excitation characteristic of the MCCT system have been analyzed using the equivalent magnetic circuit and equivalent circuit methods. In addition, the details of the electronic load circuit and control system of the MCCT are presented in this paper, and the stability of the system is verified using logarithmic criterion and total harmonic current distortion (THDi) analysis. Finally, the co-simulation and experimental results show that MCCT can produce a stable output power of 13 W in the range of 50–500 A current fluctuations, demonstrating that the proposed magnetic energy harvester is capable of a high conversion efficiency and output stability.

Tuning the Functionalization of Graphite for Hydrovoltaic Power Generation

The recent discovery of hydrovoltaic devices for power generation has led to a rapid growth into new materials for harvesting energy specifically for this research field. Of the materials investigated, carbon materials have dominated, and graphene oxide (GO) has emerged as the leader. While graphite is conductive, it does not have functional groups to strongly interact with water, and highly functionalized GO forms strong interaction with water to generate necessary surface charges but does not typically have high conductivity. Herein, we report the fabrication and functionalization of a graphite-based structure, controlling the extent of oxidation to balance the effects of conductivity and functionalization to achieve high power outputs in hydrovoltaics. Devices prepared using the functionalized graphite achieve a power output of 53.3 μW/g. High power output and good film stability are key advances toward the practical application of hydrovoltaic devices for renewable energy.

A Robust Constant–Voltage DC Triboelectric Nanogenerator Using the Ternary Dielectric Triboelectrification Effect

AbstractNowadays, the development of direct current triboelectric nanogenerators (DC‐TENGs) is oriented toward practical applications such as real‐time efficient harvesting and supplying energy. This demands DC‐TENGs with a low loss factor, high energy utilization efficiency, device portability, and output stability. Herein, a constant‐voltage DC‐TENG (C‐DC‐TENG) with robust output performance, using the ternary dielectric triboelectrification effect is demonstrated, which gives a crest factor of 1.0082. The key to improving the output charge density is the number of subdivision units, a result of theoretical simulations and experiments of C‐DC‐TENG. The optimized C‐DC‐TENG achieves not only an output charge density of 3.902 mC m−2 per round but also an average power density of 8.77 W m−2 (3.508 W m−2 Hz−1), which both set a new record for the rotary DC‐TENG. Moreover, introducing soft polyester fur enables C‐DC‐TENG to maintain 100% output without wear after 800 000 cycles. This C‐DC‐TENG is faultlessly competent for powering 2784 LEDs in series and 25 parallel‐connected hygrothermographs continuously. This work provides a promising technique for large‐scale clean energy harvesting, accelerating the progress toward practical applications of DC‐TENG.

Liquid–Liquid Triboelectric Nanogenerator for Harvesting Distributed Energy

AbstractAs one of the most widely distributed water resources, rainwater contains tremendous energy that cannot be effectively utilized by the conventional electromagnetic generators. Triboelectric nanogenerators (TENGs) represent a distributed method to convert trivial mechanical energy into electricity based on contact electrification. Benefiting from the large and replenishable contact interfaces in liquid–liquid systems, liquid–liquid TENG further promises efficient charge transfer. However, the limited understanding of liquid–liquid contact electrification has restricted its development. In this study, the mechanisms of contact electrification in various liquid–liquid systems is comprehensively investigated and thus a liquid–liquid TENG with optimized materials and structures to harvest energy from rainwater is demonstrated. The proposed liquid–liquid TENG generates a high charge density (3.63 µC L−1) with high output stability (crest factor ≈1.1) and long effective contact electrification time. Based on the direct current characteristics, energy harvested from rainwater can be fed directly to electronic devices and a self‐powered rainfall sensor can also be implemented. This study highlights the promise of all‐liquid systems in distributed green energy and passive sensors, offering a new perspective on self‐powered devices.

Wideband Photonic Microwave Frequency Divider With Large Harmonic Suppression Capability

An all-optical photonic microwave frequency divider (PMFD) is presented. It is based on injecting an RF phase modulated optical signal into a semiconductor laser oscillating in the period-two state. New optical frequency components with frequency separation of half of the input RF signal frequency are generated at the laser output. A frequency divided signal can be obtained by the beating of these optical frequency components at a photodetector. Large harmonic suppression can be achieved by using an optical filter to select only two optical frequency components to be detected by the photodetector. The proposed PMFD is free of electrical components and does not suffer from the modulator bias drift problem. It has the potential to operate over a 100 GHz frequency range. System parameters required to realise divide-by-two frequency division operation for different input RF signal frequencies are investigated. Experimental results are presented for the novel PMFD, which demonstrate the generation of a 1/2 frequency component for different input RF signal frequencies by controlling the forward bias current of an off-the-shelf semiconductor laser, and which also show the important advantages of large harmonic suppression and high signal-to-noise ratio performance. Wide input RF signal power range and high output stability performance are also demonstrated experimentally.

High-performance hybrid biofuel cells using amphiphilic assembly based enzyme electrodes

Biofuel cells, which convert chemical energy into electrical energy at mild temperature and over moderate pH ranges, have been considered some of the most promising candidates for powering biomedical devices. However, most biofuel cells provide low power output and short-term operational stability due to their poor electron transfer. To address these issues, we use a unique amphiphilic assembly method to generate hybrid biofuel cells with high power output and good operational stability. This approach can induce favorable interfacial interactions between electrocatalysts and significantly improve the electron transfer kinetics of electrodes. In this study, glucose oxidase (in aqueous media) is repeatedly assembled with hydrophobic metal nanoparticles (in nonpolar media) on a conductive textile. The formed biofuel cell exhibits remarkably high power output (7.3 mW cm−2) and good operational durability. We believe that our assembly approach can provide a basis for preparing a variety of high-performance bioelectrochemical devices, including biofuel cells.

Spheres Multiple Physical Network-Based Triboelectric Materials for Self-Powered Contactless Sensing.

Non-contact mode triboelectric nanogenerators effectively avoid physical contact between two triboelectric materials and achieve long-term reliable operation, providing broad application prospects in the field of self-powered sensing. However, the low surface charge density of triboelectric materials restricts application of contactless sensing. Herein, by controlling Rayleigh Instability deformation of the spinning jet and vapor-induced phase separation during electrostatic spinning, a polyvinylidene fluoride@Mxene (Ti3 C2 Tx ) composite film with spheres multiple physical network structures is prepared and utilized as the triboelectric material of a self-powered contactless sensor. The structure of the composite film and high conductivity of Ti3 C2 Tx provide triboelectric materials with high output performance (charge output and power output up to 128 µC m-2 and 200 µW cm-2 at 2Hz) and high output stability. The self-powered contactless sensor shows excellent speed sensitivity (1.175 Vs m-1 ). Additionally, it could accurately identify the motion states such as running (55mV), jumping (105mV), and walking (40mV) within the range of 70cm, and present the signals in different pop forms. This work lays a solid foundation for the development and application of high-performance triboelectric materials, and has guiding significance for the research of self-powered contactless sensing.

A Novel Approach on the Advancement in Polymer Phase Change Material in Solar Energy

A wide interest has been shown in the application of solar energy in recent times. This motivated the researchers to make a development in the approach of solar energy, but there are different technologies like MPPT, CPG, and grid mode that have been used to maintain a constant temperature. Among these, phase change material has been used to regulate the temperature in the system. Solar energy is becoming an essential approach for increasing the efficiency of thermal energy conversion and utilizing polymeric step change composites, which have attracted extremely large interest in recent years due to their advantages of high energy density and powerful energy output stability. A plethora of reviews and reports have been published to compile the diverse range of PCMs made available for various applications. PCMs are created by improving thermophysical thermodynamic stability, latent heat, and heat capacity. Furthermore, the possible applications of polymer phase PCMs in a variety of fields, such as energy storage devices, thermal corrective action, and temperature-controlled drug carriers, are detailed. In this paper, a novel approach on the advancement of nanoconfined phase change material is defined along with the application of the solar energy system.