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This paper presents the novel use of a sonochemical reaction product as a sensing material in self-powered ultrasonic reactor devices for determination of ultrasound parameters. A piezoelectric nanogenerator was fabricated via sonochemical synthesis of SbSeI nanowires compressed into a bulk sample. The prepared device was used to develop two fast and simple evaluation methods for acoustic power in liquid. A calibration procedure was carried out for both methods using a VCX-750 ultrasonic processor. The ultrasound acoustic power was varied within a 150 W to 750 W range and the corresponding nanogenerator electrical responses were measured. The voltage signals of the first method fit the best with theoretical dependence. The second technique was based on the application of the Fast Fourier Transform (FFT) to the measured electric output. The results of these two approaches were convergent. Acoustic power values of 255(8) W and 222(7) W were determined for the Sonic-6 reactor using theoretical dependence fitting to experimental data and FFT analysis, respectively. Developed sensing technology possesses great potential for sonochemistry applications.

A rapid development in personal electronics has raised challenging requirements for portable and sustainable power sources. For example, in wearable technologies, the concept of wearable body area network brings body motion and vital signs monitoring together in synergy. For this, a key aspect is sustainable portable energy, available anywhere, at any time, as generated by triboelectric nanogenerators (TENG). This technology usually demands high-cost processes and materials and still suffer from low power output, as well as unstable output values due to charge generating stimulus with variable intensities. In this work, we present TENGs using shear exfoliated graphene as electrodes as well as active triboelectric layer deposited by a simple solution process. Graphene in combination with polymers such as polydimethylsiloxane (PDMS) were used to produce TENG devices using low-cost solution processing methods. Device electrical power generation was tested with a cyclic physical stimulus for better control and understanding of device output. The triboelectric response of these materials showed open circuit voltages (Voc) and short-circuit currents (Isc)of approximately 233 V and 731 nA respectively when stimulated at 1.5 Hz. A power density of 13.14 μW/cm2 under a load of 200 MΩ was achieved, which can be 40 times higher when compared to devices made with aluminum and PDMS. These results demonstrate the potential of solution process for low-cost triboelectric devices for self-sustainable wearable portable nanogenerators on health and security applications using contact and positional sensors.

The organic piezoelectric polymer polyvinylidene fluoride (PVDF) has attracted extensive research because of its excellent flexibility and mechanical energy-harvesting properties. Here, the electrospinning technique was taken to fabricate synthesized fiber membranes of a PVDF/cellulose acetate (CA) composite. The obtained PVDF/CA electrospun fiber membranes (EFMs) were employed to prepare a flexible nanogenerator. XRD and FTIR spectroscopy revealed the enhancement of piezoelectric behavior due to an increase in β-phase in PVDF/CA EFMs compared with cast films. The PVDF/CA fibers (mass ratio of PVDF to CA = 9:1) showed an output voltage of 7.5 V and a short-circuit current of 2.1 μA under mechanical stress of 2 N and frequency of 1 Hz, which were 2.5 and two times greater than those of the pure PVDF fibers, respectively. By charging a 4.7 µF capacitor for 15 min with the voltage generated by the PVDF/CA EFMs, nine LED lamps could be lit. The work provides an effective approach to enhancing the piezoelectric effects of PVDF for low-power electronic loading of macromolecule polymers.

Here, we report the successful incorporation of group I elements (K, Na, Li) to ZnO nanowires. Three distinct (2, 4, and 6 wt.%) doping concentrations of group I elements have been used to generate high piezoelectric voltage by employing a vertically integrated nanowire generator (VING) structure. X-ray photoelectron spectra (XPS) indicated the seepage of dopants in ZnO nanowires by substitution of Zn. Shallow acceptor levels (LiZn, NaZn, KZn) worked as electron trapping centers for intrinsically n-type ZnO nanowires. Free moving electrons caused a leakage current through the nanowires and depleted their piezoelectric potential. Reverse leakage current is a negative factor for piezoelectric nanogenerators. A reduction in reverse leakage current signifies the rise in output voltage. A gradual rise in output voltage has been witnessed which was in accordance with various doping concentrations. K-doped ZnO nanowires have generated voltages of 0.85 V, 1.48 V, and 1.95 V. For Na-doped ZnO nanowires, the voltages were 1.23 V, 1.73 V, and 2.34 V and the voltages yeilded for Li-doped ZnO nanowires were 1.87 V, 2.63 V, and 3.54 V, respectively. Maximum voltage range has been further enhanced by the surface enrichment (oxidized with O2 molecules) of ZnO nanowires. Technique has been opted to mitigate the screening effect during an external stress. After 5 h of oxidation in a sealed chamber at 100 ppm, maximum voltage peaks were pronounced to 2.48 V, 3.19 V, and 4.57 V for K, Na, and Li, respectively. A low-cost, high performance mechanical transducer is proposed for self-powered devices.

Abstract In the dawn of energy crisis and rising challenges in powering distributed low energy portable devices, nanogenerators, a class of mechanical energy harvesters is gaining increasing interest in fundamental research and commercial applications. Nanogenerators harvest energy by transducing mechanical energy into electric energy, the performance is highly related to the mechanical and electrical properties of the materials and devices. A typical nanogenerator consists of a substrate, a functional triboelectric active layer, electrode, and separator, which overall built‐up a three dimensional (3D) structure. 3D printing with its ability to form complex 3D structures possess coveted advantages in the development of nanogenerators. In this review, we introduce the importance of 3D structures for nanogenerators and explicitly discuss the different 3D printing methods and the ink formulation to tackle the challenges in 3D structured nanogenerators. Additionally, the principle and application of 4D printing in nanogenerator fabrication are critically highlighted.

Electrostimulation has been recognized as a promising nonpharmacological treatment in orthopedics to promote bone fracture healing. However, clinical applications have been largely limited by the complexity of equipment operation and stimulation implementation. Here, we present a self-powered implantable and bioresorbable bone fracture electrostimulation device, which consists of a triboelectric nanogenerator for electricity generation and a pair of dressing electrodes for applying electrostimulations directly toward the fracture. The device can be attached to irregular tissue surfaces and provide biphasic electric pulses in response to nearby body movements. We demonstrated the operation of this device on rats and achieved effective bone fracture healing in as short as 6 wk versus the controls for more than 10 wk to reach the same healing result. The optimized electrical field could activate relevant growth factors to regulate bone microenvironment for promoting bone formation and bone remodeling to accelerate bone regeneration and maturation, with statistically significant 27%and 83%improvement over the control groups in mineral density and flexural strength, respectively. This work provided an effective implantable fracture therapy device that is self-responsive, battery free, and requires no surgical removal after fulfilling the biomedical intervention. [ABSTRACT FROM AUTHOR]

The mechanisms of electrification of various solids in contact or friction, as well as in the interaction of liquid media with conductive and dielectric materials, are described and analyzed. The output characteristics of nanogenerators based on the phenomenon of electrification of solids and liquids are considered. The design and the study results of an electrostatic nanogenerator based on the electrification of a glass porous structure when a dielectric fluid passes through it are presented. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric nanogenerators for energy harvesting are getting more and more attention nowadays by converting the mechanical energy to electric energy. Here, an environment-friendly piezoelectric nanogenerator based on the regenerated cellulose (RC)/MoS2 nanosheet nanocomposite successfully exhibited a relative high output voltage of 2 V and current of 150 nA under slight press which were 5 and 7.5 times higher than those of the neat RC film, i.e. 0.4 V and 20 nA, respectively. In particular, the MoS2 nanosheets were obtained through a simple, facile and low-cost pathway by mechanical exfoliation in triethanolamine. The nanocomposite film with MoS2 nanosheets content of 4% exhibited a high piezoelectric constant (d33) of 19 pC/N, which was 6.3 times higher than that of the neat RC film (i.e. 3 pC/N). Thus, the RC/MoS2 piezoelectric nanogenerator has great potential applications in the fields of energy harvester, sensors and is of great significance to environment protection. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present work, the triboelectric phenomenon is explored in the ferroelectric polymer (ZnO‐PVDF film) surface when water drops fall on it. Using Kelvin probe force microscopy (KPFM), it is found that negative charges are generated on the surface of the film as the water drop comes into contact with the ZnO‐PVDF film, and the induced charges are found to stay on the surface for about 5 min. It is also observed that when subsequent water drops fall on the polymer surface, the charge remains almost constant. Based on the KPFM results, a mechanism for electricity generation in liquid–solid interface triboelectric nanogenerator (LSTENG) is proposed. An LSTENG has been fabricated using ZnO‐PVDF film, which shows an open‐circuit voltage of ≈1.3V and a short circuit current of ≈0.34 µA. The electrical characteristics of the LSTENG device agree with the proposed mechanism. [ABSTRACT FROM AUTHOR]

Summary: With the growing demand for wearable electronic devices, triboelectric nanogenerators (TENGs) provide an effective solution by harvesting human body motions and converting them into electricity. Tribomaterial is one key element for the output performance and application of TENGs. In this study, biomaterial eggshell membrane (ESM) was investigated for use as a piezoelectric‐enhanced positive tribomaterial. ESM not only exhibits excellent piezoelectricity due to the amount of hydrogen bonds, but it is also biocompatible and pollution free. The piezoelectricities of raw eggshell membrane (RESM), heated eggshell membrane (HESM), and carbonized eggshell membrane (CESM) were analyzed and compared. Porous expanded polytetrafluoroethylene (ePTFE) was fabricated and used as a negative tribomaterial in the TENG due to its strong electron‐acquisition ability. Pairing ESM with an ePTFE resulted in a novel piezoelectric‐enhanced triboelectric bio‐nanogenerator (P‐TENG) with an excellent energy harvesting ability, high‐efficiency output performance, and sensitive human motion monitoring. By comparing ePTFE paired with RESM, HESM, and CESM, the CESM/ePTFE P‐TENG showed the best output performance due to CESM's piezoelectric enhancement. This bio‐P‐TENG as a wearable electric device has great potential in biomedical applications. [ABSTRACT FROM AUTHOR]

A highly potential PVDF/BSZT/MWCNT nanocomposite based nanogenerator (PENG) capable of harvesting mechanical energy and generating electricity. [Display omitted] • A robust flexible BSZT/ MWCNT/PVDF nanocomposite was developed by solution casting. • The nanocomposite displayed remarkably high mechanical properties, energy storage density and dielectric permittivity (ε). • The tensile strength and Young's modulus were increased by 144% and 71.3%, respectively as compared to the neat PVDF film. • Fabricating a nanogenerator with this nanocomposite yielded a voltage of 25.7 V, current of 1.86 μA and power density of 4.4 μW/cm2. Recently, polymer composite-based capacitors have gained an overwhelming interest in advanced power systems due to their lightweight, flexible nature, high dielectric permittivity, strong thermal stability, and good energy storage density. However, the energy storage capacity remains insufficient for practical applications. This paper reports a robust PVDF/Ba 0.7 Sr 0.3 Zr 0.02 Ti 0.98 O 3 (f-BSZT)/f 1 -MWCNTs nanocomposite with high energy storage density, energy storage efficiency (η), stable dielectric permittivity (ε) and piezoelectric response using a simple solution casting process. The composite was designed in such a way it holds a 204 % increment (14 J/cm3) in energy storage density compared to the pristine PVDF (4.6 J/cm3). The energy storage efficiency (η) was measured at 89.6 % at a breakdown strength of 2000 kV/cm and a stable dielectric permittivity (ε) of approximately 41.5 at 100 Hz. When evaluating the composite's strength, an incredible increase in tensile strength (144%) and Youngs's Modulus (71.3%) was achieved. This remarkable property enhancement is attributed to superb filler dispersion and filler-matrix interfacial bonding achieved through selective surface functionalization of the fillers. Upon fabricating a nanogenerator with this nanocomposite, the device exhibited an electrical output of 25.7 V and 1.86 μA, surpassing many contemporary results. The device also showed outstanding sensitivity and performance under various biomechanical forces, making it a promising futuristic material for self-powered energy harvesting devices. [ABSTRACT FROM AUTHOR]

• Enhancing the electrical output performance of a composite piezoelectric nanogenerator based on BCZT/MCNTs/PDMS through triboelectric hybridization. • The piezo-triboelectric nanogenerator, based on the BCZT/MCNTs/PDMS composite, demonstrated optimal electrical output performance at a 50 wt%-BCZT ratio (V OC ∼ 39.7 V, I SC ∼ 1.9 µA, peak-to-peak power of ∼ 157.7 µW, and power density of ∼ 9.85 µW/cm2) under a compressive load force of 500 N and a frequency of 1 Hz. • The piezo-triboelectric nanogenerator device exhibits promising potential for energy harvesting under high compressive loading at low frequencies. This work has developed a novel piezo-tribo-electric nanogenerator (P-TENG) that is capable of converting mechanical energy into electrical energy when operating in compressive mode. An arch-shaped P-TENG device was formed using an optimal piezoelectric polymer composite, which was fabricated using a polydimethylsiloxane (PDMS) matrix that was modified with piezoelectric (Ba 0.85 Ca 0.15) (Ti 0.90 Zr 0.10)O 3 (BCZT) ceramic particles and electrically conductive multi-walled carbon nanotubes (MCNTs). A high filler loading of BCZT (40, 50, 60 wt%) and 3 wt% of MCNTs was formed into a 0–3 connectivity composite. The P-TENG device containing 50 wt% BCZT exhibited the highest electrical output (V OC ∼ 39.7 V, I SC ∼ 1.9 µA, and maximum power ∼ 157.7 µW), compared to the other composites, when subjected to an alternating compressive load of 500 N at a 1 Hz frequency. This research provides new composite formulations for elastomeric-based energy generators that are responsive to low frequency mechanical oscillations. [Display omitted] [ABSTRACT FROM AUTHOR]

The microfluidic system provides a novel method for simultaneously carrying out microfluidic manipulation, detection and analyzation in a tiny chip with designed microchannels, which has the advantage of simple structure and low sample consumption and has been widely studied in past decades. However, the normal operation of the microfluidic system could not be separated from the role of ancillary equipment which is often bulky, high-cost, and needs an external power supply. To improve the portability and simplify the structure of microfluidic systems, different types of nanogenerators (NGs) with advantages of small dimensions, simple structure, low cost and eco-friendly were integrated with microfluidic chips, and various self-powered microfluidic systems with distinctive functions have been developed. In this review, the recent research progress of NG-based self-powered microfluidic systems was summarized and discussed from two aspects: triboelectric generator (TENG) based self-powered microfluidic manipulation system and NG based self-powered microfluidic sensing system. Furthermore, the remaining challenges and future optimizing direction of NG-based self-powered microfluidic systems were also elaborated. [Display omitted] • A comprehensive review of different self-powered microfluidic systems based on nanogenerators (NGs). • The NG-based microfluidic systems are classified into self-powered microfluidic manipulation and sensing system. • Remaining challenges, and future optimizing direction of NG-based self-powered microfluidic systems are discussed. [ABSTRACT FROM AUTHOR]

• The basic principles of acoustic physics are discussed. • The typical ultrasonic response TENG and PENG designs and materials are summarized. • The structural design scheme of flexible photoelectric device is summarized. • The biomedical applications of the devices are classified and discussed. This paper provides a comprehensive review on the acoustoelectric materials and devices in biomedicine. Prominent development has been achieved in minimally invasive medicine and high-efficacy medical treatment. Nevertheless, substantial challenges persist, encompassing sustainable power provisioning, effective drug administration, tissue regeneration, and real-time monitoring. From a foundational and material design perspective, this paper delves into the distinctive contributions and inventive solutions offered by ultrasound technology in tackling these pivotal concerns. It first discusses the fundamentals of ultrasound physics, followed by the typical ultrasound responsive TENG and PENG designs and materials. Structural design plots for flexible aoustoelectric device are then summarized. The biomedical applications of these devices are categorized and discussed. The review article furnishes a systematic documentation and timely examination of the latest advancements in relevant research fields of biomedical acoustoelectric mateirals & devices. The paper concludes with an assessment of current challenges and prospects in the field, with a view to further enhancing the precision, specificity, and system-level integration of personalized healthcare. [ABSTRACT FROM AUTHOR]

Abstract Polytetrafluoroethylene (PTFE) is a fascinating electret material widely used for energy harvesting and sensing, and an enhancement in the performance could be expected by reducing its size into nanoscale because of a higher surface charge density attained. Hence, the present study demonstrates the use of nanofibrous PTFE for high-performance self-powered wearable sensors. The nanofibrous PTFE is fabricated by electrospinning with a suspension of PTFE particles in dilute polyethylene oxide (PEO) aqueous solution, followed by a thermal treatment at 350 °C to remove the PEO component from the electrospun PTFE-PEO nanofibers. The obtained PTFE nanofibrous membrane exhibits good air permeability with pressure drop comparable to face masks, excellent mechanical property with tensile strength of 3.8 MPa, and stable surface potential of − 270 V. By simply sandwiching the PTFE nanofibrous membrane into two pieces of conducting carbon clothes, a breathable, flexible, and high-performance nanogenerator (NG) device with a peak power of 56.25 μW is constructed. Remarkably, this NG device can be directly used as a wearable self-powered sensor for detecting body motion and physiological signals. Small elbow joint bending of 30°, the rhythm of respiration, and typical cardiac cycle are clearly recorded by the output waveform of the NG device. This study demonstrates the use of electrospun PTFE nanofibrous membrane for the construction of high-performance self-powered wearable sensors.

Abstract One significant challenge for electronic devices is that the energy storage devices are unable to provide sufficient energy for continuous and long-time operation, leading to frequent recharging or inconvenient battery replacement. To satisfy the needs of next-generation electronic devices for sustainable working, conspicuous progress has been achieved regarding the development for nanogenerator-based self-charging energy storage devices. Herein, the development of the self-charging energy storage devices is summarized. Focus will be on preparation of nanomaterials for Li-ion batteries and supercapacitors, structural design of the nanogenerator-based self-charging energy storage devices, performance testing, and potential applications. Moreover, the challenges and perspectives regarding self-charging energy storage devices are also discussed.

Recently, self-powered health monitoring systems using a wearable thermoelectric generator (WTEG) have been rapidly developed since no battery is needed for continuous signal monitoring, and there is no need to worry about battery leakage. However, the existing materials and devices have limitations in rigid form factors and small-scale manufacturing. Moreover, the conventional bulky WTEG is not compatible with soft and deformable tissues, including human skins or internal organs. These limitations restrict the WTEG from stabilizing the thermoelectric gradient that is necessary to harvest the maximum body heat and generate valuable electrical energy. This paper summarizes recent advances in soft, flexible materials and device designs to overcome the existing challenges. Specifically, we discuss various organic and inorganic thermoelectric materials with their properties for manufacturing flexible devices. In addition, this review discusses energy budgets required for effective integration of WTEGs with wearable biomedical systems, which is the main contribution of this article compared to previous articles. Lastly, the key challenges of the existing WTEGs are discussed, followed by describing future perspectives for self-powered health monitoring systems.

In recent years, nanogenerator technology has developed rapidly with the rise of cloud computing, artificial intelligence, and other fields. Therefore, the quick identification of the evolutionary path of nanogenerator technology from a large amount of data attracts much attention. It is of great significance in grasping technical trends and analyzing technical areas of interest. However, there are some limitations in previous studies. On the one hand, previous research on technological evolution has generally utilized bibliometrics, patent analysis, and citations between patents and papers, ignoring the rich semantic information contained therein; on the other hand, its evolution analysis perspective is single, and it is difficult to obtain accurate results. Therefore, this paper proposes a new framework based on the methods of Sentence-BERT and phrase mining, using multi-source data, such as papers and patents, to unveil the evolutionary path of nanogenerator technology. Firstly, using text vectorization, clustering algorithms, and the phrase mining method, current technical themes of significant interest to researchers can be obtained. Next, this paper correlates the multi-source fusion themes through semantic similarity calculation and demonstrates the multi-dimensional technology evolutionary path by using the “theme river map”. Finally, this paper presents an evolution analysis from the perspective of frontier research and technology research, so as to discover the development focus of nanogenerators and predict the future application prospects of nanogenerator technology.

A neuromorphic computing chip that can imitate the human brain’s ability to process multiple types of data simultaneously could fundamentally innovate and improve the von-neumann computer architecture, which has been criticized. Memristive devices are among the best hardware units for building neuromorphic intelligence systems due to the fact that they operate at an inherent low voltage, use multi-bit storage, and are cost-effective to manufacture. However, as a passive device, the memristor cell needs external energy to operate, resulting in high power consumption and complicated circuit structure. Recently, an emerging self-powered memristive system, which mainly consists of a memristor and an electric nanogenerator, had the potential to perfectly solve the above problems. It has attracted great interest due to the advantages of its power-free operations. In this review, we give a systematic description of self-powered memristive systems from storage to neuromorphic computing. The review also proves a perspective on the application of artificial intelligence with the self-powered memristive system.

The increasing interest in harvesting mechanical energy from day-to-day activities is gaining huge interest among researchers. We have fabricated a triboelectric nanogenerator (TENG) made of aluminum and PDMS film acting as positive and negative triboelectric layers. The layers are arranged in an arc-shaped structure with an air gap of 1 cm between the layers of the device. The PDMS layer is made by blending the polymer solution with the hardener in an appropriate ratio and dried to make the transparent and flexible polymer film. The device shows a maximum electrical response of 110 V and 260 nA voltage and current with the power density of 2.9 mW/m2 at 100 MΩ load resistance. Further, the device has been used for lighting green LEDs and charging commercial capacitors. An Arduino board was connected with LED and buzzer, which was triggered by the TENG device. This shows that with the proper usage of electronic components TENG can be used for self-powered sensors and with IoT applications. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Processing of Materials / Elektronnaya Obrabotka Materialov is the property of Institute of Applied Physics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A neuromorphic computing chip that can imitate the human brain's ability to process multiple types of data simultaneously could fundamentally innovate and improve the von-neumann computer architecture, which has been criticized. Memristive devices are among the best hardware units for building neuromorphic intelligence systems due to the fact that they operate at an inherent low voltage, use multi-bit storage, and are cost-effective to manufacture. However, as a passive device, the memristor cell needs external energy to operate, resulting in high power consumption and complicated circuit structure. Recently, an emerging self-powered memristive system, which mainly consists of a memristor and an electric nanogenerator, had the potential to perfectly solve the above problems. It has attracted great interest due to the advantages of its power-free operations. In this review, we give a systematic description of self-powered memristive systems from storage to neuromorphic computing. The review also proves a perspective on the application of artificial intelligence with the self-powered memristive system. [ABSTRACT FROM AUTHOR]

Summary: Despite the low cost, high power, and wide application areas, impact‐type triboelectric generators exhibit limited applicability due to the extremely short current duration, on the order of a millisecond. The high power, short lasting current peak not only results in reduced time‐averaged power output but also acts as triboelectric shock to the accompanying circuits, quickly degrading the usability of the generator. Here, we demonstrate tunable triboelectric current duration via controlling the air gap capacitance inserted between the two dielectric plates. In typical contact‐type triboelectric generator with nylon/air gap/Polydimethylsiloxane (PDMS) multilayers, decreasing the vertical speed of the dielectric plates from 0.5 cm/s to 0.05 cm/s result in increased current duration from 0.10 second to 0.81 second. The increased peak duration accompanies decreased peak current, resulting in the optimal charge density of 0.163 nC/cm2 at the vertical speed of 0.25 cm/s. Changing the air gap capacitance in noncontact mode or the relative permittivity in dielectric layers also results in similar change in peak duration. To explain the tunable current duration, an equivalent circuit model is constructed via serially connected capacitors and numerical solutions reproduce the trends in current duration associated with change in air gap capacitance. This study provides significant implications toward further optimizing triboelectric generators, in terms of optimal triboelectric charge density, accompanying circuit lifetime and broadened applicability. [ABSTRACT FROM AUTHOR]

As an emerging nano energy technology, nanogenerators have been developed rapidly, which makes it crucial to analyze the evolutionary pathways of advanced technology in this field to help estimate the development trend and direction. However, some limitations existed in previous studies. On the one hand, previous studies generally made use of the explicit correlation of data such as citation and cooperation between patents and papers, which ignored the rich semantic information contained in them. On the other hand, the progressive evolutionary process from scientific grants to academic papers and then to patents was not considered. Therefore, this paper proposes a novel framework based on a separated three-layer knowledge graph with several time slices using grant data, paper data, and patent data. Firstly, by the representation learning method and clustering algorithm, several clusters representing specific technologies in different layers and different time slices can be obtained. Then, by calculating the similarity between clusters of different layers, the evolutionary pathways of advanced technology from grants to papers and then to patents is drawn. Finally, this paper monitors the pathways of some developed technologies, which evolve from grants to papers and then to patents, and finds some emerging technologies under research.

Constructing hybrid nanogenerators (NGs) based on triboelectric effect and piezoelectric effect can combine the merits of the individual type of NG thus have drawn great attention in flexible wearable electronics. Herein, we prepared flexible BiFeO 3 (BFO) film in a simple and cost-effective way, which was used to fabricate a wearable hybrid piezoelectric-triboelectric nanogenerator (H–P/TENG) with silk fiber. By optimizing the experimental conditions, the highest open-circuit voltage of 110 V and short-circuit current density of 3.67 μA/cm2 were achieved under 1 Hz contact-separation movement. The device also showed the best output power density of 151.42 μW/cm2 with load resistance of 250 MΩ. Stimulating by moving body, the fabricated H–P/TENG successively realized the harvest and conversion of mechanical energy into electric energy, demonstrating great potential to monitor posture and establish a self-powered system. Moreover, the proposed H–P/TENG exhibited great stable output after 1800 contact-separation cycles, indicating the outstanding structure stability and fatigue resistance. This work will provide not only a facile and viable way to realize the application of ferroelectric materials in H–P/TENG but also new opportunities for developing monitor posture and self-powered systems. [ABSTRACT FROM AUTHOR]

The decay rate of charge in the friction layer is one of the key factors affecting the output performance of triboelectric nanogenerators (TENG). Reducing the decay rate of the triboelectric charge can increase the charge-carrying capacity of the friction layer and improve the output current and voltage of the TENG. This makes a friction generator more suitable for discontinuous driving environments. In contrast, increasing the decay rate of the charge in the friction layer can greatly improve the recovery time of the device, although it reduces the output performance of the generator. This is conducive to the application of friction generator in the field of sensors. In this study, polystyrene (PS) and carbon nanotubes (CNTs) were added to polyvinylidene fluoride (PVDF) nanofibers to adjust the charge decay time in the friction layer, thereby regulating the output performance of the friction generator and sensor. When the amount of added PS in the PVDF nanofiber reached 20%, the charge density on the friction surface increased by 1.9 times, and the charge decay time decreased by 64 times; when 0.1 wt% CNTs were added in the PVDF nanofiber, the charge decay time increased by more than 10 times. The former is more conducive to improving the power generation performance of the TENG, and the latter significantly improves the stability and repeatability of TENG-based sensors., (© 2024 IOP Publishing Ltd.)

In this study, germanium arsenide (GeAs) is investigated as a promising nanomaterial for application in triboelectric nanogenerators and green energy harvesting. The mechanical and electrical properties of mechanically exfoliated GeAs on silica substrates are evaluated through friction force microscopy and Kelvin probe force microscopy, respectively. First, it is observed that the surface potential/work function of GeAs varied with thickness. Second, thickness-dependent friction on GeAs films is found. However, the variation of friction with GeAs thickness followed an inverse trend typically observed for most other 2D material systems: larger friction is measured on thicker GeAs films. The higher friction is attributed to the higher surface potential of thicker GeAs, resulting from the accumulation of electrons on the GeAs surface that also resulted in higher adhesion between GeAs surface and the tip. Finally, history-dependent friction is observed and resulted from a continual increase in the friction force as the surface is scanned and originated from the triboelectrification of the surface. The dynamic triboelectrification behavior of thick GeAs during the scanning process is further verified and visualized by a serial experiment, where the GeAs is tribo-electrified through scanning and gradually de-electrified/discharged upon ceasing the scan., (© 2023 The Authors. Small published by Wiley‐VCH GmbH.)

To date, transforming environmental energy into electricity through a non-mechanical way is challenging. Herein, a series of photomechaelectric (PME) polyurethanes containing azobenzene-based photoisomer units and ionic liquid-based dipole units are synthesized, and corresponding PME nanogenerators (PME-NGs) to harvest electricity are fabricated. The dependence of the output performance of PME-NGs on the structure of the polyurethane is evaluated. The results show that the UV light energy can directly transduce into alternating-current (AC) electricity by PME-NGs via a non-mechanical way. The optimal open-circuit voltage and short-circuit current of PME-NGs under UV illumination reach 17.4 V and 696 µA, respectively. After rectification, the AC electricity can be further transformed into direct-current (DC) electricity and stored in a capacitor to serve as a power system to actuate typical microelectronics. The output performance of PME-NGs is closely related to the hard segment content of the PME polyurethane and the radius of counter anions in the dipole units. Kelvin probe force microscopy is used to confirm the existence of the PME effect and the detailed mechanism about the generation of AC electricity in PME-NGs is proposed, referring to the back and forth drift of induced electrons on the two electrodes in contact with the PME polyurethanes., (© 2023 Wiley‐VCH GmbH.)

Wearable electronics are an essential direction for the future development of smart wearables. Among them, the battery life of wearable electronics is a key technology that limits their development. The proposal of self-powered wearable electronics (SWE) provides a promising solution to the problem of long-term stable working of wearable electronics. This review has made a comprehensive summary and analysis of recent advances on SWE from the perspectives of energy, materials, and ergonomics methods. At the same time, some representative research work was introduced in detail. SWE can be divided into energy type SWE and sensor type SWE according to their working types. Both types of SWE are broadly applied in human–machine interaction, motion information monitoring, diagnostics, and therapy systems. Finally, this article summarizes the existing bottlenecks of SWE, and predicts the future development direction of SWE.

For the first time, a composite of ferroelectric antimony sulfoiodide (SbSI) nanowires and non-ferroelectric titanium dioxide (TiO2) nanoparticles was applied as a pyroelectric nanogenerator. SbSI nanowires were fabricated under ultrasonic treatment. Sonochemical synthesis was performed in the presence of TiO2 nanoparticles. The mean lateral dimension da = 68(2) nm and the length La = 2.52(7) µm of the SbSI nanowires were determined. TiO2 nanoparticles served as binders in the synthesized nanocomposite, which allowed for the preparation of dense films via the simple drop-casting method. The SbSI–TiO2 nanocomposite film was sandwiched between gold and indium tin oxide (ITO) electrodes. The Curie temperature of TC = 294(2) K was evaluated and confirmed to be consistent with the data reported in the literature for ferroelectric SbSI. The SbSI–TiO2 device was subjected to periodic thermal fluctuations. The measured pyroelectric signals were highly correlated with the temperature change waveforms. The magnitude of the pyroelectric current was found to be a linear function of the temperature change rate. The high value of the pyroelectric coefficient p = 264(7) nC/(cm2·K) was determined for the SbSI–TiO2 nanocomposite. When the rate of temperature change was equal dT/dt = 62.5 mK/s, the maximum and average surface power densities of the SbSI–TiO2 nanogenerator reached 8.39(2) and 2.57(2) µW/m2, respectively.

Summary: Thanks to the nanogenerators known as state‐of‐the‐art energy collecting devices, the mechanical energy in every environment can be converted into electrical energy. Some studies on the improvement of the performance of triboelectric and piezoelectric nanogenerators that convert mechanical energy to electrical energy revealed that aerogels brought significant outcomes in the development of nanogenerators. Aerogels, the lightest solid material known, provides a large surface area as the contact area of the nanogenerators, its adjustable porosity allows to improve electronic properties of the nanogenerators, showing its significance in electronics once again. At the same time, the use of aerogels, which is the best candidate in terms of flexibility and mechanical strength required in wearable electronics, in the production of nanogenerators continues to attract the attention of researchers. This study includes an introduction of aerogels and the discussions on the studies involving aerogel based nanogenerators. In the paper, the studies in the literature, focusing on the advantages of aerogel based nanogenerators and their current applications were collected. Three different types of aerogel nanogenerators production were observed to be produced. They are all based on aerogel electrodes produced from different materials, and the paper outlines them with basic working principles. This classification of aerogel nanogenerators and outlining the results will make a significant contribution to the literature and will be a good source for researchers who want to work in this field. [ABSTRACT FROM AUTHOR]

Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 piezoelectric nanofiber was synthesized using the electrospinning technique. The surface of sintered BCZT nanofibers was modified by dopamine via the chemical coating method. Dopamine-modified BCZT nanofibers were used as fillers in polyvinylidenefluoride–hexafluoropropylene (PVDF-HFP) polymer matrix to cast flexible composite films by solution casting method. Nanofibers and composite films were analyzed by XRD and FE-SEM to investigate crystal structure and morphology, respectively. The broadband dielectric spectroscopy was carried out in composite films having 3.4–24.1 vol% BCZT nanofibers. The composite film having 24.1 vol% nanofibers showed a maximum dielectric constant (61 at 1 kHz) compared with other films. A flexible nanogenerator (NG) was fabricated using epoxy as a packing material. The developed NG tested in different tapping modes and exhibited maximum output voltage and power density around 10 V and 2.9 μW/cm3, respectively. [ABSTRACT FROM AUTHOR]

Summary: There have been tremendous efforts made to investigate various materials to enhance the electrical performance of triboelectric nanogenerators (TENGs) but there is still demand for some techniques to further enhance the performance of tribomaterials. Therefore, we fabricated a bimetallic hybrid cryogel via cheap and facile UV‐radiation as well as in situ reduction method. Fabricated TENG device made up of porous hybrid bimetallic cryogel film containing silver and gold nanoparticles as tribopositive material and poly dimethyl siloxane (PDMS) as a tribonegative layer with dimension of 1 × 2 cm2 has the ability to produced output voltage of 262.14 V with current density of 27.52 mA/m2 and 7.44 W/m2 peak power density, which was sufficient to light up more than 120 white light emitting‐diodes (LEDs). Porous and rough structure, interaction of nanoparticles was the reason behind the performance enhancement of tribopositive material. Thus, this study introduces a very stable and easily synthesized bimetallic hybrid cryogel as a tribopositive material to enhance the performance of tribomaterials to design high performance TENG devices. [ABSTRACT FROM AUTHOR]

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Energy harvesting technologies have found significant importance over the past decades due to the increasing demand of energy and self-powered design of electronic and implantable devices. Herein, we demonstrate the design and application of in situ poled highly flexible piezoelectric poly vinylidene fluoride (PVDF) graphene oxide (GO) hybrid nanofibers in aligned mode for multifaceted applications from locomotion sensors to self-powered motion monitoring. Here we exploited the simplest and most versatile method, called electrospinning, to fabricate the in situ poled nanofibers by transforming non-polar α-phase of PVDF to polar β- phase structures for enhanced piezoelectricity under high bias voltage. The flexible piezoelectric device fabricated using the aligned mode generates an improved output voltage of 2.1 V at a uniform force of 12 N. The effective piezoelectric transduction exhibited by the proposed system was tested for its multiple efficacies as a locomotion detector, bio-e-skin, smart chairs and so on. [ABSTRACT FROM AUTHOR]

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Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Gas sensing properties at room temperature and energy harvesting performances are realized for the polyvinylidene fluoride (PVDF) nanocomposites containing titanium dioxide (TiO2) nanotubes grown in the presence of carbon nanotubes (CNT). While hydrothermal reaction is practiced for the development of TiO2/CNT hybrid nanotubes, spin coating is done for the nanocomposite films to be deposited on sensing electrodes. Influence of various filler concentrations and the synergistic combination of fillers on the sensing characteristics are studied by recording the response times and the stability of the results. Upon exposure to liquefied petroleum gas, the PVDF/TiO2-CNT (2.5 wt.%) gas sensor shows a sensing response of 0.45 s (400 ppm LPG), approximately nine times higher than the composite containing 2.5 wt.% of TiO2 or 2.5 wt.% CNT. The piezoelectric response of the samples is also recorded and correlated with the synergistic influence of the filler materials. The current study can stimulate a good trend in fabricating self-powered gas sensors from PVDF nanocomposites. [ABSTRACT FROM AUTHOR]

The results of experimental studies of the dependence of the memristor effect of bundles of vertically aligned carbon nanotubes on the pressing force magnitude and the switching voltage are presented. The improvement of the memristor effect is shown with increasing pressing force and switching voltage. The dependence of the surface potential on the deformation of nanotubes located along the bundle cross section is shown. The obtained results can be used in the development of promising nanopiezotronics devices. [ABSTRACT FROM AUTHOR]

Here, we report the adsorption effect of NO2 on ZnO (100 nm) nanowires. We have studied the effect of adsorbed NO2 molecules on ZnO nanowire-based energy harvester for an exposure time of 1, 2, 3, 4, 5 and 6 h in a sealed chamber at 50 ppm which yielded piezoelectric voltage of 543.6 mV, 834.6 mV, 1.071 V, 1.78 V, 1.969 V and 2.835 V, respectively. We have thoroughly investigated the behaviour of ZnO nanowires in the presence of NO2 and observed a maximum output piezoelectric voltage of 2.835 V with a power density 158.2 mW cm−2. This is the first time that ZnO-based piezoelectric energy harvester is being used for the voltage enhancement in the presence of NO2. We have used vertically integrated nanowire generator (VING) structure. X-ray diffraction pattern revealed the growth orientation of ZnO nanowires were along the c-axis from the substrate. ZnO nanowires were grown on indium tin oxide-coated polyethylene terephthalate substrates via a hydrothermal route. Surface morphology has been examined by scanning electron microscopy images and diameter of ZnO nanowires was found to be around 100 nm. Piezoelectric voltage has been generated by the VING by applying minute external force of ~50 nN. Periodic output voltage peaks were being measured by picoscope 5204. [ABSTRACT FROM AUTHOR]

Bone is a complex organ possessing both physicomechanical and bioelectrochemical properties. In the view of Wolff's Law, bone can respond to mechanical loading and is subsequently reinforced in the areas of stress. Piezoelectricity is one of several mechanical responses of the bone matrix that allows osteocytes, osteoblasts, osteoclasts, and osteoprogenitors to react to changes in their environment. The present review details how osteocytes convert external mechanical stimuli into internal bioelectrical signals and the induction of intercellular cytokines from the standpoint of piezoelectricity. In addition, this review introduces piezoelectric and triboelectric materials used as self-powered electrical generators to promote osteogenic proliferation and differentiation due to their electromechanical properties, which could promote the development of promising applications in tissue engineering and bone regeneration. [ABSTRACT FROM AUTHOR]

Mechanical energy harvesting technology converting mechanical energy wasted in our surroundings to electrical energy has been regarded as one of the critical technologies for self-powered sensor network and Internet of Things (IoT). Although triboelectric energy harvesters based on contact electrification have attracted considerable attention due to their various advantages compared to other technologies, a further improvement of the output performance is still required for practical applications in next-generation IoT devices. In recent years, numerous studies have been carried out to enhance the output power of triboelectric energy harvesters. The previous research approaches for enhancing the triboelectric charges can be classified into three categories: i) materials type, ii) device structure, and iii) surface modification. In this review article, we focus on various mechanisms and methods through the surface modification beyond the limitations of structural parameters and materials, such as surficial texturing/patterning, functionalization, dielectric engineering, surface charge doping and 2D material processing. This perspective study is a cornerstone for establishing next-generation energy applications consisting of triboelectric energy harvesters from portable devices to power industries. [ABSTRACT FROM AUTHOR]

In the contemporary era, the pursuit of sustainable energy solutions has become paramount, driven by escalating energy consumption and the challenges posed by industrial revolutions. This study introduces an innovative avenue for alternative energy generation, harnessing the latent energy within Rice Husk Ash residue. This proposed technology ingeniously employs iron nanoparticles to construct a cementitious device, poised to function as a potent electricity generator. The principal objective herein is the development of a prototype that efficaciously produces electrical energy. Rigorous testing shall ensue across diverse environments, encompassing exposure to simulated solar illumination and submersion in aqueous environments. The validation of the "prototype" shall be undertaken through the charging of a 1.2 V battery, both under solar irradiation and complete water immersion conditions. Consequently, this hybrid electricity generator not only presents an avant-garde, sustainable alternative but also one that exhibits economic viability and practical applicability. [Display omitted] [ABSTRACT FROM AUTHOR]