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In recent years, electrocatalytic degradation of pollutants based on nanogenerators has gradually emerged. Compared with the huge energy consumption of traditional electrocatalysis, this method can effectively use displacement current to induce charge transfer and complete catalysis, so it can directly use the existing water flow energy and other energy sources in nature. This work will explain the basic principles, methods, and measurement methods of preparing nanogenerators from waste plastics, as well as the classification of electrocatalytic principles and methods relative to nanogenerators, which provides important support for the research in this emerging field. At the same time, the analysis based on this knowledge will also lay the foundation for future design. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric nanogenerators based on polyvinylidene difluoride (PVDF) and lead magnesium niobate-lead titanate Pb(Mg 1/3 Nb 2/3)O 3 –PbTiO 3 (PMN- x PT compositions for x between 30 and 35) particles with various filler ratios from 10 to 30 vol% were fabricated through the electrospinning method. The phase and microstructural characterizations revealed that the homogenous and continuous fiber-shaped composite structure with good interfacial interaction between the PMN-PT particles and the PVDF matrix was achieved. It was found that the diameter of the neat PVDF fibers was approximately 354 nm, whereas the PVDF/PMN-35PT fibers with ceramic particle concentrations of 10, 20, and 30 vol% had average diameters of 317, 249, and 163 nm, respectively. The piezoelectric performance tests indicated that the 30 vol%PVDF/PMN-35PT nanogenerator had a 3 times greater electrical power efficiency (10.59 μW) at 20 Hz compared to that of the pure PVDF nanogenerator (3.56 μW) at 15 Hz under the same resistance load of 1 MΩ. All in all, the incorporation of PMNT-PT particles into the PVDF appears to be a good approach for the fabrication of high-performance flexible piezoelectric nanogenerator applications for biomechanical energy harvesting of devices converting the mechanical movements of organs such as cardiac and lung into electrical energy. [ABSTRACT FROM AUTHOR]

ZnO nanorods (NRs) are piezoelectric materials used as nanogenerators because of their ease of synthesis, nontoxicity, low production costs, good electrical properties, and suitable flexibility for human movement as a source of mechanical energy. ZnO NRs are usually doped or composited with other materials to enhance their properties. Here we discuss the effect of the aluminum (Al) doping of ZnO using the hydrothermal method and subsequent coating with NiO to form a p–n junction in a nanogenerator application. According to XRD characterization, Al doping caused a shift in the ZnO NRs diffraction peaks toward a larger angle and a decrease in the diameter of the NRs. The doping of Al and NiO composites could also widen the bandgap. Moreover, current and voltage characterization results showed that the nanogenerator output power was 14.8 µW, which reached saturation (19.5 µW) at 4 % doping. Therefore, Al doping can improve the output power of the nanogenerator compared with pure ZnO.

The complex process of wound healing depends on the coordinated interaction between various immunological and biological systems, which can be aided by technology. This present review provides a broad overview of the medical applications of piezoelectric and triboelectric nanogenerators, focusing on their role in the development of wound healing technology. Based on the finding that the damaged epithelial layer of the wound generates an endogenous bioelectric field to regulate the wound healing process, development of technological device for providing an exogenous electric field has therefore been paid attention. Authors of this review focus on the design and application of piezoelectric and triboelectric materials to manufacture self-powered nanogenerators, and conclude with an outlook on the current challenges and future potential in meeting medical needs and commercialization.

For outdoor workers or explorers who may be exposed to extreme or wild environments for a long time, wearable electronic devices with continuous health monitoring and personal rescue functions in emergencies could play an important role in protecting their lives. However, the limited battery capacity leads to a limited serving time, which cannot ensure normal operation anywhere and at any time. In this work, a self-powered multifunctional bracelet is proposed by integrating a hybrid energy supply module and a coupled pulse monitoring sensor with the inherent structure of the watch. The hybrid energy supply module can harvest rotational kinetic energy and elastic potential energy from the watch strap swinging simultaneously, generating a voltage of 69 V and a current of 87 mA. Meanwhile, with a statically indeterminate structure design and the coupling of triboelectric and piezoelectric nanogenerators, the bracelet enables stable pulse signal monitoring during movement with a strong anti-interference ability. With the assistance of functional electronic components, the pulse signal and position information of the wearer can be transmitted wirelessly in real-time, and the rescue light and illuminating light can be driven directly by flipping the watch strap slightly. The universal compact design, efficient energy conversion, and stable physiological monitoring demonstrate the wide application prospects of the self-powered multifunctional bracelet. [ABSTRACT FROM AUTHOR]

The present work reports an enhanced magnetoelectric (ME) effect at room temperature (RT) and above in a nanocomposite of LaYFe2O6/poly-(vinylidene fluoride)–hexafluoropropylene [LaYFe2O6/P-(VDF-HFP)], which is prepared by the solution-casting method. Field-emission scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy reveal excellent phase-to-phase connectivity and an enhanced beta-phase fraction in the PVDF matrix by the incorporation of 10 wt % antiferromagnetic nanoparticles (NPs). This is also substantiated by the improved ferroelectric (electric-field-dependent polarization) response by a 10 wt % sample. At RT, this nanocomposite manifests a first-order ME coupling coefficient of ∼2.92 mV cm–1 Oe–1 and a second-order ME coupling coefficient of ∼0.051 μV cm–1 Oe–2 (significantly 1 order higher than that of pristine LaYFe2O6). The enhanced ME coefficient at RT and above makes it a viable candidate to address the challenges of ME-based device applications. A flexible, portable, lightweight, cost-effective magnetoelectric nanogenerator (MENG) fabricated from the nanocomposite film is able to harvest the wasted magnetic energy with an efficiency of 1.5%. As a demonstration, the harvested electric energy is stored in a capacitor, which, in turn, is used to power a light-emitting diode (LED). The present work hence suggests the deployment of this material for self-powered wearable devices. [ABSTRACT FROM AUTHOR]

The recent application of the internet of things demands the ubiquitous utilization of data and electrical power. Even with the development of a wide variety of energy‐harvesting technologies, few studies have reported a device transporting electrical energy and data simultaneously. This paper reports an electrostatic induction nanogenerator (ESING) consisting of a one‐dimensional metastructure that can modulate the output voltage based on the resonance of ultrasound waves to transmit energy and data simultaneously. The ESING device is fabricated using electronegative poly(vinylidene fluoride) (PVDF) membrane using a phase inversion process. The output voltage from the ESING device exhibits periodic resonant peaks as the gap between the PVDF membrane and the Al electrode changes, showing an up to 35‐fold difference between the maximum and minimum output voltages depending on the resonance state. The energy and electrical signal can be transmitted simultaneously in free space because the ESING converts energy from high‐frequency ultrasound waves. This paper provides proof of concept for a data and energy‐transferable smart tag device based on ESING devices exhibiting resonant and non‐resonant states. A device consisting of four ESINGs for a 4‐bit signal is implemented to demonstrate 16 signals. [ABSTRACT FROM AUTHOR]

In this context, the open-circuit voltage generated by either poly (vinylidene fluoride) or PVDF and ZnO composite sample before being enhanced to 4.2 V compared to 1.2 V for the samples of pure PVDF. The spin coating method was used to create a composite film, which served as a piezoelectric nanogenerator (PNG). Zinc oxide (ZnO) nanoparticles and PVDF serve as the matrix for the coating structure. Thin films were created that employed the spin coating method to achieve the desired results of ZnO's non-brittle outcome and piezoelectric characteristics, as well as PVDF for use in self-powered devices. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and fourier transform infrared (FT-IR) were used to evaluate the properties of these formations. The electrical properties of the film were measured using an oscilloscope. Results indicated that by adding ZnO nanoparticles to the PVDF samples, piezoelectric capabilities were enhanced compared to samples containing PVDF only. These results point to promising uses for various wearable devices, such as water strider robot systems and self-operating equipment. [ABSTRACT FROM AUTHOR]

Natural polymers such as cellulose have interesting tribo- and piezoelectric properties for paper-based energy harvesters, but their low performance in providing sufficient output power is still an impediment to a wider deployment for IoT and other low-power applications. In this study, different types of celluloses were combined with nanosized carbon fillers to investigate their effect on the enhancement of the electrical properties in the final nanogenerator devices. Cellulose pulp (CP), microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) were blended with carbon black (CB), carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The microstructure of the nanocomposite films was characterized by scanning electron and probe microscopies, and the electrical properties were measured macroscopically and at the local scale by piezoresponse force microscopy. The highest generated output voltage in triboelectric mode was obtained from MCC films with CNTs and CB, while the highest piezoelectric voltage was produced in CNF-CNT films. The obtained electrical responses were discussed in relation to the material properties. Analysis of the microscopic response shows that pulp has a higher local piezoelectric d33 coefficient (145 pC/N) than CNF (14 pC/N), while the macroscopic response is greatly influenced by the excitation mode and the effective orientation of the crystals relative to the mechanical stress. The increased electricity produced from cellulose nanocomposites may lead to more efficient and biodegradable nanogenerators. [ABSTRACT FROM AUTHOR]

The question of the length dependence of the electromechanical response of semiconducting (SC) piezoelectric nanowires (NWs) was explored. We identified a new physical mechanism of piezoresponse saturation, which originates from the combination of the influence of interface traps and piezoelectric polarization in the depleted NW. Our results are in better qualitative agreement with experimental observations than presently existing theories. To do so, we used the finite element method to simulate the coupled set of equations describing mechanical, piezoelectric and SC properties. In order to reduce the number of parameters, simulations focused on the case of uniform ZnO NWs grown along the c -axis. Saturation was explained by the incapacity of surface traps to maintain depletion along the whole NW beyond a certain length, as a result of the electric potential shift induced by piezoelectric polarization. An analytical model was developed to support this analysis. It provided the dependence trends of saturation length and piezoresponse as a function of NW dimensions, doping level, surface traps density and crystal polarity, as well as with external pressure, in fair agreement with simulation results. Moreover, we discovered that one consequence of this mechanism was that crystal polarity had an impact on the smoothness of the radius-dependent transition between high and low piezoresponse under axial stress. These results have important implications for the optimization of electromechanical sensors and nanogenerators based on piezoelectric SC NWs and related composite materials. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) nanorods have attracted considerable attention in recent years owing to their piezoelectric properties and potential applications in energy harvesting, sensing, and nanogenerators. Piezoelectric energy harvesting-based nanogenerators have emerged as promising new devices capable of converting mechanical energy into electric energy via nanoscale characterizations such as piezoresponse force microscopy (PFM). This technique was used to study the piezoresponse generated when an electric field was applied to the nanorods using a PFM probe. However, this work focuses on intensive studies that have been reported on the synthesis of ZnO nanostructures with controlled morphologies and their subsequent influence on piezoelectric nanogenerators. It is important to note that the diatomic nature of zinc oxide as a potential solid semiconductor and its electromechanical influence are the two main phenomena that drive the mechanism of any piezoelectric device. The results of our findings confirm that the performance of piezoelectric devices can be significantly improved by controlling the morphology and initial growth conditions of ZnO nanorods, particularly in terms of the magnitude of the piezoelectric coefficient factor (d33). Moreover, from this review, a proposed facile synthesis of ZnO nanorods, suitably produced to improve coupling and switchable polarization in piezoelectric devices, has been reported. [ABSTRACT FROM AUTHOR]

Nanogenerators are the backbone of self-powered systems and they have been explored for application in miniaturized biomedical devices, such as pacemakers. Piezoelectric nanogenerators (PENGs) have several advantages, including their high efficiency, low cost, and facile fabrication processes, which have made them one of the most promising nano power sources for converting mechanical energy into electrical energy. In this study, we review the recent major progress in the field of PENGs. Various approaches, such as morphology tuning, doping, and compositing active materials, which have been explored to improve the efficiency of PENGs, are discussed in depth. Major emphasis is given to material tailoring strategies and PENG fabrication approaches, such as 3D printing, and their applications in the biomedical field. Moreover, hybrid nanogenerators (HNG), which have evolved over the last few years, are discussed. Finally, the current key challenges and future directions in this field are presented. [ABSTRACT FROM AUTHOR]

The creation of sustainable power sources for wearable electronics and self-powered systems is a promising direction of modern electronics. At the moment, a search for functional materials with high values of piezoelectric coefficient and elasticity, as well as non-toxicity, is underway to generate such power sources. In this paper, nitrogen-doped carbon nanotubes (N-CNTs) are considered as a functional material for a piezoelectric nanogenerator capable of converting nanoscale deformations into electrical energy. The effect of defectiveness and of geometric and mechanical parameters of N-CNTs on the current generated during their deformation is studied. It was established that the piezoelectric response of N-CNTs increased nonlinearly with an increase in the Young's modulus and the aspect ratio of the length to diameter of the nanotube and, on the contrary, decreased with an increase in defectiveness not caused by the incorporation of nitrogen atoms. The advantages of using N-CNT to create energy-efficient piezoelectric nanogenerators are shown. [ABSTRACT FROM AUTHOR]

Abstract Heart diseases pose a serious threat to human health, and their incidence has been increasing in recent years. In past decades, many strategies have been developed to decrease the mortality and morbidity of heart diseases, among them, strategies involving cardiac electronic devices (CEDs) have been effective in treating and preventing heart diseases. To allow the CEDs to work continuously without the need to replace batteries and to meet the requirements of convenience and comfort in the process of use, nanogenerator (NG)‐based CEDs were proposed, widely studied, continuously optimized in recent years owing to their advantages of small dimensions, self‐powering ability, and good biocompatibility. In this review, recent improvements of NG‐based CEDs of two typical types (i.e., triboelectric nanogenerator [TENG] and piezoelectric nanogenerator [PENG]) and their structures and functions are summarized and discussed. The demands, remaining challenges, and future development trends of NG‐based CEDs are also discussed.

Abstract Wearable electronic devices such as mobile communication devices, portable computers, and various sensors are the latest significant innovations in technology which use the Internet of Things (IoT) to track personal data. Wearable energy harvesters are required to supply electricity to such devices for the convenience of users. In this study, a textile-type triboelectric nanogenerator (T-TENG), produced using commercial electrode fibers, was fabricated to generate electrical energy using external mechanical stimulation. The commercial fiber was an electrode coated with Teflon on a copper wire with a diameter of ~ 320 μm. Using this commercial fiber, a T-TENG was easily fabricated by knitting and weaving. The performance of the T-TENG was analyzed to understand the effect of force and frequency. It was observed that the performance of the T-TENG did not degrade even under harsh conditions and treatment. The textile-type TENG possessed an energy harvesting capability with an output power density of ~ 0.36 W/m2 and could operate electronic devices by charging a capacitor.

Abstract The recent application of the internet of things demands the ubiquitous utilization of data and electrical power. Even with the development of a wide variety of energy‐harvesting technologies, few studies have reported a device transporting electrical energy and data simultaneously. This paper reports an electrostatic induction nanogenerator (ESING) consisting of a one‐dimensional metastructure that can modulate the output voltage based on the resonance of ultrasound waves to transmit energy and data simultaneously. The ESING device is fabricated using electronegative poly(vinylidene fluoride) (PVDF) membrane using a phase inversion process. The output voltage from the ESING device exhibits periodic resonant peaks as the gap between the PVDF membrane and the Al electrode changes, showing an up to 35‐fold difference between the maximum and minimum output voltages depending on the resonance state. The energy and electrical signal can be transmitted simultaneously in free space because the ESING converts energy from high‐frequency ultrasound waves. This paper provides proof of concept for a data and energy‐transferable smart tag device based on ESING devices exhibiting resonant and non‐resonant states. A device consisting of four ESINGs for a 4‐bit signal is implemented to demonstrate 16 signals.

Freestanding, composite films of poly(vinylidene fluoride) (PVDF) and cellulose were synthesized and characterized for morphological, microstructural, vibrational and dielectric properties. The thickness of the freestanding films was found to be ~38 μm. Contact angle measurements showed the hydrophobic nature of the composite films. Fourier transformed infrared (FTIR) spectroscopy confirmed the reduction in the α phase content of the PVDF films with the addition of fillers. The measured dielectric constant of the composite films was found to be more than two times than that of the pristine films. An increase in the dielectric constant of the composite films was attributed to the Maxwell–Wagner–Sillars (MWS) polarization. A triboelectric nanogenerator (TENG) operating in a vertical contact‐separation configuration was fabricated using these composite films. A maximum output power density of ~6 μW/cm2 was achieved from the TENG fabricated using the composite films. [ABSTRACT FROM AUTHOR]

In this work, PLLA and CD/PLLA nanofibers were fabricated using electrospinning and utilized as a particulate matter (PM) and volatile organic compounds (VOCs) filter. The electrospun PLLA and CD/PLLA were characterized with various techniques, including SEM, BET, FTIR, XRD, XPS, WCA, DSC, tensile strength testing, PM and VOCs removal efficiency, and triboelectric performance. The results demonstrated that the best air filter was 2.5 wt%CD/PLLA, which performed the highest filtration efficiencies of 96.84 ± 1.51% and 99.38 ± 0.43% for capturing PM2.5 and PM10, respectively. Its PM2.5 removal efficiency was 16% higher than that of pure PLLA, which were contributed by their higher surface area and porosity. These 2.5 wt%CD/PLLA nanofibers also exhibited the highest and the fastest VOC entrapment. For triboelectric outputs, the 2.5 wt%CD/PLLA-based triboelectric nanogenerator provided the highest electrical outputs as 245 V and 84.70 μA. These give rise to a three-fold enhancement of electrical outputs. These results indicated that the 2.5 wt%CD/PLLA can improve surface charge density that could capture more PM via electrostatic interaction under surrounding vibration. Therefore, this study suggested that 2.5 wt%CD/PLLA is a good candidate for a multifunction nanofibrous air filter that offers efficient PM and VOC removal. [ABSTRACT FROM AUTHOR]

Human physiological signals have an important role in the guidance of human health or exercise training and can usually be divided into physical signals (electrical signals, blood pressure, temperature, etc.) and chemical signals (saliva, blood, tears, sweat). With the development and upgrading of biosensors, many sensors for monitoring human signals have appeared. These sensors are characterized by softness and stretching and are self-powered. This article summarizes the progress in self-powered biosensors in the past five years. Most of these biosensors are used as nanogenerators and biofuel batteries to obtain energy. A nanogenerator is a kind of generator that collects energy at the nanoscale. Due to its characteristics, it is very suitable for bioenergy harvesting and sensing of the human body. With the development of biological sensing devices, the combination of nanogenerators and classical sensors so that they can more accurately monitor the physiological state of the human body and provide energy for biosensor devices has played a great role in long-range medical care and sports health. A biofuel cell has a small volume and good biocompatibility. It is a device in which electrochemical reactions convert chemical energy into electrical energy and is mostly used for monitoring chemical signals. This review analyzes different classifications of human signals and different forms of biosensors (implanted and wearable) and summarizes the sources of self-powered biosensor devices. Self-powered biosensor devices based on nanogenerators and biofuel cells are also summarized and presented. Finally, some representative applications of self-powered biosensors based on nanogenerators are introduced. [ABSTRACT FROM AUTHOR]

With progress in fifth-generation techniques, more advanced techniques are available for disabled people. Disability table tennis has also benefited from the new technology. In this paper, a portable and low-cost triboelectric nanogenerator for wheelchair table tennis monitoring systems is proposed. It was applied for wheelchair table tennis athletes' monitoring. The portable and low-cost triboelectric nanogenerator consists of Kapton, polyurethane triboelectric films, and a foam supporting layer. The materials have flexible and low-cost characteristics. Therefore, the device has no influence on exercise performance. Due to triboelectric and electrostatic induction, the portable and low-cost triboelectric nanogenerator can convert biomechanical signals into electric signals. The electric signal is used as a sensing signal and is transformed in a computer by an Analog-to-Digital acquisition module. The coach acquires motion information in real time from a terminal device regarding force, exercise amplitude, and stability of the athlete. Meanwhile, the electric signal provides also sustainable energy for the microelectronic device. It can light 20 LEDs easily and power a calculator and a watch. This portable and low-cost self-powered triboelectric nanogenerator offers a new approach to the field of motion monitoring for disabled people. [ABSTRACT FROM AUTHOR]

In the ongoing fourth industrial revolution, the internet of things (IoT) will play a crucial role in collecting and analyzing information related to human healthcare, public safety, environmental monitoring and home/industrial automation. Even though conventional batteries are widely used to operate IoT devices as a power source, these batteries have a drawback of limited capacity, which impedes broad commercialization of the IoT. In this regard, piezoelectric energy harvesting technology has attracted a great deal of attention because piezoelectric materials can convert electricity from mechanical and vibrational movements in the ambient environment. In particular, piezoelectric-based flexible energy harvesters can precisely harvest tiny mechanical movements of muscles and internal organs from the human body to produce electricity. These inherent properties of flexible piezoelectric harvesters make it possible to eliminate conventional batteries for lifetime extension of implantable and wearable IoTs. This paper describes the progress of piezoelectric perovskite material-based flexible energy harvesters for self-powered IoT devices for biomedical/wearable electronics over the last decade. [ABSTRACT FROM AUTHOR]

Piezoelectric nanogenerators (PENGs) composed of inorganic ceramic nanoparticles and polymer matrix have received extensive attention from scientific researchers. In this article, PENG based on BaTiO3-Bi/Polyimide (BTO-Bi/PI) composite thin films were prepared. The influence of the doping amount of Bi2O3 on the electrical properties of BaTiO3 and the power generation performance of composite thin films were studied in detail. BaTiO3 doped with 0.1 mol% Bi2O3 achieve optimal piezoelectric properties with d33 of 246 pC/N and d33* of 856 pm/V. The flexible BTO-Bi/PI PENG device demonstrates short-circuit current of 365 nA and open-circuit voltage of 17 V, which shows great capability of capturing mechanical energy; it also can be used as sensors under lower mechanical stress and has a wide operating temperature range. [ABSTRACT FROM AUTHOR]

A nanogenerator (NG) is an energy harvester device that converts mechanical energy into electrical energy on a small scale by relying on physical changes. Piezoelectric semiconductor materials play a key role in producing high output power in piezoelectric nanogenerator. Low cost, reliability, deformation, and electrical and thermal properties are the main criteria for an excellent device. Typically, there are several main types of piezoelectric materials, zinc oxide (ZnO) nanorods, barium titanate (BaTiO3) and lead zirconate titanate (PZT). Among those candidate, ZnO nanorods have shown high performance features due to their unique characteristics, such as having a wide-bandgap semiconductor energy of 3.3 eV and the ability to produce more ordered and uniform structures. In addition, ZnO nanorods have generated considerable output power, mainly due to their elastic nanostructure, mechanical stability and appropriate bandgap. Apart from that, doping the ZnO nanorods and adding doping impurities into the bulk ZnO nanorods are shown to have an influence on device performance. Based on findings, Ni-doped ZnO nanorods are found to have higher output power and surface area compared to other doped. This paper discusses several techniques for the synthesis growth of ZnO nanorods. Findings show that the hydrothermal method is the most commonly used technique due to its low cost and straightforward process. This paper reveals that the growth of ZnO nanorods using the hydrothermal method has achieved a high power density of 9 µWcm−2. [ABSTRACT FROM AUTHOR]

Recent studies have shown that nitrogen doping of carbon nanotubes (CNTs) can lead to the formation of piezoelectric properties in them, not characteristic of pure CNTs. In this work, nitrogen-doped CNTs were grown by plasma-enhanced chemical vapor deposition and the effect of the aspect ratio of the nanotube length to its diameter on its piezoelectric coefficient d 3 3 was shown. It was observed that as the aspect ratio of the nanotube increased from 7 to 21, the value of d 3 3 increased linearly from 7.3 to 10.7 pm/V. This dependence is presumably due to an increase in curvature-induced polarization because of an increase in the curvature and the number of bamboo-like "bridges" in the nanotube cavity formed as a result of the incorporation of pyrrole-like nitrogen into the nanotube structure. The obtained results can be used in the development of promising elements of nanopiezotronics (nanogenerators, memory elements, and strain sensors). [ABSTRACT FROM AUTHOR]

Background: In recent years, nanotechnology has been playing an important role in designing smart fabrics. Nanomaterials have been employed to introduce in a sustainable manner, antimicrobial, ultraviolet resistant, electrically conductive, optical, hydrophobic and flame-retardant properties into textiles and garments. Nanomaterial based smart devices are now also being integrated with the textiles so as to perform various functions such as energy harvesting and storage, sensing, drug release and optics. These advancements have found wide applications in the fashion industry and are being developed for wider use in defence, healthcare and on-body energy harnessing applications. Aim of review: The objective of this work is to provide an insight into the current trends of using nanotechnology in the modern textile industries and to inspire and anticipate further research in this field. This review provides an overview of the most current advances concerning on-body electronics research and the wonders which could be realized by nanomaterials in modern textiles in terms of total energy reliance on our clothes. Key scientific concepts of review: The work underlines the various methods and techniques for the functionalization of nanomaterials and their integration into textiles with an emphasis on cost-effectiveness, comfort, wearability, energy conversion efficiency and eco-sustainability. The most recent trends of developing various nanogenerators, supercapacitors and photoelectronic devices on the fabric are highlighted, with special emphasis on the efficiency and wearability of the textile. The potential nanotoxicity associated with the processed textiles due to the tendency of these nanomaterials to leach into the environment along with possible remediation measures are also discussed. Finally, the future outlook regarding progress in the integration of smart nano-devices on textile fabrics is provided.

To mitigate the ever-increasing waste problem, utilization of recycled waste to fabricate energy harvesting devices has emerged as a propitious alternative. Despite several efforts, it is still a daunting challenge to sustain the properties of recycled-plastic-waste after multiple rounds of recycling. We address the above challenges by developing an industry-viable universal framework to recycle plastic-waste multiple-times without significant degradation in its properties. A multiple-times all-recycled triboelectric nanogenerator (MR-TENG) was demonstrated with high performance and record-high overall operational lifetime stability for 5 million cycles of mechanical impact. To the best of our knowledge, this is the first report of a nanogenerator made completely from recycled mixed-plastic-waste, which can sustain its energy-harvesting performance even after ten rounds of recycling. The multiple-times recyclability can be attributed to the improved van der Waals interactions between the polymeric blends at the macromolecular level facilitated by incorporating a mixed-plastic waste-derived compatibilizing agent, which is validated by molecular dynamics simulation. The adopted industry-viable reactive extrusion to fabricate the materials facilitates easy adaptability and commercialization. The practical application was demonstrated by utilizing it for deep learning-enabled MR-TENG-based advanced cognitive waste sorting and segregation, facilitating digitalized-waste-management, thus facilitating a major step towards upcycling of plastic-waste for circular economy. [Display omitted] • Proposed a universal framework to fabricate triboelectric nanogenerator sustaining its performance after multiple rounds of recycling. • An industry-viable solvent-free recycling process that facilitates large-scale manufacturability and commercialization. • An overall operational lifetime stability for more than 5 million cycles of mechanical impact is achieved. • Deep learning-enabled waste sorting and segregation is explored for waste management. [ABSTRACT FROM AUTHOR]

Recently, triboelectric nanogenerators (TENGs) have been widely used for energy harvesting and self-powered sensing due to their significant and unique advantages. However, the intrinsic mechanisms that contribute to tribo-electricification (TE) between two materials remain as a subject of rigorous debate. In addition to predicting the qualitative charge transfer in solid-solid contacts based on the difference in the work functions of the two moieties constituting the interface, we argue that it is essential to obtain atomic-level, first principles, insights into the bonding properties, quantitative charge transfer, and the possible presence of a electrostatic potential barrier at the interface to fully understand the TE mechanism of a system. We have utilized dispersion-corrected density functional theory (DFT) calculations in this study to systematically investigate the TE potential of bare surface Ti 3 C 2 and Ti 3 N 2 2D MXene monolayers and their surface functionalized modifications Ti 3 C 2 R 2 and Ti 3 N 2 R 2 (where R = -O, -OH, or -F) in contact with Al(111). For these heterostructures, we have analyzed the adhesive energy of the interfaces, the nature of interaction through the electron localization function (ELF), and the charge distribution, which have revealed distinct characteristics of MXene/Al contacts for these monolayer/metal interfaces at their equilibrium distance and the changes in their properties under uniaxial pressure. Among all the metallic 2D MXene variants investigated in this study, we have determined that Ti 3 C 2 F 2 /Al and Ti 3 N 2 F 2 /Al interfaces show exceptional potential for TE. [Display omitted] • A first-principles study on the mechanism of MXene-Al contact electrification is performed. • MXenes with different surface functionalizations are assessed for their role in the contact electrification process. • Crucial insights into different types of interface contacts and their potential in contact electrification are revealed. • A comprehensive assessment of interface barrier variations and their role in the dynamics of contact electrification is performed. [ABSTRACT FROM AUTHOR]

Droplet vibration nanogenerator is a promising technology that can transform kinetic energy into electric energy. In this paper, a vibration droplet nanogenerator based on lead zirconate titanate (PZT) (PZT-VDNG) is proposed, which utilizes the change in double electron layer area at the droplet/PZT interface, hence an extraordinary charge variation, induced by mechanical vibrations. Our approach innovatively combines a high fixed surface charge density with ionic solutions to significantly enhance energy conversion efficiency. A theoretical model of the PZT-VDNG is established, showing excellent consistence with the experimental results. The energy conversion efficiency and its correlation with the materials involved, device structure and circuits used, are investigated in detail. Under the optimal conditions of a vibration frequency of 5 Hz, an amplitude of 2 mm, and a droplet size of 40 μL, a short-circuit current output of 31.43 μA and an open-circuit voltage of 1.5 V are obtained by a single vibration of a droplet, respectively, 111 and 37.5 times larger as compared to those from a VDNG with PTFE polymer layer. This marks a significant leap in the efficiency and potential applications of vibration nanogenerators. [Display omitted] • PZT-VDEG achieved a 31.2 μA peak current and a 1.5 V peak voltage per droplet, 111 and 37.5 times higher than those of PTFE-based VDEG. • PZT-VDEG reached 12.19 μW max output power density, 1219 times improvement over the PTFE-based VDEG. • Output is positively correlated with droplet number, showing scalability for large applications. • The theoretical model accurately predicts PZT-VDEG performance, aiding in high-performance VDEG development. [ABSTRACT FROM AUTHOR]

Energy and environmental challenges stand as pivotal issues in contemporary society. This study presents a novel solid-liquid-solid contact-electro-catalytic (CEC) approach based on n-type and p-type silicon wafers for the degradation of organic dyes such as methylene blue, rhodamine B, eriochrome black T and crystal violet. Notably, under indoor light conditions, the degradation efficiency of 5 ppm methylene blue can achieve an exceptional 96.25 % within a brief 18-min-friction treatment. Our investigation elucidates that the catalytic mechanism arises from the synergistic interplay between electron transitions induced by the tribovoltaic effect and electron transfer facilitated by CEC. Furthermore, the solid-liquid-solid CEC exhibits remarkable attributes such as complete recyclability and reusability, thereby opening new avenues for advancements in solid-liquid-solid CEC research. [Display omitted] • A novel contact-electro-catalytic method based tribovoltaic effect is proposed. • Electron transfer and transition jointly promote the generation of free radicals. • This method could effectively utilize mechanical energy. • Methylene blue molecules can also be degraded in the dark. [ABSTRACT FROM AUTHOR]

Wound healing is a highly orchestrated biological process characterized by sequential phases involving inflammation, proliferation, and tissue remodeling, and the role of endogenous electrical signals in regulating these phases has been highlighted. Recently, external electrostimulation has been shown to enhance these processes by promoting cell migration, extracellular matrix formation, and growth factor release while suppressing pro-inflammatory signals and reducing the risk of infection. Among the innovative approaches, piezoelectric and triboelectric nanogenerators have emerged as the next generation of flexible and wireless electronics designed for energy harvesting and efficiently converting mechanical energy into electrical power. In this review, we discuss recent advances in the emerging field of nanogenerators for harnessing electrical stimulation to accelerate wound healing. We elucidate the fundamental mechanisms of wound healing and relevant bioelectric physiology, as well as the principles underlying each nanogenerator technology, and review their preclinical applications. In addition, we address the prominent challenges and outline the future prospects for this emerging era of electrical wound-healing devices.

Neurological diseases associated with dysfunctions of neural circuits, including Alzheimer’s disease (AD), depression and epilepsy, have been increasingly prevalent. To tackle these issues, artificial stimulation or regulation of specific neural circuits and nuclei are employed to alleviate or cure certain neurological diseases. In particular, ultrasound neuromodulation has been an emerging interdisciplinary approach, which integrates medicine and engineering methodologies in the treatment. With the development of medicine and engineering, ultrasound neuromodulation has gradually been applied in the treatment of central nervous system diseases. In this review, we aimed to summarize the mechanism of ultrasound neuromodulation and the advances of focused ultrasound (FUS) in neuromodulation in recent years, with a special emphasis on its application in central nervous system disease treatment. FUS showed great feasibility in the treatment of epilepsy, tremor, AD, depression, and brain trauma. We also suggested future directions of ultrasound neuromodulation in clinical settings, with a focus on its fusion with genetic engineering or nanotechnology.

Recent studies have shown that nitrogen doping of carbon nanotubes (CNTs) can lead to the formation of piezoelectric properties in them, not characteristic of pure CNTs. In this work, nitrogen-doped CNTs were grown by plasma-enhanced chemical vapor deposition and the effect of the aspect ratio of the nanotube length to its diameter on its piezoelectric coefficient [Formula: see text] was shown. It was observed that as the aspect ratio of the nanotube increased from 7 to 21, the value of [Formula: see text] increased linearly from 7.3 to 10.7 pm/V. This dependence is presumably due to an increase in curvature-induced polarization because of an increase in the curvature and the number of bamboo-like “bridges” in the nanotube cavity formed as a result of the incorporation of pyrrole-like nitrogen into the nanotube structure. The obtained results can be used in the development of promising elements of nanopiezotronics (nanogenerators, memory elements, and strain sensors).

A piezoelectric nanogenerator is an energy harvesting system that converts small-scale mechanical energy into electrical energy. Zinc oxide nanorod structures have gained wide attention as a piezoelectric material for nanogenerator applications, because ZnO has good piezoelectric properties and can be fabricated at low cost. This work studied the morphology and structures of ZnO-PVDF composite films, fabricated using spray pyrolysis, hydrothermal and spin coating techniques. ZnO nanorods were grown using two steps: (1) growing seed layers on a metal substrate using a spray pyrolysis technique and (2) growing ZnO nanorods on the seed layers using a hydrothermal technique. Two different substrates, aluminium and copper foils, were used and the varying hydrothermal growth times were 12 and 14 h. The crystalline and morphological structures of the ZnO nanorods were characterized using X-ray diffraction and Scanning electron microscopy. Then, the ZnO nanorods were coated with poly (vinylidene fluoride) or PVDF using a spin-coating method with different spin speeds of 500 and 1,000 rpm. After spin-coating, the samples were treated with either air-cooling or heating (at 100°C) for 10 minutes. The phases and substituents of PVDF were analyzed using Fourier transform infrared spectroscopy (FTIR). The polar β phase of PVDF is of interest due to its piezoelectric property. The β percentage amount, calculated from the FTIR result, was maximized at 88% with ZnO nanorods and air-cooling. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In response to the call for zero-carbon energy supply for Internet of Things (IoTs) applications and to get rid of the dependence of traditional distributed IoTs devices on batteries, the invention of nanogenerators that can convert wind energy in the surrounding environment into electrical energy have received widespread attention. Herein, a wind energy hybrid harvester (WH-EH) combining a soft-friction and positive-directional triboelectric nanogenerator (SP-TENG) and a hierarchical rotating electromagnetic nanogenerator (HR-EMG) is reported to construct a self-powered forest environment monitoring microsystem. With the design of thin inner wall beams and comb-shaped electrodes, the SP-TENG is able to change the output into positive-directional, which can be stored directly in the energy storage device, breaking the limitation of the alternating positive and negative output of conventional TENGs. In addition, the HR-EMG embeds coils in the cup lid to make the most of the available space in the external package. In the WH-EH, a layered structure, including the HR-EMG and SP-TENG is adopted to jointly utilize wind energy for both higher output and higher utilization. In order to effectively implement wireless monitoring of the forest environment, the WH-EH is further utilized to develop a self-powered forest environment monitoring microsystem by powering the IoTs sensor nodes, realizing ambient temperature and humidity sampling and wireless transmission, so as to achieve the purpose of preventing forest fires. It is believed that the development of the WH-EH and the self-powered forest environment monitoring microsystem provides diverse options for the practicalization of self-powered IoTs systems and the energy supply problem of IoTs sensor networks. [ABSTRACT FROM AUTHOR]

This review summarizes the current trends and developments in the field of polyvinylidene fluoride (PVDF) for use mainly as a nanogenerator. The text covers PVDF from the first steps of solution mixing, through production, to material utilization, demonstration of results, and future perspective. Specific solvents and ratios must be selected when choosing and mixing the solution. It is necessary to set exact parameters during the fabrication and define whether the material will be flexible nanofibers or a solid layer. Based on these selections, the subsequent use of PVDF and its piezoelectric properties are determined. The most common degradation phenomena and how PVDF behaves are described in the paper. This review is therefore intended to provide a basic overview not only for those who plan to start producing PVDF as energy nanogenerators, active filters, or sensors but also for those who are already knowledgeable in the production of this material and want to expand their existing expertise and current overview of the subject. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

Piezoionics is an emerging mechanical-electrical energy conversion paradigm that enables self-powered sensing systems for next-generation intelligent wearable electronics. However, there are currently no rational design approaches to enhance the stimulus response of piezoionic devices. Here, we present a strategy using crown ether as ion-selective mobility differential amplifiers for enhancing the pressured-induced voltage response in ionic polyvinyl alcohol (PVA) hydrogels. The crown ether grafted PVA (PVA-CE) hydrogel prototype achieves a 30-fold amplified piezoionic coefficient of 1490 nV Pa-1 within 0 - 1 kPa, compared to 49 nV Pa-1 of the unmodified PVA. The PVA-CE exhibits an ultra-low pressure detection limit of 0.2 Pa with a fast response time of 18.1 ms. Leveraging these properties, we further demonstrate a human somatosensory network analogous PVA-CE piezoionic skin using arrayed pressure sensing. These capabilities hold great promise for emerging healthcare applications such as synthetic biology, soft robotics, and beyond., (© 2024 Wiley‐VCH GmbH.)

In low-dimensional material systems, augmented physical and chemical properties may be witnessed through a unique morphological evolution. Here, we report the development of an optimized nanowall network of ZnO for the fabrication of a flexible single-electrode triboelectric nanogenerator (STENG)-based tactile and gesture sensors. The chemically grown nanowall network with an adequate pore area endows superior triboelectric output (current ∼0.6 μA and power ∼20 μW/cm 2 ) by offering an optimum surface area and dielectric constant for pressure sensing applications. The rational comparison of the triboelectric properties of nanowall and nanorod structures of ZnO reveals that the higher surface area offered by the hollow walls leads to superior output characteristics. The demonstration of pressure sensitivity of the STENG ∼1 V/N is promising for self-powered tactile sensing applications. The array of STENG sensors, when attached to a user hand, generates distinguishable signals while holding objects of varying curvature and mass. Again, the observation of sensitivity of ∼0.1 V per degree during finger movement activity indicates the gesture sensing ability of the nanowall-based TENG system, facilitating sign language expression through the movement of fingers. Further, the generated electrical signals during tactile and gesture sensing can be classified and recognized through the deployment of machine learning (ML) techniques. In fact, the implementation of Random Forest and K-Nearest Neighbor models has offered an accuracy of 96% while recognizing the output signals generated by the sensor arrays. The demonstration of superior sensing characteristics with the optimized nanowall network may be advantageous in innovating prototype sensors for the differently abled people to distinguish or classify objects on the basis of material, morphology, and mass during their regular activities.

Inspired by camouflage-colored organisms, the development of bio-camouflage systems using electrochromic (EC) technology has gained significant interest. However, existing EC systems struggle with achieving a wide color gamut, noniridescent colors, and self-sustainability. Herein, a self-sustainable color-adaptive bio-camouflage system integrating EC and nanogenerator (NG) technologies, enabling environmental color adaptation, and thermal regulation without an external power source is proposed. The system is based on a zinc-anode EC device (ZECD) with an asymmetric structure, incorporating flexible tungsten oxide and vanadium oxide electrodes. During the EC process, tungsten oxide shifts between blue and transparent, allowing near-infrared thermal modulation, while the vanadium oxide transitions from yellow to transparent. This design enables reversible near-infrared modulation and noniridescent color conversion among black, blue, green, yellow, and transparent. For the self-sustainability of the system, an electromagnetic and triboelectric hybrid NG that collects biomechanical energy is developed. In a typical driven cycle, the integrated system transitions colors and achieves significant near-infrared spectral modulation, demonstrating environmental adaptability and thermal regulation. Experiments on human skin and simulated chameleon color changes further confirm the system's effectiveness. This work highlights the potential of integrating EC and NG technologies to advance color-adaptive camouflage systems, opening new an avenue for bio-camouflage design., (© 2024 Wiley‐VCH GmbH.)

Ubiquitous moisture is of particular interest for sustainable power generation and self-powered electronics. However, current moisture electric generators (MEGs) can only harvest moisture energy in the air, which tremendously limits the energy harvesting efficiency and practical application scenarios. Herein, the operationality of MEG from air to underwater environment, through a sandwiched engineered-hydrogel device with an additional waterproof breathable membrane layer allowing water vapor exchange while preventing liquid water penetration, is expanded. Underwater environment, the device can spontaneously deliver a voltage of 0.55 V and a current density of 130 µA cm -2 due to the efficient ion separation assisted by negative ions confinement in hydrogel networks. The output can be maintained even under harsh underwater environment with 10% salt concentration, 1 m s -1 disturbing flow, as well as >40 kPa hydraulic pressure. The engineered hydrogel used for MEG also exhibits excellent self-healing ability, flexibility, and biocompatibility. As the first demonstration of practical applications in self-powered underwater electronics, the MEG device is successfully powering a wireless emitter for remote communication in water. This new type of MEG offers an innovative route for harvesting moisture energy underwater and holds promise in the creation of a new range of innovative electronic devices for marine Internet-of-Things., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Abstract Background Electrostimulation (ES) therapy for wound healing is limited in clinical use due to barriers such as cumbersome equipment and intermittent delivery of therapy. Methods We adapted a human skin xenograft model that can be used to directly examine the nanogenerator-driven ES (NG-ES) effects on human skin in vivo—an essential translational step toward clinical application of the NG-ES technique for wound healing. Results We show that NG-ES leads to rapid wound closure with complete restoration of normal skin architecture within 7 days compared to more than 30 days in the literature. NG-ES accelerates the inflammatory phase of wound healing with more rapid resolution of neutrophils and macrophages and enhances wound bed perfusion with more robust neovascularization. Conclusion Our results support the translational evaluation and optimization of the NG-ES technology to deliver convenient, efficient wound healing therapy for use in human wounds. Graphic abstract

Sensor-based human action recognition (HAR) is considered to have broad practical prospects. It applies to wearable devices to collect plantar pressure or acceleration information at human joints during human actions, thereby identifying human motion patterns. Existing related works have mainly focused on improving recognition accuracy, and have rarely considered energy-efficient management of portable HAR systems. Considering the high sensitivity and energy harvesting ability of triboelectric nanogenerators (TENGs), in this research a TENG which achieved output performance of 9.98 mW/cm2 was fabricated using polydimethylsiloxane and carbon nanotube film for sensor-based HAR as a wearable sensor. Considering real-time identification, data are acquired using a sliding window approach. However, the classification accuracy is challenged by quasi-periodic characteristics of the intercepted sequence. To solve this problem, compensatory dynamic time warping (C-DTW) is proposed, which adjusts the DTW result based on the proportion of points separated by small distances under DTW alignment. Our simulation results show that the classification accuracy of C-DTW is higher than that of DTW and its improved versions (e.g., WDTW, DDTW and softDTW), with almost the same complexity. Moreover, C-DTW is much faster than shapeDTW under the same classification accuracy. Without loss of generality, the performance of the existing DTW versions can be enhanced using the compensatory mechanism of C-DTW.

Owing to their biocompatibility, chemical stability, film-forming ability, cost-effectiveness, and excellent electroactive properties, poly(vinylidene fluoride) (PVDF) and PVDF-based polymers are widely used in sensors, actuators, energy harvesters, etc. In this review, the recent research progress on the PVDF phase structures and identification of different phases is outlined. Several approaches for obtaining the electroactive phase of PVDF and preparing PVDF-based nanocomposites are described. Furthermore, the potential applications of these materials in wearable sensors and human energy harvesters are discussed. Finally, some challenges and perspectives for improving the properties and boosting the applications of these materials are presented.