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Ocean energy is becoming increasingly important as a promising renewable energy source in modern society. Therefore, how to efficiently harvest ocean energy has attracted extensive research attention. In recent years, hybrid nanogenerators consisting of triboelectric and electromagnetic generators (TEHNGs), which compensate for the deficiency of energy conversion efficiency of single type generator, has been proposed and provided a promising way to harvest ocean energy effectively. Therefore, this review provides a comprehensive and in-depth analysis of TEHNGs from the structural design perspective. The characteristics including structural design, material selection, output performance, etc., of the four types TEHNGS are systematically summarized for the first time. The operating characteristics of TEHNGs with different structures in the ocean are elaborated in detail, as well as the significant influence of structural design on the output power of TEHNGs. In addition, the application scenario, environmental adaptability, and mutual assistance between TENG and EMG are discussed deeply. Finally, the existing challenges and development orientation in the aspects of structure design, materials, power management, durability and stability, and large-scale development, of the TEHNGs are put forward. It is believed that this work will be a significant reference for researchers in relevant field and conducive to the development of the TEHNGs in efficient ocean energy harvesting. [Display omitted] • Advances in ocean energy harvesting with TEHNG is comprehensively reviewed. • The output performance of TEHNGs with different structures are compared. • Hybridization of TENG and EMG is favorable in harvesting wave and current energy. • Challenges and perspectives of TEHNGs in ocean energy harvesting are presented. [ABSTRACT FROM AUTHOR]

In recent years, receiver transducers have gained extensive attention in both research and industrial fields. In particular, the triboelectric receiver transducer (TE-RT) stands out due to their self-powered capability, low cost, and excellent output performance. While theoretical methods for analyzing the output performance are still lacked, which may limit the further development of this field. In this study, we propose an equivalent electromechanical conversion circuit that couples the acoustic field and electric field to predict the performance characteristics of the TE-RT. Specifically, the relationship between the deformation of the diaphragm and output performance of the TE-RT is analyzed through theoretical modeling and clarification of governing equations. Subsequently, a specific transformer revealing the mechanical-electrical conversion mechanism for the TE-RT was proposed using the equivalent circuit method (ECM), and an ECM model was established to analyze the performance of TE-RT quickly and accurately. To further improve the output performance of the TE-RT, piezoelectric materials are integrated into the model to enhance its capacity for converting acoustic energy. Verification for the two types of receiver transducer was conducted using the finite element method (FEM), and the equivalent circuit model fit the simulation results well. The acoustic energy conversion efficiency of the TE-RT can also be further evaluated by the number of turns (n) in the specialized transformer. This study can provide a solid theoretical foundation for the design and development of receiver transducer. [Display omitted] • Deformation of diaphragm & triboelectric transducer output analyzed via theoretical modeling. • Proposed a hybrid piezo/triboelectric transducer for improved output performance. • Proposed a special transformer for revealing mechanical-electrical conversion mechanism for the transducers. • Verification of transducers using FEM showed high model reliability. [ABSTRACT FROM AUTHOR]

Recent advancements in energy harvesting have led to innovative methods for converting droplet motion into electricity, such as droplet triboelectric nanogenerators (D-TENGs). However, enhancing their power generation capacity and efficiency remains a challenge. We present a novel surface engineering approach that significantly boosts the electrical outputs of the D-TENGs. By grafting perfluorodecyltrimethoxysilane (PFDTMS) onto polydimethylsiloxane (PDMS) surfaces pre-treated with sandpaper, we achieve a dual effect: fluoridation and increased contact area between droplets and PDMS. This modification, when applied to a droplet-based TENG, yields a remarkable 10–20 fold increase in power metrics such as current, charge, and voltage as compared to untreated counterparts, resulting in an energy conversion efficiency of 17.1% under a 30 MΩ load. Our enhanced D-TENG efficiently harvested energy from falling tap water droplets, producing a current of ∼2 mA. Remarkably, a single droplet impact could illuminate 400 LED lights. Furthermore, when coupled with capacitors, the device powered a hygrometer and 3 W light bulbs, demonstrating substantial potential for real-world applications. This breakthrough in surface engineering for energy harvesters represents a significant step forward in the efficient and powerful generation of electricity from droplet motions. [Display omitted] • High performance device harvests energy from droplets. • Improved device performance achieved through surface engineering. • The impact of a single tap water droplet can generate a current exceeding 2 mA. • An energy conversion efficiency of 17.1% is achieved under a 30 MΩ load. • A single droplet impact can illuminate up to 400 LED lights. [ABSTRACT FROM AUTHOR]

Triboelectricity in materials has emerged as an innovative and increasingly researched approach for acoustic sensing. Despite its promise, the field has faced significant challenges due to limited working bandwidth and sensitivity. As a result, we have developed a dual-symmetry triboelectric acoustic sensor (DS-TAS), featuring an expansive working bandwidth from 20 Hz to 200 kHz, exceptional sensitivity of 6.67 V/Pa, and a detection limit as low as 0.002 Pa. Moreover, the DS-TAS has been successfully integrated into a real-time, multi-directional ultrasonic radar system, achieving an impressively minimal detection error of less than 5 mm. This breakthrough in acoustic sensing performance positions the DS-TAS as a significant milestone for the field, with broad applications ranging from human-machine interaction to voice recognition. [Display omitted] • The sensor demonstrates a multifaceted performance spectrum. • It holds a remarkable sensitivity of 6.67 V/Pa with a wide sensing range of 0.002 Pa to 0.02 Pa. • A real-time multidirectional ultrasonic radar localization scanning system has been developed. [ABSTRACT FROM AUTHOR]

In the post-Moore's Law era, there is a growing trend towards the development of advanced electronic devices that combine sensory perception, data storage, and computation for various applications. Two-dimensional semiconductor transistors, which utilize charge storage mechanisms, present a promising avenue for future information devices. Here, we introduce a neuromorphic triboelectric charge-trapping MoTe 2 transistor with stacked high- k dielectric structure, aiming to facilitate mechano-driven logic-in-memory for neuromorphic computation. By gating through triboelectric potential, the device demonstrates superior electrical performance, including an impressive switching ratio (>105), minimal off-state current (∼0.6 pA), and robust cyclic stability. By modulating the trapped charges in the stack gate structure via tribopotential modulation, the conductivity state of the MoTe 2 channel can be readily controlled, realizing an exceptional mechano-driven nonvolatile memory with a retention time of up to 104 seconds, consistent switching behavior over 100 cycles, and multi-level data storage capabilities at 8 levels. Furthermore, a mechano-driven programmable inverter can be achieved by connecting a load resistor in series. The triboelectric charge-trapping transistor also possesses the capacity to emulate typical synaptic characteristics at low energy levels (∼147 fJ). Leveraging the finely tunable conductivity through tribopotential, we demonstrate a mechano-assisted artificial neural network capable of recognizing handwritten digits with an accuracy rate of approximately 88.59%. These findings underscore the significant potential of the triboelectric charge-trapping transistor in mechanical-assisted real-time interaction, energy-efficient data storage, and neuromorphic computing. [Display omitted] • We propose a mechano-driven logic-in-memory based on neuromorphic triboelectric charge-trapping MoTe 2 transistor. • Gating by triboelectric potential, the neuromorphic device exhibits excellent electrical performance. • A mechano-assisted artificial neural network is demonstrated to recognize handwritten digits. [ABSTRACT FROM AUTHOR]

As pillars of the fourth industrial revolution, portable electronic devices and the Internet of Things are rapidly expanding. A sustainable energy supply for these devices is crucial to the sustainability of this network. It has been less than two decades since a triboelectric nanogenerator (TENG) was first introduced as a sustainable solution, and the development of these devices is accelerating rapidly. Material, structure, application, and performance optimization of these devices are all studied. The introduction of the MXene family in recent years has led to the development of TENG devices using these 2D materials. Various types of MXene behavior have been reported due to its diversity and customization, as well as its structural features caused by its 2D structure. These advantages have led MXene to its use as electrodes, electron trappers, and friction layers in TENG devices, both independently and as a complex. This article reviews studies on MXene-based TENG devices. The first part examines studies around three axes: MXene type, fabrication method, and application. The second section ranks and compares the performance parameters of these studies, and the third section provides details on the studies conducted. Finally, gaps and research opportunities in this field are highlighted, providing guidance for the future research. [Display omitted] • Reviews research directions on MXene-based triboelectric nanogenerators. • Analysis performance of different MXene-based TENG configurations and compositions. • Highlights open questions and future opportunities for MXene-based TENGs. [ABSTRACT FROM AUTHOR]

After decades of development, flexible force sensors (FFS) with excellent performance have been widely used in health monitoring, sport detection, soft robotics, electronic skin, human-machine interface. Researchers have concentrated on new materials and sophisticated structures for better performance and few have reported on functionality. The functional flexible force sensors (F-FFSs) will greatly enhance their practicality and is what needs to be considered as FFSs move from the laboratory to daily life. This paper is the first to review the functionalities of FFSs and to describe them, such as harsh environment stability, waterproofing, electromagnetic shielding, self-healing and antibacterial function. F-FFS offers great marginal benefits and will be an important development direction in the future. Finally, some questions and perspectives on the application aspects of FFSs will also be presented. [Display omitted] • The mechanisms of four types of flexible sensors and the current research status are outlined. • The advantages and disadvantages of the four types of flexible sensors are summarized and analyzed. • The functionality of flexible sensors is comprehensively reviewed, and its development prospect is prospectively analyzed. • Several representative functionality were analyzed in depth. [ABSTRACT FROM AUTHOR]

In an era marked by a growing demand for sustainable energy solutions and resilient disaster management systems, the convergence of innovative technologies holds the promise of addressing multifaceted challenges. This manuscript explores the multifunctional capabilities of the "smart maracas", a novel triboelectric nanogenerator (TENG) designed to harvest mechanical energy and simultaneously serve as an earthquake sensor. The smart maracas is a striking example of the potential of TENGs to harness mechanical motion for practical applications. The device converts mechanical energy into electrical power through meticulous engineering, opening avenues for self-sustaining power sources in various domains. The manuscript outlines the device's structural design, working principle, and real-time applications, spanning bio-mechanical energy harvesting, vibrational energy scavenging, rotational energy harvesting, and a unique sensing application for door monitoring. A pivotal aspect of this research revolves around the smart maracas' role as an earthquake sensor. Rigorous experiments were conducted to assess the device's responsiveness to simulated seismic forces. Notably, a linear relationship with an R² value of 0.9989 was established between the voltage generated by the smart maracas and seismic acceleration. This remarkable correlation underscores the device's precision and reliability in detecting seismic events, opening doors for cost-effective earthquake monitoring solutions. [Display omitted] • Reusing laboratory falcon tube wastes for sustainable energy and sensing technology. • Plasma ion etching on PTFE balls and Hot water treatment on aluminum enhanced device performance. • SM-TENG Integrates artistry, engineering, energy generation, recycling, and disaster management. • Real-time applications in bio-mechanical, vibrational, and rotational energy harvesting. • SM-TENG expands functionality to door security, multi-directional vibration, and seismic sensing applications. [ABSTRACT FROM AUTHOR]

Schottky direct-current (DC) generators have gained attention for their ability to produce DC output directly without rectification. However, a major challenge is their limited voltage output, often below 1 V, and difficulty in simultaneously increasing both voltage and current outputs. This study develops a new design concept to improve the voltage and current outputs of a conducting polymer/metal Schottky DC generator by injecting a single type of charges from the Schottky unit's exterior to either its semiconductor or metal components. By utilizing a polyaniline-coated fabric and a metal Al plate to create a Schottky DC generator, as well as a single-mode triboelectric device such as PTFE film/metal Al, PTFE film/PA6 nanofiber membrane, or PA6-Ni/Cu plate as the external charge supplier, we demonstrate that injecting positive tribo charges to the Schottky Al electrode or negative charges to the polyaniline results in a significant increase in both the voltage and current outputs of the Schottky generator. The resultant Schottky unit showcased an exceptional peak open circuit voltage increasing to 4.88 ± 0.20 V, and an equally impressive peak short circuit current output peaking at 154.97 ± 5.20 μA (6.20 ± 0.21 μA/cm2). Remarkably, this configuration delivered an outstanding power density of up to 7.37 μW/cm2. These output metrics surpass those of standalone PANI/Al Schottky DC generator counterparts (1.09 ± 0.03 V, 67.32 ± 6.52 μA, and 0.66 μW/cm²), and also surpass most other Schottky DC generators previously reported. Incorporating nano Coulombs of charge into the Schottky generator resulted in an impressive micro Coulombs of charge migration within the Schottky device, achieving a remarkable fourfold amplification of voltage outputs and twofold amplification of current outputs, all while preserving the inherent DC output characteristics intrinsic to Schottky generators. Moreover, we have observed that the amount external tribo charges have a direct relationship with the voltage and current output increases of the Schottky DC generators. These phenomena were consistent, whether introducing positive charges to the Al layer of the Schottky unit or infusing negative charges into the polyaniline layer. Furthermore, alternative triboelectric devices connected to the Schottky generators yielded similar outcomes, thereby corroborating the robustness of our approach. This novel approach shows promise in enhancing power generation efficiency in Schottky DC generators and has potential applications in various fields requiring efficient and direct DC power generation. [Display omitted] • A single-electrode triboelectric device is connected to a piezo- conducting polymer/metal Schottky DC generator. • Upon compression, the hybrid device shows remarkable output enhancements, reaching 4.88 ± 0.20 V and 6.20 ± 0.21 μA/cm2. • The performance surpasses that of standalone Schottky device counterparts and previously reported Schottky DC generators. • Nano Coulombs of the tribo charges lead to micro Coulombs of charge transfer within the Schottky generator. • The output enhancements stem from injecting external single polarity charges into the Schottky diode. [ABSTRACT FROM AUTHOR]

Low power density of polymer piezoelectric nanogenerators is a major hurdle for their application as a potential mode of powering wearable and portable electronic devices. To increase the efficiency, here we suggest use of porous piezoelectric poly (vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) nanofibers. However, designing a process that allows introduction of pores in the nanometric fibers with a diameter of only several 100 nm, is highly challenging due to the intricate physics of polymer/solvent/anti-solvent interactions. Realization of the porous nanofibers would be a breakthrough in the field of piezoelectric nanogenerators. We presents an elegant approach based on the thermodynamics of polymer solutions to tailor porosity in P(VDF-TrFE) nanofibers. By adding a conscious amount of water, carefully chosen as non-solvent based on the ternary phase diagram of P(VDF-TrFE)/water/solvent, we intentionally induce liquid-phase demixing, which leads to formation of nanopores in the electrospun nanofiber. By calculating the mean composition trajectories, we predict and explain formation of the pores in the nanofibers, and show how little variations in initial water content substantially influences fiber porosity. Nanogenerators based on the porous electrospun P(VDF-TrFE) nanofibers show output power that systematically increases with porosity (with 500 times increase in output power for 45% porous fibers). The enhanced output is due to the reduced effective dielectric permittivity of the nanofibers. We unambiguously show that the voltage generation in nanofibers is of the same origin as in neat piezoelectric P(VDF-TrFE) films and is due to the relaxation of segments within the restricted amorphous phase. Understanding how to form nanopores, would have a major contribution to other fields, ranging from nanoporous membranes, as well as porous polymer structures for triboelectric nanogenerators. Porous nanofiber is an effective route to enhance the power output density of polymeric piezoelectric nanogenerators to harvest vibrational energy. The concept has wide application also for triboelectric generators. Image 1 • Vibrational energy harvesters based on porous piezoelectric P(VDF-TrFE) nanofiber are presented that show 500 times increase in output power. • We present a detailed study of P(VDF-TrFE)/solvent/water ternary phase diagram, and the kinetic of nanofiber formation. • Deliberate addition of water into P(VDF-TrFE) solution, allows for introducing nano-sized closed pores into ultra-thin nanometric fibers. • Our methodology to introduce closed shell nano-pores is general and suited for piezoelectric and triboelectric energy harvesters. [ABSTRACT FROM AUTHOR]

In the present study, a feather rotating-TENG (FTR-TENG) was developed by analyzing the properties of nanostructure and changes in friction areas by the aerodynamic motion of naturally evolved feathers. The motion and area of surface of the feathers vary according to the interlocking effect of the aerodynamic nanostructure that was found appropriate for the FTR-TENG in the present study. Owl feather, employed in the present study, demonstrated peak output performance of FTR-TENG of 51.4 V, 4.47 μA at 1.6 cm2 of friction area and 7 m/s of wind speed. In addition, the positive surface charge potential of all feathers has increased by the electrostatic adsorption of hematoxylin, the natural dye, used to maximize the electricity generation efficiency of FTR-TENG by raising the positive triboelectric series of the β-keratin structure of feather. As a consequence, the performance of triboelectric generation was increased, despite the small area and low wind power, compared to the previous results of the rotational wind power generator. The owl feather demonstrated generation of 64.3 V and 6.55 μA with 1.6 cm2 of frictional area at wind speed of 7 m/s, which represented an approximately 25% increase in voltage, and 47% increase in current, compared with that before adsorption. A FTR-TENG based on the hyper-branched nanostructure of the feathers and the adsorption effect of hematoxylin is demonstrated for maximizing the efficiency of the wind-based TENG as an energy harvester. This is a study of a new approach to increase the performance of the TENG by adsorbing hematoxylin, a natural dye, on feathers, as well as the effect of varying friction area on the efficiency of the TENG using the feathers of the hyper branched nanostructure. Image 1 • This is a study of a new approach to increase the performance of the TENG using the hyper branched nanostructure feathers. • The FTR-TENG was developed by analyzing the change of friction area by the aerodynamic motion of feathers. • The adsorption of hematoxylin dye enabled a bigger positive triboelectric series, to maximize the electricity generation. [ABSTRACT FROM AUTHOR]

Control interfaces are important devices for connecting human with machines to achieve various manipulations. Recently, the emerging triboelectric based control interfaces exhibit great advantages in flexible wearable and battery-less applications. To further reduce the device complexity and improve the device practicability, a minimalist control interface with only one sensing electrode is developed based on sliding triboelectric mode. The developed control interface consists of connected grid metal pattern as single-electrode output for multi-directional sensing and controlling. This design provides superior advantages, including realization of multi-directional sensing and controlling using only one electrode and ultra-robust detection mechanism based on the number of the generated output peaks. Compared to the traditional triboelectric nanogenerators, this detection mechanism only depends on the number of the output peaks rather than the absolute magnitude, offering high robustness and reliability in various usage scenarios and for different users. Based on the minimalist design, two types of devices are proposed for the applications of 2D and 3D control. First, a flexible 2D-control patch with single electrode is developed to achieve in-plane 2D control. Next, through the integration of two similar patches on both sides of a card, a flexible 3D-control card is achieved to realize 3D control. In addition, the control patch and the control card are then investigated in terms of energy harvesting performance, both of which show good performance in scavenging energy from human tapping. In practical usage, these two devices are successfully demonstrated for 2D vehicle control and 3D virtual drone control, respectively. The developed flexible, self-powered and minimalist control interfaces exhibit promising potentials for diverse applications such as gaming, virtual/augmented reality, entertainment, smart home, and robotics control, etc. Image 1 • A minimalist control interface with only one grid-pattern sensing electrode is developed based on triboelectric sliding mode. • Multi-directional sensing/control using only one electrode and ultra-robust detection mechanism based on the number of the generated output peaks are realized. • The detection mechanism is only dependent on the number rather than the absolute value of the output peaks, resulting in excellent robustness and reliability in different using scenarios and for different users. • A flexible 2D-control patch with single electrode is developed to achieve in-plane 2D motion control. • A flexible 3D-control card through integrating two flexible patches on both sides is realized for object control in 3D free space. [ABSTRACT FROM AUTHOR]

Abstract Remarkable progress has been made recently in the development of soft materials and devices for human-machine interface. Emerging soft-electronics with skin-inspired stretchable, healable and bio-degradable properties have diffused the boundaries of electronics and biology. Practical utilisation of these electronics relies on the development of a skin-inspired soft energy harvester to power them. Mechanical energy harvesters including triboelectric and piezoelectric nanogenerators have emerged as promising energy harvesters for soft-electronics. In this review, we highlight the recent progress in stretchable, self-healing, and bio-compatible soft triboelectric nanogenerators. We explicitly discussed the operating mechanism, design strategies, fabrication techniques, and performances of the stretchable and self-healing energy harvesters. Additionally, the progress of bio-compatible energy harvesters for effective interaction with biological systems is discussed. Finally, we present the perspectives, existing challenges and future road-map for the development of skin-inspired soft mechanical energy harvesters. Graphical abstract We summarized the recent advances of skin-inspired triboelectric nanogenerator with stretchability, self-healability and bio-compatibility. The available materials, device design, and working mechanism are discussed. Presenting the perspectives, existing challenges and future road-map for the development of skin-inspired soft mechanical energy harvesters. fx1 Highlights • The recent progress of materials, conductors and strategies developed for stretchable TENGs are discussed. • The mechanisms and strategies to realise self-healing TENGs are highlighted. • The materials and methods for biocompatible and implantable TENGs are summarized and suggested. [ABSTRACT FROM AUTHOR]

Abstract A bouncing water droplet not only contains mechanical energy, but also electrostatic energy due to the triboelectric charges on its surface that are generated by its contacts with the surrounding environment. Here, we report development of contact electrification-based water droplet-driven triboelectric nanogenerator (Wd-TENG) for harvesting energy from the water-droplet bouncing between two superhydrophobic surfaces. The Wd-TENG consists of polytetrafluoroethylene balls on the bottom and zinc oxide nanosheets on the top; two surfaces of the device obtain electric energy during the contact electrification from the bouncing water, and additionally, maximize the bouncing motions of the droplets. The device produced a short-circuit current and an open-circuit voltage of 1.3 μA and 1.4 V, respectively. Besides, power-generating performances of the Wd-TENG at various angles of inclination were also investigated, and it showed voltage outputs of 5.5 V, 16 V, 9.8 V, and 6.8 V at the inclination angles of 52°, 58°, 64°, and 70°, respectively. These results demonstrate that the Wd-TENG is potentially a strong candidate for scavenging energy from raindrops. Graphical abstract We report development of contact electrification-based water droplet-driven triboelectric nanogenerator (Wd-TENG) for harvesting energy from the water-droplet bouncing between two superhydrophobic surfaces. The Wd-TENG consists of polytetrafluoroethylene balls on the bottom and zinc oxide nanosheets on the top; two surfaces of the device obtain electric energy during the contact electrification from the bouncing water, and additionally, maximize the bouncing motions of the droplets. It is suggested that the potential of the Wd-TENG demonstrated in this study for harvesting raindrop energy is promising. fx1 Highlights • We report development of contact electrification-based water droplet-driven triboelectric nanogenerator (Wd-TENG). • The Wd-TENG consists of polytetrafluoroethylene balls and zinc oxide nanosheets to effectively harvest from dropping water. • It is suggested that Wd-TENG is potentially a strong candidate for scavenging energy from raindrops. [ABSTRACT FROM AUTHOR]

Abstract The earth has abundant water resources, and efficient harvesting of energy from waves is always a research hotspot. In this paper, we fabricate a box-like triboelectric-electromagnetic hybrid nanogenerator for harvesting water wave energy, which is composed of the triboelectric nanogenerator (TENG) and the electromagnetic generator (EMG). In the case of TENG, the contact and separation between the aluminum film-coated PMMA cylinder and the silicone film covered interdigitated Ag electrodes is formed by ocean waves. In the case of EMG, a rolling magnetic ball is placed on the four coils to generate magnetic flux changes, thus generating electricity. Several experiments are conducted to validate the availability. Experimental results show that the instantaneous maximum output power of TENG is 0.08 mW at a load of 100 MΩ, and the instantaneous maximum output power of EMG is 14.9 mW at a load of 1 kΩ. The hybrid nanogenerator can light up 60 LEDs at the same time. After storing energy in the capacitor, the output DC signal can provide a continuous energy supply with the temperature sensor. More important, the nanogenerator can power the wireless acoustic sensing system. Graphical abstract fx1 Highlights • Combined with TENG and EMG, it can harvest more energy at wider frequencies. • A new rolling structure to harvest two-dimensional direction random wave energy. • It has potential applications in self-powered wireless acoustic sensing system. [ABSTRACT FROM AUTHOR]

Abstract Biocompatible materials are expected to play important roles in biomedical applications. In particular, dipeptide nanostructures have attracted considerable attention because of their biocompatibility, functional molecular recognition, and unique biological and electronic properties. Nevertheless, a lack of mass production and facile fabrication of the stable peptide nanostructure array is one of the major hurdles holding back the practical applications. This study developed a simple and wafer-scale process to produce a cyclo-diphenylalanine (Cyclo-FF) nanowire array via a thermal evaporation process and fabricated Cyclo-FF-based triboelectric energy generators (TEG) with high performance. This approach allowed control of the dimensions of the Cyclo-FF nanowires and the preparation of stable peptide nanostructures under ambient conditions and moisture. The Cyclo-FF nanowires were employed as triboelectric materials for biocompatible nanogenerators, which exhibited high-performance power outputs for future applications. The voltage and current output reached ~ 350 V and ~ 10 μA, respectively, with a surface treatment, which was sufficient to light up over a hundred LEDs. Even after dipping Cyclo-FF nanowires in water or TBS buffer solution, it still worked as a TEG material with minor degradation. This method is compatible for the synthesis of bionanomaterials over a large area, and thus can be a powerful strategy to fabricate high-performance biocompatible energy devices for a range of practical applications in the future. Graphical abstract fx1 Highlights • The large-scale synthesis of vertically aligned Cyclo-FF NWs are presented. • Cyclo-FF NWs are stable under high humidity even in TBS buffer. • A triboelectric generator based on Cyclo-FF NWs reached the power density of ~73.7 mW/m2. [ABSTRACT FROM AUTHOR]

Abstract To accurately evaluate the wellbeing condition of a person, sensing systems with versatile functions are needed. Apart from directly monitoring vital signs, an indirect monitoring approach by measuring human activities with wearable devices has emerged. Herein, a smart textile fabricated with a simple dip coating method is developed with multiple functionalities, such as energy harvesting, physical sensing, and even gas sensing. A maximum output power density of 2 W m−2 is achieved with a layer of PEDOT: PSS coated textile and PTFE under foot stepping at 2 Hz, and the matched impedance is as low as 14 MΩ. A height-varying multi-arch strain sensor with a large strain sensing range from 10% to 160% is developed. Furthermore, the arch-shaped strain sensors mounted on the human fingers are demonstrated to monitor hand gestures for American Sign Language interpretation and robotic hand control. Additionally, four textile-based sensors located at different body parts are employed to track human activities. Beyond that, the smart textile is also demonstrated to be a building block of a wearable CO 2 sensor. Looking forward, this smart textile could be incorporated into real clothes as both energy harvesters and various functional self-powered sensors to enable smart clothes for healthcare monitoring applications. Graphical abstract A versatile smart textile fabricated with a facile and low-cost process is proposed for energy harvesting and activity monitoring. It can harvest energy from diversified human motions. Additionally, a height-varying multi-arch strain sensor made of the smart textile with a wide sensing range is developed. Moreover, it can also detect CO 2 concentration by means of a functional coating. fx1 Highlights • A simple PEDOT:PSS coating process is adopted to achieve the smart textile with and triboelectric performance. • Versatile device configurations can be made from the stretchable smart textiles to harvest energy from various body motions. • The PEDOT:PSS coated smart textile is capable for diversified sensing applications including physical and chemical sensing. [ABSTRACT FROM AUTHOR]

Abstract Sound energy harvesting is one of the promising technologies due to the abundant and clean sound sources. It can be the semi-permanent alternative power supplies for wireless sensor networks (WSNs), which is significant in the Internet of Things (IoT). However, sound waves have the low energy density, so there are many kinds of research in recent years to overcome this problem. This paper provides a comprehensive review of sound energy harvesting, focusing on presenting principles, examples and enhancement methods of sound energy harvesters. In this paper, various approaches are introduced which are classified as sound pressure amplification and transduction mechanism. For sound pressure amplification, two typical types of energy harvesters are presented that one is using a resonator, another one is using an acoustic metamaterial, and these are based on piezoelectric, electromagnetic, and triboelectric mechanisms to convert sound energy to electrical energy. Graphical abstract fx1 Highlights • This paper summarizes the basic principles of sound energy harvesters and its state-of-the-art researches. • It mainly classifed sound energy harvesters as pressure amplification method and transduction mechanism. • Comparison of the reported sound energy harvesters are provided according to device size, and generated power etc. [ABSTRACT FROM AUTHOR]

Abstract Triboelectric nano-generators constitute a promising technology for energy harvesting that can be applied at a large scale and be integrated into the road infrastructure aiming at Energy sustainability and reduction of GHG emissions for road infrastructure operation. This technology can be also applied in small scale for the Internet of Things (IoT) applications, in human monitoring for healthcare applications, in precision agriculture as well as in industry, where the massive networking of sensors and actuators is mandatory and the requirements for energy supply are strict and critical. The usage of triboelectric nano-generators is a promising solution to supply all the above sensors and actuators, due to the autonomous characteristic for power supply that these application sectors will obtain and the minimization of battery usage, decreasing the overall Green House Gas emissions. In this article, a review and the current status of the triboelectric nano-generators (TENGs) is performed together with a number of application examples that are already demonstrated by the scientific community. [ABSTRACT FROM AUTHOR]

Self-powered vibration sensors have the potential to greatly improve vibration monitoring of remote and hard-to-access structures by providing cost-effective and energy-efficient solutions. One promising type of sensors based on the triboelectric generator mechanism has shown significant advantages over other self-powered sensors, including better energy conversion efficiency and high output voltage. However, the majority of the recently reported triboelectric powered sensors exhibit strong frequency dependence, being mostly effective under low frequency vibrations. To address these issues, herein we present a novel design of self-powered vibration sensors based on the clapping mode of a triboelectric nanogenerator (TENG). The sensor, consisting of two tribo-layers made of regular copy paper and PTFE that are clamped together by springs, is able to achieve a high sensitivity of 10.8 mV/g and a broad frequency range from 50 to 8000 Hz with a flat frequency response of ±5 dB, regardless of the inclination angle between the contacting surfaces and gravity. The sensor exhibits high linearity (0.9999) and stability over six days and 400,000 cycles. Furthermore, computational modelling has been conducted to understand the nonlinear clapping phenomenon and the influence of clamping force, proof mass and spring stiffness on the sensor's performance. The potential of the clapping TENG sensor is demonstrated through two different applications such as music recording and diagnosis of the loosing of bolts in a rotating machine. Its superior performances, along with low cost, compact design, and electromagnetic shielding, make it a promising candidate for battery-free high-frequency vibration sensors in practical vibration measurement applications. [Display omitted] • The sensor is capable of a high sensitivity of 10.8 mV/g. • A flat frequency response of ± 5 dB between 50 and 8000 Hz. • Performance is insensitive to the inclination angle with gravity. • High stability of 400,000 cycles and six days with varying humidity. • Made of low-cost materials and shielded from electromagnetic interference. [ABSTRACT FROM AUTHOR]

Human gait analysis strongly correlates with critical health metrics and provides significant information about physiological well-being. Therefore, accurate, fast, and cost-effective gait monitoring is required for intelligent healthcare systems. This paper reports the development of a flexible hybrid transduction Barium Titanate (BTO)/SU-8 nanocomposite-based, individually addressable pressure sensor matrix. The proposed sensor is highly suitable for wearables compared to the conventional pressure sensors due to its speedy and cost-effective design flow and ease of operation. The hybrid (piezoelectric/triboelectric), photo-patternable active layer enables strain and contact electrification-based sensing that convolves into a highly sensitive, lower cross talk and large area pressure sensing. The reported sensor is incorporated with a solder-free modular data acquisition setup for a straightforward design integration. A pressure sensitivity of 34 mV kPa-1 for the deep linear region and 2.7 mV kPa-1 for the linear region over a pressure range of 0–170 kPa is reported. The sensor shows excellent reliability and negligible hysteresis with an average deviation of 2.7 %. Furthermore, the 36 pressure cells with hybrid transduction deliver rich feature extraction to machine learning algorithms compared to single transducer-based systems for an accurate gait and grip strength monitoring. The developed convolution neural network (CNN)-2D model gives a model accuracy of 98.5 % and 98.3 % for two different gait characterizations, while delivering a model accuracy of 93.75 % for grip strength assessment. The combination of hybrid sensor design, development, and use of machine learning offers a novel approach to tackle the issues associated with sensors that are incompatible with rapidly developing smart healthcare technology. [Display omitted] ● A high-performance individually addressable array pressure sensor with minimal inter-cell cross talk is proposed. ● Triboelectric "dead zone" is overcome by utilizing piezoelectric transduction of BTO/SU-8. ● Large area sensing with modular processing circuit integration and photopatternability of active layer is achieved. ● Dual transduction in photopatternable BTO/SU-8 as active layer enables rich feature extraction. ● Effective machine learning integration enables hind foot deformity detection, activity and grip strength monitoring. ● Model achieves accuracy of 98.5 %, 98.3 %, and 93.75 % for only 100 epochs due to feature rich output. [ABSTRACT FROM AUTHOR]

Hybridization of triboelectric (TENG) and electromagnetic (EMG) generators has recently shown to be an effective approach toward harvesting water wave energy. Therefore, it is critical to develop efficient hybrid TENG-EMG designs for this application. This paper presents a hybrid TENG-EMG energy harvester based on heaving wave-energy point absorber which can be potentially used for harvesting energy of waves. The design employs linear tubular EMG unit in conjunction with grating structured freestanding mode TENG. The mechanism of a heaving buoy is taken into the account to apply the energy of water waves into the harvester. The adopted EMG mechanism is a relatively simple and highly efficient configuration and the freestanding grating TENG is very effective due to the use of multiple segments and fixed electrodes. Initially, the working mechanism of the device is theoretically simulated to show the practicality of the design. Then, the output performance of the fabricated device is fully investigated under various dynamical experiments. The energy output capability of the proposed device is demonstrated considering different electrical loads. Accordingly, the phase 1, phase 2, and phase 3 of the EMG part obtains the maximum average power density of 170 W m − 3 , 220 W m − 3 , and 130 W m − 3 , respectively. Also, the TENG unit achieves the maximum average power density of 120 W m − 3 . Finally, the practical application of the hybrid system for charging storage units, lighting light-emitting diodes, and powering a sensor is proved. In fact, the proposed device offers a very cost-effective, simple structure, and effective system which is potentially useful for the blue energy extraction. [ABSTRACT FROM AUTHOR]

Vibration is a widely existing mechanical phenomenon containing enormous energy that can be transformed into electricity without polluting the environment. However, most current mechanical energy harvesters only can scavenge energy from a specific direction, resulting in the waste of energy from other directions. Here, we propose a triboelectric-electromagnetic hybrid generator built on freestanding magnet (FMHG), which is able to harvest low-frequency vibration energy from arbitrary in-plane directions. Besides, it can detect vibration direction from periodical or pulse movement. Under the excitation of shaker, maximum power of 85.7 µW and 3.29  m W are obtained by one electrode pair of the TENG and EMG respectively, which can charge a capacitor of 20 µF to 7 V rapidly benefiting from the hybrid configuration. The hybrid generator can light up commercial LEDs driven by human running and bicycle braking, as well as distinguish leg movement in eight directions, proving its application potential in building up self-powered sensing systems such as alarms, environmental monitor and human-machine interface. [ABSTRACT FROM AUTHOR]

Energy harvesting is a key technology for the self-powered mode of wireless sensor nods and mobile terminals. A large number of devices have been developed to convert mechanical energy into electrical energy. Whereas great efforts have been made to improve the output performance, problems like energy dissipation, device life and response range still need to be addressed. Herein, we report a hybridized triboelectric-piezoelectric-electromagnetic nanogenerator efficiently harvesting vibration energy. Three harvest modes are integrated into a single device, whose core component is a magnetic levitation structure. On the one hand, it presents higher sensitivity than conventional spring or cantilever designs due to low energy loss, which favors the tiny energy harvesting like the slapping desk vibration and the running car vibration. On the other hand, the mechanical fatigue or damage can be avoided by the special structure design. Under 20 Hz, triboelectric nanogenerator (TENG) can deliver a peak output power of 78.4 μW, while the top (EMG2) and the bottom (EMG1) electromagnetic generator can provide a peak output power of 36 mW and 38.4 mW, respectively. Piezoelectric generator located at top (PEG2) and bottom (PEG1) can contribute a peak output power of 122 mW and 105 mW, respectively. The capacitor charge measurement reveals that unit combination performance is remarkably stronger than individual performance, and the combination of TENG+EMG1+EMG2+PEG1+PEG2 has the highest energy harvesting capacity. Finally, this device has been integrated into a wireless sensor system. Results show that the wireless sensor system can be activated and transmit temperature and vibration signal to control computer. This work has a vital significance to the development and application of the internet of things. [ABSTRACT FROM AUTHOR]

Triboelectricity and mechanoluminescence (ML) arise from the same physical processes of charge separation and recombination within the material. By measuring both phenomena simultaneously, researchers can gain insights into the nature and extent of charge separation and recombination, as well as the correlation between mechanical stress and light emission. This work shows that a composite based on polydimethylsiloxane (PDMS)/ ZnS:Cu particles possess the ideal ML and can also generate electric output by contact electrification. Using mechanoluminescent materials in wearable devices offers a non-invasive and reliable way to measure mechanical deformation and stress, generating crucial data for a wide range of applications. The single-electrode mode-based triboelectric nanogenerator (TENG) was developed to realize the simultaneous ML and TENG output. During pressing motion, the PDMS/ ZnS: Cu-based TENG device delivered an electrical output of 210 V and 800 nA. Furthermore, the bending motion was then utilized to demonstrate the simultaneous ML and TENG output during various self-powered applications, such as the monitoring of bent body parts, finger joints, and harnessing wind flow. [Display omitted] • Single-electrode mode-based TENG demonstrates simultaneous mechanoluminescence and triboelectricity output. • Various mechanical stimuli to detect mechanoluminescence and triboelectricity output. • A self-powered sensor for monitoring wind flow and joint bending. • An overall accuracy of 96.7% indicates that the ANN effectively classifies wind flow. [ABSTRACT FROM AUTHOR]

Metaverse is the society of future, which merges the physical and digital worlds by utilizing sophisticated human-machine interfaces (HMIs). In this study, a Metaverse sport interactive system based on triboelectric nanogenerators has been developed, which realizes a real-time interaction among human beings, devices, and the internet. This Metaverse sport interactive system is composed of a self-powered anaerobic power meter (APM), a wireless transmission module, personalized data analysis based on the professional Wingate anaerobic test (WAnT) method, and an augmented reality (AR) application. By leveraging the WAnT method, the power (PP), mean power (MP), and fatigue index (FI) are tested, which indeed reflect the explosive power, speed endurance, and endurance. Meanwhile, the data is transmitted to the cloud via the wireless transmission module, and the users can freely explore the Metaverse through AR application. Notably, through machine learning, the professional WAnT can not only reflect the anaerobic capacity but can also be used for athlete selection. Essentially, this work puts forward a new approach to design online competitions, sport training, and athlete selection, and in general, provides a new strategy to build the Metaverse. [Display omitted] • MSIS is consisted of a self-powered anaerobic power meter, a Bluetooth module, Wingtate analysis method, and an AR platform. • The anaerobic power of athletes is the first time tested by TENGs with the Wingtate anaerobic power. • Athletes are selected by a unique deep-learning method based on wingate anaerobic power test. • People can interact with others online via MSIS. [ABSTRACT FROM AUTHOR]

Utilising an interfacial piezoelectric ZnO nanosheet layer, a significant enhancement in the power density is reported for the triboelectric nanogenerators (TENG) based on phase inversion membranes of polyvinylidene fluoride (PVDF) and polyamide-6 (PA6). At an applied force of 80 N, the TENG device incorporating electrochemically deposited ZnO nanosheets produces an output voltage of ~ 625 V and a current density of ~ 40 mA m −2 (corresponding a charge density of 100.6 μC m −2 ), respectively; significantly higher than ~ 310 V and ~ 10 mA m −2 (corresponding a charge density of 77.45 μC m −2 ) for the pristine TENG device. The enhancement in the surface charge density provided by the interfacial piezoelectric ZnO layer is also reflected in the high piezoelectric coefficient d 33 (−74 pm V −1 ) as compared to the pristine fluoropolymer membranes (−50 pm V −1 ). For tribo-negative membranes incorporating the interfacial ZnO layer, piezoelectric force microscopy measurements further show enhanced domain size which can be attributed to the interfacial dipole-dipole interaction with the ferroelectric polarisation of PVDF, which promotes the alignment with the polar axis of ZnO. Under compressive stress, the piezoelectric potential thus produced in the ZnO nanosheets provides charge injection on to the surface of ZnSnO 3 -PVDF membrane, improving the charge density, which in-turn significantly enhances the power density from 0.11 to ~ 1.8 W/m 2 . The TENG devices thus fabricated using a facile electrochemical deposition and phase inversion technique show enhanced output power without the need for high electric field poling or external charge injection process by relying on the coupling of triboelectric and piezoelectric effects. [ABSTRACT FROM AUTHOR]

With the rapid development of wearable electronics like artificial e-skins and smart patch, harvesting biomechanical energy and realizing self-powered sensing are of essential importance for achieving sustainable and efficient function of the system. Here we report a flexible hybrid device that can be conformally attached on soft surface like human skin to harvest diversity touch energies based on electrospun nanofiber mat. Facilitated by the working mechanisms of triboeletric and piezoelectric, the device can generate maximum peak power up to 84 μW/cm 2 and 0.11 μW/cm 2 for the TENG and PENG part when stimulated by a compressive stress, which can enhance the energy harvesting efficiency and expand its application areas. By virtue of the high sensitivity of the piezoelectric nanomaterial, the device can also be attached on different parts of body for real-time monitoring the human physiological signals such as respiratory information and radial artery pulse, which shows potential value in self-powered e-skins and healthcare monitoring systems. [ABSTRACT FROM AUTHOR]

We report a hybridized electromagnetic-triboelectric nanogenerator including an electromagnetic generator (EMG) and a triboelectric nanogenerator (TENG) for simultaneously scavenging wind energy. The TENG can deliver a largest output power of about 1.7 mW under a loading resistance of 10 MΩ, while the EMG can deliver a largest output power of about 2.5 mW under a loading resistance of 1 kΩ. A power management circuit has been designed to store the produced energy from the TENG into a capacitor, resulting in the enhanced energy-storage efficiency of up to 112% as compared with that of using a traditional rectifier. The charging rate of the capacitor by using the TENG has been optimized by changing the inductance and the switching on/off time. As compared with the individual TENG or EMG, the hybridized nanogenerator has a much better ability for sustainably powering a temperature sensor, exhibiting the potential applications of hybridized nanogenerators in self-powered sensor systems. [ABSTRACT FROM AUTHOR]

Traditional MEMS acceleration sensors have been well developed, but most of them require an additional power source to operate. Moreover, they are usually susceptible to limited mechanical shock survivability due to the dominant reliance on rigid materials such as silicon. Recently, with the advancement in flexible materials and nanogenerators, piezoelectric sensors have received increasing interests due to the distinctive property of electricity generation, caused by its structural deformation. In this paper, we demonstrate a novel triboelectric acceleration sensor with flexible structure that is not only self-powered without the need of additional power source, but also is durable in a wide spectrum of operating ranges. The sensitivity is measured to be 1.33 mV/(m/s 2 ) with 0.64% nonlinearity over the acceleration range from 0 to 6 m/s 2 , and the shock survivability of 15,000 g. We envision that our work provides a new train of thought to combine MEMS technology and flexible electronics for the development of sensors with high shock survivability and low power consumption. [ABSTRACT FROM AUTHOR]

Piezoelectric (PE) devices, including PE nanogenerators (PENGs) and sensors, have been extensively studied for applications that require the transduction of mechanical and electrical energy. Recently, the need for flexible and responsive mechanical-to-electrical transducers has ignited a widespread trend in developing electromechanically active polymers. However, reports detailing the electrical characterisation of such materials have given insufficient attention to the influences of static energy (i.e., triboelectricity (TE)) in the electrical outputs reported. Separating PE and TE contributions is complex, as both occur due to mechanical motion and the waveform of the output signal is exceptionally similar. In this work, the popular frequency domain analysis technique – the fast Fourier transform (FFT) is used for the first time to decouple the energy contributions of PE and TE nanogenerators by comparing a polyvinylidene difluoride (PVDF) PENG against a non-PE polyimide (PI) NG. The intensity and the bandwidth of PE and TE signals, relative to the excitation frequency, enabled rapid identification of TE contributions in the PE measurements. This method will enable the accurate development of PE devices with precise electrical outputs in the future. [Display omitted] • Fast Fourier transform (FFT) distinguishes piezoelectric and triboelectric signals. • Differences in displacement signals in the time domain and frequency domain. • Charge induction effects visualised using the fast Fourier transform (FFT). • Approach to electronically characterise piezoelectric and triboelectric signals. [ABSTRACT FROM AUTHOR]

Liquid-solid-based triboelectric nanogenerators (LS-TENG) are new tools for collecting energy from water in nature. Recent efforts have been made on LS-TENG based on superhydrophobic surfaces with faster sliding speed of water droplets and more efficient LS separation comparing to the hydrophobic ones, resulting in higher energy output performance. However, there is a tradeoff between sliding speed and LS contact area. Solving this tradeoff will raise both the output capability and energy conversion efficiency. In this study, we demonstrate a new TENG based on liquid-organogel (LG) interface. By introducing organogel as the triboelectric layer, a new slippery contact mode is established between water droplets and organogel. In physical chemistry, the slippery contact is applauded for the high sliding speed and large contact area, which creates an opportunity for our current task. During sliding of a water droplet on LG-TENG, the electrostatic induction yielded a transferred charge of ∼12 nC per droplet, which is 3 times greater than that from control experiment based on LS-TENG. In despite of the high output performance, the LG-TENG is of low-cost and up-scalability, which make it a ready candidate for harvesting distributed energy from natural resources on the vast outdoor facilities. [Display omitted] • The sliding resistance of the water droplet on organogel surface is 25 µN. • The contact area of the water droplet on organogel is approximately 3 times higher. • Through inducing organogel, transferred charge of 12 nC per droplet is achieved. • Outputs are 3 times higher than that of LS-TENG with the same material composition. [ABSTRACT FROM AUTHOR]

Vibration in the environment usually shows uncertainty with random changes in frequency and sudden acceleration impact. However, it is a huge challenge for existing vibration energy harvesters and sensors to work in random and even extreme vibration environments due to their rigid multi-component architecture with mechanical mismatches. Here, we propose a general design of vibration transduction with broadband response and high mechanical robustness that mimics the biological musculoskeletal system. Such design is based on a tensegrity structure, consisting of a rigid frame and soft strings, combined with triboelectric nanogenerator (TENG). The Tensegrity-inspired triboelectric nanogenerator is of broadband (0–200 Hz) frequency response and exhibits excellent impact resistance under high g acceleration impacts (105 g level). The device can still work normally after undergoing some structural damage. It has been successfully applied to the aeolian vibration monitoring of transmission lines and shows more reliable performance than commercial sensors when suffering the hail impact. Such tensegrity structure design has great potential in high-performance vibration monitoring in the industrial environment. [Display omitted] [ABSTRACT FROM AUTHOR]

Fiber electronics discretely integrated into daily life is taking center stage for its enormous potentials for healthcare, physiological monitoring, and human-machine interfaces. However, the state-of-the-art fiber electronics are remarkably distinguished from generic fibers in diameter, stiffness, smoothness, and productivity. Here, we developed a universal scalable manufacturing process and generic fiber-like fine and soft self-powered interactive electronics with a diameter of only dozens of μm and a continuous length of hundreds of kilometers. These fiber electronics are prepared with a large-scale manufacturing speed (>20 m/min), and adapt to modern textile technology including weaving, knitting, sewing and embroidering. Moreover, Kawabata evaluation system for fabrics was systematically employed to analyze the fiber electronics enabled e-textile's sensorial comfort, suggesting that adding the fiber electronics to fabric benefits its tactile sensations (e.g., softness, fluffy and fullness). Based on tribotronics, the interactive fiber electronics-based smart clothing demonstrates versatile applications including biomechanical energy harvesting, vital signal detecting, human motion recognizing and tactile sensing. [Display omitted] • Industrial-level large-scale and continuous manufacture is thoroughly demonstrated. • The fiber electronics is ultra-fine, soft and compatible with various textile technologies. • Kawabata evaluation system is systematically to evaluate the electronics' sensorial comfort. • The fiber electronics is promising for energy powering and human-machine interaction. [ABSTRACT FROM AUTHOR]

Constructing a multifunctional material for harvesting different types of energy requires a novel strategy that can offer a higher output while simultaneously reducing the device's size and increasing its usability. Here we have developed a flexible Ag 2 Te-nylon nanocomposite film-based hybrid device using a vacuum filtration technique that can harvest simultaneously thermal and mechanical energy using the thermoelectric and triboelectric effect. The flexible hybrid device can generate a power of ∼ 35 nW corresponding to a power density of 58 µW/cm2 through simple finger touch by thermoelectric effect, whereas an output power of ∼7 nW corresponding to a power density of 23 nW/cm2 can be generated via rubbing with fingertips due to the triboelectric effect. In the Ag 2 Te-PVDF nanocomposite film, an output power of 0.3 µW (corresponding to a power density of 1 µW/cm2) has been achieved while rubbing with fingertips. The fabricated device in this study is the only one of its kind where a single material can harvest thermal and mechanical energy. The flexible film's hybrid energy harvesting feature, along with the advantages of low cost and simple synthesis, makes it a promising choice for harvesting energy from human activities. [Display omitted] • Fabricated a multifunctional flexible Ag 2 Te-nylon nanocomposite film. • Employed a simple and cost-effective vacuum filtration technique for synthesis. • Hybrid device fabricated for simultaneous harvesting thermal and mechanical energy. • Demonstrated the device's ability to harvest energy from human activity. [ABSTRACT FROM AUTHOR]

Despite being very promising technology for several devices, triboelectric nanogenerators (TENGs) tend to explore expensive and complex microstructures. This study reports a novel and simple TENG based on the incorporation of silk fibroin in poly (vinyl alcohol) as a simple, low-cost, and easily integrated component for transparent and flexible devices, with output performance of voltage, current, and power density of 172 V, 8.5 μA and 1.304 W.m−2, respectively, and charging capacity of 320 nC per cycle of operation, making possible the light up 56 commercial LEDs and small electronic devices. Adequate control in the polarization degree and morphology of the device are some of the critical factors that improve the performance of the proposed TENG. [Display omitted] • Flexible and bio-based TENGs are promising templates to be incorporated into transparent devices. • The incorporation of silk fibroin into poly(vinyl alcohol) results in a promising tribopositive membrane. • Bio-based TENGs with silk fibroin and PVA are favored by the good mechanical properties of components. • The PVA/silk fibroin-based TENG reaches performance in power output density in the order of 1.304 W.m−2. • The good cyclability of PVA/ silk fibroin TENG favors the prolonged operation of the device. [ABSTRACT FROM AUTHOR]

Triboelectric generators (TEGs) are state-of-the-art powering solutions for low-power Internet of Things (IoT) devices. TEGs convert periodic mechanical vibrations into cyclic charge flow between electrodes, establishing an alternating current (AC). AC output requires rectification prior to charging any load, creating additional circuitry and power requirements. In recent years, the focus has shifted towards developing direct current (DC) generators as potential direct powering solutions. In this work, a DC–TEG is realized using a novel topology involving mechanical switching between a pair of metal contacts. This switching is implemented in vertical contact-separation mode and therefore does not involve any significant friction between the electrodes and metal contacts, overcoming the major limitation of wear and tear in conventional mechanical switching DC–TEGs. The proposed device can obtain each half-cycle rectified output across distinct electrode pairs, which is crucial for conditioning the asymmetric output of the TEGs. An AC output can be simultaneously harvested between the pair of bottom electrodes. The complementary AC–DC outputs of this device can supply power to multiple loads at a time, or coupled together to produce an enhanced output. Placing two complementary TEG pairs adjacent to each other in this topology has the advantage of reducing the ambient electric field, which is critical in improving the charge retention capability of the TEG layers. The proposed device achieves peak instantaneous power of 1.05 μ W for the DC output and 1.12 μ W for the AC output across a 7 M Ω resistance. The applications of the device in driving commercial electronics, harvesting biomechanical energy, and as progressive alarming system are demonstrated. Due to its simple, flexible topology and AC-DC dual output, this device has the potential for powering multiple loads and applications in diverse scenarios. [Display omitted] • A Triboelectric Generator (TEG) device generating both AC and DC outputs is proposed. • The dual rectification topology generates half cycle output across distinct contact pairs. • The rectification is performed by mechanical switching in contact-separation mode. • The compact topology is designed with commercial materials without intricate fabrication steps. • A linear and highly sensitive voltage variation with pressure is observed at low frequencies. • The suitability for biomechanical sensing and energy harvesting applications is demonstrated. [ABSTRACT FROM AUTHOR]

In this study, triboelectric nanogenerator based self-powered active flexible hydrogen (H 2 ) sensor (TEHS) has been investigated using a micropatterned PDMS and Pd nanoparticles coated vertical ZnO nanorods (Pd-ZnO NRs). Adsorption-desorption of H 2 on the Pd-ZnO surface during contact electrification with the micropatterned PDMS film due to applied mechanical force was studied in terms of triboelectric outputs. In air, TEHS showed the peak-to-peak open-circuit voltage and short-circuit current of around 5.2V and 80 nA, respectively, while the output voltages varied with different H 2 gas concentrations. The output voltage and response of the sensor were found to be nearly 1.1V and 373% to 1 vol% ppm H 2 , respectively, and the response time was measured to be around 100sec. These results of the proposed approach suggest the possibility for developing a practical self-powered system for gas sensing applications. [ABSTRACT FROM AUTHOR]

An aptamer-based triboelectric biosensor is developed for a highly specific, label-free and self-powered detection of thrombin. For the first time, intermolecular recognition interactions are used to develop a selective nanosensor based on triboelectric effect. Positively charged Au nanoparticles (Au NPs + ) with large difference in triboelectric polarity and work function are assembled onto Al film to increase the electrical output of triboelectric nanogenerators (TENG). Modification of anti-thrombin aptamers on the Au NPs + -assembled TENG affords the triboelectric nanosensor highly selective toward thrombin, even in clinical samples because of specific binding affinity between aptamers and thrombin unlike random DNA-modified TENGs with undetectable response. A 0.41 nM limit of detection is achieved, which is directly demonstrated by the number of commercial LED lights without any supporting equipment such as power source and electrometer. Our study demonstrates an innovative and unique approach toward the self-powered and label-free detection of thrombin for rapid and simple in-field analysis. [ABSTRACT FROM AUTHOR]

High-efficiency rotation based energy harvesters require simultaneous scavenging of mechanical energy and rotation-induced wasted thermal energy. A hybridized nanogenerator is reported that has an electromagnetic generator (EMG), a triboelectric nanogenerator (TENG), and a thermoelectric generator (ThEG) for simultaneously harvesting mechanical and thermal energies in one process. As driven by the relative rotation motions between two disks, all of the EMG, TENG and ThEG can deliver outputs due to the cooperative operation of electromagnetic, triboelectric, and thermoelectric effects. With increasing the working time of the hybridized nanogenerator, the output power of EMG can be kept in a stable value, and an obvious increase can be seen for the output power of ThEG, while the output power of TENG exhibited a dramatic decrease. By using the power management circuits, all of the EMG, TENG, and ThEG devices can deliver a constant output voltage of 5 V, where the hybridized nanogenerator can produce a pulsed output current peak of about 160 mA. Moreover, the hybridized nanogenerator has been successfully installed in a commercial bicycle to scavenge biomechanical energy for lighting up globe lights and charging up a cell phone. [ABSTRACT FROM AUTHOR]

Developing a successful strategy to maximize the surface charge density is crucial to speed-up the commercialization success of triboelectric nanogenerator. Here, for the first time, the fabrication of positive triboelectric material to donate electrons efficiently to dielectrics is reported, by increasing the stretchability for the uniform contact and by introducing a functional group for the surface potential control. A highly stretchable and conductive film with Ag nanowires and PDMS was fabricated as a base material, in which the portion of nanowires exposed above the embedding surface should be accurately controlled. In specific, positively charged 4-(dimethylamino)pyridine (DMAP) coated Au nanoparticles, prepared by phase transfer method, are coated. The DMAP lowers the effective work function of the nanoparticles by a permanent dipole induced at the DMAP-Au interface and enhances the electron transfer to the dielectrics, confirmed by the Kelvin probe force microscope measurement. The designed nanogenerator gives an output performance up to 80 V and 86 μA, and 2.5 mW in output power, 2.5 times enhancement compared with the conventional TENG. With the integration with AC to DC converting circuit and buck-boost circuit, the nanogenerator produces a constant voltage of 2.6 V. The wireless sensing system, which operates the remote controller, were also demonstrated, turning on a siren. [ABSTRACT FROM AUTHOR]

Schottky direct-current (DC) generators can convert ambient mechanical energy into DC power, showing potential in portable electronics, wireless networks, and the Internet of Things. However, most Schottky DC generators generate a voltage output below 1 volt. Increasing the voltage output would considerably broaden their applications but remains challenging to achieve. In this study, we developed a novel DC generator that shows increased and tunable voltage outputs by combing the Schottky DC generator with triboelectric components. Using polyaniline-coated fabric and metal aluminum to prepare Schottky DC devices, we showed that the device voltage outputs were increased largely when a scatting layer of polyvinylidene fluoride (PVDF) powder covered the surface of either the metal Al or the polyaniline-coated fabric between them. Under compression impact, the PVDF-involved device (areal coverage 46.26 ± 0.60% on the Al surface) generated a peak open-circuit voltage of 3.2 ± 0.10 V and a short-circuit current of 15.06 ± 0.3 μA (current density 3.77 ± 0.08 μA cm−2), with a power of 12.32 ± 0.45 μW (measured by an external resistor method). The open-circuit voltage and power were 3.7 times and 1.5 times higher when compared with the same DC generator without PVDF. By changing the PVDF powder coverage area, the DC output voltage can be tuned linearly in the range of 0.86–3.20 V. However, when the coverage was above 50%, the outputs turned from DC to AC. We also simulated the electrical outputs using a circuit simulation program (LTspice XVII). The simulation results agreed well with the experimental findings, suggesting the improvement of the electrical output follows the classic electrical principle. Such Schottky diode-triboelectric hybrid may form a novel approach for developing DC energy harvesters and self-powered sensors with adjustable voltage output for various applications. [Display omitted] • DC Schottky-triboelectric hybrid generators were prepared by incorporating PVDF particles into the Schottky devices. • The modified devices showed an increase in voltage outputs up to 3.2 V. • The PVDF particles introduce triboelectric charges into the device. • The circuit simulation results indicate that the triboelectric units are connected in parallel with the Schottky device. [ABSTRACT FROM AUTHOR]

Self-powered triboelectric nanogenerators (TENG) have shown great potential in the field of electronic skin (E-skin). However, TENG is vulnerable to damage by frequent mechanical impacts during operation. In this work, a self-healable (≤ 2 h), super-stretchable (> 760%) and shape-adaptive TENG was designed as an E-skin to harvest energy and monitor human motion. The triboelectric layer is self-healing double-crosslinked polydimethylsiloxane (PDMS) prepared by adjusting the ratio of imine bonds to hydrogen bonds (H-bonds). The electrode layer is self-healable conductive composite prepared via the formation of H-bonds between MXene and lightly cross-linked PDMS. This TENG can be perfectly attached on the uneven human skin surface due to shape adaptability and can maintain original triboelectric performance after repeated damage. Also, our TENG can switch freely between single sensor and sensor arrays due to high self-healing efficiency, suggesting promising applications in E-skin and wearable device. [Display omitted] • Self-healing PDMS with super stretchability was prepared by adjusting the ratio of imine bonds to hydrogen bonds. • Self-healing conductive layer was obtained via the formation of hydrogen bonds between MXene and lightly cross-linked PDMS. • Assembled self-healing TENG can closely fit the human body to sense human movement ascribed to good shape-adaptability. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENG) have great potential to help enhancing the energy efficiency of buildings, and thus to contribute significantly to the reduction of global greenhouse gas emissions. However, there are major barriers against the adoption of such emerging energy technologies. Meeting the need for sustainable large-scale fabrication of high-performance products remains a critical challenge towards real-world TENGs' building applications. To mitigate this challenge, we enhance the poor polarizability of native wood by a scalable plasma treatment, a facile approach which to the greatest degree preserves wood's warm colors, mechanical robustness while efficiently enhancing the triboelectric output. We demonstrate the enhancement of electric output by assembling wood triboelectric nanogenerators (W-TENGs) in both contact-separation and single-electrode operation modes. We show that when two radial-cut wood samples (L × R × T: 100 × 80 × 1 mm3), one treated with an O 2 plasma and the other with a C 4 F 8 + O 2 plasma, are subjected to periodic contact and separation with an applied pressure as low as 0.0225 MPa, a maximum voltage of 227 V and a current of 4.8 µA are produced. Eventually, we showcase the real-world applicability of our approach with two prototypes of triboelectric wood floors, opening up new technological pathways towards a 'net-zero emissions' future. Self-powering floors assembled from plasma-treated wood convert the occupants' mechanical energy directly into useable electricity, powering household lamps or electrochromic windows. [Display omitted] • Wood is a cost-efficient micro- and nanostructured scaffold for fabricating efficient triboelectric surfaces. • Plasma treatments enable wood with a wide spectrum of tribopolarities, greatly improving the triboelectric output. • Selection of wood species, cutting directions, and plasma parameters allow tuning of tribopolarity. • Plasma-treated wood triboelectric nanogenerators are suitable for large-scale building applications. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) with triazine skeleton have been developed via reticular chemistry. In this present work, a triazine-based nitrogen-rich organic moiety has been used for the COF synthesis and then tested for the output performance of a triboelectric nanogenerator (TENG) using the same. The synthesized COF has been characterized by several physical characterization techniques. For the first time, the surface potential of the prepared COF material was tested experimentally using Kelvin probe force microscopy, which indicates a very high positive triboelectric potential of 2.03 V. The single unit of COF-based TENG delivered 70 V, 0.6 μA, and 38 nC as an electrical output. In the case of multiunit TENG, the current and voltage values are boosted as the parallel connection of four units of TENG gave the peak-to-peak current output rises by 6.3 μA. In comparison, the series connection of four units of TENG gave a high peak-to-peak voltage of 175 V. This work describes the synthesis of N-rich COF material, fabrication of the TENG, and the excellent energy harvesting performance with the realization of low-cost self-powered hand strengthening device. This result paves the way to achieve fruitful exercise monitoring units towards improving lifestyle. [Display omitted] • Synthesis of covalent organic framework with high positive surface potential. • 3D printed triboelectric nanogenerator structure towards suitable energy. • Multi-unit TENG devices paves the way as a sustainable power source. • A self-powered sensor for determination of proper hand strengthing activity. [ABSTRACT FROM AUTHOR]

Sustainable, self-powered wearable devices that record physiological biosignals are essential in personalized health monitoring but have yet to be achieved. Here a novel, self-powered, MXene-based, 3D-printed, flexible, and integrated wearable system for continuous, real-time physiological biosignals monitoring is proposed, developed, characterized, and validated. The system contains power-efficient triboelectric nanogenerators (TENG), highly sensitive pressure sensors, and multifunctional circuitry. MXene, with distinctive electronegative and conductive characteristics, is the core material and is amenable to 3D-printing. MXene is coupled with a skin-like Styrene-ethylene-butylene-styrene (SEBS) substrate with a positive triboelectric property and high stretchability. This self-powered physiological sensing system exhibited a power output of ~ 816.6 mW m−2, a sensitivity of ~ 6.03 kPa−1, a low detection limit of ~ 9 Pa, and a fast response time of ~ 80 ms, enabling continuous radial artery pulse (RAP) waveform monitoring without external power. Its continuous, on-demand, fully self-powered RAP monitoring and wireless data and power transmission through near-field communication are demonstrated. This is the first report of a wearable system for continuous and real-time physiological biosignals monitoring fully powered by human motion, signaling exciting potential in the field. [Display omitted] • Reporting a novel, 3D-printed, and integrated self-powered wearable sensing system for real-time vital signs monitoring. • The system is capable of continuous, real-time, on-demand, and fully self-powered radial-artery-pulse waveform monitoring. • MXene, a 2D transition material with distinctive electronegative and conductive characteristics, is the used core material. • The system is capable of wireless and continuous power and data transmission on-demand via NFC technology. [ABSTRACT FROM AUTHOR]

Harvesting mechanical energy based on the triboelectric and electrostatic concepts is a very new and extremely fast growing technology. The effect of time in which a typical energy generation cycle occurs is deeply studied here. Three set of contact key with nano-structured triboelectric surfaces, each including a magnetic and fingertip driving mechanisms, were developed and studied. The system is represented by an equivalent circuit, validated by finite element method and the relative mathematical description, and then studied by numerical analysis. It is shown how the relative speed of triboelectric surfaces affects the peak instantaneous and the average power, which is related to the electrostatic phase of energy generation. However, evidences show that the contact/release speed may also influence the charge separation amount, i.e. triboelectric phase of energy generation, which needs to be investigated too. [ABSTRACT FROM AUTHOR]

We present a newly designed self-powered identification system based on sliding electrification by combination of a barcode fabricated by gratings with intervals of different widths between each other and a reader consists of a layer of FEP film and a strip electrode. Introducing a reference interval and a baseline, an encoding method was established by calculating the ratio of time spent for sliding across the strip electrode and the one for the reference interval. Sliding across a reader at a constant speed rate from 10 mm/s to 100 mm/s, even swiping a card by human hands, coded information by gratings with intervals of different widths was successfully identified. This work demonstrates the practicability of a self-powered, triboelectric-based identification system, and indicates its potential applications in laboratories, libraries, and industry. [ABSTRACT FROM AUTHOR]