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Intelligent interaction technology based on advanced sensing units has become a research hotspot. In this paper, an intelligent interaction system (IIS) based on a multimodal conformal triboelectric nanogenerator patch (MCTP) is reported for sports monitoring and life promotion of the disabled. This IIS consists of a cloud-based smart sports recognition program and a smart life application. The porous micro-reinforced structure of polyurethane (PU) Sponge & Ecoflex, and the surface modification of PTFE by coating it with MXene endows the MCTP with excellent electrical properties. It shows good angle and force sensitivities of 1.1 V/° and 1.61 V/N, respectively, and has an ultra-fast response time of 15 ms, meeting the needs of human motion monitoring. The MCTP can also capture the mechanical energy, producing a maximum output power of 139 µW. Compared with the commercial inertial measuring unit (IMU), the MCTP shows better consistency in human joint angle sensing. A precise analysis of wheelchair curling sports monitoring points is achieved by combining the MCTP and the human anatomy model. The cloud-based smart sports recognition program utilizes machine learning to achieve visual feedback on the three throwing technologies of draw, takeout and clearing. In addition, the developed smart life application uses a high-sensitivity MCTP-sensor array design to achieve a variety of smart home interactions through simple finger touches. Overall, the IIS integrates the three major functions of smart sports sensing, energy capture, and smart home control, providing important application prospects in the fields of smart sports and human-computer interaction for the disabled. [ABSTRACT FROM AUTHOR]

Highlights: The basic information of triboelectric nanogenerator (TENG), the power conversion process, and key points of the marine energy harvesting TENGs was introduced in detail. An in-depth introduction and analysis of relevant research with the marine energy harvesting were conducted through gradient classification. This review not only provided a deeper summary of the latest research progress, discoveries, and challenges, but also made a rational outlook on solutions to related issues and future development directions. The large-scale use of ample marine energy will be one of the most important ways for human to achieve sustainable development through carbon neutral development plans. As a burgeoning technological method for electromechanical conversion, triboelectric nanogenerator (TENG) has significant advantages in marine energy for its low weight, cost-effectiveness, and high efficiency in low-frequency range. It can realize the efficient and economical harvesting of low-frequency blue energy by constructing the floating marine energy harvesting TENG. This paper firstly introduces the power transfer process and structural composition of TENG for marine energy harvesting in detail. In addition, the latest research works of TENG on marine energy harvesting in basic research and structural design are systematically reviewed by category. Finally, the advanced research progress in the power take-off types and engineering study of TENG with the marine energy are comprehensively generalized. Importantly, the challenges and problems faced by TENG in marine energy and in situ electrochemical application are summarized and the corresponding prospects and suggestions are proposed for the subsequent development direction and prospects to look forward to promoting the commercialization process of this field. [ABSTRACT FROM AUTHOR]

The triboelectric nanogenerators (TENGs) based on polyvinylidene fluoride (PVDF) have attracted significant attention due to their high energy conversion efficiency and strong flexibility. Indeed, the TENGs with higher electrical performance and stronger mechanical robustness are more desirable. In this context, we design and fabricate TENGs based on nanofiber (NF) layer of Poly(vinylidene fluoridehexafluoropropylene) (PVDF-HFP), a copolymer of PVDF with better mechanical properties, in which the enhancement of dielectric constant and specific surface area is achieved by incorporation of BaTiO3 into PVDF-HFP NFs using electrospinning. The results show that the TENGs demonstrates superior electrical performance. The optimized TENG exhibits an open-circuit voltage (VOC) of 432 V, a short-circuit current (ISC) of 44.2 µA, and a maximum power density (Pd) of 2.25 W/m2. Practical applications of the optimized TENG are also demonstrated, including its use as power source, cylindrical rotating energy harvester and self-powered wearable sensor. The findings give insights into the fabrication, performance and application of the TENGs based on BaTiO3-incorporated PVDF-HFP NFs, offering promising solutions for energy harvesting and diverse applications. [ABSTRACT FROM AUTHOR]

We studied the effect of surface functionalization with amine group-containing molecules on the electrical output performance of triboelectric nanogenerators (TENGs). The surface functionalization with an amine (–NH2) group featuring cysteamine, (3-aminopropyl)triethoxysilane (APTES), N-[3-(trimethoxysilyl)propyl]ethylenediamine (AHAPS), and N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMPTA) was performed to modify the surface. The formation of self-assembled monolayers (SAM) on the substrates was confirmed by contact angle measurements, x-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). After surface functionalization with cysteamine molecules, the power output of the TENG was improved by about 3.3 times, ascribed to the boosted charge transfer from electron-donating amine groups compared with the pristine Au surface. Furthermore, the effect of the number of amine groups in the molecule on the electrical output was studied by modifying the polyethylene terephthalate/indium tin oxide (PET/ITO) surface with APTES, AHAPS, and TMPTA with one, two, and three amine groups, respectively. Relative to the pristine PET/ITO-based TENG, the induced charge density gradually increased by 4.5, 7, and 17 times as the number of amine groups increased in the functionalized samples. The peak power density of the TMPTA-based TENG was about 8.4 times higher than the APTES-based TENG, which is attributed to the presence of amine group-containing molecules that have stronger electron-donating strength on the surface, which enhances charge transfer at the interface between the triboelectrification layers. [ABSTRACT FROM AUTHOR]

A unique oscillating wind-driven triboelectric nanogenerator (OWTENG) based on the sphere's vortex-induced vibration (VIV) behavior is proposed in this study, which can harvest wind energy across a multitude of horizontal directions. With the Euler-Lagrange method, the coupled governing equations of the OWTENG are established and subsequently validated by experimental tests. The vibrational properties and output performance of the OWTENG for varying wind speeds are analyzed, demonstrating its effectiveness in capturing wind energy across a broad range of wind speeds (from 2.20 m/s to 8.84 m/s), and the OWTENG achieves its peak output power of 106.3 µW at a wind speed of 5.72 m/s. Furthermore, the OWTENG maintains a steady output power across various wind directions within the speed range of 2.20 m/s to 7.63 m/s. Nevertheless, when the wind speed exceeds 7.63 m/s, the vibrational characteristics of the sphere shift based on the wind direction, leading to fluctuations in the OWTENG's output power. This research presents an innovative approach for designing vibrational triboelectric nanogenerators, offering valuable insights into harvesting wind energy from diverse directions and speeds. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) made from biocompatible materials serve as promising integrated power sources for portable wearable electronics due to many advantages such as lightweight, high flexibility, simple technique, and excellent breathability. In this work, we report the fabrication of electrospun polycaprolactone micro-nanofiber films (s-PCL) and convex-microdome-patterned polydimethylsiloxane (c-PDMS) utilizing electrospinning and micromolding techniques. These materials, s-PCL and c-PDMS, are utilized as positively and negatively charged tribosurfaces, respectively, in the development of a bioTENG device. The developed TENG device can generate a superior power output of 2 mW with an open-circuit voltage (VOC) of 188 V and short-circuit current (ISC) of 18.5 µA, even under a low triggering frequency of 5 Hz. In addition, TENG possesses outstanding durability and output performance stability over a continuous operation of nearly 16,000 cycles. Furthermore, the TENG demonstrates its capacity to harvest mechanical energy and convert it into electricity, capable of directly illuminating more than 100 LEDs. The electrospun s-PCL- and c-PDMS-based TENG can be considered for self-powdered wearable devices attached to fingers, wrists, feet, and other human body parts. [ABSTRACT FROM AUTHOR]

Although biopolymers have been widely utilized as triboelectric materials for the construction of self-powered sensing systems, the annihilation of triboelectric charges at high temperatures restricts the output signals and sensitivity of the assembled sensors. Herein, a novel chitosan/montmorillonite/lignin (CML) composite film was designed and employed as a tribopositive layer in the assembly of a self-powered sensing system for use under hot conditions (25–70°C). The dense contact surface resulting from the strong intermolecular interaction between biopolymers and nanofillers restrained the volatilization of induced electrons. The optimized CML-TENG delivered the highest open-circuit voltage (Voc) of 262 V and maximum instantaneous output power of 429 mW/m2. Pristine CH-TENG retained only 39% of its initial Voc at 70°C, whereas the optimized CM5L3-TENG retained 66% of its initial Voc. Our work provides a new strategy for suppressing the annihilation of triboelectric charges at high temperatures, thus boosting the development of self-powered sensing devices for application under hot conditions. [ABSTRACT FROM AUTHOR]

The highly sensitive and power efficient tactile sensors can provide grippers with vertical and shear forces from interactions with objects. In an ocean environment with low visual distance and high noise, sea otters can rely on their palms to accurately identify and grasp target objects without damage. Inspired by the structure of the sea otter's palm, this paper proposes a distributed liquid metal-based three-dimensional biomimetic underwater triboelectric palm-like tactile sensor (UPTS) for feedback-controlled grippers. The device is mainly composed of a flexible shell, a flexible cover, a flexible support, a triboelectric sensing unit and a fixed shell. The force acting on the flexible cover causes the flexible cover and sensing unit to deform, so that the sensing unit undergoes a contact-separation process, thereby generating an electrical signal. UPTS has the capability to identify the magnitude and direction of force, with a direction recognition error angle within 5 degrees. Additionally, it can distinguish the hardness and shape of objects, achieving an accuracy rate of 100% and 99.75% respectively for the tested objects. The results indicate that UPTS can provide force feedback for underwater grippers, thereby assisting the grippers in better completing salvage task. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) is an electron-withdrawing material that is widely used in triboelectric nanogenerators (TENGs). However, PDMS has poor mechanical properties after curing and is easily damaged when subjected to long-term workloads. Thus, the long-term stable operation of TENGs under mechanical deformation cannot be guaranteed. In this work, multiple hydrogen bonds and aromatic disulfide bonds were introduced into PDMS elastomers. These elastomers exhibited high toughness (a tensile strength of 1.91 MPa and an elongation at break of 340%), good recyclability, and room-temperature self-healing properties (healing efficiency of 96.4% in 24 h). Recyclable sandwich-like triboelectric nanogenerators with excellent electrical output performance (13.5 V) and room-temperature self-healing performance (24 h, 98% recovery of self-generating performance) were prepared by utilizing the hydrogen bonding between the PDMS elastomer and MXene. The work reported herein offers theoretical guidance and a compelling strategy for developing high-performance TENG negative friction layers. [ABSTRACT FROM AUTHOR]

Highlights: Comprehensively reviewed the progress in research on graphene electrode-based triboelectric nanogenerators (TENGs) from two dimensions, including precision processing methods of graphene electrodes and applications of TENGs. Discussed the various applications of graphene electrode-based TENGs in different scenarios, as well as the ways in which graphene electrodes enhance the performance of TENGs. Offered a prospective discussion on the future development of graphene electrode-based TENGs, with the aim of promoting continuous advancements in this field. With the continuous development of wearable electronics, wireless sensor networks and other micro-electronic devices, there is an increasingly urgent need for miniature, flexible and efficient nanopower generation technology. Triboelectric nanogenerator (TENG) technology can convert small mechanical energy into electricity, which is expected to address this problem. As the core component of TENG, the choice of electrode materials significantly affects its performance. Traditional metal electrode materials often suffer from problems such as durability, which limits the further application of TENG. Graphene, as a novel electrode material, shows excellent prospects for application in TENG owing to its unique structure and excellent electrical properties. This review systematically summarizes the recent research progress and application prospects of TENGs based on graphene electrodes. Various precision processing methods of graphene electrodes are introduced, and the applications of graphene electrode-based TENGs in various scenarios as well as the enhancement of graphene electrodes for TENG performance are discussed. In addition, the future development of graphene electrode-based TENGs is also prospectively discussed, aiming to promote the continuous advancement of graphene electrode-based TENGs. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have emerged as a promising technology to harvest electrical energy from natural motions such as human movement, wind, and water flow. Although TENGs show significant potential in small-scale applications, developing large-scale TENGs capable of generating high power remains a significant challenge. Several factors that can affect the performance of large-scale TENGs are being investigated to overcome this challenge, including the size and configuration of dielectric materials. This study optimizes dielectrics regarding surface area, thickness, and multicell configuration to improve harvested electrical power density in large-scale TENGs. In the studies, glass fiber was used as the positive dielectric, and multipurpose white silicone was used as the negative dielectric because of their high tribo-potential, durability, and easy accessibility. In the size optimization phase, dielectric thicknesses and surface areas that provide the maximum power density were determined. Subsequently, horizontal and vertical multicell configurations were examined to efficiently integrate size-optimized dielectrics. The results reveal that large-scale TENGs with vertical multicell configurations can achieve high and usable energy density for electronics. The findings provide valuable insight into the development of large-scale TENGs with advanced power generation capabilities. [ABSTRACT FROM AUTHOR]

Ocean wave energy is a significant and promising source of renewable energy. However, the energy harvesting is challenging due to the multi-directional nature of waves. This paper proposes a magnetic-field-assisted triboelectric nanogenerator (MFA-TENG) for harvesting multi-directional wave energy. By incorporating a magnetic field, the planar motion of the pendulum is converted into spatial motion, increasing the triggering of multilayered TENG (M-TENG) and enhancing the output energy of the MFA-TENG. Experimental results demonstrate that the output energy of the MFA-TENG is increased by 73% by utilizing the magnetic field. Moreover, a spring model based on the origami-structured M-TENG is established to analyze the effect of different equivalent stiffnesses on the performance of the M-TENG, aiming to obtain optimal output performance. The results showcase the impressive output performance of the M-TENG, generating outputs of 250 V, 18 µA, and 255 nC. Furthermore, the proposed MFA-TENG effectively harvests multi-directional wave energy under water-wave driven conditions. This study significantly enhances the ability of the MFA-TENG to harvest multi-directional wave energy and presents a promising approach for self-powered marine monitoring in the future. [ABSTRACT FROM AUTHOR]

Experimental and simulation studies demonstrated that the initial voltage setting significantly influences the open-circuit voltage (VOC) in triboelectric nanogenerators (TENGs). Utilizing diode configurations, we consistently observed two distinct VOCs independent of the initial settings. A lower VOC corresponded to the surface voltage (VSurface), while a higher VOC was amplified by the product of the VSurface and the TENG's characteristic impedance ratio. Notably, a lower measurement system capacitance provided a more precise representation of the inherent characteristics of the TENG. Conversely, an increase in system impedance led to a convergence of the two VOCs and a reduction in their magnitudes relative to VSurface. These findings suggest that optimizing the initial/repeated charge balancing and minimizing capacitive loads are crucial for maximizing TENG output power in practical applications. [ABSTRACT FROM AUTHOR]

In recent years, there has been a surge in interest surrounding the development of chitosan (CS)-based triboelectric nanogenerators (TENG) for powering attachable/portable devices. Despite numerous strategies aimed at enhancing their efficiency, the selection of acid solvent has remained largely unexplored. In this study, various acids, including acetic (CH3COOH), succinic (C4H6O4), and citric (C6H8O7) acids, were investigated for their impact on mechanical and electrical output signals. Remarkably, the choice and concentration of acid were found to significantly influence performance. Specifically, employing citric acid rendered the CS solid film more pliable and yielded the highest output signal at optimal concentration levels. Under optimized conditions, the CS-TENG exhibited an open-circuit voltage output (VOC) of 157 V and short-circuit current output (ISC) of 53 µA—more than triple that of pristine CS-TENG. Mechanistic insights into electrical generation have been elucidated, underscoring the importance of solvent selection in CS TENG fabrication. These findings underscore the potential for tailored acid solvent selection to advance specialized applications in the field. [ABSTRACT FROM AUTHOR]

The energy harvesting technology for the ubiquitous natural wind enables a desirable solution to the issue of distributed sensors in the bridge environmental sensing Internet of Things (IoT) system being restricted to conventional energy supply. In this work, a self-powered system based on a compact galloping piezoelectric-triboelectric energy harvester (GPTEH) is developed to achieve efficient wind energy harvesting. The GPTEH is constructed on the prototype of a cantilever structure with piezoelectric macro-fiber composite (MFC) sheets and a rectangular bluff body with triboelectric nanogenerators (TENGs). Through a special swing-type structural design with iron blocks inside the bluff body, the GPTEH exhibits preferable aerodynamic behavior and excellent energy conversion efficiency, compared to conventional cantilever kind of piezoelectric wind energy harvester (PWEH). The GPTEH also demonstrates the capability of high output power density (PEH of 23.65 W m−2 and TENG of 1.59 W m−2), superior response wind speed (about 0.5 m s−1), and excellent long-term stability (over 14000 cyclic tests). Furthermore, a power management system is developed to efficiently utilize the output energy from GPTEH to power the sensors and wirelessly transmit environmental data to the terminals. The proposed GPTEH powered system exhibits a great potential for the bridge environmental monitoring and IoT technologies. [ABSTRACT FROM AUTHOR]

Screen sensors are the most commonly used human-machine interfaces in our everyday life, which have been extensively applied in personal electronics like cellphones. Touchless screen sensors are attracting growing interest due to their distinct advantages of high interaction freedom, comfortability, and hand hygiene. However, the material compositions of current touchless screen sensors are rigid and fragile, hardly meeting the needs of wearable and stretchable on-skin electronics development. Additionally, these touchless screen sensors are also restricted by high power consumption, limited gesture types of recognition, and the requirement of light conditions. Here, we report a stretchable on-skin touchless screen sensor (OTSS) enabled by an ionic hydrogel-based triboelectric nanogenerator (TENG). Compared with current touchless screen sensors, the OTSS is stretchable, self-powered, and competent to recognize diverse gestures by making use of charges naturally carried on fingers without the need of sufficient light conditions. An on-skin noncontact screen operating system is further demonstrated on the basis of the OTSS, which could unlock a cellphone interface in touchless operation mode on the human skin. This work for the first time introduces the on-skin touchless concept to screen sensors and offers a direction to develop new-generation screen sensors for future cellphones and personal electronics. [ABSTRACT FROM AUTHOR]

Human–machine interactions (HMIs) have advanced rapidly in recent decades in the fields of healthcare, work, and life. However, people with disabilities and other mobility problems do not have corresponding high-tech aids for them to enjoy the convenience of HMIs. In this paper, we propose a sensor with a wave-shaped (corrugated) electrode embedded in a friction layer, which exhibits high sensitivity to skin fold excitation and enormous potential in HMIs. Attributing to the wave-shaped electrode design, it has no built-in cavities, and its small size allows it to flexibly cope with folds at different angles. By specifying the carbon nanotube hybrid silicone film as the electrode layer material and silicone film as the friction layer, good electrical output performance, tensile properties, and biocompatibility can be achieved. Then, the sensor is tested on various joints and skin folds of the human body, the output signals of which can be distinguished between normal physiological behavior and test behavior. Based on this sensor, we designed a medical alarm system, a robotic arm assistive system, and a cell phone application control system for the disabled to help them in the fields of healthcare, work, and life. In conclusion, our research presents a feasible technology to enhance HMIs and makes a valuable contribution to the development of high-tech aids for the disabled. [ABSTRACT FROM AUTHOR]

An enormous number of wireless sensing nodes (WSNs) are of great significance for the Internet of Things (IoT). It is tremendously prospective to realize the in-situ power supply of WSNs by harvesting unutilized mechanical vibration energy. A harmonic silicone rubber triboelectric nanogenerator (HSR-TENG) is developed focusing on ubiquitous constant working frequency machinery. The unique design of the strip serving as a flexible resonator realizes both soft contact and high and broadband output. The significant factors influencing the 1st-order vibration mode of the strip are developed for realizing the harmonic frequency adaptation to external vibration. The surface treatment of the strip improves the output performance of HSR-TENG by 49.1% as well as eliminates the adhesion effect. The HSR-TENG is able to achieve a voltage output bandwidth of 19 Hz under a vibration strength of 3.0, showing its broadband capability. The peak power density of 153.9 W/m3 is achieved and 12 × 0.5 W light-emitting diodes (LEDs) are successfully illuminated by the HSR-TENG. It can continuously power a temperature sensor by harvesting the actual compressor vibration energy. In brief, the HSR-TENG provides a promising way for constant frequency vibration energy harvesting, so as to achieve in-situ power supply for the WSNs in the vicinity. [ABSTRACT FROM AUTHOR]

The ocean, with its highly variable and complex meteorological conditions, harbors enormous renewable resources. Triboelectric nanogenerators (TENGs), which possess unique advantages, show exciting prospects in water wave energy collection. How to design and optimize TENGs to cover all characteristic water wave energies and achieve efficient energy utilization is emergent. In this paper, we carefully designed and fabricated a columnar multi-layer sliding TENG (CMLS-TENG) that can harvest water wave energy independent of wave height and direction. Drive rods with a hollow acrylic spherical shell were introduced to deliver wave energy, ensuring that the CMLS-TENG can work in all directions from 0° to 360°. Based on the sliding structure, switching the optimized CMLS-TENG is independent of wave heights. The optimized CMLS-TENG can achieve a total power density of 730 mW/m3 at a wave height of only 4.8 cm regardless of wave direction, which can illuminate multiple light-emitting diodes (LEDs) to provide lighting and provide power to a watch and a hygrometer for temperature and humidity monitoring. This work provides new choices and hopes for the effective collection of full-range water wave energy. [ABSTRACT FROM AUTHOR]

In the time of Internet of Things (IoT), alternating current electroluminescence (ACEL) has unique advantages in the fields of smart display and human–computer interaction. However, their reliance on external high-voltage AC power supplies poses challenges in terms of wearability and limits their practical application. This paper proposed an innovative scheme for preparing a feather triboelectric nanogenerator (F-TENG) using recyclable and environmentally friendly material. The highest open-circuit voltage, short-circuit current, and transferred charge of SF6-treated F-TENGs can reach 449 V, 63 µA, and 152 nC, which enables easy lighting of BaTiO3-doped ACEL devices. Using a human electrical potential, a single-electrode F-TENG is combined with ACEL device for self-powered fingerprint recognition display. These works achieve self-powered flexible wearable ACEL devices, which are not only efficient and portable but also have good application prospects in the human–computer interaction, functional displays, and wearable electronic devices. [ABSTRACT FROM AUTHOR]

We investigated the polarity dependence of a capacitive energy management circuit in a triboelectric nanogenerator (TENG) power system. In a half-wave rectifying circuit, the Simulation Program with Integrated Circuit Emphasis and analytical models show that the charge dump to the load varied depending on the polarity of the rectifying circuit even with the same charge output from TENG. Depending on the polarity of the rectifying circuit, a fast saturation of the direct current (DC) output voltage or a high DC output voltage was obtained. Experiments with a half-wave rectifier and Bennet doubler confirmed our simulation and theoretical results. The charge dump from the minimum capacitance of the separated TENG to the load capacitance and the charge dump from the maximum capacitance of the contacted TENG to the load resulted in asymmetric charging behavior. We concluded that it is necessary to analyze the TENG and the capacitive energy management circuit as a single system rather than considering them as independent units in the rectifying circuit of the TENG. This work can provide insights for the design of triboelectric energy harvesting systems. [ABSTRACT FROM AUTHOR]

Harvesting bio-kinetic energy using a triboelectric nanogenerator (TENG) is one of the promising routes to solve the sustainable energy supply problem for wearable electronics. However, additional materials, complex fabricating processes or specific mechanical structures are needed for existing TENGs to harvest bio-kinetic energy. Besides, they need to be tightly attached to the human body, which may result in detachment and malfunction under tense human motion. Herein, an intrinsic epidermal electrode-based TENG (E-TENG) is proposed to harvest human walking energy. The wearing shoes and ground are used as tribo-materials, and the human epidermis is used as the back electrode of the E-TENG. Compared with the traditional TENGs, the E-TENG does not need any additional tribo-materials and complex mechanical structures. Under optimal conditions, the voltage output of E-TENG can reach 914 V. E-TENG has been used as a self-powered warning sensor and pedometer sensor for demonstration. Furthermore, E-TENG based self-powered wireless sensor system has been developed using a newly designed micro energy electronic switch (MEES). Ambient ultraviolet intensity, temperature and humidity information can be monitored and then transmitted to mobile phone every 3.5 min, demonstrating great potential for widespread wearable applications. [ABSTRACT FROM AUTHOR]

In view of the increasing energy shortage and environmental pollution, the collection of friction charges to achieve the conversion of various natural energies and provide in-situ cathodic protection for metals is a significant challenge. Here, we designed a dual device-structure TENG composite array with the triboelectric layer of linear siloxane-modified polyurethane (PU) coating. This array could achieve a comprehensive collection for multiple forms of nature energy and cathodic protection of metals in multi-weather conditions. For one thing, the wave-mode TENG based on tanker structure could collect wave energy and showed the output performance with a short-circuit current of 15.5 µA. For another hing, the droplet-mode TENG based on arc-shaped surface structure could collect raindrop kinetic energy and showed the output performance with a short-circuit current of 16.3 µA. Notably, the parallel array of wave-mode TENG (W-TENG) and droplet-mode TENG (D-TENG) could simultaneously collect wave energy and raindrop kinetic energy, which showed a short-circuit current of 30.7 µA. Besides, a self-powered a cathodic protection system powered by the dual structure TENG array is assembled and the open-circuit potential drop of the carbon steel connected with the TENG array is about 450 mV. Compared with cathodic protection system powered by single structure TENG, the composite array could provide more effective corrosion resistance for marine equipment in rainy weather. Due to the characteristic for comprehensive collection of nature energy, the anti-corrosion system supplied by TENG parallel array possesses great application potential in the all-weather corrosion protection of metal machinery under complex marine conditions. [ABSTRACT FROM AUTHOR]

In the era of advanced wearable electronic devices, the triboelectric nanogenerators (TENGs) as energy harvesting and self-powered sensing units hold great promise. Selecting appropriate triboelectric material is the crucial factor to optimize the performance of TENG, while polytetrafluoroethylene (PTFE) stands out as a highly versatile option among the various materials. In this study, we present an ultrafine nanofibrous PTFE (NF-PTFE) films prepared by novel in-situ fibrillation strategy as the triboelectric material in TENG devices. The innovative processing methodology facilely addresses the dilemma between high porosity and fine pore size of traditional porous PTFE films, meanwhile achieves exceptional mechanical strength, hydrophobicity, air permeability, and chemical resistance of the films. With the integration of nanofibrous PTFE films into contact-separation mode TENG and droplet-based TENG, these devices realize the peak electrical output of 131 V/10.8 µA and 54 V/14 µA with great durability, which surpass the performance of TENGs using traditional expanded PTFE films. Furthermore, a smart glove capable of recognizing hand gestures is proposed, which demonstrates the versatility, flexibility, and practicality of this material for potential use in smart devices. This reported NF-PTFE film provides insights for the design of high-performance TENG device for advanced wearable electrical applications. [ABSTRACT FROM AUTHOR]

Highlights: A self-powered and highly sensitive tribo-label-sensor is proposed as the substitution of infrared sensor for addressing current issues in label printer. Tribo-label-sensor shows higher integrability, sensitivity, reliability and universality than traditional infrared sensor for label identification, positioning and counting. Label-sensor is an essential component of the label printer which is becoming a most significant tool for the development of Internet of Things (IoT). However, some drawbacks of the traditional infrared label-sensor make the printer fail to realize the high-speed recognition of labels as well as stable printing. Herein, we propose a self-powered and highly sensitive tribo-label-sensor (TLS) for accurate label identification, positioning and counting by embedding triboelectric nanogenerator into the indispensable roller structure of a label printer. The sensing mechanism, device parameters and deep comparison with infrared sensor are systematically studied both in theory and experiment. As the results, TLS delivers 6 times higher signal magnitude than traditional one. Moreover, TLS is immune to label jitter and temperature variation during fast printing and can also be used for transparent label directly and shows long-term robustness. This work may provide an alternative toolkit with outstanding advantages to improve current label printer and further promote the development of IoT. [ABSTRACT FROM AUTHOR]

Cellulose-based composites typically have poor water resistance because they are cross-linked through non-covalent bonds, such as hydrogen bonds. Herein, furan group was grafted onto sisal microcrystalline cellulose fiber (F-MSF) and a dynamic thermally reversible cross-linked network structure was formed with maleimide modified CaCu3Ti4O12 (D-CCTO) to obtain recyclable D-CCTO/F-MSF composites (DFF) through the Diels-Alder reaction. The results showed that the mechanical properties of DFF composites were improved due to the improvement of the cross-linked structure between D-CCTO and F-MSF. At 1 wt% D-CCTO content, the tensile strength of DFF was 5.53 MPa, which increased by 346% compared with that of pure MSF. At 5 wt% D-CCTO content, the short-circuit current, open circuit voltage, transferred charge of DFF-based triboelectric nanogenerators (DF-TENG) were 3.2 µA, 85 V and 26 nC, respectively. Additionally, the DF-TENG was able to maintain its electrical performance of more than 60% at an ambient humidity of 90% and was able to light up more than 30 LED bulbs. This research provides new insights into addressing the challenge of poor water resistance in conventional cellulose-based composites, while also designing a recyclable TENG device that can harvest energy in high humidity environments. [ABSTRACT FROM AUTHOR]

Fluorinated polymers exhibit a unique combination of attributes, including chemical inertness, low surface energy, exceptional weather resistance, and intriguing electrical properties. This mini review provides an overview of recent advancements in the research of fluorinated polymers, highlighting the development of synthetic strategies for novel fluorinated polymers and their diverse applications in various fields. Traditional fluorinated polyolefins can be modified through chemical methods to produce functional materials. Copolymerization of fluorinated olefins with non-fluorinated monomers effectively addresses synthesis challenges, yielding main-chain fluoro-containing polymers with specific functional groups. Additionally, recent studies have revealed that free radical (co)polymerization of fluorinated (meth)acrylate monomers leads to new fluorinated polymers with enhanced solubility, processability, and structural diversity. Capitalizing on these new synthetic strategies, a range of fluorinated polymer materials has been developed for a multitude of applications, including flexible electrodes, alternating current (AC) electroluminescent devices, energy storage capacitors, triboelectric nanogenerators, and lithium batteries. With their customized structures and excellent properties, fluorinated polymers hold significant promise to uncover more potential applications in the era of flexible and wearable electronics. [ABSTRACT FROM AUTHOR]

Metal corrosion causes billions of dollars of economic losses yearly. As a smart and new energy-harvesting device, triboelectric nanogenerators (TENGs) can convert almost all mechanical energy into electricity, which leads to great prospects in metal corrosion prevention and cathodic protection. In this work, flexible TENGs were designed to use the energy harvested by flexible polydimethylsiloxane (PDMS) films with ZrB2 nanoparticles and effectively improve the dielectric constant by incorporating ZrB2. The open-circuit voltage and short-circuit current were 264 V and 22.9 µA, respectively, and the power density of the TENGs reached 6 W·m−2. Furthermore, a self-powered anti-corrosion system was designed by the rectifier circuit integrated with TENGs, and the open-circuit potential (OCP) and Tafel curves showed that the system had an excellent anti-corrosion effect on carbon steel. Thus, the system has broad application prospects in fields such as metal cultural relics, ocean engineering, and industry. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) are highly promising energy-harvesting devices that exhibit considerable potential for use in self-powered wearable electronics. Nano/microfillers and surface microstructure modification have been proposed to improve the triboelectric performance of TENGs. In this work, performance-enhanced flexible polydimethylsiloxane (PDMS) was developed through bi-material (reduced graphene oxide/fluorinated ethylene propylene, rGO/FEP) modification and filtration-membrane-patterned surface microstructure. The rGO/FEP with high charge-inducing and -trapping capabilities can be used as the dielectric-enhanced filler for improving triboelectricity. Ordered micro-dents of 5–50 µm are created on the modified PDMS surface with an increased contact area of TENG. Compared with the pure PDMS, the modified PDMS film-based TENG could deliver a substantial enhancement in power density (0.87 mW cm−2) by 28 times. Further, the versatility of this device is demonstrated in human activity monitoring and capacitor charging. This work provided a simple, high-tunability, and scalable approach for improving the output performance of TENGs for biomechanical energy-harvesting devices that can be integrated into self-powering wearable electronics. [ABSTRACT FROM AUTHOR]

The rapid development of wearable electronic products brings challenges to corresponding power supplies. In this work, a thermally stable and stretchable ionogel-based triboelectric nanogenerator (SI-TENG) for biomechanical energy collection is proposed. The ionic conductivity of the ionogel increased to 0.53 S·m−1 through optimal regulation of the amount of aminoterminated hyperbranched polyamide (NH2-HBP), which also has high strain of 812%, excellent stretch recovery, and wide operating temperature range of −80 to 250 °C. The SI-TENG with this ionogel as electrode and silicone rubber both as the triboelectric layer and encapsulation layer exhibits high temperature stability, stretchability, and washability. By adding appropriate amount of nano SiO2 to triboelectric layer, the output performance is further improved by 93%. Operating in single-electrode mode at 1.5 Hz, the outputs of a SI-TENG with an area of 3 cm × 3 cm are 247 V, 11.7 µA, 78 nC, and 3.2 W·m−2, respectively. It was used as a self-charging power supply to charge a 22 µF capacitor to 1.6 V in 167 s with the palm patting and then to power the electronic calculator. Furthermore, the SI-TENG can also be used as a self-powered motion sensor to detect the amplitude and frequency of finger bending, human swallowing, nodding, and shaking of the head motion changes through the analysis of the output voltage. [ABSTRACT FROM AUTHOR]

In the context of advocating a green and low-carbon era, ocean energy, as a renewable strategic resource, is an important part of planning and building a new energy system. Triboelectric nanogenerator (TENG) arrays provide feasible and efficient routes for large-scale harvesting of ocean energy. In previous work, a spherical rolling-structured TENG with three-dimensional (3D) electrodes based on rolling motion of dielectric pellets was designed and fabricated for effectively harvesting low-frequency water wave energy. In this work, the external shape of the scalable rolling-structured TENG (SR-TENG) and internal filling amount of pellets were mainly optimized, achieving an average power density of 10.08 W·m−3 under regular triggering. In actual water waves, the SR-TENG can deliver a maximum peak power density of 80.29 W·m−3 and an average power density of 6.02 W·m−3, which are much greater than those of most water wave-driven TENGs. Finally, through a power management, an SR-TENG array with eight units was demonstrated to successfully power portable electronic devices for monitoring the marine environment. The SR-TENGs could promote the development and utilization of ocean blue energy, providing a new paradigm for realizing the carbon neutrality goal. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG) is a new cost-effective blue energy harvesting technology for its great performance in low frequency. However, many related energy harvesters operate on water surface, ignoring the ocean's depth. Herein, a chain-flipped plate TENG (CFP-TENG), consisting of longitudinally arranged repeating units, is proposed to collect wave energy. The chain structure design allows the surface wave energy to act effectively on the underwater generator. The maximum output power per unit ocean area reaches 1.5 W·m−2 at a loading resistance of 30 MΩ. Optimization of device parameters and application demonstrations are explored. Compared with previous works, the utilization rate of wave energy has been significantly improved. This work not only provides a new method to optimize the output of TENG but also makes a crucial step in promoting practical applications of TENG in renewable blue energy. [ABSTRACT FROM AUTHOR]

The triboelectric nanogenerators (TENGs), suppling power for freely mobile and distributed electronic equipment from Internet of Things, have been considered as "the energy for the new era". Research on the service behavior has become increasingly important for achieving the reliability evaluation and life prediction of TENGs, as TENGs advance from prototypes to practical applications. Due to the wide selection of materials, the diversity of device structures, and the complexity of working environment, TENGs show unique characteristics in the service behavior. These dilemmas lead to the fact that systematical summary of service behavior for TENGs is still in its infancy. Here, the progresses of the service behavior for TENGs are comprehensively reviewed from the influence of environmental factors on the service performance of TENGs to the impact of TENGs during the service on their surroundings. We summed up the performance evolution of TENGs in the real environment and the reproducibility of TENGs of which the electrical output will be restored after failure. Then, the service adaptability of TENG is systematically discussed, including the biological and environmental compatibility. Finally, the challenges and opportunities that the related research faced are proposed to promote the emerging technology from laboratory to factory. [ABSTRACT FROM AUTHOR]

The wind energy in cities cannot be exploited effectively because natural wind is unstable and complex. Therefore, a triboelectric-electromagnetic hybrid generator with swing-blade structures (SBS-TEHG) was designed to effectively harvest intermittent and continuous wind energy in an urban environment. First, the spring structure and base were considered to realize the maximum output performance of triboelectric nanogenerators. Then, the computational fluid dynamics method was applied to optimize the structure of the SBS-TEHG to improve its aerodynamic performance. The starting wind speed of the SBS-TEHG was 2 m/s, and its energy conversion efficiency was 9.04%, 159% higher than that of the SBS-TEHG without guide plates at 4 m/s. The results demonstrated that the SBS-TEHG lit 105 light-emitting diodes (LEDs) under the intermittent-wind harvesting mode at a wind frequency of 1 Hz when the single swing blade operated, while a wireless PM2.5 & PM10 sensor was powered by the SBS-TEHG after a period of operation under the continuous-wind harvesting mode. The findings of this study provide a novel solution for low-speed wind energy harvesting in cities and demonstrate the potential of SBS-TEHG as a distributed energy source. [ABSTRACT FROM AUTHOR]

Engineering materials serving in marine surroundings are inevitably corroded. The corrosive marine conditions can also be utilized to harvest kinetic ocean wave energy to solve this problem. Leveraging water-solid triboelectrification to harvest low-frequency wave energy for active anticorrosion is promising. Existing techniques are efficient in harnessing environmental energy with frequencies higher than 3 Hz, whereas the dominated ocean waves with optimal wave spectral density fluctuate from 0.45 to 1.5 Hz. Herein, we proposed a highly efficient and sustainable blue energy-powered cathodic protection (BECP) strategy by fusing water-solid triboelectric nanogenerators and cathodic protection technology. Leveraging the highly efficient triboelectrification between the moving water and hydrophobic fluorinated ethylene propylene tube, we developed the built-in power module, enabling the harvest of ocean wave energy lower than 1.5 Hz. The generated volumetric current density is 28.9 mA·m−3, 5–20 times higher than the values of the reported devices. Moreover, the proposed BECP performs comparably to conventional cathodic protection in corrosion inhibition. Significantly, the proposed approach can be easily applied to ships, buoys, and other offshore platforms to simultaneously realize blue energy harvesting and engineering material protection, providing an alternative to traditional active protection technology. [ABSTRACT FROM AUTHOR]

Dry ion-conducting elastomers (ICEs) are emerging stretchable and ionic conductive materials that are demonstrated with excellent thermal stability and great promise in multifunctional iontronic devices. Nevertheless, the poor interface between the ICEs and the dielectric material is one of the issues hindering the application of the stretchable iontronic device. Herein, a polydimethylsiloxane (PDMS) based ion-conducting elastomer with dynamic crosslinking structures is reported, which achieves the stretchability of 475% and healing efficiency of 99%. More importantly, a robust interface bonding can be generated between the electrode and the dielectric material, which is beneficial to enhance the performance and lifespan of the flexible iontronic devices. Using this PDMS based ICE as the electrode and PDMS as the dielectric material, two stretchable iontronic devices (triboelectric nanogenerator and capacitive pressure sensor) are realized with overall self-healing and stretchable capabilities. These findings provide a promising strategy to achieve integrate stretchable iontronics or electronics with a robust interface between the electrode and dielectric materials. [ABSTRACT FROM AUTHOR]

As extremely important physiological indicators, respiratory signals can often reflect or predict the depth and urgency of various diseases. However, designing a wearable respiratory monitoring system with convenience, excellent durability, and high precision is still an urgent challenge. Here, we designed an easy-fabricate, lightweight, and badge reel-like retractable self-powered sensor (RSPS) with high precision, sensitivity, and durability for continuous detection of important indicators such as respiratory rate, apnea, and respiratory ventilation. By using three groups of interdigital electrode structures with phase differences, combined with flexible printed circuit boards (FPCBs) processing technology, a miniature rotating thin-film triboelectric nanogenerator (RTF-TENG) was developed. Based on discrete sensing technology, the RSPS has a sensing resolution of 0.13 mm, sensitivity of 7 P·mm−1, and durability more than 1 million stretching cycles, with low hysteresis and excellent anti-environmental interference ability. Additionally, to demonstrate its wearability, real-time, and convenience of respiratory monitoring, a multifunctional wearable respiratory monitoring system (MWRMS) was designed. The MWRMS demonstrated in this study is expected to provide a new and practical strategy and technology for daily human respiratory monitoring and clinical diagnosis. [ABSTRACT FROM AUTHOR]

Using stretchable nanogenerators to obtain disordered mechanical energy from the environment is an ideal way to realize wearable power supply equipment and self-power electronic devices, and alleviate the energy crisis. It is of great significance to integrate the stretchability into the nanogenerator, which can fit the complex shape of the target object better and is well suitable for wearable electronics. When applied to the human body, it can directly harvest human body mechanical energy to power wearable electronic devices and get rid of the trouble of charging. This paper systematically reviewed nanogenerators in stretchability, focusing on stretchable triboelectric nanogenerators, stretchable piezoelectric nanogenerators, and stretchable hybrid nanogenerators. Their physical mechanism, material selection, structure design, and output performance are discussed in detail. It is concluded that the fabrication methods of various devices can be broadly categorized into the two most important device types, namely fiber-like and planar. A detailed analysis of representative work and the latest progress in the past decade is performed. It is most important that excellent stretchability and high-power output are the key point to realize application value of stretchable nanogenerators. In addition, we discuss opportunities and challenges, as well as future development direction of stretchable nanogenerators. [ABSTRACT FROM AUTHOR]

The development and utilization of marine blue energy has become the focus of current research. A drawstring triboelectric nanogenerator with modular electrodes (DS-TENG) is proposed to harvest wave energy. Motion displacement and water wave adaptability are improved by using the drawstring structure in the DS-TENG. Furthermore, the modular electrode design is applied to improve the durability and replaceability of the generation units. The rationality of the structure is verified by theoretical analysis, and performance experiments on the fundamental output, displacement and frequency, durability and application are carried out. The DS-TENG can achieve output performance of 98.03 nC, 3.63 µA, 238.50 V and 923.92 µW at 150 mm and 1.0 Hz. In addition, the performance drops by 6.11% after 110,000 cycles for DS-TENG durability. This paper will provide reference for the design of TENG that adapts to a wide range of wave heights. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerator (TENG) has made significant progress in wind energy harvesting. As the most advantageous rotary TENG among wind energy harvesters, the severe material wear and the output that fluctuates with wind speed seriously hinder the application of TENG wind energy harvesters. In this study, we propose a round-trip oscillation triboelectric nanogenerator (RTO-TENG) consisting of a crank transmission mechanism and a power generation unit. The RTO-TENG utilizes a simple crank transmission mechanism combined with a zigzag-laminated triboelectric nanogenerator (Z-TENG) to achieve high-performance constant output and low material wear. The crank transmission mechanism can realize the transformation from circular motion to arc reciprocating motion, converting the random wind energy into bi-directional kinetic energy, driving the vertical contact and separation of the Z-TENG. Due to the low transmission ratio (1:1) of the crank transmission mechanism and the consistent frequency of the Z-TENG contact–separation with that of the pendulum, the RTO-TENG's power generation unit (10 Z-TENGs) is insensitive to changes in wind speed, resulting in a constant and stable output response at various speeds. After 480,000 cycles, the output of RTO-TENG decreased by only 0.9% compared to the initial value of 6 µC, and the scanning electron microscopy (SEM) images of the polytetrafluoroethylene (PTFE) film showed no significant wear on the surface of the friction layer, demonstrating excellent output stability and abrasion resistance of the RTO-TENG wind energy collector's material. The equipped energy management module, based on a gas discharge tube switch, can further enhance the output performance of the RTO-TENG. After optimizing its inductor parameter L to match the load capacitor, it can charge a 220 µF load capacitor to 13.4 V in 40 s, resulting in a 298% improvement in charging speed compared to the voltage of 4.48 V without the management module. Therefore, the RTO-TENG can efficiently provide power to low-power small electronic devices for Internet of Things (IoTs), such as road traffic warning signs and thermo-hygrometers. [ABSTRACT FROM AUTHOR]

Because of its adaptive interfacial property, soft sensors/actuators can be used to perform more delicate tasks than their rigid counterparts. However, plant epidermis with a waxy cuticle layer challenges stable and high-fidelity non-invasive electrophysiology since the conventional electrodes are invasive, easily detached from plants, and require complicated setup procedures. Here, we report a bioinspired sensor and actuator created by using a conformable electrode interface as an electrical modulation unit on a Venus flytrap. Our conformable electrode, by employing an adhesive hydrogel layer, can achieve the merits of low impedance, stretchable, biocompatible, reusable, and transparent enough for normal chlorophyll activity to occur. Owing to the high sensitivity of a flytrap to a triggering mechanical stimulation, a plant sensor matrix based on flytraps has been demonstrated by capturing the stimulated action potential (AP) signals from upper epidermis, which can orient honeybee colonies by their touch during collecting nectar. Moreover, via frequency-dependent AP modulation, an autonomous on-demand actuation on a flytrap is realized. The flytrap actuator can be controlled to responsively grasp tiny objects by the modulated signals triggered by a triboelectric nanogenerator (TENG). This work paves a way of developing autonomous plant-based sensors and actuators toward smart agriculture and intelligent robots. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors have broad application prospects, such as human motion monitoring and personalized recognition. However, their applicability is limited by complex structures, low output performance, low sensitivity, and narrow measurement range. In this study, we report a single-electrode spongy triboelectric sensor (SSTS) mainly composed of spongy composite multi-walled carbon nanotubes/polydimethylsiloxane (MWCNT/PDMS) film and conductive fabric, which can simultaneously generate contact electrification and electrostatic induction coupling in a single-electrode contact-separation mode. The SSTS combines the triboelectric effect, properties of doping material, and spongy porous structure (soft sugar as a sacrificial template). An SSTS with an MWCNT content of 10 wt% and a porosity of 64% exhibits high sensitivity, a wide measurement range, and excellent linearity. It also displays two sensitivity regions (slopes): 1.324 V/kPa from 1.5 to 28 kPa in the low-pressure range and 0.096 V/kPa from 28 to 316.5 kPa in the high-pressure range, with linearities of 0.980 and 0.979, respectively. Furthermore, the SSTS delivers a high-performance output and high stability, thus enhancing the monitoring of hand pressure changes, human movement, personalized spatial recognition, and other detection tasks. This new strategy for human motion monitoring shows great potential in the healthcare fields, sports rehabilitation, and human-computer interactions. [ABSTRACT FROM AUTHOR]

Wave energy is inexhaustible renewable energy. Making full use of the huge ocean wave energy resources is the dream of mankind for hundreds of years. Nowadays, the utilization of water wave energy is mainly absorbed and transformed by electromagnetic generators (EMGs) in the form of mechanical energy. However, waves usually have low frequency and uncertainty, which means low power generation efficiency for EMGs. Fortunately, in this slow current and random direction wave case, the triboelectric nanogenerator (TENG) has a relatively stable output power, which is suitable for collecting blue energy. This article summarizes the main research results of TENG in harvesting blue energy. Firstly, based on Maxwell's displacement current, the basic principle of the nanogenerator is expounded. Then, four working modes and three applications of TENG are introduced, especially the application of TENG in blue energy. TENG currently used in blue energy harvesting is divided into four categories and discussed in detail. After TENG harvests water wave energy, it is meaningless if it cannot be used. Therefore, the modular storage of TENG energy is discussed. The output power of a single TENG unit is relatively low, which cannot meet the demand for high power. Thus, the networking strategy of large-scale TENG is further introduced. TENG's energy comes from water waves, and each TENG's output has great randomness, which is very unfavorable for the energy storage after large-scale TENG integration. On this basis, this paper discusses the power management methods of TENG. In addition, in order to further prove its economic and environmental advantages, the economic benefits of TENG are also evaluated. Finally, the development potential of TENG in the field of blue energy and some problems that need to be solved urgently are briefly summarized. [ABSTRACT FROM AUTHOR]

Highlights: This review systematically discusses the interfacial properties of cellulosic material preparation processes, top-down, bottom-up, and composite processes. The rational design strategies of cellulosic triboelectric materials are summarized in detail, and the effects of different design strategies on the surface charge characteristics and charge density of cellulosic triboelectric materials are discussed. A comprehensive review of the research progress of cellulosic triboelectric nanogenerators in the field of self-powered wearable electronics. With the rapid development of the Internet of Things and flexible electronic technologies, there is a growing demand for wireless, sustainable, multifunctional, and independently operating self-powered wearable devices. Nevertheless, structural flexibility, long operating time, and wearing comfort have become key requirements for the widespread adoption of wearable electronics. Triboelectric nanogenerators as a distributed energy harvesting technology have great potential for application development in wearable sensing. Compared with rigid electronics, cellulosic self-powered wearable electronics have significant advantages in terms of flexibility, breathability, and functionality. In this paper, the research progress of advanced cellulosic triboelectric materials for self-powered wearable electronics is reviewed. The interfacial characteristics of cellulose are introduced from the top-down, bottom-up, and interfacial characteristics of the composite material preparation process. Meanwhile, the modulation strategies of triboelectric properties of cellulosic triboelectric materials are presented. Furthermore, the design strategies of triboelectric materials such as surface functionalization, interfacial structure design, and vacuum-assisted self-assembly are systematically discussed. In particular, cellulosic self-powered wearable electronics in the fields of human energy harvesting, tactile sensing, health monitoring, human–machine interaction, and intelligent fire warning are outlined in detail. Finally, the current challenges and future development directions of cellulosic triboelectric materials for self-powered wearable electronics are discussed. [ABSTRACT FROM AUTHOR]

As a widely used security device, the electronic passworded locker is designed to protect personal property and space. However, once the password is leaked to an unauthorized person, its security is lost. Here, with the assistance of triboelectric nanogenerators (TENGs), we present an intelligent electronic passworded locker (IEPL) based on unique and personalized security barriers, which can accurately extract users' habits of entering passwords through integrated deep learning. The key of the IEPL adopts the single electrode mode of TENG that accurately recognizes the input behavior of a person based on machine learning, which serves as a reliable, unique, and unreproducible gate, with advantages of thin thickness, diversified structure, and simple preparation method. Finally, the proposed IEPL offers a reliable solution for improving the overall security of passworded lockers and extending the application of TENG-based sensors in the smart home. [ABSTRACT FROM AUTHOR]

The relatively low output performance of triboelectric nanogenerator (TENG), which faces a challenge in performance improvement, limits its practical applications. Here, a high-performance TENG consisting of a silicon carbide@silicon dioxide nanowhiskers/polydimethylsiloxane (SiC@SiO2/PDMS) nanocomposite film and a superhydrophobic aluminum (Al) plate as triboelectric layers is demonstrated. The 7 wt% SiC@SiO2/PDMS TENG presents a peak voltage of 200 V and a peak current of 30 μA, which are ~ 300 and ~ 500% over that of the PDMS TENG, owing to an increase in dielectric constant and a decrease in dielectric loss of the PDMS film because of electric insulated SiC@SiO2 nanowhiskers. Furthermore, a 10 μF capacitor can be charged up to 3 V within ~ 87 s, which can be continuously operated on the electronic watch for 14 s. The work provides an effective strategy for improving output performance of TENG by adding core–shell nanowhiskers to modulate the dielectric properties of organic materials. [ABSTRACT FROM AUTHOR]

Highlights: The porous-reinforcement microstructure is constructed by the self-assembly of silicone rubber adhering to the porous framework of the PU sponge. With the excellent performance both for tiny pressure and large mechanical stimuli, the flexible triboelectric patch can be used to monitor pulse wave and plantar pressure. A remote healthcare system for real-time physiological signal monitoring is proposed. Realizing real-time monitoring of physiological signals is vital for preventing and treating chronic diseases in elderly individuals. However, wearable sensors with low power consumption and high sensitivity to both weak physiological signals and large mechanical stimuli remain challenges. Here, a flexible triboelectric patch (FTEP) based on porous-reinforcement microstructures for remote health monitoring has been reported. The porous-reinforcement microstructure is constructed by the self-assembly of silicone rubber adhering to the porous framework of the PU sponge. The mechanical properties of the FTEP can be regulated by the concentrations of silicone rubber dilution. For pressure sensing, its sensitivity can be effectively improved fivefold compared to the device with a solid dielectric layer, reaching 5.93 kPa−1 under a pressure range of 0–5 kPa. In addition, the FTEP has a wide detection range up to 50 kPa with a sensitivity of 0.21 kPa−1. The porous microstructure makes the FTEP ultra-sensitive to external pressure, and the reinforcements endow the device with a greater deformation limit in a wide detection range. Finally, a novel concept of the wearable Internet of Healthcare (IoH) system for real-time physiological signal monitoring has been proposed, which could provide real-time physiological information for ambulatory personalized healthcare monitoring. [ABSTRACT FROM AUTHOR]

Power sources and energy-harvesting schemes are still grand challenges for soft robots. Notably, compared with other power sources, triboelectric nanogenerators (TENGs) have shown great potential because of their low manufacturing and fabrication costs, outstanding resilience, remarkable stability, and environmental friendliness. Herein, a triboelectric effect-driven piezoelectric soft robot (TEPSR) system is proposed, which integrates a rotary freestanding triboelectric nanogenerator (RF-TENG) to drive a soft robot comprising a piezoelectric unimorph and electrostatic footpads. Based on the natural triboelectrification, through converting mechanical energy into electricity, TENG provides a unique approach for actuation and manipulation of the soft robot. The perfect combination provides the most straightforward way for creating a self-powered system. Experimentally, under the power of RF-TENG, the soft robot reaches a maximum moving speed of 10 cm per second and a turning rate of 89.7° per second, respectively. The actuation and manipulation demonstration are intuitively accomplished by maneuvering the robot around a maze with a 71 cm track within 28 s. For autonomous feedback controls, one practical application is carrying two infrared sensors on board to realize obstacle avoidance in an unstructured environment. Moreover, a micro-camera was equipped with the soft robot to provide real-time "first-person" video streaming, enhancing its detection capability. [ABSTRACT FROM AUTHOR]

Highlights: A fully self-powered bimodal sensor is designed for patterned-displaying the force trajectories. Outstanding mechanoluminescence is achieved with a stimulation force as low as 0.3 N and 2000 cycles reproducibility. The designed bimodal sensor exhibits good potential for handwriting input to achieve visual intelligent control. Self-powered flexible devices with skin-like multiple sensing ability have attracted great attentions due to their broad applications in the Internet of Things (IoT). Various methods have been proposed to enhance mechano-optic or electric performance of the flexible devices; however, it remains challenging to realize the display and accurate recognition of motion trajectories for intelligent control. Here, we present a fully self-powered mechanoluminescent-triboelectric bimodal sensor based on micro-nanostructured mechanoluminescent elastomer, which can patterned-display the force trajectories. The deformable liquid metals used as stretchable electrode make the stress transfer stable through overall device to achieve outstanding mechanoluminescence (with a gray value of 107 under a stimulus force as low as 0.3 N and more than 2000 cycles reproducibility). Moreover, a microstructured surface is constructed which endows the resulted composite with significantly improved triboelectric performances (voltage increases from 8 to 24 V). Based on the excellent bimodal sensing performances and durability of the obtained composite, a highly reliable intelligent control system by machine learning has been developed for controlling trolley, providing an approach for advanced visual interaction devices and smart wearable electronics in the future IoT era. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) utilize the phenomena of contact electrification and electrostatic induction to harvest mechanical energy from the environment. A good match between the motion frequency and the circuit characteristic frequency is critical for the effective power generation of a TENG. However, most TENGs have a time-dependent inherent capacitance (TIC-TENG), which hinders an optimal design for efficient energy conversion. Here, we propose a novel structure of a TENG with a constant inherent capacitance (CIC-TENG) and a mathematical model is established to provide analytical expressions of key output parameters of the device, which gives numerical simulation results that are in good agreement with the experimentally obtained results. Figures of merit and an optimization strategy are also given as guidelines for the optimization of material selection, geometry design, etc. Furthermore, a disk-formed CIC-TENG (DCIC-TENG) with polarity-switched triboelectric pairs is constructed to harvest unidirectional mechanical energy continuously, achieving an output power density of 55 mW/m2. The effects of the motion frequency, the number of electrodes and triboelectric pairs on the charge transfer efficiency of the DCIC-TENG are assessed and a preferred design strategy is given. Finally, the CIC-TENG demonstrates approximately two-fold advantages in power transfer efficiency over the TIC-TENG, and a DCIC-TENG-based self-powered anemometer was fabricated to measure wind speed in real time. [ABSTRACT FROM AUTHOR]