Conventional Triboelectric Nanogenerator Research Articles

A Highly Wearable Single-electrode Mode Triboelectric Nanogenerator Made of Flexible Polyvinylidene Fluoride Transparent Film for Muscular Motion Monitoring

The present study reports the design and fabrication of a single-electrode mode triboelectric nanogenerator (TENGs) which can overcome the drawbacks present in the conventional triboelectric nanogenerator which works on two electrodes and two dielectric layers. The proposed concept eliminates the dual electrodes thereby reducing the complexity of the device and the higher fabrication cost enabling the device to be used for extended applications. The fabricated TENG device uses Polyvinylidene fluoride (PVDF) as the active material that is capable to generate the electrical response upon contact with the human skin when the device was worn on the skin. The device generates the highest electrical output of ~ 50 V and a current of ~ 600 nA under a 1 Hz operating frequency. The device also shows good stability and durability by powering continuously for 300 s without any interruption in its electrical output response. The device shows its applicability in utilizing it powering low-power electronic devices, bio-mechanical energy scavenging upon actuated by hand and foot tapping, as well as demonstrated for the self-powered muscular monitoring system. The study greatly expands the opportunity of using TENGs for applications in the field of healthcare, bio-medical, and the Internet of Things (IoT).

The influence of in-plane electrodes on TENG's output and its application in the field of IoT intelligent sensing

It is essential to improve the applicability of triboelectric nanogenerators (TENGs) in the Internet of Things (IoTs). The electrodes of traditional TENGs are all located on the backside of the friction surface, which greatly limits the combination of TENGs and IoTs terminals. The integration of traditional TENGs with IoTs is usually divided into embedding and pasting. Embedded integration increases the cost of manufacturing intelligent terminals. Stick-on attachment increases the risk of damage to TENGs. Therefore, an in-plane electrode TENG (IPE-TENG) is designed and fabricated to improve its applicability in the Internet of Things era. In this structure, the electrode and dielectric are in the same plane, which effectively reduces the integration cost and the risk of damage. Unlike conventional TENGs, this structure works by generating electricity based on the variation of the perpendicular and transverse electric fields of the dielectric and electrodes. Based on this working principle, edge effects in IPE-TENG are explored. The charge output is increased from 6.23nC to 19.16nC by optimizing the electrode area, electrode side length and equivalent distance. In addition, the effect of the electrodes on the output performance of IPE-TENG is also revealed by the capacitance model. Finally, an IPE-TENG integrated cup is designed to remind people to drink water. This work not only establishes a transverse induction-based TENG structure, providing a new idea for the study of TENG edge effect, but also provides a strategy for optimizing TENG output performance by using electrodes, and finally proves the feasibility of this structure in practical integrated devices in the era of the Internet of Things.

Wearable bistable triboelectric nanogenerator for harvesting torsional vibration energy from human motion

It is ubiquitous for torsional vibration of joint in human motion. However, it is difficult to harvest low-frequency torsional vibration energy from human motion using conventional triboelectric nanogenerators (TENGs). Herein, we propose a wearable bistable triboelectric nanogenerator (WBTENG) with a bistable stiffness feature, which enables high-efficiency torsional vibration energy harvesting from human motion. The prototype of the WBTENG is fabricated to test the electrical performance of the WBTENG. The dependencies of the electrical performance of the WBTENG on dynamic behaviors are investigated. Subsequently, the experiments are carried out to investigate the output voltages under different excitation frequencies, the output power varying with the load resistances and the durability of the WBTENG. In addition, the effect of the excitation amplitude on the electrical output performance of the WBTENG is investigated in detail. The bistable mechanism of the WBTENG is proved to switch the motion pattern between interwell and intrawell oscillations. The peak power is found to reach the highest value of 3.39 mW at 3 Hz with the resistance of 90 MΩ when the WBTENG exhibits interwell oscillation. Moreover, the WBTENG can power a light-emitting diode (LED) array and drive a temperature sensor under human motions. Therefore, the WBTENG can harvest torsional vibration energy efficiently from human motion.

A Dual-Functional Triboelectric Nanogenerator Based on the Comprehensive Integration and Synergetic Utilization of Triboelectrification, Electrostatic Induction, and Electrostatic Discharge to Achieve Alternating Current/Direct Current Convertible Outputs.

Traditional alternating current (AC) and direct current (DC) triboelectric nanogenerators (TENGs), which are implemented via the pairwise coupling of triboelectrification, electrostatic induction, and electrostatic discharge, have been widely explored in various fields. In this work, the comprehensive integration and synergetic utilization of triboelectrification, electrostatic induction, and electrostatic discharge in a single device for the first time is realized, achieving a dual-functional TENG (DF-TENG) to produce an AC/DC convertible output. Distinguishing from the conventional TENGs, the coupling of triboelectrification and electrostatic discharge enables charge circulation between the dielectric tribo-layers, while electrostatic induction realizes charge transfer in the external circuit. This novel energy conversion mechanism has been proven to be applicable to a variety of materials, including polymers, fabrics, and semiconductors. The output mode of the DF-TENG can be tuned by adjusting the slider motion state, and its constant output current and power density can reach 1.51 mA m-2 Hz-1 and 398 mW m-2 Hz-1 , respectively, which are the highest records reported for constant DC-TENGs to date. This work not only provides a paradigm shift to achieve AC/DC convertible output, but it also exhibits high potential for extending the TENG design philosophy.

Design and theoretical investigation of a torsional bistable triboelectric nanogenerator

Triboelectric nanogenerator (TENG) has been proven to be a high-efficiency device for converting vibration energy into electrical energy. However, the conventional TENG is unable to harvest energy from torsional vibration. To solve this issue, a torsional bistable triboelectric nanogenerator (TBTENG) is proposed. The essential part of the TBTENG is the S-shaped compliant beam, which enables bistability during torsional vibration. Firstly, the stiffness expression of the S-shaped beams is derived using the energy method, and verified by the finite element analysis (FEA). Then, the mechanical and electrical responses of the TBTENG are obtained by solving the equation of motion, and the unidirectional coupled electromechanical equation, respectively. The numerical simulations of the circuit model are also carried out using MATLAB/SIMULINK to validate the theoretical predictions. The effects of system parameters of the TBTENG on both the dynamic responses and electrical outputs are investigated. Finally, the experiment on the prototype of the TBTENG is conducted to verify the design concept. The results show that the novel bistable structure can drive the system to oscillate with large amplitude, which enables the TBTENG to effectively harvest energy from low-frequency torsional vibration. The peak power reaches the maximum value of 0.7 mW at 4 Hz. Moreover, the bandwidth of harvesting energy from low-frequency torsional vibration can be effectively broadened by enhancing the bistability.

Anaconda-shaped spiral multi-layered triboelectric nanogenerators with ultra-high space efficiency for wave energy harvesting

<h2>Summary</h2> Shifting from fossil fuels to clean energy is urgently needed to reduce anthropogenic carbon emissions. The ocean is recognized as an important source of renewable energy (i.e., wave and tidal), yet remains underutilized due to several technical barriers such as low energy conversion efficiency. The triboelectric nanogenerator (TENG), which can efficiently convert wave energy into electricity, has emerged as a potential solution. However, the low output performance and space utilization of existing TENGs impede commercial applicability. Here, we design an anaconda-shaped spiral multi-layered triboelectric nanogenerator (ASM-TENG) to overcome those two shortcomings. Benefiting from the tandem structure, compared with conventional TENGs, the ASM-TENG can enhance total power output by 2- to 30-fold with a peak power density at 347 W m⁻³, it can also enlarge the space utilization by 2- to 8-fold up to 93.75%. Our ASM-TENG provides a new strategy to improve the overall performance of TENG, strengthening its commercial applicability and further facilitating the development of ocean renewable energy.

Achieving Ultrahigh Effective Surface Charge Density of Direct-Current Triboelectric Nanogenerator in High Humidity.

As an emerging energy-harvesting technology, the triboelectric nanogenerator (TENG) is considered a powerful driving force toward the new-era of Internet of Things and artificial intelligence, but its output performance is dramatically influenced by environmental humidity. Herein, a direct current TENG (DC-TENG) based on the triboelectrification effect and electrostatic breakdown is reported to address the problem of output attenuation in high humidity environments for the conventional TENGs. It is found that high humidity not only enhances the sliding triboelectrification effect of hydrophobic triboelectric materials, but also promotes the electrostatic breakdown process for DC-TENG, thus contributing to the improvement of DC-TENG output. Furthermore, taking poly(vinyl chloride) film as the friction layer, the effective surface charge density of DC-TENG with microstructure-designed electrode achieves a milestone value of ≈2.97 mC m-2 under 90% relative humidity, which is almost 1.42-fold larger than that under 30% RH. This work not only establishes an effective methodology to boost the output performance of TENG in a high humidity environment, but also establishes a foundation for its practical applications in large-scale energy harvesting.

Robust and flexible triboelectric nanogenerator using non-Newtonian fluid characteristics towards smart traffic and human-motion detecting system

Due to the self-powered property of the triboelectric nanogenerator (TENG), development of the TENG based sensor is highly required to solve the major obstacles composed of the size and power consumption issues induced by external power source of the conventional Internet of Things (IoT) device. However, the conventional TENG based sensors are generally composed of thin films and these films can be easily damaged by external impact. With these damaged films, a malfunction of the conventional TENG based sensor can occur, which can induce an accident in a place where these sensors are utilized. Herein, the non-Newtonian fluid (NNF) with the shear thickening phenomenon (STP), which can increase its robustness as the applied external force to the NNF increases, is utilized to fabricate the TENG. Hence, the fabricated NNF with the STP based TENG (NNFT) is possessing the high resistance to impact as well as flexibility, simultaneously. The water-assisted oxidation is conducted to form the nanostructures on the surface of the Al electrode at the NNFT. Also, by adding the polyvinylidene fluoride powder into the NNFT (NNFT-P), the high open-circuit voltage of 260 V, short-circuit current of 11.2 μA, and power density of 37.5 mW/m2 are generated from the NNFT-P. As an application, the NNFT-P based self-powered traffic detection system (NSTDS) is implemented. With the NSTDS, the dangerous situation is successfully alerted to the pedestrian without significant damage in the NSTDS when the speeding vehicle is passing the NSTDS. Furthermore, the human motions including walking, running, and jumping are successfully detected with the proposed NNFT-P. Considering these results, the proposed NNFT-P is predicted to be utilized as the smart traffic system as well as human motion detecting sensor in near future.

An Energy Harvester Coupled with a Triboelectric Mechanism and Electrostatic Mechanism for Biomechanical Energy Harvesting.

Energy-harvesting devices based on a single energy conversion mechanism generally have a low output and low conversion efficiency. To solve this problem, an energy harvester coupled with a triboelectric mechanism and electrostatic mechanism for biomechanical energy harvesting is presented. The output performances of the device coupled with a triboelectric mechanism and electrostatic mechanism were systematically studied through principle analysis, simulation, and experimental demonstration. Experiments showed that the output performance of the device was greatly improved by coupling the electrostatic induction mechanisms, and a sustainable and enhanced peak power of approximately 289 μW was produced when the external impedance was 100 MΩ, which gave over a 46-fold enhancement to the conventional single triboelectric conversion mechanism. Moreover, it showed higher resolution for motion states compared with the conventional triboelectric nanogenerator, and can precisely and constantly monitor and distinguish various motion states, including stepping, walking, running, and jumping. Furthermore, it can charge a capacitor of 10 μF to 3 V within 2 min and light up 16 LEDs. On this basis, a self-powered access control system, based on gait recognition, was successfully demonstrated. This work proposes a novel and cost-effective method for biomechanical energy harvesting, which provides a more convenient choice for human motion status monitoring and can be widely used in personnel identification systems.

A high performance triboelectric nanogenerator based on ordered doping technique for human-machine interaction sensing

In order to solve the inherent problems of conventional nanoparticle doping, such as the mixed sizes and shapes of micro pores, chaotic arrangement of particles in micro pores and internal triboelectric field cancellation, we proposed a new scheme to efficiently increase the charge density by combining micro-nano machining technology with nanoparticle doping technology. A charge trap model formed by the friction inside the film was constructed by implementing directional doping in ordered micro pores. The effects of the size of micro pores, the concentration of doping particles (titanium dioxide nanoparticles TiO2) and the number of triboelectric layers on the external electric performance of the film were then systematically studied. The results show that a sustainable and enhanced transfer charge of about 428.3 nC was produced on the triboelectric nanogenerator with regular doped TiO2 in 80 µm holes, which was over 3.7-folds higher than that of conventional triboelectric nanogenerators (TENGs). The peak power of the TENG with regular doped TiO2 nanoparticles increased from 0.78 to 5.49 mW (~7.04 times higher). Then, the capability of the TENG with regular doped TiO2 nanoparticles in powering portable electrics was demonstrated by lighting up 235 LEDs and powering a thermometer. Importantly, the film can be easily integrated into human body for condition signals detection and human-machine interaction sensing in wireless control system. Our findings may offer new insights into the output characteristics of TENGs and accelerate their commercialization and application.

Semisolid-lubricant-based ball-bearing triboelectric nanogenerator for current amplification, enhanced mechanical lifespan, and thermal stabilization

Triboelectric nanogenerators (TENGs) represent a promising tool for harvesting mechanical energy and can generate electrical output through the surface charge of materials. However, because this conversion is based on contact electrification, frictional contact inevitably occurs between materials, and the high surface charge considerably limits the electrical output of TENGs. To effectively decrease the frictional wear of triboelectric materials, commercial lubricants can be applied while ensuring a suitable mechanical structure design. In this study, we demonstrated a ball-bearing-type TENG with a commercial semisolid lubricant, which could overcome the mechanical and electrical limitations of conventional TENGs. The application of a nonpolar semisolid lubricant on the surface of triboelectric materials could effectively suppress air breakdown and enhance the mechanical lifespan of the device by reducing friction. Owing to the reduced wear and enhanced thermal stability, the ball-bearing-type TENG could generate a consistent electrical output for over 55 h of continuous operation.

Bow-type bistable triboelectric nanogenerator for harvesting energy from low-frequency vibration

Triboelectric nanogenerators (TENGs) are emerging, leading-edge, and promising devices for converting ambient vibration energy into electrical energy and power for low-power sensors. However, it is difficult to harvest energy from low-frequency ambient vibrations using conventional TENGs. To solve this issue, in this study, we propose a bow-type TENG with a bistable stiffness feature, which enables the conversion of low-frequency vibration energy into electrical energy with high efficiency. The dynamic model of the bow-type TENG was established based on extended Hamilton’s principle and numerically solved to obtain the dynamic responses. Subsequently, a prototype of the bow-type TENG was fabricated and tested to verify the design concept. Moreover, the dependencies of the energy-harvesting performance on the structural parameters were experimentally investigated. The average power had a maximum value of 0.64 mW at 5 Hz in the case of optimal load resistance. The bow-type TENG could power a number of light-emitting diodes (LEDs) to display the word “HNU” under low-frequency excitation. Hence, the bow-type TENG can substantially extend the function of harvesting vibration energy from high to low frequencies.

Triboelectric Nanogenerator with Low Crest Factor via Precise Phase Difference Design Realized by 3D Printing.

Triboelectric nanogenerator (TENG) has presented the huge potential application in distributed energy field which can realize the conversion from dispersed mechanical energy to electric energy. However, the natural characteristic of pulse output for conventional TENG, which means high crest factor, is defective for directly driving electronics. Here, a strategy to convert the pulse alternate current of TENG into a direct current with low crest factor is achieved through introducing a phase difference design into the structure of TENG. As a result, a direct current with a crest factor of 1.07 is obtained in a rotational free-standing TENG (RF-TENG) array at optimum phase difference, where 3D digital printing technology is used to accurately control the parameter of phase difference. Moreover, an adaptable contact mode structure between tribolayer and electrode improves the durability of the RF-TENG array, which can present a stable performance after working 1.2 million cycles. This work provides a combined strategy to obtain a long-lifetime and low crest-factor TENG for its large-scale application in energy harvesting.

Liquid-metal embedded sponge-typed triboelectric nanogenerator for omnidirectionally detectable self-powered motion sensor

With the increasing number of devices that require electrical energy, various types of triboelectric nanogenerators (TENGs), a promising technology for energy harvesting, have been developed in recent years. However, conventional TENGs show relatively low mechanical flexibility because each layer of the conventional TENGs is composed of rigid materials. Low mechanical flexibility produces electrical energy in one-way operation and limits the utilization of TENGs in a variety of applications. In this work, we develop the liquid-metal embedded sponge-typed TENG (LMST). Liquid-metal and silicon rubber are utilized to fabricate the LMST with a peculiar sponge shape, which is inherently including the randomly distributed pores with dispersed liquid-metal droplets. Hence, the LMST can be bent 180° and stretched 300%, which indicates the great flexibility and stretchability of the LMST. The LMST with size of the 1.5 cm × 1.5 cm × 1.5 cm generated a short-circuit current ( I SC ) of 188 nA and an open-circuit voltage ( V OC ) of 24 V. Also, the 2.48 W/m 2 of power density is generated from the proposed LMST by simply inserting wires into the LMST without any conventional processes for fabricating electrodes. Interestingly, the electrical power can be used simply by connecting wires to the LMS, and power can be greatly improved by increasing the number of wires connected to the LMST. Additionally, various shapes of the LMST are facilely designed using 3D printing technology for a wide spectrum of applications. To prove the applicability of the LMST with the unique porous structure, three types of self-powered sensor systems are demonstrated, which are detecting the pressure, the direction of a spinning ball, and real-time detecting malfunction of motor faults. The flexible advantages of the liquid-metal embedded sponge structure triboelectric nanogenerator device, allow us to extend its applicability to battery-free sensors that can be used in various locations. • Using liquid metal, sugar and silicone elastomer, conductive sponges can be produced through a simple manufacturing process. • Electrical power can be generated using the principle of a single electrode TENG by simply connecting a wire to a sponge. • Due to the elasticity of porous sponges, electrical power can be collected from various directions. • The direction of rotation of the ball and motor defects can be detected using LMST.

A self-powered photodetector using a pulsed triboelectric nanogenerator for actual working environments with random mechanical stimuli

The self-powered sensing systems based on impedance matching effect have been proposed by using a triboelectric nanogenerator (TENG) as power source, which have attracted widespread attention in the field of Internet of Things. However, the output voltage and current of the conventional TENG are affected by not only the load impedance but also the working frequency of TENG, leading to inaccurate sensing results in actual working environments with random mechanical stimuli. For solving this problem, a self-powered sensing system using a Pulsed-TENG with a synchronous trigger switch has been proposed here, in which the output voltage and current of Pulsed-TENG are independent on its working frequency. The measured performances of a self-powered photodetector have verified that same detection results could be obtained for various rotation frequencies of a rotating Pulsed-TENG. Two self-powered detection modes, current mode and voltage mode, have been developed. In the current detection mode, the output current increased linearly with light intensity, and the detectable range of light intensity is 0–1 W/m2. In the voltage detection mode, the output voltage is inversely proportional to the light intensity, and the detectable range of light intensity is 9–403 W/m2. Finally, a self-powered photodetection system with visual display function has been developed, in which the light intensity can be displayed intuitively by the number of lighted LEDs. Since the output voltage and current of Pulsed-TENG are independent on its working frequency, the self-powered sensing system based on Pulsed-TENG proposed here has provided a promising strategy suitable for the actual working environments with random mechanical stimuli.

A bulk effect liquid-solid generator with 3D electrodes for wave energy harvesting

Wave energy is one of the most promising renewable energy sources. The approaches for wave energy harvesting have been attracting more and more attentions all over the world. Although triboelectric nanogenerators (TENGs) based on liquid-solid interface have offered a new method for wave energy harvesting, some challenges still remain such as the relatively low energy power density and energy conversion efficiency. Here, we introduce a liquid-solid generator with electrode arrays that allows for improved wave energy harvesting compared to conventional TENG. The design of 3D electrodes above dielectric layer engenders a bulk effect that connect the electrode array, the polymer layer and bulk water into a closed-looped system. The arrayed generator can also be assembled easily and the instantaneous output power density can be enhanced from 2.7 W/m 2 to 11.7 W/m 2 with the 3D electrodes. We envision that this bulk effect generator based on liquid-solid interface will open new insight in blue energy harvesting in the future. ● A liquid-solid generator based on bulk effect for wave energy harvesting has been realized. ● Following the design of 3D electrodes, the bulk effect liquid-solid generator can output high current of 4 mA. ● Through the arrangement of arrayed generator, a high instantaneous power density of 11.7 W/m 2 is achieved.

Suppressing Thermal Negative Effect and Maintaining High-Temperature Steady Electrical Performance of Triboelectric Nanogenerators by Employing Phase Change Material.

Triboelectric nanogenerators (TENGs) are newly developed energy-harvesting mechanisms, which can efficiently transmute irregular mechanical energy into scarce electrical energy. However, the electrical performance of TENGs shows a decreasing tendency with the increase in temperature, and the negative effect caused by friction heat and operating environmental thermal stresses for the output performance, durability, and reliability are still a bottleneck, restricting the practical application of TENG electronic devices. Especially for wearable TENG devices, the heat-induced temperature rise evokes extreme discomfort and even hazards to human health. To effectively suppress the thermal negative effect and maintain the high-temperature steady electrical performance of TENGs, a novel thermo-regulating TENG (Tr-TENG) based on phase change materials (PCMs) is designed. The results state clearly that the Tr-TENG can maintain steady output performance without deterioration by the introduction of PCMs, during continuous heating and natural cooling, while the output performance of conventional TENG is decayed by 18.33%. More importantly, the Tr-TENG possesses high-efficiency thermal management ability, resulting in its improved durability, reliability, and thermal comfort. This study creates new possibilities for the development of advanced multifunctional TENGs with attractive characteristics and desirable performances and promotes the application of TENG electronic devices in harsh environments.

A robust rolling-mode direct-current triboelectric nanogenerator arising from electrostatic breakdown effect

Abstract With merits of light weight, low cost, and high efficiency even at low frequency, triboelectric nanogenerator (TENG) has been considered as a potential solution for distributed energy for the new era of internet of things (IoTs). However, the conventional TENG always has intrinsic property of high current crest factor, which is unable to drive electronics directly, and its output performance is usually limited by air breakdown and material wear. Here, we designed a rolling-mode direct-current TENG (R-DC-TENG) by coupling triboelectrification effect and electrostatic breakdown for realizing a constant current (crest factor ~1) output in rolling mode TENG for the first time. The R-DC-TENG shows the output characteristics of a quasi-constant current source, with a stable constant current output at load from 1 kΩ to 100 MΩ. More importantly, it exhibits an excellent robustness compared with the reported sliding-mode DC-TENG (S-DC-TENG).

Multi‐Mode Water‐Tube‐Based Triboelectric Nanogenerator Designed for Low‐Frequency Energy Harvesting with Ultrahigh Volumetric Charge Density

AbstractVast renewable energies are contained in mechanical motions in nature such as ocean waves. However, it is challenging to effectively harness these energy sources due to their low frequency and irregularity. Triboelectric nanogenerators (TENGs) are a promising technology for renewable energy conversion, but conventional TENGs suffer from challenges including single‐mode operation, low contact intimacy, and material abrasion. Here, by encapsulating deionized DI water into a fluorinated ethylene‐propylene tube, a versatile and high‐performance water‐tube‐based TENG (WT‐TENG) is developed. Benefiting from the high flexibility of the water, the WT‐TENG can work at various operation modes and generate power from multiple mechanical energy sources. With the intimate water/solid contact, the WT‐TENG achieves an ultrahigh volumetric output charge density of 9 mC m−3 at a frequency of 0.25 Hz, beyond all previous reports. Moreover, multiple finger‐sized WT‐TENG units can be easily integrated as one device and realize multiplied outputs. A wearable body motion energy harvester and a water wave energy harvester are demonstrated as examples of the WT‐TENG applications. The proposed WT‐TENG can be regarded as a new brick for the TENG mansion, and numerous applications could be built up based on the WT‐TENG units.

Improved Output Performance of Triboelectric Nanogenerator by Fast Accumulation Process of Surface Charges

AbstractAs a promising energy harvesters, triboelectric nanogenerators (TENG) can be utilized to convert distributed energy into electric power, but the slow charge accumulation incorporated with the inevitable charge decay/leakage of conventional TENGs result in a low surface charge density and an inferior output performance, limiting their practical applications. Here, an effective strategy is proposed to realize high charge density by using a fast charge accumulation process on dielectric material with high relative permittivity. As a result, the charge density is tremendously improved to 2.20 mC m−2 on the poly(vinylidene fluoride‐trifluoroethylene) film. Meanwhile, the fast charge accumulation is highly conducive to reach a high charge density of 1.30 mC m−2 in a 90% relative humidity environment, which is ≈260 times that of a TENG with slow charge accumulation. This work not only provides a new insight into charge accumulation and equilibrium state, but also provides significant guidance on the performance optimization of TENG.