Triboelectric Nanogenerator Sensor Research Articles

Surface engineering AgNW transparent conductive films for triboelectric nanogenerator and self-powered pressure sensor

Triboelectric nanogenerator (TENG), originated from mechano-driven Maxwell’s displacement current, has shown great significance in harvesting low-frequency/high-entropy mechanical energy. To improve the electrical performances of TENG, surface engineering offers a facile and economical method by introducing electron donating/withdrawing groups. Here, we demonstrate a self-assembled monolayer (SAM)-assisted surface engineering strategy on AgNWs based transparent conductive film for TENG and self-powered pressure sensor. The SAM-assisted surface engineering provides an efficient means to tuning the surface potential and charge density of the friction layer by decorating different chemical functional groups. The chemical properties of decorated SAMs and their influence on TENG outputs are systematically investigated. The modified TENG exhibits an improved output performance (including open-circuit voltage of 300 V, short-circuit current of 23 μA, peak power of 1.24 mW, and power density of 1.4 W/m2), which can be readily used to drive commercial portable electronics. Furthermore, the modified TENG can be utilized as a self-powered pressure sensor with high sensitivity (221 V·kPa−1) and constructed into a pressure sensor array (4 × 4 pixels) for trajectory tracking. This work presents a universal method to tuning the electrical performance of TENGs and extends their potential applications toward low-power-consuming, highly sensitive, and multifunctional sensory devices and systems.

Drug-screening triboelectric nanogenerator-based strain sensor for cardiomyocyte contractility

Triboelectric nanogenerator (TENG) sensors have been widely developed for strain detection in health monitoring. However, current TENG sensors are insufficient to accurately detect the weak strain (< 1%) at the cellular scale (e.g. contraction of cardiomyocytes). Here, we propose a TENG-based strain sensor with a high signal-to-noise ratio (SNR) and stability to quantitatively measure the contractility of cardiomyocytes. 100,000 contact-separation cycles could be stably achieved under the strain of 16.9% (pneumatic pressure = 11 kPa), due to the effective separation of two friction layers between the micro-scale gap (8 µm). 50 µm-thickness friction layer with nano-cracks (average width = 48.1 ± 11.9 nm) lowered the strain detection limit to 0.025% with SNR of 12.1. During 11-day continuous monitoring of cardiomyocytes and drug treatment testings, the device demonstrated high SNR and stability to record the dynamic change caused by contractility of the cardiomyocytes. The flexible strain sensor based on TENG shows the potential of in cardiac pharmacological evaluation strategy.

Robust Displacement Sensing by Direct-Current Triboelectric Nanogenerator Via Intelligent Waveform Recognition.

A triboelectric nanogenerator (TENG) facilitates the advancement of self-powered displacement sensors, which are important for many autonomous intelligent microsystems. However, the amplitude-based displacement sensing of conventional TENG-based sensors still suffers significantly from varying charge densities in harsh environments. Benefiting from the combination of intelligent signal processing algorithms and direct-current TENG sensors, this study proposes an environmentally robust character-based displacement sensing method that eliminates the influences of varying charge density in principle. The experimental results show that under drastically changing air humidity and other harsh environments, the sensing of threshold and maximum displacement has far superior consistency and stability than that of traditional amplitude-based TENG sensors, providing a novel route to realize reliable self-powered displacement sensing in environment-variable applications.

A Lightweight Sensitive Triboelectric Nanogenerator Sensor for Monitoring Loop Drive Technology in Table Tennis Training

As the Internet of Things becomes more and more mainstream, sensors are widely used in the field of motion monitoring. In this paper, we propose a lightweight and sensitive triboelectric nanogenerator (LS-TENG) consisting of transparent polytetrafluoroethylene (PTFE) and polyamide (PA) films as triboelectric layers, polydimethylsiloxane (PDMS) as support layer, and copper foil as electrode. LS-TENG can be attached to the joints of the human body, and the mechanical energy generated by human motion is converted into electric energy based on the triboelectric effect, thus realizing self-power supply. LS-TENG can monitor the angle changes in elbow and wrist joints when athletes pull the loop and actively generate the output voltage as a sensing signal, which is convenient for coaches to monitor the quality of athletes’ hitting in real time. In addition, LS-TENG can also be used as a power supply for other wireless electronic devices, which facilitates the construction and transmission of large motion data and opens up a new development direction for the field of motion monitoring.

A flexible high-output triboelectric nanogenerator based on MXene/CNT/PEDOT hybrid film for self-powered wearable sensors

Developing flexible, low-cost, and self-powered triboelectric nanogenerator (TENG) with high output performance is an enormous challenge for reliable wearable electronics, whereas the disadvantages of low surface charge density hinder their potential applications. Here, a hybrid film consists of 1D carbon nanotubes (CNT), 2D niobium carbide (Nb2CTx) MXene, and conductive polymer (PEDOT) was prepared by one step vacuum assisted filtration method. A flexible high-output TENG with CNT/Nb2CTx/PEDOT hybrid membrane as the electrode and triboelectric layer for self-powered wearable sensors was obtained. Due to the synergistic effect of CNT, Nb2CTx MXene and PEDOT, the maximum output performance of the TENG sensor is achieved with an open circuit voltage (Voc) of 184.1 V and a short-circuit current (Isc) of 4.42 μA for device based on the CNT/MP11 hybrid film. Moreover, the corresponding sensor also has superior sensitivity with a response time of 20 ms, recovery time of 30 ms and good stability of over 400 cycles. Our findings provide a simple way for preparation of stable electrode layer and triboelectric layer, which have a broad application prospect in TENG-based wearable electronics.

A "Square Box"-Structured Triboelectric Nanogenerator for Road Transportation Monitoring.

Nowadays, with the rapid development of e-commerce, the transportation of products has become more and more frequent. However, how to monitor the situation of products effectively and conveniently during road transportation is a long-standing problem. In order to meet this problem in practical applications, we fabricated a triboelectric nanogenerator sensor with a “square box” structure (S-TENG) for detecting the vibration suffered by vehicles. Specifically, with the spring installed in the S-TENG as a trigger, the two friction layers can contact and then separate to generate the real-time electrical signals when the S-TENG receives external excitation. The output voltage signals of the S-TENG under different vibration states were tested and the results demonstrated that the peak and zero positions of the open-circuit voltage–output curve are related to amplitude and frequency, respectively. In addition, the subsequent simulation results, obtained by ANSYS and COMSOL software, were highly consistent with the experimental results. Furthermore, we built a platform to simulate the scene of the car passing through speed bumps, and the difference in height and the number of speed bumps were significantly distinguished according to the output voltage signals. Therefore, the S-TENG has broad application prospects in road transportation.

A triboelectric nanogenerator sensor based on phononic crystal structures for smart buildings and transportation systems

Many buildings and equipment are frequently disturbed by various types of elastic wave or vibration sources in ambient environment. The real-time state monitoring of such a disturbance is very important in the fields of green buildings and intelligent transportation systems. Based on triboelectric nanogenerators (TENGs), we propose a two-dimensional phononic crystal TENG (PC-TENG), which can serve as a self-powered sensor. The PC-TENG system consists of a periodical spherical cavity type of plate-like structure and elastic balls placed in each spherical cavity. Particularly, with bandgap property of phononic crystals, the proposed PC-TENG can also absorb or suppress vibration impact with certain frequencies acting on buildings and equipment. Taking elasticity, diameter, and surface roughness of elastic ball into account, we established a theoretical model of the cavity-ball type of PC-TENG based on Hertzian contact model. The sensing performance of the proposed PC-TENG with 5 by 5 cavities are experimentally measured, which shows the PC-TENG can efficiently detect the amplitude and frequency of an elastic wave disturbance. The theoretical output charges and currents evaluated from the developed theoretical model agree well with the experimental data.

A method of measuring weak-charge of self-powered sensors based on triboelectric nanogenerator

Although most the triboelectric nanogenerator sensors use the output voltage signal as the sensing signal, other signals such as current or charge cannot be ignored as sensing signal. TENG sensor is equivalent to a charge source with variable internal capacitance and outputs weak charge signal, which is not convenient for direct application as sensing signal. Therefore, it is essential to study the processing method of the output charge of TENG sensor. In this paper, a preprocessing method based on the output charge signal of TENG sensor is proposed to achieve accurate measurement of weak charge. In order to measure the amount of charge transfer output by the TENG device, the characteristics of "virtual ground"(non-inverting terminal grounding) at the inverting input of the inverting operational amplifier is used to transfer the charge signal output by the TENG sensor to the feedback arm capacitor, and the output charge signal is measured by measuring the low impedance and low voltage signal output by the inverting operational amplifier. Then, the reason affecting the characterization accuracy of the preprocessing method is analyzed theoretically, and the optimization strategy of each component parameter is established. Experiments are carried out with contact-separated mode triboelectric nanogenerator (CS-TENG) and rotary triboelectric nanogenerator (R-TENG) respectively, and the errors of the preprocessing method are controlled within 7% and 5% respectively, which proves the feasibility of the preprocessing method. This provides a new way to extract the charge signal from TENG sensor and is expected to be a new method to characterize the charge signal in TENG energy harvester.

Object recognition by a heat-resistant core-sheath triboelectric nanogenerator sensor

A flexible, heat-resistant and self-powered triboelectric nanogenerator sensor with a core-sheath structure was proposed for object recognition.

Study on fabric-based triboelectric nanogenerator using graphene oxide/porous PDMS as a compound friction layer

This study combined the commercially available conductive fabric with the polydimethylsiloxane (PDMS) layer containing graphene oxide (GO) to implement a fabric-based triboelectric nanogenerator (TENG) which is characterized by a simple process, low cost, high flexibility, and high stability. The findings showed that when the TENG used GO@PDMS compound layer, and after the surface was modified by SF6 plasma, the optimal open-circuit voltage of 140.4 V and short-circuit current of 2.57 μA were obtained. When the load resistance was 50 MΩ, the maximum power was 130.5 μW. Further testing illustrated this device to have excellent washability and tested for durability. When the TENG device was integrated with clothing and body, the action information could be obtained. This indicates that this device could be used as a posture or pressure sensor. As the TENG device can lighten up 180 green LEDs connected in series, it is suitably applied to develop microgenerators. Finally, this TENG device transmits signals to the mobile phone through a Bluetooth wireless module for a real-time display. It was proved the proposed fabric-based TENG sensor with self-powered and wireless transmission function has massive potential in future applications for use in wearable fitness trackers, E-skin of robotic arms, human–machine interfaces, and flexible touch sensors.

Wearable Triboelectric Sensors Enabled Gait Analysis and Waist Motion Capture for IoT-Based Smart Healthcare Applications.

Gait and waist motions always contain massive personnel information and it is feasible to extract these data via wearable electronics for identification and healthcare based on the Internet of Things (IoT). There also remains a demand to develop a cost‐effective human‐machine interface to enhance the immersion during the long‐term rehabilitation. Meanwhile, triboelectric nanogenerator (TENG) revealing its merits in both wearable electronics and IoT tends to be a possible solution. Herein, the authors present wearable TENG‐based devices for gait analysis and waist motion capture to enhance the intelligence and performance of the lower‐limb and waist rehabilitation. Four triboelectric sensors are equidistantly sewed onto a fabric belt to recognize the waist motion, enabling the real‐time robotic manipulation and virtual game for immersion‐enhanced waist training. The insole equipped with two TENG sensors is designed for walking status detection and a 98.4% identification accuracy for five different humans aiming at rehabilitation plan selection is achieved by leveraging machine learning technology to further analyze the signals. Through a lower‐limb rehabilitation robot, the authors demonstrate that the sensory system performs well in user recognition, motion monitoring, as well as robot and gaming‐aided training, showing its potential in IoT‐based smart healthcare applications.

Flexible MXene composed triboelectric nanogenerator via facile vacuum-assistant filtration method for self-powered biomechanical sensing

With the explosive development of sensing systems in miniaturization, intelligence, multi-function and networking, triboelectric nanogenerator (TENG) with simple structure, low cost and self-powering characters has become an excellent candidate for mechanical sensors. However, it remains a great challenge to obtain a stable interface of electrode and triboelectric layers for timely and long-term triboelectric surface charges transfer. In this study, through a simple vacuum-assistant filtration method, we prepared an integrated MXene-PEDOT:PSS/PTFE (MXene-poly(3,4-ethylenedioxythiophene):Poly (styrenesulfonate)/polytetrafluoroethylene) (MPP) film as the electrode and triboelectric layer of TENG for self-powered sensing. The TENG-based sensor has a high sensitivity especially to tiny forces (>6.05 V·N −1 ) with short response (52 ms) and recovery (34 ms) time, as well as an excellent stability (over 6000 cycles). The fabrication method is suitable for most conductive nanomaterials, and the triboelectric layer can be replaced with other commercialized filter films, such as cellulose and mixed fiber resin (MFR). It provides a simple and versatile method for the preparation of stable electrode-triboelectric interface, and has broad prospects in TENG-based wearable sensors. • Through one-step vacuum-assisted filtration, MXene nanosheets are deposited on filter films for fabricating TENG. • The TENG sensor has high sensitivity (>6.05 V·N −1 ), short response and recovery time, and excellent stability. • This method is generalizable for different conductive nanomaterials and commercialized filters to fabricate TENG.

Fibrous self-powered sensor with high stretchability for physiological information monitoring

Triboelectric nanogenerator (TENG) can convert mechanical energy into electricity, thus realizing the development of a new type of self-powered wearable sensors, which generate electric signals directly upon mechanical stimuli. On another hand, good stretchability is also an essential character of the wearable sensors to guarantee deformation consistence with the human body. In this work, a fibrous stretchable TENG-based sensor (FS-TENG sensor) with core-sheath structure is fabricated and applied in physiological monitoring. The output open-circuit voltage and shout-circuit current of FS-TENG sensor can reach nearly 10 V and 0.6 μA, respectively. The elastic substrates and stretchable electrodes provide the FS-TENG sensor with good resilience, and the output voltage of the sensor keeps stable under 60% strain extension, demonstrating the stability of the sensor at large deformation. Meanwhile, the FS-TENG sensor can detect ultralow pressure down to 0.02 N and achieve 26.75 V N −1 in low pressure, showing its ultralow detection limit and outstanding sensitivity to external force. Taking advantage of the excellent sensing performance of the FS-TENG sensor, we applied it in the human motions monitoring, including large movements (joints bending and step) and subtle vital signs (pulse, phonation, and expression). Moreover, a tactile sensor array with 3 × 3 pixels is fabricated by weaving 6 FS-TENG sensors to realize the pressure distribution recognition. • A fibrous stretchable triboelectric nanogenerator sensor (FS-TENG sensor) is fabricated. • The performance of FS-TENG sensor is enhanced by constructing microstructure and introducing conductive particles. • The FS-TENG sensor can output different electric signals corresponding to external force. • The applications of FS-TENG sensor in monitoring physiological information and pressure distribution are demonstrated.

Facile monitoring for human motion on fireground by using MiEs-TENG sensor

Recently, wearable electronics is rapidly developed in personal protective technology. Human motion monitoring using wearable electronics to protect workers on fireground remains challenging, such as high fabrication cost, materials flammability, operation energy consumption, and insufficient sensor information. Herein, we report a facile method for constructing self-powered sensors based on the triboelectric nanogenerator (TENG) to monitor human motion on fireground. Through directly writing the patterned MXenes ink electrodes (MiEs) on the triboelectric materials, the prepared bend sensor and pressure sensor can perceive safety-related information based on human motion, such as simple emergency hand signs and complex gaits. Furthermore, the triboelectric output data collected from pressure sensor is trained by the support vector machine (SVM) algorithm to classify different gaits with an accuracy of 92.18%. Looking forward, these TENG sensors assembled by this method could be incorporated into worker’s clothes to monitor motion for personal protection application on fireground.

Combination of Piezoelectric and Triboelectric Devices for Robotic Self-Powered Sensors.

Sensors are an important part of the organization required for robots to perceive the external environment. Self-powered sensors can be used to implement energy-saving strategies in robots and reduce their power consumption, owing to their low-power consumption characteristics. The triboelectric nanogenerator (TENG) and piezoelectric transducer (PE) are important implementations of self-powered sensors. Hybrid sensors combine the advantages of the PE and TENG to achieve higher sensitivity, wider measurement range, and better output characteristics. This paper summarizes the principles and research status of pressure sensors, displacement sensors, and three-dimensional (3D) acceleration sensors based on the self-powered TENG, PE, and hybrid sensors. Additionally, the basic working principles of the PE and TENG are introduced, and the challenges and problems in the development of PE, TENG, and hybrid sensors in the robotics field are discussed with regard to the principles of the self-powered pressure sensors, displacement sensors, and 3D acceleration sensors applied to robots.

Regulating the high-voltage and high-impedance characteristics of triboelectric nanogenerator toward practical self-powered sensors

In recent years, triboelectric nanogenerator (TENG), as a sensor with promising future, is expected to be widely used in many fields. However, the output of TENG has the characteristics of high voltage (> 10–100 V) and high impedance (in MΩ–GΩ), which hinder the TENG’s applications in sensor with considering the operation voltage of conventional electronic components. In this work, two front-end voltage signal processing circuit schemes are proposed, which can convert the high-impedance and high-voltage signal output from TENG into a low-voltage and low-impedance signal. First, we analyzed the circuit model by measuring the output voltage of the TENG sensor and explained the influence of the input impedance of the measuring device on the measurement accuracy. Then, we proposed two kinds of linear voltage signal processing methods which have been demonstrated the feasibility for a contact-separation mode TENG and a rotating type TENG. Finally, we applied the designed front-end signal processing circuit to a portable measurement system, which can measure the voltage signal up to 100 V output from a sliding mode TENG for local display or transmission to receiving terminal wirelessly. These two front-end voltage signal processing circuit solutions have the advantages of structure simplicities and cost-efficiency, and they can be used in combination with common electronic systems. The method can help with various practical TENG-based sensor applications and also provides an economical and simple solution for TENG voltage measurement. Two front-end voltage signal processing circuit schemes and linear voltage signal processing methods are proposed, which can convert the high-impedance and high-voltage signal output from TENG into a low-voltage and low-impedance signal. These two front-end voltage signal processing circuit solutions have the advantages of structure simplicities and cost-efficiency, and they can be used in combination with common electronic systems. The method can help with various practical TENG-based sensor applications and also provides an economical and simple solution for TENG voltage measurement. • Two regulating methods catering to the characteristics of high voltage and high impedance of TENG sensors were proposed. • A high-accuracy small signal circuit towards TENG was designed to replace specialized expensive measuring instruments. • An economical and exquisite solution for signal measurement is conducive to the practical application of TENG sensor.

Stretchable triboelectric sensor for measurement of the forearm muscles movements and fingers motion for Parkinson's disease assessment and assisting technologies

AbstractParkinson's disease (PD) is a degenerative, neurological disease that causes motor dysfunctions on the patient. Currently, the symptoms and progression of the disease are assessed by physicians who diagnose through careful observation, according to the Movement Disorder Society (MDS)‐sponsored Revision of the Unified Parkinson's Disease Rating Scale (UPDRS). In this manuscript, we report a portable sensor device based on a flexible Triboelectric Nanogenerator (TENG) formed from a dielectric material with a size of 4 cm × 3.5 cm and an aluminium (Al) electrode with dimensions of 2 mm × 3 mm, to monitor the movement of forearm muscles and tendons. When the hand or fingers extend or flex, the short gap between the dielectric polymer and the small conductor changes, generating a voltage due to triboelectric contact. The device is used to assess localized bradykinesia and rigidity of fingers and hands, as well as wrist and arm tremors. The voltage signal of the proposed sensor shows different waveform shapes, time duration and amplitude for each level of classification from ‘normal’ to ‘moderate’ status, described on the MDS‐UPDRS examination of hand movement, finger tapping and pronation–supination movement. Hence, we demonstrated that the proposed sensor can potentially be used for quantification of the symptoms and diagnosing. In addition, single finger motion tracking is also achieved by placing the triboelectric sensor in different positions around the forearm, close to the tendon connected to the finger under test. This way we avoid the placement of the sensor directly on the fingers, improving comfortability and long‐term wearability. The presented TENG sensor is fully integrated with the processing and the transmission board exploring new opportunities for triboelectric transducers in small motion detection of muscles. The future aim of this research is to provide real‐time monitoring of the disease progression as feedback for personalized treatment of the PD patients.

A robust and self-powered tilt sensor based on annular liquid-solid interfacing triboelectric nanogenerator for ship attitude sensing

Ship's attitude information is of great significance for navigation safety, cargo handling monitoring, and operation management. It is highly desired to develop an electromechanical integrated tilt sensor which can work well under harsh environment. In this paper, a robust and self-powered tilt sensor based on annular liquid-solid interfacing triboelectric nanogenerator (TENG) is to be proposed and systematically investigated. The TENG tilt sensor is composed of an annular polytetrafluoroethylene (PTFE) tube with copper electrodes segment disposed on the surface and the internal liquid which is encapsulated in PTFE tube with no air bubble. Studies on electrode width and liquid type are conducted to reasonably design the TENG sensor structure and improve its sensitivity. By conducting the durability test, the TENG tilt sensor demonstrates stable output performance and high sensitivity characteristics in low-frequency and low-amplitude inclination conditions. Moreover, the TENG tilt sensor hardly fails due to parts wear since there are no moving parts in it. The advantage of durability, maintenance-free, and independent with the external environment are highlighted in a harsh environment with high humidity, high salinity and strong magnetic field. Therefore, the present TENG tilt sensor is of practical significance for improving the automation and intelligence of ships.

Triboelectric nanogenerator sensors for soft robotics aiming at digital twin applications

Designing efficient sensors for soft robotics aiming at human machine interaction remains a challenge. Here, we report a smart soft-robotic gripper system based on triboelectric nanogenerator sensors to capture the continuous motion and tactile information for soft gripper. With the special distributed electrodes, the tactile sensor can perceive the contact position and area of external stimuli. The gear-based length sensor with a stretchable strip allows the continuous detection of elongation via the sequential contact of each tooth. The triboelectric sensory information collected during the operation of soft gripper is further trained by support vector machine algorithm to identify diverse objects with an accuracy of 98.1%. Demonstration of digital twin applications, which show the object identification and duplicate robotic manipulation in virtual environment according to the real-time operation of the soft-robotic gripper system, is successfully created for virtual assembly lines and unmanned warehouse applications.

Triboelectric and Piezoelectric Nanogenerators for Future Soft Robots and Machines.

SummaryThe triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) are two recently developed technologies for effective harvesting of ambient mechanical energy for the creation of self-powered systems. The advantages of TENGs and PENGs which include large open-circuit output voltage, low cost, ease of fabrication, and high conversion efficiency enable their application as new flexible sensors, wearable devices, soft robotics, and machines. This perspective provides an overview of the current state of the art in triboelectric and piezoelectric devices that are used as self-powered sensors and energy harvesters for soft robots and machines; hybrid approaches that combine the advantages of both mechanisms are also discussed. To improve system performance and efficiency, the potential of providing self-powered soft systems with a degree of multifunctionality is investigated. This includes optical sensing, transparency, self-healing, water resistance, photo-luminescence, or an ability to operate in hostile environments such as low temperature, high humidity, or high strain/stretch. Finally, areas for future research directions are identified.