Multiscale Structural Nanocellulosic Triboelectric Aerogels Induced by Hofmeister Effect

The advent of self-powered wearable electronics will revolutionize the fields of smart healthcare and sports monitoring. This technological advancement necessitates more stringent design requirements for triboelectric materials. The triboelectric aerogels must enhance their mechanical properties to address the issue of structural collapse in real-world applications. This study fabricates stiff nanocellulosic triboelectric aerogels with multiscale structures induced by the Hofmeister effect. The aggregation and crystallization of polymer molecular chains are enhanced by the Hofmeister effect, while ice crystal growth imparts a porous structure to the aerogel at the micron scale. Therefore, the triboelectric aerogel exhibits exceptional stiffness, boasting a Young's modulus of up to 142.9 MPa and a specific modulus of up to 340.6 kN m kg^–1, while remaining undeformed even after supporting 6600 times its weight. Even after withstanding an impact of 343 kPa, highly robust wearable self-powered sensors fabricated with triboelectric aerogels remain operational. Additionally, the self-powered sensor is capable of accurately detecting human movements, particularly in abnormal fall postures detection. This study provides considerable research and practical value for promoting material design and broadening application scenarios for self-powered wearable electronics.     

Flexible High-Resolution Triboelectric Sensor Array Based on Patterned Laser-Induced Graphene for Self-Powered Real-Time Tactile Sensing

Flexible tactile sensors are garnering substantial interest for various promising applications, including artificial intelligence, prosthetics, healthcare monitoring, and human–machine interactions (HMI). However, it still remains a critical challenge in developing high-resolution tactile sensors without involving high-cost and complicated manufacturing processes. Herein, a flexible high-resolution triboelectric sensing array (TSA) for self-powered real-time tactile sensing is developed through a facile, mask-free, high-efficient, and environmentally friendly laser direct writing technique. A 16 × 16 pixelated TSA with a resolution of 8 dpi based on patterned laser-induced graphene (LIG) electrodes (7 Ω sq⁻¹) is fabricated by the complementary intersection overlapping between upper and lower aligned semicircular electrode arrays. With the especially patterning design, the complexity of TSA and the number of data channels is reduced. Meanwhile, the TSA platform exhibits excellent durability and synchronicity and enables the achievement of real-time visualization of multipoint touch, sliding, and tracking motion trajectory without power consumption. Furthermore, a smart wireless controlled HMI system, composed of a 9-digital arrayed touch panel based on a LIG-patterned triboelectric nanogenerator, is constructed to control personal electronics wirelessly. Consequently, the self-powered TSA as a promising platform demonstrates great potential for an active real-time tactile sensing system, wireless controlled HMI, security identification and, many others.     

AI-Enabled Metal-Polymer Plain Bearing Based on the Triboelectric Principle

With the rapid development of the Internet of Things and artificial intelligence (AI), the requirement for sensing technologies for smart bearings has increased dramatically. The general bearing sensors can only recognize the basic information from temperature or vibration, far from satisfying the self-diagnosis and self-maintenance. Recently, self-powered sensing technologies based on triboelectric nanogenerators have paved a new route for fabricating smart bearings. In this study, the triboelectric principle is applied to a commercial metal-polymer plain bearing (MPPB) bearing, which can achieve self-sensing, self-diagnosis, and self-maintenance. The geometrical structure of the triboelectric MPPB (T-MPPB) is designed to balance the output efficiency and external load, and the super durability and load capability are verified. Besides, the mechanism behind the output change trend under boundary and hydrostatic fluid lubrication is revealed for the first time. Furthermore, the deep learning algorithm can classify the lubrication states with highly accurate performance. The proposed T-MPPB has the potential to achieve self-maintenance with the lubricating pump according to the lubrication condition classified by the AI. This research not only establishes the feasibility of designing self-powered smart MPPB but also demonstrates a way for identifying lubrication states, thus achieving self-diagnosis and self-maintenance ability by self-powered sensors.     

Autonomously Adhesive,Stretchable, and Transparent Solid-State Polyionic Triboelectric Patch for Wearable Power Source and Tactile Sensor

Robust power supplies and self-powered sensors that are extensible, autonomously adhesive, and transparent are highly desirable for next-generation electronic/energy/robotic applications. In the work, a solid-state triboelectric patch integrated with the above features ( ≈ 318% elongation, > 85% average transmission, ≈ 44.3 N m⁻¹ adhesive strength) is developed using polyethylene oxide/waterborne polyurethane/phytic acid composite (abbreviated as PWP composite) as an effective current collector and silicone rubber as tribolayer. The PWP composite is optimized systematically and corresponding single-electrode device can supply a power density of 2.3 W m⁻² at 75% strain. The triboelectric patch is capable of charging capacitors and powering electronics by efficiently harvesting biomechanical energies. Moreover, it can be autonomously attached to nonplanar skin or apparel substrates and used as a tactile sensor or an epidermal input touchpad for physiological motion detection and remote control of appliances, respectively. Even after dynamic deformation, tailoring, and prolonged use, the patch can maintain good stability and reliability of electrical outputs. This work provides a novel solid-state and liquid-free polyionic electrode-based triboelectric nanogenerator integrated with adhesiveness, stretchability, and transparency, which can meet wide application needs from transparent electronics, artificial skins, to smart interfaces.     

Harvesting Multidirectional Breeze Energy and Self-Powered Intelligent Fire Detection Systems Based on Triboelectric Nanogenerator and Fluid-Dynamic Modeling

Fire warning and monitoring are very important for public safety and environmental protection. However, most of the proposed wind energy conversion devices based on triboelectric nanogenerator (TENG) only work for unidirectional and high-speed wind and face the challenge of fatigue damage and even failure caused by cyclic stress. Moreover, TENG guided by the theory of fluid dynamics needs further exploration. Herein, a flow-induced vibration effect based TENG (F-TENG) for continuously capturing and monitoring multidirectional breeze (1.8–4.3 m s⁻¹) is developed to build a self-powered intelligent fire detection system (SIFDS). A dynamic model is proposed to study the intrinsic interaction between the electrical properties of F-TENG and wind. Since the model optimized F-TENG is more adaptable to wind characteristics, it delivers better performance and higher durability compared with previous studies. Relying on the dynamic model and combining the relationship between F-TENG's electrical output and wind characteristics, a self-powered visual wind sensing system is obtained. F-TENG successfully drives some electronic devices to monitor environmental information, which is expected to provide data for SIFDS to reduce fire hazards. This study can provide an in-depth understanding of the electromechanical conversion mechanism and large-scale capture and utilization of breeze energy.     

Single‐Thread‐Based Wearable and Highly Stretchable Triboelectric Nanogenerators and Their Applications in Cloth‐Based Self‐Powered Human‐Interactive and Biomedical Sensing

The development of wearable and large‐area fabric energy harvester and sensor has received great attention due to their promising applications in next‐generation autonomous and wearable healthcare technologies. Here, a new type of “single” thread‐based triboelectric nanogenerator (TENG) and its uses in elastically textile‐based energy harvesting and sensing have been demonstrated. The energy‐harvesting thread composed by one silicone‐rubber‐coated stainless‐steel thread can extract energy during contact with skin. With sewing the energy‐harvesting thread into a serpentine shape on an elastic textile, a highly stretchable and scalable TENG textile is realized to scavenge various kinds of human‐motion energy. The collected energy is capable to sustainably power a commercial smart watch. Moreover, the simplified single triboelectric thread can be applied in a wide range of thread‐based self‐powered and active sensing uses, including gesture sensing, human‐interactive interfaces, and human physiological signal monitoring. After integration with microcontrollers, more complicated systems, such as wireless wearable keyboards and smart beds, are demonstrated. These results show that the newly designed single‐thread‐based TENG, with the advantage of interactive, responsive, sewable, and conformal features, can meet application needs of a vast variety of fields, ranging from wearable and stretchable energy harvesters to smart cloth‐based articles.     

A Multi-Layer Stacked Triboelectric Nanogenerator Based on a Rotation-to-Translation Mechanism for Fluid Energy Harvesting and Environmental Protection

Energy shortage and environmental degradation are two important challenges facing humanity. Here, a multi-layer stacked triboelectric nanogenerator (MLS-TENG) based on a rotation-to-translation mechanism is reported for fluid energy harvesting and environmental protection. The mechanism transforms fluid-induced rotation into a reciprocal translation of the MLS-TENG, enabling the conversion of fluid energy into electrical energy. In addition, benefiting from a multi-layer stacked structural design, the open-circuit voltage is increased from 860 to 2410 V and an efficient energy harvesting rate of 2 mJ min⁻¹ is obtained in an actual river. Furthermore, with the assistance of the MLS-TENG, a self-powered wireless temperature and humidity monitoring system and a metal anticorrosion system are successfully established. Ambient monitoring data can be transmitted continuously at an interval of 49.7 s, and the corrosion rate of steel is significantly slowed down. This study provides guidance for efficient harvesting of ambient fluid energy, with promising applications in environmental monitoring and protection.     

Self-Powered Piezoelectric Actuation Systems Based on Triboelectric Nanogenerator

Sustainable power supply via triboelectric nanogenerator (TENG) is attractive for self-powered actuation systems in the era of the Internet of Things (IoTs). Herein, a low-power actuation scheme enabled by the multilayered TENG for piezoelectric actuators, including the stack, unimorph, and micro-fiber composite (MFC) actuator, is reported. The working principles of TENG-powered piezoelectric actuators and their displacement characteristics in direct current (DC) and alternating current (AC) modes are theoretically investigated. Compared with conventional high-voltage power sources, the multilayered TENG delivers a maximum power of only 10.17 mW, providing a low-power alternative for piezoelectric actuator with self-powered capability and operational safety. Meanwhile, the hysteresis of the stack actuator that is critical in precise positioning control is reduced by 58.1%. A precise positioning system is demonstrated by utilizing the TENG-powered stack actuator as an object stage for microscope focusing applications. The feasibility of vibration control with a 76.7% reduction in vibration amplitude is also verified via two TENG-powered MFC actuators. A rectifying control circuit comprising the rectifier and gas discharging tube is established to implement AC–DC conversion and discharging control, achieving a larger displacement of the unimorph actuator. The TENG-powered piezoelectric micropump demonstrates its potential application in liquid transport through straightforward operation.     

Real-Time Non-Driving Behavior Recognition Using Deep Learning-Assisted Triboelectric Sensors in Conditionally Automated Driving

Real-time recognition of non-driving behaviors is of great importance in conditionally automated driving, as it determines the takeover time budget, which in turn has a huge impact on the performance of the takeover. Here, a novel real-time non-driving behavior recognition system (RNBRS) integrating self-powered, low-cost, easy-to-manufacture triboelectric sensors, and a deep learning model is proposed. The structure, working mechanism, and electrical characteristics of triboelectric sensors are investigated and analyzed. Through the ingenious structural design of single-electrode triboelectric sensors and driving simulation experiments under conditional automated driving, non-driving behaviors are captured in the form of electrical signals. A well-trained long short-term memory network model is adopted to recognize the five most typical non-driving behaviors, including phone, console touchpad, driving, monitoring driving, and no operation, and test accuracy of 93.5% is achieved. Demonstration of a set of controlled experiments shows that RNBRS enables vehicles with conditional automation to dynamically adjust takeover time budget based on driver behavior, therefore significantly improving both safety and stability of takeover. This study opens new frontiers for the development of self-powered electronics and inspires new thoughts on human-machine interaction and the safety of autonomous vehicles.     

Self-powered In-Phase Sensing and Regulating Mechanical System Enabled by Nanogenerator and Electrorheological Fluid

Mechanical system with adjustable stiffness and damping (ASAD) shows great potential in vibration suppression of aircraft, vehicle, precise instrument, etc. However, current ASAD systems consist of power, sensing, and controlling components, which bring huge challenges of system reliability and integrability, and critically limit its application diversity. Herein, we proposed the first strategy for regulating ASAD system that is system simplification, self-powered and no-delay by deeply coupling triboelectric nanogenerator (TENG) and electrorheological fluid (ERF). Under the time-varying mechanical triggering, the local and time correlated output of TENG instantaneously applied on the ERF regulates the entire mechanical system dynamically and “in-phase”. As an illustration, the resonance of a cantilever system is effectively suppressed naturally without complicated controlling strategy, and the vibration isolating efficiency reaches up to 85.2%. Finally, a mechanical transmission system is demonstrated utilizing a rotary TENG and ERF, excellent soft-start performance is enabled by this self-regulating ASAD strategy. This work may provide the opening arsenal of methodologies used in self-powered and self-regulating mechanical systems.     

Auxetic Foam‐Based Contact‐Mode Triboelectric Nanogenerator with Highly Sensitive Self‐Powered Strain Sensing Capabilities to Monitor Human Body Movement

The first contact‐mode triboelectric self‐powered strain sensor using an auxetic polyurethane foam, conductive fabric, and polytetrafluroethylene (PTFE) is fabricated. Utilizing the auxetic properties of the polyurethane foam, the auxetic polyurethane foam would expand into the PTFE when the foam is stretched, causing contact electrification. Due to a larger contact area between the PTFE and the foam as the foam is stretched, this device can serve effectively as a strain sensor. The sensitivity of this method is explored, and this sensor has the highest sensitivity in all triboelectric nanogenerator devices that are used previously as a strain sensor. Different applications of this strain sensor are shown, and this sensor can be used as a human body monitoring system, self‐powered scale to measure weight, and a seat belt to measure body movements inside a car seat.     

Versatile Ion-Gel Fibrous Membrane for Energy-Harvesting Iontronic Skin

Developing versatile and high sensitivity sensors is beneficial for promoting flexible electronic devices and human-machine interactive systems. Researchers are working on the exploration of various active sensing materials toward broad detection, multifunction, and low-power consumption. Here, a versatile ion-gel fibrous membrane is presented by electrospinning technology and utilized to construct capacitive sensors and triboelectric nanogenerator (TENG). The iontronic capacitive sensor exhibits inherently favorable sensitivity and repeatability, which retains long-term stability after 5000 cycles. The capacitive sensor can also detect a clear pulse waveform at the human wrist and enable the mapping of pressure distribution by a capacitive sensory matrix. For the iontronic TENG, the maximum peak power is 54.56 µW and can be used to power commercial electronics. In addition, the prepared iontronic TENG array can achieve interactive, rapidly responsive, and accurate dynamic monitoring, which broadens the exploration to direct and effective sensory devices. The versatile ion-gel fibrous membrane is promising to provide an outstanding approach for physiological detection, biomechanical energy harvesting, human-machine interaction, and self-powered monitoring systems.     

All-Nanofiber Self-Powered Skin-Interfaced Real-Time Respiratory Monitoring System for Obstructive Sleep Apnea-Hypopnea Syndrome Diagnosing

Human respiration is an indispensable physiological behavior of the body, which is an important indicator to evaluate health status, especially for sleep-related diseases. A real-time respiratory monitoring and sleep breathing detecting system with convenience, high sensitivity, simple fabrication, and wearing comfort still remains a challenge and urgently desirable. Here, a breathable, highly sensitive, and self-powered electronic skin (e-skin) based on a triboelectric nanogenerator (TENG) is reported for real-time respiratory monitoring and obstructive sleep apnea-hypopnea syndrome (OSAHS) diagnosis. By using multilayer polyacrylonitrile and “polyamide 66” nanofibers as the contact pairs, and deposited gold as the electrodes, a contact-separation type of TENG-based all-nanofiber e-skin is developed. The e-skin has a peak power density of 330 mW m⁻², high pressure sensitivity of 0.217 kPa⁻¹, excellent working stability, and good air permeability. Therefore, the e-skin is simultaneously capable of energy autonomy and accurate real-time subtle respiration monitoring. Meanwhile, a self-powered diagnostic system for real-time detection and severity evaluation of obstructive sleep apnea-hypopnea syndrome are further developed to prevent the occurrence of OSAHS, delay its development, and improve sleep quality. This study hopes to pave a new and practical pathway for real-time respiration monitoring and sleep breathing diseases clinical detection.     

A Self-Healing Triboelectric Nanogenerator Based on Feathers for Sensing and Energy Harvesting

A useful direction to solve the energy problem is the effective repeated use of biomaterial for mechanical energy collection and sensing applications. Here, a feather-based single-electrode triboelectric nanogenerator (F-STENG) by only sputtering copper atoms on the feathers are presented. The feather of F-STENG, as a natural material, has environmental friendliness, which is different from the polymer materials of other triboelectric nanogenerators. F-STENG has super durability due to its feather structure self-healing property. The device has a high output voltage of 90 V and an output current of 3.5 µA. After breaking and self-healing lots of times, the output performance is also 80% of the original. F-STENG has a high sensitivity to temperature, humidity, and wind speed, and the sensitivity is 0.50 V °C⁻¹, -0.98 V RH⁻¹, and 1.67 μA m⁻¹ s⁻¹. The output power of F-STENG is 0.62 mW g⁻¹, which can realize global positioning and photographing to solve the module energy consumption problem. F-STENG provides an effective way for the application of self-powered sensors and equipment in military, industrial, transportation, and daily life.     

Large‐Scale and Washable Smart Textiles Based on Triboelectric Nanogenerator Arrays for Self‐Powered Sleeping Monitoring

Sleeping disorder is a major health threatening in high‐pace modern society. Characterizing sleep behavior with pressure‐sensitive, simple fabrication, and decent washability still remains a challenge and highly desired. Here, a pressure‐sensitive, large‐scale, and washable smart textile is reported based on triboelectric nanogenerator (TENG) array as bedsheet for real‐time and self‐powered sleep behavior monitoring. Fabricated by conductive fibers and elastomeric materials with a wave structure, the TENG units exhibit desirable features including high sensitivity, fast response time, durability, and water resistance, and are interconnected together, forming a pressure sensor array. Furthermore, highly integrated data acquisition, processing, and wireless transmission system is established and equipped with the sensor array to realize real‐time sleep behavior monitoring and sleep quality evaluation. Moreover, the smart textile can further serve as a self‐powered warning system in the case of an aged nonhospitalized patients falling down from the bed, which will immediately inform the medical staff. This work not only paves a new way for real‐time noninvasive sleep monitoring, but also presents a new perspective for the practical applications of remote clinical medical service.     

Stretchable,Washable, and Ultrathin Triboelectric Nanogenerators as Skin-Like Highly Sensitive Self-Powered Haptic Sensors

Accompanying the boom in multifunctional wearable electronics, flexible, sustainable, and wearable power sources are facing great challenges. Here, a stretchable, washable, and ultrathin skin-inspired triboelectric nanogenerator (SI-TENG) to harvest human motion energy and act as a highly sensitive self-powered haptic sensor is reported. With the optimized material selections and structure design, the SI-TENG is bestowed with some merits, such as stretchability ( ≈ 800%), ultrathin ( ≈ 89 µ m), and light-weight ( ≈ 0.23 g), which conformally attach on human skin without disturbing its contact. A stretchable composite electrode, which is formed by homogenously intertwining silver nanowires (AgNWs) with thermoplastic polyurethane (TPU) nanofiber networks, is fabricated through synchronous electrospinning of TPU and electrospraying of AgNWs. Based on the triboelectrification effect, the open-circuit voltage, short-circuit current, and power density of the SI-TENG with a contact area of 2 × 2 cm² and an applied force of 8 N can reach 95 V, 0.3 µ A, and 6 mW m⁻², respectively. By integrating the signal-processing circuits, the SI-TENG with excellent energy harvesting and self-powered sensing capability is demonstrated as a haptic sensor array to detect human actions. The SI-TENG exhibits extensive applications in the fields of human–machine interface and security systems.     

Thermal-Triggered “On–Off” Switchable Triboelectric Nanogenerator Based on Two-Way Shape Memory Polymer

Developing multifunctional triboelectric nanogenerators (TENGs) with special intelligence is of great significance for next-generation self-powered electronic devices. However, the relevant work on the intelligent TENGs, especially those spontaneously responsive to external stimuli, is rarely reported. Herein, an intelligent TENG with thermal-triggered switchable functionality and high triboelectric outputs is developed by designing a movable triboelectric layer, which is driven by a two-way shape memory polyurethane. The resultant TENG device can be spontaneously switched on/off in response to the environmental temperature change, i.e., switching on at 0 °C and off at 60 °C. At the “on” state, the developed TENG exhibits excellent triboelectric performance with a maximum output power density of 5.15 W m⁻² at a pressure of 30 kPa due to the unique advantages of micro-/nanofiber triboelectric surfaces. Furthermore, the great potential of the switchable TENG in intelligent wearable electronic applications is demonstrated, which can serve as not only the sensing element for monitoring human movement and physical condition in a cold environment but also the thermal-driven switch for turning on/off the heating function on demand. The intelligent “on–off” switchable TENG combined with excellent triboelectric performance may provide new opportunities for future self-powered wearable electronics.     

Self‐Powered Vehicle Emission Testing System Based on Coupling of Triboelectric and Chemoresistive Effects

Traditional triboelectric nanogenerator (TENG)‐based self‐powered chemical‐sensing systems are demonstrated by measuring the triboelectric effect of the sensing materials altered by the external stimulus. However, the limitations of triboelectric sensing materials and instable outputs caused by ambient environment significantly restrict their practical applications. In this work, a stable and reliable self‐powered chemical‐sensing system is proposed by coupling triboelectric effect and chemoresistive effect. The whole system is constructed as the demo of a self‐powered vehicle emission test system by connecting a vertical contact–separate mode TENG as energy harvester with a series‐connection resistance‐type gas sensor as exhaust detector and the parallel‐connection commercial light‐emitting diodes (LEDs) as alarm. The output voltage of TENG varies with the variable working states of the gas sensor and then directly reflects on the on/off status of the LEDs. The working mechanism can be ascribed to the specific output characteristics of the TENG tuned by the load resistance of the gas sensor, which is responded to the gas environment. This self‐powered sensing system is not affected by working frequency and requires no external power supply, which is favorable to improve the stability and reliability for practical application.     

Rubik-Cube-Based Self-Powered Sensors and System: An Approach toward Smart Toys

Triboelectric nanogenerator (TENG) is an effective approach for self-powered systems. Here, a second-order Rubik-cube-based TENG (SRC-TENG) is designed, which can harvest the internal sliding energy of the Rubik cube. The influence of different rotation speeds, different strengths, and effective contact area on the output performance of SRC-TENG is studied. When the SRC-TENG rotates with a high speed, light strength, and the contact area is 8 cm², the maximum open-circuit voltage and short-circuit current can reach up to 35 V and 1.45 µ A, respectively, which are enough to light up dozens of light-emitting diodes (LEDs) and charge commercial capacitors. In addition, the SRC-TENG-based smart toys can act as self-powered sensors to be applied in smart home. More importantly, the movement trajectory of the Rubik cube in the process of recovery can also be tracked in different directions of X, Y, and Z. The proposed SRC-TENG is low cost and has great potential to replace battery-powered electronic toys, which can open a new path for the next-generation commercial toys.     

A novel interface circuit for triboelectric nanogenerator

For most triboelectric nanogenerators (TENGs), the electric output should be a short AC pulse, which has the common characteristic of high voltage but low current. Thus it is necessary to convert the AC to DC and store the electric energy before driving conventional electronics. The traditional AC voltage regulator circuit which commonly consists of transformer, rectifier bridge, filter capacitor, and voltage regulator diode is not suitable for the TENG because the transformer''s consumption of power is appreciable if the TENG output is small. This article describes an innovative design of an interface circuit for a triboelectric nanogenerator that is transformerless and easily integrated. The circuit consists of large-capacity electrolytic capacitors that can realize to intermittently charge lithium-ion batteries and the control section contains the charging chip, the rectifying circuit, a comparator chip and switch chip. More important, the whole interface circuit is completely self-powered and self-controlled. Meanwhile, the chip is widely used in the circuit, so it is convenient to integrate into PCB. In short, this work presents a novel interface circuit for TENGs and makes progress to the practical application and industrialization of nanogenerators.