A Review of Contact Electrification at Diversified Interfaces and Related Applications on Triboelectric Nanogenerator

The triboelectric nanogenerator(TENG)can effectively collect energy based on contact electrification(CE)at diverse interfaces,including solid–solid,liquid–solid,liquid–liquid,gas–solid,and gas–liquid.This enables energy harvesting from sources such as water,wind,and sound.In this review,we provide an overview of the coexistence of electron and ion transfer in the CE process.We elucidate the diverse dominant mechanisms observed at different interfaces and emphasize the interconnectedness and complementary nature of interface studies.The review also offers a comprehensive summary of the factors influencing charge transfer and the advancements in interfacial modification techniques.Additionally,we highlight the wide range of applications stemming from the distinctive characteristics of charge transfer at various interfaces.Finally,this review elucidates the future opportunities and challenges that interface CE may encounter.We anticipate that this review can offer valuable insights for future research on interface CE and facilitate the continued development and industrialization of TENG.

Advances in self-powered sports monitoring sensors based on triboelectric nanogenerators

The new era of the internet of things brings great opportunities to the field of intelligent sports.The collection and analysis of sports data are becoming more intelligent driven by the widely-distributed sensing network system.Triboelectric nanogenerators(TENGs)can collect and convert energy as selfpowered sensors,overcoming the limitations of external power supply,frequent power replacement and high-cost maintenance.Herein,we introduce the working modes and principles of TENGs,and then summarize the recent advances in self-powered sports monitoring sensors driven by TENGs in sports equipment facilities,wearable equipment and competitive sports specialities.We discuss the existing issues,i.e.,device stability,material sustainability,device design rationality,textile TENG cleanability,sports sensors safety,kinds and manufacturing of sports sensors,and data collection comprehensiveness,and finally,propose the countermeasures.This work has practical significance to the current TENG applications in sports monitoring,and TENG-based sensing technology will have a broad prospect in the field of intelligent sports in the future.

Harvesting Environment Mechanical Energy by Direct Current Triboelectric Nanogenerators

As hundreds of millions of distributed devices appear in every corner of our lives for information collection and transmission in big data era,the biggest challenge is the energy supply for these devices and the signal transmission of sensors.Triboelectric nanogenerator(TENG)as a new energy technology meets the increasing demand of today’s distributed energy supply due to its ability to convert the ambient mechanical energy into electric energy.Meanwhile,TENG can also be used as a sensing system.Direct current triboelectric nanogenerator(DC-TENG)can directly supply power to electronic devices without additional rectification.It has been one of the most important developments of TENG in recent years.Herein,we review recent progress in the novel structure designs,working mechanism and corresponding method to improve the output performance for DC-TENGs from the aspect of mechanical rectifier,tribovoltaic effect,phase control,mechanical delay switch and air-discharge.The basic theory of each mode,key merits and potential development are discussed in detail.At last,we provide a guideline for future challenges of DC-TENGs,and a strategy for improving the output performance for commercial applications.

Multidiscipline Applications of Triboelectric Nanogenerators for the Intelligent Era of Internet of Things

In the era of 5G and the Internet of things(IoTs),vari-ous human-computer interaction systems based on the integration of triboelectric nanogenerators(TENGs)and IoTs technologies dem-onstrate the feasibility of sustainable and self-powered functional systems.The rapid development of intelligent applications of IoTs based on TENGs mainly relies on supplying the harvested mechanical energy from surroundings and implementing active sensing,which have greatly changed the way of human production and daily life.This review mainly introduced the TENG applications in multidisci-pline scenarios of IoTs,including smart agriculture,smart industry,smart city,emergency monitoring,and machine learning-assisted artificial intelligence applications.The challenges and future research directions of TENG toward IoTs have also been proposed.The exten-sive developments and applications of TENG will push forward the IoTs into an energy autonomy fashion.

High-performance triboelectric nanogenerator based on ZrB_(2)/polydimethylsiloxane for metal corrosion protection

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 ZrB_(2)nanoparticles and effectively improve the dielectric constant by incorporating ZrB_(2).The open-circuit voltage and short-circuit current were 264 V and 22.9μA,respectively,and the power density of the TENGs reached 6 W·m^(-2).Furthermore,a selfpowered 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.

Hierarchical Honeycomb-Structured Electret/Triboelectric Nanogenerator for Biomechanical and Morphing Wing Energy Harvesting

Flexible,compact,lightweight and sustainable power sources are indispensable for modern wearable and personal electronics and small-unmanned aerial vehicles(UAVs).Hierarchical honeycomb has the unique merits of compact mesostructures,excellent energy absorption properties and considerable weight to strength ratios.Herein,a honeycomb-inspired triboelectric nanogenerator(h-TENG)is proposed for biomechanical and UAV morphing wing energy harvesting based on contact triboelectrification wavy surface of cellular honeycomb structure.The wavy surface comprises a multilayered thin film structure(combining polyethylene terephthalate,silver nanowires and fluorinated ethylene propylene)fabricated through high-temperature thermoplastic molding and wafer-level bonding process.With superior synchronization of large amounts of energy generation units with honeycomb cells,the manufactured h-TENG prototype produces the maximum instantaneous open-circuit voltage,short-circuit current and output power of 1207 V,68.5μA and 12.4 mW,respectively,corresponding to a remarkable peak power density of 0.275 mW cm^(−3)(or 2.48 mW g^(−1))under hand pressing excitations.Attributed to the excellent elastic property of self-rebounding honeycomb structure,the flexible and transparent h-TENG can be easily pressed,bent and integrated into shoes for real-time insole plantar pressure mapping.The lightweight and compact h-TENG is further installed into a morphing wing of small UAVs for efficiently converting the flapping energy of ailerons into electricity for the first time.This research demonstrates this new conceptualizing single h-TENG device’s versatility and viability for broad-range real-world application scenarios.

Fully Fabric-Based Triboelectric Nanogenerators as Self-Powered Human-Machine Interactive Keyboards

Combination flexible and stretchable textiles with self-powered sensors bring a novel insight into wearable functional electronics and cyber security in the era of Internet of Things.This work presents a highly flexible and self-powered fully fabric-based triboelectric nanogenerator(F-TENG)with sandwiched structure for biomechanical energy harvesting and real-time biometric authentication.The prepared F-TENG can power a digital watch by low-frequency motion and respond to the pressure change by the fall of leaves.A self-powered wearable keyboard(SPWK)is also fabricated by integrating large-area F-TENG sensor arrays,which not only can trace and record electrophysiological signals,but also can identify individuals’typing characteristics by means of the Haar wavelet.Based on these merits,the SPWK has promising applications in the realm of wearable electronics,self-powered sensors,cyber security,and artificial intelligences.

Self-charging power textiles integrating energy harvesting triboelectric nanogenerators with energy storage batteries/supercapacitors

Lightweight and flexible self-charging power systems with synchronous energy harvesting and energy storage abilities are highly desired in the era of the internet of things and artificial intelligences,which can provide stable,sustainable,and autonomous power sources for ubiquitous,distributed,and low-power wearable electronics.However,there is a lack of comprehensive review and challenging discussion on the state-of-the-art of the triboelectric nanogenetor(TENG)-based self-charging power textiles,which have a great possibility to become the future energy autonomy power sources.Herein,the recent progress of the self-charging power textiles hybridizing fiber/fabric based TENGs and fiber/fabric shaped batteries/supercapacitors is comprehensively summarized from the aspect of textile structural designs.Based on the current research status,the key bottlenecks and brighter prospects of self-charging power textiles are also discussed in the end.It is hoped that the summary and prospect of the latest research of self-charging power textiles can help relevant researchers accurately grasp the research progress,focus on the key scientific and technological issues,and promote further research and practical application process.

High-Efficiency Wastewater Purification System Based on Coupled Photoelectric–Catalytic Action Provided by Triboelectric Nanogenerator

It is of great importance to explore a creative route to improve the degradation e ciency of organic pollutants in wastewater.Herein,we construct a unique hybrid system by combining self-powered triboelectric nanogenerator(TENG)with carbon dots-TiO_(2)sheets doped three-dimensional graphene oxide photocatalyst(3 DGA@CDs-TNs),which can significantly enhance the degradation e ciency of brilliant green(BG)and direct blue 5 B(DB)owing to the powerful interaction of TENG and 3 DGA@CDs-TNs photocatalyst.The power output of TENG can be applied for wastewater purification directly,which exhibits a selfpowered electrocatalytic technology.Furthermore,the results also verify that TENG can replace conventional electric catalyst to remove pollutants e ectively from wastewater without any consumption.Subsequently,the unstable fragments and the plausible removal pathways of the two pollutants are proposed.Our work sheds light on the development of e cient and sustainable TENG/photocatalyst system,opening up new opportunities and possibilities for comprehensive utilization of random energy.

High Output Performance and Ultra-Durable DC Output for Triboelectric Nanogenerator Inspired by Primary Cell

Triboelectric nanogenerator(TENG)is regarded as an effective strategy to convert environment mechanical energy into electricity to meet the distributed energy demand of large number of sensors in the Internet of Things(IoTs).Although TENG based on the coupling of triboelectrification and air-breakdown achieves a large direct current(DC)output,material abrasion is a bottleneck for its applications.Here,inspired by primary cell and its DC signal output characteristics,we propose a novel primary cell structure TENG(PC-TENG)based on contact electrification and electrostatic induction,which has multiple working modes,including contact separation mode,freestanding mode and rotation mode.The PC-TENG produces DC output and operates at low surface contact force.It has an ideal effective charge density(1.02 m Cm^(-2)).Meanwhile,the PC-TENG shows a superior durability with 99% initial output after 100,000 operating cycles.Due to its excellent output performance and durability,a variety of commercial electronic devices are powered by PC-TENG via harvesting wind energy.This work offers a facile and ideal scheme for enhancing the electrical output performance of DC-TENG at low surface contact force and shows a great potential for the energy harvesting applications in IoTs.

Anti-Overturning Fully Symmetrical Triboelectric Nanogenerator Based on an Elliptic Cylindrical Structure for All-Weather Blue Energy Harvesting

Triboelectric nanogenerators(TENGs) have shown promising potential for large-scale blue energy harvesting. However, the lack of reasonable designs has largely hindered TENG from harvesting energy from both rough and tranquil seas. Herein, a fully symmetrical triboelectric nanogenerator based on an elliptical cylindrical structure(EC-TENG) is proposed for all-weather blue energy harvesting. The novel elliptical cylindrical shell provides a unique selfstability, high sensitivity to wave triggering, and most importantly, an anti-overturning capability for the EC-TENG. Moreover, benefiting from its internal symmetrical design, the EC-TENG can produce energy normally, even if it was overturned under a rude oscillation in the rough seas, which distinguishes this work from previous reported TENGs. The working mechanism and output performance are systematically studied. The as-fabricated EC-TENG is capable of lighting 400 light-emitting diodes and driving small electronics. More than that, an automatic monitoring system powered by the EC-TENG can also monitor the water level in real-time and provide an alarm if necessary. This work presents an innovative and reliable approach toward all-weather wave energy harvesting in actual marine environments.

Self-Powered,Long-Durable,and Highly Selective Oil-Solid Triboelectric Nanogenerator for Energy Harvesting and Intelligent Monitoring

Triboelectric nanogenerators(TENGs)have potential to achieve energy harvesting and condition monitoring of oils,the“lifeblood”of industry.However,oil absorption on the solid surfaces is a great challenge for oil-solid TENG(O-TENG).Here,oleophobic/superamphiphobic O-TENGs are achieved via engineering of solid surface wetting properties.The designed O-TENG can generate an excellent electricity(with a charge density of 9.1μC m^(−2) and a power density of 1.23 mW m^(−2)),which is an order of magnitude higher than other O-TENGs made from polytetrafluoroethylene and polyimide.It also has a significant durability(30,000 cycles)and can power a digital thermometer for self-powered sensor applications.Further,a superhigh-sensitivity O-TENG monitoring system is successfully developed for real-time detecting particle/water contaminants in oils.The O-TENG can detect particle contaminants at least down to 0.01 wt%and water contaminants down to 100 ppm,which are much better than previous online monitoring methods(particle>0.1 wt%;water>1000 ppm).More interesting,the developed O-TENG can also distinguish water from other contaminants,which means the developed O-TENG has a highly water-selective performance.This work provides an ideal strategy for enhancing the output and durability of TENGs for oil-solid contact and opens new intelligent pathways for oil-solid energy harvesting and oil condition monitoring.

A Hybrid Biofuel and Triboelectric Nanogenerator for Bioenergy Harvesting

Various types of energy exist everywhere around us,and these energies can be harvested from multiple sources to power micro-/nanoelectronic system and even personal electronic products.In this work,we proposed a hybrid energy-harvesting system(HEHS)for potential in vivo applications.The HEHS consisted of a triboelectric nanogenerator and a glucose fuel cell for simultaneously harvesting biomechanical energy and biochemical energy in simulated body fluid.These two energy-harvesting units can work individually as a single power source or work simultaneously as an integrated system.This design strengthened the flexibility of harvesting multiple energies and enhanced corresponding electric output.Compared with any individual device,the integrated HEHS outputs a superimposed current and has a faster charging rate.Using the harvested energy,HEHS can power a calculator or a green light-emitting diode pattern.Considering the widely existed biomechanical energy and glucose molecules in the body,the developed HEHS can be a promising candidate for building in vivo self-powered healthcare monitoring system.

Woven fabric triboelectric nanogenerators for human-computer interaction and physical health monitoring

Triboelectric nanogenerator(TENG)converts mechanical energy into valuable electrical energy,offering a solution for future energy needs.As an indispensable part of TENG,textile TENG(T-TENG)has incredible advantages in harvesting biomechanical energy and physiological signal monitoring.However,the application of T-TENG is restricted,partly because the fabric structure parameter and structure on T-TENG performance have not been fully exploited.This study comprehensively investigates the effect of weaving structure on fabric TENGs(F-TENGs)for direct-weaving yarn TENGs and post-coating fabric TENGs.For direct-weaving F-TENGs,a single-yarn TENG(Y-TENG)with a core-sheath structure is fabricated using conductive yarn as the core layer yarn and polytetrafluoroethylene(PTFE)filaments as the sheath yarn.Twelve fabrics with five different sets of parameters were designed and investigated.For post-coating F-TENGs,fabrics with weaving structures of plain,twill,satin,and reinforced twill were fabricated and coated with conductive silver paint.Overall,the twill F-TENGs have the best electrical outputs,followed by the satin F-TENGs and plain weave F-TENGs.Besides,the increase of the Y-TENG gap spacing was demonstrated to improve the electrical output performance.Moreover,T-TENGs are demonstrated for human-computer interaction and self-powered real-time monitoring.This systematic work provides guidance for the future T-TENG’s design.

A columnar multi-layer sliding triboelectric nanogenerator for water wave energy harvesting independent of wave height and direction

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/m^(3) 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.

Robust, breathable, and chemical-resistant polytetrafluoroethylene (PTFE) films achieved by novel in-situ fibrillation strategy for highperformance triboelectric nanogenerators

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/10.8μA and 54 V/14μA 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.

Self-powered flexible fingerprint-recognition display based on a triboelectric nanogenerator

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,63μA,and 152 nC,which enables easy lighting of BaTiO_(3)^(-)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.

Triboelectric nanogenerator hybrid array driven by multiform natural energies and its applications in self-powered cathodic protection

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 thing, 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 selfpowered 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.

Advances in Triboelectric Nanogenerators for Blue Energy Harvesting and Marine Environmental Monitoring

Blue energy,which includes rainfall,tidal current,wave,and water-flow energy,is a promising renewable resource,although its exploitation is limited by current technologies and thus remains low.This form of energy is mainly harvested by electromagnetic generators(EMGs),which generate electricity via Lorenz force-driven electron flows.Triboelectric nano genera tors(TENGs)and TENG networks exhibit superiority over EMGs in low-frequency and high-entropy energy harvesting as a new approach for blue energy harvesting.A TENG produces electrical outputs by adopting the mechanism of Maxwell’s displacement current.To date,a series of research efforts have been made to optimize the structure and performance of TENGs for effective blue energy harvesting and marine environmental applications.Despite the great progress that has been achieved in the use of TENGs in this context so far,continuous exploration is required in energy conversion,device durability,power management,and environmental applications.This review reports on advances in TENGs for blue energy harvesting and marine environmental monitoring.It introduces the theoretical foundations of TENGs and discusses advanced TENG prototypes for blue energy harvesting,including TENG structures that function in freestanding and contact-separation modes.Performance enhancement strategies for TENGs intended for blue energy harvesting are also summarized.Finally,marine environmental applications of TENGs based on blue energy harvesting are discussed.

Soft-bionic-fishtail structured triboelectric nanogenerator driven by flow-induced vibration for low-velocity water flow energy harvesting

To adapt to the low-velocity water flow closely related to human life,the natural energy can be efficiently harvested and used to power monitoring devices.Herein,a triboelectric soft fishtail(TE-SFT)driven by flow-induced vibration(FIV)effect is proposed based on the soft material synthesis technology.Specifically,inspired by the fishtail fin,a bluff body with the cross-section of fishtail-shaped is designed,and has a preferable vortex effect by fluid simulation.In power generation part,the triboelectric nanogenerator(TENG)is designed to act as an inertial pendulum structure by geometric method.Under the FIV effect,the TESFT driven by fishtail-shaped bluff body swings like a fish in the water and then brings the inertial pendulum to acquire the oscillation for harvesting energy from low-velocity water flow.The TE-SFT attains an open-circuit voltage(VOC)of 200 V to 313 V at the flow velocities of 0.24 to 0.89 m/s.Additionally,after 30 days of water immersion,the VOC of TE-SFT retains 96.81%.In demonstration,the TE-SFT is applied to power the temperature and humidity sensor through harvesting water flow energy.This work also provides a way for self-powered system based on the TENG and soft bionic fish in water environment.