Application Of Triboelectric Nanogenerator Research Articles

Self-powered artificial joint wear debris sensor based on triboelectric nanogenerator

Replacing the diseased joints with artificial prostheses has long been a common medical mean to alleviate pain or disability, in which the wear debris-induced aseptic loosening is the main mechanism for failure of artificial joint replacement. Timely and in situ detection of the wear debris is necessary to prevent further deterioration of the joint, and provides a basis for the lifetime diagnosis of artificial joint. Here, a self-powered sensor based on triboelectric nanogenerator (TENG) was developed for detecting wear debris generated in artificial joint. The TENG with polyethylene film and steel ball was designed into artificial joint configuration and fabricated by thermo-compression, which could in-situ detect the production of wear debris. Furthermore, the dependence of electrical output signals on the amount and size of the debris was investigated, which demonstrated obvious decrease in voltage with the increase in the amount and size of the particles. Finally, the fabricated sensor was tested in joint wear simulator, which achieved the real-time wear debris monitoring. This work expands the application of TENG in artificial joint wear detection, which is expected to promote the development of biomedical sensor and intelligent healthcare.

Bioinspired designs and biomimetic applications of triboelectric nanogenerators

The emerging novel power generation technology of triboelectric nanogenerators (TENGs) is attracting increasing attention due to its unlimited prospects in energy harvesting and self-powered sensing applications. The most important factors that determine TENGs’ electrical and mechanical performance include the device structure, surface morphology and the type of triboelectric material employed, all of which have been investigated in the past to optimize and enhance the performance of TENG devices. Amongst them, bioinspired designs, which mimic structures, surface morphologies, material properties and sensing/power generation mechanisms from nature, have largely benefited in terms of enhanced performance of TENGs. In addition, a variety of biomimetic applications based on TENGs have been explored due to the simple structure, self-powered property and tunable output of TENGs. In this review article, we present a comprehensive review of various researches within the specific focus of bioinspired TENGs and TENG enabled biomimetic applications. The review begins with a summary of the various bioinspired TENGs developed in the past with a comparative analysis of the various device structures, surface morphologies and materials inspired from nature and the resultant improvement in the TENG performance. Various ubiquitous sensing principles and power generation mechanisms in use in nature and their analogous artificial TENG designs are corroborated. TENG-enabled biomimetic applications in artificial electronic skins and neuromorphic devices are discussed. The paper concludes by providing a perspective towards promising directions for future research in this burgeoning field of study. • A comprehensive and comparative review of biobioinspired designs and biomimetic applications of TENGs. • TENGs with structures, surfaces, materials and sensing/power generation mechanisms inspired from nature are summarized. • TENG enabled biomimetic applications for electronic skins and neuromorphic devices are summarized. • Opportunities and challenges for bioinspired designs and biomimetic applications of TENGs are discussed.

Environment-resisted flexible high performance triboelectric nanogenerators based on ultrafast self-healing non-drying conductive organohydrogel

Triboelectric nanogenerator (TENG), a promising energy harvesting technique, has attracted intense research interests in recent years for its applicability in portable and wearable electronics. Self-powered sensors with high sensitivity based on TENG have been widely reported. However, for practical applications, the survivability of TENG in harsh working environments is a vital issue which must be addressed. Herein, we report a hydrophobic, icephobic, and ultrafast self-healing TENG with outstanding non-drying and non-freezing properties for energy harvesting and self-powered sensor. Due to the excellent environment resistance and conductive capability of organohydrogel, the TENG shows much better electrical output stability in a wide temperature range than conventional hydrogel-based TENG which suffers from being frozen at low temperature and dried at high temperature. Moreover, the ultrafast self-healing function enables the electrical output performance of the TENG rapidly restore without delay. The TENG in this work demonstrates an open-circuit voltage of 157 V, a short-circuit current of 16 µA, and a short-circuit charge of 29 nC. The maximum output power density reaches up to 710 mW m−2. This research might pave a new road for novel applications of TENG in harsh environments with reliable output performance and self-healing capability for practical applications.

Triboelectric-piezoelectric hybrid nanogenerator based on BaTiO3-Nanorods/Chitosan enhanced output performance with self-charge-pumping system

Recent advances in achieving flexible triboelectric nanogenerators (TENGs) focus widely on utilizing and modifying abundant natural biopolymer. Boosting power generation and conversion efficiency continue to prevail. In this work, three main strategies were proposed to enhance the output performance of chitosan-based TENGs; 1) hybridization with lead-free piezoelectric nanorod, 2) introduction of a soft electrode using bacterial cellulose/carbon nanotube composite to enhance contact efficiency, and 3) enhancement of charge density of the triboelectric friction layer using a self-charge pumping (SCP) module. Under the same testing conditions of 48 ± 5% relative humidity, ~0.55 Hz of frequency, ~250 N of compressive force at 25.0 ± 0.5 °C, and the combination of 7 wt% lead-free piezoelectric BaTiO3 nanorods (BT-NRs) in the chitosan matrix, the highest open-circuit voltage (Voc) of ~111.4 V, short circuit (Isc) of ~21.6 μA/cm2, and also output power density of 756 μW/cm2 was achieved. By using an integrated SCP module, the TENGs can provide a Voc, Isc and peak power output of 247.2 V, 36.7 μA/cm2 and 1568 μW/cm2, respectively. This electrical power output rises to over 4-fold more power enhancement than that of pristine chitosan TENGs. The TENGs demonstrate remarkable mechanical stability and reliability upon cyclical contact for up to 3000 times. This work provides a promising strategy for achieving high-output, eco-friendly triboelectric nanogenerators. By boosting the output performance via continuous charge pumping, ultrahigh effective charge density was achieved successfully in flexible chitosan/BT-NR biocomposites that can push output performance towards real applications of TENGs.

High-performance triboelectric nanogenerator based on electrospun PVDF-graphene nanosheet composite nanofibers for energy harvesting

Abstract As a promising sustainable power source for intelligent electronics, triboelectric nanogenerator (TENG) has attracted remarkable attention and various strategies have been sought to improve its output performance. However, most of these approaches for triboelectric materials optimization only focus on either chemical composition modulation or surface microstructure fabrication. In this work, both aspects are considered and an effective strategy is proposed to construct high performance TENGs based on polyvinylidene fluoride (PVDF) via graphene nanosheets incorporation in conjunction with electrospinning technology. Hence, a 20 × 20 mm2 TENG comprising of PVDF/G nanofibers and polyamide-6 (PA6) films demonstrates superior triboelectric performance with an output voltage of ~1511 V, a short-circuit current density of ~189 mA m−2, and a maximum peak power density of ~130.2 W m−2, nearly eight times higher than that of the PVDF-PA6 TENG. Additionally, under impedance matching condition, the PVDF/G-PA6 TENG can harvest ~74.13 μJ energy per cycle, with a time-averaged output power density of 926.65 mW m−2. Detail investigation reveals that both composition modulation with graphene and nanofiber structure fabricated through electrospinning contribute to the triboelectric performance enhancement of PVDF/G NF films. This work provides an effective strategy of simultaneously optimizing the chemical composition and surface microstructure of triboelectric materials to significantly improve the output performance of TENGs, and to further promote the widespread application of TENGs.

Active matching circuit to enhance the generated power of triboelectric nanogenerators

Converting mechanical energies to electricity using triboelectrification is one of the emerging technologies. Triboelectric nanogenerators (TENGs) have drawn much attention due to their high conversion efficiency. However, the internal capacitance of TENGs limits the currents generated and slows down the charging rate of storage elements. Such limitations restrict the amount of the generated power and the application of TENGs in areas that need high currents and power. This paper presents a solution to enhancing the output power of a TENG by devising an active on chip (IC) matching circuit. The matching circuit generates a negative capacitance to counter the effect of TENG’s internal capacitance and boosts the produced current. We implement the circuit using 130 nm CMOS technology and use a part of the generated power to provide the circuit with the needed biasing. The performance of the matching circuit is tested at different values of load capacitances. A relationship between the load and parasitic capacitances is estimated, which agrees with the simulation results. Numerical simulations show that the generated power can be greatly improved by using the matching circuit for four types of TENGs. The proposed matching circuit only consumes 6 . 4 μ W and improves the power of the TENG by 77.9% on average. • A matching architecture to improve the power generated from triboelectric nanogenerators using an active inductor circuit. • Implementing a negative impedance converter with low power consumption to generate a negative capacitance as a solution for creating an active inductor. • The matching circuit will be supplied by a small amount from the power generated from the TENG to achieve a fully integrated matching system that requires no external biasing source.

Recent progress of triboelectric nanogenerators: From fundamental theory to practical applications

AbstractFor the development of the internet of things (IoTs), big data, and artificial intelligence, widely distributed sensing network is the most essential element, which has to be driven by the energy storage unit, with a limited lifetime and environmental concerns. Given that the wide distribution and high mobility of these numerous sensors, the success of the IoTs and sustainable development of human society call for renewable distributed energy sources. Since triboelectrification effect is ubiquitous and universal in our living environment, the triboelectric nanogenerator (TENG) for mechanical energy harvesting and self‐powered sensing developed by Wang and co‐workers is one of the best choices for this energy for the new era. In this review, the recent progress of TENGs from fundamental theory to practical applications is systematically summarized. First, the mechanism of contact electrification, first principle theory, working principle, working modes, and figure of merits of the TENG are introduced. Furthermore, recent important progress in four major TENG applications, including micro/nano power sources, active self‐powered sensors, large‐scale blue energy, and direct high‐voltage power sources are reviewed. In the end, some perspectives and challenges for the future development of TENG are also discussed.image

Simultaneously Enhancing Power Density and Durability of Sliding‐Mode Triboelectric Nanogenerator via Interface Liquid Lubrication

AbstractThe sliding‐mode triboelectric nanogenerator (TENG) exhibits higher charge transfer efficiency for extracting mechanical energy than the contact–separation mode TENG, but the energy loss induced by air breakdown as well as the inferior durability seriously limits its practical applications. Here, an effective strategy via interface liquid lubrication is proposed for enhancing output performance of both sliding‐mode alternative current TENG (AC‐TENG) and direct current TENG (DC‐TENG). Due to the improved breakdown field strength requirement and reduced electrostatic field strength in the microgap between the triboelectric layer and electrode, interface liquid lubrication suppresses the interfacial electrostatic breakdown and reduces charge loss after the triboelectrification process, and thus more electrostatic charges are harvested by the AC‐TENG via electrostatic induction and the DC‐TENG via electrostatic breakdown. The maximum output power density of the lubricated sliding‐mode TENG is enhanced by more than 50% (3.45 W m−2 Hz−1) compared to the device without lubrication, and shows excellent durability over more than 500 000 operation cycles. This work provides an effective approach to improve the electric performance and durability of sliding‐mode AC‐TENG and DC‐TENG, which further promotes the practical applications of TENGs.

Screw Pump‐Type Water Triboelectric Nanogenerator for Active Water Flow Control

Triboelectric nanogenerators (TENGs) have been spotlighted due to the high efficiency, low cost, and easy accessibility. Despite their advantage, TENGs exhibit certain limitations such as a low lifetime. To overcome the limitation, the use of water–solid contact TENGs has been suggested. Most of the studies about water–solid contact TENG are focused on optimizing the device to adjust to the stagnant water or natural water movement. However, in most actual fluid machinery applications, the flow of water can be changed by mechanical components. The development of the water–solid contact TENG that actively changes water movement can broaden the application of TENGs. Herein, a screw pump TENG (SP–TENG) that can generate electricity by pumping water is developed. By analyzing contact surface area between water and screw in different screw rotational velocity and electrical difference from different electrode area, the device is able to optimize. The developed SP–TENG can light four light‐emitting diodes (LEDs) and activate temperature sensor. In addition, because SP–TENG can function as an active water TENG, it can enable the circulation of water to improve the ecosystem. Thus, SP–TENG can be used as an ecofriendly device that can simultaneously harvest energy and induce self‐purification of water.

Single-Layer Triboelectric Nanogenerators Based on Ion-Doped Natural Nanofibrils.

As emerging ambient energy harvesting technology, triboelectric nanogenerators (TENGs) have proven to be a robust power source and have demonstrated the unique ability to power micro-nano electronics autonomously to form self-powered devices. Although four working modes of TENGs have been developed to promote the feasibility of self-powered micro-nano systems, the relatively complicated structure composed of multilayer and movable components limits the practical applications of TENGs. Herein, we propose a single-layer triboelectric nanogenerator (SL-TENG) based on ion-doped natural nanofibrils. Compared with the simplest mode of currently existing TENGs, i.e., the single-electrode type, this novel single-electrode TENG further simplifies the configuration by the removal of the dielectric layer. The underlying mechanism of the proposed SL-TENG is comprehensively investigated through electrical measurements and the analysis of the effect of ion species at different concentrations. In contrast to conventional TENGs that require electrodes to realize charge transfer, it is revealed that the ions doped into natural nanofibrils effectively realize charge transfer due to the separation and migration of cations and anions. This new working principle based on the combination of electrons and ions enables TENGs to show greater potential for applications since the ultrasimple single-layer configuration enables them to be more easily integrated with other electronic components; additionally, the whole device of the proposed SL-TENG is biodegradable because the natural nanofibrils are completely extracted from carrots.

Universal Triboelectric Nanogenerator Simulation Based on Dynamic Finite Element Method Model.

The lack of a universal simulation method for triboelectric nanogenerator (TENG) makes the device design and optimization difficult before experiment, which protracts the research and development process and hinders the landing of practical TENG applications. The existing electrostatic induction models for TENGs have limitations in simulating TENGs with complex geometries and their dynamic behaviors under practical movements due to the topology change issues. Here, a dynamic finite element method (FEM) model is proposed. The introduction of air buffer layers and the moving mesh method eliminates the topology change issues during practical movement and allows simulation of dynamic and time-varying behaviors of TENGs with complex 2D/3D geometries. Systematic investigations are carried out to optimize the air buffer thickness and mesh densities, and the optimized results show excellent consistency with the experimental data and results based on other existing methods. It also shows that a 3D disk-type rotating TENG can be simulated using the model, clearly demonstrating the capability and superiority of the dynamic FEM model. Moreover, the dynamic FEM model is used to optimize the shape of the tribo-material, which is used as a preliminary example to demonstrate the possibility of designing a TENG-based sensor.

Tunable output performance of triboelectric nanogenerator based on alginate metal complex for sustainable operation of intelligent keyboard sensing system

As a renewable power source, the triboelectric nanogenerator (TENG) can effectively harvest mechanical energy and can convert it into remarkable electrical output. However, also worth considering is to exploit the new triboelectric material to promote the practical application of TENGs in the field of intelligent sensing. Here, we firstly proposed a novel multifunctional TENG based on the alginate-metallic complex (AMC-TENG), which can provide tunable electrical output via synthesis of the alginate complexes with different metal ions. Through some comparative experiments, the AMC has a strong ability to lose electrons. As displayed in the experimental results, the AMC-TENG can achieve the highest electrical output, and the order of the electrical output from high to low is Copper alginate (Alg-Cu), ferric alginate (Alg-Fe), sodium alginate (Alg-Na), magnesium alginate (Alg-Mg), and aluminum alginate (Alg-Al). Besides, we design a self-powered sensing array based on the binary-decimal conversion system to demonstrate its practical application. We all think this work can provide a new perspective and possibility for the research of multifunctional triboelectric material and the development of self-powered sensing array. • We firstly report a novel TENG based on the alginate-metallic complex (AMC-TENG) to harvest mechanical energy and provide tunable electrical output via synthesis of the alginate complexes with different metal ions. • Through a series of experiments, the AMC-TENG can achieve the highest electrical output, and the order of the electrical output from high to low is copper alginate (Alg-Cu), ferric alginate (Alg-Fe), sodium alginate (Alg-Na), magnesium alginate (Alg-Mg), and aluminum alginate (Alg-Al). • Furthermore, we measured the corresponding electrical performance of Alg-Cu complex-based TENG (size: 3 cm × 3 cm), peak values of 40.16 μA, 629 V, 83.57 nC, and 438 μW/cm 2 are realized for the short-circuit current ( I sc ), open-circuit voltage ( V oc ), transferred charge ( Q sc ), and power density, respectively. • According to the tunable electrical output function of AMC-TENG, a self-powered sensing array based on the binary-decimal conversion system has been designed, and good results have be observed.

Bio‐Derived Natural Materials Based Triboelectric Devices for Self‐Powered Ubiquitous Wearable and Implantable Intelligent Devices

AbstractThe capability of devices in future ubiquitous networked wearable and implantable electronics to efficiently scavenge and store operational power from their working environment through sustainable pathways would enable viable self‐powering schemes in societally‐pervasive applications such as advanced healthcare and robotics. Triboelectric nanogenerators (TENGs) can efficiently harvest the ubiquitous mechanical energy for powering electronics and sensors. However, the majority of demonstrated TENG prototypes have been built with materials that are not biodegradable or biocompatible, which significantly hinders the application of TENGs for wearable and implantable technologies. In this review, the recent progress of the wearable and implantable triboelectric devices built with bio‐derived natural materials is summarized. The properties of these natural biopolymers are discussed in the context of self‐powered triboelectric applications. The common manufacturing methods for processing these materials into triboelectric devices are also discussed. In addition, the applications of the bio‐derived natural materials based TENGs for in vitro and in vivo applications are discussed. Finally, the outstanding challenges and potential opportunities for the development of bio‐derived natural materials based triboelectric devices targeting wearable and implantable human‐integrated applications are analyzed.

Triboelectric nanogenerator for healthcare and biomedical applications

• A summarized view of the fundamentals of the triboelectric nanogenerator (TENG) is presented. • Promising applications in different biomedical and healthcare sectors are discussed in detail. • Future perspectives and challenges for the commercialization of TENG based healthcare devices are provided. Triboelectric nanogenerator (TENG) can convert various types of mechanical energy into electricity via coupling of contact electrification and electrostatic induction. The wide range of materials, device designs, high output power are few of the TENG advantages. The human body and internal organ motions can serve as an excellent energy source for TENG based self-powered healthcare applications. This review highlights the past 7-year development in TENG based biomedical and healthcare devices. A summary of TENG applications, including drug delivery, neural prosthesis, cell modulation, circulatory system, microbial disinfection, gene transfection, hair regeneration, biodegradable electronics, is presented. However, miniaturization, long-term stability, encapsulation, and in-vivo performance are the challenges that need to be addressed before any clinical trials. In the future, overcoming the problems will make TENG as an alternative power source for the biomedical and healthcare applications.

Simultaneous energy harvesting and signal sensing from a single triboelectric nanogenerator for intelligent self-powered wireless sensing systems

Abstract The puzzle of sustainable power and reliable signal sensing poses a tough challenge for electronic systems in the era of the Internet of Things. Fortunately, triboelectric nanogenerator (TENG), as a promising electro-mechanical conversion method, has been widely used to solve these two problems as reported. In existing reports, TENG is used either as an energy harvester or a self-powered sensor, yet it cannot undertake both demands at the same time in a single system. In this work, by proposing a method of decoupling/extracting signals and energy, energy harvesting and signal sensing in a single device were both achieved by extracting the energy and capturing signal simultaneously from a rotating triboelectric nanogenerator (R-TENG), through which a real self-powered sensing system is realized. Firstly, we proposed a R-TENG device adopting PCB manufacturing process, which can obtain energy and sense signals from external rotation. Then, we designed a decoupled signal processing unit and a reserved power management unit that supplies for the signal processing unit and an additional wireless transmission module with a microcontroller. Finally, we set up a validation system that uses wind-driven R-TENG to collect wind energy while detecting wind speed information. The collected energy powers the entire system and the measured wind speed information is successfully transmitted to the receiving end wirelessly. This method of decoupling/extracting signals and energy expands the application of TENG that it can be used as energy harvester and sensor simultaneously in a self-powered system.

Development of Highly Durable Sliding Triboelectric Nanogenerator Using Diamond-Like Carbon Films

Climate change is affecting every being on the planet. The time has arrived to give a big push for harvesting renewable energy sources, thus reducing the dependencies on fossil fuels and chemical batteries. This inspired Nanotechnologists to explore energy harvesting techniques from the environment. Triboelectric nanogenerator (TENG) is one such emerging, promising, and a reliable technology to extract micropower from the abundantly available natural mechanical energy. In this study, we have addressed the durability issues of TENG using Diamond-like Carbon (DLC) films as a triboelectric surface. Our findings indicate a high potential for DLC films for TENG applications attributing to its outstanding tribological, mechanical and insulating properties. Hydrogenated DLC (H-DLC) film, Fluorinated DLC (F-DLC) film, and PTFE were used as dielectric surfaces on a rotary based sliding-TENG. The output performance of each pair differed with the sliding frequency where H-DLC/F-DLC pair produced the maximum output at a moderate frequency of 4 Hz. As the frequency was raised, H-DLC/PTFE pair exhibited the highest output at 10 Hz, equal to that of the Al/PTFE pair. The durability evaluation of DLC-TENG showed very promising outcomes producing stable output current for 2 h. This study is expected to encourage the development of DLC-based sliding-TENGs, with enhanced durability and output efficiency.

Electron transfer mechanism of graphene/Cu heterostructure for improving the stability of triboelectric nanogenerators

Harvesting energy from the mechanical motion has been demonstrated to be a preferable strategy to satisfy the requirements for self-powered electronics. Here we report a flexible and stable induction electrode based on graphene/Cu heterostructure, which is fabricated by electrodeposition and spin-coating, and is also utilized in energy harvesting for triboelectric nanogenerator (TENG). Typically, graphene dispersion prepared by physical exfoliation is spin-coated on the copper nanostructure based on PDMS. Besides, we provide favorable evidences that electrons transfer from graphene to copper, and ignite the reduced reaction of copper oxides. The function of graphene in avoiding the oxidation of copper nanostructure, thus improving the stability of graphene/Cu heterostructure and achieving its applications in triboelectric nanogenerator, is confirmed. The interactive mechanism is formulated, including energy barrier, metal work function and the electrochemical potential difference between graphene, copper and oxygen. The enhanced stability of graphene/Cu heterostructure is inspected by the chemical state of copper as the function of exposure time, and the applicability is also evaluated by their output electrical performance for TENG applications.

Self-cleaning triboelectric nanogenerator based on TiO2 photocatalysis

Dielectric polymer materials are indispensable for the fabrication of self-powered nanosystem and electronic skin. However, the performance of the device is often seriously degraded due to the contamination of the surface. It is very important to keep the clean of the surface of the device, especially for the application of wearable devices. In this work, triboelectric nanogenerator (TENG) integrated with TiO2 photocatalysis is developed for realizing the dual functions of energy generation and self-cleaning interface. The friction layer of TENG is sponged polydimethylsiloxane (PDMS) film which is prepared by sacrificial template method with the pore size varied from hundreds of microns to several millimeters. When the interface of TENG is contaminated by organic pollutants, the open circuit voltage (VOC) of the device decrease from 125 V to 88 V. Under the solar illumination for 35 min, the self-cleaning interface can degrade the contaminants attached on the tribo-surface, while VOC raises from 88 V to 115 V after illumination, indicating that 92% of the TENG's output performance can be fully recovered. The photocatalysis-based self-cleaning effect on polymer tribo-material can contribute to the application of TENG towards e-skin and wearable devices.

Noncontact triboelectric nanogenerator for human motion monitoring and energy harvesting

Monitoring human motion and harvesting its energy is an interesting and important topic. Triboelectric nanogenerators (TENGs) have shown their potential for signal detecting and energy harvesting. In this paper, a noncontact paper-based TENG is creatively proposed to be used as a self-powered human motion monitoring sensor and also to be used for human motion energy harvesting. The noncontact mode avoids the requirement of direct physical contact between the TENG and the human subject, which fascinates the application of TENG and can increase its service life. It is found that the walking gait cycle (leg raising and falling), moving direction, walking or running speed and moving path can be reflected by the output voltage signals directly and clearly. Noncontact human motion energy harvesting is also achieved by using this TENG with a rectification circuit. It is also surprisingly found that this TENG is able to detect human motion even through a building wall, and the output voltage is strong enough to be captured by a normal multimeter without any additional amplification circuit. This study opens up a new method for self-powered noncontact human movement detecting and monitoring.

Surface charge density of triboelectric nanogenerators: Theoretical boundary and optimization methodology

Although high charge densities of triboelectric nanogenerators (TENG) were achieved by working in high vacuum or charge pumping techniques in atmosphere, owing to their complex structure and/or stability issues, it still remains a great challenge and necessity to directly obtain the high charge density directly through triboelectrification effect in atmosphere. Here, a basic theory about the limitation factors of surface charge density is comprehensively rebuilt through analytical mathematical derivation of the limitation equation. As a result, high surface charge density can be obtained directly by a new optimization methodology, i.e. using thin dielectric layer, which is demonstrated by the designed contact-separation model TENG and sliding model TENG. In addition, the theoretical models of charge decay and charge accumulation during triboelectrification process were built. This work provides not only a new facile and universal optimization methodology for TENG, but also a new insight in the triboelectrification process, both of which will prompt the applications of TENG ranging from powering electronic devices to harvesting large-scale blue energy.