Performance Of Triboelectric Nanogenerator Research Articles

Controlling Performance of Organic–Inorganic Hybrid Perovskite Triboelectric Nanogenerators via Chemical Composition Modulation and Electric Field‐Induced Ion Migration

AbstractIn this paper, new strategies are proposed to design high‐performance organic–inorganic hybrid perovskite (PVK)‐based triboelectric nanogenerators (TENGs) via both chemical composition modulation and electric field‐induced ion migration in the films. Both composition variation and ion migration under electric field are found to change the type of conductivity of the perovskite films, then modify their surface potentials and electron affinities. These are utilized to fabricate PVK‐based TENGs in pairs with poly‐tetrafluoroethylene (PTFE) or nylon films, respectively. Results show that PVK films are able to work as either a positive or a negative tribo‐material depending on the tribo‐material pair used; the optimal performances are obtained for PTFE/PVK TENGs using a PVK film with a MAI/PbI2 ratio of 2 and forward polarization, and for nylon/PVK TENGs using a PVK film with a MAI/PbI2 ratio of 0.4 and reverse polarization, respectively. The maximum output voltage and peak power density of PTFE/PVK TENGs are about 979 V and 24 W m−2, 2.5 and 6.5 times higher than those of TENGs with nonoptimal composition ratio or that are poorly polarized. This work provides a new material design method for high‐performance TENGs and a novel polarization strategy for TENG performance enhancement.

Q-switched pulsed laser direct writing of aluminum surface micro/nanostructure for triboelectric performance enhancement

The micro/nano surface structure of triboelectric layers possesses a critical impact on the performance of triboelectric nanogenerators (TENG). Here, we present a solution for the enhancement of the triboelectric performance by utilizing a Q-switched Pulsed Laser (QSL) that directly writes on an Aluminum surface in the net configuration. The crinkled nanostructure of the surface of Polytetrafluoroethylene (PTFE) is fabricated by the Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) technology. By adjusting the QSL source parameters, many kinds of Al/PTFE concepts of synthetic devices with built-in contact-separation could systematically be characterized. The optimal triboelectric performance was confirmed by the increase of the open-circuit voltage and the short-circuit current from 75 V to 148 V and from 6.8 μA to 9.6 μA, respectively, and by a nearly 2.5 times higher power than that of a pristine Al-based device. The real-time practical applicability of the SA-TENG concept was confirmed by the lighting up of 92 LEDs connected in series and by the charging up of a 10 μF capacitor to 1.68 V in 30 s. This work provides an effective direct writing process with a Q-switched Pulsed Laser for the fabrication of micro/nano-structures on Aluminum and for the enhancement of the output performance of TENG, which would greatly promote the TENG branding in mass manufacturing and micro-energy utilizations.

Material choices for triboelectric nanogenerators: A critical review

AbstractA triboelectric nanogenerator (TENG) is a novel technology with applications in many areas, including energy harvesting, self‐powered sensing, medication, and electronics. The materials used as triboelectric layers are diverse and include polymers, metals, and inorganic materials. The most commonly used materials are dielectric polymers such as PTFE, FEP, PDMS, and Kapton. Green materials, such as cellulose‐based materials, have recently gained increasing interest, and the performance of TENGs using cellulose materials has improved. The material choices are of great importance for TENGs since the triboelectric effects of the materials are fundamental for TENGs. To design a TENG for a particular application, several parameters need to be considered, such as power density, stability, flexibility, and sustainability. This critical review will summarize and evaluate the material choices for TENGs in different applications.image

Research methods of contact electrification: Theoretical simulation and experiment

Contact electrification (CE) is an ancient phenomenon in human history, which has been recorded more than 2600 years. Since the invention of triboelectric nanogenerators (TENGs), the CE has been widely focused again. However, the process of TENG generally includes two stages: CE and electrostatic induction. To distinguish the influence of these two effects on the performance of TENGs, this paper first reviews the generation process of four modes of TENGs and summarizes their characteristics in the stages of CE and electrostatic induction. Then, the research methods of CE are reviewed in three aspects: theory, simulation, and experiment. Finally, the prospect for future development of the research methods and applications are discussed. In brief, this paper provides an important reference for the current triboelectric researchers to frame out the efficient research methods for the behind CE mechanisms.

Effects of surface micro-structures on capacitances of the dielectric layer in triboelectric nanogenerator: A numerical simulation study

Triboelectric nanogenerator (TENG) provides a promising approach for energy harvesting and sensing. Micro-structures are often employed at dielectric layer for improving efficiency, but the effects on the electric output performance of TENG are not well understood. In this work, we conduct a numerical simulation study based on the planar capacitor analytical method to study the electric output performance for contact-separation (CS) TENG. Different from previous work, which only investigates the effects on the real contact area, this work also studies the effects of the surface micro-structures on the capacitance and the consequent effects on the electronic output performance. The separation to contact open circuit (OC) output voltage is focused on, which is widely employed for sensor applications. The effects of the capacitance variations on OC output voltages under different elastic modulus and micro-structure geometrical parameters are investigated. The results indicate that the capacitance variations can even lead up to more than 100% deviation of the OC output voltages, which confirms that the effect of the capacitance variations is also an important factor. More importantly, it is found that some existing experimental data cannot be explained/simulated by models without consideration of the capacitance variations, and it is more correct to use the ratio of real contact area to capacitance variations to predict the open circuit output voltage of TENG instead of only using contact area when the micro-structure size is larger than 10 µm. • A numerical model for calculating electric outputs of CS TENG with surface micro-structures has been proposed. • The separation to contact operation is focused. • Capacitance variations causing by the surface micro-structure deformation are considering. • Ratios of real contact area to capacitance variation are more correct to predict the OC output voltage.

Interfacial modification boosted permittivity and triboelectric performance of liquid doping composites for high-performance flexible triboelectric nanogenerators

Composites' interface is the contact area between filler and matrix, which is a critical issue in composites' permittivity and thereby of great value to improve friction composites' performance in triboelectric nanogenerators (TENGs). However, composites' interfacial influence on triboelectric performance was not clear in past years even numerous composites were prepared, which limited materials' advance of triboelectric performance. Here, a systematic investigation about the composites' interfacial influence was performed on liquid doping polydimethylsiloxane (PDMS) composites, in which interfacial area and compatibility were found with great importance to composites' permittivity and triboelectric performance. Through high preparation stirring speed and appropriate surfactant additive, interfacial modification of enlarging interfacial area and compatible interface was facilely achieved. The as-prepared composites' permittivity and triboelectric performance were remarkably promoted as compared to composites without interfacial modification, achieving 8.1-fold in output voltage and 9.5-fold in output current of pristine PDMS. Further, the composites were applied to assemble TENG for energy harvesting and movement detection. This work revealed the interface properties’ influence on composites permittivity and further demonstrated the importance of interfacial modification for enhancement of triboelectric performance, illustrating that the interface issues should be taken into consideration in doping triboelectric composites for high output performance TENG.

Theoretical modeling of triboelectric nanogenerators (TENGs)

Triboelectric nanogenerators (TENGs), using Maxwell's displacement current as the driving force, can effectively convert mechanical energy into electricity. In this work, an extensive review of theoretical models of TENGs is presented. Based on Maxwell's equations, a formal physical model is established referred to as the quasi-electrostatic model of a TENG. Since a TENG is electrically neutral at any time owing to the low operation frequency, it is conveniently regarded as a lumped circuit element. Then, using the lumped parameter equivalent circuit theory, the conventional capacitive model and Norton's equivalent circuit model are derived. Optimal conditions for power, voltage, and total energy conversion efficiency can be calculated. The presented TENG models provide an effective theoretical foundation for understanding and predicting the performance of TENGs for practical applications.

Enhancement of Triboelectric Charge Density by Chemical Functionalization

AbstractA triboelectric nanogenerator (TENG) can convert energy in the surrounding environment to electricity. Therefore, in recent years, research related to TENGs has significantly increased owing to its simple and low‐cost manufacturing process, high portability, and high efficiency. The principle of the TENG lies in the coupling effect of contact electrification and electrostatic induction. Its output performance is directly proportional to the square of the surface charge density, which is related to friction materials. To increase the output power of a TENG and continuously provide electricity for other electronic equipment, many scholars have conducted detailed studies on the triboelectric properties of materials. Particularly, there has been research interest in the chemical functionalization of TENGs due to their unique advantages, such as high triboelectric charge density, durability, stability, and self‐cleaning properties. This Progress Report highlights the research progress in chemical modification methods for improving the charge density of TENGs, and classifies their modification methods according to their mechanisms. The effects of chemical reaction, surface chemical treatment, and chemical substance doping on the output performance of TENGs are systematically elaborated. Furthermore, the applications of chemically modified TENG in self‐powered sensors and emerging fields, including wearable electronic devices, human‐machine interfaces, and implantable electronic devices, are introduced. Lastly, the challenges faced in the future developments of chemical modification methods are discussed, thereby guiding researchers to the use of chemical modification methods for the improvement of charge density for further exploration.

Origami triboelectric nanogenerator with double-helical structure for environmental energy harvesting

Triboelectric nanogenerators (TENGs) based on contact electrification and electrostatic induction have emerged as promising green and clean energy harvesting devices. Its most unique property is that it can harvest low-frequency waste mechanical energy from the environment to electricity with high conversion efficiency. To improve the output power of TENGs, a lot of efforts have been done on fabrication of textured contact surface which leads to higher fabrication cost. In this work, inspired by the origami technology, we have designed a novel double helix structure TENGs (dh-TENG) with low cost and ease fabricating process. The dh-TENG can switch from 2D to 3D freely and significantly improve the output performance of TENG. Several factors, such as the input frequency, resistive load together with various structural parameters, were systematically investigated; the working mechanism of the dh-TENG was studied by using the COMSOL software. The experimental results show that the maximum output power of the dh-TENG reaches 0.58 mW when the external load resistance is 20 MΩ, which can fully power electronic devices such as capacitors and LEDs. These findings provide useful guidance for optimizing the performance of dh-TENGs for practical applications in self-powered systems and portable mobile electronic products, especially on soft electronics and wearable electronics.

Enhanced output in polyvinylidene fluoride nanofibers based triboelectric nanogenerator by using printer ink as nano-fillers

Abstract Triboelectric nanogenerators (TENGs) are expected to be new energy supply devices for wearable electronics, which have been proven effective in converting biomechanical energy into electrical energy. Polyvinylidene fluoride (PVDF) is a ferroelectric and piezoelectric material for TENGs, with high crystallinity of which could improve the performance of TENGs. In this work, we have developed TENGs based on PVDF in nanofiber (NF) form, which have high crystallinity. Electro-spinning technique was used to grow PVDF NFs. Commercially available printer ink (PI) nano-fillers were added in PVDF NFs to further increase their crystallinity for enhanced output of PVDF-PI NFs based TENGs. Highest β phase crystallinity of 88%, as quantified by Fourier transform infrared spectroscopy, was obtained for 5 h-grown PVDF-PI NFs, with a TENG performance of 22 W/m2, more than double that of PVDF NFs counterpart, which is so far the highest recorded value for PVDF NFs based TENGs. This can be attributed to a competition among ferroelectric domain alignment, surface charge density, and NF medium properties. As printer ink contains magnetic materials, the relation of magnetic properties to the β phase and the power output as a function of growth time have been discussed. We have also demonstrated that PVDF-PI NFs based TENGs can be efficiently used in several potential applications, such as humidity sensors, and easily integrated into flexible electrical and optoelectronic systems, which may open a new avenue in the era of self-powered electronics.

Fabrication of flexible self-powered humidity sensor based on super-hydrophilic titanium oxide nanotube arrays

Stable and flexible super-hydrophilic nanotubular-based titanium oxide electrode has been utilized as the active electrode of self-powered humidity sensor. TiO2 nanotubular electrodes fabricated through anodization method and utilized in combination with Kapton electrode as the triboelectric nanogenerator (TENG). Vertical contact-separation mode TENG performance has been examined in various range of frequencies and the maximum output voltage and current more than 300 V and 40 μA respectively with maximum power of 1.25 ± 0.67 mW has been achieved at 4 Hz. The fabricated TENG has been employed as the active self-powered humidity sensor. Super-hydrophilic feature of TiO2 nanotubes resulted in full absorption of water molecules, and noticeable decrease in charge transfer across two triboelectric materials upon increasing humidity. The TiO2-based TENG sensor was exposed to various relative humidity (RH) and the results showed that by increasing the humidity the output voltage and output current decreased from 162.24 ± 35.99 V and 20.4 ± 4.93 μA at RH = 20% to 37.92 ± 1.54 V at RH = 79% and 40.87 88 6.88 ± 1.7 μA at RH = 84%, respectively, Which shows the responsivity more than 300%. This method of measuring humidity has a simple and cost-effective fabrication that has various applications in many fields such as industry and medicine.

Toward High‐Performance Triboelectric Nanogenerators by Engineering Interfaces at the Nanoscale: Looking into the Future Research Roadmap

AbstractTo meet the future need for clean and sustainable energies, there has been considerable interest in the development of triboelectric nanogenerators (TENGs) that scavenge waste mechanical energies. The performance of a TENG at the macroscale is determined by the multifaceted role of surface and interface properties at the nanoscale, whose understanding is critical for the future development of TENGs. Therefore, various protocols from the atomic to the macrolevel for fabrication and tuning of surfaces and interfaces are required to obtain the desired TENG performance. These protocols branch out into three categories: chemical engineering, physical engineering, and structural engineering. Chemical engineering is an affordable and optimal strategy for introducing more surface polarities and higher work functions for the improvement of charge transfer. Physical engineering includes the utilization of surface morphology control, and interlayer interactions, which can enhance the active interfacial area and electron transfer capacity. Structural engineering at the macroscale, which includes device and electrode design/modifications has a considerable effect on the performance of TENGs. Future challenges and promising research directions related to the construction of next‐generation TENG devices, taking into consideration “interfaces” are also presented.

Electromagnetic Pulse Powered by a Triboelectric Nanogenerator with Applications in Accurate Self‐Powered Sensing and Security

AbstractRecent advances in the Internet of Things (IoTs) technology have accelerated the realization of micro or nano systems that necessitate not only the development of a self‐powered sensing system, but also devices that are able to protect personal security. Here, a direct ink write (DIW) 3D‐printed ultrathin fuse is fabricated and coupled with a high performance triboelectric nanogenerator (TENG). By triggering the high‐AC voltage TENG with a low‐frequency sliding motion, the fuse, which initially has low resistance, can instantly transition from a short‐circuit state to an open circuit state. Utilizing this method, a variety of self‐powered applications can be realized. Here, the first triboelectric, fully self‐powered system is demonstrated, which can accurately detect package drops without the use of a computing element or an external power source. In addition, by coupling the TENG, 3D printed fuse, and logic circuit elements, a self‐powered security device is developed, in which users are able to quickly change sensitive information if it is at risk of exposure by a single sliding motion on the TENG.

Origami-tessellation-based triboelectric nanogenerator for energy harvesting with application in road pavement

The output performance of the current origami inspired Triboelectric Nanogenerator (TENGs) are limited by the simple origami pattern used as the TENGs base. Here, we propose a kind of origami tessellation (OT) base to enhance the electric output performance of TENG and facilitate its application in road pavement for energy harvesting. The OT base provides multi layers facets to install tribo-pairs and can be driven by very small stimulation owing to the resilience of the structure. It can be operated effectively under either traction or compression depending on the initial configuration of the OT base. Besides, the foldability of the OT base makes easily the developed devices to be fitted thin gap in the road pavement. A series of mechanical tests are carried out to study the output performance of a quadrangular prism shape OT-TENG based on the Arc pattern under different boundary conditions and frequencies. To guarantee the motion synchronicity of the OT base, a strip-shape OT-TENG based on the Miura pattern is designed to obviously increase the output performance as the number of the tribo-pairs increases. Then, the tracking board test shows the potential application of the OT-TENGs for pavement vibration energy harvesting. By constructing a two-dimensional network of the OT-TENGs in pavement, the devices will provide a feasible green energy to meet the energy need of the intelligent transportation systems in the future. The outcomes of this work offer a novel OT-TENG design with great potential to dramatically enhance the output performance of TENGs devices in more general shape space and more flexible environment for vibration energy harvesting.

A unified contact force-dependent model for triboelectric nanogenerators accounting for surface roughness

Abstract Triboelectric nanogenerators (TENGs) allow generation of electricity based on charge transfer during repeated contact of suitably chosen surfaces. Recently, rapid advances have been made in boosting their performance, but advancement in fundamental understanding has progressed more slowly. Currently, the most popular TENG models assume idealized flat surfaces that guarantee complete contact and a contact force (or load)-independent response. However, all real surfaces possess some level of surface roughness which is known to produce a load-dependent contact area. We develop a new unified model (for dielectric-to-dielectric TENGs) which adds consideration of surface roughness to the established distance-dependent electric field model. We account for surface roughness by applying Persson's contact theory to determine the load-dependent contact area. The model is applicable from first touch to nearly complete contact provided deformation remains elastic. Compared to load-independent approaches, the presented model is a better predictor of TENG performance. It captures the load-dependent nature of TENG performance apparent in recent tests. It predicts that the electrical output can be expected to be tiny at low contact loads, but should converge to an upper-bound at higher loads as the contact area approaches complete contact. Comparison with test results reveal substantially better prediction of open circuit voltage V O C compared to load-independent models which tend to overestimate V O C considerably. By assisting the designers with better predictions of TENG output, the developed unified theory has huge potential for advancing the use of TENGs in applications such as wearables (i.e. low loads) to tidal or wave energy (i.e. large loads).

Highly porous and thermally stable tribopositive hybrid bimetallic cryogel to boost up the performance of triboelectric nanogenerators

Highly porous and thermally stable tribopositive hybrid bimetallic cryogel to boost up the performance of triboelectric nanogenerators

Theoretical foundations of triboelectric nanogenerators (TENGs)

Triboelectric nanogenerator (TENG) is an emerging powerful technology for converting ambient mechanical energy into electrical energy through the effect of triboelectricity. Starting from the expanded Maxwell’s equations, the theoretical framework of TENGs has been gradually established. Here, a review is given about its recent progress in constructing of this general theory. The fundamental mechanism of TENGs is constructed by the driving force—Maxwell’s displacement current, which is essentially different from that of electromagnetic generators. Theoretical calculations of the displacement current from a three-dimensional mathematical model are presented, as well as the theoretical studies on the TENGs according to the capacitor models. Furthermore, the figure-of-merits and standards for quantifying the TENG’s output characteristics are discussed, which will provide important guidelines for optimizing the structure and performance of TENGs toward practical applications. Finally, perspectives and challenges are proposed about the basic theory of TENGs and its future technology development.

A high-performance transparent and flexible triboelectric nanogenerator based on hydrophobic composite films

The modern portable and wearable electronic devices have been put forward a claim on flexibility, transparency and lightweight. Triboelectric nanogenerator (TENG) has attracted great attention as basic component of independent power source due to its outstanding characteristics. Here, a simple and efficient approach was demonstrated to modify poly-(dimethylsiloxane) (PDMS) in order to both improve the output electrical performance of TENG and optimize its hydrophobility as well. The 4 cm2 TENG consisting of PDMS-perfluorododecyl trichlorosilane (FDTS) friction layer and copper nanowires (Cu NWs)/reduced graphene oxide (RGO) electrode, exhibits high output voltage and large transfer charge quantity of 125 V and 80 nC, where the corresponding electrical performances are larger with several times than that of pristine PDMS-based TENG. A voltage of 105.8V can be obtained even under the ambient condition with high humidity of ~60%. The improvements are attributed to the reaction between FDTS and PDMS, introducing fluorine element to absorb more electrons and increasing dielectric constant. Moreover, the fabricated TENG remains high visible transmittance (70.1%) and good flexibility as energy sources which can satisfy the demands of portable and wearable electronic devices.

Contributions of Different Functional Groups to Contact Electrification of Polymers.

Polymers are commonly used to fabricate triboelectric nanogenerators (TENGs). Here, several polymer films with similar main chains but different functional groups on the side chain are employed to clarify the contributions of each functional group to contact electrification (CE). The results show that the electron-withdrawing (EW) ability and density of these functional groups on the main chain can determine both the polarity and density of CE-induced surface charges. Similar results are obtained for CE in both the polymer-polymer and polymer-liquid modes. A theoretical mechanism involving electron cloud overlap is proposed to explain all of these results. More importantly, the unsaturated groups on poly(tetrafluoroethylene) molecular chain are proved to have a much stronger EW ability than the saturated groups. The density of these unsaturated groups can be increased using a sputtering technique, suggesting that this is a facile and effective method of enhancing the performance of TENGs. These results clarify the correlation between the molecular structure and macroscopic electrification behavior of polymers.

Exploring the theoretical and experimental optimization of high-performance triboelectric nanogenerators using microarchitectured silk cocoon films

Triboelectric nanogenerators (TENGs) developed using eco-friendly natural materials instead of traditional electronic materials are more favorable for biocompatible applications, as well as from a sustainable life-cycle analysis perspective. Microarchitectured silkworm fibroin films with high surface roughness and an outstanding ability to lose electrons are used to design TENGs. An alcohol-annealing treatment is utilized to strengthen the resistance of the silk film (SF) against humidity and aqueous solubility. Herein, for the first time, the distance-dependent electric field theoretical model is employed to optimize the TENG parameters to achieve high output, which shows excellent agreement with the experimental outputs of SF-based TENG. The alcohol-treated microarchitectured SF (AT-MASF) with a polytetrafluoroethylene positive contact exhibits a stable and high electrical output even in harsh environments. These studies can lead us closer to the attractive future vision of realizing biodegradable TENG systems for harness/sensing various biomechanical activities even under real/humid environments. The potential and real-time application of the proposed AT-MASF-based TENG is demonstrated by directly employing its electric power to drive a number of low-power portable electronics and for sensing in human-body centric activities. • Silk film with high surface roughness was proposed by an inexpensive technique for TENGs. • The alcohol-annealing treatment was performed to strengthen such silk film against humidity and aqueous solubility. • The novel DDEF model was adopted to theoretically investigate the optimum triboelectric material opposite to the SF. • The surface roughness effect of silk film on the performance of TENG is also investigated by DDEF model. • The feasibility of AT-MASF-TENG is demonstrated by sensing daily human-activities.