High-performance Triboelectric Nanogenerators Research Articles

Harsh Environmental-Tolerant and High-Performance Triboelectric Nanogenerator Based on Nanofiber/Microsphere Hybrid Membranes.

Triboelectric nanogenerator (TENG) can convert tiny mechanical energy into precious electrical energy. Constant improvements to the output performance of TENG is not only the driving force for its sustainable development, but also the key to expand its practical applicability in modern smart devices. However, most previous studies were conducted at room temperature, ignoring the influence of temperature on the output performance of TENG. Additionally, due to thermionic emission effect, the electrons transferred to a dielectric surface can be released into a vacuum after contact electrification. Therefore, TENG cannot maintain an effective electrical output under high-temperature conditions. Here, a series of high-temperature operatable flexible TENGs (HO-TENGs) based on nanofiber/microsphere hybrid membranes (FSHMs) was fabricated by electrospinning and electrospraying. The Voc of HO-TENG is 212 V, which is 2.33 times higher than that of control TENG. After 10,000 cycle stability tests, the HO-TENG shows excellent durability. Especially, this HO-TENG can maintain 77% electrical output at 70 °C compared to room temperature, showing excellent high-temperature operability. This study can not only provide a reference for the construction of advanced high-performance TENG, but also provide a certain experimental basis for efficient collection of mechanical energy in high-temperature environment and promote the application of TENG devices in harsh environments.

Design and synthesis of triboelectric polymers for high performance triboelectric nanogenerators

The latest progress, and important experimental strategies and conclusions on the design and synthesis of thetriboelectric polymers are systemically summarized. A triboelectric polymer handbook with common polymers and their properties is listed.

Flexible, humidity- and contamination-resistant superhydrophobic MXene-based electrospun triboelectric nanogenerators for distributed energy harvesting applications.

The low surface-charge density, poor stability and irreparable surface of triboelectric materials under harsh environments are still some obstacles for developing high-performance triboelectric nanogenerators (TENGs). In particular, a two-dimensional MXene material's surface is likely to be corroded by water molecules under high humidity conditions owing to its hydrophilic nature, limiting the output performance and stability of TENGs. Herein, an approach for fabricating a humidity- and contamination-resistant MXene-based TENG is established using the electrospinning technique. First, nanofibrous layers of MXene/MoS2 composites blended in a cellulosic polymer matrix were prepared, benefitting the high surface roughness and controlled air-trapping pores. Furthermore, the prepared nanofibrous layers were chemically modified with stearic acid (SA), which enhances the hydrophobicity and electronegativity of MXene/MoS2 composites. In a typical synthesis, four different compositions of MXene/MoS2/cellulose acetate nanofibers were prepared, which illustrates that an increasing concentration of MoS2 could effectively tune the surface oxidation, hydrophilic nature, and surface roughness of MXene as well as induce a piezoelectricity-enhanced triboelectric potential. On the other side, the SA modification ultimately generated a superhydrophobic surface with low surface energy and a high water contact angle of ∼154°. The integrated TENG displayed an enhanced output voltage of ∼140 V and an instantaneous power density of ∼2975 mW cm-2 with long-term stability under high humidity conditions. Additionally, the self-cleaning properties were demonstrated, ensuring the sustainability and reusability of the TENG in a contaminated environment. Moreover, the fabricated MXene-based superhydrophobic layer can harvest the energy on dripping water droplets based on the liquid-solid contact-electrification TENG mode. Overall, this work paves the way for the design and development of humidity- and contamination-resistant triboelectric materials and guides the study of harvesting of distributed environmental energy efficiently.

Sustainable robust waste-recycled ocean water-resistant fly ash-carbon nanotube nanocomposite-based triboelectric nanogenerator

Herein, for the first time, we have successfully converted waste materials into a novel, sustainable, robust, ocean water- and thermal-resistant high-performance triboelectric nanogenerator device using fly ash waste and carbon nanotubes to scavenge mechanical energy.

Nafion-mediated barium titanate-polymer composite nanofibers-based triboelectric nanogenerator for self-powered smart street and home control system

Incorporation of inorganic materials into a polymer matrix has drawn significant interest, as the process can improve the mechanical and triboelectric properties of composite products. However, well dispersion and long-term stability of the developed composites remain a challenge. In this paper, we propose a novel Nafion-functionalized barium titanate nanoparticles (BaTiO3 NPs)/polyvinylidene fluoride (PVDF) composite nanofibers based high-performance triboelectric nanogenerator (NBP-TENG), which can serve as a self-powered human-machine interface for a smart control system. Specifically, our method of introducing Nafion provides an excellent dispersion of BaTiO3 into the PVDF matrix. As a result, a highly stable dispersion is maintained for almost 6 months without any noticeable precipitation or agglomeration. Consequently, the excellent dispersion enhances the effective stress transfer at the interface between the BaTiO3 and PVDF, resulting in the remarkably improved negative surface potential in the BaTiO3/PVDF homogeneous composite nanofibers. The NBP-TENG allows the generation of high output voltage, current density, and power density of 307 V, 1.8 µA/cm2, and 1.12 mW/cm2, respectively, which are enhanced by ∼ 6.3, 7.1, and 3.7 times, respectively, compared to pristine PVDF nanofibers. The NBP-TENG is capable of powering dozens of commercial LEDs connected in series by manual tapping and demonstrates stable output performance even after 10,000 cycles of repeated contact separation. Moreover, the NBP-TENG can be utilized as a self-powered human-machine interactive interface for smart street and home control systems, with the advantages of promising reliability, cost-effectiveness, energy efficiency, and practicality.

Deep Trap Boosted Ultrahigh Triboelectric Charge Density in Nanofibrous Cellulose-Based Triboelectric Nanogenerators

For their use in self-powered implantable or wearable electronics, cellulose nanofiber (CNF)-based triboelectric nanogenerators (TENGs) have drawn a lot of attention. However, the low triboelectric charge density (TECD) hinders its further application as a tribolayer for TENGs. In this work, a sulfonated cellulose nanofiber was prepared as an electropositive tribolayer for TENGs to obtain ultrahigh electrical output performance. Since the introduction of sulfonic acid effectively increased the dielectric properties and hole deep trap density of the CNF film, the triboelectric charge storage capacity of the CNF-SO3Na film was improved. The results showed that the TECD of the CNF-SO3Na film increased by 460% compared with the pristine CNF film. Furthermore, the dielectric constant and deep trap density of the CNF-SO3Na film increased by 2.4 times and 8.1 times. This work encourages the use of TENGs in real-world wireless transmission applications by outlining an easy and effective method for building high-performance TENGs.

Physically doped and printed elastomer films as flexible high-performance triboelectric nanogenerator for self-powered mechanoelectric sensor for recovering voice and monitoring heart rate

Flexible triboelectric nanogenerator (f-TENG) is usually fabricated from elastomer. However, elastomer is generally not as effective as fluorine or amine plastics in gaining or donating electrons, which compromises the electrical performance of the fabricated f-TENG. Herein, this study demonstrates a simple solution-casting based physical doping strategy to develop high-performance triboelectric elastomer films and f-TENGs. Styrenic elastomer film was physically doped using various fluorines or amines. The doped elastomer films were further printed with flexible silver electrodes and then were used to construct a wide spectrum of f-TENGs. Remarkably, at vertical contact-separation mode, the f-TENG fabricated from the trifluoroacetic acid and polystyrene-bound triazabicyclodecene respectively doped films generated up to 385 V voltage with maximum 39.7 μA/cm2 current density and 15.1 mW/cm2 power density. This f-TENG also effectively converted a wide range of low-frequency body motions (run, walk, finger bending, throat vibration, and heart electrical impulse) to electricity. This f-TENG enables to develop self-powered real-time mechanoelectric sensor for recovering voice and monitoring heart rate. The results also indicated that trifluoroacetic acid was generally more effective than other fluorines in enhancing the electron-accepting ability of styrenic elastomer film and polystyrene-bound triazabicyclodecene was more effective than other amines in enhancing the electron-donating ability of styrenic elastomer film.

Ultralarge Curvature and Extreme Rapid Degradable Porous Wood Based Flexible Triboelectric Sensor for Physical Motion Monitoring

AbstractFlexible self‐power triboelectric nanogenerators (TENGs) have attracted worldwide attention in the fields of optoelectronic systems, communication, and biomedical diagnostics due to its outstanding energy collection capacity and high output potential. Wood, as a natural and environmental friendly material with excellent mechanical properties, is an ideal material for construction of high performance TENG. Herein, a porous wood based flexible triboelectric sensor (PWFTS) as a wearable motion testing system with ultralarge folding curvature and extreme high stability for real‐time body motion monitoring is presented. With an over 180° curving angle, the output power of the PWFTS from porous wood is more than 200% compared with that from natural wood. Moreover, a rapid degradation of as low as 48 h with extremely reliable repeatability and stability leads to an ideal candidate for wearable devices. The enhancement of such PWFTS may open up opportunities in innovative applications in various triboelectric devices and flexible integrated systems.

Green-in-green biohybrids as transient biotriboelectric nanogenerators

Green self-powered devices based on biodegradable materials have attracted widespread attention. Here, we propose the construction of the transient biotriboelectric nanogenerator (TENG) using green-in-green bionanocompoites. The green-in-green nanocomposites, cellulose nanocrystal (CNC)/polyhydroxybutyrate (PHB), are prepared with a high-pressure molding method. The CNC promotes the degradation and enhances the dielectric constant of CNC/PHB. It further allows for the significant improvement of the triboelectric output of CNC/PHB-based TENG. The voltage output and current output of CNC/PHB-based TENG are 5.7 and 12.5 times higher than those of pristine PHB-based TENG, respectively. Also, the bio-TENG exhibits admirable signal stability in over 20000 cycles. Despite the high hardness of CNC/PHB, a soft but simple-structured arch sensor is successfully assembled using CNC/PHB-based TENG. It can attain the precise real-time monitoring of various human motions. This study may provide new insights into the design/fabrication of green functional materials, and initiate the next wave of innovations in eco-friendly self-powered devices.

Surface patterning strategies for performance enhancement in triboelectric nanogenerators

Triboelectrification is reported as a surface phenomenon and is explained by the electron cloud overlap model explained in the Wang transition concept. Therefore, the performance enhancement of Triboelectric Nanogenerators (TENGs) need to be explored through strategies to engineer the surfaces for increased surface contact area and surface roughness. Surface patterning strategies holds a significant role in upscaling the performance and widening the fields of application of TENGs. The current review article is dedicated to presenting various surface patterning methods, which comes under the physical modification of surfaces. Techniques such as lithography, plasma assisted methods, laser irradiation techniques, electrochemical anodization and other geometrical patterning are discussed. It is noted that the surface modification offered by laser induced graphene is effective for fabricating high performance TENGs. One of the major advantages reported with lasing polyimide and laser induced graphene composite for TENG application is that the composite could act as an electrode for both dielectric to conductor interface and metal free dielectric-dielectric interfaces. Additionally, block copolymer lithography has been identified to be an effective method for fabricating vertically aligned nanopatterned surfaces with high contact surface area. Apart from that, the pressurised plasma jets in non-thermal plasma treatment are also proved to be highly suitable for effective and selective etching of different types of surfaces. Surface texturing by electrochemical anodization has been employed on metallic substrates for developing high performance TENG electrodes. Current challenges faced by various surface patterning approaches and possible suggestions for future developments are also discussed in detail.

Theoretical boundary and optimization methodology of contact-separation triboelectric nanogenerator

Triboelectric nanogenerators (TENGs) have exhibited great potential as the promising energy harvesters in recent decades. To obtain superior output performance, advances in materials science and engineering technology have been applied to promote the surface charge density and energy output. In this work, the mathematical derivations have been developed to derive the theoretical boundary under the air breakdown restriction for contact-separation mode TENGs. Through the optimization of limitation equations, mathematical relations were deduced between the output evaluation metrics and TENGs’ design including the structural and material factors. In addition, methodologies for output performance enhancement were proposed, from which an optimized model possessing 10 μm silicone rubber as the dielectric layer exhibits 2.85 mC/m2 in surface charge density and 1.12 mJ in energy output under 2 cm separation distance. This work provides systematical analysis and comprehensive predicts for the theoretical boundary of TENGs’ capability, which gives guidance on the design and optimization for high-performance TENGs.

A Water-Driven and Low-Damping Triboelectric Nanogenerator Based on Agricultural Debris for Smart Agriculture.

The rapid progress in distributed electronics in agriculture depends on a wide range of energy supplies, such as cables and batteries. However, cable installation and maintenance are inconvenient in the agricultural environment, and the massive use of batteries will cause high replacement costs and serious environmental issues. To mitigate these problems, a water flow-driven and high-performance triboelectric nanogenerator based on agricultural debris (including derelict plant fibers and recycled greenhouse film) (AD-TENG) is developed. The precisely designed air gap and plant fiber-based dielectric brushes enable minimized frictional resistance and sustainable triboelectric charges, resulting in low damping and high performance for the AD-TENG. After nano-morphology modifications of the dielectric layer, the maximum power density of the AD-TENG increases by 64 times and reaches ≈1.24W m-2 . The practical application demonstrates that the AD-TENG realizes the recycling of agricultural debris to achieve harvesting low-frequency and low-speed water-flow energy. Besides, the AD-TENG can be used to power agricultural sensors and develop the automatic irrigation system, which alleviates the energy consumption problem of agriculture and contributes to the realization of automated and informative intelligent agriculture.

Zirconium metal-organic framework and hybridized Co-NPC@MXene nanocomposite-coated fabric for stretchable, humidity-resistant triboelectric nanogenerators and self-powered tactile sensors

High-performance triboelectric nanogenerators (TENGs) have become more attractive for energy harvesting and self-powered sensing applications. Herein, a stretchable, humidity-resistant, and high-performance multilayered TENG (M-TENG) is newly developed for self-powered biomotion and tactile sensing applications by using a zirconium metal-organic framework (MOF-525)@Ecoflex nanocomposite with a layer of Ecoflex@cobalt-nanoporous carbon (Co-NPC)@MXene. The MOF-525 improved TENG’s performance four times due to homogeneous porosity and high charge accumulation. The porous structure of the Co-NPC functions as charge traps, promoting high charge-trapping capability, while the MXene nanosheets operate as microcapacitors, improving transport-ions inside the Ecoflex@Co-NPC@MXene nanocomposite (charge-trapping and charge-transport). When the Ecoflex@Co-NPC@MXene nanocomposite was added as an intermediate layer, it captured triboelectric charges from the charge-generating layer and accumulated more negative charges, improving the M-TENG performance by 13 times. A 3D-printed microstructure is apprehended to the surface to increase contact area and humidity-resistant. Besides, knitted fabrics provide flexible electrodes due to their excellent stretchability. The as-prepared M-TENG showed excellent performance, including a power density of 25.7 W/m2, sensitivity (149 V/KPa), humidity-resistant, and stretchability (245%) which are superior to the previously reported TENGs. By exploiting the outstanding stretchability of the M-TENG and its ultra-high sensitivity to mechanical stimuli, practical applications were successfully demonstrated in low-frequency wearable biomotion monitoring, biomechanical energy harvesting, high-precision character recognition, and as a self-powered tactile sensor. Furthermore, the real-time sensing capability was demonstrated via the LabVIEW interface and virtual-reality car games control by tracing the finger. Therefore, this work is anticipated to open exciting opportunities for wearable energy harvesters, self-powered sensing systems, and human-machine interfaces.

Boosting performance of triboelectric nanogenerator via polydimethylsiloxane modified with perovskite BiFeO3 nanoparticles

ABSTRACT Triboelectric nanogenerators (TENGs) have great potential applications in the field of microelectronics. However, the low surface charge density of the triboelectric layer is one of the key problems greatly limiting its output performance. Herein, we report a high-performance TENG using BiFeO3@polydimethylsiloxane (BFO@PDMS) composite film as a triboelectric layer. The results indicate that doping a small amount of BFO particles can significantly increase the dielectric constant and surface area of the PDMS film, which maximises the surface charge density of the triboelectric layer. With an optimized doping concentration , the dielectric constant of BFO@PDMS composite film is 14.2% higher than that of the pure PDMS film. The BFO@PDMS-based TENG delivers a maximum output voltage and current of 180 V and 30 μA, corresponding to 200% and 500% increases compared with pure PDMS film, respectively, which can drive an electronic watch and light 52 LEDs, indicating potential applications in microelectronic devices.

Ultralight, Elastic, Hybrid Aerogel for Flexible/Wearable Piezoresistive Sensor and Solid-Solid/Gas-Solid Coupled Triboelectric Nanogenerator.

Aerogels have been attracting wide attentions in flexible/wearable electronics because of their light weight, excellent flexibility, and electrical conductivity. However, multifunctional aerogel-based flexible/wearable electronics for human physiological/motion monitoring, and energy harvest/supply for mobile electronics, have been seldom reported yet. In this study, a kind of hybrid aerogel (GO/CNT HA) based on graphene oxide (GO) and carboxylated multiwalled carbon nanotubes (CMWCNTs) is prepared which can not only used as piezoresistive sensors for human motion and physiological signal detections, but also as high performance triboelectric nanogenerator (TENG) coupled with both solid-solid and gas-solid contact electrifications (CE). The repeatedly loading-unloading tests with 20000 cycles exhibit its high and ultrastable piezoresistive sensor performances. Moreover, when the obtained aerogel is used as the electrode of a TENG, high electric output performance is produced due to the synergistic effect of solid-solid, and gas-solid interface CEs (3D electrification: solid-solid interface CE between the two solid electrification layers; gas-solid interface CE between the inner surface of GO/CNT HA and the air filled in the aerogel pores). This kind of aerogel promises good applications for human physiological/motion monitoring and energy harvest/supply in flexible/wearable electronics such as piezoresistive sensors and flexible TENG.

Enhanced Performance of Triboelectric Nanogenerators and Sensors via Cold Spray Particle Deposition.

In this study, a high-performance triboelectric nanogenerator (TENG) is developed based on cold spray (CS) deposition of composite material layers. Composite layers were fabricated by cold spraying of micron-scale tin (Sn) particles on aluminum (Al) and polytetrafluoroethylene (PTFE) films, which led to improved TENG performance owing to functionalized composite layers as friction layers and electrodes, respectively. As-sprayed tin composite layers not only enhanced the flow of charges by strong adhesion to the target layer but also formed a nano-microstructure on the surface of the layers, thereby increasing the surface area during friction. More importantly, the electricity generation performance was improved more than 6 times as compared to the TENG without CS deposition on it. From parametric studies, the TENG using the cold-sprayed composite layer produced an electrical potential of 1140 V for a simple structure with a 25.4 × 25.4 mm2 contact area. We also optimize the geometry and fabrication process of the TENG to increase the manufacturing efficiency while reducing the processing cost. The resultant sprayed layers and structures exhibited sustainable robustness by showing consistent electrical performance after the mechanical adhesion test. The proposed manufacturing approach is also applicable for processing three-dimensional (3D) complex layers owing to the technological convergence of a cold spray gun attached to a robotic arm, which makes possible to fabricate the 3D TENG. To elaborate, a composite layer having the shape of a 3D ball is produced, and the exercise status of the ball is monitored in real-time. The fabricated 3D ball using the TENG transmitted a distinguishable signal in real-time according to the state of the ball. The proposed TENG sensing system can be utilized as a self-powered sensor without the need of a battery, amplifier, and rectifier. The results of this study can potentially provide insights for the practical material design and fabrication of self-powered TENG systems.

Effective interfacial energy band engineering strategy toward high-performance triboelectric nanogenerator

Provided that electron transition ascribed to overlapping electron dominates the mechanism of contact electrification of triboelectric nanogenerators (TENGs), the electron transfer process occurs due to the built-up electric field between the triboelectrification surface and bottom electrode. In this work, we embed a solution-processed high-permittivity electron blocking layer (HPEBL) of LaZrO into the classical contact-separation mode TENG to build an energy barrier (ΔE > 1.3 eV) between ITO and PDMS, which could effectively block the transportation of electrons towards the bottom electrode. The surface potential decline rate of PDMS is obviously suppressed, extending the half-charge decay time by ∼3.1 times. A La0.1Zr0.9Ox HPEBL based TENG (H-TENG) demonstrates the electrical outputs with 215 V, 96.3 mA m−2 and 243.3 μC/m−2. Under the external load of 100 MΩ, the average gravimetric/volumetric power density and energy conversion efficiency can be calculated to be 59.34 μW g−1, 152.5 μW cm−3 and 39.2%, respectively. Furthermore, the dielectric behaviors of LaZrO thin films are investigated by metal–insulator-metal (MIM) devices. The Poole-Frenkel (PF) emission is found to dominate the leakage mechanism of LaZrO during operation. Consequently, increasing the relative permittivity and reducing the trap density could be indicated as the optimization orientation of HPEBL.

Surface Area Enhanced Nylon-6,6 Nanofiber Engineered Triboelectric Nanogenerator for Self-Powered Seat Monitoring Applications

High-performance triboelectric nanogenerators (TENG), generally comprised of either a pair of surface-functionalized or dielectric modulated composite frictional layers, are technically unreliable from a commercial perspective, because of the complex fabrication procedures and configurations. This work projects a surface area enforced electrospun Nylon-6,6-based TENG as the vibrational energy scavenging and seat occupation detection system. The devised TENG can derive an output response of more than 300 μA of short circuit current, 350 V of open circuit voltage, and a power density of 550 mW m–2, which is the highest compared to previously reported Nylon-based dielectric-metal contact separation-based TENGs. The seat occupation sensing was successfully evaluated during a test drive on the TENG fitted vehicle. The charging up of a 1 μF capacitor to ∼30 V in 30 s marks the potential of Nylon-6,6 as a promising material for many applications, including smart transit.

Chemical structure-based design of triboelectric materials for high-performance TENGs

Triboelectric nanogenerator (TENG) has attracted much interest due to its efficiency, flexibility and cost-effectiveness to harvest wasted mechanical energy. However, the relationship between the chemical composition and output performance of triboelectric materials is still not completely revealed. As an attempt to understand the structure-performance relationship at the molecular level, representative fluorinated poly (arylene ether)s with varying content of electron-donating groups (fluorene groups) in the backbone are synthesized and compared in the performance of TENGs. The structure-dependent performance of triboelectric materials in TENGs is closely related to the potential energy difference (∆E) between the HOMO energy level of the positive material and the LUMO energy level of the negative material. With an introduction of 50 mol% fluorene groups and the smaller ∆E, the fluorinated poly (arylene ether) (DFAFW50) contacting with PEEK provides the best output performance of the TENG, and remains stable output performance in 120,000 cycles. For fluorinated poly (arylene ether)s, the introduction of electron-donating groups makes materials tend to lose electrons. Within this effort, a potential molecular design protocol is proposed to develop high-performance positive and negative triboelectric materials applicable in TENGs.

High-Performance Triboelectric Nanogenerators Based on Commercial Textiles: Electrospun Nylon 66 Nanofibers on Silk and PVDF on Polyester.

A high-performance textile triboelectric nanogenerator is developed based on the common commercial fabrics silk and polyester (PET). Electrospun nylon 66 nanofibers were used to boost the tribo-positive performance of silk, and a poly(vinylidene difluoride) (PVDF) coating was deployed to increase the tribo-negativity of PET. The modifications confer a very significant boost in performance: output voltage and short-circuit current density increased ∼17 times (5.85 to 100 V) and ∼16 times (1.6 to 24.5 mA/m2), respectively, compared with the Silk/PET baseline. The maximum power density was 280 mW/m2 at a 4 MΩ resistance. The performance boost likely results from enhancing the tribo-positivity (and tribo-negativity) of the contact layers and from increased contact area facilitated by the electrospun nanofibers. Excellent stability and durability were demonstrated: the nylon nanofibers and PVDF coating provide high output, while the silk and PET substrate fabrics confer strength and flexibility. Rapid capacitor charging rates of 0.045 V/s (2 μF), 0.031 V/s (10 μF), and 0.011 V/s (22 μF) were demonstrated. Advantages include high output, a fully textile structure with excellent flexibility, and construction based on cost-effective commercial fabrics. The device is ideal as a power source for wearable electronic devices, and the approach can easily be deployed for other textiles.