Triboelectric Properties Research Articles

Defects drive the tribocharging strength of PTFE: An ab-initio study

If polytetrafluoroethylene (PTFE), commonly known as Teflon, is put into contact and rubbed against another material, almost surely it will be more effective than its counterpart in collecting negative charges. This simple, basic property is captured by the so called triboelectric series, where PTFE ranks extremely high, and that qualitatively orders materials in terms of their ability to electrostatically charge upon contact and rubbing. However, while classifying materials, the series does not provide an explanation of their triboelectric strength, besides a loose correlation with the workfunction. Indeed, despite being an extremely familiar process, known from centuries, tribocharging is still elusive and not fully understood.In this work we employ density functional theory to look for the origin of PTFE tribocharging strength. We study how charge transfers when pristine or defective PTFE is put in contact with different clean and oxidized metals. Our results show the important role played by defects in enhancing charge transfer. Interestingly and unexpectedly our results show that negatively charged chains are more stable than neutral ones, if slightly bent. Indeed deformations can be easily promoted in polymers as PTFE, especially in tribological contacts. These results suggest that, in designing materials in view of their triboelectric properties, the characteristics of their defects could be a performance determining factor.

Creating Ultrahigh and Long‐Persistent Triboelectric Charge Density on Weak Polar Polymer via Quenching Polarization

AbstractTo achieve high charge density for the triboelectric polymer is a crucial task for fabricating triboelectric nanogenerators (TENGs). This work has developed a quenching polarization (QP) method to create ultrahigh and long‐persistent triboelectric charge on the triboelectric polymer with weak dipole polarity. The Ethylene chlorotrifluoroethylene copolymer (ECTFE) film can reach a charge density of 391 µC m−2 in the vertical contact mode by using this QP treatment, which is 200% higher than the result achieved by the most widely used method of corona polarization. The mechanism of the improvement through QP on the triboelectric properties is studied on the basis of the polarization induced grain refinement and interfacial trapping. The QP‐treated ECTFE can maintain ultra‐high charge density for both solid‐solid and solid‐liquid TENG. More interestingly, the charge induced by QP treatment is so persistent that it produces a recoverable discharging phenomenon for solid‐liquid TENG, which has never been observed before. This QP method provides a different approach for fabricating high‐performance triboelectric materials, while the QP‐induced changes in crystallization and tribo‐charge density can help to complete the physical understanding of the electrification mechanism of triboelectric polymer.

A Liquid Triboelectric Series.

The triboelectric series is a generally accepted method for describing the triboelectric effect. It provides a way to control the double face of the ubiquitous triboelectric effect: causes of unpredictable accidents and the resultant surface charge as energy sources. However, previous studies have been biased in solids despite being observed in liquids (liquid-solid contact electrification). Therefore, a liquid triboelectric series is necessary to be established to manipulate the liquid triboelectric effect according to the appropriate goal. In this study, a liquid triboelectric series is first established to describe the triboelectric properties of each liquid when contact electrification occurs with a solid surface. The liquid triboelectric series covers electrolytes, organic solvents, oxidants, and higher sugar alcohols. Common chemical groups can be derived from the liquid triboelectric series that hydroxyl groups enhance, and benzene groups suppress the liquid triboelectric effect. The results are demonstrated by the amplified efficiency of an energy harvester and particle contamination after surface washing. This study will play a pivotal role in understanding the liquid-solid contact electrification phenomenon and providing new perspectives on the applications of the liquid triboelectric effect.

Molecular-functionalized metal-organic frameworks enabling contact-electro-catalytic organic decomposition

Metal-organic frameworks (MOFs) have been used in triboelectric areas for either improving the outputs or expanding some novel applications. However, research on the effects of the grafted groups of MOFs molecular to triboelectricity remains scarce. Here, we modified the MIL-101(Cr) with three groups (pyridine, amino, nitro) to obtain a series of X-MOFs (X = -PY, -NH2, -H and -NO2) and clarified their position in triboelectric series. The great electron-donating ability of pyridine granted PY-MOF positive tribo-polarity and effectively improved the power density by 9.6 times. Moreover, PY-MOF was proved as significant contact-electro-catalytic (CEC) material with degradation rate of 97% in 3 h via degradation of methylene blue (MB) dye in aqueous environment. This work shows that the modification of MOF molecular with functional groups can modulate the triboelectric properties of MOFs for largely improving the output performance and show great application prospects in the field of tribo-catalysis.

Snake ecdysis: A potential e-material for advanced electronic technology

Nature has gifted superior e-materials to many living organisms. This work investigates a keratinized hexagonal patterned snake ecdysis for advanced electronic applications. The snake ecdysis carries high porosity, flexibility, piezo-sensitivity, and tribopositivity. Furthermore, the presence of various functional groups and high keratinization are responsible for the piezo and triboelectric properties. First, we develop high-performance and impressively stable piezoelectric and triboelectric energy harvesters based on snake ecdysis. The snake ecdysis-based piezoelectric device is further utilized for various electronic applications such as speaker, microphone, and speech recognition sensor because of its outstanding wide band sensitivity. In addition, the snake ecdysis is further employed as a separator in a piezoelectric supercapacitor. The snake ecdysis/rGO-based piezoelectric supercapacitor delivers an excellent specific capacitance of 82 mF/cm2 with 72 mJ/cm2 energy density. These results suggest that snake ecdysis for energy harvesting, sensing, and storage applications could be an encouraging approach towards snake biodiversity as well as for developing sustainable self-driven electronic devices.

A biocompatible, eco-friendly, and high-performance triboelectric nanogenerator based on sepiolite, bentonite, and kaolin decorated chitosan composite film

Recent advancements in triboelectric nanogenerators (TENGs) have primarily focused on improving power conversion and generation efficiency. However, challenges still exist in developing TENGs that are affordable and biocompatible. Chitosan, an abundant natural biopolymer derived from marine crustacean shells, and natural clays offer exciting possibilities for developing cost-effective and biodegradable TENG applications. In this study, we present the development of biocompatible and eco-friendly TENGs by incorporating clay-based compounds as natural fillers into chitosan. To construct chitosan/clay-based biocomposite TENGs, we have introduced sepiolite, bentonite, and kaolin, as natural additives, into the chitosan biopolymer matrix. Decorating chitosan with natural clays improves the triboelectric properties of the TENGs, which in turn enhances the output voltage and significantly boosts the electric power density. Chitosan-based TENGs with 3 wt% sepiolite, 1 wt% bentonite, and 1 wt% kaolin demonstrate open circuit voltages of 863, 996, and 963 V, respectively. Moreover, when compared to pure chitosan-based TENG, the chitosan-based TENGs with 3 wt% sepiolite, 1 wt% bentonite, and 1 wt% kaolin show a maximum output peak power increase of 19, 54.4, and 32.6%, respectively. At 1.1 MΩ load resistance, the maximum peak electric power densities of 20.4, 26.5, and 22.8 W/m² are reached for chitosan-based TENGs with 3 wt% sepiolite, 1 wt% bentonite, and 1 wt% kaolin, respectively. Furthermore, we analyzed the surface potential, morphology, roughness, and dielectric constant of chitosan/clay composites to understand the relationship between them and electrical performance. The results demonstrate that the output performances of the chitosan/clay-based TENGs are quite high. TENGs made of biocompatible materials may not only pave the way for the production of environmentally friendly, cost-effective, and efficient TENGs for self-powered nanosystems and biomedical devices but may also shed light on new technologies utilizing natural materials.

Self-powered microbial blocking textile driven by triboelectric charges

Conventional methods of protecting against airborne pathogens, such as face masks, are typically associated with significant pressure loss and uncomfortable long-term wear. Alternative methods, such as antimicrobial textiles, can utilize nanomaterial-modified functional fabrics for effective microbial prevention, but suffer from limited treatment throughput, high cost, and potential toxicity from nanomaterial release. Herein, we develop a novel microbial-blocking textile using fabrics with opposite triboelectric properties of the outer and inner layers, which induces triboelectric charges by harvesting kinetic energy from human motion. The induced triboelectric negative charges at the outer textile layer achieve efficient airborne pathogen blocking based on electrostatic repulsion between the fabric and microbes. This self-powered, triboelectrification-induced microbial blocking system with optimized material (PTFE and nylon) and structure (rib knitted) achieves highly efficient microbial blocking (>95%) at a very high airflow rate of 2.0 m/s. In addition, the pressure drop for microbial blocking by this novel method is extremely low (<30 Pa). Our results demonstrate a promising method for rapid, self-powered blocking of airborne pathogens by incorporating triboelectric charges from human motion to meet vital public health needs.

Energy Harvesting Using Wastepaper‐Based Triboelectric Nanogenerators

Inks and toners used for printing contain materials, such as polyester, with strong triboelectric properties to enhance the binding effects, making wastepaper, such as magazines and newspapers, good candidates for triboelectric materials. Herein, high‐output power triboelectric nanogenerators (TENGs) that utilize wastepaper as triboelectric layers (wastepaper‐based triboelectric nanogenerators (WP–TENGs)) are reported. Journal paper and office copy paper wastes are investigated. The results show that the maximum power densities of the WP–TENGs reach 43.5 W m−2, which is approximately 250 times the previously reported output of the TENG with a recycled triboelectric layer made from wastepaper. The maximum open circuit voltage (V OC) and short circuit current (I SC) are 774 V and 3.92 mA (784 mA m−2), respectively. These findings can be applied to extend the life cycle of printed papers for energy harvesting, and they can later be applied for materials recycling to enhance the sustainable development of our society.

Large-scale production of the 3D warp knitted terry fabric triboelectric nanogenerators for motion monitoring and energy harvesting

In the coming era of intelligence, the textile-based triboelectric nanogenerator (T-TENG) is considered to be one of the most important development directions to achieve flexible wearable sensing and micro/nano energy harvesting. Among them, due to excellent physical proeprties of nano/micro fibrous structure, fluff/terry /fleece/brush/fur/pile/villus/velvet structure fabrics are gradually being applied to TENG. However, the research on the relationship between the triboelectric properties of TENG and the structural parameters of fluff, as well as the fabrication of large-scale fluff TENG are very lacking. Here, a 3D warp knitted terry fabric TENG (WKTF-TENG) is mass produced by a mature warp knitted technology. The triboelectric properties of contact-separation mode, lateral-sliding mode and single electrode mode are systematically investigated by changing the height and density of the pile loops of the fabric. This study demonstrates that terry fabric is an excellent triboelectric materials for it high output and good wear resistance, especially for ateral-sliding mode. The output of WKTF-TENG even increases with the increase of working cycles due to the more fluffy and uniform distribution of fibers on the surface of the fabric. What’s more, the triboelectric properties of terry fabrics also have a great relationship with the compression properties of the pile loops. As smart textile matertail, WKTF-TENG can be usde as self-powered motion monitoring sensor and energy harvesting device. The research on the output performance of WKTF-TENG through theoretical analysis and experimental testing may provides a promising direction for fluff fabric based TENG.

A Single Electronic Tattoo for Multisensory Integration.

Wearable electronics are garnering growing interest in various emerging fields including intelligent sensors, artificial limbs, and human-machine interfaces. A remaining challenge is to develop multisensory devices that can conformally adhere to the skin even during dynamic-moving environments. Here, a single electronic tattoo (E-tattoo) based on a mixed-dimensional matrix network, which integrates two-dimensional MXene nanosheets and one-dimensional cellulose nanofibers/Ag nanowires, is presented for multisensory integration. The multidimensional configurations endow the E-tattoo with excellent multifunctional sensing capabilities including temperature, humidity, in-plane strain, proximity, and material identification. In addition, benefiting from the satisfactory rheology of hybrid inks, the E-tattoos are able to be fabricated through multiple facile strategies including direct writing, stamping, screen printing, and three-dimensional printing on various hard/soft substrates. Especially, the E-tattoo with excellent triboelectric properties also can serve as a power source for activating small electronic devices. It is believed that these skin-conformal E-tattoo systems can provide a promising platform for next-generation wearable and epidermal electronics.

Self-healing fluorinated poly(urethane urea) for mechanically and environmentally stable, high performance, and versatile fully self-healing triboelectric nanogenerators

Fully self-healing triboelectric nanogenerators (TENGs) capable of recovering damaged triboelectric layers and electrodes are highly desirable as power supplies or self-powered sensors for next-generation electronics. However, the viable application of fully self-healing TENGs is limited due to their poor mechanical and environmental stabilities and output performances. These arise due to the poor mechanical strength, chemical stability, and triboelectric properties exhibited by the triboelectric layers. Herein, a self-healing fluorinated poly(urethane urea) with high mechanical strength, chemical stability, excellent healing efficiency, and outstanding triboelectric performance is synthesized. By sandwiching the self-healing fluorinated poly(urethane urea) with a self-healing ionogel, a fully self-healing TENG named FSI-TENG is obtained with an output power density of 2.75 W m−2, which is the highest compared with other reported fully self-healing TENG. Due to the mechanical strength and chemical stability of the self-healing fluorinated poly(urethane urea), the FSI-TENG exhibits a reliable electrical output performance after being stored at − 30 °C and 90 °C, immersed in corrosive solutions, bent, trampled, and even ran over by a car. Thus, the FSI-TENG can be used for high-output energy generation and as a self-powered sensor to detect water leaks, body movements, and the speed of a car. After damage, the FSI-TENG can be healed to completely restore its electrical output performance, mechanical properties, and environmental stability, ensuring its reliability and service life.

Achieving High‐Performance Triboelectric Nanogenerator by DC Pump Strategy

AbstractTriboelectric nanogenerator (TENG) has been demonstrated as a promising solution for powering widely distributed electronics in the new era of Internet of Things (IoTs), however, high‐performance TENG always relies on tribo‐materials with high triboelectric property. Herein, a simple self‐charge excitation technique that charge injection is directly realized by self‐generated electrostatic breakdown charge instead of voltage‐multiplying circuit is proposed to break through the limitation of triboelectrification. By using the designed electrostatic breakdown charge excitation TENG (EBE‐TENG), the output performance of poor tribo‐material based TENG such as polyethylene (PE) can be enhanced by 5.7 times, which even approximates that of high tribo‐material based TENG such as fluorinated ethylene propylene (FEP). Moreover, electrostatic breakdown charge excitation technique also exhibits a universal applicable ability for other different triboelectric materials. This work not only greatly simplifies the charge excitation system, but also broadens the availability of materials for achieving high‐performance TENG.

Acoustic-electric conversion and triboelectric properties of nature-driven CF-CNT based triboelectric nanogenerator for mechanical and sound energy harvesting

Currently, the world is facing severe environmental challenges such as water pollution, rising temperatures beyond the tolerable range, and air pollution. Moreover, improper waste disposal is becoming a serious concern that enhances global warming. Among the waste materials, plastic waste and cigarette butts (CBs) or cigarette filters (CFs) are causing major environmental problems. Therefore, treating these waste materials has become a critical issue. In this scenario, converting waste to energy is considered to be the most effective disposal process for discarded materials. Furthermore, integrating waste matters with nanomaterials can lead to novel technological aspects. Herein, we utilized discarded CFs and plastic waste as positive and negative tribo materials, respectively, to fabricate a triboelectric nanogenerator (TENG) device. The energy harvesting performance of the developed TENG device was investigated by adding a small amount (0.1 wt %) of carbon nanotubes (CNTs). The CNTs incorporated TENG device exhibited exceptional energy harvesting performance by generating 60 V output voltage, 1805 nA current, and 110.6 mW/m2 power density under 10 N applied force. The energy harvested by the fabricated device can efficiently light 50 green LEDs and power the LCD of a portable timer clock. The developed CF-CNT TENG device exhibited robust electrical performances under various compressive forces and showed long-term stability. Moreover, the fabricated device can be used as a sound-driven TENG device that can work effectively in broad bandwidths ranging from 100 Hz to 400 Hz. Thus reducing sound pollution and simultaneously generating green and clean energy. Therefore, we anticipate that the present study will pave the way for green energy generation and environmental remediation.

Environmentally friendly natural materials for triboelectric nanogenerators: a review

Different natural materials can be used to prepare TENGs, and their triboelectric mechanisms and properties are summarized.

Enhanced triboelectric properties of Eu2O3-doped BaTiO3/PVDF-HFP nanofibers.

Because triboelectric nanogenerators (TENGs) convert mechanical energy into electricity, they are sustainable energy sources for powering a diverse range of intelligent sensing and monitoring devices. To enhance the electrical output of polymer-based TENGs, nanofillers are commonly incorporated into polymers. In this study, we developed a simple low-temperature process for preparing high-performance ceramic powder-based TENGs comprising electrospun fibrous surfaces based on poly(vinylidene difluoride-co-hexafluoropropylene) (PVDF-HFP) and dispersed Eu2O3-doped BaTiO3 nanofillers. Herein, we discuss the effect of the modified dielectric properties and transferred charge of the electrification film on the performance of the TENGs. After incorporating the Eu2O3-doped BaTiO3 nanofiller, the maximum output voltage of the 10 wt% Eu2O3-BaTiO3/PVDF-HFP electrospun-nanofiber TENG reached as high as 1004 V with a corresponding current density of 9.9 μA cm-2. The enhancement in the triboelectric properties of the Eu2O3-BaTiO3/PVDF-HFP electrospun-nanofiber TENGs was due to their high amounts of interface polarization and transferred charge, suggesting improved capture and storage of triboelectric electrons. These Eu2O3-BaTiO3/PVDF-HFP electrospun-nanofiber TENGs could harvest mechanical energy and power electronic devices; they were robust and not affected by the operating temperature or humidity. Furthermore, we used a fabricated device as a sensor for application as a light-emitting diode dimmer switch and for the tracking of leg movement.

Influence of graphene oxide on rheology, mechanical, dielectric, and triboelectric properties of poly(vinyl alcohol) nanocomposite hydrogels prepared via a facile one step process.

The present investigation aims to develop hydrogels with higher mechanical stability for triboelectric applications by adopting a simple method to fabricate a graphene oxide (GO) incorporated poly(vinyl alcohol) (PVA) nanocomposite hydrogel. Instead of the traditional repeated freeze-thaw method, high-shear solution mixing followed by solvent exchange with deionized water was adopted. Morphological observations showed dense and undulated microstructures in the nanocomposite hydrogel with increased GO concentration. Attenuated Total Reflection Fourier Transform Infrared spectroscopy confirmed a higher degree of intermolecular H-bonding between the hydroxyl group of PVA and oxygenated groups of GO, which leads to a robust gel formation. The formation of a robust PVA/GO nanocomposite hydrogel was examined through rheological investigations at room temperature. Nanoindentation analysis estimated a significant increase in hardness and Young's modulus of the nanocomposite hydrogels. Broadband dielectric spectroscopy showed the variation of the dielectric properties of the PVA/GO nanocomposite hydrogels with increased GO concentration. The PVA/GO nanocomposite hydrogels exhibited a maximum output voltage of 3.65 V at 0.075 wt% GO content during finger tapping experiment suggesting the potential for triboelectric applications. The extensive analysis demonstrates the influence of a very low concentration of GO on the variation of the morphology, rheology, mechanical, dielectric, and triboelectric properties of PVA/GO nanocomposite hydrogels.

Antibacterial self-cleaning nylon-11/TiO2nanofiber membranes as triboelectric nanogenerators

Triboelectric nanogenerators (TENGs), among the most simple and efficient means to harvest mechanical energy, have great potential as self-powered gadgets and sensors for multipurpose applications. In this work, Nylon-11/TiO2 nanofiber membranes have been developed as a prospective tribopositive material for wearable TENG devices with superior properties of high mechanical strength, thermal stability, hydrophobicity, and antibacterial activity. The addition of TiO2 in the electrospun Nylon-11 nanofiber matrix resulted in high-quality, uniformly spun membranes with reduced fiber diameter and self-cleaning property. Incorporating TiO2 nanocrystals imparted semicrystalline nature, good physicochemical properties, enhanced piezoelectric γ phase, and antibacterial properties in the as-fabricated Nylon-11/TiO2 nanofibers, which are advantageous to wearable TENGs. 5 wt% Nylon-11/TiO2 TENGs of [2 × 2 cm2] area were found to have exceptional triboelectric properties with short circuit current (ISC) of 5.1 μA and open circuit voltage (VOC) of 56 V measured at an applied force of 10 N and frequency 10 Hz. The as-fabricated TENGs also showed extraordinary performance towards simple palm tapping with high outputs of 53 μA and 283 V, powering 80 LEDs by the rectified output.

PEO/cellulose composite paper based triboelectric nanogenerator and its application in human-health detection

Recently, cellulose paper based triboelectric nanogenerators (CPTENGs) has gained widely attention due to the development of wearable, green and miniaturized electronic products. Modification of cellulose fibers or paper is a feasible method to improve the output performance of CPTENGs, however, the simple and effective routes to improve the triboelectric property of cellulose paper still remain a challenge. Herein, we report a simple method to prepare PEO/cellulose composite paper (PEO/CCP) via mixing polyethylene oxide (PEO) with cationic cellulose fibers. Benefiting from amino groups and PEO, the composite paper exhibits higher triboelectric positive property and triboelectric charge density, thereby endowing PEO/CCP based TENG with outstanding output performance. The voltage, current and power density peak values of PEO/CCP based TENG exhibited linear relationship with amino groups content; in this instance, the performance of the TENGs can be readily adjusted by the amino groups. The voltage, current and power density of PEO/CCP based TENG can be up to 222.1 V, 4.3 μA, and 217.3 mW•m−2, respectively. Moreover, a human-health detection device based on this TENG can monitor the physiological signals such as eye muscles, respiration, heart beat and wrist pulse, promising potentials for applications in human health-care.

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.

Rational Design of Advanced Triboelectric Materials for Energy Harvesting and Emerging Applications

The properties of materials play a significant role in triboelectric nanogenerators (TENGs). Advanced triboelectric materials for TENGs have attracted tremendous attention because of their superior advantages (e.g., high specific surface area, high porosity, and customizable macrostructure). These advanced materials can be extensively applied in numerous fields, including energy harvester, wearable electronics, filtration, and self-powered sensors. Hence, designing triboelectric materials as advanced functional materials is important for the development of TENGs. Herein, the structural modification methods based on electrospinning to improve the triboelectric properties and the latest research progress in this kind of TENGs are systematically summarized. Preparation methods and design trends of nanofibers, microspheres, hierarchical structures, and doping nanomaterials are highlighted. The factors influencing the formation and properties of triboelectric materials are considered. Furthermore, the latest progress on the applications of TENGs is systematically elaborated. Finally, the challenges in the development of triboelectric materials are discussed, thereby guiding researchers in the large-scale application of TENGs.