Porous Polymer Materials in Triboelectric Nanogenerators: History
View Latest Version
Please note this is an old version of this entry, which may differ significantly from the current revision.
Contributor:
Yajun Mi
,
Zequan Zhao
,
Han Wu
,
Yin Lu
,
Ning Wang

Since the invention of the triboelectric nanogenerator (TENG), porous polymer materials (PPMs), with different geometries and topologies, have been utilized to enhance the output performance and expand the functionality of TENGs.

  • porous polymers
  • triboelectric nanogenerator
  • energy harvester
  • self-powered sensor
  • multifunctionality

1. Introduction

The integration of artificial intelligence (AI) and the Internet of Things (IoTs) is spawning rising demand for small, flexible, and portable systems that are built with renewable power sources for sustainable operation [1][2][3]. Emerging as the time requires, the TENG was invented for harvesting ambient mechanical energy that would otherwise be wasted and converts it into usable alternating current for continuously powering portable systems [4][5]. Compared to other renewable energy harvesting technologies such as solar and thermoelectric systems, TENGs have advantages in structure adaptivity, convenience of materials selection, as well as reversibility in sensing both the chemical and physical variation at the triboelectric interface [6]. By collecting energy from environmental vibration sources, as it is easily accessible in the surrounding environment as well as from our own human movements, they successfully find wide applications in high-voltage power supplies, biomedical devices, speech recording, wind speed monitoring, blue energy harvesting, and other self-powered intelligent systems [7][8][9][10][11].
Up to this point, the TENG has experienced a swift and thriving phase of growth. This encompasses everything from the intricacies of structural planning, the meticulous selection and refinement of materials, to the fine-tuning of performance, adept power management, and the dynamic exploration of applications [12][13]. Various successful approaches have been implemented to enhance the output attributes of the TENG, ensuring it meets the diverse demands for energy provision and tactile sensing across a range of applications [9][14]. For example, selecting appropriate materials, optimizing structural design, improving preparation processes, and introducing external fields. A common method to enhance TENG output performance is to introduce micro- and nano-scale morphology on the surface of triboelectric materials to increase the electrification area. However, this process often involves high-cost technologies such as anodizing, laser-assisted processing, etching, and micro-printing, which seriously hind its practical applications [15][16][17]. Additionally, intrinsic defects of dielectrics and electrodes restrict the multifunctionality of TENGs. These issues include mechanical defects such as a lack of stretchability and flexibility, limited contact area, and insufficient breathability [14][18]. Meanwhile, some specific applications require custom triboelectric materials to meet diverse characteristics and multifunctional demands. For instance, in biomedical applications, self-powered sensors that need to be mounted on living organs might require porous dielectrics to enhance breathability. In response to these challenges and requirements, there has been a notable surge of interest in the development of next-generation high-performance TENGs based on porous designs. These designs encompass both porous material and structural configurations [19][20][21].
Porous structures exhibit notable permeability for gases and liquids [22][23][24][25][26]. In this context, materials featuring a highly porous network exhibit exceptional qualities in terms of mechanical, electrical, thermal, optical, and surface properties. Porous materials can manifest in diverse forms, including aerogels, hydrogels, fibers, and foams [27][28][29]. Hydrogels are materials formed due to the swelling of water within a gel [30][31][32]. Aerogels are a unique form of hydrogel where the internal liquid is replaced by gas [33][34][35]. Fiber media of different sizes intertwine in a non-woven arrangement, providing internal pores [36][37][38][39]. Foams are defined as highly compressed gases dispersed in solids or liquids [40][41][42]. Due to the characteristics of the void units, these porous materials exhibit a wide range of exceptional properties [43]. At the same time, PPMs also possess a large specific surface area and specific volume, making them an ideal choice for membranes requiring high roughness and various applications. These diverse characteristics expand the potential of porous materials in various application fields, including thermal resistance, electromagnetic interference shielding, filtration, and high-magnetic-permeability films. The customizability and tunability of these materials allow them to meet the unique demands of different applications. The preparation and application of porous dielectrics are actively being researched, especially in the case of hydrogels and fiber materials. Abundant evidence has shown that the number and size of pores are crucial for defining the behavior of materials. Additionally, the porous structure of PPMs not only creates a rough surface but also offers an immense internal surface area, which might be beneficial for generating additional charges [44][45].
At the same time, electrostatic induction plays a crucial role in shaping the output characteristics of the TENG, wherein the TENG is conceptualized as a parallel plate capacitor comprising a dielectric layer and electrodes [46]. It is a widely acknowledged principle that the charge in a capacitor is directly linked to the surface area and inversely related to the separation between its upper and lower plates. Hence, diminishing the thickness of the dielectric layer presents another avenue for augmenting the output efficiency of TENGs. In addition to enhancing performance, advancements have been made in augmenting features like nanomechanical and optical properties. Consequently, there has been a notable shift in research focus towards incorporating porous dielectrics and electrodes in TENG design [47][48].

2. Porous Polymer Materials and Structures in TENG Design

A porous TENG is achieved by adopting PPMs (such as aerogels, hydrogels, foams, and fibers) or by designing porous structures (like textiles and yarns). Based on the material preparation method and structural design strategy, different ranges of pore sizes and dimensions can be obtained [49][50]. Generally, the pore sizes of porous materials can typically be divided into three main groups: micropores (pore diameter less than 2 nm), mesopores (pore diameter between 2 nm and 50 nm), and macropores (pore diameter greater than 50 nm). However, due to the broad range of porous materials and structures used for TENGs, ranging from a few nm (as in the case of gels) to macro mm (as in textiles and yarns), the porous designs can be categorized into five classes: ultramicropores (less than 1 nm), nanopores (1 nm to 1 mm), micropores (1 mm to 62.5 μm), mesopores (62.5 μm to 4 mm), and macropores (4 mm to 256 mm). The TENG materials and structures exhibit a range of pore sizes, spanning from 1 nm to 1 cm. Figure 1 visually depicts the diversity in pore sizes among various materials and structural configurations. PPMTENGs can be categorized based on the design of various porous materials, which include hydrogels, aerogels, fibrous media, and foams, or they can be classified based on structural design or assembly methods, such as those based on textiles and yarns [51]. Additionally, natural PPMs like wood and bamboo have also been employed in TENG technology [52][53].
Figure 1. (a) Various porous designs of TENGs: (left) material designs, including aerogel, hydrogel, fibrous medium, and foam; (right) structural designs, including textiles and yarns; (b) the working cycle of TENG in the contact separation mode, and (c) the effect of the air-gap cell on the triboelectric performance of the gapless TENG.

2.1. Porous Polymer Dielectric Materials

Dielectrics are a class of materials with specific electrical properties. They can conduct electric charges under the influence of an electric field, but they restrict the movement of charges over relatively long distances. Among them, the contact area (S) and the surface charge density (σ) are two key features of the dielectric, which together determine the amount of charge the material surface can accommodate [54][55]. As the dielectric participates in the TENG cycle, these charges migrate between the dielectrics. When an external force is applied, charges of opposite polarity are induced within the dielectric. In addition to the contact area and surface charge density, the dielectric constant (also known as the relative dielectric constant, denoted as ε) is another important material parameter affecting TENG performance. The dielectric constant describes the dielectric’s electric field response capability relative to a vacuum or air. The higher it is, the stronger the ability of the dielectric to store charges in an electric field [56][57]. Dielectrics with high dielectric constants can effectively store and release charges during the TENG cycle. When the two dielectrics separate during the TENG cycle, induced charges lead to the flow of free electrons, thereby generating induced voltage and current in the external circuit. This process provides the foundation for the electrical energy output of the TENG, and the magnitude of the output voltage and current depends on many factors, including, but not limited to, contact area, surface charge density, and dielectric constant [58][59]. Through a comprehensive analysis of existing literature, researchers can conclude that the electrical properties of dielectrics are crucial for TENG performance. Therefore, when designing and selecting dielectric materials, parameters such as contact area, surface charge density, and dielectric constant must be considered comprehensively to achieve optimized TENG system design and performance enhancement.
The unique structure of PPMs gives them a larger surface area relative to their volume, providing them with excellent contact properties [29][60]. In TENG systems, the use of porous dielectrics has become an important research direction. Researchers have explored various physical, chemical, biological, and hybrid surface modification methods, aiming to enhance the TENG’s output performance by improving the contact area of porous dielectrics [61]. PPMs exhibit a range of excellent properties, including outstanding acoustic absorption and sound damping, superior thermal resistance, and good electromagnetic interference (EMI)-shielding characteristics [62][63]. Therefore, introducing these properties into PPMTENGs enables their development in emerging application areas, especially suitable for scenarios in harsh environmental conditions and with secondary objectives.
The pores within the dielectric play the role of air gaps in the operation cycle of TENGs. Creating air gaps in TENG devices using traditional methods is a challenging task (as shown in Figure 1b). In contrast, by using the pores inside the porous dielectric to replace air gaps, the design complexity can be reduced. Various design schemes have been proposed, including arc-shaped, spring-assisted, spacer-assisted, vibrational, and spherical designs, to provide the required air gaps between dielectrics. However, these designs often struggle to withstand numerous cycles. The changing morphology of the air gaps over time can have a negative impact on the output performance of the TENG. In fact, the porous structure’s framework acts as a spacer, allowing the TENG to exhibit the functions of traditional air gaps during regular contact and separation processes. In other words, these pores can be viewed as minute air gaps in micro-TENGs, and the collective of all these pores forms a series of TENG units. In this design, the requirement for external air gaps is obviated, since the porous dielectric incorporates a network of internal pores. When pressure is exerted and the porous dielectric undergoes compression, the pore size diminishes, leading to the generation of opposing charges and, thereby, a current in the external circuit. Once the porous dielectric is fully compressed and the external force is alleviated, the empty spaces within the porous membrane start to expand until they revert to their original state [64][65]. This results in a transfer of opposite charges in the external circuit (as shown in Figure 1c).

2.1.1. Foam-Based Polymer Dielectrics

The preparation methods for porous polymer foam-based dielectrics mainly include template-assisted synthesis, foaming method, and laser-induced method. Template-assisted synthesis uses solid templates, such as salt crystals or sugar cubes, to coat the required materials on the template surface or inside. By curing or sintering and then removing the template, an interconnected porous polymer framework is formed, thus achieving precise control over the pore structure and diameter. The foaming method is a technique commonly used for producing porous-structured materials. By adding foaming agents, bubbles are produced, forming a porous structure. This method is simple, cost effective, and applicable to various materials [66][67]. The laser-induced method is an emerging technology for preparing porous foam structures, utilizing lasers to generate a thermal effect in PPMs, melting them locally, and producing bubbles to form a porous structure. This method is straightforward, highly precise, and can be used to design and create porous structures of different sizes and shapes, offering extensive application potential [42][68].
To leverage the advantages of a porous structure, in 2014, and as shown in Figure 2a, Lee et al. used polystyrene microspheres as a template to obtain a porous sponge structure, which exhibited a 10-fold increase in power compared to a flat thin-film-based TENG (FTNG). This method demonstrates its potential in the development of high-performance TENGs [69]. Similarly, Kou et al. utilized citric acid as a solid template to obtain a flexible and breathable TENG that was employed in a range of applications, including head motion monitoring and bed exit alarm functions (Figure 2b) [70]. Kim et al. developed a manufacturing method for triboelectric sponges using a sugar cube template and 3D soft lithography (Figure 2c). The resulting sponge displayed remarkable properties such as superhydrophobicity and elasticity, rendering it applicable in various fields. With identical mechanical force, the power output of the sponge was 3 times higher than that of the control group (flat PDMS film). Lastly, they also achieved a high immunity for TES in extremely humid environments [71].
Figure 2. (a) STNG’s structure and fabrication. (b) Porous PDMS and FB-TENG in single-electrode mode fabrication diagram. (c) Porous PDMS sponge fabrication using sugar particles. (d) CCTO@BT particles fabrication. Preparing flat CCTO@BT/PDMS composite film and sponge. (e) Porous PTFE thin film fabrication methods. A 3D image of the porous PTFE thin film from PTFE/DI water mixed with 50% DI water. (f) Design of the FPS-TENG. Polymer sponge characterization with SEM images of large-hole sponge with 25 wt% PDMS. (g) Illustration of a tire with pristine AF. Tire-TENG schematic. SEM images of CNT-PDMS on a PU skeleton. (h) Photos of WPS material, recycled WPS film with Cu electrode, WPS film’s SEM image, and WPS-TENG photos.
In a similar vein, as shown in Figure 2d, Lu and colleagues achieved the incorporation of high-dielectric CCTO@BT nanoparticles and pores within a PDMS structure via a feasible filling and removal process. They identified the significant influence of dielectric constant and porosity on the surface charge density and pore fraction of the dielectric in TENG design. As a result of their innovation, they achieved a 2.5-fold power enhancement in the TENG [72]. PTFE, ranking higher than PDMS in electronic attraction, offers significant potential for TENG development. As illustrated in Figure 2e, Wang’s team developed an S-TENG using a porous PTFE film, crafted with deionized water as a template. At optimal porosity (50% deionized water volume), the output voltage peaked at 5.1 V. This porous PTFE S-TENG delivered a voltage 1.8 times greater than its solid counterpart under the same conditions. Notably, when manually pressed, it generated 1.1 V, and inside a latex glove, this surged to 6.9 V, immediately lighting up five green LEDs without energy storage [73]. Peng and his team introduced a high-performance FPS-TENG crafted from a robust fluorinated polymer sponge, demonstrating unmatched electrical stability across various humidity levels. Owing to the sponge’s superior hydrophobic nature, the FPS-TENG resists moisture-related setbacks, ensuring consistent performance even after extensive wear (Figure 2f). At a relative humidity of 40%, this innovative FPS-TENG achieves an electrical surge of 181 V, 2.26 μA, and 52.5 μC m−2, marking a staggering 364% leap over traditional PPS and PPF-based TENGs [74]. In an innovative stride, Kim and his team introduced the Tire-TENG, a groundbreaking TENG integrated into a smart tire using acoustic foam (AF). Beyond its sound-damping capabilities, the AF acts as a potent energy collector, delivering both impressive energy output and noise mitigation. As depicted in Figure 2g, Tire-TENG’s prowess was substantiated through rigorous lab and Flat-Trac evaluations, proving its efficacy in powering smart sensor systems within the tire. With its dual capabilities of versatile energy capture and formidable environmental resistance, the Tire-TENG emerges as an optimal choice for continuously energizing smart tire sensor systems [75]. Nawaz and team pioneered a technique to harness polystyrene (PS) from discarded packaging, subsequently crafting a porous TENG showcased in Figure 2h. The device’s outstanding triboelectric charge density (~90 μC m−2) is a testament to the unique porosity introduced in the WPS film. Notably, the WPS-TENG showcased enduring stability, withstanding over 20,000 contact/separation cycles and a test period of 180 days. Leveraging this innovation, they also introduced a self-sustained speed sensor for road vehicles, underscoring the practical applications of the WPS-TENG [76].
From an overarching standpoint, foam processing offers a distinct advantage in meticulously engineering the size, distribution, and morphology of pores. Dielectrics grounded in foam technology stand at the forefront as prime contenders for seamless TENG architectures, with expansive void units showcasing dynamic, spring-like attributes, perfectly aligned for the TENG’s contact separation dynamics. Nonetheless, the presence of these pronounced voids inherently creates pronounced discontinuities in the polymer matrix, which could compromise its dielectric integrity. The realm also grapples with potential pitfalls such as fluctuating energy outputs, escalated manufacturing expenditures, diminished longevity due to consistent compressions, and variances in specimen parameters, potentially jeopardizing the consistency and replicability of performance outcomes.

2.1.2. Aerogel-Based Dielectrics

Aerogels, with their ultralightweight, highly porous nature, boast a sophisticated three-dimensional nanonetworked architecture. Their intricate synthesis includes gelation, solvent extraction, and gas phase transitions [77]. Renowned for their minimal densities, vast surface areas, and superior thermal insulation, aerogels find applications in advanced insulation, sound attenuation, and as catalyst substrates. The production techniques for aerogels are continually optimized to suit diverse industry needs. Material chemistry and environmental conditions influence their unique pore structure, ranging from nanometers to microns, ensuring uniformity. This structure amplifies nanoconglomerations and surface-to-volume ratios. Being feather-light, aerogels are ideal for weight-sensitive applications. As dielectrics, they offer immense lightweight advantages and charge storage capacities, marking them as a preferred choice in innovative TENG designs.
In 2018, Zheng’s team innovated a TENG (A-NGs) harnessing the capabilities of a cutting-edge polymer porous aerogel film. Capitalizing on an amplified contact area and innate electrostatic induction of the porous matrix, the A-NGs eclipsed the performance of traditional dense-film nanogenerators, D-NGs (Figure 3a). Employing a fusion of porous chitosan with a highly porous polyimide aerogel (at 92% porosity), this A-NG showcased a remarkable voltage of 60.6 V and a current of 7.7 µA, equating to a power density of 2.33 W m−2 [78]. Zhang and associates unveiled an innovative technique for engineering cellulose-based aerogel TENGs. Through a strategic dissolution–regeneration protocol, they achieved a cellulose aerogel endowed with a sophisticated 3D open-pore network, remarkable flexibility, pronounced porosity, and a significant surface area of 221.3 m2 g−1 (Figure 3b). TENGs harnessed from this cellulose II aerogel demonstrated superior mechanical responsiveness and elevated electrical performance [79].
Figure 3. (a) A-NG: Porous aerogel film-based TENG with schematic and photo. Also, performance and stability of P-CTS/P-PI A-NG. (b) Cellulose II structure: Fabrication, characterization, and performance under varying force and frequency. (c) PBOA/Al TENGs: Fabrication, SEM of compressed PBOA films, and schematic. Shows TENG performance under different temperatures. (d) PA nanofiber mats and PI aerogel film TENG: Illustrates TENG setup and material morphology. (e) C-NGD: Details of preparation, SEM, and TEM images of nanosheets. (f) MXene/CMC aerogel: Fabrication and evaluation of voltage/power density. Output stability of MXene/CMC2.5 aerogel-based TENG: Stability assessment at 2 Hz. Voc curves of MXene/CMC aerogel TENG: Comparison before and after 5 months at room temperature.
As depicted in Figure 3c, Qian and team utilized polybenzobisoxazole aerogel (PBOAs) for the TENG as a resilient negative tribomaterial, withstanding up to 350 °C. Leveraging its pronounced porosity and superior specific surface area, the TENG recorded a maximum of 40 V open-circuit voltage, 2.9 mA m−2 current density, and 72 μC m−2 charge density. Remarkably, even at 350 °C, the TENG maintained a Jsc of 1.2 mA m−2 and a charge density of 32 μC m−2, underscoring its potential in high-temperature applications [80]. Leveraging porous polyamide (PA) nanofiber pads and polyimide aerogel films, Mi’s team unveiled an advanced TENG design (Figure 3d). Their study underscored the pivotal role of multilayered porous tribomaterials in optimizing TENG output. As PA layering progressed from single to sextuple, a marked surge in triboelectric efficiency was observed [81]. Simultaneously, multifunctional carbon aerogels have been integrated into TENG fabrication. Using a biomass-mediated strategy, Long’s team synthesized nitrogen-doped carbon aerogels (C-NGD) from a cost-effective, abundant blend of calcined glucose, dicyanamide nanoplatelets (C-GD), and cellulose nanofibers (CNFs). The synergy between C-GD and CNFs crafted a robust wavy lamellar architecture (Figure 3e). This carbon aerogel is not only apt for wearable piezoresistive sensors tracking bodily motions and biosignals but also showcases promise in supercapacitors and triboelectric nanogenerators [82]. As shown in Figure 3f, Cheng et al. developed an MXene-Ti3AlCx/carboxymethyl cellulose (MXene/CMC) aerogel for both mechanical energy harvesting and shielding against electromagnetic radiation, demonstrating a dual functionality [62].
Luo et al. introduced a biocompatible porous TENG utilizing bacterial cellulose (BC) and hydroxyethyl cellulose (HEC) aerogels. The plentiful hydroxyl groups in BC and HEC molecules enable the formation of a three-dimensional network structure through hydrogen bonding, eliminating the need for additional cross-linking agents (Figure 4a). Through fine-tuning of the aerogel’s surface potential and pore structure, the output performance of the BC/HEC aerogel-based single-electrode TENG experiences a substantial boost. It outperforms pure BC aerogels with matching HEC content (80 wt%) by over 30 times and non-porous samples by over 4 times. This method delivers a biocompatible, cost-effective, and highly porous cellulose-based TENG with greatly enhanced output capabilities [83]. Qian et al. achieved a biocompatible cellulose-based TENG through advanced full printing. This AP-TENG, distinguished by a unique 3D micro/nanopatterned design, optimizes structural efficiency, increasing contact area, surface roughness, and mechanical resilience. This leads to heightened triboelectric response compared to traditional molded TENGs (Figure 4b). The layered micro/nano 3D structure of the AP-TENG delivers superior voltage output. This breakthrough provides a novel approach for crafting high-performance 3D TENGs with wide applicability in multifunctional electronics [84].
Figure 4. (a) BC/HEC aerogel preparation. Current, voltage, and charge of 20/80 aerogel TENG under 1 Hz frequency and varying external forces. Electrical signal on mobile screen upon tapping the smart panel. (b) Schematic AP-TENG fabrication. Photos (i) and corresponding optical microscope images (ii) of CNF triboelectric layer patterns at different tilt angles, with cross-sectional SEM image (iii) of printed aerogel structure. (c) Diverse applications of multifunctional AP-TENG. FRTENG creation steps. Flame resistance and self-extinguishing properties. (d) PIA film creation and liquid analyzer’s structural design. Mechanisms behind trace liquid analysis.
As aerogel synthesis advances, there is a renewed focus on improving their triboelectric performance. Common materials like polyimide (PI), polybenzimidazole, polyurethane, polyvinylidene fluoride (PVDF), polyethylene terephthalate (PET), and polyether ether ketone (PEEK) have shown significant progress in this area. Ahmed et al. developed a flame-retardant, self-extinguishing triboelectric nanogenerator (FRTENG) with controllable chemical and structural properties. This FRTENG, also functioning as a motion sensor and generator, utilizes resorcinol–formaldehyde aerogel’s excellent thermal properties. By incorporating polyacrylonitrile nanofibers and graphene oxide nanosheets, they significantly enhanced its electrical, mechanical, and triboelectric performance. This advancement enables the FRTENG to generate up to 80 V potential differences and achieve current densities of 25 µA/m2 (Figure 4c). Additionally, the FRTENG exhibits flame-retardant and self-extinguishing traits, marking a breakthrough in lifesaving wearable technology [85]. Zhou’s team created a highly porous 220 μm thick polyimide aerogel (PIA) film with an impressive 98.01% porosity. Using this material, they developed a liquid analyzer embedding a TENG structure (Figure 4d). This analyzer swiftly responds to tiny liquid volumes as small as 7 μL, owing to the PIA film’s mesoporous and highly porous yet robust nature [86]. By manipulating drying conditions and synthesis parameters, aerogel structures with diverse pore sizes and distributions can be attained. While aerogel-based dielectrics offer benefits like extreme light weight, superior insulation, and highly adjustable surface-area-to-volume ratios, they are hindered by brittleness and the challenge of thin-film fabrication. These factors can negatively impact the output of aerogel-based TENGs.

2.1.3. Fiber Dielectric

Fiber dielectrics, based on fibrous structures, are typically composed of polymeric materials. This imparts excellent flexibility and a large specific surface area. The pore size, crucial for charge storage, varies based on factors like fiber diameter and fabrication methods. Processing technologies include electrospinning, wet spinning, gel spinning, melt spinning, dry spinning, and centrifugal spinning [27][39][87]. Research-team-controlled factors like solution pumping rate and needle type regulate fiber size and distribution, allowing precise control over pore size and porosity in the prepared fiber pads. As shown in Figure 5a, Rastegardoost et al. developed a high-performance TENG using porous PVDF pads with enhanced dielectric properties and a unique dipole arrangement. Different single-layer electrospinning felts were produced by adjusting process parameters. The enhancement was even more significant in intelligent multilayer configurations, achieved by stacking electrospinning porous pads with oriented dipoles. The dielectric constant surpassed that of a single-layer electrospinning pad and matched the non-porous original PVDF film. Output voltages exceeded 130 V, with currents up to 12 μA—markedly superior to the non-porous original PVDF film and single-layer electrospinning pad [88]. Rahman et al. incorporated cobalt-based nano porous carbon (Co-NPC) derived from metal–organic frameworks into PVDF composite nanofibers (NFs) to enhance TENG performance in mechanical energy harvesting. Co-NPC, with large surface area and exceptional nanoscale porosity, significantly improved the β-phase formation and dielectric constant of PVDF composite NFs (Figure 5b). This led to a 4-fold increase in surface potential and a 9.5-fold increase in charge capture capability, resulting in a substantial boost in TENG efficiency [89]. Jiang et al. developed a self-powered, UV-protected, self-cleaning, and antibacterial triboelectric nanogenerator (TENG) based on Ag nanowires/TPU nanofibers and a TiO2@PAN network (Figure 5c). The TiO2 nanoparticles, evenly dispersed in PAN nanofibers, broaden solar absorption and enhance photocatalysis. With a micro–nanoporous structure, this TENG acts as a self-powered pedometer for monitoring human movement, promising diverse applications in human–machine interfaces [90]. Zhong et al. innovatively used asymmetrical dielectric manipulation, employing electrospinning to create a dual-layer PCL nanofiber felt. This material, distinguished by its large surface area, robust hydrophobicity, and high dielectric constant, functioned as an exceptional positive triboelectric material (Figure 5d). The BPF-TENG exhibited a 740% increase in transferred charge compared to PCL gel film-based devices, achieving 210 nC at 1 Hz. Remarkably, it could sustain long-term operation through human motion at 80% humidity [91]. In another study, as shown in Figure 5e, Li et al. achieved a milestone in material integration by developing a microfiber membrane that seamlessly combines hydrophobic elastic fibers with electrodes. Through synchronized electrospinning of styrene–isoprene–styrene (SIS) block copolymers and fluorinated SiO2 nanoparticles, they achieved a membrane with exceptional superelasticity, permeability, and superhydrophobicity. By integrating various conductors, including sputtered gold (Au) layers, they created a spectrum of elastic conductors and triboelectric active materials. These demonstrated optional benefits in terms of mechanical stability, electrical durability, triboelectric output, and permeability. This breakthrough gave rise to the development of self-powered sensors that are not only breathable but also capable of material identification and hand gesture monitoring [92].
Figure 5. (a) Compares fabrication processes, SEM morphologies, and WCA of electrospinning samples, optimizing parameters. (b) Illustrates Co-NPC synthesis and PVDF composite NFs. (c) Details of structure and working mechanism, showing leg actions and voltage signals during walking, and activities monitoring for squatting. (d) Presents BPF-TENG structure and biomechanical energy harvesting. (e) Highlights SPSM fabrication and STENG arrays as self-powered sensors. (f) Covers materials, structure, wet spinning, and smart textile functionality, with voltage signals for human motions.
In recent years, fiber dielectrics have gained prominence in the study of porous materials. Numerous reviews have specifically explored TENGs based on fibers and textiles, emphasizing the chosen fiber-processing techniques and material selections [87][93][94][95][96][97]. The TENGs incorporating fiber dielectrics have been categorized and studied. For instance, Kwak et al. systematically analyzed the organization of fibers within fibrous matrices. Their examination further elucidated the performance attributes of fiber-based configurations, encompassing wound, coaxial, folded, and elastic fiber architectures [94]. Hao et al. introduced a highly stretchable, conductive composite fiber formed by co-polymerizing surface-modified MXene (P-MXene) ink with wet-spun MXene/TPU fibers (MMP). MMP combines TPU’s mechanical flexibility with MXene’s conductivity, resulting in fibers with high conductivity (4.32 S cm−1), extensive strain tolerance (~675%), and strong mechanical properties (~3.76 MPa) (Figure 5f). These fibers, when woven with commercial ones, create fiber-based TENGs that convert mechanical energy to electricity, generating 20.1 V open-circuit voltage and 0.16 mW m−2 power density [98].
In addition to investigating two-dimensional (2D) and three-dimensional (3D) fiber structures, such as knitting, weaving, and braiding, this study also discusses and compares various techniques aimed at enhancing the triboelectric electrification of fibers. These techniques include coating, spinning, electroplating, and printing, as illustrated in Figure 6 [99]. For instance, Chen et al. have introduced an eco-friendly superhydrophobic fabric-based TENG (SF-TENG) composed of superhydrophobic conductive bacterial cellulose fibers (SEBC fibers) woven in a core–shell structure. SEBC fibers with this biofabricated core–shell structure exhibit outstanding conductivity, mechanical strength, biodegradability, and long-lasting superhydrophobicity (Figure 6a). This configuration achieves a maximum open-circuit voltage of 266.0 V, a short-circuit current of 5.9 μA, and an output power of 489.7 μW. SF-TENG successfully powers devices like stopwatches and calculators, offering a novel biomanufacturing strategy for core–shell superhydrophobic conductive fibers [100].
Figure 6. (a) Fabrication of SEBC fiber and SF-TENG. Overview of the intelligent clothing and a magnified image of the SF-TENG component. Performance results of the intelligent clothing and sports and health monitoring system. (b) Fabrication and structure of the TENG. Details of the TENG fabrication process and its structure. Real-time monitoring of human body motion. Output voltage, short-circuit current, and power density of the TENG annealed at 120 °C. (c) Preparation of PVDF fibers via NFES system. Description of the PVDF fiber preparation process using the NFES system driven by a TENG. Workflow for testing the piezoelectric performance of single PVDF fibers, including forward and reversed connections for measuring open-circuit voltage and short-circuit current.
Despite the introduction of various methods for producing nanofibers, including techniques like self-assembly and phase separation, electrospinning remains the dominant approach in this research field. Its widespread use is attributed to its ability to control fiber diameter and microstructure, cost effectiveness, and the availability of a diverse range of materials [101][102]. Furthermore, over 55% of these studies opt for fluorinated polymers as the material for nanofiber production. These polymers, composed of fluorine and hydrogen atoms, exhibit dipole moments in different configurations, resulting in superior triboelectric electrification performance. Ge et al. provided an overview of the factors influencing the preparation and formation of electrospinning fibers, as well as their advantages as triboelectric electrodes for TENGs [103]. Recently, Lee et al. fabricated a highly flexible TENG by directly electrospinning polyvinylidene fluoride–trifluoroethylene (PVDF-TrFE) nanofiber membranes onto a multiwalled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS)/silver nanowire (Ag NW) composite electrode (Figure 6b). The electrospun PVDF-TrFE nanofiber membrane, with its unique crystal structure, enhances the TENG’s output performance and ensures stable electricity generation under various conditions [104]. Guo et al. utilized a TENG-powered near-field electrospinning (NFES) system to craft PVDF fibers with precision. They achieved controlled deposition on a rotating drum electrode by short-distance (2 mm) continuous injection of PVDF precursor solution from a moving needle, eliminating the need for extra polarization and stretching. Key parameters like PVDF concentration, needle diameter, TENG pulse DC voltage, flow rate, and drum speed were systematically optimized for the desired β-phase fraction. At a 0.5 Hz frequency, the PVDF single fiber device yielded 6.1 mV voltage and a maximum power of 3.52 pW with an optimal load resistance of 10.6 MΩ (Figure 6c). This cost-effective TENG-driven NFES approach offers highly controllable PVDF fibers suitable for precision micro/nanodevices and wearable components [105].
Li et al. provided an extensive review of recent progress in electrospinning nanofibers used for triboelectric-based energy generation and functional conductors. They covered topics such as working mechanisms, fabrication strategies, geometric control, functional integration, and performance enhancements. Additionally, the review emphasized the advantages of nanofiber-based TENG devices across different application areas, highlighting their potential for harvesting high-entropy energy from the environment [39]. In summary, fiber dielectrics offer advantages such as strain compatibility, breathable structures, and versatile control over dielectric thickness—a key TENG parameter—making them potential candidates for diverse applications. However, they have limitations including limited mechanical strength, reduced structural integrity under cyclic loading, significant interface challenges, sensitivity to environmental conditions, and a need for improved chemical stability.

2.2. Porous Electrode Materials

Porous electrode materials are pivotal in TENG for efficient energy collection and conversion. Critical considerations for these materials include conductivity, surface area, pore architecture, and mechanical and chemical robustness [106][107]. The evolution to an all-porous TENG design offers superior breathability, flexibility, and adaptability, positioning it ideally for advancements in flexible electronics and wearable tech. This adaptability ensures consistent performance across diverse environments and dynamic conditions [108]. Li’s team adeptly engineered a PEGDA/Lap nanocomposite hydrogel conductor from biocompatible polyethylene glycol diacrylate and lithium laponite, leading to the creation of a pioneering biodegradable single-electrode triboelectric nanogenerator (BS-TENG) (Figure 7a) [109]. Fabricating high-conductivity porous electrodes presents a significant challenge due to the inherent tension between conductivity and porosity. Elevated conductivity often diminishes porosity, given the limited surface area of highly conductive materials. This demands a nuanced balance between the two. Importantly, such enhancements can pose a risk to mechanical resilience, potentially compromising electrode longevity. In TENG design, the highlighted challenges can precipitate notable energy losses, compromising output efficiency. Beyond the electrode’s conductivity and porosity, a pivotal concern is achieving robust adhesion between the electrode and dielectric for optimal charge transfer. An uptick in pore density and size can diminish this electrode–dielectric contact area, undermining adherence. Such a decline can detrimentally influence the TENG’s long-term performance. Consequently, in the electrode fabrication process, it is essential to judiciously balance conductivity, porosity, and effective contact interfacing.
Figure 7. (a) Preparation schematic of BS-TENGs using PEGDA/Lap hydrogel for physiological signal monitoring. (b) Synthesis outline of PAM/HPMC/MXene hydrogel with a confusion matrix for 1D-CNN prediction. (c) Visualization of ultrasound-activated electrical stimulation of vagus nerves via implantable HENG, with corresponding ultrasound response. (d) Hydrogel structural diagram with repeatable voltage signals highlighting handwriting detail discernment.
Beyond electrode conductivity and porosity, commercialization of porous electrodes grapples with two salient barriers: prohibitive production costs and diminished durability. This underscores the imperative for intensified research focus. Fabricating high-conductivity porous electrodes involves intricate methodologies, necessitating precise control over processes and parameters. While multiple methods exist, balancing effective electrode–dielectric contact with optimal conductivity and porosity remains a cardinal concern. Key conductive materials feature low-dimensional nanostructures, including nanowires, nanoparticles, and nanosheets, supplemented by conductive polymers like PANI and PEDOT. An alternate tactic entails the deposition of conductive coatings on insulating substrates, utilizing materials like carbonaceous fillers, liquid metals, and electrolytes. Such components are foundational in crafting porous electrodes. Another pivotal avenue is the exploration of porous electrode fabrication techniques. Core methodologies include coating, electrospinning, metal plating, and printing. Utilizing these advanced techniques, researchers have synthesized diverse porous electrodes, such as aerogels, fibrous media, and foams, exhibiting properties like high transparency, stretchability, self-healing, and freeze resistance. Such advancements fortify the trajectory of porous electrodes, underscoring their potential for broad applications. The pronounced wettability of hydrogels markedly facilitates ionic conductivity, mitigating carrier constraints. In TENG designs, a common approach integrates moisture-retentive hydrogels within highly extensible elastomers. Utilizing sol–gel processes, factors such as pressure, temperature, and cross-linking density can be finely tuned, optimizing pore geometry in hydrogels and thus enhancing electrode efficacy. This innovation heralds a significant leap in TENG technology [110].
Li and colleagues devised a composite hydrogel comprising polyacrylamide, hydroxypropyl methylcellulose, and MXene (Ti3C2Tx) nanosheets. Through hydrogen bonding, the hydrogel establishes a robust double-helix structure, exhibiting attributes like superior strength, tensile performance, conductivity, and strain sensitivity (Figure 7b). Capitalizing on these properties, they constructed a flexible multifunctional TENG that can harness biomechanical energy, achieving a conversion of 183 V with a peak power density of 78.3 mW/m2 [111]. Panwar et al. synthesized a high-performance CMCh-CMC-PDA hydrogel by integrating carboxymethyl chitosan (CMCh) and CMC-dialdehyde-polydopamine (CMC-D-PDA) through both physical and covalent interactions. The pre-formation of CMC-D-PDA involved two key steps: oxidation of CMC to introduce aldehyde groups and subsequent dopamine polymerization. Similarly, actions on CMCh formed reversible dynamic imine bonds, yielding a hydrogel with outstanding properties [112]. Uniform dispersion of carbon-based materials in a hydrogel is a known challenge. Yet, Chen et al. ingeniously addressed this by integrating graphene dispersion with the hydrogel precursor, as depicted in Figure 7c. Introducing 5 wt% graphene into the PAM hydrogel created a conductive three-dimensional network, facilitating charge transfer and current collection [113]. While hydrogels offer excellent flexibility and stretchability for wearable electronics, their limited mechanical strength poses challenges for long-term stability. To address this, researchers have focused on developing self-healing hydrogels and resultant H-TENGs. Zhang et al. introduced an ionic hydrogel comprising polypropylene amine (PAM), tannic acid (TA), sodium alginate (SA), and MXene (PTSM). The hydrogel, fortified by numerous weak hydrogen bonds, demonstrated remarkable stretchability (strain > 4600%), adhesion, and self-repair capabilities. Encasing PTSM hydrogel with Ecoflex yielded the PTSM TENG, achieving an output power density of 54.24 mW/m2 (Figure 7d). This technology was integrated into a glove-based human–machine interaction (HMI) system [114]. Due to their outstanding strain compatibility, hydrogels are considered a potential choice for lateral sliding TENG applications. However, they require encapsulation, which to some extent limits their widespread use.
In addition to hydrogels, research has also been conducted on other porous electrode materials. Li et al. innovated a fully stretchable triboelectric nanogenerator (FSTENG) comprising electrospinning electrodes and a porous PDMS triboelectric layer with nickel foam structure (Figure 8a). The FSTENG achieves an impressive 92 V output voltage, surpassing traditional TENGs based on flat PDMS films by an order of magnitude [115]. Porous foam electrodes have been shown to enhance TENG performance. For example, Cui et al. developed a dual-mode TENG with a spongy electrode-brush structure for mechanical energy harvesting and self-powered trajectory tracking. The conductive sponge (CS) electrode, created through chemical and electroplating processes, features a flexible, elastic, porous, and large-surface-area network structure (Figure 8b). This CS-based TENG exhibits potential for self-powered sensing, excelling in both contact separation and sliding modes with excellent electrical performance and environmental adaptability. A 4 × 4 CS unit-based trajectory tracking matrix demonstrated outstanding real-time monitoring and comprehensive trajectory recording. This work carries substantial implications for the practical implementation of TENGs in future intelligent systems [116]. As shown in Figure 8c, Liu et al. have developed a TENG using conductive elastic sponges for efficient collection of random mechanical energy and ammonia sensing. The TENG is based on conductive sponge electrodes with large surface area, flexibility, and elasticity. It effectively harvests mechanical energy from random motion and vibration and detects ammonia. The TENG showed good sensitivity and stability in ammonia-sensing experiments and has potential for environmental monitoring and gas-sensing applications. Conductive elastic sponges and TENGs have potential to develop into a convenient self-powered source for collecting random mechanical energy and rapid response self-powered NH3 sensors. This work emphasizes the effectiveness of TENGs based on conductive elastic sponges in energy-harvesting and sensing applications [117].
Figure 8. (a) Illustration of FSTENG fabrication process. Digital photo of resulting pPDMS film. (b) Electrical characterization of CS-based TENG in vertical contact separation mode. (c) Illustration and SEM images of conductive elastic sponge preparation using dilute chemical polymerization. Schematic of ES-TENG. (d) Structure and operation of PCP-TENG. Electrical output under 180 N vertical force and 3 Hz frequency. (e) Fabrication process and photo of LMS. (f) Illustration of CCA fabrication. (g) Sponge-based TENG fabrication and corresponding output parameters.

This entry is adapted from the peer-reviewed paper 10.3390/polym15224383

References

  1. Han, Y.; Wang, W.; Zou, J.; Li, Z.; Cao, X.; Xu, S. Self-powered energy conversion and energy storage system based on triboelectric nanogenerator. Nano Energy 2020, 76, 105008.
  2. Shrestha, K.; Sharma, S.; Pradhan, G.B.; Bhatta, T.; Maharjan, P.; Rana, S.M.S.; Lee, S.; Seonu, S.; Shin, Y.; Park, J.Y. A Siloxene/Ecoflex nanocomposite-based triboelectric nanogenerator with enhanced charge retention by MoS2/LIG for self-powered touchless sensor applications. Adv. Funct. Mater. 2022, 32, 2113005.
  3. Lei, H.; Xiao, J.; Chen, Y.; Jiang, J.; Xu, R.; Wen, Z.; Dong, B.; Sun, X. Bamboo-inspired self-powered triboelectric sensor for touch sensing and sitting posture monitoring. Nano Energy 2022, 91, 106670.
  4. Li, W.; Pei, Y.; Zhang, C.; Kottapalli, A.G.P. Bioinspired designs and biomimetic applications of triboelectric nanogenerators. Nano Energy 2021, 84, 105865.
  5. Liu, Y.; Ping, J.; Ying, Y. Recent progress in 2D-nanomaterial-based triboelectric nanogenerators. Adv. Funct. Mater. 2021, 31, 2009994.
  6. Chang, A.; Uy, C.; Xiao, X.; Chen, J. Self-powered environmental monitoring via a triboelectric nanogenerator. Nano Energy 2022, 98, 107282.
  7. Mi, Y.; Lu, Y.; Wang, X.; Zhao, Z.; Cao, X.; Wang, N. From Triboelectric nanogenerator to uninterrupted power supply system: The key role of electrochemical batteries and supercapacitors. Batteries 2022, 8, 215.
  8. Hanani, Z.; Izanzar, I.; Amjoud, M.; Mezzane, D.; Lahcini, M.; Uršič, H.; Prah, U.; Saadoune, I.; Luk’Yanchuk, I.A.; Kutnjak, Z.; et al. Lead-free nanocomposite piezoelectric nanogenerator film for biomechanical energy harvesting. Nano Energy 2021, 81, 105661.
  9. Yu, D.; Zheng, Z.; Liu, J.; Xiao, H.; Huangfu, G.; Guo, Y. Super flexible and lead-free piezoelectric nanogenerator as a highly sensitive self-powered sensor for human motion monitoring. Nano-Micro Lett. 2021, 13, 117.
  10. Kim, W.-G.; Kim, D.-W.; Tcho, I.-W.; Kim, J.-K.; Kim, M.-S.; Choi, Y.-K. Triboelectric Nanogenerator: Structure, Mechanism, and Applications. ACS Nano 2021, 15, 258–287.
  11. Parandeh, S.; Etemadi, N.; Kharaziha, M.; Chen, G.; Nashalian, A.; Xiao, X.; Chen, J. Advances in Triboelectric Nanogenerators for Self-Powered Regenerative Medicine. Adv. Funct. Mater. 2021, 31, 2105169.
  12. Dong, K.; Peng, X.; Cheng, R.; Wang, Z.L. Smart textile triboelectric nanogenerators: Prospective strategies for improving electricity output performance. Nanoenergy Adv. 2022, 2, 133–164.
  13. Zhou, Y.; Deng, W.; Xu, J.; Chen, J. Engineering materials at the nanoscale for triboelectric nanogenerators. Cell Rep. Phys. Sci. 2020, 1, 100142.
  14. Chen, J.; Wang, Z.L. Reviving vibration energy harvesting and self-powered sensing by a triboelectric nanogenerator. Joule 2017, 1, 480–521.
  15. Liang, S.; Wang, Y.; Liu, Q.; Yuan, T.; Yao, C. The recent progress in cellulose paper-based triboelectric nanogenerators. Adv. Sustain. Syst. 2021, 5, 1904066.
  16. Dong, K.; Wang, Z.L. Self-charging power textiles integrating energy harvesting triboelectric nanogenerators with energy storage batteries/supercapacitors. J. Semicond. 2021, 42, 101601.
  17. Yang, X.; Liu, G.; Guo, Q.; Wen, H.; Huang, R.; Meng, X.; Duan, J.; Tang, Q. Triboelectric sensor array for internet of things based smart traffic monitoring and management system. Nano Energy 2022, 92, 106757.
  18. Zhang, C.; Lin, X.; Zhang, N.; Lu, Y.; Wu, Z.; Liu, G.; Nie, S. Chemically functionalized cellulose nanofibrils-based gear-like triboelectric nanogenerator for energy harvesting and sensing. Nano Energy 2019, 66, 104126.
  19. Jin, L.; Zhang, S.L.; Xu, S.; Guo, H.; Yang, W.; Wang, Z.L. Free-fixed rotational triboelectric nanogenerator for self-powered real-time wheel monitoring. Adv. Mater. Technol. 2021, 6, 2000918.
  20. Lama, J.; Yau, A.; Chen, G.R.; Sivakumar, A.; Zhao, X.; Chen, J. Textile triboelectric nanogenerators for self-powered biomonitoring. J. Mater. Chem. A 2021, 9, 19149–19178.
  21. Xuan, Z.; Wang, Z.L.; Wang, N.; Cao, X. Thermal-driven soft-contact triboelectric nanogenerator for energy harvesting and industrial cooling water monitoring. Small 2023, 19, e2206269.
  22. Wu, H.; Wang, S.; Wang, Z.; Zi, Y. Achieving ultrahigh instantaneous power density of 10 MW/m2 by leveraging the oppo-site-charge-enhanced transistor-like triboelectric nanogenerator (OCT-TENG). Nat. Commun. 2021, 12, 5470.
  23. Shi, X.; Chen, S.; Zhang, H.; Jiang, J.; Ma, Z.; Gong, S. Portable self-charging power system via integration of a flexible paper-based triboelectric nanogenerator and supercapacitor. ACS Sustain. Chem. Eng. 2019, 7, 18657–18666.
  24. Mi, Y.J.; Lu, Y.; Shi, Y.L.; Zhao, Z.Q.; Wang, X.Q.; Meng, J.J.; Cao, X.; Wang, N. Biodegradable polymers in triboelectric nano-generators. Polymers 2023, 15, 15010222.
  25. Tang, Y.; Zheng, Q.; Chen, B.; Ma, Z.; Gong, S. A new class of flexible nanogenerators consisting of porous aerogel films driven by mechanoradicals. Nano Energy 2017, 38, 401–411.
  26. Yang, J.C.; Mun, J.; Kwon, S.Y.; Park, S.; Bao, Z.; Park, S. Electronic skin: Recent progress and future prospects for skin-attachable devices for health monitoring-robotics, and prosthetics. Adv. Mater. 2019, 31, e1904765.
  27. Chen, A.; Zhang, C.; Zhu, G.; Wang, Z.L. Polymer materials for high-performance triboelectric nanogenerators. Adv. Sci. 2020, 7, 2000186.
  28. Jayababu, N.; Kim, D. ZnO nanorods@conductive carbon black nanocomposite based flexible integrated system for energy conversion and storage through triboelectric nanogenerator and supercapacitor. Nano Energy 2021, 82, 105726.
  29. Rastegardoost, M.M.; Tafreshi, O.A.; Saadatnia, Z.; Ghaffari-Mosanenzadeh, S.; Park, C.B.; Naguib, H.E. Recent advances on porous materials and structures for high-performance triboelectric nanogenerators. Nano Energy 2023, 111, 108365.
  30. Chen, H.; Huang, J.; Liu, J.; Gu, J.; Zhu, J.; Huang, B.; Bai, J.; Guo, J.; Yang, X.; Guan, L. High toughness multifunctional organic hydrogels for flexible strain and temperature sensor. J. Mater. Chem. A 2021, 9, 23243–23255.
  31. Guo, X.; Yang, F.; Sun, X.; Bai, Y.; Liu, G.; Liu, W.; Wang, R.; He, X. Anti-freezing self-adhesive self-healing degradable touch panel with ultra-stretchable performance based on transparent triboelectric nanogenerators. Adv. Funct. Mater. 2022, 32, 2201230.
  32. Xu, Z.; Zhou, F.; Yan, H.; Gao, G.; Li, H.; Li, R.; Chen, T. Anti-freezing organohydrogel triboelectric nanogenerator toward highly efficient and flexible human-machine interaction at −30 °C. Nano Energy 2021, 90, 106614.
  33. Feng, J.; Su, B.L.; Xia, H.; Zhao, S.; Gao, C.; Wang, L.; Ogbeide, O.; Feng, J.; Hasan, T. Printed aerogels: Chemistry, processing, and applications. Chem. Soc. Rev. 2021, 50, 3842–3888.
  34. Chen, Y.; Zhang, L.; Yang, Y.; Pang, B.; Xu, W.; Duan, G.; Jiang, S.; Zhang, K. Recent progress on nanocellulose aero-gels-preparation, modification, composite fabrication, applications. Adv. Mater. 2021, 33, e2005569.
  35. Wang, X.; Liang, L.; Lv, H.; Zhang, Y.; Chen, G. Elastic aerogel thermoelectric generator with vertical temperature-difference architecture and compression-induced power enhancement. Nano Energy 2021, 90, 106577.
  36. Wang, L.; Fu, X.; He, J.; Shi, X.; Chen, T.; Chen, P.; Wang, B.; Peng, H. Application challenges in fiber and textile electronics. Adv. Mater. 2020, 32, e1901971.
  37. Jang, Y.; Kim, S.M.; Spinks, G.M.; Kim, S.J. Carbon nanotube yarn for fiber-shaped electrical sensors, actuators, and energy storage for smart systems. Adv. Mater. 2020, 32, e1902670.
  38. Tong, Y.; Feng, Z.; Kim, J.; Robertson, J.L.; Jia, X.; Johnson, B.N. 3D printed stretchable triboelectric nanogenerator fibers and devices. Nano Energy 2020, 75, 104973.
  39. Li, Y.; Xiao, S.; Luo, Y.; Tian, S.; Tang, J.; Zhang, X.; Xiong, J. Advances in electrospun nanofibers for triboelectric nanogenerators. Nano Energy 2022, 104, 107884.
  40. Liu, S.; Yuan, F.; Sang, M.; Zhou, J.; Zhang, J.; Wang, S.; Li, J.; Xuan, S.; Gong, X. Functional sponge-based triboelectric nan-ogenerators with energy harvesting, oil–water separating and multi-mode sensing performance. J. Mater. Chem. A 2021, 9, 6913–6923.
  41. Zhang, C.; Chen, H.; Ding, X.; Lorestani, F.; Huang, C.; Zhang, B.; Zheng, B.; Wang, J.; Cheng, H.; Xu, Y. Human motion-driven self-powered stretchable sensing platform based on laser-induced graphene foams. Appl. Phys. Rev. 2022, 9, 011413.
  42. Zhu, D.; Handschuh-Wang, S.; Zhou, X. Recent progress in fabrication and application of polydimethylsiloxane sponges. J. Mater. Chem. A 2017, 5, 16467–16497.
  43. Tan, X.Q.; Wang, S.T.; You, Z.Y.; Zheng, J.M.; Liu, Y. High Performance Porous Triboelectric Nanogenerator Based on Silk Fibroin@MXene Composite Aerogel and PDMS Sponge. ACS Materials Lett. 2023, 5, 1929–1937.
  44. Sun, S.; Liu, Z.-J.; Zheng, J.-Q.; Cheng, Q.-K.; Tan, Y.-L.; Huang, S.-L.; Zhang, L.; Wang, Y.-M.; Zhou, H.-M. A Directional Chitosan Sound Sensor Based on Piezoelectric–Triboelectric Sensing. Nano Energy 2023, 12, 577–582.
  45. Huang, J.Y.; Hao, Y.; Zhao, M.; Li, W.; Huang, F.L.; Wei, Q.F. All-fiber-structured triboelectric nanogenerator via one-pot electrospinning for self-powered wearable sensors. ACS Appl. Mater. Interfaces. 2021, 13, 24774–24784.
  46. Li, Y.; Yao, M.Z.; Luo, Y.-D.; Li, J.; Wang, Z.-L.; Liang, C.; Qin, C.-R.; Huang, C.-X.; Yao, S.-Q. Polydopamine-Reinforced Hemicellulose-Based Multifunctional Flexible Hydrogels for Human Movement Sensing and Self-Powered Transdermal Drug Delivery. ACS Appl. Mater. Interfaces 2023, 15, 5883–5896.
  47. Feng, P.Y.; Xia, Z.K.; Sun, B.B.; Jing, X.; Li, X.; Tao, X.M.; Mi, H.Y.; Liu, Y.J. Enhancing the Performance of Fabric-Based Triboelectric Nanogenerators by Structural and Chemical Modification. ACS Appl. Mater. Interfaces 2021, 13, 16916–16927.
  48. Ma, L.; Zhou, M.; Wu, R.; Patil, A.; Gong, H.; Zhu, S.; Wang, T.; Zhang, Y.; Shen, S.; Dong, K.; et al. Continuous and Scalable Manufacture of Hybridized Nano-Micro Triboelectric Yarns for Energy Harvesting and Signal Sensing. ACS Nano 2020, 14, 4716–4726.
  49. Korkmaz, S.; Kariper, İ.A. Aerogel based nanogenerators: Production methods, characterizations and applications. Int. J. Energy Res. 2020, 44, 11088–11110.
  50. Shao, Y.; Luo, C.; Deng, B.W.; Yin, B.; Yang, M.B. Flexible porous silicone rubber-nanofiber nanocomposites generated by supercritical carbon dioxide foaming for harvesting mechanical energy. Nano Energy 2020, 67, 104290.
  51. Xiong, J.; Cui, P.; Chen, X.; Wang, J.; Parida, K.; Lin, M.F.; Lee, P.S. Skin-touch-actuated textile-based triboelectric nanogenerator with black phosphorus for durable biomechanical energy harvesting. Nat. Commun. 2018, 9, 4280.
  52. Gupta, S.; Dey, M.; Matzke, C.; Ellis, G.; Javaid, S.; Hall, K.; Ji, Y.; Payne, S. Synthesis and characterization of novel foams by pyrolysis of lignin. TAPPI J. 2019, 18, 45–56.
  53. Jiang, W.; Li, H.; Liu, Z.; Li, Z.; Tian, J.; Shi, B.; Zou, Y.; Ouyang, H.; Zhao, C.; Zhao, L.; et al. Fully bioabsorbable natural materials based triboelectric nanogenerators. Adv. Mater. 2018, 30, e1801895.
  54. Biutty, M.N.; Koo, J.M.; Zakia, M.; Handayani, P.L.; Choi, U.H.; Yoo, S.I. Dielectric control of porous polydimethylsiloxane elastomers with Au nanoparticles for enhancing the output performance of triboelectric nanogenerators. RSC Adv. 2020, 10, 21309–21317.
  55. Chun, J.; Kim, J.W.; Jung, W.S.; Kang, C.Y.; Kim, S.W.; Wang, Z.L.; Baik, J.M. Mesoporous pores impregnated with Au nano-particles as effective dielectrics for enhancing triboelectric nanogenerator performance in harsh environments. Energy Environ. Sci. 2015, 8, 3006–3012.
  56. Sun, J.; Choi, H.; Cha, S.; Ahn, D.; Choi, M.; Park, S.; Cho, Y.; Lee, J.; Park, T.; Park, J.J. Highly enhanced triboelectric per-formance from increased dielectric constant induced by ionic and interfacial polarization for chitosan based multi-modal sensing system. Adv. Funct. Mater. 2021, 32, 2109139.
  57. Mannsfeld, S.C.B.; Tee, B.C.-K.; Stoltenberg, R.M.; Chen, C.V.H.-H.; Barman, S.; Muir, B.V.O.; Sokolov, A.N.; Reese, C.; Bao, Z. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nat. Mater. 2010, 9, 859–864.
  58. Sriphan, S.; Pharino, U.; Charoonsuk, T.; Pulphol, P.; Pakawanit, P.; Khamman, O.; Vittayakorn, W.; Vittayakorn, N.; Maluangnont, T. Tailoring charge affinity, dielectric property, and band gap of bacterial cellulose paper by multifunctional Ti2NbO7 nanosheets for improving triboelectric nanogenerator performance. Nano Res. 2022, 16, 3168–3179.
  59. Paria, S.; Si, S.K.; Karan, S.K.; Das, A.K.; Maitra, A.; Bera, R.; Halder, L.; Bera, A.; De, A.; Khatua, B.B. A strategy to develop highly efficient TENGs through the dielectric constant, internal resistance optimization, and surface modification. J. Mater. Chem. A 2019, 7, 3979–3991.
  60. Haider, Z.; Haleem, A.; Ahmad, R.U.S.; Farooq, U.; Shi, L.; Claver, U.P.; Memon, K.; Fareed, A.; Khan, I.; Mbogba, M.K.; et al. Highly porous polymer cryogel based tribopositive material for high performance triboelectric nanogenerators. Nano Energy 2020, 68, 104294.
  61. Shanbedi, M.; Ardebili, H.; Karim, A. Polymer-based triboelectric nanogenerators: Materials, characterization, and applications. Prog. Polym. Sci. 2023, 144, 101723.
  62. Cheng, Y.; Zhu, W.; Lu, X.; Wang, C. Lightweight and flexible MXene/carboxymethyl cellulose aerogel for electromagnetic shielding, energy harvest and self-powered sensing. Nano Energy 2022, 98, 107229.
  63. Liu, Y.; Zhang, Z.; Yang, X.; Li, F.; Liang, Z.; Yong, Y.; Dai, S.; Li, Z. A stretchable, environmentally stable, and mechanically robust nanocomposite polyurethane organohydrogel with anti-freezing, anti-dehydration, and electromagnetic shielding properties for strain sensors and magnetic actuators. J. Mater. Chem. A 2023, 11, 6603–6614.
  64. Wang, Z.L. Triboelectric nanogenerator (TENG)—Sparking an energy and sensor revolution. Adv. Energy Mater. 2020, 10, 2000137.
  65. Zhu, J.; Zhu, M.; Shi, Q.; Wen, F.; Liu, L.; Dong, B.; Haroun, A.; Yang, Y.; Vachon, P.; Guo, X.; et al. Progress in TENG technology—A journey from energy harvesting to nanoenergy and nanosystem. EcoMat 2020, 2, 12058.
  66. Wu, M.; Gao, Z.; Yao, K.; Hou, S.; Liu, Y.; Li, D.; He, J.; Huang, X.; Song, E.; Yu, J.; et al. Thin, soft, skin-integrated foam-based triboelectric nanogenerators for tactile sensing and energy harvesting. Mater. Today Energy 2021, 20, 100657.
  67. Mao, Y.; Zhao, P.; McConohy, G.; Yang, H.; Tong, Y.; Wang, X. Sponge-like piezoelectric polymer films for scalable and integratable nanogenerators and self-powered electronic systems. Adv. Energy Mater. 2014, 4, 1301624.
  68. Xia, X.; Chen, J.; Guo, H.; Liu, G.; Wei, D.; Xi, Y.; Wang, X.; Hu, C. Embedding variable micro-capacitors in polydimethylsiloxane for enhancing output power of triboelectric nanogenerator. Nano Res. 2016, 10, 320–330.
  69. Lee, K.Y.; Chun, J.; Lee, J.; Kim, K.N.; Kang, N.; Kim, J.; Kim, M.H.; Shin, K.; Gupta, M.K.; Baik, J.M.; et al. Hydrophobic sponge structure-based triboelectric nanogenerator. Adv. Mater. 2014, 26, 5037–5042.
  70. Kou, H.; Wang, H.; Cheng, R.; Liao, Y.; Shi, X.; Luo, J.; Li, D.; Wang, Z.L. Smart pillow based on flexible and breathable tribo-electric nanogenerator arrays for head movement monitoring during sleep. ACS Appl. Mater. Interfaces 2022, 14, 23998–24007.
  71. Kim, D.; Park, S.J.; Jeon, S.B.; Seol, M.L.; Choi, Y.K. A triboelectric sponge fabricated from a cube sugar template by 3D soft lithography for super hydrophobicity and elasticity. Adv. Electron. Mater. 2016, 2, 1500331.
  72. Lu, Y.; Qin, Q.; Meng, J.; Mi, Y.; Wang, X.; Cao, X.; Wang, N. Constructing highly flexible dielectric sponge for enhancing triboelectric performance. Chem. Eng. J. 2023, 468, 143802.
  73. Wang, M.; Zhang, N.; Tang, Y.; Zhang, H.; Ning, C.; Tian, L.; Li, W.; Zhang, J.; Mao, Y.; Liang, E. Single-electrode triboelectric nanogenerators based on sponge-like porous PTFE thin films for mechanical energy harvesting and self-powered electronics. J. Mater. Chem. A 2017, 5, 12252–12257.
  74. Peng, Z.; Song, J.; Gao, Y.; Liu, J.; Lee, C.; Chen, G.; Wang, Z.; Chen, J.; Leung, M.K. A fluorinated polymer sponge with superhydrophobicity for high-performance biomechanical energy harvesting. Nano Energy 2021, 85, 106021.
  75. Kim, W.-G.; Kim, J.-K.; Kim, D.-W.; Tcho, I.-W.; Choi, Y.-K. A triboelectric nanogenerator implemented with an acoustic foam for a self-driven silent tire. Nano Energy 2022, 96, 107090.
  76. Nawaz, S.M.; Saha, M.; Sepay, N.; Mallik, A. Energy-from-waste: A triboelectric nanogenerator fabricated from waste poly-styrene for energy harvesting and self-powered sensor. Nano Energy 2022, 104, 107902.
  77. Zhao, G.; Shi, L.; Yang, G.; Zhuang, X.; Cheng, B. 3D fibrous aerogels from 1D polymer nanofibers for energy and environmental applications. J. Mater. Chem. A 2022, 11, 512–547.
  78. Zheng, Q.; Fang, L.; Guo, H.; Yang, K.; Cai, Z.; Meador, M.A.B.; Gong, S. Highly porous polymer aerogel film-based triboelectric nanogenerators. Adv. Funct. Mater. 2018, 28, 1706365.
  79. Zhang, L.; Liao, Y.; Wang, Y.; Zhang, S.; Yang, W.; Pan, X.; Wang, Z.L. Cellulose II Aerogel-Based Triboelectric Nanogenerator. Adv. Funct. Mater. 2020, 30, 2001763.
  80. Qian, Z.; Li, R.; Guo, J.; Wang, Z.; Li, X.; Li, C.; Zhao, N.; Xu, J. Triboelectric nanogenerators made of poly benzazole aerogels as fire-resistant negative tribo-materials. Nano Energy 2019, 64, 103900.
  81. Mi, H.-Y.; Jing, X.; Meador, M.A.B.; Guo, H.; Turng, L.-S.; Gong, S. Triboelectric nanogenerators made of porous polyamide nanofiber mats and polyimide aerogel film: Output optimization and performance in circuits. ACS Appl. Mater. Interfaces 2018, 10, 30596–30606.
  82. Long, S.; Feng, Y.; He, F.; Zhao, J.; Bai, T.; Lin, H.; Cai, W.; Mao, C.; Chen, Y.; Gan, L.; et al. Biomass-derived, multifunctional and wave-layered carbon aerogels toward wearable pressure sensors, supercapacitors and triboelectric nanogenerators. Nano Energy 2021, 85, 105973.
  83. Luo, C.; Ma, H.; Yu, H.; Zhang, Y.; Shao, Y.; Yin, B.; Ke, K.; Zhou, L.; Zhang, K.; Yang, M.B. Enhanced triboelectric nanogenerator based on a hybrid cellulose aerogel for energy harvesting and self-powered sensing. ACS Sustain. Chem. 2023, 11, 9424–9432.
  84. Qian, C.; Li, L.; Gao, M.; Yang, H.; Cai, Z.; Chen, B.; Xiang, Z.; Zhang, Z.; Song, Y. All-printed 3D hierarchically structured cellulose aerogel based triboelectric nanogenerator for multi-functional sensors. Nano Energy 2019, 63, 103885.
  85. Ahmed, A.; El-Kady, M.F.; Hassan, I.; Negm, A.; Pourrahimi, A.M.; Muni, M.; Selvaganapathy, P.R.; Kaner, R.B. Fire-retardant, self-extinguishing triboelectric nanogenerators. Nano Energy 2019, 59, 336–345.
  86. Zhou, Q.; Wang, W.; He, Y.; Li, Z.; Zhao, R.; Tao, G.; Hu, B.; Hou, C. High-performance polyimide aerogel film-based triboelectric nanogenerator for trace liquid analyzing. ACS Appl. Polym. Mater. 2023, 5, 5466–5473.
  87. Gao, Y.; Tian, E.; Zhang, Y.; Mo, J. Utilizing electrostatic effect in fibrous filters for efficient airborne particles removal: Principles, fabrication, and material properties. Appl. Mater. Today 2022, 26, 101369.
  88. Rastegardoost, M.M.; Tafreshi, O.A.; Saadatnia, Z.; Ghaffari-Mosanenzadeh, S.; Park, C.B.; Naguib, H.E. Porous PVDF mats with significantly enhanced dielectric properties and novel dipole arrangement for high-performance triboelectric nanogenerators. Appl. Mater. Today 2023, 30, 101732.
  89. Rahman, M.T.; Rana, S.S.; Abu Zahed, M.; Lee, S.; Yoon, E.-S.; Park, J.Y. Metal-organic framework-derived nanoporous carbon incorporated nanofibers for high-performance triboelectric nanogenerators and self-powered sensors. Nano Energy 2022, 94, 106921.
  90. Jiang, Y.; Dong, K.; An, J.; Liang, F.; Yi, J.; Peng, X.; Ning, C.; Ye, C.; Wang, Z.L. UV-Protective, Self-cleaning, and antibacterial nanofiber-based triboelectric nanogenerators for self-powered human motion monitoring. ACS Appl. Mater. Interfaces 2021, 13, 11205–11214.
  91. Zhong, J.; Hou, X.; He, J.; Xue, F.; Yang, Y.; Chen, L.; Yu, J.; Mu, J.; Geng, W.; Chou, X. Asymmetric permittivity enhanced bilayer polycaprolactone nanofiber with superior inner interfacial polarization and charge retention for high-output and humidi-ty-resistant triboelectric nanogenerators. Nano Energy 2022, 98, 107289.
  92. Li, Y.; Xiao, S.; Zhang, X.; Jia, P.; Tian, S.; Pan, C.; Zeng, F.; Chen, D.; Chen, Y.; Tang, J.; et al. Silk inspired in-situ interlocked superelastic microfibers for permeable stretchable triboelectric nanogenerator. Nano Energy 2022, 98, 107347.
  93. Hu, C.; Wang, F.; Cui, X.; Zhu, Y. Recent progress in textile-based triboelectric force sensors for wearable electronics. Adv. Compos. Hybrid. Mater. 2023, 6, 1131–1162.
  94. Kwak, S.S.; Yoon, H.J.; Kim, S.W. Textile-based triboelectric nanogenerators for self-powered wearable electronics. Adv. Funct. Mater. 2018, 29, 1804533.
  95. Yang, B.; Xiong, Y.; Ma, K.; Liu, S.; Tao, X. Recent advances in wearable textile-based triboelectric generator systems for energy harvesting from human motion. EcoMat 2020, 2, 12054.
  96. Cui, X.; Wu, H.; Wang, R. Fibrous triboelectric nanogenerators: Fabrication, integration, and application. J. Mater. Chem. A 2022, 10, 15881–15905.
  97. Du, X.; Zhang, K. Recent progress in fibrous high-entropy energy harvesting devices for wearable applications. Nano Energy 2022, 101, 107600.
  98. Hao, Y.; Zhang, Y.; Mensah, A.; Liao, S.; Lv, P.; Wei, Q. Scalable, ultra-high stretchable and conductive fiber triboelectric nanogenerator for biomechanical sensing. Nano Energy 2023, 109, 108291.
  99. Dong, K.; Peng, X.; Wang, Z.L. Fiber/fabric-based piezoelectric and triboelectric nanogenerators for flexible/stretchable and wearable electronics and artificial intelligence. Adv. Mater. 2020, 32, e1902549.
  100. Chen, K.; Li, Y.; Yang, G.; Hu, S.; Shi, Z.; Yang, G. Fabric-based TENG woven with bio-fabricated superhydrophobic bacterial cellulose fiber for energy harvesting and motion detection. Adv. Funct. Mater. 2023, 33, 2304809.
  101. Shi, Q.; Dong, B.; He, T.; Sun, Z.; Zhu, J.; Zhang, Z.; Lee, C. Progress in wearable electronics/photonics—Moving toward the era of artificial intelligence and internet of things. InfoMat 2020, 2, 1131–1162.
  102. Parandeh, S.; Kharaziha, M.; Karimzadeh, F.; Hosseinabadi, F. Triboelectric nanogenerators based on graphene oxide coated nanocomposite fibers for biomedical applications. Nanotechnology 2020, 31, 385402.
  103. Ge, X.; Hu, N.; Yan, F.; Wang, Y. Development and applications of electrospun nanofiber-based triboelectric nanogenerators. Nano Energy 2023, 112, 108444.
  104. Lee, C.; Cho, C.; Oh, J.H. Highly flexible triboelectric nanogenerators with electrospun PVDF-TrFE nanofibers on MWCNTs/PDMS/AgNWs composite electrodes. Compos. Part. B Eng. 2023, 255, 110622.
  105. Guo, Y.; Zhang, H.; Zhong, Y.; Shi, S.; Wang, Z.; Wang, P.; Zhao, Y. Triboelectric nanogenerator-based near-field electrospinning system for optimizing PVDF fibers with high piezoelectric performance. ACS Appl. Mater. Interfaces 2023, 15, 5242–5252.
  106. Yang, W.; Cao, R.; Zhang, X.; Li, H.; Li, C. Air-Permeable and Washable Paper–Based Triboelectric Nanogenerator Based on Highly Flexible and Robust Paper Electrodes. Adv. Mater. Technol. 2018, 3, 1800178.
  107. Cao, W.T.; Ouyang, H.; Xin, W.; Chao, S.; Ma, C.; Li, Z.; Chen, F.; Ma, M.G. A stretchable high output triboelectric nanogenerator improved by MXene liquid electrode with high electronegativity. Adv. Funct. Mater. 2020, 30, 2004181.
  108. Li, G.; Zhang, J.; Huang, F.; Wu, S.; Wang, C.H.; Peng, S. Transparent, stretchable and high-performance triboelectric nano-generator based on dehydration-free ionically conductive solid polymer electrode. Nano Energy 2021, 88, 106289.
  109. Li, Z.; Li, C.; Sun, W.; Bai, Y.; Li, Z.; Deng, Y. A Controlled biodegradable triboelectric nanogenerator based on PEGDA/Laponite hydrogels. ACS Appl. Mater. Interfaces 2023, 15, 12787–12796.
  110. Wu, Y.; Luo, Y.; Cuthbert, T.J.; Shokurov, A.V.; Chu, P.K.; Feng, S.; Menon, C. Hydrogels as Soft Ionic Conductors in Flexible and Wearable Triboelectric Nanogenerators. Adv. Sci. 2022, 9, 2106008.
  111. Li, K.; Zhang, D.; Zhang, H.; Wang, D.; Xu, Z.; Cai, H.; Xia, H. Triboelectric nanogenerators based on super-stretchable con-ductive hydrogels with the assistance of deep-learning for handwriting recognition. ACS Appl. Mater. Interfaces 2023, 15, 32993–33002.
  112. Panwar, V.; Babu, A.; Sharma, A.; Thomas, J.; Chopra, V.; Malik, P.; Rajput, S.; Mittal, M.; Guha, R.; Chattopadhyay, N.; et al. Tunable, conductive, self-healing, adhesive and injectable hydrogels for bioelectronics and tissue regeneration applications. J. Mater. Chem. B 2021, 9, 6260–6270.
  113. Chen, P.; Wang, Q.; Wan, X.; Yang, M.; Liu, C.; Xu, C.; Hu, B.; Feng, J.; Luo, Z. Wireless electrical stimulation of the vagus nerves by ultrasound-responsive programmable hydrogel nanogenerators for anti-inflammatory therapy in sepsis. Nano Energy 2021, 89, 106327.
  114. Zhang, H.; Zhang, D.; Wang, Z.; Xi, G.; Mao, R.; Ma, Y.; Wang, D.; Tang, M.; Xu, Z.; Luan, H. Ultrastretchable, self-healing conductive hydrogel-based triboelectric nanogenerators for human-computer interaction. ACS Appl. Mater. Interfaces 2023, 15, 5128–5138.
  115. Li, X.; Jiang, C.; Zhao, F.; Lan, L.; Yao, Y.; Yu, Y.; Ping, J.; Ying, Y. Fully stretchable triboelectric nanogenerator for energy harvesting and self-powered sensing. Nano Energy 2019, 61, 78–85.
  116. Cui, X.; Zhao, T.; Yang, S.; Xie, G.; Zhang, Z.; Zhang, Y.; Sang, S.; Lin, Z.H.; Zhang, W.; Zhang, H. A spongy electrode-brush-structured dual-mode triboelectric nanogenerator for harvesting mechanical energy and self-powered trajectory tracking. Nano Energy 2020, 78, 105381.
  117. Liu, Y.; Zheng, Y.; Wu, Z.; Zhang, L.; Sun, W.; Li, T.; Wang, D.; Zhou, F. Conductive elastic sponge-based triboelectric nano-generator (TENG) for effective random mechanical energy harvesting and ammonia sensing. Nano Energy 2021, 79, 105422.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
This entry is offline, you can click here to edit this entry!
Video Production Service
Feedback