Silicone-Based Triboelectric Nanogenerator for Water Wave Energy Harvesting

Research Progress of Triboelectric Nanogenerators for Ocean Wave Energy Harvesting

The ocean wave energy is considered one of the most promising forms of marine blue energy due to its vast reserves and high energy density. However, traditional electromagnetic power generation technology suffers from drawbacks such as high maintenance costs, heavy structures, and low conversion efficiency, which restricts its application range. The triboelectric nanogenerator (TENG) uses Maxwell displacement current as its internal driving force, which can efficiently convert irregular, low-frequency, and dispersed mechanical energy into electrical energy. The generator utilizes the coupling effect between contact electrification and electrostatic induction, showing the significant advantages of light weight, high cost effectiveness, and easy expansion. Compared with traditional mechanical energy harvesting techniques such as electromagnetic generators, triboelectric nanogenerators exhibit higher efficiency and output performance in the low-frequency range. Thus, wave power generation technology based on triboelectric nanogenerators has emerged as a highly potential alternative in this field. Herein, recent progress to summarize the latest advancements in TENG-based ocean wave energy capture is reviewed. More importantly, the actual progress of TENG with different structures in wave energy harvesting is discussed, providing an overview of the current research status in this field for relevant researchers.

Advances in TENGs for Marine Energy Harvesting and In Situ Electrochemistry

The large-scale use of ample marine energy will be one of the most important ways for human to achieve sustainable development through carbon neutral development plans. As a burgeoning technological method for electromechanical conversion, triboelectric nanogenerator (TENG) has significant advantages in marine energy for its low weight, cost-effectiveness, and high efficiency in low-frequency range. It can realize the efficient and economical harvesting of low-frequency blue energy by constructing the floating marine energy harvesting TENG. This paper firstly introduces the power transfer process and structural composition of TENG for marine energy harvesting in detail. In addition, the latest research works of TENG on marine energy harvesting in basic research and structural design are systematically reviewed by category. Finally, the advanced research progress in the power take-off types and engineering study of TENG with the marine energy are comprehensively generalized. Importantly, the challenges and problems faced by TENG in marine energy and in situ electrochemical application are summarized and the corresponding prospects and suggestions are proposed for the subsequent development direction and prospects to look forward to promoting the commercialization process of this field.

Development of Thermoplastic Bi-Component Electrodes for Triboelectric Impact Detection in Smart Textile Applications

Smart textiles provide a significant technological advancement, but their development must balance traditional textile properties with electronic features. To address this challenge, this study introduces a flexible, electrically conductive composite material that can be fabricated using a continuous bi-component extrusion process, making it ideal for sensor electrodes. The primary aim was to create a composite for the filament's core, combining multi-walled carbon nanotubes (MWCNTs), polypropylene (PP), and thermoplastic elastomer (TPE), optimised for conductivity and flexibility. This blend, suitable for bi-component extrusion processes, exemplifies the role of advanced materials in combining electrical conductivity, mechanical flexibility, and processability, which are essential for wearable technology. The composite optimisation balanced MWCNT (2.5, 5, 7.5, and 10 wt.%) and TPE (0, 25, and 50 wt.%) in a PP matrix. There was a significant decrease in electrical resistivity between 2.5 and 5 wt.% MWCNT, with electrical resistivity ranging from (7.64 ± 4.03)104 to (1.15 ± 0.10)10-1 Ω·m. Combining the composite with 25 wt.% TPE improved the flexibility, while with 50 wt.% TPE decreased tensile strength and hindered the masterbatch pelletising process. The final stage involved laminating the composite filament electrodes, with a 5 wt.% MWCNT/PP/(25 wt.% TPE) core and a TPE sheath, into a textile triboelectric impact detection sensor. This sensor, responding to contact and separation, produced an output voltage of approximately 5 V peak-to-peak per filament and 15 V peak-to-peak with five filaments under a 100 N force over 78.54 cm2. This preliminary study demonstrates an innovative approach to enhance the flexibility of conductive materials for smart textile applications, enabling the development of triboelectric sensor electrodes with potential applications in impact detection, fall monitoring, and motion tracking.

Stretchable and Elastic Triboelectric Nanogenerator with Liquid-Metal Grid-Patterned Single Electrode for Wearable Energy-Harvesting Devices

Triboelectric nanogenerators (TENGs) have garnered significant attention as efficient energy-harvesting systems for sustainable energy sources in the field of self-powered wearable devices. Various conductive materials are used to build wearable devices, among which, gallium-based liquid metal (LM) is a preferred electrode owing to its fluidity and metallic conductivity even when strained. In this study, a stretchable, elastic, and wearable triboelectric nanogenerator is designed using a single electrode fabricated by embedding LM grid patterns into a stretchable silicone substrate through a two-step spray-coating process. Contrary to conventional double-electrode TENG that is challenging to integrate to human body, the LM grid-patterned single-electrode TENG (LMG-SETENG) has a simplified design and provides more flexibility. The LMG-SETENG can generate voltages of up to 100 V via triboelectrification upon contact with the human body, even under various degrees of strain, owing to the fluidity of the LM electrode. The generated energy can be utilized as a sustainable energy source to power various small appliances. Moreover, the proposed LMG-SETENG can be utilized in soft robotics, electronic skin, and healthcare devices.

Advancements and Future Prospects in Ocean Wave Energy Harvesting Technology Based on Micro-Energy Technology

Marine wave energy exhibits significant potential as a renewable resource due to its substantial energy storage capacity and high energy density. However, conventional wave power generation technologies often suffer from drawbacks such as high maintenance costs, cumbersome structures, and suboptimal conversion efficiencies, thereby limiting their potential. The wave power generation technologies based on micro-energy technology have emerged as promising new approaches in recent years, owing to their inherent advantages of cost-effectiveness, simplistic structure, and ease of manufacturing. This paper provides a comprehensive overview of the current research status in wave energy harvesting through micro-energy technologies, including detailed descriptions of piezoelectric nanogenerators, electromagnetic generators, triboelectric nanogenerators, dielectric elastomer generators, hydrovoltaic generators, and hybrid nanogenerators. Finally, we provide a comprehensive overview of the prevailing issues and challenges associated with these technologies, while also offering insights into the future development trajectory of wave energy harvesting technology.

Piezoelectric Energy Harvester Technologies: Synthesis, Mechanisms, and Multifunctional Applications

Piezoelectric energy harvesters have gained significant attention in recent years due to their ability to convert ambient mechanical vibrations into electrical energy, which opens up new possibilities for environmental monitoring, asset tracking, portable technologies and powering remote "Internet of Things (IoT)" nodes and sensors. This review explores various aspects of piezoelectric energy harvesters, discussing the structural designs and fabrication techniques including inorganic-based energy harvesters (i.e., piezoelectric ceramics and ZnO nanostructures) and organic-based energy harvesters (i.e., polyvinylidene difluoride (PVDF) and its copolymers). The factors affecting the performance and several strategies to improve the efficiency of devices have been also explored. In addition, this review also demonstrated the progress in flexible energy harvesters with integration of flexibility and stretchability for next-generation wearable technologies used for body motion and health monitoring devices. The applications of the above devices to harvest various forms of mechanical energy are explored, as well as the discussion on perspectives and challenges in this field.

Elastic Self-Recovering Hybrid Nanogenerator for Water Wave Energy Harvesting and Marine Environmental Monitoring

To achieve large-scale development of triboelectric nanogenerators (TENGs) for water wave energy harvesting and powering the colossal sensors widely distributed in the ocean, facile and scalable TENGs with high output are urgently required. Here, an elastic self-recovering hybrid nanogenerator (ES-HNG) is proposed for water wave energy harvesting and marine environmental monitoring. The elastic skeletal support of the ES-HNG is manufactured using three-dimensional (3D) printing technology, which is more conducive to the large-scale integration of the ES-HNG. Moreover, the combination of a TENG and an electromagnetic generator (EMG) optimizes the utilization of device space, leading to enhanced energy harvesting efficiency. Experimental results demonstrate that the TENG achieves a peak power output of 42.68 mW, and the EMG reaches a peak power output of 4.40 mW. Furthermore, various marine environment monitoring sensors, such as a self-powered wireless meteorological monitoring system, a wireless alarm system, and a water quality monitoring pen, have been successfully powered by the sophisticated ES-HNG. This work introduces an ES-HNG for water wave energy harvesting, which demonstrates potential in marine environment monitoring and offers a new solution for the sustainable development of the marine internet of things.

3D Printing of Flexible BaTiO3/Polydimethylsiloxane Piezocomposite with Aligned Particles for Enhanced Energy Harvesting

With the rapid development of human-machine interactions and artificial intelligence, the demand for wearable electronic devices is increasing uncontrollably all over the world; however, an unsustainable power supply for such sensors continues to restrict their applications. In the present work, piezoelectric barium titanate (BaTiO3) ceramic powder with excellent properties was prepared from milled precursors through a solid-state reaction. To fabricate a flexible device, the as-prepared BaTiO3 powder was mixed with polydimethylsiloxane (PDMS) polymer. The BaTiO3/PDMS ink with excellent rheological properties was extruded smoothly by direct ink writing technology (DIW). BaTiO3 particles were aligned due to the shear stress effect during the printing process. Subsequently, the as-printed composite was assembled into a sandwich-type device for effective energy harvesting. It was observed that the maximum output voltage and current of this device reached 68 V and 720 nA, respectively, for a BaTiO3 content of 6 vol %. Therefore, the material extrusion-based three-dimensional (3D) printing technique can be used to prepare flexible piezoelectric composites for efficient energy harvesting.

An Ultrasensitive Laser-Induced Graphene Electrode-Based Triboelectric Sensor Utilizing Trapped Air as Effective Dielectric Layer

Air, a widely recognized dielectric material, is employed as a dielectric layer in this study. We present a triboelectric sensor with a laser-induced graphene (LIG) electrode and an air-trapped pad using silicone rubber (SR). A very thin device with a thickness of 1 mm and an effective gap for contact-separation between the films of silicone rubber and polyimide (PI) of 0.6 mm makes the device extremely highly sensitive for very low amplitudes of pressure. The fabrication of LIG as an electrode material on the surface of PI is the key reason for the fabrication of the thin sensor. In this study, we showed that the fabricated air-trapped padded sensor (ATPS) has the capability to generate an output voltage of ~32 V, a short-circuit current of 1.2 µA, and attain a maximum power density of 139.8 mW m-2. The performance of the ATPS was compared with a replicated device having a hole on the pad, allowing air to pass through during contact-separation. The observed degradation in the electrical output suggests that the trapped air in the pad plays a crucial role in enhancing the output voltage. Therefore, the ATPS emerges as an ultra-sensitive sensor for healthcare sensing applications.

Three-Dimensional Printing of Triboelectric Nanogenerators by Digital Light Processing Technique for Mechanical Energy Harvesting

Triboelectric nanogenerators (TENGs) represent intriguing technology to harvest human mechanical movements for powering wearable and portable electronics. Differently, compared to conventional fabrication approaches, additive manufacturing can allow the fabrication of TENGs with good dimensional resolution, high reproducibility, and quick production processes and, in particular, the obtainment of complex and customized structures. Among 3D printing technologies, digital light processing (DLP) is well-known for being the most flexible to produce functional devices by controlling both the geometry and the different ingredients of printable resins. On the other hand, DLP was not exploited for TENG fabrication, and consequently, the knowledge of the performance of 3D printable materials as charge accumulators upon friction is limited. Here, the application of the DLP technique to the 3D printing of triboelectric nanogenerators is studied. First, several printable materials have been tested as triboelectric layers to define a triboelectric series of DLP 3D printable materials. Then, TENG devices with increased geometrical complexity were printed, showcasing the ability to harvest energy from human movement. The method presented in this work illustrates how the DLP may represent a valuable and flexible solution to fabricate triboelectric nanogenerators, also providing a triboelectric classification of the most common photocurable resins.

Preparation of carbon black/silicone rubber composites with large-area-homogeneous-low electrical-resistance used as electroplating matrix

Conductive carbon black (CCB) is an important filler in stretchable conductive silicone rubber (CSR) composites. However, due to the active oxygen-containing groups on CCB, introducing it into silicone rubber (SR) may cause SR to not completely cure. Surface modification of CCB may ease the problem but at the cost of reducing the electrical conductivity of pristine CCB. In this work, the curing and crosslinking performance of CCB/SR is detected in detail, the hydroxyl groups (-OH) carried by CCB can react with the silicon-hydrogen group (Si-H) with the existence of Pt catalyst, causing insufficiency of the hydrosilylation reaction thus hindering the solidifying process of silicon rubber. To take advantage of this reaction, more hydrogen silicone oil (PHMS) possessing silicon-hydrogen bonds is introduced into the system to improve the curing degree as well as fix the CCB in the crosslinked network. Due to the lock-in effect of CCB, the resistance of CSR samples is stable after several hundred bending cycles, and the composite's tensile strength is three times that of the pure SR samples. Besides, the size of the composites can expand to dozens of centimeters or even a few meters with uniform electric conductivity. This composite has resistance as low as 10.20 Ω and is suitable to make electroplating mold, and a rapid plating rate of 2.4 mm/24 h can be achieved. Meanwhile, the overall properties make this CSR composite have potential applications in mold manufacture, flexible electronics, and other related fields.

Directed molecular structure design of coordination polymers with different ligands for regulating output performance of triboelectric nanogenerators

A triboelectric nanogenerator (TENG) provides an effective method to harvest mechanical energy from the environment. The morphology and structure of frictional electrode materials of this type of device affect the output performance significantly. Metal-organic coordination polymers (CPs) with special structure advantages offer a vast pool of materials enabling high performances. Two Co-CPs based on terephthalic acid and 2,5-dihydroxyterephthalic acid ligands, respectively, were used to fabricate TENGs. Detailed electrical characterizations of the TENG devices revealed that the introduction of the substituent groups in the organic ligands leads to the structural changes of CPs, which ultimately leads to significant differences in the output performance.

Silicone Rubber Based-Conductive Composites for Stretchable "All-in-One" Microsystems

Wearable electronics with development trends such as miniaturization, multifunction, and smart integration have become an important part of the Internet of Things (IoT) and have penetrated various sectors of modern society. To meet the increasing demands of wearable electronics in terms of deformability and conformability, many efforts have been devoted to overcoming the nonstretchable and poor conformal properties of traditional functional materials and endowing devices with outstanding mechanical properties. One of the promising approaches is composite engineering in which traditional functional materials are incorporated into the various polymer matrices to develop different kinds of functional composites and construct different functions of stretchable electronics. Herein, we focus on the approach of composite engineering and the polymer matrix of silicone rubber (SR), and we summarize the state-of-the-art details of silicone rubber-based conductive composites (SRCCs), including a summary of their conductivity mechanisms and synthesis methods and SRCC applications for stretchable electronics. For conductivity mechanisms, two conductivity mechanisms of SRCC are emphasized: percolation theory and the quantum tunneling mechanism. For synthesis methods of SRCCs, four typical approaches to synthesize different kinds of SRCCs are investigated: mixing/blending, infiltration, ion implantation, and in situ formation. For SRCC applications, different functions of stretchable electronics based on SRCCs for interconnecting, sensing, powering, actuating, and transmitting are summarized, including stretchable interconnects, sensors, nanogenerators, antennas, and transistors. These functions reveal the feasibility of constructing a stretchable all-in-one self-powered microsystem based on SRCC-based stretchable electronics. As a prospect, this microsystem is expected to integrate the functional sensing modulus, the energy harvesting modulus, and the process and response modulus together to sense and respond to environmental stimulations and human physiological signals.

Underwater wireless communication via TENG-generated Maxwell's displacement current

Underwater communication is a critical and challenging issue, on account of the complex underwater environment. This study introduces an underwater wireless communication approach via Maxwell's displacement current generated by a triboelectric nanogenerator. Underwater electric field can be generated through a wire connected to a triboelectric nanogenerator, while current signal can be inducted in an underwater receiver certain distance away. The received current signals are basically immune to disturbances from salinity, turbidity and submerged obstacles. Even after passing through a 100 m long spiral water pipe, the electric signals are not distorted in waveform. By modulating and demodulating the current signals generated by a sound driven triboelectric nanogenerator, texts and images can be transmitted in a water tank at 16 bits/s. An underwater lighting system is operated by the triboelectric nanogenerator-based voice-activated controller wirelessly. This triboelectric nanogenerator-based approach can form the basis for an alternative wireless communication in complex underwater environments.

Anti-Overturning Fully Symmetrical Triboelectric Nanogenerator Based on an Elliptic Cylindrical Structure for All-Weather Blue Energy Harvesting

Triboelectric nanogenerators (TENGs) have shown promising potential for large-scale blue energy harvesting. However, the lack of reasonable designs has largely hindered TENG from harvesting energy from both rough and tranquil seas. Herein, a fully symmetrical triboelectric nanogenerator based on an elliptical cylindrical structure (EC-TENG) is proposed for all-weather blue energy harvesting. The novel elliptical cylindrical shell provides a unique self-stability, high sensitivity to wave triggering, and most importantly, an anti-overturning capability for the EC-TENG. Moreover, benefiting from its internal symmetrical design, the EC-TENG can produce energy normally, even if it was overturned under a rude oscillation in the rough seas, which distinguishes this work from previous reported TENGs. The working mechanism and output performance are systematically studied. The as-fabricated EC-TENG is capable of lighting 400 light-emitting diodes and driving small electronics. More than that, an automatic monitoring system powered by the EC-TENG can also monitor the water level in real-time and provide an alarm if necessary. This work presents an innovative and reliable approach toward all-weather wave energy harvesting in actual marine environments.

A Novel Electrochemical Immunosensor Based on COF-LZU1 as Precursor to Form Heteroatom-Doped Carbon Nanosphere for CA19-9 Detection

Porous carbon sphere materials have a large variety of applications in several fields due to the large surface area, adaptable porosity, and good conductivity they possess. Obtaining a steady carbon sphere using the green synthesis method remains a significant challenge. In this experiment, covalent organic frameworks (COFs) were used as a precursor and Fe₃O₄NPs were integrated into the precursor in order to synthesize a porous carbon sphere material using the one-step pyrolysis method. COFs have an ordered porous structure, perpetual porosity, large surface area, and low density and display good environmental tolerance. These properties make them an excellent precursor for synthesizing porous carbon sphere, which maintains good morphology at high temperatures, and it is not involved in the removal of dangerous reagent and small size restrictions during the synthesis process. In addition to the formation of a porous carbon sphere, transition metal carbon material that contains N element can be an active catalyst. The composites exhibit better activity when Fe is doped into carbon materials containing N element than that of other doped transition metals including Mn and Co. In this situation, the integration of Fe₃O₄NPs and N element in the COF precursor exposed the active sites of the composites and the two substances synergistically improved the electrocatalytic properties, and the composites were named Fe₃O₄@NPCS. The constructed Fe₃O₄@NPCS/GCE immunosensor was applied as a means of detecting CA19-9 antigen and presented a wide linear range from 0.00001 to 10 U/mL with a low detection limit of 2.429 μU/mL (S/N = 3). In addition, the prepared immunosensor was utilized for detecting CA19-9 antigen in the real human serum, and the recovery rates were in the range from 95.24% to 106.38%. Therefore, a porous carbon sphere prepared by COFs as a precursor can be applied for the detection of CA19-9 antigen in real samples, which could be an excellent strategy for CA19-9 antigen detection and could potentially promote the development of COF materials in various electrochemical fields.

Electrospun Nanofiber Covered Polystyrene Micro-Nano Hybrid Structures for Triboelectric Nanogenerator and Supercapacitor

Recently, tremendous research on small energy supply devices is gaining popularity with the immerging Internet of Things (IoT) technologies. Especially, energy conversion and storage devices can provide opportunities for small electronics. In this research, a micro-nano structured design of electrodes is newly developed for high performing hybrid energy systems with the improved effective surface area. Further, it could be simply fabricated through two-steps synthesis of electrospinning and glass transition of a novel polystyrene (PS) substrate. Herein, the electro-spun nanofiber of polyacrylonitrile (PAN) and Nylon 66 (Nylon) are applied to the dielectric layer of a triboelectric generator (TENG), while the PAN and polyaniline (PANI) composites is utilized as an electroactive material of supercapacitor (SC). As a result, the self-charging power system is successfully integrated with the wrinkled PAN/PS (W-PAN/PS@PANI)-SC and W-TENG by using a rectifier. According to the fabricated hybrid energy systems, the electrical energy produced by W-TENG can be successfully stored into as-fabricated W-PAN/PS@PANI-SC and can also turn on a commercial green LED with the stored energy. Therefore, the micro-nano structured electrode designed for hybrid energy systems can contribute to improve the energy conversion and storage performance of various electronic devices.

Methyl Orange-Doped Polypyrrole Promoting Growth of ZIF-8 on Cellulose Fiber with Tunable Tribopolarity for Triboelectric Nanogenerator

Cellulose fiber (CelF) is a biodegradable and renewable material with excellent performance but negligible triboelectric polarizability. Methods to enhance and rationally tune the triboelectric properties of CelF are needed to further its application for energy harvesting. In this work, methyl-orange-doped polypyrrole (MO-PPy) was in situ coated on CelF as a mediating layer to promote the growth of metal–organic framework ZIF-8 and to construct a cellulose-based triboelectric nanogenerator (TENG). The results showed that a small amount of MO-PPy generated in situ significantly promoted the growth of ZIF-8 on CelF, and the ZIF-8 deposition ratio was able to increase from 7.8% (ZIF-8/CelF) to 31.8% (ZIF-8/MO-PPy@CelF). ZIF-8/MO-PPy@CelF remained electrically conductive and became triboelectrically positive, and the triboelectricity’s positivity was improved with the increase in the ZIF-8 deposition ratio. The cellulose-based TENG constructed with ZIF-8/MO-PPy@CelF (31.8% ZIF-8 deposition ratio) and polytetrafluoroethylene (PTFE) could generate a transfer charge of 47.4 nC, open-circuit voltage of 129 V and short-circuit current of 6.8 μA—about 4 times higher than those of ZIF-8/CelF (7.8% ZIF-8 deposition ratio)—and had excellent cycling stability (open-circuit voltage remained almost constant after 10,000 cycles). MO-PPy not only greatly facilitated the growth of ZIF-8 on CelF, but also acted as an electrode active phase for TENG. The novel TENG based on ZIF-8/MO-PPy@CelF composite has cheerful prospects in many applications, such as self-powered supercapacitors, sensors and monitors, smart pianos, ping-pong tables, floor mats, etc.

A Robust and Wearable Triboelectric Tactile Patch as Intelligent Human-Machine Interface

The human-machine interface plays an important role in the diversified interactions between humans and machines, especially by swaping information exchange between human and machine operations. Considering the high wearable compatibility and self-powered capability, triboelectric-based interfaces have attracted increasing attention. Herein, this work developed a minimalist and stable interacting patch with the function of sensing and robot controlling based on triboelectric nanogenerator. This robust and wearable patch is composed of several flexible materials, namely polytetrafluoroethylene (PTFE), nylon, hydrogels electrode, and silicone rubber substrate. A signal-processing circuit was used in this patch to convert the sensor signal into a more stable signal (the deviation within 0.1 V), which provides a more effective method for sensing and robot control in a wireless way. Thus, the device can be used to control the movement of robots in real-time and exhibits a good stable performance. A specific algorithm was used in this patch to convert the 1D serial number into a 2D coordinate system, so that the click of the finger can be converted into a sliding track, so as to achieve the trajectory generation of a robot in a wireless way. It is believed that the device-based human-machine interaction with minimalist design has great potential in applications for contact perception, 2D control, robotics, and wearable electronics.

Triboelectric Nanogenerators for Energy Harvesting in Ocean: A Review on Application and Hybridization

With recent advancements in technology, energy storage for gadgets and sensors has become a challenging task. Among several alternatives, the triboelectric nanogenerators (TENG) have been recognized as one of the most reliable methods to cure conventional battery innovation’s inadequacies. A TENG transfers mechanical energy from the surrounding environment into power. Natural energy resources can empower TENGs to create a clean and conveyed energy network, which can finally facilitate the development of different remote gadgets. In this review paper, TENGs targeting various environmental energy resources are systematically summarized. First, a brief introduction is given to the ocean waves’ principles, as well as the conventional energy harvesting devices. Next, different TENG systems are discussed in details. Furthermore, hybridization of TENGs with other energy innovations such as solar cells, electromagnetic generators, piezoelectric nanogenerators and magnetic intensity are investigated as an efficient technique to improve their performance. Advantages and disadvantages of different TENG structures are explored. A high level overview is provided on the connection of TENGs with structural health monitoring, artificial intelligence and the path forward.

Volatile organic compounds sensing based on Bennet doubler-inspired triboelectric nanogenerator and machine learning-assisted ion mobility analysis

Ion mobility analysis is a well-known analytical technique for identifying gas-phase compounds in fast-response gas-monitoring systems. However, the conventional plasma discharge system is bulky, operates at a high temperature, and inappropriate for volatile organic compounds (VOCs) concentration detection. Therefore, we report a machine learning (ML)-enhanced ion mobility analyzer with a triboelectric-based ionizer, which offers good ion mobility selectivity and VOC recognition ability with a small-sized device and non-strict operating environment. Based on the charge accumulation mechanism, a multi-switched manipulation triboelectric nanogenerator (SM-TENG) can provide a direct current (DC) bias at the order of a few hundred, which can be further leveraged as the power source to obtain a unique and repeatable discharge characteristic of different VOCs, and their mixtures, with a special tip-plate electrode configuration. Aiming to tackle the grand challenge in the detection of multiple VOCs, the ML-enhanced ion mobility analysis method was successfully demonstrated by extracting specific features automatically from ion mobility spectrometry data with ML algorithms, which significantly enhance the detection ability of the SM-TENG based VOC analyzer, showing a portable real-time VOC monitoring solution with rapid response and low power consumption for future internet of things based environmental monitoring applications.

Environmental energy harvesting based on triboelectric nanogenerators

With the fast development of the Internet of Things, the energy supply for electronics and sensors has become a critical challenge. The triboelectric nanogenerator (TENG), which can transfer mechanical energy from the surrounding environment into electricity, has been recognized as the most promising alternative technology to remedy the shortcomings of traditional battery technology. Environmental mechanical energy widely exists in activities in nature and these environmental energy sources can enable TENGs to achieve a clean and distributed energy network, which can finally benefit the innovation of various wireless devices. In this review, TENGs targeting different environmental energy sources have been systematically summarized and analyzed. Firstly, we give a brief introduction to the basic principle and working modes of the TENG. Then, TENGs targeting different energy sources, from blowing wind and raindrops to pounding waves, noise signalling, and so on, are summarized based on their design concept and output performance. In addition, combined with other energy technologies such as solar cells, electromagnetic generators, and piezoelectric nanogenerators, the application of hybrid nanogenerators is elaborated under different scenarios. Finally, the challenges, limitations, and future research trends of environmental energy collection are outlined.

Natural and Eco-Friendly Materials for Triboelectric Energy Harvesting

Triboelectric nanogenerators (TENGs) are promising electric energy harvesting devices as they can produce renewable clean energy using mechanical excitations from the environment. Several designs of triboelectric energy harvesters relying on biocompatible and eco-friendly natural materials have been introduced in recent years. Their ability to provide customizable self-powering for a wide range of applications, including biomedical devices, pressure and chemical sensors, and battery charging appliances, has been demonstrated. This review summarizes major advances already achieved in the field of triboelectric energy harvesting using biocompatible and eco-friendly natural materials. A rigorous, comparative, and critical analysis of preparation and testing methods is also presented. Electric power up to 14 mW was already achieved for the dry leaf/polyvinylidene fluoride-based TENG devices. These findings highlight the potential of eco-friendly self-powering systems and demonstrate the unique properties of the plants to generate electric energy for multiple applications.

Integrated Triboelectric Nanogenerators in the Era of the Internet of Things

Since their debut in 2012, triboelectric nanogenerators (TENGs) have attained high performance in terms of both energy density and instantaneous conversion, reaching up to 500 W m-2 and 85%, respectively, synchronous with multiple energy sources and hybridized designs. Here, a comprehensive review of the design guidelines of TENGs, their performance, and their designs in the context of Internet of Things (IoT) applications is presented. The development stages of TENGs in large-scale self-powered systems and technological applications enabled by harvesting energy from water waves or wind energy sources are also reviewed. This self-powered capability is essential considering that IoT applications should be capable of operation anywhere and anytime, supported by a network of energy harvesting systems in arbitrary environments. In addition, this review paper investigates the development of self-charging power units (SCPUs), which can be realized by pairing TENGs with energy storage devices, such as batteries and capacitors. Consequently, different designs of power management circuits, supercapacitors, and batteries that can be integrated with TENG devices are also reviewed. Finally, the significant factors that need to be addressed when designing and optimizing TENG-based systems for energy harvesting and self-powered sensing applications are discussed.

Unveiling Peritoneum Membrane for a Robust Triboelectric Nanogenerator

Triboelectric nanogenerators (TENGs) are smart alternative energy harvesters to convert mechanical energy into electrical energy to power small and portable electronic devices. A key challenge in fabricating an efficient TENG lies in the choice of an active material in addition to the mechanical stability and robust output performance of the device. This report suggests, for the first time, the use of a peritoneum membrane as a triboelectrically positive material for designing TENGs. The peritoneum covers the abdominal wall and diaphragm of mammals except for the kidneys and the adrenal glands and consists of a structure of a well-defined network of elastic fibers. Our peritoneum-based TENG (p-TENG) can generate an open-circuit output voltage of ∼550 V, output current density of ∼100 mA m^-2, and instantaneous output power density of 9.4 Wm^-2. This work demonstrates the p-TENG as a portable power source, a self-powered pedometer, and a speedometer, which conveys its futuristic applications for health care purposes. Our p-TENG is highly stable, delivering a constant output voltage of ∼550 V over a period of 90 days. The introduction of a biowaste peritoneum membrane as a triboelectrically positive component in the TENG has great potential as a portable alternative energy source owing to its abundance, stability, low cost, and ease of fabrication.

Triboelectric filtering for air purification

Air pollution becomes more and more serious with the rapid development of the society, and the haze caused by particulate matters (PMs) has become a global problem. Thus seeking an effective technology for removing the airborne PMs or other pollutants is much desirable for alleviating the air pollution. The newly invented triboelectric nanotechnology can realize efficient air filtering with obvious advantages over traditional fibrous filtering and electrostatic precipitation. Here, a review is provided for recent progress in air filter by utilizing the triboelectric nanotechnology, starting from the choices of triboelectric materials and main features of triboelectric nanotechnology. The mechanism of triboelectric air filtering technology was presented as the coupling of triboelectric filtering and mechanical filtering. Then the approaches of air filtering were summarized as the triboelectric nanogenerator (TENG)-driven air filtering, TENG-enhanced nanofiber air filtering, and self-powered triboelectric air filtering. The device structure, working principle and filtering performance were systematically discussed. Furthermore, the industry products which have been developed based on the triboelectric filtering technology were introduced.