Polydirectional Microvibration Energy Collection for Self-Powered Multifunctional Systems Based on Hybridized Nanogenerators

Research on Vibration Accumulation Self-Powered Downhole Sensor Based on Triboelectric Nanogenerators

In drilling operations, measuring vibration parameters is crucial for enhancing drilling efficiency and ensuring safety. Nevertheless, the conventional vibration measurement sensor significantly extends the drilling cycle due to its dependence on an external power source. Therefore, we propose a vibration-accumulation-type self-powered sensor in this research, aiming to address these needs. By leveraging vibration accumulation and electromagnetic power generation to accelerate charging, the sensor's output performance is enhanced through a complementary charging mode. The experimental results regarding sensing performance demonstrate that the sensor possesses a measurement range spanning from 0 to 11 Hz, with a linearity of 3.2% and a sensitivity of 1.032. Additionally, it exhibits a maximum average measurement error of less than 4%. The experimental results of output performance measurement indicate that the sensor unit and generator set exhibit a maximum output power of 0.258 μW and 25.5 mW, respectively, and eight LED lights can be lit at the same time. When the sensor unit and power generation unit output together, the maximum output power of the sensor is also 25.5 mW. Furthermore, we conducted tests on the sensor's output signal in conditions of high temperature and humidity, confirming its continued functionality in such environments. This sensor not only achieves self-powered sensing capabilities, addressing the power supply challenges faced by traditional downhole sensors, but also integrates energy accumulation with electromagnetic power generation to enhance its output performance. This innovation enables the sensor to harness downhole vibration energy for powering other micro-power devices, showcasing promising application prospects.

Swing Origami-Structure-Based Triboelectric Nanogenerator for Harvesting Blue Energy toward Marine Environmental Applications

The appearance of triboelectric nanogenerators (TENG) provides a promising energy technology for harvesting abundant water wave energy. Here, the design and fabrication of a swinging origami-structured TENG (SO-TENG) tailored specifically for water wave energy harvesting are presented. The design incorporates an oscillating structure weighted at the bottom, inducing reciprocating motion propelled by the inertia of passing water waves. This reciprocating motion efficiently converts mechanical into electrical energy through the origami structure. By employing origami as the monomer structure, the surface contact area between friction layers is enhanced, thereby optimizing output performance. the swinging structure, combined with the placement of heavy objects, enhances the folding and contact of the origami, allowing it to operate effectively in low-frequency water wave environments. This configuration exhibits robust power generation capabilities, making it suitable for powering small electronic devices in water wave environments. Furthermore, when applied to metal corrosion protection, the SO-TENG demonstrates notable efficacy. Compared to exposed Q235 carbon steel, Q235 carbon steel protected by SO-TENG exhibits a significant reduction in open-circuit potential drop, approximately 155 mV, indicative of superior anti-corrosion properties. It lays a solid foundation for water wave energy collection and self-powered metal corrosion protection in marine environments.

Enhancing Output Signals of Sport Monitors Based on Triboelectric Porous PVDF Nanogenerators via Concaving Cells and Cell-Packing Structures

Porous triboelectric polymer materials are widely used in portable sensors due to their lightweight and suitable mechanical performance, but their triboelectric properties need to be improved. Here, we propose a two-step strategy to concave the cell and cell-packing structure of triboelectric materials based on porous poly(vinylidene fluoride) (PVDF). The first step is to prepare triboelectric nanogenerators (TENGs) of PVDF with a concave cell-packing structure via oriented phase inversion. The second step is to concave the cells by radial and axial compression. The results reveal that the concavities in the cell structure at the radial direction and in the cell-packing structure at the axial direction improve the output signals of the porous PVDF TENG by ca. 150 and 110%, respectively. By contrast, the concaving in cell structure at the radial direction exerts a positive effect on triboelectric performance only when the radial compression strain is not bigger than 17.5%, especially when the cell wall is thin (ca. 0.85 μm). Meanwhile, the concavity-based strategy eliminates the irreversible deformation behavior of the porous PVDF material, enhancing its elasticity. The stability test shows that the sensor based on those materials is stable under 12,500 cycles, and the variance in the square derivation of output voltage is less than 1% during the cycle friction. Such stable and triboelectric-improved materials are assembled into sports-monitoring devices, providing an idea for the application of TENG in smart sensing.

High-performance hybrid nanogenerator for self-powered wireless multi-sensing microsystems

Wireless sensor network nodes are widely used in wearable devices, consumer electronics, and industrial electronics and are a crucial component of the Internet of Things (IoT). Recently, advanced power technology with sustainable energy supply and pollution-free characteristics has become a popular research focus. Herein, to realize an unattended and reliable power supply unit suitable for distributed IoT systems, we develop a high-performance triboelectric-electromagnetic hybrid nanogenerator (TEHNG) to harvest mechanical energy. The TEHNG achieves a high load power of 21.8 mW by implementing improvements of material optimization, configuration optimization and pyramid microstructure design. To realize a self-powered integrated microsystem, a power management module, energy storage module, sensing signal processing module, and microcontroller unit are integrated into the TEHNG. Furthermore, an all-in-one wireless multisensing microsystem comprising the TEHNG, the abovementioned integrated functional circuit and three sensors (temperature, pressure, and ultraviolet) is built. The milliwatt microsystem operates continuously with the TEHNG as the only power supply, achieving self-powered operations of sensing environmental variables and transmitting wireless data to a terminal in real time. This shows tremendous application potential in the IoT field.

Recent Advances in Mechanical Vibration Energy Harvesters Based on Triboelectric Nanogenerators

With the development of autonomous/smart technologies and the Internet of Things (IoT), tremendous wireless sensor nodes (WSNs) are of great importance to realize intelligent mechanical engineering, which is significant in the industrial and social fields. However, current power supply methods, cable and battery for instance, face challenges such as layout difficulties, high cost, short life, and environmental pollution. Meanwhile, vibration is ubiquitous in machinery, vehicles, structures, etc., but has been regarded as an unwanted by-product and wasted in most cases. Therefore, it is crucial to harvest mechanical vibration energy to achieve in situ power supply for these WSNs. As a recent energy conversion technology, triboelectric nanogenerator (TENG) is particularly good at harvesting such broadband, weak, and irregular mechanical energy, which provides a feasible scheme for the power supply of WSNs. In this review, recent achievements of mechanical vibration energy harvesting (VEH) related to mechanical engineering based on TENG are systematically reviewed from the perspective of contact-separation (C-S) and freestanding modes. Finally, existing challenges and forthcoming development orientation of the VEH based on TENG are discussed in depth, which will be conducive to the future development of intelligent mechanical engineering in the era of IoT.

Hybrid Nanogenerators for Ocean Energy Harvesting: Mechanisms, Designs, and Applications

The ocean holds vast potential as a renewable energy source, but harnessing its power has been challenging due to low-frequency and high-amplitude stimulation. However, hybrid nanogenerators (HNGs) offer a promising solution to convert ocean energy into usable power efficiently. With their high sensitivity and flexible design, HNGs are ideal for low-frequency environments and remote ocean regions. Combining triboelectric nanogenerators (TENGs) with piezoelectric nanogenerators (PENGs) and electromagnetic nanogenerators (EMGs) creates a unique hybrid system that maximizes energy harvesting. Ultimately, hybrid energy-harvesting systems offer a sustainable and reliable solution for growing energy needs. This study provides an in-depth review of the latest research on ocean energy harvesting by hybrid systems, focusing on self-powered applications. The article also discusses primary hybrid designs for devices, powering self-powered units such as wireless communication systems, climate monitoring systems, and buoys as applications. The potential of HNGs is enormous, and with rapid advancements in research and fabrication, these systems are poised to revolutionize ocean energy harvesting. It outlines the pros and cons of HNGs and highlights the major challenges that must be overcome. Finally, future outlooks for hybrid energy harvesters are also discussed.

A Self-Powered, Highly Embedded and Sensitive Tribo-Label-Sensor for the Fast and Stable Label Printer

Label-sensor is an essential component of the label printer which is becoming a most significant tool for the development of Internet of Things (IoT). However, some drawbacks of the traditional infrared label-sensor make the printer fail to realize the high-speed recognition of labels as well as stable printing. Herein, we propose a self-powered and highly sensitive tribo-label-sensor (TLS) for accurate label identification, positioning and counting by embedding triboelectric nanogenerator into the indispensable roller structure of a label printer. The sensing mechanism, device parameters and deep comparison with infrared sensor are systematically studied both in theory and experiment. As the results, TLS delivers 6 times higher signal magnitude than traditional one. Moreover, TLS is immune to label jitter and temperature variation during fast printing and can also be used for transparent label directly and shows long-term robustness. This work may provide an alternative toolkit with outstanding advantages to improve current label printer and further promote the development of IoT.

Self-Powered Non-Contact Motion Vector Sensor for Multifunctional Human-Machine Interface

Sensors as the significant units of the Internet of Things play an important role in the field of information interaction. Non-contact sensors have the advantages of flexible manipulation and a longer lifespan but it is constrained in motion detection due to their relative single detection function. Herein, a self-powered non-contact motion vector sensor (NMVS) for the multifunctional human-machine interface is reported. Based on the electrostatic induction effect, the motion vector is measured according to the output electrical signals from the non-contact triboelectric nanogenerator (NC-TENG). By simulation analysis and experimental validation, the output characteristics of NC-TENG dependence on structural and motion parameters are investigated in detail. On this basis, the resolution of NMVS is improved and exhibits for non-contact micro-vibration monitoring, rehabilitation gait detection, contactless smart lock, and the non-contact limit alarm. This work not only proposes an ingenious strategy for non-contact motion vector detection but also demonstrates the promising prospects of a multifunctional human-machine interface in intelligent electronics, health rehabilitation, and industrial inspection.

A Review on Kinetic Energy Harvesting with Focus on 3D Printed Electromagnetic Vibration Harvesters

The increasing amount of Internet of Things (IoT) devices and wearables require a reliable energy source. Energy harvesting can power these devices without changing batteries. Three-dimensional printing allows us to manufacture tailored harvesting devices in an easy and fast way. This paper presents the development of hybrid and non-hybrid 3D printed electromagnetic vibration energy harvesters. Various harvesting approaches, their utilised geometry, functional principle, power output and the applied printing processes are shown. The gathered harvesters are analysed, challenges examined and research gaps in the field identified. The advantages and challenges of 3D printing harvesters are discussed. Reported applications and strategies to improve the performance of printed harvesting devices are presented.

Electromagnetic–Triboelectric Hybridized Nanogenerators

Since the triboelectric nanogenerator (TENG) was invented, it has received extensive attention from researchers. Among the many pieces of research based on TENG, the research of hybridized generators is progressing rapidly. In recent years, the research and application of the electromagnetic–triboelectric hybridized nanogenerator (EMG-TENG) have made great progress. This review mainly focuses on the latest research development of EMG-TENG and elaborates on the principles, materials, structure, and applications of EMG-TENG. In this paper, the microscopic charge transfer mechanism of TENG is explained by the most primitive friction electrification phenomenon and electrostatic induction phenomenon. The commonly used materials for fabricating TENG and the selection and modification methods of the materials are introduced. According to the difference in structure, EMG-TENG is divided into two categories: vibratory EMG-TENG and rotating EMG-TENG. The summary explains the application of EMG-TENG, including the energy supply and self-powered system of small electronic devices, EMG-TENG as a sensor, and EMG-TENG in wearable devices. Finally, based on summarizing previous studies, the author puts forward new views on the development direction of EMG-TENG.

Printed Honeycomb-Structured Reduced Graphene Oxide Film for Efficient and Continuous Evaporation-Driven Electricity Generation from Salt Solution

Water-evaporation-induced electricity generation provides an ideal strategy to solve growing energy demand and supply power for self-powered systems because of its advantages of a highly spontaneous process, continuous power generation, and low cost. However, the reported evaporation-induced generators are limited to working only in deionized (DI) water, leading to a low output power. Herein, we utilize a modified multiple ion mode to demonstrate that the streaming potential can be optimized in microchannels filled with salt solution and achieve an enhanced evaporation-induced output power in salt solution by a generator based on honeycomb-structured reduced graphene oxide (rGO) film with abundant interconnected microchannels. This generator enables an around 2-fold open-circuit voltage (V_oc) and a 3.3-fold power density of 0.91 μW cm^-2 in 0.6 M NaCl solution compared to that in DI water. Experiments evidence that the honeycomb structure with abundant interconnected microchannels plays a key role in achieving high and stable output power in salt solution because of its large specific surface area and excellent ion-exchange capacity. Notably, it can work at all times of day and night for more than 240 h in natural seawater, delivering a stable V_oc of ∼0.83 V with a power density of 0.79 μW cm^-2. This study expands a working solution for water-evaporation-induced electricity generation from DI water to natural seawater, advancing a great step toward practical applications.

All-Fiber-Structured Triboelectric Nanogenerator via One-Pot Electrospinning for Self-Powered Wearable Sensors

With the rapid development in wearable electronics, self-powered devices have recently attracted tremendous attention to overcome the restriction of conventional power sources. In this regard, a simple, scalable, and one-pot electrospinning fabrication technique was utilized to construct an all-fiber-structured triboelectric nanogenerator (TENG). Ethyl cellulose was co-electrospun with polyamide 6 to serve as the triboelectric positive material, and a kind of strongly electronegative conductive material of MXene sheet was innovatively incorporated into poly(vinylidene fluoride) nanofiber to act as a triboelectric negative material. The assembled all-fiber TENG exhibited excellent durability and stability, as well as excellent output performance, which reached a peak power density of 290 mW/m² at a load resistance of 100 MΩ. More importantly, the TENG was capable of harvesting energy to power various light-emitting diodes (LEDs) and monitoring human movements as a self-powered sensor, providing a promising application prospect in wearable electronics.

Hybridized nanogenerators for effectively scavenging mechanical and solar energies

Solar and wind energy harvesting technology is increasingly an economical and efficient energy form and receives excellent support from government policies worldwide. Various functional and structural nanogenerators based on multi-effects named hybridized nanogenerators have been reported separately or simultaneously to effectively generate the wasted mechanical and solar energy in our daily life. We review the development of hybridized nanogenerators, including the working mechanism of solar and mechanical energies. Moreover, the classification of nanogenerators for scavenging mechanical and solar energies is discussed. The potential applications of hybridized nanogenerators are reviewed. Finally, the challenge and prospective of hybridized nanogenerators and the future explored improvements of output performance, stability, preparation, large-scale utilizing, and efficiency are discussed. The hybridized nanogenerator as the energy technology will be popularized in energy and self-powered sensor systems.

Air-gap embedded triboelectric nanogenerator via surface modification of non-contact layer using sandpapers

With the increased number of small electronics and demand for their energy source, renewable energy sources have received much attention. Above all, a triboelectric nanogenerator (TENG) based on the combination of contact electrification and electrostatic induction has been researched as a method of converting mechanical energy into electricity. In order to increase the electrical output of TENGs with raising the surface charge density, a lot of researchers have focused on the fabrication methods to employ micro-/nano-structures onto a contact surface of the TENG, but have been facing several issues regarding the degradation of the output performance from the iterative operation process. Hence, it is highly required to introduce an approach to enhancing the performance of TENG, while minimally degrading the output power during the long-term operation. In this paper, an air-gap embedded TENG (AE-TENG), which contains a microstructure on the non-contact surface by means of a sandpaper, is proposed. These small air-gaps between the spin-coated polydimethylsiloxane and the non-contact surface can significantly boost the total surface charge density of the dielectric layer. Thus, the electrical output performance of the AE-TENG is enhanced without any surface engineering on the contact surface. Furthermore, the effect of the air-gap induced surface charges on the electric potential is systematically analyzed by not only experimentally electrical outputs, but theoretical and computational modeling based on the V-Q-x relationship and simulation software tool. This air-gap induced triboelectric effect opens a new perspective of the development of electrical outputs by providing a structural/theoretical understanding for TENGs.

A Nonresonant Hybridized Electromagnetic-Triboelectric Nanogenerator for Irregular and Ultralow Frequency Blue Energy Harvesting

As a promising renewable energy source, it is a challenging task to obtain blue energy, which is irregular and has an ultralow frequency, due to the limitation of technology. Herein, a nonresonant hybridized electromagnetic-triboelectric nanogenerator was presented to efficiently obtain the ultralow frequency energy. The instrument adopted the flexible pendulum structure with a precise design and combined the working principle of electromagnetism and triboelectricity to realize the all-directional vibration energy acquisition successfully. The results confirmed that the triboelectric nanogenerator (TENG) had the potential to deliver the maximum power point of about 470 μW while the electromagnetic nanogenerator (EMG) can provide 523 mW at most. The conversion efficiency of energy of the system reached 48.48%, which exhibited a remarkable improvement by about 2.96 times, due to the elastic buffering effect of the TENG with the double helix structure. Furthermore, its ability to collect low frequency wave energy was successfully proven by a buoy in Jialing River. This woke provides an effective candidate to harvest irregular and ultralow frequency blue energy on a large scale.

Magnetic Force Enhanced Sustainability and Power of Cam-Based Triboelectric Nanogenerator

Since the first invention of triboelectric nanogenerators (TENGs) in 2012, many mechanical systems have been applied to operate TENGs, but mechanical contact losses such as friction and noise are still big obstacles for improving their output performance and sustainability. Here, we report on a magnet-assembled cam-based TENG (MC-TENG), which has enhanced output power and sustainability by utilizing the non-contact repulsive force between the magnets. We investigate the theoretical and experimental dynamic behaviors of MC-TENGs according to the effects of the contact modes, contact and separation times, and contact forces (i.e., pushing and repulsive forces). We suggest an optimized arrangement of magnets for the highest output performance, in which the charging time of the capacitor was 2.59 times faster than in a mechanical cam-based TENG (C-TENG). Finally, we design and demonstrate a MC-TENG-based windmill system to effectively harvest low-speed wind energy, ~4 m/s, which produces very low torque. Thus, it is expected that our frictionless MC-TENG system will provide a sustainable solution for effectively harvesting a broadband of wasted mechanical energies.

Triboelectric Nanogenerators and Hybridized Systems for Enabling Next-Generation IoT Applications

In the past few years, triboelectric nanogenerator-based (TENG-based) hybrid generators and systems have experienced a widespread and flourishing development, ranging among almost every aspect of our lives, e.g., from industry to consumer, outdoor to indoor, and wearable to implantable applications. Although TENG technology has been extensively investigated for mechanical energy harvesting, most developed TENGs still have limitations of small output current, unstable power generation, and low energy utilization rate of multisource energies. To harvest the ubiquitous/coexisted energy forms including mechanical, thermal, and solar energy simultaneously, a promising direction is to integrate TENG with other transducing mechanisms, e.g., electromagnetic generator, piezoelectric nanogenerator, pyroelectric nanogenerator, thermoelectric generator, and solar cell, forming the hybrid generator for synergetic single-source and multisource energy harvesting. The resultant TENG-based hybrid generators utilizing integrated transducing mechanisms are able to compensate for the shortcomings of each mechanism and overcome the above limitations, toward achieving a maximum, reliable, and stable output generation. Hence, in this review, we systematically introduce the key technologies of the TENG-based hybrid generators and hybridized systems, in the aspects of operation principles, structure designs, optimization strategies, power management, and system integration. The recent progress of TENG-based hybrid generators and hybridized systems for the outdoor, indoor, wearable, and implantable applications is also provided. Lastly, we discuss our perspectives on the future development trend of hybrid generators and hybridized systems in environmental monitoring, human activity sensation, human-machine interaction, smart home, healthcare, wearables, implants, robotics, Internet of things (IoT), and many other fields.

Hybridized Nanogenerators for Multifunctional Self-Powered Sensing: Principles, Prototypes, and Perspectives

Sensors are a key component of the Internet of Things (IoTs) to collect information of environments or objects. Considering the tremendous number and complex working conditions of sensors, multifunction and self-powered feathers are two basic requirements. Nanogenerators are a kind of devices based on the triboelectric, piezoelectric, or pyroelectric effects to harvest ambient energy and then converting to electricity. The hybridized nanogenerators that combined multiple effects in one device have great potential in multifunctional self-powered sensors because of the unique superiority such as generating electrical signals directly, responding to diverse stimuli, etc. This review aims at introducing the latest advancements of hybridized nanogenerators for multifunctional self-powered sensing. Firstly, the principles and sensor prototypes based on TENG are summarized. To avoid signal interference and energy insufficiently, the multifunctional self-powered sensors based on hybridized nanogenerators are reviewed. At last, the challenges and future development of multifunctional self-powered sensors have prospected.

Research progress of TiO2 photocathodic protection to metals in marine environment

Corrosion protection has become an important issue as the amount of infrastructure construction in marine environment increased. Photocathodic protection is a promising method to reduce the corrosion of metals, and titanium dioxide (TiO₂) is the most widely used photoanode. This review summarizes the progress in TiO₂ photogenerated protection in recent years. Different types of semiconductors, including sulfides, metals, metal oxides, polymers, and other materials, are used to design and modify TiO₂. The strategy to dramatically improve the efficiency of photoactivity is proposed, and the mechanism is investigated in detail. Characterization methods are also introduced, including morphology testing, light absorption, photoelectrochemistry, and protected metal observation. This review aims to provide a comprehensive overview of TiO₂ development and guide photocathodic protection.

Water Splitting: From Electrode to Green Energy System

Hydrogen (H2) production is a latent feasibility of renewable clean energy. The industrial H2 production is obtained from reforming of natural gas, which consumes a large amount of nonrenewable energy and simultaneously produces greenhouse gas carbon dioxide. Electrochemical water splitting is a promising approach for the H2 production, which is sustainable and pollution-free. Therefore, developing efficient and economic technologies for electrochemical water splitting has been an important goal for researchers around the world. The utilization of green energy systems to reduce overall energy consumption is more important for H2 production. Harvesting and converting energy from the environment by different green energy systems for water splitting can efficiently decrease the external power consumption. A variety of green energy systems for efficient producing H2, such as two-electrode electrolysis of water, water splitting driven by photoelectrode devices, solar cells, thermoelectric devices, triboelectric nanogenerator, pyroelectric device or electrochemical water-gas shift device, have been developed recently. In this review, some notable progress made in the different green energy cells for water splitting is discussed in detail. We hoped this review can guide people to pay more attention to the development of green energy system to generate pollution-free H2 energy, which will realize the whole process of H2 production with low cost, pollution-free and energy sustainability conversion.