Low-frequency Mechanical Energy Research Articles

Robust maglev hybrid nanogenerator with an airflow-based motion conversion mechanism for exploiting low-frequency mechanical energy

Triboelectric nanogenerator (TENG) has been widely recognized as an efficient technology for exploiting low-frequency (LF) mechanical energy, but the sparse outputs at low frequencies and insufficient durability at high frequencies hinder its extensive applications. Herein, a robust and high-output triboelectric-electromagnetic hybrid nanogenerator (TEHG) is proposed with an ingenious airflow-based motion conversion mechanism (AMCM) and a well-designed maglev mechanism. Distinct from conventional MCMs generally constructed with complicated rigid components, the AMCM transforms LF-motions to fast rotation through a flexible bladder and air tubes. Enabled by the AMCM, the TENG part can provide power density up to 274 mW/kg at an output frequency 70 times higher than the excitation frequency. The normalized voltage of the TENG part stabilizes at 84.1 % after 8-day durability test with the specially designed maglev mechanism, which allows the TENG part to operate in intermittent (sliding) contact state under slow rotation to replenish tribo-charges with minor material wear whereas switch to non-contact state without material wear under fast rotation. By combining the complementary output characteristics of triboelectric and electromagnetic technologies, a storage capacitor can be charged to a higher voltage level within remarkably reduced time. The practical feasibility of the AMCM-TEHG was verified by arranging it on a footpath to charge a wireless digital camera and a wireless sensing system. This study provides a promising strategy for multiplying the output frequencies as well as increasing the durability of TEHGs for efficiently exploiting LF-mechanical energy.

A Comprehensive Review of Strategies toward Efficient Flexible Piezoelectric Polymer Composites Based on BaTiO3 for Next-Generation Energy Harvesting

The increasing need for wearable and portable electronics and the necessity to provide a continuous power supply to these electronics have shifted the focus of scientists toward harvesting energy from ambient sources. Harvesting energy from ambient sources, including solar, wind, and mechanical energies, is a solution to meet rising energy demands. Furthermore, adopting lightweight power source technologies is becoming more decisive in choosing renewable energy technologies to power novel electronic devices. In this regard, piezoelectric nanogenerators (PENGs) based on polymer composites that can convert discrete and low-frequency irregular mechanical energy from their surrounding environment into electricity have attracted keen attention and made considerable progress. This review highlights the latest advancements in this technology. First, the working mechanism of piezoelectricity and the different piezoelectric materials will be detailed. In particular, the focus will be on polymer composites filled with lead-free BaTiO3 piezoceramics to provide environmentally friendly technology. The next section will discuss the strategies adopted to enhance the performance of BaTiO3-based polymer composites. Finally, the potential applications of the developed PENGs will be presented, and the novel trends in the direction of the improvement of PENGs will be detailed.

High-performance triboelectric nanogenerator based on biocompatible electrospun polycaprolactone nanofiber and counter convex PDMS for low-frequency mechanical energy harvesting

High-performance triboelectric nanogenerator based on biocompatible electrospun polycaprolactone nanofiber and counter convex PDMS for low-frequency mechanical energy harvesting

Construction of small size and high output triboelectric nanogenerator by multi-layer-stacking and charge excitation

Abstract The triboelectric nanogenerator (TENG) has been considered a low-frequency mechanical energy collection and conversion device in the modern era. The reasonable stack structure of TENG is an effective method to boost its electric output performance within a limited space. Nevertheless, relying solely on the stacking structure, the TENG is unable to produce excessive output due to the low contact electrification capability of its materials. Hence, there are still significant challenges in enhancing the output performance of stacked TENGs. We propose a multi-layer-stack TENG (M-TENG) with two zigzag-shaped (Z-shaped) multilayer units interleaving and stacking with each other, which enormously enlarges the effective utilization area. Furthermore, a voltage multiplier circuit (VMC) incorporating a Zener diode allows the transfer charge to approach the critical threshold and maintain a stable output. The transfer charge and current of M-TENG integrated with a VMC can reach 1.52 μC and 86 μA, respectively, with the maximum output of the TENG being 8.65 mW (5 MΩ). To prove it as a self-power device, M-TENG excited by a VMC is employed to power 912 light-emitting diodes (LEDs) and three temperature and humidity sensors with a power management circuit (PMC), respectively. This work offers a new method for optimizing stacking-layer TENG electric output performance in a narrow space.

A flexible silicone tube arrangement structure triboelectric nanogenerator for tennis training monitoring

As the Internet of Things (IoTs) rapidly gain popularity, the demand for self-powered flexible electronic devices is continuously rising, particularly in the intelligent sports field. Hence, we introduced a silicone tube-based triboelectric nanogenerator (ST-TENG) designed for mechanical energy harvesting and tennis training monitoring. The ST-TENG, with its innovative tubular structure, effectively harvests low-frequency mechanical energy and converts it into electrical energy. At a working frequency of 6 Hz, the ST-TENG achieved an open-circuit voltage (Voc) of 122.51 V, a short-circuit current (Isc) of 15.05 µA, and a transfer charge (Qsc) of 33.74 nC. The ST-TENG demonstrates high sensitivity and accuracy in capturing subtle motion details, providing comprehensive data on various aspects of an athlete’s performance. The ST-TENG demonstrated excellent responsiveness to pressure and bending, making it suitable for real-time motion monitoring in tennis. Integrating the ST-TENG into the clothing and equipment of tennis players effectively monitored wrist, waist, and foot movements, providing detailed motion data. This research paves the way for developing highly efficient, self-powered wearable sensors that can significantly enhance the accuracy and sustainability of real-time athletic training monitoring.

Biodegradable flexible triboelectric nanogenerator for winter sports monitoring

With the energy crisis and environmental pollution becoming a growing concern worldwide, the development of clean and renewable energy from the environment has become an imperative for human survival and development. However, the equipment used to harvest clean renewable energy is large, subject to environmental impacts and regional differences (such as wind, solar and tidal energy). In this study, a biodegradable eggshell membrane triboelectric nanogenerator (EM-TENG) is introduced for the purpose of harvesting low-frequency mechanical energy. A Wireless Intelligent Motion Monitoring System (WIMMS) has been created using EM-TENG. It includes a Bluetooth sensor terminal and an intelligent processing terminal for digital signal reception on a host computer. The EM-TENG can be attached to knee and ankle joints to monitor posture. Therefore, for real-time monitoring of joint and kinetic chain changes during land training of ice dance athletes, the intelligent ice dance land training aid system is important. As a wearable motion monitoring sensor, EM-TENGs application in intelligent motion monitoring, intelligent wearable devices and big data analytics is being promoted.

High-sensitivity wearable multi-signal sensor based on self-powered MXene hydrogels

Developing high-performance wearable sensors with multi-sensing capabilities for different signals such as temperature, human motion and physiological signals remains a challenge. In this report, a novel catechol functionalization of PVA-CA/Poly(N-acryloyl glycinamide)/MXene hydrogels(PcNA-M) was fabricated by combining the thermosensitivity of Poly(N-acryloyl glycinamide)(PNAGA) hydrogel and the self-powered properties of the catechol functionalization of PVA(Pc)/MXene hydrogels. The mixing ratio of PNAGA and Pc was adjusted to impart the resulting PcNA-M with good tensile, compression, rebound properties, rapid self-healing and temperature sensing properties. In addition, the conductivity of the hydrogel was found to have contributions from ionic and electrical conductivity. To produce different forms of electrical signals for different signal sources, the PcNA-M sensor was utilized to monitor the resistive and voltage signals during body movements, switching temperature and handwriting motion. The PcNA-M sensor exhibits high sensitivity, identifiability, and reliability in applications of self-powered wearable sensors, and demonstrates great prospects in the field of low-frequency mechanical energy harvesting. This study opens a new possibility for wearable self-powered multi-signal sensors to monitor different signals related to human motion.

Electrostatic-driven self-assembled chitin nanocrystals (ChNCs)/MXene films for triboelectric nanogenerator

With the rapid development of smart wearable electronics, self-powered devices are urgently needed to overcome the limitations of conventional power sources. The single electrode triboelectric nanogenerator (TENG) attracts much attention owing to its simple fabrication, carrying convenience, and easy use as a power source for wearable electronic devices. Herein, a flexible, responsive, and multifunctional single electrode TENG based on renewable chitin nanocrystals (ChNCs) and MXene composite film (CM-TENG) is developed. ChNCs act as interfacial adhesives to facilitate the assembly of the MXene nanosheets, which significantly improves the composite film's mechanical properties and electrical conductivity. Positively charged ChNCs neutralize the negative charges of MXene nanosheet surfaces, enabling the composite film to rapidly transfer charges during the electrostatic induction process. The output performance of the CM-TENG can achieve 99.5 mW m−2 power density so it can be utilized for self-powered strain and tactile sensors. This work presents a new strategy for constructing stable and flexible power sources and self-powered sensors via electrostatic-driven self-assembled of ChNCs and MXene, which shows promising application in low frequency mechanical energy harvesting and self-powered wearable electronics.

Orange peel-like triboelectric nanogenerators with multiscale micro-nano structure for energy harvesting and touch sensing applications

With the continuous advancements in technology, triboelectric nanogenerators (TENGs) have gained significant traction as efficient harnessers of low-frequency mechanical energy to meet the escalating energy demands. Notably, employing solid polymer electrolyte (SPE) as a contact layer or optimizing the microstructural composition of the surface material represents a prevalent strategy for augmenting the output performance of TENGs. However, the fabrication of numerous microstructures poses significant challenges, particularly in terms of incorporating environmentally harmful materials. Moreover, the utilization of triboelectric nanogenerators is further constrained by limitations associated with electrode materials. Although various techniques are available for producing transparent and stretchable electrodes for such generators, these procedures can be intricate and necessitate the use of hazardous chemicals. In this study, we exploit Poly(vinyl alcohol) (PVA) and natural bacterial cellulose (BC) nanofibers to fabricate contact layers with OP structures characterized by micron-scale domes and nanoscale microcracks. The electrodes were fabricated using BC hydrogel and ionic liquids(ILs). Under the action of hydrogen bond topological network, a multi-scale structure is formed comprising of a molecular-scale interlacing network of hydrogen bonds and a nanoscale fiber skeleton, which synergistically confer the ionic gel with remarkable tensile strength and high ionic conductivity (up to 83.51mS/cm). The resulting OP-TENG exhibited an output open-circuit voltage of 280 V, a short-circuit current of 24μA, and a maximum power density of 5.6 W m−2, enabling it to illuminate up to 303 LEDs. A SSEM-TENG was devised by stacking two single electrode mode TENGs on top of each other using a single wire. This innovative design holds great potential for applications in wearable motion monitoring, high-precision writing stroke recognition, and low-frequency mechanical energy harvesting.

Enhancing PDMS-based triboelectric nanogenerator output by optimizing the microstructure and dielectric constant

Triboelectric nanogenerators possess the capability to convert low-frequency mechanical energy into electrical energy, thereby attracting significant attention due to their reliable performance, light weight nature, and simplistic structure.

(Invited) bionic Composite Films for Biomechanical Energy Harvesting and Self-Powered Sensing Applications

Triboelectric nanogenerators (TENGs) are novel and sustainable devices for harvesting ambient energy for many technological-based applications. However, extreme friction wear of triboelectric layers severely limits their long-term electrical stability and mechanical reliability, restricting the applicability of TENGs for low-frequency mechanical energy harvesting. Herein, we report novel bionic composite (BC) films, inspired by the structures and compositions of bioskins, as wear-resistant triboelectric contact layers for TENGs. We demonstrated that the proposed BC films has superior charge transfer capability, high wear resistance, and maintained long-term stable outputs compared to commercially available films. These works provide an effective strategy to reduce material abrasion by exploiting unique characteristics of the bionic materials, and lays a foundation for effective environmental energy harvesting toward practical applications. Figure 1

Ultrahigh Piezocatalytic Performance of Perovskite Ferroelectric Powder via Oxygen Vacancy Engineering.

Piezocatalysis has increasingly gained prominence due to its enormous potential for addressing energy shortages and environmental pollution issues. Nonetheless, the low piezocatalytic activity of state-of-the-art materials seriously inhibits the practical applications of piezocatalysis. Here, itis proposed to greatly enhance the piezocatalytic activity for a perovskite ferroelectric, i.e., Sm-doped 0.68Pb(Mg1/3 Nb2/3 )-0.32PbTiO3 (Sm-PMN-PT, a solid solution with ultrahigh piezoelectricity), by introducing oxygen vacancies (OVs). The results show that the presence of OVs promotes the production of reactive oxygen species while enhancing the adsorption and activation of organic pollutants to improve piezocatalytic performance. The OV-Sm-PMN-PT is found to possess a superior piezocatalytic degradation rate constant of 0.073 min-1 under ultrasonic vibration, which is ≈4.9 times higher than that of pristine Sm-PMN-PT. Furthermore, the OV-Sm-PMN-PT can efficiently remove RhB under 400rpm stirring, making it a promising candidate for water purification using low-frequency mechanical energy from nature. This research sheds light on the design of piezocatalytic materials via defect engineering.

Impact of external excitations on blinking enhanced synchronization in bistable vibrational energy harvesters.

Vibrational energy harvesters are capable of converting low-frequency broad-band mechanical energy into electrical power and can be used in implantable medical devices and wireless sensors. With the use of such energy harvesters, it is feasible to generate continuous power that is more reliable and cost-effective. According to previous findings, the energy harvester can offer rich complex dynamics, one of which is obtaining the synchronization behavior, which is intriguing to achieve desirable power from energy harvesters. Therefore, we consider bistable energy harvesters with periodic and quasiperiodic excitations to investigate synchronization. Specifically, we introduce blinking into the coupling function to check whether it improves the synchronization. Interestingly, we discover that raising the normalized proportion of blinking can initiate synchronization behaviors even with lower optimal coupling strength than the absence of blinking in the coupling (i.e., continuous coupling). The existence of synchronization behaviors is confirmed by finding the largest Lyapunov exponents. In addition, the results show that the optimal coupling strength needed to achieve synchronization for quasiperiodic excitations is smaller than that for periodic excitations.

Revisiting lead magnesium niobate-lead titanate piezoceramics for low-frequency mechanical vibration-based energy harvesting

Revisiting lead magnesium niobate-lead titanate piezoceramics for low-frequency mechanical vibration-based energy harvesting

Laser-Induced Graphene Formation on Chitosan Derivatives toward Ecofriendly Electronics

Laser-induced graphene (LIG) has aroused a wide range of research interests ranging from micro-nano energy devices to the Internet of Things (IoT). Nevertheless, the non-degradability of most-used synthetic polymer carbon sources poses a serious threat to the environment. In this work, ecofriendly chitosan-based derivatives, including carboxymethyl chitosan (CMCS), chitosan oligosaccharide, and chitosan hydrochloride, are successfully converted into LIGs for the first time via a convenient one-step CO2 laser engraving at ambient air. The obtained LIGs are characterized by a three-dimensional hierarchical porous structure and exhibit good sheet conductivity. The consecutive carbonization and graphitization mechanism of target precursors induced by laser heat accumulation is also deeply discussed. Besides, based on a mechanically reliable LIG/CMCS composite film and tribo-negative acrylic/polyimide anti-layers, two contact-separation mode triboelectric nanogenerators are built and their power densities range from 1.44 to 2.48 mW cm–2. These devices with long cycle life can be used for low-frequency mechanical energy harvesting and commercial capacitance charging, which could be potentially applied in the wireless sensor network nodes. Such a family of chitosan derivatives paves a new route for LIG synthesis and provides new ideas for ecofriendly LIG electronics.

Enhancing the Performance of Triboelectric Generator: A Novel Approach Using Solid-Liquid Interface-Treated Foam and Metal Contacts.

This work introduces a novel approach for enhancing the performance of a triboelectric generator (TEG) by using a solid-liquid interface-treated foam (SLITF) as its active layer, combined with two metal contacts of different work functions. SLITF is made by absorbing water into a cellulose foam, which enables charges generated by friction energy during the sliding motion to be separated and transferred through the conductive path formed by the hydrogen-bonded network of water molecules. Unlike traditional TEGs, the SLITF-TEG demonstrates an impressive current density of 3.57 A/m2 and can harvest electric power up to 0.174 W/m2 with an induced voltage of approximately 0.55 V. The device generates a direct current in the external circuit, eliminating the limitations of low current density and alternating current found in traditional TEGs. By connecting six-unit cells of SLITF-TEG in series and parallel, the peak voltage and current can be increased up to 3.2 V and 12.5 mA, respectively. Furthermore, the SLITF-TEG has the potential to serve as a self-powered vibration sensor with high accuracy (R2 = 0.99). The findings demonstrate the significant potential of the SLITF-TEG approach for efficiently harvesting low-frequency mechanical energy from the natural environment, with broad implications for a range of applications.

Research Progress in Intelligent Exercise Monitoring Based on Triboelectric Nanogenerator

The coming of the 5G era in the Internet of Things (IoT) opens progress in cross-sectoral research in multiple disciplines. All physiological indicators of the human body are collected through sensors to provide new ideas for developing innovative sports, wearable devices, and modern intelligent venues for IoT. Conventional sensors require an external power source and have a limited lifespan and maintenance cost. Triboelectric nanogenerators (TENG), a new self-powered sensing technology that collects mechanical energy from bodily motions, can break through these limitations and be used in intelligent sports applications. Firstly, TENG can capture kinematic, biochemical, electrophysiological, and tissue dynamics information from the human body. Secondly, the low-frequency mechanical energy of the human body is not only physiological information but can also be used to power microelectronic devices to transmit big data in sports. In conclusion, we discuss TENG-based wearable sensing systems’ challenges and future opportunities.

Enhanced piezo-catalytic H2O2 production over Bi0.5Na0.5TiO3 via piezoelectricity enhancement and surface engineering

The piezo-catalytic hydrogen peroxide (H2O2) production is a promising alternative to traditional anthraquinone oxidation process, but it remains a challenging task. The low conversion efficiency of mechanical energy and the limitedsurface-active sites are the challengings for improving reaction efficiency. Moreover, piezo-catalysts are difficult to prepare in large quantities, limiting the industrial application. To address this issue, this study utilized piezoelectricity enhancement and surface engineering to regulate the Bi0.5Na0.5TiO3 (BNT) for piezo-catalytic H2O2 production. We successfully synthesized an efficient and stable piezo-catalyst, Ag-loaded Bi0.5Na0.5TiO3-AgNbO3 solid solution (Ag/BNT-AN), that was applied to two-channel H2O2 production. The piezo-catalytic activity of Ag/BNT-AN piezo-catalyst was greatly improved through joint regulation of enhancing piezoelectricity by Ag and Nb co-substitution, as well as promoting O2 reduction and H2O oxidation reactions by surface modification with Ag nanoparticals and hydroxyl groups. The optimal Ag/BNT-AN piezo-catalyst displayed H2O2 production rates of 469 µmol g−1 h−1 under ultrasonic vibration, which was 13 times higher than pure BNT. Additionally, the study found that H2O2 could also be synthesized when the catalyst was subjected to simple stirring as mechanical stress, indicating the potential of Ag/BNT-AN to harness low-frequency mechanical energy. This work provides an effective strategy for regulating piezo-catalysts and presents a catalyst design paradigm at the kilogram level.

Broadband and Multi-Cylinder-Based Triboelectric Nanogenerators for Mechanical Energy Harvesting with High Space Utilization.

The development and utilization of new energy sources is an effective means of addressing the limits of traditional fossil energy resources and the problem of environmental pollution. Triboelectric nanogenerators (TENG) show great potential for applications in harvesting low-frequency mechanical energy from the environment. Here, we propose a multi-cylinder-based triboelectric nanogenerator (MC-TENG) with broadband and high space utilization for harvesting mechanical energy from the environment. The structure consisted of two TENG units (TENG I and TENG II) assembled by a central shaft. Both an internal rotor and an external stator were included in each TENG unit, operating in oscillating and freestanding layer mode. On one hand, the resonant frequencies of the masses in the two TENG units were different at the maximum angle of oscillation, allowing for energy harvesting in a broadband range (2.25-4 Hz). On the other hand, the internal space of TENG II was fully utilized, and the maximum peak power of the two TENG units connected in parallel reached 23.55 mW. In contrast, the peak power density reached 31.23 Wm-3, significantly higher than that of a single TENG unit. In the demonstration, the MC-TENG could power 1000 LEDs, a thermometer/hygrometer, and a calculator continuously. Therefore, the MC-TENG will have excellent application in the field of blue energy harvesting in the future.

The sealed bionic fishtail-structured TENG based on anticorrosive paint for ocean sensor systems

Triboelectric nanogenerators (TENGs) have attracted considerable research attention because of there ability to collect low-frequency mechanical energy. The sealed bionic fishtail-structured TENG (SBF-TENG) based on anticorrosive paint is presented for the first time in this paper because of its good maneuverability, stability and mechanical characteristics for harvesting blue energy. Meanwhile, the material characteristics of the SBF-TENG are systematically studied and engineered for optimizing triboelectric power generation, collecting the wave energy in the environment. The salinity of the ocean or solution can be sensitively detected by The SBF-TENG through the collection of ocean energy. Furthermore, the service life of metals in the ocean or solution can be increased through the cathodic protection system constructed by the SBF-TENG. This work provides a paradigm of combining TENGs with the biomimetic underwater robot, and it is of great importance for the application of TENGs in the field of metal cathodic protection and ocean sensor systems.