Search Results (38)

Triboelectric nanogenerators (TENGs) are key technologies for the Internet of Things with energy harvesting. To improve energy conversion efficiency and convert mechanical energy into electrical energy, high charge density in TENGs plays a crucial role in the design of triboelectric materials and device structures. This paper proposes mechanisms and strategies to increase TENGs’ charge density through multi-charge storage layers. We also discuss the realization of higher charge densities through material and structure design. The implementation of novel charge storage strategies holds the potential for significant improvements in charge density. Full article

As a new technology for harvesting distributed energy, the triboelectric nanogenerator (TENG) has been widely used in harvesting wind energy. However, the wind-driven TENG (WD-TENG) faces the problems of high frictional resistance and low mechanical energy conversion efficiency. Here, based on optimizing the structure of the wind turbine, a rotational double-electrode-layer WD-TENG (DEL-WD-TENG) is developed. When the rotational speed is less than 400 round per minute (rpm), the dielectric triboelectric layer rubs with the inner electrode layer under its gravity; when the rotational speed is higher than 400 rpm, the dielectric triboelectric layer rubs with the outer electrode layer under the centrifugal force. The double-electrode-layer structure avoids the energy loss caused by other forces except gravity, centrifugal, and electrostatic adsorption, which improves the mechanical energy conversion efficiency and prolongs the working life of the DEL-WD-TENG. The conversion efficiency from mechanical energy to electricity of the DEL-WD-TENG can reach 10.3%. After 7 million cycles, the transferred charge of the DEL-WD-TENG is reduced by about 5.0%, and the mass loss of dielectric triboelectric layer is only 5.6%. The DEL-WD-TENG with low frictional resistance and high energy conversion efficiency has important application prospects in wind energy harvesting and self-powered sensing systems. Full article

Zinc oxide nanowires (ZnO NWs) have gained considerable attention in the field of piezoelectricity in the past two decades. However, the impact of growth-process conditions on their dimensions and polarity, as well as the piezoelectric properties, has not been fully explored, specifically when using pulsed-liquid injection metal–organic chemical vapor deposition (PLI-MOCVD). In this study, we investigate the influence of the O₂ gas and DEZn solution flow rates on the formation process of ZnO NWs and their related piezoelectric properties. While the length and diameter of ZnO NWs were varied by adjusting the flow-rate conditions through different growth regimes limited either by the O₂ gas or DEZn reactants, their polarity was consistently Zn-polar, as revealed by piezoresponse force microscopy. Moreover, the piezoelectric coefficient of ZnO NWs exhibits a strong correlation with their length and diameter. The highest mean piezoelectric coefficient of 3.7 pm/V was measured on the ZnO NW array with the length above 800 nm and the diameter below 65 nm. These results demonstrate the ability of the PLI-MOCVD system to modify the dimensions of ZnO NWs, as well as their piezoelectric properties. Full article

Addressing the increasing development of IoT networks and the associated energy requirements, rotating triboelectric nanogenerators (R-TENGs) are proving to be strong candidates in the field of energy harvesting, as well as to that of self-powered devices and autonomous sensors. In this work, we review the theoretical framework surrounding the operating principles and key design parameters of R-TENGs, while also associating them with their output characteristics. Furthermore, we present an overview of the core designs used by the research community in energy harvesting applications, as well as variations of these designs along with explicit solutions for the engineering and optimization of the electrical output of R-TENGs. Last but not least, a comprehensive survey of the potential applications of R-TENGs outside the energy harvesting scope is provided, showcasing the working principles of the various designs and the benefits they confer for each specific scenario. Full article

Indoor organic photovoltaics (IOPVs) have attained considerable research attention as a power source for a low-power consumption self-sustainable electronic device for Internet of Things (IoT) applications. This study aims to develop an efficient cathode interfacial layer (CIL) based on a polyethyleneimine (PEIE) derivative, processed at room temperature, for the advancement of non-fullerene acceptor (NFA)-based IOPVs. Using a simple chemical reaction between polyethyleneimine and cobalt (II) chloride, we developed a 3D network-structured CIL. Through quaternary ammonium salts and chelating, metal ions act as mediators and induce metal-ion doping. An inverted device architecture with wide-bandgap and low-bandgap photo-absorber layer is utilized to understand the role of CILs under standard 1 sun and low-light or indoor light illuminations. The IOPV devices with modified CIL (Co-PEIE) having PBDB-T: IT-M and PBDB-T-2F: BTP-4F photo-absorber layers demonstrate a power conversion efficiency of 22.60% and 18.34% under 1000 lux LED lamp (2700 K) illumination conditions, respectively, whereas the IOPV devices with pristine PEIE CIL realized a poor device performance of 18.31% and 14.32% for the PBDB-T: IT-M and PBDB-T-2F: BTP-4F active layers, respectively. The poor device performance of PEIE interlayer-based IOPV under low-light conditions is the result of the significantly high leakage current and low shunt resistance that directly affect the open-circuit voltage (V_OC) and fill factor (FF). Therefore, the adjustable energy barrier and notably low leakage current exhibited by the Co-PEIE CIL have a crucial impact on mitigating losses in V_OC and FF when operating under low-light conditions. Full article

Lithium-ion batteries (LIBs) dominate the market of rechargeable power sources. To meet the increasing market demands, technology updates focus on advanced battery materials, especially cathodes, the most important component in LIBs. In this review, we provide an overview of the development of materials and processing technologies for cathodes from both academic and industrial perspectives. We briefly compared the fundamentals of cathode materials based on intercalation and conversion chemistries. We then discussed the processing of cathodes, with specific focuses on the mechanisms of a drying process and the role of the binders. Several key parameters for the development of thick electrodes were critically assessed, which may offer insights into the design of next-generation batteries. Full article

As wearable devices continue to be updated and iterated, there is an increasing demand for energy supplies that are small, portable and capable of working continuously for extended periods of time. Here, a hybrid triboelectric-electromagnetic nanogenerator (HNG) based on a biomechanical energy harvester is demonstrated. The HNG is designed to be worn on the wrist according to the curve of the wearer’s arm swing. During the swinging of the arm, the magnet covered by the PTFE film will move relative to the curved cavity of the HNG and take on a negative charge by rubbing against the inner wall of the Cu coated cavity, resulting in a change in the potential difference between the two copper electrodes on the inner wall of the curved cavity. The movement of the magnet causes the magnetic flux of the three pairs of coils on both sides of the arc track to change to produce the induced electric potential, which converts the mechanical energy generated by the arm swing into electrical energy. After the rational design, the HNG is integrated into a small size device to achieve the collection of biomechanical energy. Several experiments were conducted to verify the HNG’s usability. Experiments show that the HNG takes 90 s to charge from 0 V to 1.2 V for a 1000 μF capacitor. In addition, the HNG can light up 23 LEDs simultaneously and provide a continuous supply of energy to portable electronic devices, such as temperature sensors and electronic watches after the capacitor has stored the energy. Furthermore, the HNG is experimentally verified by volunteers wearing the HNG to achieve continuous and stable output in all three states of slow swing, fast swing and running swing. This work not only provides a useful reference for human biomechanical energy harvesting, but can also provide a continuous, clean source of energy for wearable devices. Full article

Facing the energy consumption of a huge number of distributed wireless Internet of Things (IoT) sensor nodes, scavenging energy from the ambient environment to power these devices is considered to be a promising method. Moreover, abundant energy sources of various types are widely distributed in the surrounding environment, which can be converted into electrical energy by micro-nano energy harvesters based on different mechanisms. In this review paper, we briefly introduce the development of different energy harvesters according to the classification of target energy sources, including microscale and nanoscale energy harvesters for vibrational energy sources, microscale energy harvesters for non-vibrational energy sources, and micro-nano energy harvesters for hybrid energy sources. Furthermore, the current advances and future prospects of the applications of micro-nano energy harvesters in event-based IoT systems and self-sustained systems are discussed. Full article

Anthropogenetic environmental deterioration and climate change caused by energy production and consumption pose a significant threat to the future of humanity. Renewable, environmentally friendly, and cost-effective energy sources are becoming increasingly important for addressing future energy demands. Mechanical power is the most common type of external energy that can be converted into useful electric power. Because of its strong electromechanical coupling ability, the piezoelectric mechanism is a far more successful technique for converting mechanics energy to electrical energy when compared to electrostatic, electromagnetic, and triboelectric transduction systems. Currently, the scientific community has maintained a strong interest in piezoelectric micro-power generators because of their great potential for powering a sensor unit in the distributed network nodes. A national network usually has a large mass of sensor units distributed in each city, and a self-powered sensor network is eagerly required. This paper presents a comprehensive review of the development of piezoelectric micro-power generators. The fundamentals of piezoelectric energy conversion, including operational modes and working mechanisms, are introduced. Current research progress in piezoelectric materials including zinc oxide, ceramics, single crystals, organics, composite, bio-inspired and foam materials are reviewed. Piezoelectric energy harvesting at the nano- and microscales, and its applications in a variety of fields such as wind, liquid flow, body movement, implantable and sensing devices are discussed. Finally, the future development of multi-field coupled, hybrid piezoelectric micropower generators and their potential applications are discussed. Full article

Metal–support interaction (MSI) is considered a key effect of electronic and geometric structures of catalysts on tuning catalytic performance. The oxygen evolution reaction (OER) is a crucial process during energy conversion and storage. However, the OER process requires the help of noble metal catalysts to reduce the reaction overpotential, enhance reactivity with intermediates, and maintain good operating stability. Carbon–supported metal catalysts have been considered candidates for noble metal catalysts for OER. MSI occurs at the interface of carbon supports and metals, affecting the catalytic performance through electronic and geometric modulation. MSI can influence the catalytic performance and change reaction pathways from charge redistribution, electron transfer, chemical coordination and bonding, and steric effect. Connecting MSI effects with the OER mechanism can provide theoretical guidance and a practical approach to the design of efficient catalysts, including the modulation of particle size, morphology, heteroatom doping, defect engineering, and coordination atom and number. Advantage can be taken of MSI modulation between metal compounds and carbon supports to provide guidance for catalyst design. Full article

Zinc–air batteries are promising candidates as stationary power sources because of their high specific energy density, high volumetric energy density, environmental friendliness, and low cost. The oxygen-related reactions at the air electrode are kinetically slow; thus, the air electrode integrated with an oxygen electrocatalyst is the most critical component, and inevitably determines the performance of a Zn–air battery. The aim of this paper was to document progress in researching bifunctional catalysts for Zn–air batteries. The catalysts are divided into several categories: noble metal, metal nanoparticle (single and bimetallic), multicomponent nanoparticle, metal chalcogenide, metal oxide, layered double hydroxide, and non-metal materials. Finally, the battery performance is compared and discussed. Full article

Contact electrification exists everywhere and between every phase of matter. However, its mechanism still remains to be studied. The recent triboelectric nanogenerator serves as a probe and provides some new clues about the mechanism present in solid–solid, solid–liquid, and liquid–liquid contact electrification. The gas–solid model still remains to be exploited. Here, we investigated the contact electrification between gases and solids based on the single-electrode triboelectric nanogenerator. Our work shows that the amount of transferred charges between gas and solid particles increases with surface area, movement distance, and initial charges of particle increase. Furthermore, we find that the initial charges on the particle surface can attract more polar molecules and enhance gas collisions. Since ions in gas–solid contact are rare, we speculate that gas–solid contact electrification is mainly based on electron transfer. Further, we propose a theoretical model of gas–solid contact electrification involving the gas collision model and initial charges of the particle. Our study may have great significance to the gas–solid interface chemistry. Full article

Nanogenerators are a recently emerging technology which is able to cost-effectively harvest energy from renewable and clean energy sources at the micro/nano-scale. Their applications in the field of self-powered sensing systems and portable power supplying devices have been increasing in recent years. Wearable and implantable electromechanical/electrochemical transducers for energy harvesting represent a novel alternative to chemical batteries for low-power devices and to exploit the energy conveyed by human biomechanics. The human heart, in particular, is a compelling in vivo source of continuous biomechanical energy and is a natural battery which can power implantable or wearable medical devices. This review describes the recent advances in cardiac wearable/implantable soft and flexible devices and nanogenerators for energy harvesting (piezoelectric nanogenerators, triboelectric nanogenerators, biofuel cells, solar cells, etc.), as well as cardiovascular implantable electronic devices in a more general sense, as components of more complex self-sustainable bioelectronic systems for controlling irregular heartbeats or for interventional therapy for cardiac diseases. The main types of soft heart energy harvesters (HEHs) and heart bioelectronic systems (HBSs) are covered and classified, with a detailed presentation of state-of-the-art devices, and the advances in terms of materials choice, chemical functionalization, and design engineering are highlighted. In vivo bioelectronic cardiac interfaces are outlined as well as soft devices for in vitro cardiac models (patch and organoids). Cutting-edge 3D/4D bioprinting techniques of cardiac tissue are also mentioned. The technical challenges for the practical application and commercialization of soft HBSs are discussed at the end of this paper. Full article

In the era of the Internet of Things, various electronics play an important role in information interaction, in which the power supply is an urgent problem to be solved. Triboelectric nanogenerator (TENG) is an emerging mechanical energy harvesting technology that can serve as a power source for electronics, which is developing towards high performance, miniaturization and integration. Herein, the advanced micro-nano manufacturing technologies are systematically reviewed for TENGs. First, film preparation such as physical vapor deposition, chemical vapor deposition, electrochemical deposition, electrospinning and screen printing for triboelectric layers are introduced and discussed. Then, surface processing, such as soft lithography, laser ablation, inductively coupled plasma and nanoimprint for micro-nano structures on the surface of triboelectric layers are also introduced and discussed. In addition, micro-electromechanical system fabrication for TENG devices such as acoustic and vibration sensors, is introduced, and their current challenges are analyzed. Finally, the challenges of the advanced micro-nano manufacturing technologies for the TENGs are systematically summarized, and further development is prospected. Full article