Nanogenerator Research Articles

Multieffect Coupled Nanogenerators.

With the advent of diverse electronics, the available energy may be light, thermal, and mechanical energies. Multieffect coupled nanogenerators (NGs) exhibit strong ability to harvest ambient energy by integrating various effects comprising piezoelectricity, pyroelectricity, thermoelectricity, optoelectricity, and triboelectricity into a standalone device. Interaction of multitype effects can promote energy harvesting and conversion by modulating charge carriers' behaviour. Multieffect coupled NGs stand for a vital group of energy harvesters, supporting the advances of an electronic device and promoting the resolution of energy crisis. The matchless versatility and high reliability of multieffect coupled NGs make them main candidates for integration in complicated arrays of the electronic device. Multieffect coupled NGs can also be employed as a variety of self-powered sensors due to their rapid response, high accuracy, and high responsivity. This article reviews the latest achievements of multieffect coupled NGs. Fundamentals mainly including basic theory and materials of interest are covered. Advanced device design and output characteristics are introduced. Potential applications are described, and future development is discussed.

Nanogenerator-Based Self-Powered Sensors for Wearable and Implantable Electronics.

Wearable and implantable electronics (WIEs) are more and more important and attractive to the public, and they have had positive influences on all aspects of our lives. As a bridge between wearable electronics and their surrounding environment and users, sensors are core components of WIEs and determine the implementation of their many functions. Although the existing sensor technology has evolved to a very advanced level with the rapid progress of advanced materials and nanotechnology, most of them still need external power supply, like batteries, which could cause problems that are difficult to track, recycle, and miniaturize, as well as possible environmental pollution and health hazards. In the past decades, based upon piezoelectric, pyroelectric, and triboelectric effect, various kinds of nanogenerators (NGs) were proposed which are capable of responding to a variety of mechanical movements, such as breeze, body drive, muscle stretch, sound/ultrasound, noise, mechanical vibration, and blood flow, and they had been widely used as self-powered sensors and micro-nanoenergy and blue energy harvesters. This review focuses on the applications of self-powered generators as implantable and wearable sensors in health monitoring, biosensor, human-computer interaction, and other fields. The existing problems and future prospects are also discussed.

Self-Powered Smart Insole for Monitoring Human Gait Signals.

With the rapid development of low-power consumption wireless sensors and wearable electronics, harvesting energy from human motion to enable self-powered sensing is becoming desirable. Herein, a pair of smart insoles integrated with piezoelectric poly(vinylidene fluoride) (PVDF) nanogenerators (NGs) are fabricated to simultaneously harvest energy from human motion and monitor human gait signals. Multi-target magnetron sputtering technology is applied to form the aluminum electrode layers on the surface of the PVDF film and the self-powered insoles are fabricated through advanced 3D seamless flat-bed knitting technology. Output responses of the NGs are measured at different motion speeds and a maximum value of 41 V is obtained, corresponding to an output power of 168.1 μW. By connecting one NG with an external circuit, the influence of external resistance, capacitor, and motion speed on the charging characteristics of the system is systematically investigated. To demonstrate the potential of the smart insoles for monitoring human gait signals, two subjects were asked to walk on a treadmill at different speeds or with a limp. The results show that one can clearly distinguish walking with a limp from regular slow, normal, and fast walking states by using multiscale entropy analysis of the stride intervals.

On the first principle theory of nanogenerators from Maxwell's equations

Nanogenerators (NGs) are a field that uses Maxwell's displacement current as the driving force for effectively converting mechanical energy into electric power/signal, which have broad applications in energy science, environmental protection, wearable electronics, self-powered sensors, medical science, robotics and artificial intelligence. NGs are usually based on three effects: piezoelectricity, triboelectricity (contact electrification), and pyroelectricity. In this paper, a formal theory for NGs is presented starting from Maxwell's equations. Besides the general expression for displacement vector D = εE used for deriving classical electromagnetic dynamics, we added an additional term Ps in D, which represents the polarization created by the electrostatic surface charges owing to piezoelectricity and/or triboelectricity as a result of mechanical triggering in NG. In contrast to P that is resulted from the electric field induced medium polarization and vanishes if E = 0, Ps remains even when there is no external electric field. We reformulated the Maxwell equations that include both the medium polarizations due to electric field (P) and non-electric field (such as strain) (Ps) induced polarization terms, from which, the output power, electromagnetic behavior and current transport equation for a NG are systematically derived. A general solution is presented for the modified Maxwell equations, and analytical solutions about the output potential are provided for a few cases. The displacement current arising from ε∂E/∂t is responsible for the electromagnetic waves, while the newly added term ∂Ps/∂t is the application of Maxwell's equations in energy and sensors. This work sets the first principle theory for quantifying the performance and electromagnetic behavior of a nanogenerator in general.

An Easily Assembled Electromagnetic‐Triboelectric Hybrid Nanogenerator Driven by Magnetic Coupling for Fluid Energy Harvesting and Self‐Powered Flow Monitoring in a Smart Home/City

AbstractHarvesting wind energy and water flow energy from the living environment to efficiently and conveniently power many small electric devices at home is becoming increasingly important for the development of the smart home system. Triboelectric nanogenerators (TENGs) are considered to be one of the most effective devices to harness various types of mechanical energy. Here, an easily assembled electromagnetic‐triboelectric hybrid nanogenerator (EANG) driven by magnetic coupling is reported. The introduction of magnetic coupling makes it easy to package, maintain, and assemble a nanogenerator (NG), so its performance is very stable regardless of environmental variations. A sliding freestanding mode TENG and a rotary electromagnetic generator (EMG) are integrated to improve their output and broaden the frequency range of external energy. It is shown that the EANG can be conveniently integrated with a wind cup or water turbine and harvest fluid energy to power small electronic devices, such as a humidity sensor and temperature sensor. Moreover, a NG can be used as a self‐powered flow sensor to monitor the flow rate of outdoor wind and tap water. These results can be used to help solve practical problems regarding energy supplying and sensing in a smart home, smart building, and smart city.

Improved Piezoelectric Performance of Electrospun PVDF Nanofibers with Conductive Paint Coated Electrode

Fabrication of Nanogenerators (NGs) using Electrospun polyvinylidene fluoride (PVDF) nanofibers for sensing and energy harvesting applications is a trending research due to its flexibility, biocompatibility, low-cost, etc. Different electrode materials, polymer composites had been proposed to increase the energy output. However, the contact area between the electrode material and nanofiber mat which helps to conduct more piezoelectric charges to the electrode surface are still unexplored especially at nanoscale level. In this paper, authors have proposed the use of low-cost carbon conductive paint to increase the contact area between the electrode and nanofiber mat. The electrode material is coated with conductive paint and the NG was fabricated with that electrode to compare the performances with conventional NG. Piezoelectric performance of the proposed NG has increased substantially as it generates an open circuit voltage [Formula: see text]) of 4.5[Formula: see text]V and short circuit current [Formula: see text]) of 25[Formula: see text]nA, whereas the conventional NG can only produce 1.6 [Formula: see text]) and 1.5[Formula: see text]nA [Formula: see text]). A drop test experiment was conducted, and the device consistency was verified experimentally.

Effect of annealing temperature on the microstructure and optoelectrical properties of ZnO thin films and their application in self-powered accelerometers

This paper reports a piezoelectric nanogenerator (NG) with a thickness of approximately 80 μm for miniaturized self-powered acceleration sensors. To deposit the piezoelectric zinc oxide (ZnO) thin film, a magnetron sputtering machine was used. Polymethyl methacrylate (PMMA) and aluminum-doped zinc oxide (AZO) were used as the insulating layer and the top electrode of the NG, respectively. The experimental results show that the ZnO thin films annealed at 150°C exhibited the highest crystallinity among the prepared films and an optical band gap of 3.24 eV. The NG fabricated with an AZO/PMMA/ZnO/stainless steel configuration exhibited a higher output voltage than the device with an AZO/ZnO/PMMA/stainless steel configuration. In addition, the annealing temperature affected the open-circuit voltage of the NGs; the output voltage reached 3.81 V when the annealing temperature was 150°C. The open-circuit voltage of the prepared self-powered accelerometer increased linearly with acceleration. In addition, the small NG-based accelerometer, which exhibited excellent fatigue resistance, can be used for acceleration measurements of small and lightweight devices.

(Invited) Triboelectric Nanogenerators for Internet of Things and Self-Powered Systems

Self-powered system is a system that can sustainably operate without an external power supply for sensing, detection, data processing and data transmission. Nanogenerators (NG) were first developed for self-powered systems based on piezoelectric effect and triboelectrification effect for converting tiny mechanical energy into electricity, which have applications in internet of things, environmental/infrastructural monitoring, medical science, environmental science and security. NGs are the applications of Maxwell’s displacement current in energy and sensors. NGs have three major application fields: micro/nano-power source, self-powered sensors and blue energy. We will present the applications of the NGs for harvesting all kind mechanical energy that is available but wasted in our daily life, such as human motion, walking, vibration, mechanical triggering, rotating tire, wind, flowing water and more. Then, we will illustrate the networks based on triboelectric NGs for harvesting ocean water wave energy, for exploring its possibility as a sustainable large-scale power supply. Lastly, we will show that NGs as self-powered sensors for actively detecting the static and dynamic processes arising from mechanical agitation using the voltage and current output signals. This presentation will cover not only the fundamental science of triboelectric nanogenerators, but also will focus on the technology innovation and perspective industrial applications as well as business opportunities. Z.L. Wang, Materials Today, 20 (2017) 74-82.“Nanogenerators for Self-Powered Devices and Systems”, by Z.L. Wang, published by Georgia Institute of Technology (first book for free online down load): http://smartech.gatech.edu/handle/1853/39262 Z.L. Wang, L. Lin, J. Chen. S.M. Niu, Y.L. Zi “Triboelectric Nanogenerators”, Springer, 2016. http://www.springer.com/us/book/9783319400389L. Wang “Triboelectric Nanogenerators as New Energy Technology for Self-Powered Systems and as Active Mechanical and Chemical Sensors”, ACS Nano 7 (2013) 9533-9557.Z.L. Wang, J. Chen, L. Lin “Progress in triboelectric nanogenertors as new energy technology and self-powered sensors”, Energy & Environmental Sci, 8 (2015) 2250-2282.

Effect of Adding BaTiO3 to PVDF as Nano Generator

Piezoelectric nanogenerator based on a composite structure formed of Polyvinylidene Fluoride (PVDF) as the matrix and Barium Titanate BaTiO3 nanospherical after dissolving them in a solvent of Dimethyl Sulfoxide DMSO/Acetone in (1/3 v/v) then spanning it’s homogeneous solution on Aluminum foil. structural and morphology analyses that of fabricated nanofibers characterized by X-ray diffraction, Scanning Electron Microscope and the electrical output of piezoelectric membrane devices was measured by using oscilloscope. The electrical output of different samples were measured for the pure powder PVDF and for composite PVDF& BaTiO3. The highest PVDF composite piezoelectrically generated voltage for samples with BaTiO3 (20%PVDF & 25% BT) wt. %. where improved to 6 V in general the addition of BT Nc increases the piezoelectric response of electrospun PVDFnanofibers.

Simulation study on piezoelectric characteristics of two‐dimensional ZnO nanodiscs

Two-dimensional (2D) zinc oxide (ZnO) nanostructures have emerged as an attractive approach for constructing high-performance piezoelectric nanogenerators (NGs) because of their high rate of surface area to volume and good mechanical durability for applications in energy conversion devices. However, there has been to date no comprehensive study on piezoelectric characteristics of 2D ZnO nanostructures. In this paper, 2D nanodiscs have been prepared by aqueous solution method on flexible indium tin oxide coated polyethylene terephthalate substrates. Also, the piezoelectric characteristics are statistically demonstrated and analysed on the as-grown 2D ZnO nanodiscs by applying different external force with the finite element method (COMSOL Multiphysics). Besides, the size-dependent simulation analysis of piezopotentials is also conducted for further optimising output performance of NGs based on 2D ZnO nanostructures. Also, the simulation will provide a guideline for designing high-performance piezo-nanodevices.

Fiber/Fabric-Based Piezoelectric and Triboelectric Nanogenerators for Flexible/Stretchable and Wearable Electronics and Artificial Intelligence.

Integration of advanced nanogenerator technology with conventional textile processes fosters the emergence of textile-based nanogenerators (NGs), which will inevitably promote the rapid development and widespread applications of next-generation wearable electronics and multifaceted artificial intelligence systems. NGs endow smart textiles with mechanical energy harvesting and multifunctional self-powered sensing capabilities, while textiles provide a versatile flexible design carrier and extensive wearable application platform for their development. However, due to the lack of an effective interactive platform and communication channel between researchers specializing in NGs and those good at textiles, it is rather difficult to achieve fiber/fabric-based NGs with both excellent electrical output properties and outstanding textile-related performances. To this end, a critical review is presented on the current state of the arts of wearable fiber/fabric-based piezoelectric nanogenerators and triboelectric nanogenerators with respect to basic classifications, material selections, fabrication techniques, structural designs, and working principles, as well as potential applications. Furthermore, the potential difficulties and tough challenges that can impede their large-scale commercial applications are summarized and discussed. It is hoped that this review will not only deepen the ties between smart textiles and wearable NGs, but also push forward further research and applications of future wearable fiber/fabric-based NGs.

Different Trends of Hybrid Solar And Raindrops Energies to Generate Photovoltaic

New trends for making an all-weather photovoltaic (PV) that is able to trigger by both sunlight and raindrops become trends in developing the solar energy systems to generate electricity for households, industries and buildings. The idea is to develop a hybrid device that harvests kinetic energy from water without destroying the output of the solar cell during sunny times. This paper reviews the two devices of hybrid sunlight and raindrops, namely are the Triboelectric Nano Generator (TENG) and Pseudo Capacitor Graphene Layer (PCGL), respectively. Both TENG and PCGL similarly in such way places two transparent polymer layers on top of PV cell. When raindrops fall on to the layers and then roll off, the friction generates a static electricity charge. In addition, these devices even could provide electricity at night whenever there is rain. These two trends of all-weather PV obviously have advantages and drawbacks, as they have been developed in order to make them more compact and efficient as the device that harvesting sunlight during dry seasons and rainfall during wet seasons both for days and nights.

(Invited) Self-Powered Medical Electronics

Recently, piezoelectric nanogenerator（PENG） and triboelectric nanogenerator (TENG) have attracted much attention and been considered as another potential solution for harvesting mechanical energy. With its high output performance, outstanding biocompatibility and low cost, nanogenerator（NG） has been studied for powering implantable and wearable electronic medical devices. Here, we demonstrated a biomechanical-energy harvesting using a NG as a power source or an active sensor. The NGs can convert the mechanical energy from human motion into electricity and drive the implanted long-term self-powered medical devices or biosensors. An implantable triboelectric nanogenerator (iTENG) in a living animal has been developed to harvest energy from its periodic breathing. The energy generated from breathing and body moving was used to power a prototype pacemaker and a low-level laser cure (SPLC) system, respectively. Meanwhile, it was found that the self-powered system could regulate the heart rate of a rat and significantly accelerated the mouse embryonic osteoblasts' proliferation and differentiation. Real-time acquisition and wireless transmission of self-powered cardiac monitoring data was also demonstrated for the first time. Another NG based self-powered pulse sensor have been applied for antidiastole of coronary heart disease, atrial septal defect and atrial fibrillation from health. These works are concentrated on live-powered medical devices. It showed broad clinical applications of self-powered medical systems for disease detection and health care.

(Invited) Flexible Nanogenerators for Energy Harvesting and Self-Powered Biomedical Devices

Recently, flexible electronics have experienced a rapid development and are dramatically desirable for commercial, medical, and military applications. Conventional flexible biomedical sensors usually require external power-supply devices whose small power density and limited lifetime dramatically hinder the speedy advancement of this field. To solve the above issues, self-powered sensing technology has been introduced and attracted significant interests as a crucial alternative. The self-powered active sensor will generate electricity as a response to the external stimuli and the electric signal can reversely reflect the impact of the outside trigger. Therefore, it is able to effectively and independently work without any external power sources and hence its accelerated progress is of great significance to the prevalence of wearable and flexible sensors. Originated from Maxwell’s displacement current, nanogenerator (NG) based on triboelectric effects have been developing rapidly for efficiently harvesting environmental mechanical energy and self-powered active sensor. Triboelectric nanogenerator (TENG) relied on a conjunction of triboelectrification and electrostatic induction has shown numerous advantages, including large output, high efficiency, low cost, simple fabrication, light weight, and being environmental friendly. Besides mechanical energy, thermal energy is another important energy source especially for wearable electronics. The temperature difference (ΔT) between human body and surrounding environment always exists and can be used as driving force for electric energy generation through Seebeck effect. But the ΔT need to be furtherly enhanced. In our living environment, in addition to the direct heat source, light source (such as the infrared light) can also provide thermal energy through the photothermal effect. Based on the photothermal effect and Seebeck effect, photo-thermoelectric generator has been rapidly developed for converting photo energy into electricity without a spatial temperature gradient in the environment. In our works, flexible NGs based on triboelectric effect and photo-thermoelectric effect have been demonstrated and designed for wearable electronics. The electric signals obtained from the NGs not only can be acted as direct energy sources for flexible devices but also used for self-powered biomedical applications, such as human motion monitoring, temperature sensing, anti-bacterial treatment, and so on.

Fabrication of Tandem-type Vertically Integrated Nanogenerator by In-situ Deposition of AlN/ZnO Films

Fabrication of Tandem-type Vertically Integrated Nanogenerator by In-situ Deposition of AlN/ZnO Films

Electrochemical synthesis of p-Cu2O/n-ZnO heterojuncion for enhanced piezoelectric nanogenerators

The output performance of ZnO piezoelectric nanogenerators (NGs) has been limited because of the potential screening of large excess intrinsic electron carriers in ZnO. In this study, a simple and effective approach was demonstrated to fabricated piezoelectric nanogenerators (NGs) with higher output performance by constructing a p-Cu2O/n-ZnO heterojunction. The p–n heterostructure formed by adding Cu2O layer on ZnO, effectively reduced potential screening from intrinsic free electron carriers of ZnO. Using this approach, we obtained a maximum of output current up to 900 nA, which was a 30-fold higher output current compared with ZnO NG without a Cu2O layer. These results indicate a compatible strategy for realizing a high-performance piezoelectric harvesting devices.

Development of semi-transparent ZnO/FTO solar thermoelectric nanogenerator for energy efficient glazing

In this work we developed and successfully tested a new design of semi-transparent solar thermoelectric nanogenerator (NG) based on the pulsed electrodeposited array of ZnO nanorods on transparent conducting fluorine doped tin oxide (FTO) substrate. An operation of this NG caused by a distinguishable temperature gradient between 1-D ZnO array and uncoated FTO that spontaneously created under heating of ZnO/FTO composition, including under the influence of sunlight. The developed NG combines benefits of low thermal emittance of FTO and ZnO coatings with TE technology for the harvesting of photo-thermal energy of outdoor sunlight by the windows themselves to produce electricity. The network of such NGs can be integrated harmoniously into buildings without affecting the overall aesthetics and serve as a source of electricity sufficiently high to make sensors entirely autonomous in energy by the harvesting solar near-infrared radiation and heat from ambient.

Can nanogenerators contribute to the global greening data centres?

In past two decades, global data centres had become a major sector of energy consumption. In 2010, the consuming power of global data centres accounted for about 1.5% in the global electricity; however, by 2020, it was estimated that the power consumption of global data centres will account for over 8% of the global power usage. Although many outstanding practices had been conduted to improving the PUE (Power usage effectiveness) of data centres, the traditional approaches seem to have reached a ceiling by far. Meanwhile, the remarkable improvement in power efficacy of nanogenerators (NGs) in past five years, especially the discovery of triboelectric nanogenerators (TENGs), could offer intriguing prospects to further improve the PUE of data centres. Through an interdisciplinary perspective, an exploratory energy saving approach for GDCs (greening data centres) based on nanogenerators is proposed, which is defined as DEHNs (distributed energy harvesting via nanogenerators). In the proposed DEHNs, the different types of NGs are supposed to flexibly integrated into established or new data centres to further improve energy usageefficiency. Basically, as a potential ingredient in contributing to GDCs, DEHNs could offer a moderate promise, but also have limitations and challenges.

All-Printed Human Activity Monitoring and Energy Harvesting Device for Internet of Thing Applications.

A self-powered device for human activity monitoring and energy harvesting for Internet of Things (IoT) devices is proposed. The self-powered device utilizes flexible Nano-generators (NGs), flexible diodes and off-the-shelf capacitors. During footsteps the NGs generate an AC voltage then it is converted into DC using rectifiers and the DC power is stored in a capacitor for powering the IoT devices. Polydimethylsiloxane (PDMS) and zinc stannate (ZnSnO3) composite is utilized for the NG active layer, indium tin oxide (ITO) and aluminum (Al) are used as the bottom and top electrodes, respectively. Four diodes are fabricated on the bottom electrode of the NG and connected in bridge rectifier configuration. A generated voltage of 18 Vpeak was achieved with a human footstep. The self-powered smart device also showed excellent robustness and stable energy scavenger from human footsteps. As an application we demonstrate human activity detection and energy harvesting for IoT devices.

A Self-Powered Wearable Pressure Sensor and Pyroelectric Breathing Sensor Based on GO Interfaced PVDF Nanofibers

This paper reports a self-powered, flexible, piezo- and pyro-electric hybrid nanogenerator (NG) device that can be fixed on different locations of human skin for detecting static and dynamic pressu...