Search

Oceanic wave energy extraction through electrical generator is one of the most interesting topics in the field of power engineering. Almost all the existing relevant review paper focus on electrical generator with the working principle of electromagnetic induction or piezoelectric or triboelectric effect. In this paper, all the existing types (based on principle of operation) of electrical generator used for wave power harvesting are discussed. This paper not only covers recent progress in electrical power generation by electro-magnetic induction, piezoelectric generator, and electrostatic induction, but also presents critical comparative review as well where suitable use and weakness of each type of generators are discussed. Moreover, the application of advanced magnetic core, winding, and permanent magnets are discussed with extensive explanation which are not focused in the existing reviews. Various new constructional features of the electrical generators such as split translator flux switching, two-point absorber, triangular coil, dual port linear generator, piezoelectric, triboelectric nanogenerator, etc. are highlighted with principles of operation. It also includes emerging human intervened optimization method for determining optimum shape of generator and cooling system which is necessary to prevent demagnetization of the permanent magnet. Finally, the way of supply the generated electrical power form the generator to load/grid is thoroughly described in a separate section that would be obvious for successful operation. The comparison among all types of generators in terms of output voltage, current, scale of power production, power-frequency characteristics, power density, cascading, and approaches are tabulated in this paper.

The demand for using wireless sensors to monitor gases dissolved in transformer oil is growing and has brought challenges in the development of new sources of energy. Nano-generators are devices capable of converting mechanical energy, as vibrations, into electricity in a innovative and renewable way at low cost. In this work, the authors studied the addition of a steel spring to triboelectric nanogenerator (TENG) on the performance of its output power. Here, TENGs were built by using ZnO nanorods as donating electrons and PDMS:GO composites as negative material. PDMS:GO composites were prepared at different concentrations and the study was carried out in a wide frequency range (45 to 250 Hz). The addition of a steel spring to design of the TENG, as well as, 4% weight GO to PDMS improved the performance of the device. A power density around 246 mW m−2 , and output voltage of 4 V were obtained at 60 Hz. TENG’s ability to collect vibration energy from the wall of transformers and transform it into electrical energy is discussed based on the vibration frequencies obtained at different external points of transformers and performance of the devices.

A novel integrated multi-wall carbon nanotube /polydimethylsiloxane (MWCNTs/PDMS) and Polyvinylidene Fluoride (PVDF) based flexible triboelectric nanogenerator (TENG) was fabricated for energy harvesting application. The TNEG consists of minimal parts: aluminium (AI) electrode, PVDF layer and MWCNTs/PDMS layer. A surface roughness and thickness of −0.45 µm was measured for the fabricated MWCNT/PDMS respectively. The capability of the TENG in term of open circuit voltage (OCV) and short circuit current (SCC) was investigated by subjecting it to a force of 5 N, 10 N and 15 N at varying frequencies of 3 Hz, 5Hz and 7 Hz respectively. The maximum OCV of 21.6 V and SCC of 1.7 µA was obtained for an applied force of 15 N at frequency 7 Hz, respectively.

Energy harvesters for smart wearables are gaining increasing attention world-wide. Among the various type of options availabel, triboelectric nanogenerators harvesting mechanical energy from human body movements are especially attractive. In this work, a flexible sandwich-type triboelectric nanogenerator (FS-TENG) based on ridged and biocompatible silicone elastomers and thermoplastic polyurethane is proposed. The proposed FS- TENG exhibits the open-circuit voltages and maximum power density of ~80 volts and 0.35 mW/cm2, respectively. This preliminary performance already makes the device extremely promising to power low energy smart wearable devices, as well as monitor pressure in bespoke biomedical applications.

The market for wearable sensors is growing rapidly as interest in personal health has recently increased, and the Internet of Things (IoT) has developed. However, supplying power to wearable sensors, such as body-attached flexible devices and E-skin, is still a matter of concern. Herein, we report a triboelectric nanogenerator (TENG)-based E-skin that can harvest bio-friendly energy and self-powered pressure sensing with its own power source. Au-coated Cu yarn and polytetrafluoroethylene-molded micro-patterned polydimethylsiloxane were used to fabricate E-skin with excellent stability, high sensitivity, elasticity, and flexibility. The TENG-based E-skin generates an output peak voltage and current of up to 200 V and 2.7 µA, respectively, and is stable with 4,500 cycles of pushing motion without any deterioration of the output signal. In addition, it is possible to operate an electronic watch by charging a capacitor and measuring the arterial pulse of the wrist as a pressure sensor. The results of this study present potential solutions for power source and signal monitoring within soft/wearable devices and human-machine interfaces.

As the demand for low-carbon and eco-friendly energy is increasing and the use of wearable devices is soaring, the triboelectric nanogenerator (TENG), which can economically harvest energy, is in the spotlight. Among many materials, paper is considered a promising substrate and frame material for self-powered TENG due to its high accessibility, flexibility, and biocompatibility. Here, we present a new structure of foldable paper based TENG (FP-TENG) composed of paper and PTFE/Si-rubber. The double-folded FP-TENG generates voltages and currents of 153 V and 2.2 µA, respectively, and shows excellent durability without signal degradation under 5,000 cycles of external force. A watch strap was manufactured with FP-TENG and integrated with an electronic watch pannel to supply power, and several LEDs were turned on. Therefore, FP-TENG is expected to be utilized as a promising eco-friendly energy source for small electronic devices.

With the increasing in human population and decreasing in traditional energy methods made the human society all around to re-think towards Alternate energy sources. Moreover, potential usage of miniaturized electronic devices has been increasing in our day-to-day activities and their energy requirements also very less in terms of few mW/$\mu$ W. This paved a new path for many industrialist to turn their head towards energy harvesting techniques from human physiological body movements like walking, breathing, jogging, squatting etc., This research work mainly focuses on fabrication of Triboelectric nanogenerator using organic polymer materials PDMS Poly (dimethylsiloxane) which is a suitable candidate due to its interesting physical, electrical and mechanical property, cost effectiveness, user-friendliness, by low cost spin coating technique and subsequent annealing at $70-80^{\circ}C$.

A novel flexible triboelectric nanogenerator (TENG) was fabricated for energy harvesting applications. The TENG consists of graphite/polydimethylsiloxane (G/PDMS) composite on copper (Cu) as anode and polyvinylidene fluoride (PVDF) layer on aluminum (Al) as cathode. The G/PDMS composite was prepared by mixing G (6 wt%) and PDMS (74 wt%) in Toluene and bar coated on to a copper film. A surface thickness of 100 µm and 150 µm as well as a roughness of ~0.81 µm and ~1.5 µm was measured for the G/PDMS and PVDF, respectively. The capability of the TENG in term of open circuit voltage (OCV) and short circuit current (SCC) was investigated by subjecting it to a force of 4 N at varying frequencies of 3 Hz, 5 Hz and 7 Hz. Similarly, the OCV and SCC measurements were performed for 8 N and 12 N as well at different frequencies. A maximum OCV of 14 V and SCC of 3.2 μA was obtained for an applied force of 12 N at frequency 7 Hz, respectively.

Air breakdown effect, which restricts the increase of the surface charge density, is the major limitation for further improving the output performance of triboelectric nanogenerator (TENG). To solve this problem, a universal strategy which only requires adding an appropriate external capacitor to TENG is proposed in this work. By connecting a 68 pF external capacitor with a $2\times 2\ \text{cm}^{2}$ contact-separation (CS) mode TENG in parallel, the output energy per cycle can be increased to 2.5 times of that without an external capacitor. This research provides a novel and simple way to suppress the air breakdown effect and improve the output performance of CS-TENG.

A haptic-feedback ring enabled glove-based human-machine interface (HMI) using a ring-shaped triboelectric nanogenerator (TENG) for finger bending sensing, and a lead zirconate titanate (PZT) thin film for effective haptic sense simulating, is developed for advanced interaction and collaborative operation in robotic manipulation and virtual/augmented reality (VR/AR) area. With the novel voltage integration method, the continuous finger motion can be captured with the minimalistic sensor design, which is difficult to be achieved by conventional contact-separation mode TENGs. With the haptic feedback function enriched by the PZT stimulator, the real sense of touch, compress and force can be successfully simulated, showing great potential in next-generation virtual entertainment and educational training applications.

Zinc oxide (ZnO) nano-powder embedded within SU-8 matrix forms a new class of low-cost, large area, photo-patternable piezoelectric thin films enabling the rapid design of mechanical energy harvesters. For wider acceptance of such nano-composites, the deposition and integration process flow optimization in terms of patternability and piezoelectricity is required. In this paper, we report an optimum process flow for ZnO/SU-8 based nano-composite thin films for energy harvesting applications. By varying various patterning parameters, the optimally deposited 15% weight ratio based ZnO/SU-8 nano-composite thin film shows the optimum results with good piezoelectric voltage and transmittance characteristics for reliable photo-lithography. The trade-off between the piezo-response and photopatternability is analyzed using both experiments and finite element simulations. Furthermore, two types of energy harvesting devices are fabricated using the same nano-composite as an active layer which provide output voltages of ∼300 mV for the conventional cantilever type energy harvester at 0.5g and ∼570 mV for flexible nanogenerator using finger pressing. The simple, efficient, and rapid method to deposit thick, high-performance piezoelectric thin films over large area can be suitable for wide range of applications for the self-powering of IoT devices.

This work presents a triboelectric nanogenerators (TENG) based wide-range, self-powered flexible pressure sensor. The fabricated TENG can detect wide range of applied pressure from 3.2 to 1176 kPa. By analyzing the open-circuit voltage versus pressure curve, the sensitivity in three pressure regimes, namely low (1-10 kPa), medium-high (10-500 kPa) and ultra-high (>500 kPa) is extracted. The obtained sensitivities for these three pressure regimes are 3.16, 0.023 and 0.031 V•kPa-1, respectively. The origin of such a stable response of TENG at all of 3 pressure regimes lies in the use of real contact area of the interface pair. To the best of our knowledge, this is the first time a TENG as self-powered pressure sensor has been characterized over such a wide pressure range covering both low and super high pressures. These results show the potential of TENGs for a wide range of applications such as detecting the pressure in wearables, self-powered e-Skin for sole of humanoid robot to help them walk and stand, and the impact of wave energy.

Herein, we present a novel triboelectric nanogenerator based on nylon-11/poly-DADMAC and PVDF-TrFE nanofibers and demonstrate as a self-powered human motion sensor (SPHMS). The incorporation of cation poly-DAD MAC into the nylon-11 via the electrospinning method acts as a highly positive triboelectric layer that significantly enhanced dielectric constant by trapping surface charge in the composite materials. The fabricated SPHMS exhibited outstanding performance, including superior electrical performance (power 2.4 mW), excellent mechanical stability (>76k cycles), and sensitivity (1.01 V/KPa). As a proof of concept, the SPHMS was successfully demonstrated for monitoring human motion while walking, jogging, running, and jumping via a smartphone.

The conversion of water energy into sustainable electricity has attracted more and more attention. Conventional water energy harvesting technologies are limited by manufacturing materials and output performance. The triboelectric nanogenerator (TENG) shows good performance in mechanical energy harvesting, while it has a relatively low short-circuit current and large inherent impedance. A novel high DC current output salt battery (SB) hybrid and enhanced by TENG (DC-SBHET) is proposed in this paper. The high open-circuit voltage generated by TENG can accelerate the velocity of mobile ions in the SB. The combination of TENG and SB can successfully increase the DC short- circuit current up to 18.1mA. Nano-foam electrodes were also chosen to further increase the battery performance.

Sound energy is a ubiquitous renewable energy source. How to comprehensively harvest and utilize this energy has become a hot research topic. Triboelectric Nanogenerator(TENG) can convert different forms of mechanical energy into kinetic energy, and has significant advantages in micro-nano power generation, self-driving sensing, and device performance control. This work designs an ultra-high power density Helmholtz resonant cavity based on triboelectric nanogenerator with a printed electrode(H-TENG) for harvesting acoustic energy efficiently. We proposed an optimized scheme for harvesting sound energy effectively by the special treatment of the electrode flexible film. Then we researched the structure of the resonant cavity, acoustic conditions, and the tension of flexible film, they can affect the output characteristics of the H-TENG acoustic energy converter. We find H-TENG follows the best output frequency deviation law, that is, introducing appropriate tension according to a specific sound wave range can improve the best frequency response. Compared with the best results in the early literature, the H-TENG has a high power density of 1.47 W/m2 sound pressure. The study showed that the high power output of H-TENG can light up 457 LEDs at the same time. Finally, this research also proposes the application potential of H-TENG in energy conversion and acoustic sensing.

Several species of terrestrial and marine organisms like seals, use their vibrissae (whiskers) as important tactile sensors to find and follow underwater wakes. Here, we propose a bionic-tactile sensor (BTS) based on triboelectric nanogenerator to capture complex stimuli by organisms moving through water, and utilize received signal to track the hydrodynamic trails. One of the BTS's essential features is that triboelectric nanogenerator coupled with inspired by the structure characteristics of seal whiskers, which leads to the highly-sensitive detection of stimuli. Another is that our design is self-powered without additional power supply. Experiments show that the designed BTS has the ability to perceive the hydrodynamic trails left by underwater moving objects. Moreover, the relationship between the output signal and the movement parameters is linear, and we use this principle to perceive the relative motion state of the moving object. These new insights into the biological basis of tactile perception using whiskers provides new design guidelines to develop efficient underwater robotic sensors.

This paper present the conical Helmholtz resonator-based triboelectric nanogenerator (CH-TENG) designed for highly efficient harvesting of acoustic energy in various occasions. This CH-TENG consists of an acoustic collecting tube, a conical Helmholtz resonant cavity and an aluminum film with uniform distributed pinholes, and a dielectric soft film with one side ink-printed for electrode. Furthermore, the effects of resonant cavity structure, sound wave frequency, sound pressure level and sound collection tube on the performance of CH-TENG are systematically studied. Compared with previous research, the proposed CH-TENG can generates higher acoustic sensitivity per unit area and power density per unit sound pressure, because the acoustic collecting tube structure gathers more sound waves and sound wave amplification capability of the Conical Helmholtz Resonator stronger. Meanwhile, this new technique to some extent can serve as a sensor.

This paper proposed a hybridized energy harvester combining electromagnetic, piezoelectric, and triboelectric transduction mechanisms for ocean wave energy harvesting. Two energy harvesting mechanisms of wave shaking and heaving are contained in this device. The shaking energy harvesting mechanism (S-EHM) consists of a compound pendulum mechanism and a gear mechanism. Together with an electromagnetic generator (EMG) and a piezoelectric generator (PEG) are used to harvest the shaking energy of ocean waves. The heaving energy harvesting mechanism (H-EHM) consists of a sliding sub, mass slider and springs. Meanwhile, the triboelectric nanogenerator (TENG) is used to harvest the undulations energy of ocean waves. They all supply energy to the electrical appliances inside the marine buoy, which can extend its working life. The diameter of the harvester is 140 mm and the height is 185 mm. The tested maximum output voltages of the electromagnetic, piezoelectric and triboelectric parts are 12V, 18V, and 55 V, respectively. Moreover, the device can light up at least 90 LEDs and can power the temperature and humidity sensor to display the ambient temperature.

Nanogenerator has demonstrated its capability as motion, displacement and pressure sensor in various sensing scenarios. This work presents the first time-dependent finite element modeling of nanogenerator with resistive load. Compared with previous research on the theoretical study and modeling of nanogenerator, three distinctive advances have been achieved: (1) the finite element modeling of the nanogenerator is established and coupled with the lumped-parameter elements for resistive load; (2) the time-dependent study is conducted rather than the quasi-static study based on parametric sweep to reveal the transient process; (3) the results of finite element simulations are compared with the derived results based on the simplified theoretical model to reveal the influence of fringe effect.

Traditional vibration sensor of ship machinery using cable for power supply cannot meet the requirements of a large number of distributed sensors of the intelligent ship. A bouncing-ball based triboelectric nanogenerator (BB-TENG) to be used as a self-powered vibration frequency monitoring sensor is proposed. In the sensing test, the vibration frequency of 15 ∼ 50 Hz under different amplitudes can be measured accurately. The frequency calculation of the voltage signal can accurately reflect external vibration frequency, while the change of short-circuit current has linear relationship with the frequency, and the correlation coefficient is about 0.99. In addition, electrical signal test results and photos taken by high-speed cameras show that the limit of the available detection frequency of BB-TENG increases with the increase of amplitude and support height. The electrical output of BB-TENG under different working conditions are tested, which provides the basis for selecting suitable BB-TENG according to different vibration characteristics.

Powering marine distributed nodes (e.g. monitoring buoys) has always been challenging under the harsh conditions in oceans. Triboelectric nanogenerator (TENG), on account of its robustness and cost, provide a novel solution to this problem. In this study, a stackable TENG (S-TENG) consisting of polytetrafluoroethylene pellets, an acrylic plates coated with aluminum film and a 3D-printed brace, has been proposed to harvest wave energy efficiently. Experiments show that each S-TENG unit produces a maximum peak power of 25.22mW while a power density of 34.65W/m3 is achieved. The output characteristic of multiple S-TENG units parallel connected is studied. It turns out that the output performance yields linear increase with the unit number without having to use rectifier bridge. This feature indicates that self-powered marine monitoring buoy is achievable by S-TENG integration.

Wearable electronics and electric skin attract increasing attention, which demand high transparency, extensibility, and biocompatibility. In this work, a transparent and highly stretchable pyramidal hydrogel-based triboelectric nanogenerator (HTG) for tactile sensation and neck movement detection is reported. Hydrogel can be easily stretched to 800% of the initial length. The output property of HTG could reach up to 360V and 1.27mW. Meanwhile, a slight signal like blowing could also be detected by the proposed device. Besides, the charging time of the capacitor reveals the dependence of output property and frequency. This work provides a brilliant method for self-powered physiological signal monitoring.

There are many studies on the use of solid-liquid triboelectric nanogenerator (TENG) to harvest energy from water motion to obtain sustainable electrical energy, but there are very few studies on the collection of oil Kinetic energy. Insulating oil is a kind of liquid dielectric with good physical and chemical properties, dielectric properties, and flow characteristics. It is widely used in power equipment and plays the role of electrical insulation, convection heat dissipation, and arc suppression. We have invented a TENG that can be used to harvest the energy of oil motion. Different structural designs have verified that TENG can effectively collect the mechanical energy generated by oil motion. The generator producing an open circuit voltage of up to 100V, and a short circuit current of up to 0.5µA. Also, using reactive ion etching (RIE) technology to process the surface of the solid insulating material with microstructures, the output of TENG is increased by about five times. The research content of this paper provides experimental support for detecting the electrification degree of the oil flow in the transformer through TENG. The designed TENG can be further applied to the oil flow electrification detection of power equipment.

Recently, environmentally, friendly and flexible piezoelectric generators have attracted considerable interest in powering wearable and implantable devices. In this present work, a lead free and flexible piezoelectric nanogenerator with good efficiency is demonstrated, based on composite film of zinc doped $\text{Ba}_{0.85}\text{Ca}_{0.15}\text{Ti}_{0.09}\text{Zr}_{0.10}\mathrm{O}_{3}$ (Zn-BCZT) nanoparticles embedded into polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) polymer. The effect of the different doping contents of Zn-BCZT on the electrical behavior and the output performance of piezoelectric nanogenerator were investigated. As a result, composite film with 7 wt.% contents Zn-BCZT shows an excellent performance, which generated the maximum open-circuit voltage of 2.24 V. Moreover, impedance spectra show increased conductivity with increasing of Zn-BCZT content. Besides, Zn-BCZT/PVDF-HFP nanogenerators generate the maximum power equal to $2.26\ \mu\mathrm{W}$ across a load resistance of $860\ \mathrm{k} \mathrm{\Omega}$ with 7% of content. The output voltage of the nanogenerator shows good linear relationship with the applied force. Due to the susceptibility of the force, the obtained piezoelectric composite can be used in several applications such as a sensor.

Piezoelectric nanogenerator are attracting a lot of attention due to environmental constraints and the ecological considerations of energy collection. A piezoelectric nanocomposite based on Ba 0.85 Ca 0.15 Zr 0.1 Ti 0.9 O 3 (BCZT) nanoparticles and PDMS polymer with excellent output properties for the application of nanogenerators has been developed. The piezoelectric nanogenerator is smart device that offers these required qualities and properties and converts mechanical energy. Here PENG can generate an open circuit voltage of 10 V respectively under the effect of light finger tapping. It reaches an output power of $\mathrm{P}=2.218\ \mu\mathrm{W}$ for a resistance $\mathrm{R}=370\ \mathrm{k}\Omega$ under shaker vibration. This generator is known by its simple and ordinary design as well its high performance after polarization. However, the polarization is long and unsafe. To avoid this problem, a homogeneous distribution of carbon nanotubes (CNTs) on the BCZT/PDMS matrix is the best solution to have self-polarized generator. In this study, piezoelectric nanocomposites were prepared using solution mixing method. A comparative study was performed to investigate the impact of CNTs on the performance of nanogenrators under external mechanical load. The nanogenerator with 15 wt.% BCZT doped with CNTs offers an outstanding output performance with an open circuit voltage of 15 V and an output power $\mathrm{P}=5.68029\ \mu\mathrm{W}$ at a resistance load $\mathrm{R}=350\ \mathrm{k}\Omega$ using the shaker device.

Barium titanate (BaTiO 3 ) as a kind of lead-free biocompatible ceramics, has become one of the most promising piezoelectric materials for fabricating piezoelectric nanogenerator. In order to increase the electrical performance of nanomaterials, Zirconium acetate was doped into BaTiO 3 to form barium zirconate titanate (BaZr x Ti 1-x O 3 , short for BZT). In this study, we introduce a highly efficient piezoelectric energy harvester based on a Pb-free representative compound BaZr 0.1 Ti 0.9 O 3 . Barium zirconate titanate (BZT) powders were prepared by sol–gel process. Piezoelectric nanogenerators were fabricated by various concentrations (10 wt.%; 15 wt.%; 20 wt.%; 25 wt.% and 30 wt.%) of BZT particles dispersed in PVDF-HFP matrix to form a nanocomposite. The electrical properties as well as the piezoelectric performance of the materials are monitored for the fabricated nanocomposite in mechanical energy harvesting. The as-prepared piezoelectric device of 20 wt.% BZT in PVDF-HFP exhibits an enhanced output voltage up to 4.6 V and power of $12.807\ \mu\mathrm{W}$ . Complex impedance plots show arcs which explain the impedance results. It can be seen that for 20 wt.% of BZT. The conducting charge reaches maximum, and therefore we contribute to the relaxation in the piezoelectric materials.

The surface charge density of the tribo-layer is the paramount parameter to determine the electrical output of triboelectric nanogenerator(TENG). Most previous works focused on high dielectric metal particle doping. However, metal nanoparticles will form charge leakage channels in the triboelectric layer, which will reduce the surface charge density and thus weaken the output of TENG. In this paper, a new doping scheme of SiO 2 @Ag composite particles was proposed. By attaching Ag nanoparticles to the surface of SiO 2 microspheres, the problem of Ag nanoparticles being easily agglomerated due to the surface potential energy was not only solved, but the SiO 2 microspheres could construct a blocking layer in the triboelectric layer to prevent the leakage of surface charges. The output performance of reported TENG significantly yielded 241 µC/m2 in charge density, giving over 3.45-fold enhancement to the unadulterated TENG. As such, the demonstrated TENG could potentially serve as sensitive electromechanical energy conversion device, and provides a promising power solution for MEMS transducers and energy harvesting applications.

Electronic skin (e-skin) is a kind of artificial skin, which has great application value in the fields of sensors, signal monitoring and human-machine interaction. This paper proposes a new type of self-powered flexible hybrid wearable e-skin system based on the combined working mechanism of Single-Electrode mode Triboelectric Nanogenerator (SE-TENG) and Piezoelectric Nanogenerator (PENG). The electrode and piezoelectric material are designed into a serpentine grid structure, which greatly improves the stretchability. The open circuit voltage (V OC ) is ~100V, the short circuit current (I SC ) is ~10µA, and the power density is as high as 1mW / cm2. The system can not only be used as a self-powered sensor to detect physical signals in real time, but also can achieve high-precision positioning functions, which has extremely broad application prospects in the field of artificial intelligence.

This paper reports a high-efficiency raindrops energy harvester using the interdigital electrode. With the new electrode deployment and connection scheme, the proposed raindrops energy harvester shows excellent energy conversion effeciency up to 2.5%, over 250 times higher than the conventional interdigital electrode-based triboelectric nanogenerator with efficiency of only 0.01%. The performance under the different finger electrodes was investigated. Note that the first electrode of the interdigital electrode is designed for the energy harvesting and the rest are utilized to detect the raindrops speed. We also find out that the open-circuit voltage varies with the tilt angle of the structure, of which the inclination angle of 45 degrees shows the best output performance. And under the condition of 0 degree, the open-circuit voltage first decreases and then gradually remains stable, rather than showing no voltage output. The proposed raindrops generator pushes forward a significant step of realizing raindrops energy harvesting in real-world application.

Origami, an ancient art of paper folding with a history spanning over 1000 years, can devise ingenious patterns with unique advantages in terms of great flexibility, lightweight, extreme simplicity, and excellent shape adaptability. The poor stability of electret / triboelectric devices in a humid environment is a key challenge faced by researchers worldwide. Inspired from Japanese Muira-origami structures, we propose a "W-tube" shaped triboelectric nanogenerator (WTN) with the two pieces of electret films encapsulated inside to isolate the humid environment. Besides, it's capable of capturing energy from various moving scenes, including horizontal or vertical pressing, and lateral bending. We have tested multiple parameters of WTN in detail, including the influence of the number of generating units, the original height of equipment, the acceleration and the excitation direction on the output performance. This work combines the ancient origami art with energy conversion technology to create a multifunctional waterproof energy harvesting device.

Piezoelectric nanogenerators used for energy harvesting in wearable electronics require flexibility, durability, and skin compatibility. Previous work has identified expanded polytetrafluoroethylene (ePTFE) as a potential candidate. A ferroelectret film was prepared by laminating ePTFE membranes and two fluorinated ethylene propylene (FEP) films using hot pressing, and injecting charges through corona discharge process. Using conductive fabric containing poly(3,4- ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as electrodes, an all-organic nanogenerator was obtained. The open- circuit voltage and short-circuit current were measured to characterize the piezoelectric response. The short-circuit current was found to be approximately 50 nA for one layer of ePTFE membrane (15 × 15 mm2) under light pressure from one finger, and no increase in current and voltage was found from additional ePTFE layers. The polarizability and charges stability of the FEP/ePTFE/FEP film were also evaluated. The flexible ferroelectret nanogenerator can be embedded into clothes or insole and is expected to power continuously future wearable electronics system.

In order to collect mechanical energy in the environment for self-powered sensor applications, a self-powered capacitive pressure sensor with liquid alloy composite as electrode is developed based on triboelectric nanogenerator (TENG). A micro-pyramid structure is fabricated on the surface of polydimethylsiloxane (PDMS) to improve the performance of the pressure sensor. Test results show that the sensitivity of the pressure sensor is increased by 86.26% compared with the sensor without the micro-pyramid structure. The sensor also has an outstanding output performance. When resistance is 100 MΩ, power output has reached nearly 64 μW.

PVDF (polyvinylidene fluoride) and its copolymers are the most promising piezoelectric polymers in sensors, actuators, and energy harvesting, owing to a repetitive structure - [CH 2 — CF 2 ] n - and 50% crystalline. In the present study, we examined the influence of multi-jet (32 jets) electrospinning with a randomized approach focused on three variables, which are feeding rate, the voltage applied, and tip-to-collector distance. Furthermore, the effect of single and double layer piezoelectric nanogenerator (PENG) was demonstrated under the pendulum impact loadings. The prepared nanofiber structures were characterized using FE-SEM, FTIR, and XRD. Outcomes from the morphological analysis appeared that the spinning parameter, the tip-to-collector distance, plays a crucial role in the formation of beads free with uniform distribution of nanofibers and β-phase formation. The fabricated PENG was able to generate a maximum open-circuit output of 24 V at 2.5 N from 50 μm thick nanofiber web under a single impact. In this way, the output voltage generated is sufficient for the operation of nanoelectromechanical systems (NEMS), low-power electronics and energy harvesting.

Currently, with the transition to the ubiquitous era, next-generation electronic devices such as artificial electronic skin, wearable computers, and flexible displays have been developed that are light and portable and can be easily applied to human life. Therefore, in order to supply power to such devices, the importance for the development of an energy devices is increasing. To address this issue, a stretchable on-skin based triboelectric nanogenerator (TENG) that contacts to the skin and can generate energy from the free movement is proposed. It is easier to manufacture than the previously reported body-attachable TENG and is ultrathin with a total thickness of 200 μm. As an electrode, the conductive thread was formed in a winding pattern on an elastomer substrate, showed high elasticity of 100% or more, and stability without distortion even under repeated strain. It adhered to the back hand to generate an electrical output of 280 V and 12 μA, and the test on the electronic drive demonstrated its practical applicability. The on-skin based TENG may be utilized as a stretchable and flexible energy device that can replace the conventional bulk battery, and has the potential to be an important core technology in combination with E-skin and wearable sensors.

Piezoelectric nanogenerator (PNG) is a type of sensor that converts mechanical energy to electrical energy by detecting small-scale physical deformation. In this study, to realize a PNG, firstly polyvinylidene difluoride (PVDF) based electrospun nanofiber film is produced through electrospinning system. The obtained nanofiber film was characterized by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR). After that, the PNG device was built as the capacitor by locating the PVDF electrospun nanofiber between two aluminum conductive plates and cabled. The piezoelectric energy harvesting analyses of the PNG was defined by taking measurements under various resistive loads. At a vibration frequency of 15 Hz, the effective voltage value of the PNG reached the maximum voltage of 62.6 mV under the resistive load of $750 \mathrm{K}\Omega$ while its electrical power was around $5.23 \mu \mathrm{W}$ under the same load. The PNG based energy harvesting system aims to obtain electrical energy from the natural vibrational sources for mobile microelectronics.

With the further growth of the Internet of things (IoT), flexible piezoelectric nanogenerators (PENGs) are extensively gaining attention due to the possibility to harvest wasted mechanical energy to power electronics and nano systems. In this context, lead-free composite was used to fabricate nanogenerators (NGs) via solution mixing method. The effect of the used solvent and the concentration of the BaTiO3 particles on the crystallinity structure and the quality of composite were deeply investigated using X-ray diffractometer (XRD) and scanning electron microscopy (SEM) in addition to the piezoelectric performance. The study shows that composites dissolved in N, N, dimethylformamide (DMF) exhibit better performance comparing to those dissolved in N-methyl-2-pyrrolidone (NMP). The nanogenerator prepared with 20 wt. % BaTiO3 and dissolved in DMF solvent possesses the highest output voltage around 1.02 V and output power around 32 n W because of the increased crystallinity in comparison to other samples which are dominated by the presence of a-phase. These results indicate that NGs based on PVDF-HFP/BaTiO3 can be useful for flexible and wearable self-powered electrical devices and systems.

The design of endoscopes has not considered the compliance adaptability inside the body. Hence, endoscopy procedures are harmful and even fatal during endoscopic procedure when using commercial endoscopes. A cutting-edge technology should involve the redesign of endoscopes based on stimuli responsive integrated devices. Herein, we report and discuss the results of soft sensors integrated in a custom pneumatically actuated soft silicone-structure simulating the shape of soft endoscopes and catheters that can respond to low-load sensing capabilities such as tactile and multidirectional stimuli. For this purpose, two triboelectric nanogenerator based-sensors, lateral and semispherical, were integrated. Lateral sensor showed the highest voltage outputs (1.25 V) at 45 kPa of pressure, while pressures of 30 and 35 kPa generated voltages of 100 and 500 mV, respectively; showing high sensitivity at very low pressures. Moreover, regarding multidirectional sensing, the semispherical sensor showed voltage outputs of 110 mV for 0 degrees of interaction with regard to axial axis, while 75-85 mV for interaction angles of 30 and 60 degrees.

A triboelectric nanogenerator (TENG) is a promising candidate for harvesting the wasted energy from the ambient environment and utilizing it as an independent power source for batteries used in wearable and portable devices as well as sensing systems. This paper investigated the performance and behavior of triboelectric energy harvesters based on energy harvesting floor tiles by applying different mechanical input parameters such as contact gap, velocity, and vibration frequency to characterize the electrical characteristics while maintaining the applied pressure of 600 kPa and temperature. The results revealed that massive air gap displacement tends to generate higher electrical output. This demonstrated that the device could generate 2294.14 µW of optimal power and 95.50 µJ of total energy in 10 s at the mechanical excited frequency of 2 Hz with a fixed gap displacement of 5 mm. Moreover, the output power is proportional to the velocity of the cover plate movement. In contrast, varying the relative humidity (%RH) showed that the TENG could generate high electrical output at low relative humidity. The proposed work demonstrates that the TENG can function as an energy-harvesting device from low-frequency mechanical vibration for energy harvesting floor tiles.

This paper reports a self-powered sensor for detecting wind speed and direction using triboelectric nanogenerator with a curved flap array. The sensor comprises a radial array of polyethylene terephthalate (PET)/Al flaps rolled up in different directions and polytetrafluoroethylene/Cu substrate. The curved flaps are simply fabricated through plastic deformation of PET/Al film. When the wind blows, the curved flap can be easily deformed, and thus the contact area between the flap and the substrate changes. The change in the contact area enables the flap to generate voltage via triboelectrification. Experimental results confirm that the voltage generated from the flap increases as the wind speed increases. We demonstrated that our sensor can detect both the wind speed and direction simultaneously based on the difference of the output voltage of the flaps. The proposed wind sensor has great potential in self-sustainable environmental monitoring applications.

Wearable photonics is an emerging field in wearable devices. Current wearable AlN photonics is passive without tuning capability, hindering its versatile applications in optical switching and signal encoding. The relatively small Pockels coefficient of AlN requires very high voltage for a wide wavelength tuning range, which is hardly achievable in traditional wearable energy sources. TENG is a promising energy source with a high voltage output for wearable devices. This paper presents the first demonstration of wide wavelength tuning in AlN photonics by leveraging TENG's high voltage output.

Herein, a self-powered flex sensor (SPFS) based on triboelectric nanogenerator is newly presented for detecting finger bending motion and hand gestures to be used in prosthetic arm and robotic applications. Drawn inspiration from the human skin dermis-epidermis intermesh structure, the fabricated flex sensor was designed with a random microstructure on triboelectric material surface, resulting in a high sensitivity of 0. 77 VkPa-1 and high stability (>100,000 loading-unloading cycles). The proposed self-powered flex sensor was successfully demonstrated in the real-time applications such as interpreting gesticulation and precise control of the wireless bionic arm.

We report a type of miniaturized and self-powered gas identification platform for wearable applications that works on the principle of ion mobility transients offering a high degree of selectivity for a variety of gas species. The self-powered operation of the sensor exploited the high voltage output from a systematically designed triboelectric nanogenerator (TENG). The multi-layer TENG platform provided a voltage of the order kV just by finger triggering, which was further leveraged in a special type of electrode (tip-plate) configuration making it possible to obtain plasma discharge of a wide range of gas molecules at atmospheric condition. By adding an additional collector plate at a specific distance within the device configuration, we successfully demonstrated different transient characteristics for different gas molecules which can be directly attributed to their differences in terms of ion-mobility. Our analysis clearly indicated unique and repeatable discharge characteristics at various mixture conditions and atmospheric pressure. We further employ machine learning to classify different gases based on the transient dynamics observed at the collector plate. High classification accuracy was obtained for four different gases even using a shallow network that indicated the potential of the proposed platform as a low-power, small foot-print wearable Internet of Things (IoTs) device for gas leak detection. It is envisioned that the proposed platform can enable early detection of gas species by incorporating the transient development of the multitude of time-domain finger-prints into the machine learning model.

We study the feasibility of actively and efficiently tuning an aluminum nitride (AlN) photonic modulator using a triboelectric nanogenerator (TENG). By utilizing the Pockels effect in AlN, AlN microring resonator (MRR) modulator can be tuned by the external E-field penetrating through it. The high open-circuit voltage provided by the TENG has synergy with the capacitor nature of AlN MRR modulators. The high voltage can be applied to the AlN modulator with negligible degradation. We demonstrate dynamic modulation of AlN modulator using a textile TENG. The AlN modulator has high fabrication variation tolerance. The hybrid integrated system is not affected by the hand tapping speed on TENG. Dynamic optical switching is realized which is further utilized to demonstrate the optical Morse code transmission. This hybrid integration is a crucial demonstration toward future self-sustainable wearable photonic IC, which will find significant applications in Internet of Things (IoT) and human-machine interface (HMI).

Soft robotics is an exciting novel research field and has great potentiality in human-machine cooperation. This kind of robot can undergo large deformations to execute complex motions, which leads to the difficulty to apply traditional sensors and the lack of necessary feedback. Therefore, we want to create a sensory finger that is able to grasp and hold heavy objects. This work explores the potential of triboelectric nanogenerators (TENGs) and presents the demonstration of TENG based on tactile sensors integrated into the structure of a soft finger with variable stiffness. For displaying the sensing result, three soft fingers were assembled to form a soft gripper. Our result shows that the tactile sensor with strip electrodes can detect the contact position when comparing the output difference in different electrodes. In order to describe the shape of the grab target, in this paper, we theoretically analyze the relative position relationship of the end before and after the finger bending deformation, and obtain the finger-bending mode. In the demonstration, the gripper integrating with the sensor can roughly distinguish the scale of the object by combining tactile perception capability. The proposed highly pliable fingers can help the robot handle the fragile and soft objects and appropriately recognize their shapes in complex environment.

A triboelectric interacting patch with only four sensing electrodes is presented as flexible and multifunctional human-machine interface for the detection of various human-machine interactions. By leveraging the predefined operation areas, position detection under finger operations can be achieved through the output relationship of the four electrodes. The accurate sensing capability of the triboelectric patch is compatible with common finger motions such as finger tapping and sliding, opening up broad application in various interacting areas, e.g., writing interface, security code system, intuitive intelligent control, virtual/augmented reality, and robotics, etc.