With the development of smart grid, many wireless sensor nodes (WSN) used in monitoring grid equipment need continuous power supply. This work propose a multi-frequency array piezoelectric vibration energy harvester (PVEH) powering WSN based on the grid transformers vibration of 100, 200 and 300 Hz. The PZT bimorph with U shaped mass sturcture is design and opitimized by finite element simulation. The bonding method of epoxy conductivity and insulation is studied for PZT bimorph and aluminum packaged PVEHs. The equivalent circuit modeling and interface circuit of PVEHs are studied in LTspice simulation. Through the whole system design of the array PVEHs powered WSN circuit with LTC3331 chip, the WSN can run continuously in simultation and experimental verification. The feasibility of multi-frequency PVEH powered WSN is verified on the 500 kV transformer in filed operation. This research has important application value to the design of WSN self-power supply for smart grid.

Piezoelectric fragility is concerned with low broadband and large amplitude vibration for energy harvesting in human motion, vehicles, wave energy, etc. The design of the stopper is helpful for the protection and broadband of the piezoelectric vibration energy harvester (PVEH), but the output is limited due to uneven stress distribution and collision energy loss. This paper proposes a U-shaped mass PVEH with double-point stopper and magnetic coupling. The stress homogenization method of the cantilever beam is achieved by converting the collision energy into bending moment by double-point stopper, which effectively improves the electromechanical coupling coefficient of the structure. Thus, the double-point stopper enables 1.5 times saturation displacement within allowable PZT stress. The experimental performance is carried out that PVEH with double-point stopper and magnetic coupling has double higher power output of 10.2 mW than single-point stopper at the excitation level of 0.6 g. The stopper collision and the magnetic coupling broaden the high and low frequency response of the PVEH system jointly. It has voltage output beyond 40 V with broadband of 8-15.6 Hz under 1 g acceleration in test. This work has a good potential in the occasions of the big mass, stopper protection and magnetic coupling design for low frequency, broadband and large amplitude of PVEH.

To warn of overcurrent heating, temperature wireless sensor node (WSN) need to be deployed on the overhead lines of the power grid. The sustainable power supply of WSN is difficult. Using the electric field energy around the transmission line to power the sensor has the advantages of stability, reliability and sustainability, but the electric field energy harvesting (EFEH) power need to be improved. This paper studies the principle of energy harvesting by displacement current and discharge method, and analyzes the influencing factors of the output power of the EFEH unit. The power improvement method of the EFEH unit is proposed by improving the coupling capacitor and the energy storage capacity discharge voltage. The relationship between the structural parameters of energy cylinder and induced potential and coupling capacitance is explored by COMSOL simulation software. A low-cost, self-driven and adjustable high voltage undervoltage lock (UVLO) circuit is proposed. A 10 kV high voltage generation platform is built in the laboratory, and the wireless temperature and humidity sensor is self-powered by the EFEH with power of 2.04 mW. This research has important theoretical and application value for the high voltage side EFEH powered WSN.

Self-sustained wireless sensing nodes (WSN) with energy harvesting, low power consumption, and intelligent sensing are the key devices in artificial intelligence of things (AIoT) area. This paper designs a tri-hybrid generator with electromagnetic-piezoelectric-triboelectric units integrated into one vibration energy harvesting structure. The tri-hybrid generator has three functions with electromagnetic unit for power supply with 13.1 mW, two piezoelectric units as the accelerometer for amplitude and frequency sensing with broadband decoupling function, triboelectric unit for triggering the self-wakeup WSN. The tri-hybrid generator structure is simulated and optimized by theory and finite element modeling, and the performance is tested in a vibration platform. To achieve self-sustained WSN, this study designs the power management circuit with maximum power point tracking and undervoltage lock function, combining periodic wake-up with overload self-wakeup to decrease 94.2% WSN power consumption. Self-sustained WSN is realized in the laboratory and verified on the vehicle engine. Finally, the application of wireless vibration sensing is verified on the vehicle engine. This work has a wide range of applications in vibration scenarios and hopefully promotes the development of AIoT.

The Internet of Things calls for the demand for wearable self-powered sensors for human motion monitoring and interaction. However, the redundant data and large amount of power consumption limit the application in sustainable wireless sensing. In this study, a flexible hybrid nanogenerator with bridge structure design for self-powered wearable sensor is proposed. When harvesting energy from the finger bent motion, it combines contact separation mode for triboelectric nanogenerator (TENG) with bending d31 mode for piezoelectric generator (PEG). To highlight the significance, we propose an autonomous wake-up wireless sensing method by hybrid generator in wearable bending. Different from recording and transmitting data all the time, the TENG signal as a trigger to record the PEG voltage amplitude as angle sensing data for wireless transmitting. Concise and accurate sensing data with autonomous wake-up is expected to reduce the computational burden and power consumption for wireless sensing and provide more possibilities for wearable wireless monitoring and human-computer interaction. The wireless manipulator interaction experiment based on this hybrid nanogenerator as wearable bending sensor verifies the feasibility of this scheme, which has a great application prospect in wearable self-powered sensors field such as virtual reality and robot control.

Flexible energy storage devices play significant role in wearable and portable electronics. Herein, a cobalt-nickel phosphate (CoNiP2O7) composite was synthesized on conductive carbon nanotubes (CNTs) substrate by facile one-step electrochemical deposition method, forming a binder-free CoNiP2O7@CNTs positive electrode for microsupercapacitors (MSCs). Combined with a CNTs substrate on the opposite side of interdigitated electrodes, a CoNiP2O7@CNTs//CNTs hybrid MSC device was assembled. It displayed good electrochemical performance with a largest areal capacitance of 20.9 mF.cm(-2) at 0.08 mA.cm(-2) and an energy density of 2.9 mu Wh.cm(-2). To construct a self-powered solar cell energy storage system, the proposed MSC device was utilized for energy storage and further provided power for red light-emitting diode (LED), forming natural energy collection-conversion-storage-utilization system. The results of this study offer a simple design route for flexible energy storage devices.

The synchronized switch interface circuit is believed to boost piezoelectric power generation. The threshold voltage of electronic components causes rectification loss and delay in peak detection. This work reports a novel design of a mechanical rectification (MR) piezoelectric vibration energy harvester (MR-PVEH). Compact and low-loss MR is achieved by the double switch with five electrodes contact at the cantilever tip. The switch as a mechanical stopper also contributes to broadband performance. The saturation voltage and response frequency range can be adjusted in the modeling and simulation of nonlinear electromechanical coupling vibration. Self-adapting MR-optimized synchronous electric charge extraction (M-OSECE) circuit is also proposed with fewer electronic components in this article and shows an extra 60% increase in generated power than the traditional standard energy harvesting circuit (SEH) in the test. This novel design gives a promising solution for self-adapting synchronous switching in broadband piezoelectric vibration energy harvesting.

Compact reliable structure and strongly electromechanical coupling are hot pursuit in piezoelectric vibration energy harvester (PVEH) design. PVEH with static arc stopper makes piezoelectric stress uniformly distributed, and widen the frequency band by collision, but waste space. This paper proposes a hinged PVEH with two arc mass stoppers (AS-H-PVEH). Two arc stoppers as movable mass increase the vibration energy and also increase the effective electromechanical coupling coefficient to achieve strongly electromechanical coupling. It induces a high power output of 4.1 mW at 11.6-12.0 Hz for AS-H-PVEH prototype test in 0.2 g, and can withstand 4g acceleration vibration for 10 minutes without attenuation. To offset the resonance frequency increase caused by arc contact, the magnetic coupling and axial force effects are discussed in modeling and experiments. The design of arc stopper radius, nonlinear electromechanical coupling model, and system parameter identification method are presented in theory study. The varied mechanical quality factor and effective electromechanical coupling coefficient with displacement are considered in the modified model for the first time. The model obtained a good agreement under both sinusoidal frequency and shock excitation experiments. The power generation performance of AS-H-PVEH was verified under low frequency human motion. This research has important theoretical and application value for the performance optimization of PVEH with arc stopper.

Ambient vibrations from human activities, vehicle, and grid transmission lines' motion are low frequency, broadband, and random, which brings challenges in piezoelectric vibration energy harvester (PVEH) design. Nonlinear technology including magnetic coupling and impact has their limitation such as no broadband behavior in low excitation level. This paper proposed a hybrid magnetic coupling and impact enhanced broadband PVEH. For upward broadband, the impact design is adopted to provide overload protection for the piezoelectric cantilever beam while achieving frequency expansion with hardening stiffness. For downward broadband, the magnetic coupling enhancement is introduced, and the high voltage area gradually extends to the low frequency range. The frequency tuning mechanism brought about by the magnetically coupled axial force which helps to achieve frequency matching and energy harvesting to the ambient vibration. An inverted beam with large U-shaped mass block is adapted in PVEH to achieve low resonant frequency and high power output. The simulation of the lumped parameters model indicates the effect of impact and magnetic parameters on the broadband and output voltage characteristics. The proposed PVEH can achieve bidirectional broadband expending and high output power compared with conventional PVEH. The optimized PVEH can achieve 8.96 V (pure impact), 10.69 V (hybrid) as peak voltage and 1.004 mW (pure impact), 1.91 mW (hybrid) as average power under 0.5 g acceleration, 10 Hz fixed frequency excitation. Compared to the conventional linear design, the broadband performance of proposed PVEH in this paper can realize 8.5-14.1 Hz (56 %, pure impact) and 7.7-15.81 Hz (81 %, hybrid) respectively under acceleration of 0.5 g.

In the Internet of Things era, wearable electronics and sensors have become essential for health monitoring and human computer interaction. However, a continuous power supply is an urgent demand in the field of distributed sensing. Energy harvesting from daily human activities and its conversion into electricity are expected to replace traditional batteries and wearable power supplying electronic devices. This article reviews the electromagnetic, piezoelectric, and triboelectric energy harvesting technologies from human motions, including joint rotation, limb swing, force application, fold stretching, and organ motion. It also discusses and analyzes the advantages and disadvantages of various recently proposed human energy harvesters. In addition, possible applications of active sensing and wearable powered electronic devices driven by human body kinetic energy harvesting are provided. Finally, the concept of a human energy and information exchange center based on energy harvesting is proposed as a future prospect.

High power density is a hot pursuit in piezoelectric vibration energy harvester (PVEH) design. The assembly process has a great impact on the stiffness and damping of PVEH, and then affects the resonant frequency and output power of the system. The acrylic epoxy bonding assembly process has large damping and low stiffness. Here, we propose a PVEH inserted with aluminum alloy frame bonding assembly process, which has large stiffness, small damping, high resonant frequency of 125 Hz and high output power of 0.185 mW at 0.1g acceleration, with a high power density of 3.63 mWꞏcm-3ꞏg-2 in test.

Herein, a novel in-plane dual-axis micro-electro-mechanical system piezoresistive accelerometer was proposed based on theoretical and simulation analyses. Its self-support piezoresistive beam (SPB) possessed the features of force amplification and axial deformation to obtain high sensitivity. To clarify the influence of structural dimensions on the performance of the accelerometer and the pure axial-deformation condition of the SPB, a theoretical model was established to analyze mechanical behavior. The theoretical results were in well accordance with the simulation ones, displaying a maximum relative error of less than 10%. The theoretical and simulation results suggested that the accelerometer with thin and long support/hinge beams possesses a higher sensitivity but a lower frequency. However, the sensitivity and natural frequency increased simultaneously before the distance between SPB and support beam $D$ reached a certain value. The simulated longitudinal stress of SPB achieved the average value of 32.473 MPa, and the first-order natural frequency was nearly 13.6 kHz. Furthermore, the fabricated accelerometer was tested in a simple packaging case. The experimental results demonstrated that the proposed accelerometer had a measuring sensitivity of 0.198 mV/g/V with a maximum non-linearity of 1.00% FS and a resonant frequency of 12.93 kHz. The cross sensitivities were 11.93 and $15.97~\mu \text{V}$ /g/5V in the $y$ and $z$ axes, respectively, which were 1.21% and 1.61% of the prime-axis sensitivity. The zero offset with varying temperatures was 0.00296%/°C, and the zero drift in the long-term static stability test was 0.02 mV. All the results above revealed the promising application potential of the proposed accelerometer in vibration detection in the high-speed rotating spindle of machine tools. [2022-0057]

Vibrational triboelectric nanogenerators (V-TENG) can be used to harvest broadband vibration energy due to the nonlinear impact force induced by a stopper. However, V-TENGs with a single stopper have limited bandwidth and surface charge density, which has limited their application in wideband vibration energy harvesting. Herein, a V-TENG with two stoppers and a charge pumping effect is proposed for frequency band broadening and charge density enhancement. The theoretical analysis and experimental validation have indicated the V-TENG with two stoppers could improve the bandwidth by 75% compared with one stopper at a gap distance of 0.5 mm. Moreover, a charge pump can be constructed with two output channels, which has improved surface charge density by about 14 times. With the frequency varying from 18 to 38 Hz, the V-TENG can continually power 400 LEDs and charge a commercial capacitor quickly. This work has shown an encouraging method for enhancing the performance of V-TENGs, which also has great prospects in harvesting wideband vibration energy from machines, cars, ships, and human motions for self-powered electronics.

Herein, hybrid micro-supercapacitors (MSCs), consisting of positive CoNi layer double hydroxides (LDHs) decorated on carbon nanotubes (CoNi LDHs@CNTs) and negative CNT electrodes, were assembled by facile drop-coated and electrodeposition methods. The as-fabricated MSCs were optimized in view of electrochemical performance, and the CoNi LDHs-2@CNTs//CNT MSC exhibited a favorable performance and was thus chosen to be the candidate for MSC device package. The packaged CoNi LDHs-2@CNTs//CNT MSC demonstrated a large areal capacitance of 11.0 mF·cm-2 at a current density of 0.08 mA·cm-2, a good rate performance (56% areal capacitance retained at a higher current density of 0.4 mA·cm-2), and a favorable cycling stability and reversibility (92% of the original areal capacitance was retained after 5000 cycles). Furthermore, the MSC device recorded an energy density of 1.5 μWh·cm-2 at a power density of 42.5 μW·cm-2 and was successfully applied for the storage of energy supplied by solar cells to operate a red light-emitting diode. All these findings demonstrated the promising practical energy storage application of the as-fabricated hybrid MSC devices in the construction of sunlight-powered energy storage systems.

Triboelectric Nanogenerators (TENGs) based on spring-assisted structures play a central role in scavenging vibrational energy that is widely available in the natural environment. However, they suffer from difficulties in adjusting the stiffness and bonding the springs to the triboelectric layer. Here, a kirigami-inspired TENG (KI-TENG) with a kirigami structure is demonstrated, which can be used as an ultra-wide-band vibrational energy harvester and self-powered acceleration sensor. The triboelectric layer of the KI-TENG can be easily processed into the kirigami structure with one or two-degree-of-freedom by laser cutting technology. The frequency responses of the KI-TENG under the influence of mass, acceleration, and initial distance are investigated in detail to optimize the structural design. With optimized structural parameters, the KI-TENG can not only harvest broadband vibration energy from 2 to 49 Hz in vertical vibration state but also obtain high output performance over a wide frequency range in horizontal vibration state. Moreover, the KI-TENG can be used as a sensor measuring acceleration from 1 to 9 m/s(2). This work demonstrates a compact TENG coupled with the kirigami structure for energy harvesting and active sensing, which has great prospects in intelligent plants, artificial intelligence, and the internet age.

In this short paper, four ideas of narrow band design of FBAR filter are discussed, including adding support layers, varying the area of series and parallel resonant units, connecting inductors in series and parallel, and varying the thickness of the top electrodes of different resonant units. A narrowband FBAR filter with center frequency of 2210 MHz, in-band loss of 1.6 dB, bandwidth of 10 MHz, out-of-band suppression of more than 34 dB is obtained in ADS simulation.

In view of the large scale and distributed characteristics of transformers, which lead to inconvenient manual inspection and state monitoring, and the limited energy of batteries restricting the development of wireless sensor nodes (WSNs), WSNs powered by solar energy are a promising approach. We propose a power management circuit for dual energy storage and dual-channel charging of a supercapacitor and a lithium battery with four modes to deal with the different charging currents of photovoltaic power generation under strong and weak light illumination, as well as the time mismatch between the energy harvesting power and WSN consumption power. We designed a low-power WSN with temperature, humidity, vibration, and illumination sensors in a low-duty-cycle operation mode with an average current consumption of 4.96 mA. Our solar power management circuit with undervoltage lockout (UVLO), maximum power point tracking (MPPT), quick charging, and a sustainable output characteristic is designed by LTspice simulation and verified by experiment in alternating light outdoors. The experiment demonstrates sustainable autonomous wireless sensing by dual charging and the feasibility of our storage design for solar energy harvesting, indicating its potential application in grid transformers.

The traditional single degree of freedom linear piezoelectric vibration energy harvester (PVEH), such as the cantilever type, mainly works and resonates in a single direction and at a single frequency. To adapt broadband and bidirectional ambient vibration, this paper designs and compares two PVEHs of L-shaped beam and U-shaped beam through COMSOL simulation and prototype test. FEA modeling is introduced for accurate structure design with modal analysis, voltage frequency response analysis, and proof mass analysis with multiphysics electromechanical coupling simulation. Two PVEH prototypes with different gravity angles and clamping angles are tested at 0.1 g acceleration to find the optimal angle for maximum output power. The best clamping angle of L-PVEH is 135° with RMS power of 0.3 mW at 7.9 Hz, and that of U-PVEH is 45° with RMS power of 0.4 mW at 5.0 Hz. The proposed U-PVEH shows more advantages in low broadband and bidirectional vibration energy harvesting.

To convert as much vibration energy as possible into electrical energy, the design of a high-performance piezoelectric vibration energy harvester (PVEH) has been studied widely in recent years. To overcome the low energy utilization of a traditional piezoelectric cantilever by inhomogeneous strain, a uniform stress distribution of bimorph by an ARC mechanical stopper structure has been designed for maximum piezoelectric vibration energy harvesting. Deflection equations and their simulation at the first-order modal of two classic bimorph cantilever beam models, with transverse tip force and with equal curvature, are derived based on the Euler–Bernoulli beam assumption. Piezoelectric energy from a beam model with equal curvature is four times that of a cantilever beam model with transverse tip force at the theoretical level. The nonlinear frequency response performance of bimorphs by an ARC mechanical stopper and point stopper model could be observed by the numerical simulations of the lumped parameter electromechanical model. PVEH prototypes were manufactured by 3D printing and tested. To verify the high-power generation capacity, PVEH with an ARC stopper has 1.756 times more voltage than that of a PVEH with a point stopper.

Piezoelectric vibration energy harvester (PVEH) is a promising device for sustainable power supply of wireless sensor nodes (WSNs). PVEH is resonant and generates power under constant frequency vibration excitation of mechanical equipment. However, it cannot output high power through off-resonance if it has frequency offset in manufacturing, assembly and use. To address this issue, this paper designs and optimizes a PVEH to harvest power specifically from grid transformer vibration at 100 Hz with high power density of 5.28 μWmm−3g−2. Some resonant frequency modulation methods of PVEH are discussed by theoretical analysis and experiment, such as load impedance, additional mass, glue filling, axial and transverse magnetic force frequency modulation. Finally, efficient energy harvesting of 6.1 V output in 0.0226 g acceleration is tested in grid transformer reactor field application. This research has practical value for the design and optimization process of tunable PVEH for a specific vibration source.