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Nonlinear energy sink (NES) as a new type of dynamic absorber has received widespread attention due to its broadband vibration suppression capability, but it has a certain requirement of energy triggering threshold. In this work, a bistable NES-based piezoelectric system with combined damping (BCPNES) and low threshold requirement is proposed. Electromechanical-coupled equations for the nonlinear oscillator coupled with BCPNES (NO-BCPNES) are established. The vibration suppression and vibration energy harvesting performance for the coupled system are investigated numerically and analytically. The frequency–energy plots of the conservative system are investigated using the complex-variable averaging method and the electromechanical decoupling method. The influence of circuit parameters on the target energy transfer threshold and harvested energy is discussed through the equivalent stiffness and damping of the circuit. The vibration suppression performance and the target energy transfer characteristics are analyzed in terms of the time–history response, the time–frequency response and the slowly varying dynamic flow, respectively. The results show that the electromechanical coupling coefficient affects the skeleton curve of frequency–energy plots in the form of equivalent stiffness. The NO-BCPNES system exhibits higher energy dissipation performance and better targeted energy transfer form under various excitations. From the phase perspective, NES-based piezoelectric system achieves vibration suppression of the main structure through the phase locking phenomenon. The mechanism of the influence of piezoelectric device parameters on the energy harvesting performance of the systems is clarified.

With the development of inkjet-/3D-/4D-printing additive manufacturing technologies, flexible 3D substrate with complex structures can be patterned with dielectric, conductive and semi-conductive materials to realize novel RF designs. This paper provides a review of state-of-the-art additively manufactured passive RF devices including antennas and frequency selective surfaces (FSS), couplers, where origami-inspired structure enables unprecedented capabilities of on-demand continuous frequency tunability and deployability. This paper also discusses additively manufactured active RF modules and systems such as inkjet printed RF energy harvester system with high sensitivity and efficiency for Internet of Things (IoT), smart cities and wireless sensor networks (WSN) applications, inkjet-printed RF front ends, and inkjet-printed mm-wave backscatter modules.

In this paper, for the first time, a new design for a MEMS cantilever-based energy harvester (EH) has been proposed which takes advantage of two engineered piezoelectric layers. The output voltage of the EH has been increased by the aid of making grooves in the piezoelectric layers. By application of the grooves in the piezoelectric layers, the sensitivity of the cantilever as the vibration sensor or the EH has been improved. Results have shown that these grooves can increase the output voltage and decrease the resonance frequency which are desired changes in designing EHs. The single and double groove bimorph cantilevers have been compared and discussed. The position, length and depth of the grooves have been used as optimization parameters and consequently an optimal design has been proposed at the end of the paper. In the optimal design the top and the bottom piezoelectric layers have not covered the entire beam and have different lengths to produce maximum voltage. By means of groove engineering, we could rise the voltage from 5.395 V to 28.35 V which is considered a great improvement compared to other structures reported previously.

Modeling and analysis of a MEMS piezoelectric (PZT-Lead Zirconate Titanate) unimorph cantilever with different substrates are presented in this paper. Stainless steel and Silicon $〈110〉$ are considered as substrate. The design is intended for energy harvesting from ambient vibrations. The cantilever model is based on Euler–Bernoulli beam theory. The generated voltage and power, the current density, resonance frequencies and tip displacement for different geometry (single layer and array structure) have been analyzed using finite element method. Variation of output power and resonant frequency for array structure with array elements connected in parallel have been studied. Strain distribution is studied for external vibrations with different frequencies. The geometry of the piezoelectric layer as well as the substrate has been optimized for maximum power output. The variation of generated power output with frequency and load has also been presented. Finally, several models are introduced and compared with traditional array MEMS energy harvester.

This paper presents the design and implementation of an RF energy harvester system at 5.8GHz for low-power wireless transmission applications. The potential application of the proposed system is to wirelessly power sensor nodes. First, a design methodology of the rectifier based on a theoretical approach is presented. The simulation results show an excellent correlation with the theoretical ones, proving the accuracy of the proposed design methodology. A prototype is fabricated and the simulation results are validated by the measurements. Then, the rectenna is combined to a commercial power management circuit and a load which emulates the behavior of a sensor. The power management circuit boosts and regulates the output DC voltage as well as stores the collected energy into a capacitor. Finally, the complete system is experimentally tested and excellent performances are demonstrated. The efficiency of the RF energy harvester is 24% at $-$10dBm input power and 47% at $-$5dBm input power which are the highest reported measured efficiencies at this frequency and at those power levels. The complete rectenna system is able to harvest 4.62mJ in 40 s and 192s for $-$6dBm and $-$10dBm input power, respectively allowing us to power wirelessly low-power electronic devices.

Nonlinear energy harvesters were found to be sensitive to excitation conditions. In order to reveal the influence mechanism of the excitation condition on the energy harvesting performance, this paper presents an uncertainty analysis for nonlinear monostable energy harvesters (NMEHs). An improved interval extension based on the second-order Taylor’s series is presented as a new uncertainty analysis method. A mathematic example is used to demonstrate that the bounds of responses based on this method are more accurate than the classic interval extension when the dependence of the response on the uncertain variable is nonlinear. Meanwhile, the results from the Monte Carlo simulation are used to verify the accuracy of the proposed method. It is confirmed that the proposed method is suitable for quantifying the propagation of the uncertain level and frequency of the excitation for the NMEH. The results show that the output voltage of the NMEH is more sensitive to the frequency than the level of excitation, for which the influence mechanism is revealed.

In this paper, it has been demonstrated that the tri-stable energy harvesters are more efficient than the bi-stable and mono-stable harvesters in energy harvesting. The oscillators of energy harvesters can be designed as a vibration absorber to attenuate the vibration of the primary system. This paper presents a combined vibration absorber and energy harvester (VAEH) system for simultaneous vibration control and energy harvesting, and the dynamic performances of the VAEH with two magnet arrays of the same geometric parameters, but opposite polarity external magnets, are studied. The mathematical model of the tri-stable VAEH is established, by which the dynamic and energetic characteristics of the VAEH system are obtained. It is found that the potential barrier and potential well depth of the repulsive magnet array are greater than the attractive one, reducing the voltage harvesting efficiency under harmonic and impulsive excitation. Both the amplitude and frequency of excitation are crucial to the dynamic response of the VAEH system. The attractive VAEH performs better than the repulsive VAEH in vibration suppression, especially for high impulse input. From the frequency response of the system, the vibration of the primary system is shown to be magnified at certain frequencies. The magnified primary system vibration and the harvested voltage can be attenuated by increasing the VAEH damping, which is a critical parameter to balance the weight of vibration suppression and energy harvesting. The attractive VAEH designed in this paper performs better than the repulsive one in vibration suppression and energy harvesting.

The posture monitoring of basketball is very important for daily training and skill improvement, and the research and development of related sensor technology is extremely urgent. Here, we design a box-shaped triboelectric nanogenerator (BS-TENG) to harvest mechanical energy and serve as the smart sport sensor. The BS-TENG can realize two working modes, leading to harvest both active and passive mechanical energy. This unique box structure enables to be integrated on the floor, which can play the role of smart sport floor. Furthermore, under different basketball posture (such as walk with the ball, dribble and shoot), the BS-TENG can generate different voltage signal, which make BS-TENG can serve as the self-powered sport sensor. We think this design will promote the development of intelligent sports devices.

In this paper, a nonresonant electromagnetic micro-generator is proposed. The proposed device is capable of converting nonresonant environmental vibrations to electrical power. The energy harvester could generate output power from heartbeat, human leg and arm motion. The proposed energy harvester uses Frequency up CONVersion technique (FCONV) to improve the bandwidth of the device. The results approve the high bandwidth of the proposed method. The micro-generator is designed by micro-electro-mechanical systems (MEMS) methods. Consequently, the volume of the power harvester is minimized and power density is maximized. The new configuration of energy harvester with imposed motion trigger is proposed. Output power, bandwidth and performance of the designed micro-power harvester are discussed. The proposed micro-generator exhibits higher bandwidth in comparison with resonant, multi-resonant and tunable bandwidth structures. The nonresonant device is designed using FCONV to convert 1–3Hz heartbeat mechanical vibrations to output electrical power. The optimum upconverted mechanical vibration frequency is 60Hz and the output voltage frequency is 120Hz. The peak output electrical power of FCONV is 17.75$\mu$W. For 1Hz, 2Hz and 3Hz mechanical vibration with imposed motion trigger, average output powers are 1.60$\mu$W, 3.81$\mu$W and 5.19$\mu$W, respectively. The achieved results illustrate that the proposed FCONV method exhibits better and wider frequency response in comparison with different methods. The designed device can be utilized to supply implantable biomedical sensors. Also, the heat generation of the device is studied. The results illustrate that the temperature rise of the micro-generator remains in the normal human body temperature range. Hence, the proposed power harvester is biocompatible.

With the development of inkjet-/3D-/4D-printing additive manufacturing technologies, flexible 3D substrate with complex structures can be patterned with dielectric, conductive and semi-conductive materials to realize novel RF designs. This paper provides a review of state-of-the-art additively manufactured passive RF devices including antennas and frequency selective surfaces (FSS), couplers, where origami-inspired structure enables unprecedented capabilities of on-demand continuous frequency tunability and deployability. This paper also discusses additively manufactured active RF modules and systems such as inkjet printed RF energy harvester system with high sensitivity and efficiency for Internet of Things (IoT), smart cities and wireless sensor networks (WSN) applications, inkjet-printed RF front ends, and inkjet-printed mm-wave backscatter modules.

In order to achieve low-frequency, multi-direction vibration energy reliably recovery and utilization, a multi-direction vibration energy harvester (MDVEH) based on the piezoelectric effect is presented. This paper introduces mainly the structural design, working principle, and test of the prototype. Theoretical analysis shows that the MDVEH's electric performance is commonly decided by the environmental vibration frequency, amplitude, proof mass, structure parameters of piezoelectric vibrator, spring stiffness and so on. It can achieve its intended function only when all factors are configured appropriately. Test prototype is fitted to the shaker table and tested in different excitation frequencies, amplitudes and proof masses. The test shows that the MDVEH can work in different directions of vibration, there is an optimum operating frequency about 13Hz, in which MDVEH can generate the maximum voltage about 15V, and within a certain range, the output voltage increases with the rise of the proof mass and the amplitude.