Narrow Results

During the last years, the design and production of self-powered engineering structures gained extensive attention due to the shortage of nonrenewable energy resources and the increase in fossil fuel prices. To this end, the current numerical study focused on assessing the forced vibration behavior and energy harvesting capability of a silicon microbeam reinforced with chopped fiber rods (CFRs). This topic is important because it offers a novel approach to generate sustainable energy from ambient vibrations, addressing the growing demand for renewable energy sources while advancing structural health monitoring and smart materials technology. The piezoelectric patch is located at the top surface of the microbeam and is under the distributed harmonic force. The related governed relations are derived using the new theory of the five-parameter beam model, which also accounted for the Poisson effect, and solved by adopting the Galerkin method. The microscale effects are taken into account by employing strain gradient theory. Moreover, the effects of the top and bottom surfaces have accounted for the microbeam using Gurtin and Murdoch’s theory. The outcomes of this research indicated that utilizing narrow-short length piezoelectric patches for Silicon microbeams yields the highest available output voltage. Compared to the homogeneous porosity distribution case, as the porosity coefficient reduced in the bottom and top surfaces of the microbeam, the voltage initial rise point decreased by about 13%. By increasing the porosity coefficient to 0.9, both voltage and displacement initial rise points are increased respectively by approximately 32% and 890%. As the piezoelectric patch thickness is decreased from 8$\mu$m to 6$\mu$m while the strain gradient theory is utilized, voltage and displacement initial rise points are increased respectively about 1066.67% and 1200%. Also, a simultaneous increase in CFRs vol. fraction from 5% to 10% and Silicon microbeam thickness from 7$\mu$m to 8$\mu$m caused about 37% improvement in dynamic deflections.

In this paper, an inertial amplifier and a quasi-zero stiffness system are combined to propose an energy harvesting system that can change the dynamic mass of the system. By adjusting the inertial amplifier, it is possible to change the distribution of its chaotic region and the effective range of energy collection. The kinetic equations of the system with an inertial amplifier under a combination of multiple harmonic excitations are developed. Based on this, the system was simulated and tested and the Lyapunov exponent, the RMS value of the induced voltage and the coexisting basins of attraction were plotted. Subsequently, the best optimization solution to improve the energy harvesting efficiency of the system was identified. In addition, the system was tested for impulse excitation based on the given coexisting basins of attraction. The simulation results show that the inertial amplifier can effectively improve the range of the energy harvesting region and the distribution of the chaotic region in the system ground under ultra-low-frequency vibration. The initiation of impulse excitation can change the energy harvesting performance of the system to a great extent.

This paper investigates the stochastic nonlinear dynamic response of a single-degree-of-freedom dielectric elastomer generator under the combined action of harmonic excitation and stochastic disturbance. First, the nonlinear vibration model of a single-degree-of-freedom dielectric elastomer generator is established. The average method and fourth-order Runge–Kutta method are used to analyze the influence of pre-stretching, the initial membrane length, the charge amount, and the external excitation amplitude on the system response. Considering stochastic disturbance, the stochastic average method is applied to determine the probability density function (PDF) of the system’s steady-state response, and Monte Carlo numerical simulations are compared with the theoretical calculations for verification. The oscillation amplitude of the steady-state response can be increased by increasing the pre-stretching, harmonic excitation amplitude, and stochastic disturbance intensity. In the case of stochastic disturbance, as the intensity of the disturbance increases, the system becomes more likely to exhibit large amplitude responses for longer durations.

Ocean waves are abundant in energy; however, they also cause ships to sway and can disrupt the operation of precision equipment. Harvesting energy from ocean waves and isolating vibrations in marine precision equipment have long posed significant challenges due to the inherently low-frequency nature of ocean waves. This study proposes a dynamic-constrained nonlinear (DCN) stiffness method for low-frequency energy harvesting and vibration isolation. A generalized mathematical model of the DCN stiffness system is established, and its semi-analytical solution is derived using the harmonic balance method and the arc-length extension method. Finally, various application scenarios for energy harvesting and vibration isolation using the nonlinear stiffness method are explored. The results demonstrate that the DCN stiffness method can significantly enhance the performance of low-frequency wave energy, capture and provide excellent low-frequency vibration isolation. Notably, this method exhibits a strong adaptive capability to excitation compared to traditional nonlinear stiffness methods.

Vertical ZnO nanorods (NRs) were grown on flexible plastic substrates at low temperature using hydrothermal synthesis method. An energy scavenging piezoelectric device was constructed using two flexible substrates with the NR sides facing each other providing a maximum open-circuit voltage of 1.4 V (peak). Two sets of three piezoelectric devices connected in series in a half-diode-bridge circuit configuration was demonstrated to turn on a commercial red LED.

An inductorless power converter for low-power energy harvesting is presented. The power converter for energy harvesting is employed to maximize power extraction from energy sources. The power converter is based on a capacitive boost converter which is divided into two stages; a number of first-stage in parallel and shared-stage. The first-stage maximizes power extraction from the energy source while the shared-stage operates as a conventional charge pump. For not only low-power energy source but also high-power energy source, the maximum power extraction is targeted by the proposed converter. The extracted power from energy sources enhances by range from 117% to 161% over the conventional design. The output current of the proposed converter with three first-stages is improved by 183% over conventional converter. The peak efficiencies achieved with three and one first-stage are 53.3% and 38.5% for the proposed and the conventional converters, respectively. The peak end-to-end efficiency is enhanced by 198% as compared to the conventional converter. The proposed inductorless power converter has been implemented on a 0.13μm CMOS process.

This publication considers the use of a variety of additive manufacturing techniques in the development of wireless modules and sensors. The opportunities and advantages of these manufacturing techniques are explored from an application point of view. We discuss first the origami (4D-printed) structures which take advantage of the ability to alter the shape of the inkjet-printed conductive traces on the paper substrate to produce a reconfigurable behavior. Next, focus is shifted towards the use of additive manufacturing technology to develop skin-like flexible electrical system for wireless sensing applications. We then discuss the development of a fully flexible energy autonomous body area network for autonomous sensing applications, the system is fabricated using 3D and inkjet printing techniques. Finally, an integration of inkjet and 3D printing for the realization of efficient mm-wave 3D interconnects up to 60GHz is discussed.

This publication provides an overview of additive manufacturing techniques including Inkjet, 3D and 4D printing methods. The strengths, opportunities and advantages of this array of manufacturing techniques are evaluated at different scales. We discuss first the applicability of additive manufacturing techniques at the device scale including the development of origami inspired tunable RF structures as well as the development of skin-like conformal, flexible systems for wireless/IoT, Smartag and smart city applications. We then discuss application at the package scale with on package printed antennas and functional packaging applications. Following this, there is a discussion of additive manufacturing techniques in applications at the die scale such as 3D printed interconnects. The paper is concluded with an outlook on future advancements at the component scale with the potential for fully printed passive components.

The proposed study presents an electromagnetic (EM) energy harvesting and density sensor application based on a perfect metamaterial absorber (MA) in microwave frequency regime. In order to verify the absorption behavior of the structure, its absorption behavior is experimentally tested along with the energy harvesting and sensing abilities. The absorption value is experimentally found 0.9 at the resonance frequency of 4.75 GHz. In order to harvest the EM energy, chips resistors are used. In addition, the suggested model is analyzed for its dependency on polarization angles. The results show that the perfect MA can be easily and efficiently used for EM energy harvesting applications. Moreover, as an additional feature of the model, we also realized a density sensor application. It can be seen that this structure can be used as a multi-functional device and configured for many other sensing applications.

Harvesting energy from the surrounding environment through piezoelectric conversion is a promising method for implementing self-sustained low-power devices. To date, most piezoelectric energy harvesters (PEHs) developed can only scavenge energy from the unidirectional mechanical vibration. This deficiency severely limits the adaptability of PEHs because the real-world excitations may involve different mechanical motions and the mechanical vibration may come from various directions. To tackle this issue, we proposed a multipurpose PEH, which is composed of a ferromagnetic ball, a cylindrical track and four piezoelectric cantilever beams. In this paper, theoretical and experimental studies were carried out to examine the performance of the multipurpose PEH. The experimental results indicate that, under the vibrations that are perpendicular to the ground, the maximum peak voltage is increased by 3.2 V and the bandwidth of the voltage above 4 V is expanded by more than 4 Hz by the proposed PEH as compared to its linear counterpart; the maximum power output of 0.8 mW is attained when the PEH is excited at 39.5 Hz. Under the sway motion around different directions on the horizontal plane, significant power outputs, varying from 0.05 mW to 0.18 mW, are also generated by the multipurpose PEH when the sway angle is larger than 5${}^{\circ }$ and the sway frequency is smaller than 2.8 Hz. In addition, the multipurpose PEH demonstrates the capacity of collecting energy from the rotation motion, and approximately 0.14 mW power output is achieved when the rotation frequency is 1 Hz.

Scavenging energy from human motion through piezoelectric transduction has been considered as a feasible alternative to batteries for powering portable devices and realizing self-sustained devices. To date, most piezoelectric energy harvesters (PEHs) developed can only collect energy from the uni-directional mechanical vibration. This deficiency severely limits their applicability to human motion energy harvesting because the human motion involves diverse mechanical motions. In this paper, a novel PEH is proposed to harvest energy from the motion of human lower limbs. This PEH is composed of two piezoelectric cantilever beams, a sleeve and a ferromagnetic ball. The two beams are designed to sense the vibration along the tibial axis and conduct piezoelectric conversion. The ball senses the leg swing and actuates the two beams to vibrate via magnetic coupling. Theoretical and experimental studies indicate that the proposed PEH can scavenge energy from both the vibration and the swing. During each stride, the PEH can produce multiple peaks in voltage output, which is attributed to the superposition of different excitations. Moreover, the root-mean-square (RMS) voltage output of the PEH increases when the walking speed ranges from 2 to 8 km/h. In addition, the ultra-low frequencies of human motion are also up-converted by the proposed design.

A new metamaterial absorber (MA) having distinct properties than those given in the literature is investigated. Although several designs have been studied for achieving absorption characteristics in single-band, dual-band and multiple bands within the whole spectrum of solar light, there has been limited number of researches examining the broadband MA in the visible light section of the spectrum. The designed structure is composed of the combination of three layers having different thicknesses including a metallic substrate, dielectric and a metal layer. Due to the sandwich-like structure, it can support the plasmonic resonance. The proposed structure, which provides a maximum absorption level of 99.42% at 579.26 THz, has a high absorption rate of 99% between the frequency band 545 and 628 THz. Numerical results indicate that the proposed structure has perfect absorption which is greater than 90.98% through the whole working frequency band. The dependency of the designed structure on the polarization angle is investigated for different incident angles with TE and TM polarizations as well as the TEM mode. In addition to its potential applications such as solar cells and cloaking, the designed structure can also be considered as a color sensor and an optical frequency sensor.

In this study, a novel metamaterial absorber (MA) is designed and numerically demonstrated for solar energy harvesting. The structure is composed of three layers with different thicknesses. The interactions of three layers bring about the plasmonic resonances. Although the main operation frequency of the structure is chosen between 430 and 770 THz, which is the visible light regime, the proposed structure is also investigated in the ultra-violet (UV) region. One can see from the results that the proposed structure carries nearly perfect absorption capacity that is more than 91% at the whole visible light spectrum. The proposed structure even has the absorption capacity of 99% between 556 and 657 THz. In addition, the designed MA is also investigated in terms of its polarization and angle independency. Results show that the proposed structure is independent from the polarization and incident angles. Lastly, the designed structure can be considered to be used in solar energy applications as a harvester since it has an ultra-broadband absorption characteristic in visible light regime.

In the present paper, guided four beam (G4B) piezoelectric transducers with enhanced sensitivities have been designed. Based on the suggested G4B structures, piezoelectric energy harvesters (PEHs) and acceleration transducers with higher voltages than their previously reported counterparts and with lower displacements than the single-cantilever PEHs (SC-PEHs) have been proposed. We have shown that it is possible to arrive at much more output voltages in comparison with the conventional PEHs by redesigning the structure of the cantilever beams. In 1 g acceleration, the maximum output voltage obtained from the proposed PEHs has been 13.49 V whereas the output voltage for the conventional G4B-PEH is 2.87 V. This paper for the first time proposes G4B-PEHs with smaller displacements and larger voltages compared to a SC-PEH. The same G4B framework has been studied as a piezoelectric acceleration transducer. The effect of piezoelectric length on the extracted voltage in both unimorph and bimorph cantilevers has been discussed and the optimized length has been calculated. An analytical method is developed to compute the resonance frequencies of different beam shapes whose results are in a good agreement with numerical simulations.

This study is focused on obtaining a comprehensive understanding of the influence of geometry — size and shape — on the indentation response of a large set of piezoelectric small-volume structures such as nanoislands, nanowires and thin films. Using three-dimensional finite element modeling, the complex interplay between the properties of the indented materials and the indentation response of piezoelectric micro- and nanostructures is analyzed. It is demonstrated that: (i) In general, the indentation response of thin film structures tends to be much stiffer than that of the piezoelectric nanoisland and nanowires, resulting in more charges being generated during the indentation of the thin-film structures. (ii) The indentation of the piezoelectric nanowire structures with a spherical indenter whose radius is substantially larger than the width of the nanowires, introduces a combination of deformation modes — structural bulging and indentation-induced compression. The combined effect of two deformation modes produces a maximum in the charges generated during the indentation process on a nanowire structure with a particular aspect ratio (i.e., wire width/wire height), which is greater than that produced in nanoisland and thin films structures with the same characteristic size.

A low-frequency vibration energy generator has been proposed by using a locally resonant phononic crystal plate which has spiral beams connecting the scatterers and the matrix. Finite element analysis shows that at the flat bands frequencies of the phononic crystal, locally resonant leads to the spiral beams having strong deformations which are perpendicular to the plate. A designed structure with three PC cells arranged in the same direction was adopted for the experiments. Piezoelectric patches were adhered on the end of the spiral beams and then the collected vibration energy could be converted into electric energy. The maximum single-channel output voltage which reached as much as 13 V was obtained at the first flat band frequency 29.2 Hz in the experiment. Meanwhile, in the low-frequency range of 0–500 Hz, it showed that the piezoelectric transformation could be conducted at a dozen of resonant frequencies. Furthermore, through modulating the structure parameters, this phononic crystal has the potential to realize broad-distributed vibration energy harvesting.

With the increasing development of wireless sensor network (WSN), power supply for WSN nodes had attracted increasing attention, and the energy harvesting system based on Karman vortex street has been widely used in underwater WSN. But the research of the influences of affecting factors towards the energy harvesting system is yet to be completed. So, in this paper, an underwater flow-induced vibration energy harvesting system based on Karman vortex street was proposed and tested. The influence of bluff body geometry and flow velocity towards the performance of the energy harvesting has been researched. The results showed that the output voltage increased as the diameter of bluff body and the water velocity increase. The power generation efficiency was the best when the shape of bluff body was circular.

An electromagnetic generator with magnetic spring and ferrofluid is proposed and designed to harvest low-frequency vibration energy from human body motion. The magnetic spring is formed by gravity and magnetic repulsive force between the fixed and the moving permanent magnets. The ferrofluid is aggregated at both ends of the moving permanent magnet, and the ferrofluid layer between the plastic tube wall and permanent magnet can remove the solid-friction as a fluid lubricant. The electromagnetic generator is used to harvest human motion energy. The measured average load powers of electromagnetic generator with ferrofluid 1.5 g from human body motion are 1.3 mW and 7.5 mW during walking and low running, respectively, which is 30 times more than the measured average power of generator without ferrofluid.

This paper describes an energy management system and an algorithm for an energy-aware operation. The system obtains energy from an energy harvester and manages the energy adaptively according to the monitored energy status. Based on a low-power microcontroller, the system controls the energy harvester so that it always harvests energy at maximum power and tracks it when the operating condition changes. It also controls the power consumption of all parts of the system so that they are adjusted dynamically for the management of harvested or stored energy. To manage the energy transfer to a battery, a DC–DC converter, called the energy management IC, is optimized for the operating voltage control of the harvester. In an experiment using an energy harvester and a battery modified for the system, the energy management IC fabricated in a 0.18 μm process maximizes the energy transfer power with a simple, low-power algorithm. The proposed system is verified to be more efficient for low-energy harvesting by the adaptive energy and power management.

Fault tolerance and energy have become important design issues in multiprocessor system-on-chips (SoCs) with the technology scaling and the proliferation of battery-powered multiprocessor SoCs. This paper proposed an energy-efficient fault tolerance task allocation scheme for multiprocessor SoCs in real-time energy harvesting systems. The proposed fault-tolerance scheme is based on the principle of the primiary/backup task scheduling, and can tolerate at most one single transient fault. Extensive simulated experiment shows that the proposed scheme can save up to 30% energy consumption and reduce the miss ratio to about 8% in the presence of faults.