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This paper proposes a new design of bimorph-type electrothermal actuators based on flexible Ni-Co substrates and describes the results of the finite element method (FEM) simulation and performance evaluation of the actuators. In the design of the actuators, a multilayer structure consisting of an adhesion layer, two insulation layers, and a Pt (platinum) heater layer was formed on the Ni-Co flexible substrate that was patterned in an individual shape. The thin-film actuators proposed in this study could be detached from a Si carrier wafer and adhered to other micro or macrostructural elements. To investigate the temperature distribution and mechanical behavior of the actuators, multiphysics FEM simulations combining electrothermal and static structural analyses were carried out. The actuators were fabricated using conventional microfabrication and electroplating technologies on Si carrier wafer; then, the actuators were peeled off from the carrier wafer using the release process proposed in this paper. After fabricating the actuators, the deflection of their tips was evaluated and compared with that obtained from the FEM simulations.

Piezoelectric energy harvesting (PEH) provides an essential mode for the transformation of mechanical vibration to electrical form for providing continuous power to wireless sensor nodes in today’s...

A shape memory alloy (SMA) bimorph actuator is a composite structure composed of flexible polyimide substrate and SMA thin film deposited using thermal evaporation technique. In this work, the substrate thickness in the range of 25 - 75 mm was selected for the development of CuAlNiMn SMA bimorph actuator. An investigation on the control behavior of copper based SMA bimorph towards the development of micro positioning system has been performed. The actuation behavior of the SMA bimorph was studied using electrical actuation. Subsequently, a proportional integral derivative (PID) controller was designed to control the bimorph actuator with proper tuning of gain parameters. The displacement of the bimorph actuator was controlled through dedicated experimental setup consisted of laser displacement sensor, data acquisition system and LabVIEW software. The CuAlNiMn SMA bimorph actuator resulted in a satisfying control performance which can be extended to MEMS applications. A preliminary prototype of the SMA bimorph actuator based micro positioning system has been developed.

We propose reconfigurable metamaterials with multiband resonance in the terahertz (THz) frequency range. By modifying the pattern width and gap of metamaterial, these designs exhibit the characteristics of polarization-dependence, dual-band resonance, and triple-band resonance. Two cantilever metamaterial (CM) devices are demonstrated by using micro-electro-mechanical system (MEMS) based bimorph cantilevers array, which can be deflected toward the out-of-plane direction. The measured transmission spectra are greatly agreed well with the simulation results. By applying different direct current (DC) bias voltages, the bending degree and electromagnetic response of CM device could be controlled. The multiband resonance can be tuned in the range of 0.33 THz by applying a DC bias voltage of 30 volts. The relationship of the resonant shifts and the applied DC bias voltages is quite linear, which can assist the device to be more controllable and applied in more fields. Such designs are promising to be used in various applications, such as frequency-selective detectors, multispectra imagers, and multifunctional switches in the THz frequency range. [2020-0236]

Macro-Fiber Composite bimorph is a kind of piezoelectric actuator that allow large bending deformation. However, macro-fiber composites exhibit strong stiffness nonlinearity in their operation range, so it is difficult to accurately estimate their large deformation behavior based on a linear constitutive model. In addition, the macro-fiber composites have active and inactive parts, that significantly differ in their material sizes and properties, so it is not reasonable to consider them as uniform material. Thus, it is necessary develop an accurate modeling and analysis method for the large deformation macro-fiber composite structures. First, the mixing rules are extended to derive the three-dimensional homogenized mechanical and electrical parameters of the macro-fiber composite active part; based on these parameters, the actuation results of linear finite element model is in good agreement with the official data. Then a finite element model of the axially compressed macro-fiber composite bimorph is established, the bilinear tensile stiffness of macro-fiber composite is realized by secondary development in ANSYS. Comparison with the experimental results reveals high accuracy of the established finite element model. Thus, the developed method can be effectively used for the performance evaluation and design of the macro-fiber composite devices with large deformation.

A novel process was developed for the fabrication of 5–50 µm lead zirconate titanate (PZT) thick films on metal substrates. Tape cast PZT with a methyl cellulose binder was burned out at 275 °C, humidified, and then partially densified at 300 °C by cold sintering with a wet lead nitrate liquid phase. Lamination of the green tape on dense metal foils led to incomplete densification due to constrained sintering. However, when metal foils were replaced with tape cast Cu, fully sintered PZT/Cu/PZT composites were acquired after a secondary heat treatment at 800 °C. The PZT films has a relative permittivity over 500 and a loss tangent ~12% at 100 Hz because of a Cu2O interface between the PZT and Cu presumably formed during the cold sintering process. The polarization-electric field hysteresis loop shows a remanent polarization over 20 µC/cm2, and the e31,f of the samples is -4.7 C/m2.

This paper presents modification in the thickness profile of bimorph cantilever type piezoelectric vibration energy harvester (PVEH) to achieve uniform stress along the beam length. The thickness profile is obtained by varying the thickness of substrate layer and keeping the thickness of piezoelectric layers constant. Analytical expressions for the cantilever beam displacement, stress on the beam and generated voltage are derived and solved for sinusoidal input excitations. The results from the analytical expressions are validated with that of the finite element (FE) analysis of an identical PVEH. The generated power and stress distribution in the proposed PVEH are compared with that of an equivalent conventional PVEH of uniform thickness. Compared to the conventional PVEH, in the proposed PVEH the generated power is 20% higher for an input acceleration of 0.2g, and the stress on the proposed device is found to be uniformly distributed with the peak stress value reduced significantly by 46%.

This paper presents a non-polynomial coupled plate theory for smart composite structures employing inverse hyperbolic displacement and electric potential functions. The theory is utilized towards analysis of composite piezoelectric plates operating in sensor and actuator modes. Particularly, the following three cases are studied: (i) passive laminated composite structure, (ii) composite piezoelectric plate actuator and (iii) unimorph and bimorph piezoelectric plate sensors. Analytical solutions are obtained for simply supported plates under static electrical and mechanical loads. These results are validated with existing 3D elasticity solutions and compared with other plate theory solutions. Furthermore, parametric studies are performed to determine the effect of loading, span-to-thickness ratio and lamination sequence on the response of the piezoelectric plate. Finally, the theory is applied to a transverse shear sensing device which utilizes transverse shear-electric field coupling in piezoelectric materials. This effect is often ignored in literature. It is observed that the maximum percentage error of the present theory, when compared with 3D results, is less than 3%, which is lower than other higher order plate theories.

In this article, proposed is a hysteresis effects model of a bimorph circular flexural-mode piezoelectric actuator for a deformable mirror of adaptive optics system. The analytical solutions are derived from the three-dimensional equations of piezoelectricity, and the dependence of the nonlinear hysteresis performance of the actuator on the physical parameters is evaluated. Numerical results illustrate that the hysteresis loops of the strokes of the actuator are affected by the start values of the electric field and the thickness of the metallic layer. Besides, the results also suggest that an appropriate thickness of metallic layer could compensate some hysteresis effects. Moreover, the results of the analytical method have been demonstrated by those of the finite element method.

A nonlinear micro-piezoelectric–electrostatic energy harvester is designed and studied using mathematical and computational methods. The system consists of a cantilever beam substrate, a bimorph piezoelectric transducer, a pair of tuning parallel-plate capacitors, and a tip–mass. The governing nonlinear mathematical model of the electro-mechanical system including nonlinear material and quadratic air-damping is derived for the series connection of the piezoelectric layers. The static and modal frequency curves are computed to optimize the operating point, and a parametric study is performed using numerical methods. A bias DC voltage is used to adapt the system to resonate with respect to the frequency of external vibration. Furthermore, to improve the bandwidth and performance of the harvester (and achieve a high level of harvested power without sacrificing the bandwidth), a nonlinear feedback loop is integrated into the design.

The challenge of continuously powering the wireless sensor network located at remote areas has been resolved by the emergence of piezoelectric energy harvester. This paper evolved a new idea of using different piezoelectric materials together within segmented doubly clamped bimorph piezoelectric energy harvester (DCBPEH). The finite element modeling of the device has been presented here using COMSOL multiphysics software. This paper starts with concept of strain nodes and further better performance of segmented electrodes-based beam over the continuous electrode-based beam has been achieved. Next, a performance analysis study with continuous electrode-based beam has been carried out for different variants of two piezoelectric materials, namely, PMN-xPT and PZT. From this study, PMN-35%PT and PZT-5H piezoelectric materials are found to be best variants. Finally, the performance of segmented DCBPEH has been observed for different positioning formats of PMN-35%PT (M1) and PZT-5H (M2) piezoelectric materials on different segments of the beam. From this analysis, M1–M1–M2 and M2–M1–M1 are noted to be two favorable positioning formats which provide similar and maximum performance (7.78 mW) as compared to other formats.

Piezoelectric energy conversion has received considerable attention for vibration-to-electric energy conversion over the past decade. A typical piezoelectric energy harvester is a unimorph or a bimorph cantilever located on a vibrating host structure. This paper presents a comparison between unimorph and bimorph cantilever beam having a number of segmented PMN-PT piezo-elements on the input and output power. The numerical simulation was carried out by applying the finite element analysis (FEA) using COMSOL multi-physics software in order to predict output voltage and power over a frequency range of 60–200 Hz for the first resonant frequencies. The simulation results show maximum output voltage and power harvested of 7.38 V and 135.73 μW, respectively, by the unimorph piezoelectric energy harvester at resonant frequency value of 84 Hz with electromechanical coupling factor (ke) of 77.29%. These results highlight that the highest value of the output electrical power can be obtained when the piezoelectric element is attached on the top of a clamped end of a cantilever piezoelectric beam. Moreover, in an unimorph or bimorph cantilever beam system, increasing the number of piezoelectric elements results in a higher resonant frequency shift and significantly decreasing in the harvested power.

In order to investigate the mechanical properties of Ag-IPMC artificial muscles, establishing the mathematical model of Ag-IPMC under non-electrically actuated conditions by superelastic large deformation equation. The mechanical simulation and experimental comparison of Ag-IPMC with different moisture contents were carried out. The piezoelectric coefficient from the bimorph piezoelectric model was equivalently analogized to the calculating of the Ag-IPMC model so that the model was more suitable for the characteristics of nonlinear large deformation of Ag-IPMC. According to the data from the analysis, a conclusion can be drawn: when the moisture content of Ag-IPMC was within a certain range, with the decrease of moisture content of Ag-IPMC, the strain was small under low voltage or low moisture content conditions. Meanwhile, the smaller the strain, the smaller the extrusion of the root where the place was clamped causing by the Ag-IPMC deformation. The mechanical properties of Ag-IPMC were the coupling result of comprehensive factors. Simply improving the performance of any single item would affect the overall mechanical properties.

Piezoelectric bimorphs have a promising application in morphing micro air vehicles; however, increasing the actuation displacement is a difficult point. Axial compression can be used to increase the deformation of the piezoelectric bimorph. Compared with piezoelectric ceramics, macro fiber composites offer higher flexibility. In this article, a large displacement actuator of axial-compressed macro fiber composite bimorph is proposed. A multi-layer parallel scheme of macro fiber composite bimorphs is presented to increase the output torque of piezoelectric bimorph within a limited space. The actuation performance of the axial-compressed macro fiber composite bimorph and its multi-layer parallel scheme are verified through quasi-static experiment and displacement tracking control test. The experimental results show that the end-free rotations of both the axial-compressed macro fiber composite bimorph and its multi-layer scheme achieve ±8.1°, which is 60% higher than that of a piezoelectric ceramics bimorph with the same length. The blocking torque of the single-layer macro fiber composite bimorph is 0.028 Nm. The proposed parallel bimorphs method can magnify output torques. In addition, the axial-compressed macro fiber composite bimorph can accurately track any displacement signals in the range of its actuation. It is a continuous and controllable piezoelectric bimorph with large displacement.

A printed flexible hybrid electronics (FHE) technology platform is described, which combines a thin-film audio speaker, printed interconnects, and printed passive components in a highly flexible system. Bimorph piezoelectric polymer speaker structures were developed and shown to give increased loudness compared with a single layer speaker, with good fidelity and easily recognizable sound. Speakers were fabricated on flexible thin polyimide substrates, which enables integration with printed electronics and other thin-film devices. Two demonstrator circuits were designed to operate the speakers and were fabricated using printed FHE techniques. One circuit was an amplifier for a portable music player, and the second provides a record and playback function using an audio integrated circuit. The fabrication of these devices included ink-jet printed interconnects and ink-jet printed resistors, which showed a good long-term stability and flexibility.

The piezoelectric technique has received extensive attention in an energy harvesting system in the generation of electrical energy through renewable mechanical vibration. In this research paper, a bimorph energy scavenger based on the cantilever beam is designed and optimized to obtain the maximum efficiency. The COMSOL Multiphysics is utilized to design and simulate the proposed model whose output response has been investigated with the variation in the excitation frequency, the thickness of piezoelectric layers and the acceleration. It has been found that the thickness of the piezoelectric layers is the most promising parameter to acquire the maximum harvested energy. Moreover, several trials are also introduced in the simulation based on the resistance values of 20, 40, and 60 Ω. The results show that the output voltage has a positive linear relationship with the resistance and it is maximum at the frequency of 50 Hz, known as the resonant frequency. Many studies have shown quite significant relationships between mechanical vibration and harvested energy. So, the current research has presented a novice approach to optimize the results of an energy harvester. This approach is accomplished by a statistical analysis based on the Taguchi and ANOVA design of experiments. Keywords: Energy harvesting, Piezoelectric materials, Micro-Electro-Mechanical Systems (MEMS), COMSOL Multiphysics, Design of experiments (DOE)

This paper presents the investigation of a crack repair in a composite plate using piezoelectric smart material, which is also called as active repair. Composite plate with crack is modeled by a finite element method. An 8-node structural shell element is used to discretize composite material, and the 8-node coupled-field element is used for the modeling of the piezoelectric patch. The repair in the cracked composite plate is modeled and analyzed under both static and dynamic loading conditions. The unimorph and bimorph patching are used for active repair. Effectiveness of the patch repair is measured in terms of stress field near the crack tip. The usefulness of unimorph and bimorph patching is compared in three different cases, namely (i) passive, (ii) active and (iii) without patching. A significant reduction in the equivalent stress at the crack tip of the composite plate is observed because of repair by unimorph and bimorph active patching. Bimorph patching presents a greater reduction in the stress level near to discontinuity

To meet the dual requirement of high flow rate and high output pressure in water-cooling system of electronic chip, a quintuple-bimorph tenfold-chamber piezoelectric pump (QTPP) is presented, which owns the comprehensive advantages of parallel and serial connection. QTPP is composed of two groups of five-chamber-in-series, and the two groups of five-chamber-in-series can be in parallel or serial. QTPP is designed and fabricated, the output performance of which is invested by experiments. The experimental results show that QTPP can obtain high flow rate and high output pressure under low driving voltage. When driven by quintuple piezoelectric vibrators under 60Vpp, QTPP in parallel can obtain the maximum flow rate of 251.1ml/min and the maximum output pressure of 60.2kPa. While in serial, QTPP can obtain 186.2ml/min and 109.9kPa respectively. The water-cooling system with QTPP is established and experimented. The experimental results indicate that the water-cooling system with QTPP can achieve a good cooling performance under low driving voltage. Under the driving voltage of 60Vpp, QTPP can reduce the temperature of stimulate chip from 107.8°C to 51°C.

In this investigation the modeling and analysis of dynamic structured Macro-Fiber Composite (MFC) for ambient power has been composed to unimorph and bimorph cantilever beam. The dimensions of the beam and its properties were investigated in order to tip displacement across its length with active and inactive piezoelectric layers of MFC. To optimize structure of a cantilever beam with respect to natural frequency, more effective vibration control that can be achieved with minimum control input. The results show that the dynamic model of the cantilever beam is validated with comparisons of experimental, theoretical data and analytical investigation by using ANSYS Simulation.

We present an analytical modeling framework and its analysis for thin piezoelectric metamaterial plates to enable and predict low-frequency bandgap formation in finite structural configurations with specified boundary conditions. Using Hamilton’s extended principle and the assumptions of classical (Kirchhoff) plate theory, the governing equations and boundary conditions for the fully coupled two-dimensional electromechanical system are obtained. The two surfaces of the piezoelectric bimorph are segmented into non-overlapping opposing pairs of electrodes of arbitrary shape, and each pair of electrodes is shunted to an external circuit. This formulation can be used to study the effect of electrode shape on plate response for topology optimization and other vibration control applications. Using modal analysis, we show that for a sufficient number of electrodes distributed across the surface of the plate, the effective dynamic stiffness of the plate is determined by the shunt circuit admittance applied to each pair of electrodes and the system-level electromechanical coupling. This enables the creation of locally resonant bandgaps and broadband attenuation, among other effects, in analogy with our previous work for one-dimensional piezoelectric structures with synthetic impedance shunt circuits. It is also demonstrated that piezoelectric bimorph plates display significantly improved performance (i.e. electromechanical coupling) over bimorph beams, but require additional electrode segmentation to achieve metamaterial-type performance. The governing equations are also used for dispersion analysis using the plane wave expansion method, enabling the analytical dispersion analysis of unit cells with arbitrary electrode shapes. The modeling framework and approximate closed-form bandgap expressions are numerically validated using finite element analysis.

Autonomous sensors that receive their energy from an energy harvester or directly from the environment have the potential to save energy for applications in numerous sectors. For humidity sensing, the swelling behaviour of a water vapour-sensitive hydrogel is used. To trigger an electrical contact the mechanical energy is taken from the hydrogel swelling by the bimorph effect. As long as a defined threshold is not reached, the electrical microcontact remains open. By passing the threshold value, a switching will be triggered causing the closure of the contact. This sensor principle does not need any electrical power supply because the switching power is provided directly by the surrounding humidity as quantity to be measured. For the description of the deflection versus the hydrogel pattern of such a sensor, a model was developed by means of the beam theory. Goal of the model was to derive design guidelines for the dimensioning of the sensors bending plate and the patterned hydrogel layer. Experiments then should show the applicability of the model approaches. The deflection of the bending plate depends on the ratio between the lengths of the uncoated and the coated part of the bending plate where the maximum occurs at a ratio of ca. 0.5. The swelling behaviour of the hydrogel shows a high sensitivity with regard to slight changes in relative humidity. This can be used for humidity threshold sensors that open and close microcontacts with respect to very small changes in relative humidity. To avoid voltage peaks and arcs during the switching process that could arise and destroy the microcontact, a bistable characteristic with hysteresis is needed. Experiments demonstrate the feasibility of this concept and are in good agreement with the modelling results.

The problem of constructing a thermal sensor based on the technology of microelectromechanical systems is solved by structural and circuit integration of capacitance-dependent and thermomechanical parts. For this, the use of a MOS transistor (capacitance-dependent part) with a gate in the form of a bimorph membrane (thermomechanical part), which performs cyclic oscillations under the influence of heating from a sensitive element and subsequent cooling, is proposed. The novelty of the proposed sensor is the provision of a frequency-dependent output signal without the use of additional generator circuits. This makes it easier to combine the sensor with digital signal processing systems and reduce the influence of transmission lines on measurement accuracy. Also, the advantages of the sensor include reduced overall dimensions, which is achieved due tothevertical integration of its elements. Model studies of the sensor are carried out and on their basis circuit and software-hardware solutions for determining the temperature of the sensitive element are proposed. It is shown that the use of logarithmic dependence to approximate the influence of the temperature of the sensitive element on the output pulse frequency of the sensor minimizes the measurement error to 3.08%. The composition of the information and measurement system, which contains a thermal sensor, a sensor signal pre-processing circuit and measurement processing unit using the Atmega328 microcontroller on the platform of the unified ArduinoUno module, is determined. It is shown that the total error of temperature determination in the developed system does not exceed 4.18% in the temperature range of the sensor element from 20 °C to 47 °C. The program code for the microcontroller part of the information and measurement system is developed, which occupies 12% of the program memory and 4.9% of the dynamic memory of the unified module. The proposed thermal microelectromechanical sensor can be used for contact measurement ofthetemperature of gaseous and liquid media, recording of optical radiation and microwave signals

As the need for smaller, lighter, and longer lasting energy storage increases, silicon (Si) rises as a promising anode material of lithium (Li) ion batteries due to large specific capacity. However, the Si undergoes severe volume expansion causing mechanical fracture and electrochemical degradation. The use of nanostructured Si prevents mechanical fracture, but its large surface area enables irreversible side reaction. Therefore, understanding the mechanical behavior of lithiated Si (LixSi) is essential for designing robust Si structures with less surface area. Here, we estimate the stress in LixSi on crystalline-Si (c-Si) and copper bimorph plate and study its fracture resistance. When LixSi and c-Si coexisted, LixSi exhibits ~ 50 % of the full lithiation and compression of ~ 0.55 GPa, which is smaller than its yield strength. After c-Si is removed, it is predicted that plastic deformation of LixSi would occur on the open surface of the plate, but most of the structure would remain in the elastic behavior regime. The low stress in the LixSi plate allows it to bear fractures up to much larger size (~ 2 μm) than that of Si nanoparticles and nanopillars. It suggests using the robust micron-scale silicon structure for highly reversible and cost effective anode of Li-ion batteries. Agency for Science, Technology and Research (A*STAR) Accepted version This work was supported by Science and Engineering Research Council Singapore-Korea Joint Research Programme from A*STAR, Singapore [162-82-00009]; International Cooperation in S&T Program [NRF-2016K2A9A1A06934767]; and Basic Research Lab Program [NRF-2017R1A4A1015533] through the National Research Foundation of Korea funded by the Ministry of Science and ICT.

This paper deals with analytical modelling of piezoelectric energy harvesting systems for generating useful electricity from ambient vibrations and comparing the usefulness of materials commonly used in designing such harvesters for energy harvesting applications. The kinetic energy harvesters have the potential to be used as an autonomous source of energy for wireless applications. Here in this paper, the considered energy harvesting device is designed as a piezoelectric cantilever beam with different piezoelectric materials in both bimorph and unimorph configurations. For both these configurations a single degree-of-freedom model of a kinematically excited cantilever with a full and partial electrode length respecting the dimensions of added tip mass is derived. The analytical model is based on Euler-Bernoulli beam theory and its output is successfully verified with available experimental results of piezoelectric energy harvesters in three different configurations. The electrical output of the derived model for the three different materials (PZT-5A, PZZN-PLZT and PVDF) and design configurations is in accordance with lab measurements which are presented in the paper. Therefore, this model can be used for predicting the amount of harvested power in a particular vibratory environment. Finally, the derived analytical model was used to compare the energy harvesting effectiveness of the three considered materials for both simple harmonic excitation and random vibrations of the corresponding harvesters. The comparison revealed that both PZT-5A and PZZN-PLZT are an excellent choice for energy harvesting purposes thanks to high electrical power output, whereas PVDF should be used only for sensing applications due to low harvested electrical power output.

The development of wearable devices and remote sensor networks progressively relies on their increased power autonomy, which can be further expanded by replacing conventional power sources, characterized by limited lifetimes, with energy harvesting systems. Due to its pervasiveness, kinetic energy is considered as one of the most promising energy forms, especially when combined with the simple and scalable piezoelectric approach. The integration of piezoelectric energy harvesters, generally in the form of bimorph cantilevers, with wearable and remote sensors, highlighted a drawback of such a configuration, i.e., their narrow operating bandwidth. In order to overcome this disadvantage while maximizing power outputs, optimized cantilever geometries, developed using the design of experiments approach, are analysed and combined in this work with frequency up-conversion excitation that allows converting random kinetic ambient motion into a periodical excitation of the harvester. The developed optimised designs, all with the same harvesters’ footprint area of 23 × 15 mm, are thoroughly analysed via coupled harmonic and transient numerical analyses, along with the mostly neglected strength analyses. The models are validated experimentally via innovative experimental setups. The thus-proposed ϕ = 50 mm watch-like prototype allows, by using a rotating flywheel, the collection of low-frequency (ca. 1 to 3 Hz) human kinetic energy, and the periodic excitation of the optimized harvesters that, oscillating at their eigenfrequencies (~325 to ~930 Hz), display specific power outputs improved by up to 5.5 times, when compared to a conventional rectangular form, with maximal power outputs of up to &gt, 130 mW and average power outputs of up to &gt, 3 mW. These power levels should amply satisfy the requirements of factual wearable medical systems, while providing also an adaptability to accommodate several diverse sensors. All of this creates the preconditions for the development of novel autonomous wearable devices aimed not only at sensor networks for remote patient monitoring and telemedicine, but, potentially, also for IoT and structural health monitoring.

Photothermal bimorph actuators have attracted considerable attention in intelligent devices because of their cordless control and lightweight and easy preparation. However, current photothermal bimorph actuators are mostly based on films or papers driven by near-infrared sources, which are deficient in flexibility and adaptability, restricting their potential in wearable applications. Herein, a bimorph textile actuator that can be scalably fabricated with a traditional textile route and autonomously triggered by sunlight is reported. The active layer and passive layer of the bimorph are constructed by polypropylene tape and a MXene-modified polyamide filament. Because of the opposite thermal expansion and MXene-enhanced photothermal efficiency (>260%) of the bimorph, the textile actuator presents effective deformation (1.38 cm–1) under low sunlight power (100 mW/cm2). This work provides a new pathway for wearable sunlight-triggered actuators and finds attractive applications for smart textiles.

In this work, the optimal design of an unmanned aerial vehicle (UAV) wing spar by multi-objective optimization genetic algorithms is studied. An electromechanical finite element model (FEM) for piezolaminated bimorph cantilever structure with embedded piezoceramics is used combined with multiobjective genetic algorithms. The FEM formulation is based on laminated plate theory combined with the first-order shear deformation theory (FSDT) for which each piezoelectric layer has one additional electrical degree of freedom. Non-dominated Sorting Genetic Algorithm II (NSGA-II), Non-dominated Sorting Genetic Algorithm III (NSGA-III) and Generalized Differential Evolution 3 (GDE3) algorithm have been used to optimize the geometric and electric circuit parameters of a UAV generator for maximum power output and minimum mass added by the embedded piezoceramics. It is shown that the proposed algorithms are effective in developing optimal Pareto front curves for maximum electrical power output of the generator spar and minimum mass add by the embedded piezoceramics. Comparison of the generated solutions on the Pareto Front for UAV wing spar design shows that all three algorithms achieve solutions that closely resemble a constructed reference Pareto optimal front.

Silicon is regarded as one of the most promising anode materials for lithium-ion batteries. Its high theoretical capacity (4000 mAh/g) has the potential to meet the demands of high-energy density applications, such as electric air and ground vehicles. The volume expansion of Si during lithiation is over 300%, indicating its promise as a large strain electrochemical actuator. A Si-anode battery is multifunctional, storing electrical energy and actuating through volume change by lithium-ion insertion. To utilize the property of large volume expansion, we design, fabricate, and test two types of Si anode cantilevers with bi-directional actuation: (a) bimorph actuator and (b) insulated double unimorph actuator. A transparent battery chamber is fabricated, provided with NCM cathodes, and filled with electrolyte. The relationship between state of charge and electrode deformation is measured using current integration and high-resolution photogrammetry, respectively. The electrochemical performance, including voltage versus capacity and Coulombic efficiency versus cycle number, is measured for several charge/discharge cycles. Both configurations exhibit deflections in two directions and can store energy. In case (a), the largest deflection is roughly 35% of the cantilever length. Twisting and unexpected bending deflections are observed in this case, possibly due to back-side lithiation, non-uniform coating thickness, and uneven lithium distribution. In case (b), the single silicon active coating layer can deflect 12 passive layers.

In this paper, an acoustic resonator with frequency > 5 GHz is designed, implemented, and measured with electromechanical coupling exceeding 15% and low temperature dependence compared to conventional Lamb-wave resonators. The acoustic resonator is optimized for the S4 mode Lamb waves in a bi-morph composed of Lithium Niobate and Silicon Dioxide. The resonator optimization is based on adjusting the thickness of different materials in the bimorph to maximize the coupling and minimize temperature dependence simultaneously. The achieved specifications are adequate for 5G sub-6 GHz frequency band n46 in addition to Wi-Fi new bands between 5 and 6 GHz.

This paper present a simulation of lead-free piezoelectric materials which are Zinc Oxide (ZnO), Barium Sodium Niobate (BNN), and Barium Titanate (BaTiO 3 ) using COMSOL Multiphysics 5.2 software. The simulation aims to investigate the power generated by these lead-free materials. There were two parts of the simulation setup, firstly, 3D block cantilever for simulating frequency response and total displacement. As result, BaTiO 3 generates the highest frequency response, which was 58.566 kHz with 303μm of the total displacement. This part also simulates various cantilever beam thickness range around 1-4μm and BaTiO 3 gave the highest value for resonant frequency than the ZnO and BNN. The second part was a 2D block bimorph to simulate the generated power. For this modeling, there is four rectangles parameter of cantilever block dimension is simulates by varying frequency response. The frequency response has been set at 60 - 200 Hz. According to this, at 100 Hz frequency response give the best performance. For generated power, BaTiO 3 offer the best performance in term of mechanical stress with generated electric potential was 12.2V, and 1.86mW of power dissipation and 6.09 N/m2 at 140Hz. At the end of this project, BaTiO 3 give the best performance in terms of frequency response and power generated 91.72-99% better compared to ZnO and BNN.

This paper presents a new way to design a broadband harvester for harvesting high energy over a low-frequency range of 10–15 Hz. The design comprises a cantilever beam with two parallel grooves to form three dissimilar length parallel branches, each with an unequal concentrated tip mass. The piezoelectric material covers the whole length on both sides of the beam to form a bimorph. Appropriate geometry and mass magnitudes are obtained by a parametric study using the Finite Element Method. The design was simulated in COMSOL Multiphysics to study its response. The first three bending modes were utilized in energy harvesting, resulting in three power peaks at their respective fundamental frequencies. The adequate load resistance determined was 5.62 kΩ, at which maximum power can be harvested. The proposed harvester was compared to two other harvesters presented in the literature for validation: First, an optimized conventional harvester while the proposed harvester is operating at adequate load resistance. Second, a multimodal harvester, while the proposed harvester is operating at a 10 kΩ load. The suggested harvester proved to be more efficient by harvesting sufficiently higher broadband energy and is applicable in a wide range of vibration environments because of its adaptability in design.

Bimorph deformable mirrors can be successively used to improve focusing of a laser beam passed through a moderately scattering medium with optical density in the range of 1 ... 10. In this paper we investigate the efficiency of the stacked actuator deformable mirror with 61 piezo stacks and clear aperture of 60 mm. We demonstrate that such kind of mirrors also can be used to optimize the focal spot in the far-field. Shack-Hartmann sensor was used to measure the averaged wavefront distortions and CCD camera was used to estimate the intensity distribution of the focal spot in the far-field.

PZT (lead zirconate titanate)-glued bimorph deformable mirrors are widely used in hard x-ray regimes[1], however, they have not yet been used in soft X-ray regimes because they are less compatible for usage under high vacuum. Therefore, we have developed a glue-free bimorph deformable mirror, in which silver nanoparticles were employed to bond PZT actuators to mirror substrates[2]. In this study, we achieved a 2 nm figure error on an elliptical shape of a glue-free deformable mirror. We evaluated the figure change characteristics due to humidity and temperature increasing at the ultrafine figure error condition.

This paper presents a study on the design and multiobjective optimization of a bimorph-segmented linearly tapered piezoelectric harvester for low-frequency and multimode vibration energy harvesting. The procedure starts with a significant number of FEM simulations of the structure with different geometric dimensions—length, width, and tapering ratio. The datasets train the artificial neural network (ANN) that provides the fitting function to be modified and used in algorithms for optimization, aiming to achieve minimal resonant frequency and maximal generated power. Levenberg–Marquardt (LM) and scaled conjugate gradient (SCG) methods were used to train the ANN, then the goal attainment method (GAM) and genetic algorithm (GA) were used for optimization. The dominant solution resulted from optimization by the genetic algorithm integrated with the ANN fitting function obtained by the SCG training method. The optimal piezoelectric harvester is 121.3 mm long and 71.56 mm wide and has a taper ratio of 0.7682. It ensures over five times greater output power at frequencies below 200 Hz, which benefits the low frequency of the vibration spectrum. The optimized design can harness the power of higher-resonance modes for multimode applications.