Showing papers on "Bimorph published in 2019"

Review of Electrothermal Actuators and Applications

Abstract: This paper presents a review of electrothermal micro-actuators and applications. Electrothermal micro-actuators have been a significant research interest over the last two decades, and many different designs and applications have been investigated. The electrothermal actuation method offers several advantages when compared with the other types of actuation approaches based on electrostatic and piezoelectric principles. The electrothermal method offers flexibility in the choice of materials, low-cost fabrication, and large displacement capabilities. The three main configurations of electrothermal actuators are discussed: hot-and-cold-arm, chevron, and bimorph types as well as a few other unconventional actuation approaches. Within each type, trends are outlined from the basic concept and design modifications to applications which have been investigated in order to enhance the performance or to overcome the limitations of the previous designs. It provides a grasp of the actuation methodology, design, and fabrication, and the related performance and applications in cell manipulation, micro assembly, and mechanical testing of nanomaterials, Radio Frequency (RF) switches, and optical Micro-Electro-Mechanical Systems (MEMS).

A novel method for autonomous remote condition monitoring of rotating machines using piezoelectric energy harvesting approach

Abstract: This paper presents a novel autonomous method for condition monitoring of rotating machines during operation based on radio frequency (RF) pulse transmission using energy harvesting from operational vibration. An energy harvesting unit is designed to generate and rectify the energy harvested from the machine vibration using Voltage Multiplier (VM) circuit and to store the energy into a capacitor. Then, this energy harvesting unit runs a smart system consisting of a microcontroller and the RF transmitter designed to send a pulse at specific capacitor voltage. A pulse-based condition monitoring approach is introduced which monitors the state of the machine during the operation. In order to estimate power output of the piezoelectric harvester for a realistic vibration signal, the Fourier Transform concept for signal decomposition is incorporated into the well-known electromechanical distributed parameter model. Using experimental data, performance of this autonomous condition monitoring system is tested for a water pump at different conditions. To do so, acceleration data from a centrifugal water pump are acquired with an accelerometer, which then decomposed into a series of harmonics using Fast Fourier Transform. Then using analytical distribute model, a bimorph energy harvester with two Piezoceramic layers is optimized to generate maximum power from the water pump vibration. Consequently, the condition monitoring of the water pump is performed using the presented pulse-based approach. Results of this study show that, the fault diagnosis can be performed autonomously by applying the pulse-based method presented in this work, and by using the piezoelectric harvesting device as an energy source.

Photo-activated bimorph composites of Kapton and liquid-crystalline polymer towards biomimetic circadian rhythms of Albizia julibrissin leaves

Abstract: Circadian rhythm is a built-in bioclock widely existing in living organisms, not only in animals but also in plants. Particularly, circadian rhythm is of great importance for the growth of plants. To mimic the circadian rhythm behavior of Albizia julibrissin leaves, we designed photo-activated bimorph composites with several kinds of photoresponsive liquid-crystalline polymers and commercially-available polyimide (Kapton). Compared with conventional photo-actuators, the fabricated bimorph composite possesses good mechanical properties, a large displacement angle and a fast photoresponsive rate at room temperature. Upon irradiation with actinic light, unique photomechanical behaviors were observed, in which the bimorph composites always bent towards the Kapton layer side independent of the incident direction of UV light, as a result of the photoinduced volume expansion of the liquid-crystalline polymer layer. To further explore the photomechanical properties, the F (photoinduced driving force)–I (light intensity) and θ (displacement angle)–I (light intensity) relationships of the photo-activated bimorph composites were theoretically proposed based on a classical double beam model. Taking advantage of their sensitivity to light intensities, artificial Albizia julibrissin leaves exhibiting circadian rhythms upon UV irradiation with time varying light intensities (simulating the sunlight change from sunrise to sunset) were successfully fabricated, which may extend the versatility of biomimetic research studies.

A Low-Frequency Structure-Control-Type Inertial Actuator Using Miniaturized Bimorph Piezoelectric Vibrators

Abstract: A low-frequency structure-control-type inertial actuator using miniaturized bimorph piezoelectric vibrators is proposed in this paper to achieve high resolution and high stability with a large linear stroke. These vibrators are fabricated by bonding, thinning, and patterning fabrication processes, which are beneficial to realize miniaturization and increase output performance for the system. A theoretical model based on work-energy analysis is established to predict the output displacement characteristics. An experimental system is built to evaluate the performance of the proposed actuator. Experimental results indicate that the stable minimum step displacement is 0.03 μm under a square wave signal of 5 V, 50 Hz, and a clamping difference of 3.5 mm. Under the condition of 7 V and 50 Hz, the sample standard deviation is 0.0337 μm in repeatability test. The proposed actuator achieves a stable and accurate linear bidirectional motion with high resolution, high stability, low power consumption, and a large working stroke.

Rapid and low power laser actuation of sputter-deposited NiTi shape memory alloy (SMA) MEMS thermal bimorph actuators

Abstract: NiTi SMA thermal bimorph actuators have potential as high-force, high-displacement MEMS actuators. Historically, even microscale SMA actuation response has been limited to a maximum of ˜100 Hz. As NiTi film and device dimensions are scaled down into the micro and nano scales, heat transfer, and thus device cycling speeds can be significantly improved upon. We have used an in-situ annealed nickel-titanium (NiTi) shape memory alloy (SMA) sputter deposition process to sputter equiatomic NiTi films at 600 °C. We characterized our thin film (270 nm NiTi – 1.6 μm NiTi) material and verified its reversible shape memory effects (SME) using differential scanning calorimetry (DSC), X-ray diffraction (XRD), and wafer bow versus temperature measurements. Upon release, the NiTi material exhibited a reversible phase change around 60 °C with a hysteresis of ˜3 °C. For the substrate confined case (i.e. NiTi on Si or Pt), hysteresis was much larger (i.e. ˜40 °C) with the phase change completed at ˜80 °C. In addition to SMA material characterization, we fabricated NiTi/Pt bimorph actuators at several (100 nm to 1.2 μm) NiTi and Pt thicknesses. Free-standing bimorph actuators were produced via a dry etch release, and temperature dependent curvature of these cantilevers was investigated. To address the low power, and high response time aspects, we performed a dynamic characterization using a 440 mW, 532 nm “green” laser to irradiate devices from 2 to 24 W/cm2 while measuring actuation response times that varied from 3 ms at the highest irradiation fluxes to 240 ms at the lowest. Our results showed decreased actuation powers and faster heating or actuation times compared to past works with NiTi microactuators. The NiTi films with 600 nm thickness on top of 20 nm Pt films exhibited the greatest change in curvature from 200 μm to flat states, and actuated in under 3 ms due to the very small volume of SMA requiring to be heated. These results suggest that NiTi/Pt bimorphs have potential applications as lower-power, faster-response, laser-activated micro shutters or thermal switches without needing a traditional wired power source.

Bimorph deformable mirror with a high density of electrodes to correct for atmospheric distortions.

Abstract: This paper presents a new development of small-diameter, high-spatial-resolution, semipassive bimorph deformable mirrors to be used in different imaging systems. To manufacture the small control elements, laser engraving technology is used. An ultrasonic welding technique to connect the wires to the electrodes (actuators) is applied for this kind of mirror. The initial flatness of the mirror surface equals 0.33 μm (P-V) due to the use of substrate polishing technology after gluing the glass substrate to a piezo disk. We present the main parameters of these wavefront correctors, such as the response functions of different electrodes, temporal behavior, and the ability to compensate for high-order aberrations.

A complementary strategy for producing moisture and alkane dual-responsive actuators based on graphene oxide and PDMS bimorph

Abstract: Smart actuators that enable deforming in a predictable manner under external stimuli have revealed great potential for both traditional and emerging industries. Generally, an asymmetric bilayer structure with one layer active and the other inert to a certain stimulus is essential to realize bending behavior. However, towards the development of dual- or multi-responsive actuators, it still lacks universal and effective strategies for rational design and fabrication of such devices through the simplest way. In this paper, we report a complementary strategy to produce dual-responsive bilayer actuators by combining the moisture-active/alkane-inert graphene oxide (GO) layer with the alkane-active/moisture-inert polydimethylsiloxane (PDMS) layer. The GO@PDMS bimorph actuator can switch its active and inert layers in response to moisture and alkane, respectively, realizing dual-responsive deformation under different actuations. Typical dual-responsive actuators, including a selective air valve and a grip and hook smart claw, are successfully fabricated, demonstrating the capability of effective gases and objects transmission. The complementary bimorph actuator may hold great promise for developing intelligent devices and portable delivery systems.

Nonlinear dynamics of parametrically excited piezoelectric energy harvester with 1:3 internal resonance

Abstract: In this work, the nonlinear dynamic analysis of a parametrically base excited cantilever beam based piezoelectric energy harvester is carried. The system consists of a cantilever beam with piezoelectric patches in bimorph configuration and attached mass at an arbitrary position. The attached mass is placed in such a way that the system exhibits 3:1 internal resonance. The governing spatio-temporal equation of motion is discretized to its temporal form by using generalized Galerkin’s method. To obtain the steady state voltage response and stability of the system, Method of multiple scales is used to reduce the resulting equation of motion into a set of first-order differential equations. The response and stability of the system under principal parametric resonance conditions has been studied. The parametric instability regions are shown for variation in different system parameters such as excitation amplitude and frequency, damping and load resistance. Bifurcations such as turning point, pitch-fork and Hopf are observed in the multi-branched non-trivial response. By tuning the attached mass an attempt has been made to harvest the electrical energy for a wider range of frequency. Such kind of smart self-sufficient systems may find application in powering low power wireless sensor nodes or micro electromechanical systems.

High accuracy comsol simulation method of bimorph cantilever for piezoelectric vibration energy harvesting

Abstract: Piezoelectric bimorph cantilever is a typical structure for vibration energy harvesting. This paper studies the method to improve the accuracy of FEA (finite element analysis) simulation for piezoelectric bimorph cantilever. The COSMOL simulation methods based on 1 D (dimension) model of Euler Bernoulli beam, as well as 2 D and 3 D models of solid mechanics are proposed respectively. Compared with the theory and experiment results given by Erturk A, the influences of 1 D and 3 D piezoelectric material parameters on simulation accuracy in FEA modeling is discussed. The simulation error can be reduced to less than 1.2% by using 1D piezoelectric material parameters in COMSOL simulation, while the maximum simulation error can be up to 28% by using 3D piezoelectric material parameters. Comparing serial and parallel configurations of piezoelectric bimorph cantilever, the output electrical powers, varying with the excitation frequency and load resistance, are also discussed in COMSOL simulation. Performance comparation of three kinds of piezoelectric bimorph cantilevers with tip mass shows that the modelling and simulation in finite element methods by COMSOL are simple and convenient, and are suitable for the electromechanical coupling analysis and optimization of complex topological structures.

Investigation of Deformation in Bimorph Piezoelectric Actuator: Analytical, Numerical and Experimental Approach

Abstract: Piezoelectric actuators are widely used in many fields such as medical instruments, optics, and aerospace due to their small size and high reliability. Piezoelectric cantilever actuators ar...

Modeling and power performance improvement of a piezoelectric energy harvester for low-frequency vibration environments

Abstract: A novel oscillator structure consisting of a bimorph piezoelectric cantilever beam with two steps of different thicknesses is proposed to improve the energy harvesting performance of a vibration energy harvester (VEH) for use in low-frequency vibration environments. Firstly, the piezoelectric cantilever is segmented to obtain the energy functions based on the Euler–Bernoulli beam assumptions, then the Galerkin approach is utilized to discretize the energy functions. Applying boundary conditions and continuity conditions enforced at separation locations, the coupled electromechanical equations governing the piezoelectric energy harvester are introduced by means of the Lagrange equations. Furthermore, expressions for the steady-state response are obtained for harmonic base excitations at arbitrary frequencies. Numerical results are computed, and the effects of the ratio of lengths, ratio of thicknesses, end thickness, and load resistance on the output voltage, harvested power, and power density are discussed. Moreover, to verify the analytical results, finite element method simulations are also conducted to analyze the performance of the proposed VEH, showing good agreement. All the results show that the present oscillator structure is more efficient than the conventional, uniform beam structure, specifically for vibration energy harvesting in low-frequency environments.

A Packaged Piezoelectric Vibration Energy Harvester with High Power and Broadband Characteristics

Abstract: This paper presents the new design and fabricating process of a packaged micro piezoelectric vibration energy harvester (PVEH). Structures are designed and parameters are optimized through finite element modelling and analysis. The double L-shaped tungsten proof mass block and thick copper-based PZT bimorph are proposed to ensure the harvester with high electrical power. Polymethyl methacrylate (PMMA) packaging and epoxy resin bonding supply the flexible clamping of piezoelectric cantilever, which decreases the resonant frequency, increase average PZT stress, reduces the maximum PZT stress and broadens the effective frequency range. Bulk PZT bonding is used in PVEH prototype fabrication. Experimental results show that the packaged PVEH resonates under the excitation of 1 g (9.8 m s−2) at 160 Hz. It has an optimum resistance load of 47 kΩ. More importantly, its maximum output power is 2.49 mW in experiments, and the half-power bandwidth is 22 Hz. After package, it has a high volume power density of 0.64 mW/cm3 g2 with the volume of 3.9 cm3 (2 cm × 1.5 cm × 1.3 cm). Connected with energy harvesting circuit, PVEH can light up a light emitting diode (LED) under broadband vibration frequency. The proposed PVEH with broadband output power in mW level is promised to power up some microelectronic devices for application.

Dual-Structured Flexible Piezoelectric Film Energy Harvesters for Effectively Integrated Performance.

Abstract: Improvement of energy harvesting performance from flexible thin film-based energy harvesters is essential to accomplish future self-powered electronics and sensor systems. In particular, the integration of harvesting signals should be established as a single device configuration without complicated device connections or expensive methodologies. In this research, we study the dual-film structures of the flexible PZT film energy harvester experimentally and theoretically to propose an effective principle for integrating energy harvesting signals. Laser lift-off (LLO) processes are used for fabrication because this is known as the most efficient technology for flexible high-performance energy harvesters. We develop two different device structures using the multistep LLO: a stacked structure and a double-faced (bimorph) structure. Although both structures are well demonstrated without serious material degradation, the stacked structure is not efficient for energy harvesting due to the ineffectively applied strain to the piezoelectric film in bending. This phenomenon stems from differences in position of mechanical neutral planes, which is investigated by finite element analysis and calculation. Finally, effectively integrated performance is achieved by a bimorph dual-film-structured flexible energy harvester. Our study will foster the development of various structures in flexible energy harvesters towards self-powered sensor applications with high efficiency.

Gradient Assembly of Polymer Nanospheres and Graphene Oxide Sheets for Dual-Responsive Soft Actuators.

Abstract: Bimorph actuators hold great promise for developing soft robots. However, poor interlayer adhesion between different materials always threatens their stability for long-term usage. In this paper, i...

Deflection of coupled elasticity–electrostatic bimorph PVDF material: theoretical, FEM and experimental verification

Abstract: Piezoelectric materials have wide applications in the field of mechanical, aerospace and civil engineering because of its voltage dependent actuation. Piezoelectric material goes through voltage generation whenever deflection is induced in it and vice versa. Piezoelectric bimorph beam has been widely used for sensing and actuating. In the actuation mode, an electric field is applied across the beam thickness, one layer contracts while the other expands. This results in the bending of the entire structure and tip deflection. In the sensing mode, the bimorph is used to measure an external load by monitoring the piezoelectric induced electrode voltages. In this research work, a 2D bimorph piezoelectric actuator model having two layers made of polyvinylidene fluoride (PVDF) material was developed to examine the inverse piezoelectric effect. Finite element analysis (FEA) was carried out on specially designed actuator model by using MATLAB Partial Differential Equation (PDE) Toolbox™. Theoretical analysis has been carried out to measure the tip deflection under applied electric field. The laboratory test was performed to investigate the deformation behavior of piezoelectric actuator. It is observed that, more the electric field applied, more the material would be deformed in a particular direction. The experimental results are in good agreement with numerical results.

A high-performance soft actuator based on a poly(vinylidene fluoride) piezoelectric bimorph

Abstract: Compared with a single piezoelectric poly(vinylidene fluoride) (PVDF) sheet, a bimorph can enhance driving performance. The main aim of this work is to study a soft piezoelectric bimorph as an actuator used in a soft sail. PVDF samples were prepared using a high-temperature solvent evaporation method and were then drawn and poled. The crystalline phase, mechanical properties, piezoelectric property and energy-harvesting performance were analyzed. A PVDF piezoelectric bimorph was designed. The capacity of deformation of the parallel bimorph with a pulsed electric field was studied. The deformation of the sample increased almost linearly, and the deformation performance was obvious with the increase in voltage. To evaluate its driving performance in the engineering model, a sail made of Kapton was produced, and the PVDF bimorph was used as an actuator to drive the sail. The deformation was observed by a Video-Simultaneous Triangulation and Resection System. Furthermore, the finite element method was used to further understand the actuation effect of the Kapton sail matrix and PVDF bimorph actuator according to three different laying methods.

Performance analysis of parametrically and directly excited nonlinear piezoelectric energy harvester

Abstract: The performance of bimorph cantilever energy harvester subjected to horizontal and vertical excitations is investigated. The energy harvester is simulated as an inextensible piezoelectric beam with the Euler–Bernoulli assumptions. A horizontal base excitation along the axis of the beam is converted into the parametric excitation. The governing equations include geometric, inertia and electromechanical coupling nonlinearities. Using the Galerkin method, the electromechanical coupling Mathieu–Duffing equation is developed. Analytical solutions of the frequency response curves are presented by using the method of multiple scales. Some analytical results are obtained, which reveal the influence of different parameters such as the damping, load resistance and excitation amplitude on the output power of the energy harvester. In the case of parametric excitation, the effect of mechanical damping and load resistance on the initiation excitation threshold is studied. In the case of combination of parametric and direct excitations, the dynamic characteristics and performance of the nonlinear piezoelectric energy harvesters are studied. Our studies revealed that the bending deformation generated by direct excitation pushes the system out of axial deformation and overcomes the limitation of initial threshold of parametric excitation system. The combination of parametric and direct excitations, which compensates and complements each other, can be served as a better solution which enhances performance of energy harvesters.

An Electrothermal Cu/W Bimorph Tip-Tilt-Piston MEMS Mirror with High Reliability

Abstract: This paper presents the design, fabrication, and characterization of an electrothermal MEMS mirror with large tip, tilt and piston scan. This MEMS mirror is based on electrothermal bimorph actuation with Cu and W thin-film layers forming the bimorphs. The MEMS mirror is fabricated via a combination of surface and bulk micromachining. The piston displacement and tip-tilt optical angle of the mirror plate of the fabricated MEMS mirror are around 114 μm and ±8°, respectively at only 2.35 V. The measured response time is 7.3 ms. The piston and tip-tilt resonant frequencies are measured to be 1.5 kHz and 2.7 kHz, respectively. The MEMS mirror survived 220 billion scanning cycles with little change of its scanning characteristics, indicating that the MEMS mirror is stable and reliable.

Design, Fabrication, and Characterization of Bimorph Micromachined Harvester With Asymmetrical PZT Films

Abstract: This paper presents a high-performance bimorph MEMS cantilever harvester with partially covered asymmetrical functional piezoelectric layers on both sides of a beryllium bronze foil. The optimal PZT coverage length is employed to improve the output power density. The two piezoelectric layers with the controlled different thicknesses for the top and bottom PZT layers can provide three different output powers. Furthermore, a proof mass tungsten bonded at the free end of the cantilever can reduce the resonant frequency. The experimental results showed that the serial-connected bimorph piezoelectric energy harvester can obtain the maximum power density of 26.90 mW/cm3 at the matched loading resistance of 660 $\text{k}\Omega $ under 1.5-g acceleration at the resonant frequency of 38.89 Hz. The normalized power density of the harvester can reach $307.4\,\,\mu \text{W}\cdot \text{g}^{-2}\,\,\cdot $ cm $^{-3}$ . Meanwhile, the harvester provides good stability under 1.5-g acceleration amplitude.

Particle swarm approach to the optimisation of trenched cantilever-based MEMS piezoelectric energy harvesters

Abstract: A micro-electro-mechanical system (MEMS) trenched piezoelectric energy harvester based on a cantilever structure has been proposed. The trenched piezoelectric layer has increased the output voltage and the generated power. It also provides three additional design parameters such as the trench position, depth and length. A particle swarm approach has been used for optimisation of the piezoelectric energy harvester geometry with the aim of finding the optimum design which transfers the maximum harvested power to a definite load. The optimisations and comparisons have been made for unimorph, bimorph, trenched and non-trenched cantilever beams. The results are quite revealing that the generated power for a trenched bimorph energy harvester is much larger than other structures. The optimum design found by particle swarm optimisation algorithm has asymmetric trenches in the top and bottom piezoelectric layers and can generate much more power than the unoptimised structure.

Energy harvesting of a frequency up-conversion piezoelectric harvester with controlled impact

Abstract: Frequency up-conversion is an effective approach to increase the output power of a piezoelectric energy harvester (PEH). In this work, we studied a piezoelectric energy harvesting system, which converts low-frequency vibration from ambient sources to the resonant vibration of the PEH to improve the energy harvesting efficiency. The PEH includes two beams, a pair of rack and pinions, and a slider crank mechanism to retrieve energy from ambient low-frequency vibrations through impacts. The soft driving beam is subjected to a sinusoidal base excitation along the transverse direction. The piezoelectric bimorph undergoes both slow longitudinal motion as well as transverse vibrations. The transverse vibration of the bimorph is induced by impacts which is the vibration source to generate output power. The longitudinal motion of the bimorph is used to control the impact with the soft driving beam, which guarantees the harvester to pump in more kinetic energy from the driving beam. Using the discontinuous dynamic theory, the energy harvesting performance of the impact-controlled system was studied in period one and period two motions. The stability of periodic solutions was investigated and bifurcation diagrams of impact velocities, times and displacements were obtained. The harvested power of the piezoelectric beam versus the based excitation frequency was also obtained, and the results were compared to the power generation of a piezoelectric beam directly subjected to the base excitation along the transverse direction.

A linear inertial piezoelectric actuator using a single bimorph vibrator

Abstract: A linear inertial piezoelectric actuator using a single bimorph vibrator clamped by asymmetrical fixed beam structure is proposed in this paper to achieve extremely simple structure and high stability. It adopted one vibrator to produce the inertial impact force, which is beneficial to simplify the overall architecture. A dynamic model, based on the stiffness-damping vibration model and LuGre friction model, is established to predict the motion of the actuator by Matlab/Simulink. An experimental system is built to test its performance. Experimental results indicate that the stable minimum displacement is 1.9 μm and the maximum repeat error rate reaches 1.1% under a square wave signal of 15 V, 2 Hz with no-load. When the load is 420 g, the minimum displacement is 0.6 μm under 100 V and 2 Hz. Compared with similar actuators, the proposed actuator achieves much higher stable linear motion with a larger stroke and without drawback.