The acquisition of a high-quality imaging performance by an atomic force microscope is significantly influenced by the motion coupling effect of its key scanning unit, i.e. its piezoelectric tube scanner. In this Letter, to improve its performance, a MIMO model predictive control scheme for reducing this effect is proposed. The proposed controller achieves this by greatly overcoming the problem of tilted characters in the atomic force microscopy (AFM) scanned images. The experimental results are demonstrating the effectiveness of the proposed control technique.

This chapter describes theories and technologies about ultrasound imaging. As a mechanical wave, ultrasound propagates in the imaging zone, and the echoes deliver information about the position and properties of non -uniformities inside the specimen. The most commonly used device for ultrasound transmission and reception is piezoelectric ultrasound transducers and their arrays. Vibration modes and design principles were discussed in detail. Other ultrasound transmission and/ or reception technology include CMUT and optical -based acoustic sensing. Multiple imaging modes are available in ultrasound imaging. Finally, typical ultrasound imaging modes are described, including A -mode, B -mode, M -mode, IUVS, Doppler imaging and harmonic imaging modes.

A microelectromechanical systems piezoelectric transducer capable of measuring static accelerations and acoustic vibrations has been designed and proposed. The transducer is composed of a circular plate on a pillar, which is fixed at the centre and free at the rim so that it resembles a flat cap mushroom. An annular piezoelectric layer has been employed to convert the vibration-induced stress of the plate to a potential difference. The proposed structure has been compared with diaphragm piezoelectric transducers and hydrophones and its superior performance has been verified. Analytical models for both static and dynamic accelerations have been developed, discussed and the output voltage has been formulated, which is in a very good agreement with the finite element analysis. Results show that the maximum sensitivity is achieved when there is an annular piezoelectric layer on the plate around the pillar perimeter. The effect of different geometrical parameters on the transducer performance has been studied. The proposed flat cap mushroom shape piezoelectric transducer could achieve −186.5 dB sensitivity and a very wide bandwidth. Another important advantage of the proposed structure is that by controlling the pillar radius and without changing the plate size, the sensitivity can be enhanced.

In order to maximise the power from a harvester including a great number of piezoelectric transducers (PZTs), the outputs of these transducers should be connected in a suitable way. Since each PZT can be thought of as a non-ideal source, it is also clear that direct serial connection or parallel connection of these PZTs will not be a very good strategy. In this study, a new circuit topology is proposed for the electric connection between PZTs in a harvester including a great number of PZTs. This proposed circuit topology at the same time presents an efficient rectification and regulation strategy for each PZT used. The process of rectification takes place with minimum voltage loss due to the structure of the proposed circuit topology. In addition, the output of the proposed circuit topology can be used directly to charge an energy storage unit in addition to being connected to the input of any interface circuit. An experimental setup was designed to compare the performance of circuit topology proposed in this study in the form of connection used commonly in the literature. With this experimental setup used, various connection forms and the proposed circuit topology were compared under the same conditions.

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.

In a free-standing 400-nm-thick platelet of crystalline ZY-LiNbO₃, narrow electrodes (500 nm) placed periodically with a pitch of a few microns can eXcite standing shear-wave bulk acoustic resonances (XBARs), by utilising lateral electric fields oriented parallel to the crystalline Y-axis and parallel to the plane of the platelet. The resonance frequency of ∼4800 MHz is determined mainly by the platelet thickness and only weakly depends on the electrode width and the pitch. Simulations show quality-factors (Q) at resonance and anti-resonance higher than 1000. Measurements of the first fabricated devices show a resonance Q-factor ∼300, strong piezoelectric coupling ∼25%, (indicated by the large Resonance-antiResonance frequency spacing, ∼11%) and an impedance at resonance of a few ohms. The static capacitance of the devices, corresponds to the imaginary part of the impedance ∼100 Ω. This device opens the possibility for the development of low-loss, wide band, RF filters in the 3–6 GHz range for 4th and 5th generation (4G/5G) mobile phones. XBARs can be produced using standard optical photolithography and MEMS processes. The 3rd, 5th, 7th, and 9th harmonics were observed, up to 38 GHz, and are also promising for high frequency filter design.

This article focuses on the behaviour analysis of an unimorph ring-shaped piezoelectric plate that is used as an actuator in a fluidic valve. First, the system modelling is discussed by using the material mechanical properties of the piezoelectric plate and the non-piezoelectric substrate. That is, two differential equations are established for the displacements along the radial and transverse directions. After that, based on the clamped edge conditions, the transverse displacement solution is obtained as an explicit function of the applied voltage. On this basis, the analytical relationship between the transverse displacement and the applied voltage is displayed. Finally, three different voltages are applied to the ring-shaped piezoelectric plate of a fluidic valve. The measured experimental results are almost consistent to the analytical results, which illustrates the validity of the established system model.

Design of DC–DC converter for harvesting maximum power from the multiple piezoelectric energy harvesters is a challenging task. In this work, a method to obtain maximum power from the multiple piezoelectric energy harvesters for supercapacitor charging is proposed. The method involves acquiring energy from each harvester by time-multiplexed operation of the multi-input buck–boost converter. The maximum power from each harvester is extracted by operating the converter to match the impedance of each harvester to the load impedance. The impedance matching is done by operating the converter with optimal duty cycle. The proposed method is experimentally evaluated, and the charging rate of supercapacitor is found to be higher while charging by the proposed method as compared to charging directly through the rectifier. The proposed method involves a single converter circuit for extracting energy from multiple piezoelectric energy harvesters, so that the component utilisation and its associated losses are very much reduced.

Piezoelectric actuators (PEAs) are widely applied in various nanopositioning equipment. However, the strong hysteresis nonlinearity compromises the positioning accuracy. In this work, a novel modified Bouc-Wen (MBW) model with a polynomial function of the differential of the input is established for modelling the hysteresis nonlinearity of the PEA-actuated nanopositioning stages. The particle swarm optimisation algorithm is adopted to identify the parameters of the MBW model with a set of input–output experimental data. The obtained model with the corresponding identification parameters matches well the experimental data with 0.31% relative error. A feedforward compensator based on the obtained model is also applied to compensate the hysteresis nonlinearity. Experiments are conducted to validate the effectiveness of this approach, and the results show the great improvement of positioning accuracy of the stage.

A 247 mg weight coin-size piezoelectric-driven micro air vehicle (MAV) with four symmetrical distributed bionic flexible wings is presented. The MAV is planar designed and monolithic fabricated via film printed circuit, graphic lasering and lamination process, and is able to be self-assembled by using shape memory polymer (SMP). The SMP can be heated by the flexible circuit and shrink at a large strain, resulting in the self-folding of hinges and self-assembly of MAV from 2D shape into 3D shape. The flexible four-bar mechanism converts the slight vibration of lead zirconate titanate (PZT) actuator into flexible wings’ reciprocation, thereby generating lift force. The response characteristics and motion behaviour of the MAV are experimentally tested. Results suggest that the prototype can be self-assembled to the designed position and achieve a 23.5° reciprocating angle at 134 Hz resonance frequency under 280 V driving signals.