Showing papers on "Transducer published in 2017"

Highly efficent on-chip direct electronic-plasmonic transducers

Abstract: In one embodiment, an on-chip electronic-plasmonic transducer is provided that is capable of both direct plasmon generation and detection at high efficiencies. The electronic-plasmonic transducer includes a metal-insulator-metal junction formed from a first wire constructed of a first metal, a tunneling barrier material in contact with the first wire, and a second wire made from a second metal in contact with the tunneling barrier material. A plasmonic waveguide is formed as a contiguous part of the second wire, such that the waveguide is directly coupled to the MIM junction. The electronic-plasmonic transducer can both directly generate and detect plasmons, such that it may be configured on-chip as either a plasmon source or a plasmon detector. The electronic-plasmonic transducer may be used to form an on-chip plasmon-based frequency multiplier or plasmon amplifier, among other usages.

Optically driven ultra-stable nanomechanical rotor.

Abstract: Nanomechanical devices have attracted the interest of a growing interdisciplinary research community, since they can be used as highly sensitive transducers for various physical quantities. Exquisite control over these systems facilitates experiments on the foundations of physics. Here, we demonstrate that an optically trapped silicon nanorod, set into rotation at MHz frequencies, can be locked to an external clock, transducing the properties of the time standard to the rod’s motion with a remarkable frequency stability f r/Δf r of 7.7 × 1011. While the dynamics of this periodically driven rotor generally can be chaotic, we derive and verify that stable limit cycles exist over a surprisingly wide parameter range. This robustness should enable, in principle, measurements of external torques with sensitivities better than 0.25 zNm, even at room temperature. We show that in a dilute gas, real-time phase measurements on the locked nanorod transduce pressure values with a sensitivity of 0.3%. Nanomechanical sensors that rely on intrinsic resonance frequencies usually present a tradeoff between sensitivity and bandwidth. In this work, the authors realise an optically driven nanorotor featuring high frequency stability and tunability over a large frequency range.

Design and Optimization of Ultrasonic Wireless Power Transmission Links for Millimeter-Sized Biomedical Implants.

Abstract: Ultrasound has been recently proposed as an alternative modality for efficient wireless power transmission (WPT) to biomedical implants with millimeter (mm) dimensions. This paper presents the theory and design methodology of ultrasonic WPT links that involve mm-sized receivers (Rx). For given load (R L ) and powering distance (d), the optimal geometries of transmitter (Tx) and Rx ultrasonic transducers, including their diameter and thickness, as well as the optimal operation frequency (f c ) are found through a recursive design procedure to maximize the power transmission efficiency (PTE). First, a range of realistic f c s is found based on the Rx thickness constrain. For a chosen f c within the range, the diameter and thickness of the Rx transducer are then swept together to maximize PTE. Then, the diameter and thickness of the Tx transducer are optimized to maximize PTE. Finally, this procedure is repeated for different f c s to find the optimal fc and its corresponding transducer geometries that maximize PTE. A design example of ultrasonic link has been presented and optimized for WPT to a 1 mm 3 implant, including a disk-shaped piezoelectric transducer on a silicon die. In simulations, a PTE of 2.11% at fc of 1.8 MHz was achieved for RL of 2.5 kΩ at d = 3 cm. In order to validate our simulations, an ultrasonic link was optimized for a 1 mm3 piezoelectric transducer mounted on a printed circuit board (PCB), which led to simulated and measured PTEs of 0.65% and 0.66% at f c of 1.1 MHz for RL of 2.5 kΩ at d = 3 cm, respectively.

Design and Verification of a Rail-Borne Energy Harvester for Powering Wireless Sensor Networks in the Railway Industry

Abstract: Design, modeling, simulation, and vibration testing related to electromagnetic energy harvesters are investigated in this paper. A rail-borne electromagnetic energy harvester with copper-beads spacing is proposed and fabricated, the suitable for harvesting vibration-induced energy of the wheelset/track system. A vehicle-track model considering vehicle traveling load is constructed and numerically solved by fast explicit integration methods. An electromagnetic model is established to predict the induced voltage. The track irregularity power spectrum density is applied as excitation source on the track. Based on the calculation results, both the resonant harvester and the magnetic levitation harvester are designed. The solution utilizes copper beads as radial spacing, which guarantees reliable unidirectional movement of magnets inside a multilayer-multirow coil. Vibration tests are conducted with the proposed track-borne device, and a hydraulic driven system is exploited to generate the realistic wheelset/rail interaction force. The proposed rail-borne energy harvester can be mounted to the track easily and extensively. The magnetic levitation harvester offers an approach for harvesting broadband low-frequency (3–7Hz) wheelset/track interaction with the rail displacement of 0.6 to 1.2 mm. For the resonant harvester, the output power of 119 mW and the output peak-peak voltage of 2.32 V are achieved with the rail displacement of 1.2 mm, the coil height of 48 mm, the load resistance of 45 $\Omega $ , the coil inductance of 105.572 mH, and 3000 numbers of turns. Furthermore, a dc–dc boost converter is proposed, which is capable of converting the alternating voltage of the transducer into 5 V/10-mA dc output at the resonant frequency of 6 Hz, the rail displacement of 2 mm, and the induced voltage of 3.4 V.

Optimised Signal Processing for Nonlinear Ultrasonic Nondestructive testing of Complex Materials and Biological Tissues

Abstract: In this thesis the possibility of nonlinear ultrasonic NDT is investigated for complex materials and biological tissues. The delayed TR-NEWS signal processing methodis developed, which is based on the TR-NEWS method. TR-NEWS is a method well-suited for materials with complex structure: it allows spatio-temporal focusing of a long ultrasonic chirp signal to the region near the receiving transducer, forming an impulse pulse. The received signal power and SNR are increased as a result.Delayed TR-NEWS allows the use of this focused wave pulse as a new basis for either the signal optimisation or, alternatively, for the detection of nonlinearity by the breakdown of linear superposition. This method is used in physical experiments and simulations. The physical experiments are made on an undamaged CFRP block and a porcine skin sample. The skin is tested in a synchronised acoustomechanical setup specially designed in the course of this thesis. In 1D pseudospectral simulations for CFRP, it is determined that while classical nonlinearity cannot probably be detected in ultrasonic NDT, it could be possible to detect nonclassical nonlinear effects such as those from cracks and microdamage.Physical experiments and 2D FEM simulations of linear, undamaged CFRP are compared for studying the delayed TR-NEWS method, its applicability in optimising the focused wave, and also for creating an interaction of waves at the focusing region with a linear superposition prediction. This suggests the possibility of detecting nonlinearities by comparing the actual signal from interaction to the linear prediction.Finally, more 2D simulations are conducted for CFRP with a single contact gap nonlinearity near the focusing region. The nonlinearity is measured by PI and delayed TR-NEWS. It is determined that delayed TR-NEWS is able to detect the defect at least as well as the PI method. It is ascertained that the PM hysteresis model could describe the nonclassical nonlinearity of damaged materials and biological tissues. Asynchronised acoustomechanical test setup is created to test such multiscale nonlinearity. The simultaneous mechanical load test and ultrasonic delayed TR-NEWS test can be used to measure the mechanical properties of skin

A Low-Power Wireless Piezoelectric Sensor-Based Respiration Monitoring System Realized in CMOS Process

Abstract: This paper presents a methodology of monitoring respiration pattern using piezoelectric transducer incorporating CMOS integrated circuits for signal processing and data transmission. As a proof of concept, the system has been tested by placing electrodes on human chest using adhesive hydrogel to detect the pulsatile vibration due to respiration. The system can be used either as a wearable device itself or alternatively can be attached to a jacket or a chest belt. The front-end transducer is a piezoelectric material-based sensor, which is comprised of a ferroelectric polymer named polyvinylidene-fluoride (PVDF). PVDF is also biocompatible, which makes the sensor suitable to be used as a wearable device. The charge produced by the sensor is converted to a proportional voltage signal with the help of a charge amplifier designed in a standard 130-nm CMOS process with eight metal and one poly layer. The analog voltage signal acquired from the charge amplifier is then converted into a digital signal using a reconfigurable pipelined analog-to-digital converter for ease of transmission. An impulse-radio ultra-wideband transmitter operating in the frequency range of 3.1–5 GHz is designed for wireless transmission of the data. The smaller footprint, lighter weight, wireless telemetry, and low-cost material along with the low-power integrated CMOS circuitry for signal processing and data transmission make the proposed system an attractive choice for stable respiration monitoring system.

A wearable energy harvester unit using piezoelectric–electromagnetic hybrid technique

Abstract: Wearable sensor electronics require a sustainable electrical power supply to operate. Energy harvesting techniques can be used to convert available nonelectrical energy sources into electrical energy. This paper presents WE-Harvest system, which is a new wearable energy harvesting system that combines piezoelectric and electromagnetic energy harvesters in one unit to generate a combined electrical energy source. Piezoelectric transducers are used to obtain sufficient regulated output voltages while electromagnetic is employed for its high power generation capability. Regular human body motions provide input vibrations for the proposed energy harvester unit. Several conditioning circuit topologies are proposed to efficiently extract energy from the two sources. The experimental results demonstrate that the combined topology enhances the power generation efficiency as well as enables stable output DC voltages. The dependence of energy harvester output on the load and input frequency has also been investigated.

A multi-delay-and-sum imaging algorithm for damage detection using piezoceramic transducers

Abstract: The traditional delay-and-sum imaging algorithm usually requires sending an excitation pulse at each piezoceramic transducer and obtains a damage image by drawing only ellipses. A multi-delay-and-s...

Transducer design for AlN Lamb wave resonators

Abstract: AlN Lamb wave resonators enjoy advanced and attractive properties for enabling the next-generation single-chip radio frequency front-end, but their moderate effective electromechanical coupling coefficient (k2eff) poses a limit to their application in filters and multiplexers. Despite the fact that the reported k2eff enhancement techniques of doped AlN thin films which are expensive and trade off the quality factor (Q), the transducer topology itself extensively impacts the k2eff value. Although an AlN cross-sectional Lame mode resonator exhibiting a k2eff of 6.34% has been demonstrated without the need for changing the piezoelectric material, a detailed study of transducer design for AlN Lamb wave resonators has not been conducted. In this work, we investigate the impact of (i) transducer configurations, (ii) electrode materials, (iii) electrode thicknesses, and (iv) interdigital transducer duty factors on the k2eff dispersive characteristics of one-port AlN Lamb wave resonators by using the finite eleme...

A Front-End ASIC With Receive Sub-array Beamforming Integrated With a $32 \times 32$ PZT Matrix Transducer for 3-D Transesophageal Echocardiography

Abstract: This paper presents a power- and area-efficient front-end application-specific integrated circuit (ASIC) that is directly integrated with an array of $32 \times 32$ piezoelectric transducer elements to enable next-generation miniature ultrasound probes for real-time 3-D transesophageal echocardiography. The $6.1 \times 6.1$ mm2 ASIC, implemented in a low-voltage 0.18- $\mu \text{m}$ CMOS process, effectively reduces the number of receive (RX) cables required in the probe’s narrow shaft by ninefold with the aid of 96 delay-and-sum beamformers, each of which locally combines the signals received by a sub-array of $3 \times 3$ elements. These beamformers are based on pipeline-operated analog sample-and-hold stages and employ a mismatch-scrambling technique to prevent the ripple signal associated with the mismatch between these stages from limiting the dynamic range. In addition, an ultralow-power low-noise amplifier architecture is proposed to increase the power efficiency of the RX circuitry. The ASIC has a compact element matched layout and consumes only 0.27 mW/channel while receiving, which is lower than the state-of-the-art circuit. Its functionality has been successfully demonstrated in 3-D imaging experiments.

Design of HIFU Transducers for Generating Specified Nonlinear Ultrasound Fields

Abstract: Various clinical applications of high-intensity focused ultrasound have different requirements for the pressure levels and degree of nonlinear waveform distortion at the focus. The goal of this paper is to determine transducer design parameters that produce either a specified shock amplitude in the focal waveform or specified peak pressures while still maintaining quasi-linear conditions at the focus. Multiparametric nonlinear modeling based on the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation with an equivalent source boundary condition was employed. Peak pressures, shock amplitudes at the focus, and corresponding source outputs were determined for different transducer geometries and levels of nonlinear distortion. The results are presented in terms of the parameters of an equivalent single-element spherically shaped transducer. The accuracy of the method and its applicability to cases of strongly focused transducers were validated by comparing the KZK modeling data with measurements and nonlinear full diffraction simulations for a single-element source and arrays with 7 and 256 elements. The results provide look-up data for evaluating nonlinear distortions at the focus of existing therapeutic systems as well as for guiding the design of new transducers that generate specified nonlinear fields.

Erratum to “A 200–1380 kHz Quadrifrequency Focused Ultrasound Transducer for Neurostimulation in Rodents and Primates: Transcranial In Vitro Calibration and Numerical Study of the Influence of Skull Cavity”

Abstract: Low intensity transcranial focused ultrasound has been demonstrated to produce neuromodulation in both animals and humans. Primarily for technical reasons, frequency is one of the most poorly investigated critical wave parameters. We propose the use of a quadri-band transducer capable of operating at 200, 320, 850, and 1380 kHz for further investigation of the frequency dependence of neuromodulation efficacy while keeping the position of the transducer fixed with respect to the subject’s head. This paper presents the results of the transducer calibration in water, in vitro transmission measurements through a monkey skull flap, 3-D simulations based on both a $\mu $ -computed tomography ( $\mu $ CT)-scan of a rat and on CT-scans of two macaques. A maximum peak pressure greater than 0.52 MPa is expected at each frequency in rat and macaque heads. According to the literature, our transducer can achieve neuromodulation in rodents and primates at each four frequencies. The impact of standing waves is shown to be most prominent at the lowest frequencies.

Three-dimensional ultrasonic trapping of micro-particles in water with a simple and compact two-element transducer

Abstract: We report a simple and compact piezoelectric transducer capable of stably trapping single and multiple micro-particles in water. A 3D-printed Fresnel lens is bonded to a two-element kerfless piezoceramic disk and actuated in a split-piston mode to produce an acoustic radiation force trap that is stable in three-dimensions. Polystyrene micro-particles in the Rayleigh regime (radius λ/14 to λ/7) are trapped at the focus of the lens (F# = 0.4) and manipulated in two-dimensions on an acoustically transparent membrane with a peak trap stiffness of 0.43 mN/m. Clusters of Rayleigh particles are also trapped and manipulated in three-dimensions, suspended in water against gravity. This transducer represents a significant simplification over previous acoustic devices used for micro-particle manipulation in liquids as it operates at relatively low frequency (688 kHz) and only requires a single electrical drive signal. This simplified device has potential for widespread use in applications such as micro-scale manufac...

Broadband gradient impedance matching using an acoustic metamaterial for ultrasonic transducers

Abstract: High-quality broadband ultrasound transducers yield superior imaging performance in biomedical ultrasonography. However, proper design to perfectly bridge the energy between the active piezoelectric material and the target medium over the operating spectrum is still lacking. Here, we demonstrate a new anisotropic cone-structured acoustic metamaterial matching layer that acts as an inhomogeneous material with gradient acoustic impedance along the ultrasound propagation direction. When sandwiched between the piezoelectric material unit and the target medium, the acoustic metamaterial matching layer provides a broadband window to support extraordinary transmission of ultrasound over a wide frequency range. We fabricated the matching layer by etching the peeled silica optical fibre bundles with hydrofluoric acid solution. The experimental measurement of an ultrasound transducer equipped with this acoustic metamaterial matching layer shows that the corresponding −6 dB bandwidth is able to reach over 100%. This new material fully enables new high-end piezoelectric materials in the construction of high-performance ultrasound transducers and probes, leading to considerably improved resolutions in biomedical ultrasonography and compact harmonic imaging systems.

Identification of Droplet-Flow-Induced Electric Energy on Electrolyte-Insulator-Semiconductor Structure.

Abstract: Recently, various energy transducers driven by the relative motion of solids and liquids have been demonstrated. However, in relation to the energy transducer, a proper understanding of the dynamic behavior of ions remains unclear. Moreover, the energy density is low for practical usage mainly due to structural limitations, a lack of material development stemming from the currently poor understanding of the mechanisms, and the intermittently generated electricity given the characteristics of the water motion (pulsed signals). Here, we verify a hypothesis pertaining to the ion dynamics which govern the operation mechanism of the transducer. In addition, we demonstrate enhanced energy transducer to convert the mechanical energy of flowing water droplets into continuous electrical energy using an electrolyte–insulator–semiconductor structure as a device structure. The output power per droplet mass and the ratio of generated electric energy to the kinetic energy of water drops are 0.149v2 mW·g–1·m–2·s2 and 29...

Transducer placement optimisation scheme for a delay and sum damage detection algorithm

Abstract: Summary In this work, a transducer placement scheme based on wave propagation is proposed, which enhances damage localisation. The method was tailored to seek an optimal transducer network placement for a delay and sum damage detection algorithm. The proposed method determines a coverage index map and utilises a genetic algorithm to determine an optimal transducer network. It can also minimise the impact of faulty transducers, incorporate the effect of stiffeners and different damage types. The method is initially verified using numerically simulated signals. The optimal network outperformed the suboptimal for detection of holes and debonding in a stiffened panel. It is also shown that the coverage index reflected the localisation accuracy. The method is then validated with experimental results and the generated optimal transducer network compared with a suboptimal arrangement. The optimal network is shown to locate an actual crack with significantly higher accuracy than the suboptimal arrangement. © 2016 The Authors. Structural Control and Health Monitoring published by John Wiley & Sons, Ltd.

Self-Focused AlScN Film Ultrasound Transducer for Individual Cell Manipulation.

Abstract: Precise cell positioning is indispensable in the fields of biophysics and cellular biology. Acoustic microbeam produced by a highly focused ultrasound transducer has recently been investigated for a particle or cell manipulation. By virtue of the relatively good piezoelectric property, Sc doped AlN film was introduced for a highly focused ultrasound transducer application. Using a sputtering approach, a self-focused AlScN film based device has been designed, fabricated, and characterized at a frequency of ∼230 MHz. It had a narrow lateral beam width (∼8.2 μm). The AlScN ultrasound transducer was not only shown to be capable of remote controlling a single 10 μm polystyrene microsphere in distilled water, but also demonstrated to possess the capability to manipulate without contact individual 10 μm epidermoid carcinoma cell in two dimensions within a range of hundreds of micrometers in phosphate buffered saline. Most importantly, the cell manipulation was realized in continuous mode and no switch-on and -of...

Phononic Crystal Waveguide Transducers for Nonlinear Elastic Wave Sensing

Abstract: Second harmonic generation is one of the most sensitive and reliable nonlinear elastic signatures for micro-damage assessment. However, its detection requires powerful amplification systems generating fictitious harmonics that are difficult to discern from pure nonlinear elastic effects. Current state-of-the-art nonlinear ultrasonic methods still involve impractical solutions such as cumbersome signal calibration processes and substantial modifications of the test component in order to create material-based tunable harmonic filters. Here we propose and demonstrate a valid and sensible alternative strategy involving the development of an ultrasonic phononic crystal waveguide transducer that exhibits both single and multiple frequency stop-bands filtering out fictitious second harmonic frequencies. Remarkably, such a sensing device can be easily fabricated and integrated on the surface of the test structure without altering its mechanical and geometrical properties. The design of the phononic crystal structure is supported by a perturbative theoretical model predicting the frequency band-gaps of periodic plates with sinusoidal corrugation. We find our theoretical findings in excellent agreement with experimental testing revealing that the proposed phononic crystal waveguide transducer successfully attenuates second harmonics caused by the ultrasonic equipment, thus demonstrating its wide range of potential applications for acousto/ultrasonic material damage inspection.

High-performance electromechanical transduction using laterally-constrained dielectric elastomers part I: Actuation processes

Abstract: A dielectric elastomer transducer is a deformable capacitor, and is under development as a sensor, actuator, or generator. Among various geometric configurations, laterally-constrained transducer, also known as pure-shear transducer, is easy to implement and effective to couple mechanical force and electrical voltage. This analytical study reveals that lateral pre-stretch enhances actuation, far exceeding previously reported actuation strokes. Laterally-constrained transducers exhibit complex electromechanical behavior. As voltage increases, an actuator may undergo electromechanical instability, or form wrinkles, or suffer electrical breakdown. We survey the behavior of actuators under all possible states of pre-stretches, and identify five modes of actuation. Our analysis predicts that laterally-constrained actuators can achieve actuation stroke of 1000% for an acrylic elastomer, and 230% for natural rubber. This analysis opens the door to design actuators of simple geometry capable of a very large range of electromechanical actuation.

Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

Abstract: Electromagnetic Acoustic Transducers (EMATs) are a useful ultrasonic tool for non-destructive evaluation in harsh environments due to their non-contact capabilities, and their ability to operate through certain coatings. This work presents a new Rayleigh wave EMAT transducer design, employing geometric focusing to improve the signal strength and detection precision of surface breaking defects. The design is robust and versatile, and can be used at frequencies centered around 1 MHz. Two coils are used in transmission mode, which allows the usage of frequency-based measurement of the defect depth. Using a 2 MHz driving signal, a focused beam spot with a width of 1.3±0.25 mm and a focal depth of 3.7±0.25 mm is measured, allowing for defect length measurements with an accuracy of±0.4 mm and detection of defects as small as 0.5 mm depth and 1 mm length. A set of four coils held under one magnet is used to find defects at orientations offset from normal to the ultrasound beam propagation direction. This EMAT has a range which allows detection of defects which propagate at angles from 16° to 170° relative to the propagation direction over the range of 0–180°, and the setup has the potential to be able to detect defects propagating at all angles relative to the wave propagation direction if two coils are alternately employed as generation coils.

Structural Health Monitoring Using Lamb Wave Reflections and Total Focusing Method for Image Reconstruction

Abstract: This investigation aimed to adapt the total focusing method (TFM) algorithm (originated from the synthetic aperture focusing technique in digital signal processing) to accommodate a circular array of piezoelectric sensors (PZT) and characterise defects using guided wave signals for the development of a structural health monitoring system. This research presents the initial results of a broader study focusing on the development of a structural health monitoring (SHM) guided wave system for advance carbon fibre reinforced plastic (CFRP) composite materials. The current material investigated was an isotropic (aluminium) square plate with 16 transducers operating successively as emitter or sensor in pitch and catch configuration enabling the collection of 240 signals per assessment. The Lamb wave signals collected were tuned on the symmetric fundamental mode with a wavelength of 17 mm, by setting the excitation frequency to 300 kHz. The initial condition for the imaging system, such as wave speed and transducer position, were determined with post processing of the baseline signals through a method involving the identification of the waves reflected from the free edge of the plate. The imaging algorithm was adapted to accommodate multiple transmitting transducers in random positions. A circular defect of 10 mm in diameter was drilled in the plate, which is similar to the delamination size introduced by a low velocity impact event in a composite plate. Images were obtained by applying the TFM to the baseline signals, Test 1 data (corresponding to the signals obtained after introduction of the defect) and to the data derived from the subtraction of the baseline to the Test 1 signals. The result shows that despite the damage diameter being 40 % smaller than the wavelength, the image (of the subtracted baseline data) demonstrated that the system can locate where the waves were reflected from the defect boundary. In other words, the contour of the damaged area was highlighted enabling its size and position to be determined.

Direct-Write Piezoelectric Ultrasonic Transducers for Non-Destructive Testing of Metal Plates

Abstract: Current real time structural health monitoring is implemented by assembling multiple discrete sensors on a structure with each sensor providing only point measurement. The installation of the multiple sensors results in high global cost and low reliability. This paper reports the design, direct-write fabrication, and testing of ultrasonic transducers on a plate structure and a non-destructive testing method for detecting defects using the sensor array comprising the direct-write ultrasonic transducers. The transducers are made of piezoelectric poly(vinylidenefluoride/trifluoroethylene) (P(VDF/TrFE)) polymer coatings that are aerosol-spray deposited and patterned directly on the plate structure to be monitored. The ultrasonic transducers bearing annular array comb electrodes are designed for generating and selectively detecting fundamental antisymmetric Lamb-mode ultrasonic waves in the plate structure. The ultrasonic transducers can serve as both the actuators to generate ultrasonic waves and the sensors to detect ultrasonic waves. The ultrasonic waves propagating through the plate structure contain the information about the structural integrity. With copper bars of different thicknesses introduced at the plate center as mock defects of different severity, the correlation between the transducer response and the defect thickness and hence, the severity is verified. It is also demonstrated that four ultrasonic transducers located at the square plate (100 mm $\times 100$ mm $\times 1.27$ mm) corners forming a transducer array, which can locate the defect on the plate. A short time Fourier transform algorithm and an imaging algorithm are developed for processing signal of the pitch-catch ultrasonic wave spectra to determine the location of the defects, which is verified by experimental results.

A Portable Ultrasound System for Non-Invasive Ultrasonic Neuro-Stimulation

Abstract: Fundamental insights into the function of the neural circuits often follows from the advances in methodologies and tools for neuroscience. Electrode- and optical- based stimulation methods have been used widely for neuro-modulation with high resolution. However, they are suffering from inherent invasive surgical procedure. Ultrasound has been proved as a promising technology for neuro-stimulation in a non-invasive manner. However, no portable ultrasound system has been developed particularly for neuro-stimulation. The utilities used currently are assembled by traditional functional generator, power amplifier, and general transducer, therefore, resulting in lack of flexibility. This paper presents a portable system to achieve ultrasonic neuro-stimulation to satisfy various studies. The system incorporated a high voltage waveform generator and a matching circuit that were optimized for neuro-stimulation. A new switching mode power amplifier was designed and fabricated. The noise generated by the power amplifier was reduced (about 30 dB), and the size and weight were smaller in contrast with commercial equipment. In addition, a miniaturized ultrasound transducer was fabricated using Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-PT) 1–3 composite single crystal for the improved ultrasonic performance. The spatial peak temporal average pressure was higher than 250 kPa in the range of 0.5–5 MHz. In vitro and in vivo studies were conducted to show the performance of the system.

Ultrasonic transducer techniques for ultrasonic surgical instrument

Abstract: Disclosed is a method of fabricating an ultrasonic medical device. The method includes machining a surgical tool from a flat metal stock, contacting a face of a first transducer with a first face of the surgical tool, and contacting a face of a second transducer with an opposing face of the surgical tool opposite the first transducer. The first and second transducers are configured to operate in a D31 mode with respect to the longitudinal portion of the surgical tool. Upon activation, the first transducer and the second transducer are configured to induce a standing wave in the surgical tool and the induced standing wave comprises a node at a node location in the surgical tool and an antinode at an antinode location in the surgical tool.

Excitation and reception of single torsional wave T(0,1) mode in pipes using face-shear d24 piezoelectric ring array

Abstract: Excitation of single fundamental torsional wave T(0, 1) mode is of practical importance in inspecting or monitoring the structural integrity of pipelines, as T(0, 1) wave is the only non-dispersive mode in pipe-like structures. This work presents a piezoelectric ring array to excite and receive single T(0, 1) mode which is made up of a series of equally-spaced face-shear d24 PZT elements around the pipe. Firstly, we proposed that single T(0, 1) mode can be excited by the piezoelectric ring, when the number of d24 PZT elements is slightly greater than n, where F(n, 2) is the highest circumferential order flexural torsional mode within the frequency bandwidth of the drive signal. Then this proposed principle was confirmed by finite element simulations. Later, experimental testing was conducted on a 100 mm outer diameter, 3 mm thick aluminum pipe. Results show that the ring of 24 face-shear d24 PZT elements can suppress all the non-axisymmetric flexural modes at the excitation frequency of 150 kHz so that single T(0, 1) mode is generated. Moreover, such a piezoelectric ring transducer can also filter flexural modes and receive the T(0, 1) mode only at 150 kHz. Note that here the highest circumferential order flexural torsional mode within the frequency bandwidth is F(20, 2), so the experimental results are in good agreement with the proposed principle. The presented ring of face-shear d24 PZT elements is very suitable for severing as the T(0, 1) wave transducer in structural health monitoring system, as it is cost-effective and no external load is required for operation.