Transmitter Transducer Research Articles

Ultrasonic Levitation for Airway Humidification.

This study employs the transmitter part of an ultrasonic proximity sensor to generate a powerful ultrasonic field for medical humidification. This field is created using an arrangement of small ultrasonic transmitter transducers configured in an acoustic levitator-style setup. As droplets pass through this ultrasonic field, they undergo disintegration, leading to an accelerated evaporation process. The research findings highlight a significant change in droplet size distribution due to ultrasonics, resulting in a notable increase in the rate of evaporation. As a result, this study presents a conceptual framework for reimagining humidification devices for lung therapeutic purposes through the utilization of simple sensor technology.

Self-Detachable Through-Metal Acoustic Wireless Power Transfer

Unlike electromagnetic waves, acoustic vibrations waves can be used to transfer power directly through metal structures without being shielded. In this paper, a novel design of a self-detachable acoustic wireless power transfer system that can be used to transfer power through the thickness of a steel plate is presented, which does not require the use of any couplant. Electro-permanent-magnets (EPM's) were used to provide magnetic clamping force along the perimeter of the receiver transducer disc to enhance the coupling to the steel plate, while the transmitter transducer was bonded to the other side of the plate. The EPM clamping force can be switched on/off electronically with low power consumption. Unlike past work reliant on additional bonding materials or liquid/gel couplant, this approach enables the receiver to be attached and detached at will, opening up the possibility of a simple charging pad for unmanned aerial vehicles (UAVs) or other consumer devices for harsh environment applications. Power transfer efficiency up to 63% was achieved, and the effect of varying steel plate thickness and clamping force was also investigated. A finite element model was also constructed to understand the vibration mode shape.

An analysis for unipole acoustic logging while drilling wavefields with varying eccentered collar positions

Abstract The unipole logging while drilling (LWD) tool is a recently developed acoustic logging tool that uses an azimuthal emitting source to generate acoustic waves in the borehole to measure the longitudinal and transverse wave speeds of the surrounding stratum. In this study, the unipole transmitter transducer is modeled as a surface force source, and the analytical solution for unipole LWD wavefield is derived. The received waveforms are composed of infinite-order contributions owing to the directivity of the excitation of the unipole source. Using up to eight lowest-order modes, the acoustic waveforms excited by the unipole are calculated in both soft and hard formations, and then slowness-time coherence and velocity dispersion analysis are performed. The pure mode waves are obtained using the mode wave decomposition method. The influence of tool eccentricity (off-center positioning) on the wavefields excited by the unipole transmitter is also discussed. Based on the addition theorem of the Bessel function, the analytical solution of the received waveforms when the tool is eccentered can be obtained. In soft and hard formations, the received waveforms with tool eccentricities of 0 to 90% are compared. Tool eccentricity has a smaller effect for the soft formation than the hard formation. The received waveforms on the side closest to the borehole wall are also affected most when the tool is off center, with a sharp increase in amplitude in the fast formation and a late arrival wave group in the soft formation. These conclusions are important for the design and data interpretation of a unipole LWD tool.

Novel transmitter transducer for acoustic logging while drilling

In this paper, a new transmitter transducer for an acoustic logging while drilling (ALWD) tool is proposed. The piezoelectric ceramic is cut into two parts based on conventional transducers, and a buffer material is set in the middle. Thus, the radial vibration displacement of the new transducer is larger at the resonant frequency, whereas the longitudinal coupling vibration is significantly reduced. Although conventional transducers have a simple structure, they have large longitudinal vibration displacements, which directly cause strong drill collar waves. These collar waves negatively affect the measurement of formation signals. In this study, the differences in admittance and vibration displacement distribution between a conventional transducer and the new transducer are compared using COMSOL simulation. Finite element simulation results show that the transducer employing soft epoxy resin with a height of 6 mm as the filling material is the most effective. The real axis integral method is used to verify that the longitudinal vibration of the transducer causes strong drill collar waves. Then, sound field and well field experiments are conducted on actual transducers. The experimental results show that the emission voltage response of the new ALWD transducer designed in this study can reach 140 dB, which is 6.22% higher than that of a conventional transducer; moreover, the output voltage increased by 52.81%, directivity improved by 67.82%, and drill collar wave interference decreased by 66%. Therefore, the new transducer can improve the detection performance of ALWD instruments and provide a reference for the design of other transducers.

Broadband Electrical Impedance Matching of Transmitter Transducer for Acoustic Logging While Drilling Tool

Broadband Electrical Impedance Matching of Transmitter Transducer for Acoustic Logging While Drilling Tool

THE BONE MICROSTRUCTURE IDENTIFICATION MODEL BASED ON BACKSCATTER MODE OF ULTRASOUND

Osteoporosis is defined by a decrease in bone mass and a deterioration in bone microstructure. It is a major public health issue and a significant economic burden for both individuals and society. Thus, monitoring bone mass and structure is necessary to prevent bone fragility and osteoporosis. This study aimed to develop a prototype of quantitative ultrasound (QUS) and to evaluate the feasibility of backscatter mode for the bone assessment. Ultrasound (US) signals that propagate through the bone can be characterized by comparing the signal from both transmitter and receiver transducers. The US backscattered signal depends on the characteristic of both medium and transducer. In this study, we analyzed the attenuated signal based on the parameters: type of bone (compact and spongy), type of coupling medium (air, starch, and gel), the angle between transducers and bone (30o, 60o, and 90o), and transducer distance (0, 10, 5, 15, 20 and 25 cm). We use only 1 MHz transducer frequency. The prototype has been evaluated by Digital Oscilloscope and LabVIEW user interface to observe received signals. The results of this study showed that there was a difference in amplitude of the US signal from compact and spongy bones. The amplitude is directly proportional to acoustic impedance and inversely proportional to the distance between transducers. There is a negative correlation between bone microstructure to attenuation, and compact bones have a greater attenuation coefficient than spongy bones.

A lab-on-chip ultrasonic platform for real-time and nondestructive assessment of extracellular matrix stiffness.

Extracellular matrix (ECM) mechanical stiffness and its dynamic change is one of the main cues that directly affects the differentiation and proliferation of normal cells as well as the progression of disease processes such as fibrosis and cancer. Recent advancements in biomaterials have enabled a wide range of polymer matrices that could mimic the ECM of different tissues for a wide range of in vitro basic research and drug discovery. However, most of the technologies utilized to quantify the stiffness of such ECM are either destructive or expensive, and therefore are unsuitable for the in situ, long-term monitoring of variations in ECM stiffness for on-chip cell culture applications. This work demonstrates a novel noninvasive on-chip platform for characterization of ECM stiffness in vitro, by monitoring ultrasonic wave attenuation through the targeted material. The device is composed of a pair of millimeter scale ultrasonic transmitter and receiver transducers with the test medium placed in between them. The transmitter generates an ultrasonic wave that propagates through the material, triggers the piezoelectric receiver and generates a corresponding electrical signal. The characterization reveals a linear (r2 = 0.86) decrease in the output voltage of the piezoelectric receiver with an average sensitivity of -15.86 μV kPa-1 by increasing the stiffnesses of hydrogels (from 4.3 kPa to 308 kPa made with various dry-weight concentrations of agarose and gelatin). The ultrasonic stiffness sensing is also demonstrated to successfully monitor dynamic changes in a simulated in vitro tissue by gradually changing the polymerization density of an agarose gel, as a proof-of-concept towards future use for 3D cell culture and drug screening. In situ long-term ultrasonic signal stability and thermal assessment of the device demonstrates its high robust performance even after two days of continuous operation, with negligible (<0.5 °C) heating of the hydrogel in contact with the piezoelectric transducers. In vitro biocompatibility assessment of the device with mammary fibroblasts further assures that the materials used in the platform did not produce a toxic response and cells remained viable under the applied ultrasound signals in the device.

A Method Combining Measurement Tool and Numerical Simulation for Calculating Acoustic Signals of Ultrasonic Flowmeter

Ultrasonic flowmeters (UFMs) based on the principle of transit time difference are widely used in process industries. The transit time difference is obtained through analyzing received acoustic signals generated by a couple of transducers located upstream and downstream respectively. The quality of received acoustic signal will directly affect the measurement accuracy of UFM. For this reason, a measurement-calculation coupled approach combining measurement tools and numerical simulation for calculating the acoustic signal of UFM is proposed in this paper. The method can predict the acoustic signals of UFM with different flowrates. First, important boundary condition (vibration velocity on transmitter transducer surface) is measured by measurement tool, which can reduce computational complexity and also avoid modeling transmitter transducers. Second, simulating the wave propagation (difficult to access experimentally) within moving medium by using the measured vibration velocity. Third, obtaining the transfer function of receiver by comparing estimated force acting on the receiver transducer surface with measured voltage signal from receiver, which can avoid modeling receiver transducer. Finally, predicting the received acoustic signal at different flowrates by using the transfer function. The rationality of predicted data was validated by comparing experimental and predicted acoustic signal on receiver transducer at different flowrates. A good agreement between simulated and experimental data was obtained, which means that the working processes of the acoustic signal generated by actual transducers inside UFMs can be accurately predicted based on this method. Analysis of the predicted results will provide good guides and advices to the design of UFMs involving actual application.

An ultrasound-based water-cut meter for heavy fuel oil

In order to have on-line measurement of water content in heavy fuel oil (HFO), the so-called water-cut meters are used. Typically, measurements performed by these devices are based on capacitive principle, in which the water-in-oil emulsion acts as the insulation material. In this case, variations in the water/oil ratio affect the dielectric, which causes the capacitance to vary. By contrast, in our approach, water-in-oil emulsions act as the material medium for propagation of ultrasound waves so that the variations in water/oil ratio affect their frequency components. Since we keep the transmitter transducer excitation the same, the received ultrasound signal will vary according to the current characteristics of the fluid. As it is not known in advance which components will be affected by the presence of water, we present a methodology consisting in laboratory experiments in conjunction with Principal Component Analysis (PCA). This methodology leads to an expression that relates the score value issued from PCA and the water content information. In addition to presenting the development of an ultrasound-based water-cut meter, this paper presents some results obtained from both laboratory and field measurements. We could also compare the proposed system with a PCB-based capacitive sensor under field conditions. We verified a maximum difference of 0.2 percentage point between both approaches.

Contextual Application of Pulse-Compression and Multi-frequency Distance-Gain Size Analysis in Ultrasonic Inspection of Forging

Ultrasonic pulse-echo non-destructive testing, combined with Distance Gain Size (DGS) analysis, is still the main method used for the inspection of forgings such as shafts or discs. This method allows the inspection to be carried out, assuring in turns the necessary sensitivity and defect detection capability in most of the cases. However, when testing large or highly attenuating samples with standard pulse-echo, the maximum achievable signal-to-noise ratio is limited by both the beam energy physical attenuation during the propagation and by the inherent divergence of any ultrasound beam emitted by a finite geometrical aperture. To face this issue, the application of the pulse-compression technique to the ultrasonic inspection of forgings was proposed by some of the present authors, in combination with the use of broadband ultrasonic transducers and broadband chirp excitation signals. Here, the method is extended by applying DGS analysis to the pulse-compression output signal. Both standard single-frequency/narrowband DGS and multi-frequency/broadband DGS analyses applied on pulse-compression data acquired on a forging with known defects are tested and compared. It is shown that the DGS analysis works properly with pulse-compression data collected by using a separate transmitter and receiver transducers. Narrowband analysis and broadband analyses provide almost identical results, but the latter exhibits advantages over the traditional method: it allows the inspection frequency to be optimized by using a single pair of transducers and with a single measurement. In addition, the range resolution achieved is higher than the one achievable for the narrowband case.

Exploiting Self-Capacitances for Wireless Power Transfer

Conventional approaches for wireless power transfer rely on the mutual coupling (near-field or far-field) between the transmitter and receiver transducers. As a result, the power-transfer efficiency of these approaches scales non-linearly with the cross-sectional area of the transducers and with the relative distance and respective alignment between the transducers. In this paper, we show that when the operational power-budget requirements are in the order of microwatts, a self-capacitance (SC)-based power delivery has significant advantages in terms of the power transfer-efficiency, receiver form-factor, and system scalability when compared to other modes of wireless power transfer (WPT) methods. We present a simple and a tractable equivalent circuit model that can be used to study the effect of different parameters on the SC-based WPT. In this paper, we have experimentally verified the validity of the circuit using a cadaver mouse model. We also demonstrate the feasibility of a hybrid telemetry system where the microwatts of power, which can be harvested from SC-based WPT approach, is used for back-scattering a radio-frequency (RF) signal and is used for remote sensing of in vivo physiological parameters such as temperature. The functionality of the hybrid system has also been verified using a cadaver mouse model housed in a cage that was retrofitted with 915MHz RF back-scattering antennas. We believe that the proposed remote power-delivery and hybrid telemetry approach would be useful in remote activation of wearable devices and in the design of energy-efficient animal cages used for long-term monitoring applications.

Ultrasonic based determination of apple quality as a nondestructive technology

This research, aimed to apply ultrasonic based technology and develop a portable system for determination of the apple (Golden Delicious) mechanical properties as the quality factor. The main components of the designed portable system are a pair of transmitter and receiver transducers with 40 kHz center frequency, a signal generation unit, a measuring unit of the gain ratio (dB) and phase difference of two signals (input and transmitted), a microcontroller (Atmega 32) and a 16 × 2 LCD display. Mechanical properties of the specimens were distractively measured by an Instron universal testing machine based on the Magness−Taylor method. By combination the physical and ultrasonic attributes and developing the multiple linear regressions, for firmness the model with a good ability of prediction was developed with R and RMSE values of 0.73 and 2.35 N, respectively. For the elastic modulus, the best model had R and RMSE values of 0.64 and 0.18 MPa, respectively. Also for the rupture energy, the model with a high ability of prediction was developed with R and RMSE values of 0.73 and 5.18 mJ, respectively. It was concluded that by using the nondestructive ultrasonic based system to measure the ultrasonic velocity and attenuation of apple, it might be possible to nondestructively assess its mechanical properties.

Designing ocean acoustic waveguide remote sensing for target detecting and tracking

Acoustic sensor used sound wave to transmit pulses into the underwater in order to gain underwater environment information. We developed Ocean Acoustics Waveguide Remote Sensing (OAWRS) instrument. The acoustic signal acquisition system has been designed which used to record the direct, reflected, scattered or echoed signals originated from transmitter transducer, targets or underwater objects. The acquisition system compose of interconnected hardware and software with a simple working principles. The software, which is written under Windows™ and Matlab, controlled the hardware by sending commands to the Transmitter Module located somewhere to generate a sound pulse and the Receiver Module to be ready to receive sound signals. The received sound data may be recorded for further analysis to developed OAWRS algorithm.

Fourier transform of high frequency ultrasonic waves propagated with a transmission mode

When ultrasonic propagates as a wave, the frequencies contained in the propagated waves may carry information regarding to the medium. The transformation of time-domain propagated signals into those of frequency domain is a common digital signal processing (DSP) technic to extract such important information. This requires quite a high resolution of the detection device which relates to the high frequency ultrasonic waves. The advancement of microprocessor technologies enables the complex and fast digital signal processing in the frequency domain. This allows measurement and evaluation using a broadband frequency domain analysis which is effective in the extraction of information contained in the ultrasonic signals. This work presents the implementation of Fourier transform of propagated ultrasonic signals through air medium. The generation of ultrasonic waves employs two pairs of transmitter-receiver ultrasonic transducers which have the center frequencies of 200 kHz and 1 MHz, respectively. The transmitter transducer was excited by a 107.1-ns negative spike to generate ultrasonic waves propagating through the air and converted into an electrical signal by a receiver transducer. This was amplified and recorded as a digital signal for subsequent offline digital signal processing.

Identification and Characterization of Defects in Glass Fiber Reinforced Plastic by Refining the Guided Lamb Waves.

In this paper, the disbond-type defect presented on glass fiber reinforced plastic material is analyzed by refining the guided Lamb wave signals. A segment of wind turbine blade is considered as a test sample. The low-frequency ultrasonic measurement system is used for the non-destructive testing of the test sample using guided waves. The P-1 type macro-fiber composite transducer as a transmitter and contact-type piezoceramic transducer as a receiver are used for the testing of a sample. The disbond type defect having a diameter of 81 mm is detected from the experimental results. To improve the accuracy in locating and sizing the defects and estimation of the time of flight and phase velocity of ultrasonic guided waves in defective region, signal processing algorithm is developed by utilizing the promising properties of various ultrasonic signal processing techniques such as wavelet transform, amplitude detection, two-dimensional Fast-Fourier transform, Hilbert transform and variational mode decomposition. The discrete wavelet transform is used to denoise the guided wave signals and then, the size and location of defects are estimated by amplitude detection. The reflected wave signals from the opposite edge of the sample are removed by applying the two-dimensional Fast-Fourier transform to the experimental B-scan signal. Afterwards, variational mode decomposition and Hilbert transform are used for the phase velocity and time-delay estimation by comparing the instantaneous amplitudes of the defective and defect-free signal. The validation and the demonstration of reproducibility of the algorithm is performed by extracting the features of a 51 mm defect from another experimental B-scan.

A Hybrid Inductive-Ultrasonic Link for Wireless Power Transmission to Millimeter-Sized Biomedical Implants

Ultrasound has recently been utilized for efficient wireless power transmission (WPT) to biomedical implants with millimeter (mm) dimensions and below. However, the power transmission efficiency (PTE) of ultrasonic links reduces significantly in mediums with different acoustic impedances. This brief presents a hybrid inductive-ultrasonic WPT link for powering mm-sized implants that utilizes two cascaded co-optimized inductive and ultrasonic links for WPT through bone/air and tissue, respectively. The ultrasonic link is first optimized based on the implant depth (d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">us</sub> ) and load (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> ) to find the optimal geometries for ultrasonic transducers and operation frequency (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> ). Then, the inductive link is optimized at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> to drive the transmitter (Tx) transducer. A hybrid link was optimized and measured to transfer power to a receiver (Rx) transducer with the diameter of 1.1 mm, loaded by R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> of 2.5 kQ and located at d <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">us</sub> = 3 cm inside castor oil, as the tissue model. The Tx coil was placed in air and spaced from the Rx coil by 3 cm, resulting in a total powering distance (d) of 6 cm. At the optimal f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> of 1.1 MHz, the hybrid link achieved a considerable measured PTE of 0.16%.

An acousto-electric effect logging detector in boreholes

An acousto-electric effect logging detector in boreholes is introduced. The detector can measure the first and second type of acousto-electric effect in the downhole. The acoustic transducer of the detector is composed of a transmitting transducer T and a receiving transducer array R1, R2, and R3, and the electrode is composed of power supply electrodes A and B, and measuring electrodes E1, E2, E3, and E4. The minimum spacing between the transmitter transducer T and the receiving transducer R1 is 2500 mm, and the spacing between the receiving transducer is 300 mm. The spacing of the power supply electrode is 1500 mm, and the spacing of the measuring electrode is 300 mm. The detector circuits include the acoustic transducer excitation circuit, power supply electrode excitation circuit, acoustic signal-processing and acquisition circuit, electrical signal-processing and acquisition circuit, system main control circuit, and telemetry interface circuit. Laboratory and field tests were conducted. The sound pressure of the acoustic transmitting transducer at 1 m is up to 70 kPa. The typical acousto-electric logging signal has been observed from the field test in the downhole formation.

Metrological Validation of a Measurement Procedure for the Characterization of a Biological Ultrasound Tissue-Mimicking Material

The speed of sound and attenuation are important properties for characterizing reference materials such as biological phantoms used in ultrasound applications. There are many publications on the manufacture of ultrasonic phantoms and the characterization of their properties. However, few studies have applied the principles of metrology, such as the expression of the uncertainty of measurement. The objective of this study is to validate a method for characterizing the speed of sound and the attenuation coefficient of tissue-mimicking material (TMM) based on the expression of the measurement of uncertainty. Six 60-mm-diameter TMMs were fabricated, three 10 mm thick and three 20 mm thick. The experimental setup comprised two ultrasonic transducers, acting as transmitter or receiver depending on the stage of the measurement protocol, both with a nominal center frequency of 5 MHz and an element diameter of 12.7 mm. A sine burst of 20 cycles and 20-V peak-to-peak amplitude at 5 MHz excited the transmitter transducer, producing a maximum pressure of 0.06 MPa. The measurement method was based on the through-transmission substitution immersion technique. The speed of sound measurement system was validated using a calibrated stainless-steel cylinder as reference material, and normalized errors were <0.8. The attenuation coefficient measurement method was validated using replicated measurements under repeatability conditions. The normalized error between the two measurement sets was <1. The proposed uncertainty models for the measurements of the speed of sound and the attenuation coefficient can help other laboratories develop their own uncertainty models. These validated measurement methods can be used to certify a TMM as a reference material for biotechnological applications.

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

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 (RL) 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 (fc) are found through a recursive design procedure to maximize the power transmission efficiency (PTE). First, a range of realistic fcs is found based on the Rx thickness constrain. For a chosen fc 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 fcs 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 mm3 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 [Formula: see text] at [Formula: see text]. 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 fc of 1.1 MHz for RL of 2.5 [Formula: see text] at [Formula: see text], respectively.

Optimal resonance configuration for ultrasonic wireless power transmission to millimeter-sized biomedical implants.

In order to achieve efficient wireless power transmission (WPT) to biomedical implants with millimeter (mm) dimensions, ultrasonic WPT links have recently been proposed. Operating both transmitter (Tx) and receiver (Rx) ultrasonic transducers at their resonance frequency (fr) is key in improving power transmission efficiency (PTE). In this paper, different resonance configurations for Tx and Rx transducers, including series and parallel resonance, have been studied to help the designers of ultrasonic WPT links to choose the optimal resonance configuration for Tx and Rx that maximizes PTE. The geometries for disk-shaped transducers of four different sets of links, operating at series-series, series-parallel, parallel-series, and parallel-parallel resonance configurations in Tx and Rx, have been found through finite-element method (FEM) simulation tools for operation at fr of 1.4 MHz. Our simulation results suggest that operating the Tx transducer with parallel resonance increases PTE, while the resonance configuration of the mm-sized Rx transducer highly depends on the load resistance, Rl. For applications that involve large Rl in the order of tens of kΩ, a parallel resonance for a mm-sized Rx leads to higher PTE, while series resonance is preferred for Rl in the order of several kΩ and below.