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Showing papers on "Transducer published in 2022"


Journal ArticleDOI
21 Jan 2022-Sensors
TL;DR: In this article , the authors present the physics of guided surface acoustic waves and the piezoelectric materials used for designing SAW sensors and discuss the applications of these sensors and their progress in the fields of biomedical, microfluidics, chemical, and mechano-biological applications.
Abstract: Surface acoustic waves (SAWs) are the guided waves that propagate along the top surface of a material with wave vectors orthogonal to the normal direction to the surface. Based on these waves, SAW sensors are conceptualized by employing piezoelectric crystals where the guided elastodynamic waves are generated through an electromechanical coupling. Electromechanical coupling in both active and passive modes is achieved by integrating interdigitated electrode transducers (IDT) with the piezoelectric crystals. Innovative meta-designs of the periodic IDTs define the functionality and application of SAW sensors. This review article presents the physics of guided surface acoustic waves and the piezoelectric materials used for designing SAW sensors. Then, how the piezoelectric materials and cuts could alter the functionality of the sensors is explained. The article summarizes a few key configurations of the electrodes and respective guidelines for generating different guided wave patterns such that new applications can be foreseen. Finally, the article explores the applications of SAW sensors and their progress in the fields of biomedical, microfluidics, chemical, and mechano-biological applications along with their crucial roles and potential plans for improvements in the long-term future in the field of science and technology.

58 citations


Journal ArticleDOI
TL;DR: In this article , a transparent, stretchable, resilient, and high-performance hydrogel fiber-based bimodal sensor is fabricated by using a polyacrylamide-alginate double network hydrogels, which features high sensitivity (3.17% cm-1), wide working range (18 cm), fast response/recovery speeds (90/90 ms), and impressive pressure sensing performance, including high sensitivity, including 0.91 kPa-1, short response/response time (40/40 ms), low detection limit (63 Pa) and good linearity.
Abstract: The traditional human-machine interaction mode of communicating solely with pressure sensors needs modification, especially at a time when COVID-19 is circulating globally. Here, a transparent, stretchable, resilient, and high-performance hydrogel fiber-based bimodal sensor is fabricated by using a polyacrylamide-alginate double network hydrogel, which features high sensitivity (3.17% cm-1), wide working range (18 cm), fast response/recovery speeds (90/90 ms) and good stability in proximity sensing, and impressive pressure sensing performance, including high sensitivity (0.91 kPa-1), short response/recovery time (40/40 ms), low detection limit (63 Pa) and good linearity. Moreover, the response switch between proximity/pressure modes is measured and non-interfering dual-mode detection is achieved. Notably, the stretchable bimodal sensor is capable of working under 100% tensile strain without degrading the sensing performance. Specifically, the proximity sensor shows good immunity to the strain, while the pressure sensitivity is even promoted. Furthermore, the sensor is tough enough to work normally after punctures from a knife and strikes from a wrench. Notably, the sensor can be used for gesture recognition and subtle pressure detection, such as small water droplets (10 mg), wrist pulse, etc. A 3 × 3 array is further shown for accurate spatial sensing and location identification, verifying the feasibility of its practical application.

41 citations



Journal ArticleDOI
TL;DR: In this article , the authors proposed an air-coupled ultrasonic transducer with a matching system, which includes the matching layers and bonding layers attached to the piezoelectric composite.
Abstract: The tremendous acoustic impedance difference between the piezoelectric composite and air prevents the ultrasonic transition, resulting in low amplitude for the received signal for the composite defect detection using an air-coupled transducer. The matching system, which includes the matching layers and bonding layers attached to the piezoelectric composite, can reduce the acoustic impedance difference and benefit the acoustic transition. In this paper, the fabrication method and modeling for the matching layers are proposed to optimize the transducer performance. The effects of bonding layer material on the transducer performance are also discussed. Experiments were conducted for modeling validation. The proposed model can predict the matching layer acoustic properties with an error of less than 11%. The bonding layer using the same material as the first matching layer can help to increase the sensitivity by about 33% compared to the traditional epoxy bonding. The optimized air-coupled ultrasonic transducer, based on the results of this study, has a 1283 mV amplitude in the air, which is 56% higher than commercially available transducers, and can identify the defects in two typical non-metallic composite materials easily.

29 citations


Journal ArticleDOI
09 Jan 2022-Fibers
TL;DR: In this article , a remotely controlled monitoring system vibrates the PZT patches, acting as actuators by an amplified harmonic excitation voltage, and then transmits them wirelessly and in real time.
Abstract: The addition of short fibers in concrete mass offers a composite material with advanced properties, and fiber-reinforced concrete (FRC) is a promising alternative in civil engineering applications. Recently, structural health monitoring (SHM) and damage diagnosis of FRC has received increasing attention. In this work, the effectiveness of a wireless SHM system to detect damage due to cracking is addressed in FRC with synthetic fibers under compressive repeated load. In FRC structural members, cracking propagates in small and thin cracks due to the presence of the dispersed fibers and, therefore, the challenge of damage detection is increasing. An experimental investigation on standard 150 mm cubes made of FRC is applied at specific and loading levels where the cracks probably developed in the inner part of the specimens, whereas no visible cracks appeared on their surface. A network of small PZT patches, mounted to the surface of the FRC specimen, provides dual-sensing function. The remotely controlled monitoring system vibrates the PZT patches, acting as actuators by an amplified harmonic excitation voltage. Simultaneously, it monitors the signal of the same PZTs acting as sensors and, after processing the voltage frequency response of the PZTs, it transmits them wirelessly and in real time. FRC cracking due to repeated loading ad various compressive stress levels induces change in the mechanical impedance, causing a corresponding change on the signal of each PZT. The influence of the added synthetic fibers on the compressive behavior and the damage-detection procedure is examined and discussed. In addition, the effectiveness of the proposed damage-diagnosis approach for the prognosis of final cracking performance and failure is investigated. The objectives of the study also include the development of a reliable quantitative assessment of damage using the statistical index values at various points of PZT measurements.

28 citations


Journal ArticleDOI
TL;DR: In this article , a coda wave interferometry (CWI)-based high-resolution bolt preload monitoring using a single piezoceramic transducer is proposed.
Abstract: Abstract The traditional monitoring methods can only give warnings for the bolts with severe looseness. However, it is essential for the safety of bolted joints to detect the looseness of bolts at the very early stage. To this end, in this paper, coda wave interferometry (CWI)-based high-resolution bolt preload monitoring using a single piezoceramic transducer is proposed. According to the CWI and acoustoelastic theories, a theoretical model is established and the linear relationship between the time shifts of coda waves and the preload variations of the bolt is derived. An experiment, in which a piezoceramic transducer simultaneously functions as the actuator and sensor, was carried out to verify the effectiveness of the proposed method. Three lead zirconium titanate transducers at different locations of a bolted specimen are tested. The experimental results show that the time shifts of coda waves increase linearly with the decrease of bolt preload and the detectable resolution of bolt preload (DRBP) is up to 0.326%. The DRBP value proves that the proposed technique can successfully monitor bolt looseness at the very early stage. In addition, a comparison study is carried out between the CWI-based method and the energy-based wavelet packet decomposition (WPD) method, and the result shows that the preload sensitivity of the CWI-based method is about six times higher than that of the WPD approach. Therefore, the CWI-based method is an effective way for the in situ monitoring of bolt looseness, especially in the embryonic stage.

23 citations


Journal ArticleDOI
TL;DR: In this article , a planar 5-coil mTMS transducer was developed to allow controlling the maximum of the induced electric field (E-field) within a cortical region approximately 30 mm in diameter.

20 citations


Journal ArticleDOI
TL;DR: In this article, a planar 5-coil mTMS transducer was designed and manufactured to allow controlling the maximum of the induced electric field (E-field) within a cortical region approximately 30mm in diameter.

20 citations


Journal ArticleDOI
TL;DR: An overview of recent developments in ultrasound transducer technologies that use a variety of material strategies and device designs based on both the piezoelectric and photoacoustic mechanisms is provided in this paper .
Abstract: Ultrasound is extensively studied for biomedical engineering applications. As the core part of the ultrasonic system, the ultrasound transducer plays a significant role. For the purpose of meeting the requirement of precision medicine, the main challenge for the development of ultrasound transducer is to further enhance its performance. In this article, an overview of recent developments in ultrasound transducer technologies that use a variety of material strategies and device designs based on both the piezoelectric and photoacoustic mechanisms is provided. Practical applications are also presented, including ultrasound imaging, ultrasound therapy, particle/cell manipulation, drug delivery, and nerve stimulation. Finally, perspectives and opportunities are also highlighted.

19 citations


Journal ArticleDOI
TL;DR: In this paper , the authors evaluated the performance of 6 commercially available ultrasound transducer arrays to identify the optimal characteristics for transfontanelle photoacoustic imaging, based on vasculature depth and blood density in tissue using ex vivo sheep brain.
Abstract: Transfontanelle ultrasound imaging (TFUI) is the conventional approach for diagnosing brain injury in neonates. Despite being the first stage imaging modality, TFUI lacks accuracy in determining the injury at an early stage due to degraded sensitivity and specificity. Therefore, a modality like photoacoustic imaging that combines the advantages of both acoustic and optical imaging can overcome the existing TFUI limitations. Even though a variety of transducers have been used in TFUI, it is essential to identify the transducer specification that is optimal for transfontanelle imaging using the photoacoustic technique. In this study, we evaluated the performance of 6 commercially available ultrasound transducer arrays to identify the optimal characteristics for transfontanelle photoacoustic imaging. We focused on commercially available linear and phased array transducer probes with center frequencies ranging from 2.5MHz to 8.5MHz which covers the entire spectrum of the transducer arrays used for brain imaging. The probes were tested on both in vitro and ex vivo brain tissue, and their performance in terms of transducer resolution, size, penetration depth, sensitivity, signal to noise ratio, signal amplification and reconstructed image quality were evaluated. The analysis of selected transducers in these areas allowed us to determine the optimal transducer for transfontanelle imaging, based on vasculature depth and blood density in tissue using ex vivo sheep brain. The outcome of this evaluation identified the two most suitable ultrasound transducer probes for transfontanelle photoacoustic imaging.

19 citations


Journal ArticleDOI
TL;DR: In this article , it was shown that the structures of GPCRs bound to these interaction partners available today do not reveal a clear conformational basis for signaling bias, which would have enabled the rational design of biased GRCR ligands.

Journal ArticleDOI
TL;DR: In this paper , a load and vibration transducer (FLVT) was developed using a 3D fused deposition modeling (FDM) approach, which has the pressure measurement sensitivity of 0.01274 nm kPa−1 for the earth pressure below 150 kPa.
Abstract: A fibre Bragg grating (FBG)-based load and vibration transducer (FLVT) was developed using a 3D fused deposition modelling (FDM) approach. A newly FLVT was designed by the equal-strength cantilever beam in which the FBG sensors were embedded in the beam during the FDM process. The temperature effect was eliminated by the temperature sensor in the vibration sensing unit. The parameters of the proposed FLVT was examined by the finite element method. The simulated results were matched well with the theoretical analysis results and laboratory calibration results. The proposed transducer has the pressure measurement sensitivity of 0.01274 nm kPa−1 for the earth pressure below 150 kPa. In addition, the proposed transducer could accurately measure low-frequency vibration signals with maximum frequency of 4 Hz and the maximum displacement amplitude of 4 mm with sensitivity of 117.6 pm g−1. The measurement accuracy and stability were carried out. Results shown that the maximum relative errors between the calculation results and the experimental results was 1.3%. The effect of vibration direction was also analysed for the proposed FLVT. The results indicated that the transversal vibration has less influence on the longitudinal vibration. The outcome of this study indicated that the proposed FLVT provide a newly approach for the measurement of earth pressure and soil vibration in one transducer which is quit suit for soil mass.

Journal ArticleDOI
TL;DR: In this article , the authors demonstrate a miniaturized acoustic detector capable of tomographic imaging with spread functions whose width is below 20 µm, based on an optical resonator fabricated in a silicon-photonics platform coated by a sensitivityenhancing elastomer.
Abstract: Medical ultrasound and optoacoustic (photoacoustic) imaging commonly rely on the concepts of beam-forming and tomography for image formation, enabled by piezoelectric array transducers whose element size is comparable to the desired resolution. However, the tomographic measurement of acoustic signals becomes increasingly impractical for resolutions beyond 100 µm due to the reduced efficiency of piezoelectric elements upon miniaturization. For higher resolutions, a microscopy approach is preferred, in which a single focused ultrasound transducer images the object point-by-point, but the bulky apparatus and long acquisition time of this approach limit clinical applications. In this work, we demonstrate a miniaturized acoustic detector capable of tomographic imaging with spread functions whose width is below 20 µm. The detector is based on an optical resonator fabricated in a silicon-photonics platform coated by a sensitivity-enhancing elastomer, which also effectively eliminates the parasitic effect of surface acoustic waves. The detector is demonstrated in vivo in high-resolution optoacoustic tomography.

Journal ArticleDOI
TL;DR: It is shown that the proposed mapping algorithm successfully estimates the position of a sample’s edges, which enables the localisation of edges and/or the welded joints, when implemented on a mobile magnetic robotic platform.

Journal ArticleDOI
TL;DR: In this paper , the authors performed a numerical simulation on corrosion damage identification using embedded piezoceramic transducers, where three groups of PZT sensors in depth, width and longitudinal directions of the beam were simulated to evaluate corrosion damage rate correlated to concrete/rebar parameters including mass loss, cross-section loss, elastic modulus, strength and bond-slip relationship at steel-concrete interface.

Journal ArticleDOI
TL;DR: In this article, a microwave transducer for room-temperature gas sensor integrated on a wearable device was proposed, where the ultra-narrowband microwave filter was designed as microwave transducers, and the microwave sensing measurements were extended to reflected coefficient.
Abstract: The innovative application of microwave transduction technology in the field of gas sensors make it possible to develop wireless passive room-temperature gas sensor integrated on wearable device. Herein, the ultra-narrowband microwave filter was designed as microwave transducer device, and the microwave sensing measurements were extended to reflected coefficient. Meanwhile, the SnO2/bionic porous (BP) carbon composites based thick film were deposited on the coupled line spacing blank surface via blade coating method. According to the SnO2 nanoparticles were well distributed on BP carbon with abundant micro pores, the gas adsorption and desorption can be enhanced, and the sensor response signal base on microwave transduction was finally improved. Without the influence of temperature and humility, the proposed SnO2/BP carbon microwave gas sensor exhibited excellent NH3 sensing behavior at room temperature including wide concentration range (10–200 ppm), relatively fast response and recovery rate, superior selectivity, as well as good reversibility and stability. More importantly, the dielectric constant of microwave sensor has been proved strongly correlation with injected ammonia concentration. This work further proves the feasibility and frontier of microwave transduction technology in gas sensor application.

Journal ArticleDOI
TL;DR: In this paper , a comprehensive review of the practical applications of capacitated micromachined ultrasonic transducers (CMUTs) has been presented, and the necessary details of the device properties and experimental niceties were briefly covered.
Abstract: Capacitive micromachined ultrasonic transducer (CMUT) was introduced as an alternative to the piezoelectric thick-film-based transducers in medical imaging applications. Gradually, CMUTs have been investigated in almost all the applications in acoustics due to their superior transduction properties. CMOS compatible process flow and limitless possibilities of miniaturization made CMUT a preferred choice for the ultrasound industry. This article comprehensively reviews all the applications in which CMUT was used until now. Such a complete review of the practical applications of CMUT has not been reported elsewhere. A topicwise presentation approach is adopted, and wherever possible, the necessary details of the device properties and experimental niceties were briefly covered.

Journal ArticleDOI
TL;DR: In this paper , a fiber Bragg grating (FBG) sensor with three-dimensional (3D) fused deposition modeling (FDM) approach is proposed for effective stress measurement in soil mass.
Abstract: A novel fiber Bragg grating (FBG) sensor with three-dimensional (3D) fused deposition modeling (FDM) approach is proposed for effective stress measurement in soil mass. The three-diaphragm structure design is developed to measure earth and water pressures simultaneously. The proposed transducer has advantages of small size, high sensitivity, low cost, immunity to electromagnetic interference and rapid prototyping. The working principle, design parameters, and manufacturing details are discussed. The proposed transducer was calibrated for earth and water pressures measurement by using weights and a specially designed pressure chamber, respectively. The calibration results showed that the wavelength of the transducer was proportional to the applied pressure. The sensitivity coefficients of the earth and water pressures were 12.633 nm/MPa and 6.282 nm/MPa, respectively. Repeated tests and error analysis demonstrated the excellent stability and accuracy of the earth and water pressure measurements. The performance of the proposed transducer was further verified by a model experimental test and numerical analysis, which indicated that the proposed transducer has great potential for practical applications.

Journal ArticleDOI
29 Oct 2022-Sensors
TL;DR: In this paper , the use of piezoelectric lead zirconate titanate (PZT) transducers for the examination of the efficiency of an innovative strengthening technique of reinforced concrete columns and beam-column joint (BCJ) is presented and commented on.
Abstract: Recent research has indicated that the implantation of a network of piezoelectric transducer patches in element regions of potential damage development, such as the beam–column joint (BCJ) area, substantially increases the efficacy and accuracy of the structural health monitoring (SHM) methods to identify damage level, providing a reliable diagnosis. The use of piezoelectric lead zirconate titanate (PZT) transducers for the examination of the efficiency of an innovative strengthening technique of reinforced concrete (RC) columns and BCJs is presented and commented on. Two real-scale RC BCJ subassemblages were constructed for this investigation. The columns and the joint panel of the second subassemblage were externally strengthened with carbon fiber-reinforced polymer (C-FRP) ropes. To examine the efficiency of this strengthening technique we used the following transducers: (a) PZT sensors on the ropes and the concrete; (b) tSring linear variable displacement transducers (SLVDTs), diagonally installed on the BCJ, to measure the shear deformations of the BCJ panel; (c) Strain gauges on the internal steel bars. From the experimental results, it became apparent that the PZT transducers successfully diagnosed the loading step at which the primary damage occurred in the first BCJ subassemblage and the damage state of the strengthened BCJ during the loading procedure. Further, data acquired from the diagonal SLVDTs and the strain gauges provided insight into the damage state of the two tested specimens at each step of the loading procedure and confirmed the diagnosis provided by the PZT transducers. Furthermore, data acquired by the PZT transducers, SLVDTs and strain gauges proved the effectiveness of the applied strengthening technique with C-FRP ropes externally mounted on the column and the conjunction area of the examined BCJ subassemblages.

Journal ArticleDOI
TL;DR: In this paper, an improved technique for sensing damage initiation and progression in thermoplastic resin composite plate specimens is presented, which uses a nonlinear ultrasonic (NLU) technique called S ideband P eak C ount I ndex or SPC-I.

Journal ArticleDOI
TL;DR: In this paper , an improved SPC-I technique was proposed to detect damage initiation and progression in thermoplastic resin composite plate specimens using a nonlinear ultrasonic (NLU) technique called Sideband Peak Count Index.

Journal ArticleDOI
TL;DR: In this paper , the authors demonstrate how acoustic holograms can produce controlled thermal patterns in absorbing media at ultrasonic frequencies using time-reversal methods and manufactured using 3D-printing.
Abstract: Holograms can shape wavefronts to produce arbitrary acoustic images. In this work, we experimentally demonstrate how acoustic holograms can produce controlled thermal patterns in absorbing media at ultrasonic frequencies. Magnetic resonance imaging (MRI)-compatible holographic ultrasound lenses were designed by time-reversal methods and manufactured using 3D-printing. Several thermal holographic patterns were measured using MRI thermometry and a thermographic camera in gelatin-milk phantoms and in an ex vivo liver tissue. The results show that acoustic holograms enable spatially controlled heating in arbitrary regions. Increasing the temperature using low-cost and MRI-compatible holographic transducers might be of great interest for many biomedical applications, such as ultrasound hyperthermia, where the control of specific thermal patterns is needed.

Journal ArticleDOI
TL;DR: In this paper , a novel implementation of FSATs for guided wave inspections is presented, where the spiral electrodes on a Piezoelectric (PZT) plate bonded on a supporting aluminum plate are patterned through patterning.
Abstract: This paper presents a novel implementation of Frequency Steerable Acoustic Transducers (FSATs) for guided waves (GWs) inspections. Unlike the conventional phased array systems, which demand a large number of transducers and complex wiring, FSATs benefit from inherent directional properties for generation and sensing ultrasonic guided waves, resulting in significant hardware simplification and cost reductions for GWs-based systems. The FSATs exploit the frequency-dependent spatial filtering effect, leading to a direct relationship between the direction of propagation and the frequency content of the transmitted signal. The proposed Piezoceramic FSAT is fabricated through patterning the spiral electrodes on a Piezoelectric (PZT) plate bonded on a supporting aluminum plate. In light of the need to investigate the influence of the generated stiffness caused by the PZT plate on the coupling behavior between the FSAT and the aluminum plate, Finite Element (FE) simulations were carried out. Furthermore, experimental validations were conducted using a Scanning Laser Doppler Vibrometer (SLDV) to highlight the directional capabilities of such devices. The results show that the generation of directional GWs in a host structure is substantially improved thanks to the high actuation strength of Piezoceramic materials employed in the proposed transducer.

Journal ArticleDOI
TL;DR: Guo et al. as discussed by the authors proposed a physics-informed deep neural network, named GuwNet, based on a unidirectional oblique-focusing (UOF) high-frequency, high-order shear horizontal guided wave electromagnetic acoustic transducer (EMAT) to quantify microcrack defects more accurately.
Abstract: It is challenging to apply deep learning in professional fields that lack big data support, especially in industrial structure health assessments using ultrasonic guided wave nondestructive testing (NDT) method. To solve this problem, one feasible solution is to introduce the concept of NDT physics into a deep neural network to compensate for the network's poor predictive abilities when trained on small datasets. Therefore, we propose a physics-informed deep neural network, named GuwNet, based on a unidirectional oblique-focusing (UOF) high-frequency, high-order shear horizontal guided wave electromagnetic acoustic transducer (EMAT) to quantify microcrack defects more accurately. First, the designed focused-transmission omnidirectional-reception UOF-EMAT can produce pure high-frequency, high-order guided waves. Through a circumferential arrangement of multiple receiving transducers, the maximum amount of information can be obtained regarding the reflected waves of the defect. This method solves the inherent problems of an EMAT (i.e., low energy conversion efficiency) and achieves effective detection of microcrack defects. Second, we study the quantification principle of microcrack defects suitable for UOF-EMAT, and propose a deep neural network using physical knowledge regarding this theory. We rationally design the network structure based on the quantitative principles and logic obtained from this article. In addition, feedback and feedforward loss functions suitable for evaluating different forms of variables are proposed to integrate the physical concepts of ultrasonic guided wave testing into the neural network training. Finally, we verify the performance of the proposed GuwNet based on the UOF-EMAT. Compared with traditional nonphysics-informed methods, the length, depth, and direction of the quantification errors are reduced to 0.127 mm, 0.279% dt , and 1.843°, respectively, and the average quantification error is reduced by more than 80%.

Journal ArticleDOI
TL;DR: In this paper , the authors present a brief overview of the history, current situation, and future perspective of piezoelectric single crystals (SCs), and they believe that the main research in the next century is high d33 SCs with a high composition uniformity and low energy SC growth methods, such as solid state SC growth, low-loss SC transducer manufacturing technique, and improved poling process.
Abstract: Piezoelectric materials have been developed since early 1900s and many research had been conducted on the composition and process to obtain higher piezoelectric constants ( d33 ). Within composition research, lead perovskite relaxor piezoelectric single crystals (SCs) of Pb(Mg1/3Nb2/3)O3-lead titanate PbTiO3 type have been actively studied since 1990s because of their outstanding pC/N compared with those of the conventional Pb(Zr,Ti)O3 ceramics. A major driving force of these SC research has been promoted by mass production of ultrasound transducers and array probes for medical diagnostic systems since early 2000s. However, higher d33 material and process research for these ultrasound devices are almost saturated. In this review article, we present a brief overview of the history, current situation, and future perspective of piezoelectric SCs. The authors believe that the main research in the next century is high d33 SCs with a high composition uniformity and low-energy SC growth methods, such as solid-state SC growth, low-loss SC transducer manufacturing technique, and improved poling process. This is a big technical challenge for all the scientists; however, the relatively large market of medical ultrasound has been expanded year by year, and we hope that the community is motivated to solve such technical problems in the near future.

Journal ArticleDOI
01 Sep 2022-Matter
TL;DR: In this article , a subcutaneously implantable flexible ultrasound energy harvesting system that integrates a triboelectric nanogenerator (TENG) transducer and a power management circuit into a single flexible printed circuit board was designed.

Journal ArticleDOI
TL;DR: In this article , a nonlinear relationship model between feature variables and the resonant frequency was established based on the input-output mapping function of back propagation neural network, and particle swarm optimization (PSO) was used to optimize the initial weight and threshold of BP neural network to obtain the best parameter combination, thereby improving the output accuracy.

Journal ArticleDOI
TL;DR: In this paper , the authors reviewed the work done for three decades on 2-D ultrasound sparse arrays for medical applications and discussed the main shortcomings associated with the use of sparse arrays, the related countermeasures and the next steps envisaged in the development of innovative arrays.
Abstract: An ultrasound sparse array consists of a sparse distribution of elements over a 2-D aperture. Such an array is typically characterized by a limited number of elements, which in most cases is compatible with the channel number of the available scanners. Sparse arrays represent an attractive alternative to full 2-D arrays that may require the control of thousands of elements through expensive application-specific integrated circuits (ASICs). However, their massive use is hindered by two main drawbacks: the possible beam profile deterioration, which may worsen the image contrast, and the limited signal-to-noise ratio (SNR), which may result too low for some applications. This article reviews the work done for three decades on 2-D ultrasound sparse arrays for medical applications. First, random, optimized, and deterministic design methods are reviewed together with their main influencing factors. Then, experimental 2-D sparse array implementations based on piezoelectric and capacitive micromachined ultrasonic transducer (CMUT) technologies are presented. Sample applications to 3-D (Doppler) imaging, super-resolution imaging, photo-acoustic imaging, and therapy are reported. The final sections discuss the main shortcomings associated with the use of sparse arrays, the related countermeasures, and the next steps envisaged in the development of innovative arrays.

Journal ArticleDOI
TL;DR: In this paper , a Bayesian mapping technique (Occupancy grid mapping) was used to map the boundaries of an irregular sample in a pseudo-pulse-echo mode, which successfully estimates the position of a sample's edges.

Journal ArticleDOI
TL;DR: In this paper , the stability of PEDOT:PSS OECTs is demonstrated with continuous measurements of the drain current, and the results show that these OECs are ready for biosensing applications requiring accurate continuous monitoring.
Abstract: Organic electrochemical transistors (OECTs) are a burgeoning biosensing transducer platform due to their intrinsic amplification, high transconductance, and biocompatibility. To be successful in real world biosensing applications, however, stable performance should be demonstrated to avoid false analyte readings that could lead to dangerous misdiagnosis. This work demonstrates the stability of carefully prepared OECTs using commercially available PEDOT:PSS as the channel layer. These devices exhibit more than 99% retention of the baseline current over 50 transfer curve cycles and, importantly, after several changes in electrolyte solution. Furthermore, impressive stability is demonstrated during continuous measurements of the drain current. These results show that PEDOT:PSS OECTs are ready for biosensing applications requiring accurate continuous monitoring.