0.36BiScO3-0.64PbTiO3/Epoxy 1-3-2 High-Temperature Composite Ultrasonic Transducer for Non-destructive Testing Applications.

The development of high-temperature nondestructive testing (NDT) requires ultrasonic transducers with good temperature resistance and high sensitivity for improved detection efficiency. Piezoelectric composite can improve the performance of transducers because of its high electromechanical coupling coefficient and adjustable acoustic impedance. In this study, 1-3-2 composites and 1-3-2 high-temperature composite ultrasonic transducers (HTCUTs) based on 0.36BiScO3-0.64PbTiO3 (BSPT), which are preferred piezoelectric materials at 200°C-300°C, and high-temperature epoxy with a center frequency of 6 MHz were designed and fabricated. From 25°C to 250°C, 1-3-2 composites show a higher electromechanical coupling coefficient kt especially at high temperatures (~0.53 at 25°C, and ~0.64 at 250°C) than monolithic BSPT (~0.5). The signal of the pulse-echo response of 1-3-2 HTCUTs is distinguishable up to 250 °C and remains stable (Vpp~500 mV) below 150°C, exhibiting higher sensitivity (improved by 7 dB) than that of monolithic BSPT high-temperature ultrasonic transducers (HTUTs). Bandwidth has been greatly enhanced especially at high temperatures (~103250°C) compared with that of monolithic BSPT HTUTs(~30250°C). To verify the excellent performance, B-mode scanning imaging measurement of a stepped steel block and defect location detection of a steel block were performed, showing the potential for high-temperature NDT applications.

Acoustic hologram-induced virtual in vivo enhanced waveguide (AH-VIEW).

Optical imaging and phototherapy in deep tissues face notable challenges due to light scattering. We use encoded acoustic holograms to generate three-dimensional acoustic fields within the target medium, enabling instantaneous and robust modulation of the volumetric refractive index, thereby noninvasively controlling the trajectory of light. Through this approach, we achieved a remarkable 24.3% increase in tissue heating rate in vitro photothermal effect tests on porcine skin. In vivo photoacoustic imaging of mouse brain vasculature exhibits an improved signal-to-noise ratio through the intact scalp and skull. These findings demonstrate that our strategy can effectively suppress light scattering in complex biological tissues by inducing low-angle scattering, achieving an effective depth reaching the millimeter scale. The versatility of this strategy extends its potential applications to neuroscience, lithography, and additive manufacturing.

Multimodal ultrasound imaging for diagnostic differentiation of sclerosing adenosis from invasive ductal carcinoma.

Background: Sclerosing adenosis (SA) is a common proliferative benign lesion without atypia in the breast that may mimic invasive ductal carcinoma (IDC) on medical imaging, leading to it often being misdiagnosed and mistreated. Consequently, the purpose of this study was to assess the diagnostic value of multimodal ultrasound imaging in distinguishing SA from IDC. Methods: Multimodal ultrasound imaging, including automated breast volume scan (ABVS), elasticity imaging (EI), and color Doppler flow imaging (CDFI), were performed on 120 consecutive patients comprising 122 breast lesions (54 SA, 68 IDC). All lesions were pathologically confirmed. Multimodal ultrasound imaging features were compared between the two groups. Binary logistic regression analysis based on ABVS, EI, and CDFI was conducted to formulate a logistic regression equation for differentiating SA from IDC. The diagnostic performances of ABVS, EI, CDFI, and their combination were compared by the receiver operating characteristic (ROC) curve analysis. Results: The sensitivity, specificity, and accuracy of ABVS, EI, CDFI, and their combination in differentiating SA from IDC were, respectively, 75.00%, 72.22%, and 73.77%; 86.76%, 72.22%, and 80.33%; 73.53%, 64.81%, and 69.67%; and 88.24%, 74.07%, and 81.97%. Combining multimodal ultrasound imaging yielded an area under the curve (AUC) of 0.895 (95% confidence interval: 0.827-0.943), which was higher than that of ABVS, EI, and CDFI, with AUC values of 0.736, 0.795, and 0.692, respectively, and the difference was statistically significant (ABVS vs. combined model, P<0.001; CDFI vs. combined model, P<0.001; EI vs. combined model, P<0.001). There was no significant difference in the diagnostic efficacy among the three imaging modalities (ABVS vs. EI, P=0.266; ABVS vs. CDFI, P=0.4671; EI vs. CDFI, P=0.051). Compared with those in IDC, the calcification (16.67% vs. 57.35%; P<0.001) and retraction phenomena in the coronal planes (18.52% vs. 57.35%; P<0.001) were less common in patients with SA, while circumscribed margin (38.89% vs. 5.88%; P<0.001), vascularity grade 0-I (64.81% vs. 26.47%; P<0.001), and elasticity scores 1-3 (72.22% vs. 13.24%; P<0.001) were more frequently found in patients with SA. Patients with SA were significantly younger than were patients with IDC (43±11 vs. 54±11 years; P<0.001), and the lesion size was smaller in patients with SA than in those with IDC (median size 1.0 cm; interquartile range (IQR), 0.9 cm vs. median size 1.3 cm; IQR, 1.3 cm; P<0.001). Conclusions: The preliminary results suggested that multimodal ultrasound imaging can improve the diagnostic accuracy of SA and provide additional information for differential diagnosis of SA and IDC.

Ultra-High Frequency Self-Focusing Ultrasonic Sensors With Half-Concave Geometry for Visualization of Mouse Brain Atrophy.

Ultra-high frequency (>100 MHz) acoustic waves feature biocompatibility and high sensitivity and allow biomedical imaging and acoustic tweezers. Primarily, excellent spatial resolution and broad bandwidth at ultra-high frequency is the goal for pathological research and cell selection at the cellular level. Here, we propose an efficient approach to visualize mouse brain atrophy by self-focused ultrasonic sensors at ultra-high frequency with ultra-broad bandwidth. The numerical models of geometry and theoretically predicted acoustic parameters for half-concave piezoelectric elements are calculated by the differential method, which agrees with measured results (lateral resolution: 24 µm, and bandwidth: 115% at -6 dB). Compared with the brain slices of 2-month-old mouse, the atrophy visualization of the 6-month-old mouse brain was realized by C-mode imaging with an acoustic microscopy system, which is a potential prospect for diagnosis and treatment of Alzheimer's disease (AD) combined with neuroscience. Meanwhile, the acoustic properties of the brain slices were quantitatively measured by the acoustic microscopy. These encouraging results demonstrate the promising application for high-resolution imaging in vitro biological tissue with ultra-high frequency self-focusing ultrasonic sensors.

Design, Synthesis, and Antiproliferative Activity of Selective Histone Deacetylases 6 Inhibitors Containing a Tetrahydropyridopyrimidine Scaffold.

The development of selective histone deacetylase 6 inhibitors (sHDAC6is) is being recognized as a therapeutic approach for cancers. In this paper, we designed a series of novel tetrahydropyridopyrimidine derivatives as sHDAC6 inhibitors. The most potent compound, 8-(2, 4-bis(3-methoxyphenyl)-5, 8-dihydropyrido [3, 4-d]pyrimidin-7(6H)-yl)-N-hydroxy-8-oxooctanamide (8f), inhibited HDAC6 with IC50 of 6.4 nM, and showed > 48-fold selectivity over other subtypes. In Western blot assay, 8f elevated the levels of acetylated α-tubulin in a dose-dependent manner. In vitro, 8f inhibited RPMI-8226, HL60, and HCT116 tumor cells with IC50 of 2.8, 3.20, and 3.25 µM, respectively. Moreover, 8f showed good antiproliferative activity against a panel of tumor cells.

Phase-Optimized Multi-Step Phase Acoustic Metasurfaces for Arbitrary Multifocal Beamforming.

Focused ultrasound featuring non-destructive and high sensitivity has attracted widespread attention in biomedical and industrial evaluation. However, most traditional focusing techniques focus on the design and improvement of single-point focusing, neglecting the need to carry more dimensions of multifocal beams. Here we propose an automatic multifocal beamforming method, which is implemented using a four-step phase metasurface. The metasurface composed of four-step phases improves the transmission efficiency of acoustic waves as a matching layer and enhances the focusing efficiency at the target focal position. The change in the number of focused beams does not affect the full width at half maximum (FWHM), revealing the flexibility of the arbitrary multifocal beamforming method. Phase-optimized hybrid lenses reduce the sidelobe amplitude, and excellent agreement is observed between the simulation and experiments for triple-focusing beamforming metasurface lenses. The particle trapping experiment further validates the profile of the triple-focusing beam. The proposed hybrid lens can achieve flexible focusing in three dimensions (3D) and arbitrary multipoint, which may have potential prospects for biomedical imaging, acoustic tweezers, and brain neural modulation.

Determining whether hydrological processes drive carbon source and sink conversion shifts in a large floodplain-lake system in China.

Lake carbon (C) cycling is a key component of the global C cycle and associated C source and sink processes. The partial pressure of carbon dioxide (pCO2) and carbon dioxide (CO2) exchange flux at the lake-air interface (Fc) are controlled by complex physical, chemical, and biological mechanisms. It would be instructively significant to determine whether hydrological processes drive conversion shifts between C sources and sinks in floodplain-lake systems. Findings from this study show that exogenous input and in situ metabolism related to photosynthesis, respiration, and organic matter degradation were the main driving mechanisms of CO2 absorption and release in a large floodplain-lake system (i.e., Lake Poyang). Moreover, the intense and frequent water-level fluctuations inherent to floodplain-lakes may also have a direct or indirect impact on C cycling processes and CO2 exchange rates in floodplain-lake systems via their effect on physical processes, inorganic C transport, in-situ metabolic processes. We confirmed the potential of C source and sink conversion in floodplain-lakes under hydrological fluctuations, and strengthen the understanding of driving mechanisms of C source and sink conversion in floodplain systems.

An Optimized Miniaturized Ultrasound Transducer for Transcranial Neuromodulation.

Transcranial ultrasound stimulation (TUS) is a young neuromodulation technology, which uses ultrasound to achieve non-invasive stimulation or inhibition of deep intracranial brain regions, with the advantages of non-invasive, deep penetration, and high resolution. It is widely considered to be one of the most promising techniques for probing brain function and treating brain diseases. In preclinical studies, developing miniaturized transducers to facilitate neuromodulation in freely moving small animals is critical for understanding the mechanism and exploring potential applications. In this article, a miniaturized transducer with a half-concave structure is proposed. Based on the finite element simulation models established by PZFlex software, several ultrasound transducers with different concave curvatures were designed and analyzed. Based on the simulation results, half-concave focused ultrasonic transducers with curvature radii of 5 mm and 7.5 mm were fabricated. Additionally, the emission acoustic fields of the ultrasonic transducers with different structures were characterized at their thickness resonance frequencies of 1 MHz using a multifunctional ultrasonic test platform built in the laboratory. To verify the practical ability for neuromodulation, different ultrasound transducers were used to induce muscle activity in mice. As a result, the stimulation success rates were (32 ± 10)%, (65 ± 8)%, and (84 ± 7)%, respectively, by using flat, #7, and #5 transducers, which shows the simulation and experimental results have a good agreement and that the miniaturized half-concave transducer could effectively converge the acoustic energy and achieve precise and effective ultrasonic neuromodulation.

Single-Beam Acoustic Tweezer Prepared by Lead-Free KNN-Based Textured Ceramics.

Acoustic tweezers for microparticle non-contact manipulation have attracted attention in the biomedical engineering field. The key components of acoustic tweezers are piezoelectric materials, which convert electrical energy to mechanical energy. The most widely used piezoelectric materials are lead-based materials. Because of the requirement of environmental protection, lead-free piezoelectric materials have been widely researched in past years. In our previous work, textured lead-free (K, Na)NbO3 (KNN)-based piezoelectric ceramics with high piezoelectric performance were prepared. In addition, the acoustic impedance of the KNN-based ceramics is lower than that of lead-based materials. The low acoustic impedance could improve the transmission efficiency of the mechanical energy between acoustic tweezers and water. In this work, acoustic tweezers were prepared to fill the gap between lead-free piezoelectric materials research and applications. The tweezers achieved 13 MHz center frequency and 89% -6 dB bandwidth. The -6 dB lateral and axial resolution of the tweezers were 195 µm and 114 µm, respectively. Furthermore, the map of acoustic pressure measurement and acoustic radiation calculation for the tweezers supported the trapping behavior for 100 µm diameter polystyrene microspheres. Moreover, the trapping and manipulation of the microspheres was achieved. These results suggest that the KNN-based acoustic tweezers have a great potential for further applications.

Ultrawide Bandwidth High-Frequency Ultrasonic Transducers With Gradient Acoustic Impedance Matching Layer for Biomedical Imaging.

The high-frequency ultrasonic transducers with larger bandwidths yield excellent imaging performance in the biomedical field. However, achieving perfect acoustic impedance matching from the piezo-element to the target medium in the operating frequency spectrum is still a challenge. Conventional matching layers are mostly fabricated by only one or two uniform materials which are limited by their acoustic property. We propose a novel composite matching layer with gradient acoustic impedance based on a 1-3 gradient composite structure and multilevel matching theory. The proposed gradient-composite matching layer applied for ultrasonic transducer provides efficient impedance matching and ultrawide bandwidth which can significantly improve the quality of biomedical imaging. The active aperture size of the matching layer is 5× 5 mm2, and the overall thickness for five equivalent layers is 115 [Formula: see text]. The -6-dB bandwidth and the center frequency obtained by the ultrasonic transducer equipped with the 1-3 gradient composite matching layer are 141.7% and 22.3 MHz, respectively. The exceedingly good imaging performance of the fabricated ultrasonic transducer was demonstrated by the tungsten wire phantom and study on the biological tissues of a zebrafish and porcine eyeball. The theoretical and experimental results provide a novel train of thought for improving the quality of biomedical ultrasonic imaging.

High-Frequency 0.36BiScO3-0.64PbTiO3 Ultrasonic Transducer for High-Temperature Imaging Application.

( 1- x )BiScO3- x PbTiO3 (BS-PT) ceramics have excellent piezoelectricity and high Curie temperature at its morphotropic phase boundary (MPB) ( x = 0.64 ), so it is a promising piezoelectric material for fabricating high-temperature ultrasonic transducer (HTUT). Electric properties of 0.36BS-0.64PT ceramics were characterized at different temperatures, and an HTUT with the center frequency of about 15 MHz was designed by PiezoCAD based on the measuring results. The prepared HTUT was tested in a silicone oil bath at different temperatures systematically. The test results show that the HTUT can maintain a stable electrical resonance until 290 °C and get a clear echo response until 250 °C with slight changes of the center frequency. Then, a stepped metal block submerged in silicone oil was imaged by the HTUT until 250 °C. Velocity of silicone oil and axial resolution of the HTUT at different temperatures was calculated. The results verify the capability of 0.36BS-0.64PT-based HTUT for high-temperature ultrasonic imaging applications.

Optimized Backing Layers Design for High Frequency Broad Bandwidth Ultrasonic Transducer.

Ultrasonic transducers with broad bandwidth are considered to have high axial resolution and good ultrasound scanning flexibility for the clinical applications. The limitations of spatial resolution due to bandwidth are of great concern in ultrasound medical imaging. The method of acoustic impedance matching between the piezoelectric element and medium is commonly used to obtain broad bandwidth and high resolution. In this study, an optimized backing layer design was proposed to broaden the bandwidth by adding a tunable acoustic impedance matching layer of backing (AIMLB) between the backing layer and the piezoelectric ceramic element. The Mason equivalent circuit method was used to analyze the effect of the backing material composition and its structure on the bandwidth of the transducer. The optimized transducer was simulated using the finite-element method with the PZFlex software. Based on the PZFlex simulations, a 20-MHz ultrasonic transducer using the AIMLB with a bandwidth of approximately 92.29% was fabricated. The experimental results were in good agreement with the simulations. The ultrasonic imaging indicated that the designed ultrasonic transducer with an additional AIMLB had high performance with good imaging capability.

Effects of Composition Segregation in PMN-PT Crystals on Ultrasound Transducer Performance.

This study investigates the relationship between the composition segregation in lead magnesium niobate-lead titanate (PMN-PT; PMN-29%PT, PMN-29.5%PT, PMN-30%PT, PMN-30.5%PT, and PMN-31%PT) single crystals within morphotropic phase boundary (MPB) and the corresponding ultrasonic transducer performance through PiezoCAD modeling and real transducer testing. For five crystals with compositions distributed across the main body of a crystal ingot, the piezoelectric coefficient and free relative permittivity values were measured to vary by over 30%, whereas the transducer bandwidth and center frequency values were modeled to change by less than 10%. For the single-element ultrasonic transducers fabricated using those crystals without matching layers, the variations of -6-dB bandwidth, insertion loss, receiver-free field voltage response, and center frequency were measured to be 9.61%, -15.23%, 9.76%, and 1.41%, respectively, confirming the modeling results. Using the Mason and Krimholtz, Leedom, and Matthaei (KLM) models, it is found that the relatively stable transducer performance can be attributed to the relatively consistent electromechanical coupling coefficient, acoustic impedance, and clamped relative permittivity originated from the stable elastic compliance properties among the crystals of various compositions. It is expected that the relatively stable performance could be extended to multielement transducers with matching layers for the same contributing mechanisms. Our results suggest that it is possible to use crystal plates of different compositions within the MPB region, obtained from one and the same ingot, to fabricate a batch of ultrasonic transducers that will exhibit a similar performance, significantly reducing the cost of materials.

Adjustable Acoustic Field Controlled by "Ultrasonic Projector" on Ultrasound Application.

The control of acoustic field has great potential in many applications such as medical treatment, neuro-modulation, and bio-imaging. Recently, acoustic lenses and phased arrays have become common ways of controlling acoustic fields. However, the shortcomings of the two ways are obvious. Acoustic lenses lack flexibility after design, and phased arrays have complicated structures and need to adjust the parameters of each array element. In this work, we propose an alternative for sound field control using a flexible and adjustable "acoustic projector," and two symmetric mirrors are used to change the direction of propagation of an acoustic wave produced by a piezoelectric element and realize acoustic focusing in the target region. The 2-D "acoustic projector" model was built in finite element simulation, and the feasibility was verified with an actual prototype. The sound intensity produced by the piezoelectric element at different horizontal and vertical positions along the target area can be accurately controlled by two adjustable mirrors. When the angle of the mirror ranges from 30° to 40°, the focal depth can change from 39 to 140 mm. Furthermore, the focus can be controlled in a sector with an angle of 60°. The "acoustic projector" demonstrates simple but precise control of acoustic fields and may broaden their applicability. To show its imaging ability, the three groups of target balls at different positions were imaged and their position information by scanning the mirrors in simulation was given.

Vertically stratified water source characteristics and associated driving mechanisms of particulate organic carbon in a large floodplain lake system.

Particulate organic carbon (POC) is an important component of lake organic carbon (C) pools, of which different factors drive vertical distributions and sources. This study used the dual stable isotope (δ13C and δ15N) approach to investigate vertical POC sources and drivers in a large floodplain lake system. Findings showed that POC composition gradually changed from endogenous dominant to exogenous dominant sequentially from the surface layer to the bottom layer of Lake Poyang. Environmental factors associated with phytoplankton photosynthesis as well as nutrient levels primarily drove surface POC. Moreover, soil erosion, sediment deposition, and resuspension strongly affected POC distribution and composition in the middle and bottom layers of the lake. POC sources were also affected by factors associated with vertical mixing, such as wind speed and water depth. Litter from C3 plants significantly contributed to POC concentrations in the middle and bottom layers of the lake. Results from this study can benefit our overall understanding of the potential driving mechanisms of lake C cycling processes, aquatic ecosystem functions, and pollutant migration.

FOXD3-induced miR-133a blocks progression and metastasis of colorectal cancer through regulating UBA2.

Background and Aim: Some studies have verified that miR-133a played an inhibitory role in several cancers. Whereas, the effect of miRNA-133a in colorectal cancer (CRC) has not been fully elucidated. Our study aims to confirm UBA2 as a direct target gene of miRNA-133a and explore the upstream modulatory molecules of miR-133a. In addition, their impacts on the biological characteristics of CRC cells were assessed. Methods: QRT-PCR analyzed miR-133a expression levels in colorectal cells including HCT116, SW48 cells and human normal colorectal cell line NCM460. A serial biological experiment assessed miR-133a effects on cell proliferation, migration, invasion and apoptosis capacities in HCT116 and SW48 cells. MiRNA targeting gene prediction and a dual luciferase assay were employed to confirm miR-133a-targeted UBA2. Transcription factors (TFs) FOXD3 was identified as an upstream regulator of miR-133a via JASPAR. The influence of miR-133a and FOXD3 on UBA2 expression was analyzed by qRT-PCR or western blot. Results: miR-133a was lowly expressed in CRC cells. High miRNA-133a expression suppressed the proliferation, migration, invasion and enhanced apoptosis capacities of CRC cells. MiR-133a targeted the UBA2 mRNA 3'UTR area and reduced UBA2 protein expression. We also unveiled that FOXD3 high-expression significantly raised miR-133a expression and diminished UBA2 expression. We also discovered that high miR-133a expression augmented the effects of elevated FOXD3 expression on CRC cell proliferation, migration and invasion, whereas, low miR-133a expression generated the opposite outcomes. Conclusion: FOXD3 induced miRNA-133a directly targeting UBA2 could affect the progression and growth of CRC.

Construction of methylation-associated nomogram for predicting the recurrence-free survival risk of stage I-III lung adenocarcinoma.

Aim: The aim of our study was to investigate a methylation-associated predictor for prognosis in patients with stage I-III lung adenocarcinoma (LUAD). Methods: A DNA methylation-based signature was developed via univariate, least absolute shrinkage and selection operator and multivariate Cox regression models. Results: We identified a 14-site methylation signature that was correlated with recurrence-free survival of stage I-III lung adenocarcinoma patients. By receiver operating characteristic analysis, we showed the high ability of the 14-site methylation signature for predicting recurrence-free survival. In addition, the nomogram result showed a satisfactory predictive value. Conclusion: We successfully identified a DNA methylation-associated nomogram which can predict recurrence-free survival in patients with stage I-III lung adenocarcinoma.

Lay abstract Non-small-cell lung cancer patients have a high death rate as a result of cancer recurrence, which can lead to a dismal prognosis. Our study aimed to determine a novel DNA methylation-related biomarker for predicting the recurrence-free survival of stage I­III lung adenocarcinoma patients via comprehensive bioinformatics analysis. A prognostic model was developed and verified according to regression analysis. A high predictive ability of the 14-site methylation signature was determined. Additionally, we constructed a nomogram based on methylation-related risk score and several clinicopathological factors. In conclusion, an effective 14-site methylation signature was discovered which may act as a potential hallmark for stage I­III lung adenocarcinoma prognosis, and a DNA methylation-related nomogram was developed to promote the individual treatment of patients with stage I­III lung adenocarcinoma.

Sediment carbon short-term response to water carbon content change in a large floodplain-lake system.

After carbon (C) enters a lake through surface runoff and atmospheric deposition, most of it, being influenced by the environmental conditions of the basin, is deposited into lake sediment, thus, becoming one of the most important C pools in the world. Therefore, it is critical to understand sediment response characteristics under the context of increasing C concentrations in lake water. Based on the changes of sediment C concentration at different depths in Poyang Lake, belonging to China's large floodplain-lake system, we revealed the sediment C short-term response characteristics to changes in lake water C concentrations as well as their associated impacting factors. We found that dissolved total carbon (DTC) concentrations increased by 25.78% in winter compared to spring, while total carbon (TC) sediment concentrations increased by only 4.37% during the corresponding period. Specifically, we found that there was a hysteresis effect in the response of sediment C to the increase of water C concentration in the short term. When DTC concentrations in water were below a threshold value (12.50 mg/L), sediment TC concentrations were generally maintained at approximately 5.79 mg/kg. We also believed that biological and environmental factors and sediment stratification characteristics collectively resulted in this sediment C hysteresis effect. Among these factors and characteristics, phytoplankton can affect sediment C response by changing C absorption and utilization in water or cause a synergistic effect along with environmental factors, which is the key link that causes this C sediment hysteresis effect to occur. Furthermore, we found that the combined effect of sediment C from different depths also resulted in a hysteresis effect in C deposition.

Optimization Design of Ultrasonic Transducer With Multimatching Layer.

An optimization design strategy is developed for ultrasonic transducer (UT) with multimatching layer to improve its performance. The piezoelectric equivalent circuit model is used to determine the optimization interval of matching layer, and the PiezoCAD software is used to simulate the performance of UT with multimatching layer. The neural network (NN) models are trained by the simulation data to characterize the relationship between the thickness of matching layer and performance of UT. Then, the multiobjective optimality criteria for UT is established based on its performance parameters, including center frequency (CF), -6 dB bandwidth (BW) and pulsewidth (PW). The thickness of matching layer is optimized by particle swarm optimization (PSO) algorithm. According to the designed performance, the optimized copper thickness and parylene thickness are about 17.76 and [Formula: see text], respectively. The simulation results of UT with the optimized multimatching layer well agree with the designed targets. Also, CF, -6 dB BW, and PW of the fabricated UT with the optimized multimatching layer are 5.672 MHz, 50.08%, and [Formula: see text], respectively, which nearly achieve the designed performance. In addition, the performance of UT with the optimized multimatching layer is much better than that of UT without matching layer. Moreover, compared with UT with single or double matching layers determined by the quarter wavelength theory, the UT with the optimized multimatching layer has better comprehensive performance. Finally, the fabricated UT with the optimized multimatching layer is used to measure the thickness of testing block, and the relative errors are all less than 1.0%, which implies that the optimized UT has excellent performance.

The forbidden band and size selectivity of acoustic radiation force trapping.

Acoustic micro-beams produced by highly focused ultrasound transducer have been investigated for micro-particle and cell manipulation. Here we report the selective trapping of microspheres via the acoustic force using the single acoustical beam. The forbidden band theory of acoustic radiation force trapping is proposed, which indicates that the trapping of particles via the acoustic beam is directly related to the particle diameter-to-beam wavelength ratio as well as excitation frequency of the ultrasonic acoustic tweezers. Three tightly focused LiNbO3 transducers with different center frequencies were fabricated for use as selective single beam acoustic tweezers (SBATs). These SBATs were capable of selectively manipulating microspheres of sizes 5-45 µm by adjusting the wavelength of acoustic beam. Our observations could introduce new avenues for research in biology and biophysics by promoting the development of a tool for selectively manipulating microspheres or cells of certain selected sizes, by carefully setting the acoustic beam shape and wavelength.