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To address the need for high-resolution imaging in lung nodule detection and overcome the limitations of the shallow imaging depth associated with high-frequency ultrasound and the complex structure of lung tissue, we successfully integrated 50 MHz ultrasound transducers with 18-gauge biopsy needles. Featuring a miniaturized size of 0.6 × 0.5 × 0.5 mm3, the 50 MHz micromachined 1-3 composite transducer was tested to perform mechanical scanning of a nodule within a lung-tissue-mimicking phantom in vitro. The high-frequency transducer demonstrated the ability to achieve imaging with an axial resolution of 30 μm for measuring nodule edges. Moreover, the integrated biopsy needle prototype exhibited high accuracy (1.74% discrepancy) in estimating nodule area compared to actual dimensions in vitro. These results underscore the promising potential of biopsy-needle-integrated transducers in enhancing the accuracy of endoscopic ultrasound-guided fine needle aspiration biopsy (EUS-FNA) for clinical applications. [ABSTRACT FROM AUTHOR]

The overpoling effect of alternating current poling (ACP) was studied on [001]-orientated rhombohedral Pb(Mg1/3Nb2/3)O3-0.26PbTiO3 (PMN-0.26PT) single crystals. Our experimental results showed that the property enhancement from the ACP was remarkable only when the poling cycle number (NL) was kept low. When ACP was continued after the saturation, dielectric and piezoelectric properties gradually dropped down to traditional direct current poled levels or even lower. Such a decrease in material properties caused by the large NL during ACP was defined as the "overpoling effect of ACP" in this study. The following lattice symmetry and domain structure characterization studies were performed through x-ray diffraction (XRD) and piezoelectric force microscopy (PFM) to find the origin of the overpoling effect. The XRD measurements combined with temperature dependence of dielectric properties demonstrated that the field-induced phase transition continued when the samples became overpoled. Further PFM measurements illustrated that the domain density of the overpoled ACP sample was significantly lower than that of the normal one, while the "2R" domain configuration was maintained through the ACP process. In addition, the hysteresis loop characterization indicated large decreases in the coercive fields. The discovered overpoling effect of ACP could help us understand the mechanisms of ACP and optimize the ACP process. [ABSTRACT FROM AUTHOR]

High temperature or temperature nonuniformity has become a serious threat to performance and reliability of high-performance integrated circuits (ICs). Since the temperature in a 3-D IC is mainly determined by a power distribution across tiers, this article proposes a novel method to allocate modules to tiers while exploring a better power distribution according to the hyperparameter optimization technique. In addition, we integrate the sub-3-D thermal mask into the analytical formulation to interleave high power consumption modules in contiguous tiers during distributing modules over placement regions so that it is possible to insert through-silicon vias (TSVs) around high power modules to further reduce the temperature at a later stage. Since the temperature in a tier will be changed every time the locations of TSVs in its lower tier are moved, we also propose a procedure to update the temperature map before refining locations of TSVs. Experimental results have demonstrated that the proposed methodology can effectively reduce the temperature of a 3-D IC with a slight increase in the wirelength. Moreover, its runtime is quite fast. [ABSTRACT FROM AUTHOR]

This article aims to develop a semi-noncontact stress-sensing system using a laser-generated ultrasound (LGU) wave assisted by candle soot nanoparticle (CSNP) composite. While the acoustoelastic effect is commonly targeted to measure the stress level, efforts to combine it with the LGU wave signal have been lacking due to weak signal intensity. In this study, the CSNP-based transducer is designed to potentiate the photoacoustic energy conversion. To demonstrate the wave propagation with the designed parameters, a numerical simulation was first conducted. The experimental results showed that a laser intensity of 6.5 mJ/cm2 was enough to generate the subsurface longitudinal (SSL) wave from the CSNP composite transducer. The normal beam projection is the most effective wave-generation method, exhibiting the highest signal magnitude compared with inclined projection cases. Finally, the laser-assisted stress-sensing system was assessed by increasing the internal pressure of an air tank. The sensitivity of the developed sensor system was estimated to be 0.296 ns/MPa, showing a correlation of 0.983 with the theoretical prediction. The proposed sensing system can be used to monitor the structural integrity of nuclear power plants. [ABSTRACT FROM AUTHOR]

In this article, a flexible piezo-composite transducer composed of the active piezoelectric material (PZT-5H) and passive polymer matrix [polydimethylsiloxane (PDMS)] is developed to achieve excellent flexibility, sensitivity, and bandwidth for biomedical and industrial applications. The flexible electrodes [silver nanowires (AgNWs) mixed with PDMS] are deposited on the transducers using a spray coating method, providing a sufficient conductivity of an electrode through repeated bending tests. The flexible 1–3 composite transducer exhibits robust mechanical flexibility (curved radius <5 mm) without failure due to the stretchable mechanical properties of PDMS and AgNWs network, which indicates that the AgNW/PDMS electrode is a promising alternative to conventional metal-type electrodes, such as Au film. The acoustic characterization suggests that the −6 dB fractional bandwidth (∼49%) and transmitting sensitivity (∼107 mV/V) of the prototyped transducer are promising for nondestructive testing, biomedical imaging, and therapy. [ABSTRACT FROM AUTHOR]

Alternating current (electric field) poling (ACP) was applied on [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-0.3PT) single crystal samples with dimensions of 5 × 1.25 × 1.25 mm3 (with electrodes on the 1.25 × 1.25 mm2 surfaces), and the influence of ACP frequency (fACP) was studied. Compared to those from traditional direct (electric field) poling samples, the piezoelectric coefficient (d33) and free dielectric constant (εT33/ε0) of ACP samples could gain up to a 67% increase to 3200 pC/N and 10 500, respectively. The influence of fACP was studied on two main aspects: saturated properties and dynamic saturation process. In general, ACP samples with lower fACP had higher saturated d33, εT33/ε0, and coupling factor k33, as well as lower dielectric loss and faster saturation speed. The ACP dynamics during the saturation process were studied by measuring the polarization-vs-electric field hysteresis loops (P-E loops). The P-E loops illustrated that the coercive field of ACP samples could be further tuned from 1.84 kV/cm to 3.03 kV/cm by changing fACP (0.1–10 Hz). This work demonstrated the enormous potential of ACP optimization in relaxor-PT single crystal-based low-frequency transducer applications. [ABSTRACT FROM AUTHOR]

The generation of ultrasonic surface waves with a photoacoustic-laser-source has become useful for the noncontact nondestructive testing and evaluation (NDT&E) of materials and structures. In this work, a hybrid ultrasound based NDT&E method is proposed based on the photoacoustic-laser-source as a noncontact Lamb wave generator by incorporating a line-arrayed patterned candle soot nanoparticle-polydimethylsiloxane (CSNPs-PDMS) patch as the signal amplifier and with a narrow bandwidth. The CSNP-PDMS composite has been investigated as the functional patch for its laser energy absorption efficiency, fast thermal diffusion, and large thermoelastic expansion capabilities. The signal amplitude (in mW) from the CSNP-PDMS patch exhibits 2.3 times higher amplitude than the no patch condition and a narrower bandwidth than other conditions. Furthermore, improvement in the sensitivity is also achieved through the selection of the aluminum nitride sensing system. The overall combination of the Lamb wave generation and receiver-sensing system in this study is found to be very promising for a broad range of noncontact NDT&E applications. [ABSTRACT FROM AUTHOR]

This article provides a review of candle-soot nanoparticle (CSNP) composite laser ultrasound transmitters (LUTs) and compares and contrasts this technology with other carbon-composite designs. Among many carbon-based composite LUTs, a CSNP composite has demonstrated its advantages of maximum energy conversion and fabrication simplicity for developing highly efficient ultrasound transmitters. We focus on the advantages and challenges of the CSNP-composite transmitter in the areas of nanostructure design, fabrication procedure, and promising applications. [ABSTRACT FROM AUTHOR]

In this work, the piezoelectric and dielectric properties of [001]-oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals under alternating current poling (ACP) at different temperatures were studied. The piezoelectric coefficients (d33 ∼ 1930 pC/N, d31 ∼ −850 pC/N) and free dielectric permittivity (εT33/ε0 ∼ 7570) reached their highest values when the poling temperature (Tpoling) was 70 °C. Compared with traditional direct current electric field poling at 20 °C, 70 °C-ACP samples showed an enhancement of 40%, 35%, and 49% for d33, d31, and εT33/ε0, respectively. Meanwhile, d33 and εT33/ε0 were enhanced by about 9% when Tpoling increased from 20 °C to 70 °C under ACP, while d31 remained the same value and the dielectric loss was lowered from 0.29% to 0.22%. Moreover, ACP samples with different Tpoling have similar electromechanical coupling factors (k31 ∼ 0.44, kt ∼ 0.60). A discussion of the mechanism for the ACP enhancement was based on the domain observation using piezoresponse force microscopy, and the results showed that the domain densities of ACP samples with different Tpoling were positively correlated with their piezoelectric properties. This work demonstrated the enormous potential of ACP optimization for relaxor-PT single crystal applications. [ABSTRACT FROM AUTHOR]

In this paper, 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-30%PT) single crystal samples were poled using an alternating current (electric field) poling (ACP) method. Compared to the traditional poling method, the piezoelectric coefficient, free and clamped dielectric constants were improved more than 21%. X-ray diffraction result suggests the existence of monoclinic phase (MA) in ACP samples and piezoresponse force microscopy (PFM) result further depicts the finer engineered domain structures. The ACP sample also showed the unique phase transition sequences during the depoling process. Our work could provide a novel domain engineered method to enhance piezoelectric properties of PMN-PT single crystal. Piezoelectric and dielectric properties of relaxor-PT single crystals can be significantly enhanced by employing the new alternating current poling method, attributing to the unique heterogenous domain structure containing unprecedented domain wall density. [ABSTRACT FROM AUTHOR]

Domain engineering was performed on the [111]c-oriented tetragonal ferroelectric 0.63Pb(Mg1/3Nb2/3)-0.37PbTiO3 (PMN-0.37PT) single crystal in order to achieve better piezoelectric properties. Influences of the poling electric field (EP), poling temperature, and poling time on piezoelectric and electromechanical properties were investigated. The piezoelectric and dielectric constants increase with increasing the EP. In addition, the piezoelectric response increases with increasing the poling time but the crystal saturates after 10 min of poling at 30 °C or 20 min at 150 °C under EP = 2 kV mm−1. The piezoelectric strain coefficient d33 can be improved from 407 pC N−1 poled at 30 °C to 706 pC N−1 after poling at 150 °C near TC, which is 27.9% higher than the highest value reported before (d33 = 551.9 pC N−1). The enhancement of piezoelectric response results from the domain structure redistribution occurring near the ferroelectric to paraelectric phase transition temperature because the potential barrier is substantially lowered so that polarization switching becomes easier. Therefore, more domain walls appear to be beneficial for the enhancement of the piezoelectric response. Under the optimized poling conditions, a complete set of dielectric, elastic, and piezoelectric constants was measured for [111]c-poled PMN-0.37PT single crystal using a combined resonance and ultrasonic method (CRUM). Both the longitudinal (d33 = 706 pC N−1) and shear (d15 = 875 pC N−1) piezoelectric properties are outstanding for the [111]c-poled PMN-0.37PT single crystal due to domain wall motions. [ABSTRACT FROM AUTHOR]

Candle soot nanoparticles (CSNP) and polydimethyl-siloxane (PDMS) composite has shown the highly efficient photoacoustic transduction owing to their high light absorption coefficient and low interfacial thermal resistance. In this study, we report the effect of candle soot structure and thickness on the photoacoustic transduction efficiency. Optical properties of the CSNP/PDMS nanocomposites were characterized through both experimental measurements and finite difference time domain analysis in the visible wavelength range, indicating that the carbon volume fraction and thickness of CS/PDMS composite are highly relevant with light absorption. With a low laser energy input ($< {\text{1 mJ/pulse}}$), the CS/PDMS composite with 2.15 μm thickness exerts an output pressure of 3.78 MPa and a conversion efficiency of ${\text{9.69}}\,\times \,{\text{10}}^{- 3}$ , which is two orders of magnitude higher than previously reported results. [ABSTRACT FROM AUTHOR]

As a novel composite material for laser ultrasound transducer, candle soot nanoparticles polydimethylsiloxane (CSPs-PDMS) has been demonstrated to generate high frequency, broadband, and high-amplitude ultrasound waves. In this study, we investigated the mechanism of the high-optoacoustic conversion efficiency exhibited by the composite. A thermal-acoustic coupling model was proposed for analyzing the performance of the composite. The theoretical result matches well with the experimental observation. The acoustic beam profile was compared with Field II simulation results. The 4.41 × 10−3 energy conversion coefficient and 21 MHz-–6 dB frequency bandwidth of the composite suggest that CSPs-PDMS composites is promising for a broad range of ultrasound therapy and non-destructive testing applications. [ABSTRACT FROM PUBLISHER]

Effect of nano-patterned composite electrode and backswitching poling technique on dielectric and piezoelectric properties of 0.7 Pb(Mg1/3Nb2/3)O3-0.3 PbTiO3 was studied in this paper. Composite electrode consists of Mn nano-patterns with pitch size of 200 nm, and a blanket layer of Ti/Au was fabricated using a nanolithography based lift-off process, heat treatment, and metal film sputtering. Composite electrode and backswitching poling resulted in 27% increase of d33 and 25% increase of dielectric constant, and we believe that this is attributed to regularly defined nano-domains and irreversible rhombohedral to monoclinic phase transition in crystal. The results indicate that nano-patterned composite electrode and backswitching poling has a great potential in domain engineering of relaxor single crystals for advanced devices. [ABSTRACT FROM AUTHOR]