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Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state–of–art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ult...
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The method of measuring blood flow in photoacoustic microscopy usually relies on ultrasonic transducers in contact fashion, which is not favored in many applications, such as wound areas, burns, and anabrosis. Here we present a noncontact photoacoustic velocity measurement method to quantitatively map transverse blood flow based on the photoacousti...
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... Typically, in this crystalline arrangement, the larger cation is situated at the A site, while the smaller cation occupies the B site. The most commonly employed perovskites are leadbased piezoelectric materials such as lead zirconate (PZT, PbZrO 3 ), lead titanate (PbTiO 3 ) and lead barium lithium niobate (PBLN, Pb(Ba₁/ ₂Nb₂/₃)O₃) due to their high piezoelectric coefficients and excellent electromechanical coupling properties [29][30][31]. Among them, PZT is one of the most widely used lead-based piezoelectric materials, primarily due to its exceptional combination of properties [30,[32][33][34]. ...
... The most commonly employed perovskites are leadbased piezoelectric materials such as lead zirconate (PZT, PbZrO 3 ), lead titanate (PbTiO 3 ) and lead barium lithium niobate (PBLN, Pb(Ba₁/ ₂Nb₂/₃)O₃) due to their high piezoelectric coefficients and excellent electromechanical coupling properties [29][30][31]. Among them, PZT is one of the most widely used lead-based piezoelectric materials, primarily due to its exceptional combination of properties [30,[32][33][34]. However, the presence of lead (Pb) in these piezoelectric materials has harmful implications for both human health and ecosystems [35]. ...
Photocatalysis and piezocatalysis have been extensively employed in energy production and environmental restoration applications. However, the photocatalysis process suffers from rapid recombination of photo-generated electrons (e −) and holes (h +), limiting its practical application. Recently, the piezoelectric effect, which relies on the conversion of mechanical energy to trigger chemical reactions, has shown promise. It can produce an internal piezoelectric field under mechanical vibration, promoting the separation and migration of photogenerated charge carriers. This enhancement leads to significantly improved photocatalytic performance. However, there are still limited reports on other strategies to improve the performance of piezo-photocatalysts. Therefore, a comprehensive review was conducted to categorize the development of piezo-photocatalysts, detailing their classifications, synthetic methods and construction strategies, as well as their applications in energy production and wastewater treatment. This review aims to address the present challenges and future prospects of piezo-photocatalysis, providing clarity on its developmental trajectory.
... Sensing technology is widely used in environmental monitoring, healthcare, safety monitoring, intelligent transportation, agricultural production, and other fields. Compared to other sensors [1][2][3][4][5], optical fiber sensors (FOSs) [6][7][8][9] based on optical fiber sensing technology have attracted more and more attention due to their unique anti-electromagnetic interference, compactness, high sensitivity, and corrosion resistance. Optical fiber sensors can be used to monitor various physical variables in the external environment, including temperature [10], strain [11,12], refractive index (RI) [13][14][15][16], magnetic field [17], humidity [18,19], curvature [20][21][22], pH [23], displacement [24,25], shape [26][27][28][29], and so on [30]. ...
In this paper, a high-linear-sensitivity fiber curvature sensor based on the sphere-shaped misaligned structure (SSMS) with few-mode fiber (FMF) and single-mode fiber (SMF) was proposed and demonstrated. A spherical structure was prepared at one end of a few-mode fiber, which could effectively excite higher-order modes and generate interference in the misaligned cascade. When external environmental parameters changed, the resonance peaks formed by intermodal interference were displaced, and the shifts generated by different resonant peaks were also different. The experimental results show that the maximum curvature sensitivity was −2.220 nm/m−1, and the linear fitting coefficient reached up to 0.991, which is an extremely high sensitivity among wavelength-modulated curvature sensors. Meanwhile, the strain sensitivity of the sensor was as low as 7.99 pm/με¯, and the temperature sensitivity was 3.958 pm/°C, which is a low temperature sensitivity and low strain sensitivity, and solves the cross-sensitivity problem. With advantages of simple manufacture, low cost, and favorable stability, the sensor is expected to be one of the best candidate instruments for measuring curvature and inclination.
... Piezoelectric materials which convert mechanical energy into electrical energy and vice versa have been widely employed for actuators and transducers in a plenty of applications for electroacoustic sensors, diagnostic imaging, nondestructive evaluations and therapeutic treatments owing to their electromechanical coupling [1][2][3][4][5]. Especially, relaxor-PbTiO 3 (PT) piezoelectric single crystals, represented by Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT) and Pb(In 1/2 Nb 1/2 ) O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PIN-PMN-PT), have been at the forefront of leading advancements in state-of-the art electromechanical devices due to their superior electromechanical responses (piezoelectric coefficient, d 33 > 1,500 pC/N) and coupling factor (k 33 > 0.9) to polycrystalline counterparts, e.g., Pb(Zr,Ti)O 3 (PZT) ceramics [6,7]. ...
We investigated mechanical stress-dependent behaviors of (011)-oriented Mn-doped PIN–PMN–PT single crystals to further improve their stabilities for high-power piezoelectric applications. In contrast to the common belief that mechanical constraint induces depolarization of active piezoelectric materials, the (011)-oriented single crystals demonstrated up to 44% of enhancements in their coercive field when mechanical stress is loaded on the specific flank surfaces of the single crystals. Furthermore, the suggested strategy is also feasible over practical operational temperatures for electroacoustic sensors (5–60 °C), which is beneficial to high-temperature applications. Nevertheless, consistent with the generally accepted trade-off, their electromechanical responses are inevitably degraded at constrained states due to less shear deformation which is key in piezoelectricity of relaxor-PT single crystals. We hope that the current work will elucidate mechanical stress-dependent behaviors of domain-engineered anisotropic relaxor-PT single crystals and provide a clue for a proper selection of prestress levels to achieve better performances of electroacoustic transducers in a variety of environments.
... For example, the silver-loaded epoxy is commonly used as an inner matching layer for high-frequency piezoelectric-crystal/ceramics-based transducers due to its moderate acoustic impedance (5)(6)(7) and commendable electrical conductivity (< 1 Ω mm −1 ). However, its opacity prevents its application in the fabrication of TUTs [43][44][45] . Although extensive efforts have been made to develop various transparent matching layers for TUTs, there's still a gap between TUTs and conventional highfrequency transducers. ...
... The advantages of using PIN-PMN-PT for TUTs Figure 1a shows the basic structure and working principle of a TUT used for PAI. The TUT mainly includes a transparent piezoelectric material, electrodes, matching layers, and backing layers, in which the piezoelectric material is essential for achieving high detection sensitivity 43,51 . Generally, the acoustic impedance of piezoelectric materials (e.g., piezoelectric ceramics,~35 MRayl) mismatches that of biological tissues (~1.5 MRayl). ...
... Thus, the matching layers are required in the design of transducers to achieve high acoustic energy transmission efficiency. The backing layer is applied at the back of the piezoelectric material to damp out the ringing effect and provide reliable mechanical support 43 . For this design, the laser beam can be illuminated on the biological tissues directly through the transparent sensing elements. ...
Photoacoustic imaging is a promising non-invasive functional imaging modality for fundamental research and clinical diagnosis. However, achieving capillary-level resolution, wide field-of-view, and high frame rates remains challenging. To address this, we propose a transparent ultrasonic transducer design using our developed transparent Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 crystals. Our fabrication technique incorporates quartz-glass-and-epoxy matching layers with low-resistance indium-tin-oxide electrodes through a brass-ring based structure, enabling a high frequency (28.5 MHz), wide bandwidth (78%), and enhanced pulse-echo sensitivity (2.5 V under 2-μJ pulse excitation). Our Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3-based transparent ultrasonic transducer demonstrates a four-fold enhancement in photoacoustic detection sensitivity when compared to the LiNbO3-based counterpart, leading to a 13 dB improvement of signal-to-noise ratio in microvascular photoacoustic imaging. This enables dynamic monitoring of mouse cerebral cortex microvasculature during seizures at 0.8 Hz frame rates over a 1.5 × 1.5 mm² field-of-view. Our work paves the way for high-performance and compact photoacoustic imaging systems using advanced piezoelectric materials.
... 9,10 At a given operational frequency, the axial resolution of IVUS transducers can be improved by increasing their bandwidth, 11 while lateral resolution can be improved by employing acoustic focusing as well as increasing the transducer aperture size. [12][13][14][15][16] However, for practical considerations, the aperture size of IVUS transducer must remain below 0.8 mm to fit into an intravascular catheter. 8 Therefore, the geometries (i.e., aperture size and focal depth) of IVUS transducers require careful design to balance the tradeoffs between lateral resolution and depth of field for optimal imaging performance. ...
... Currently, relaxor-PbTiO 3 (PT) single crystals, such as Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT) and Pb(Zn 1/3 Nb 2/3 )O 3 -PbTiO 3 (PZN-PT), have been extensively utilized in commercial IVUS transducers due to their excellent piezoelectric and electromechanical properties. [12][13][14][15]17,18 However, the low phase transition temperature ($100 C) of relaxor-PT crystals inevitably leads to depolarization during the press-focusing process, because their phase and domain structures become extremely unstable under simultaneous high-temperature and high-pressure conditions, particularly for crystals with compositions near the morphotropic phase boundary. 19,20 Moreover, repolarizing such a thin (<100 lm) crystal plate after the fabrication can degrade transducer performance due to the thickness scaling effect in relaxor-PT crystals. ...
... At an aperture size of 0.3 mm, the acoustic field shows no significant change with and without focusing, as the geometric focal depth exceeds the natural focal depth ($0.58 mm). 12 When the aperture size is increased to 0.6 mm, the focusing effect becomes prominent, leading to a significant enhancement in acoustic field intensity at a depth of 1.4 mm. Figure 1(f) shows that the 0.6-mm focused transducer exhibits a smaller À6 dB beam width at the acoustic focus compared to the planar counterpart. Figure 1(g) demonstrates the À6 dB beam width with respect to depth for transducers with different geometries. ...
Intravascular ultrasound (IVUS) imaging is a minimally invasive medical technology that plays a critical role in diagnosis, treatment guidance, and post-treatment assessment of coronary artery diseases. As a crucial component of the IVUS system, conventional IVUS transducers are designed to be planar and unfocused to adequately cover the region of interest. However, this design comes at the cost of spatial resolution. Here, we developed a high-performance focused IVUS transducer using Pb(In1/2Nb1/2)O3-Pb(Sc1/2Nb1/2)O3-PbTiO3 (PIN-PSN-PT) textured ceramics with both high electromechanical performance (thickness-mode electromechanical coupling factor kt: ∼60%) and high Curie temperature (TC: ∼250 °C). Benefiting from the relatively low clamped dielectric constant ( ε33S/ε0: ∼450) of PIN-PSN-PT-textured ceramics in contrast to currently used soft piezoelectric ceramics (>1000), we designed a relatively large aperture for the focused IVUS transducer, with a goal of enhancing lateral resolution across a larger depth of field, ranging from 1 to 5 mm. The developed focused IVUS transducer operates at 42 MHz with an −6 dB bandwidth of 72%, featuring a 0.6 × 0.6 mm² aperture while maintaining an electrical impedance of approximately 40–60 Ω. The axial and lateral resolutions characterized by wire phantom imaging are 45 and 208 μm, respectively. The acoustic pressure generated by the focused IVUS transducer is 1.4 times higher than that of its planar counterpart. Ex vivo porcine coronary artery imaging demonstrates that our focused IVUS transducer offers improved image quality and uniformity for the visualization of intravascular structures. Our work shows great potential of PIN-PSN-PT-textured ceramics for creating high-frequency miniaturized focused transducers.
... 0.5NN ceramic as competitive candidates for electromechanical devices, particularly in ultrasonic transducer applications where high electromechanical performance and low acoustic impedance contribute to expanded bandwidth and enhanced sensitivity. [34][35][36][37] Randomly oriented ceramics exhibit large-sized strip domain structures in Fig. 3(a), whereas the T-KNN-0.5NN textured ceramic not only features dense strip domains of approximately 5-40 nm but also displays high-density domain configurations adjacent to longrange ordered domain structures in Figs. ...
The progress of next-generation electromechanical devices is substantially reliant upon achieving high electromechanical coupling performance in piezoelectric materials. Here, a local stress regulation strategy is introduced to significantly enhance the overall electromechanical response of lead-free piezoceramics. A remarkable large piezoelectric coefficient (d33) of ∼800 pC N⁻¹ and longitudinal electromechanical coupling factor (k33) of 88% are obtained in (K,Na)NbO3 (KNN)-based textured piezoceramics. From both experimental examinations and theoretical simulation, including phase-field analyses, it is found that the improved piezoelectric performance primarily stems from the stress-induced elastic field aligned with the preferred crystallographic orientation, which constrains the domain size, resulting in nanoscale short-range ordered domain structures. Such structures facilitate the flexible rotation of electric dipoles within coexisting phases due to flattened free energy distribution, thereby leading to the exceptionally large piezoelectric response. This understanding provides valuable guidance for the design of novel lead-free piezoceramics with excellent piezoelectric performance.
... Organic piezoelectric polymers are ideal for many applications because they are naturally lightweight, flexible, resilient, and easy to construct into any shape. This sets them apart from inorganic piezoelectric materials [56]. ...
As science and technology grow at a rapid pace and human civilization progresses, portable microelectronic gadgets are becoming more and more commonplace. The energy sources of these devices have become a popular research. The most common and most available form of energy in the environment is mechanical energy derived from vibrations. The available energy density for random vibrations with frequencies ranging from hundreds of hertz to kHz is a few hundred microwatts to milliwatts per cubic centimeter. Therefore, how to capture this energy for battery charging, power supply for electronic devices, and remote/wireless sensing has become an important and novel research direction. Using nanoscale mechanical energy harvesting to power small circuits and create self-powered electronic devices has enormous potential, of which piezoelectric nanogenerators (PENGs) are widely studied. Piezoelectric nanogenerators, which use nanometer-scale piezoelectric materials to transforming arbitrary mechanical energy into electrical energy, are a rapidly emerging product category. They can produce sustained electrical energy and are more environmentally benign than chemical batteries. The concept and evolution of piezoelectric materials are first presented in this paper. Next, the structure and operation of a piezoelectric nanogenerator are explained. Lastly, the development trend of converting mechanical energy produced by drum vibration into electrical energy is combined.
... Different piezoelectric materials [21] became a standard in medical ultrasound since the first reported usage of piezoelectric effect in quartz crystal transducer acting as a head scanner [22]. The number of peculiarities is inherent in this technology, including impedance matching [23] and the constant pursuit for a wide operating frequency range [24], [25]. The former results in power losses during acoustic energy transfer, because significant amounts of energy are reflecting into transducer, whereas the latter is crucial for axial or lateral resolution and, as a result, in more detailed structural description of lesions or anatomical peculiarities of human organs [26]. ...
Starting from an overview of historical aspects of biomedical ultrasound development and its application areas, as well as the brief description of state-of-the art microfabrication technologies, used for capacitive and piezoelectrical micromachined ultrasonic transducers manufacturing, also outlining their modelling approaches, the reader will be further presented with an overview of existing methods for achieving broadband operation both at unit transducer and transducers array levels. Moreover, a generalized signal processing system is discussed, including description of known approaches for building blocks implementation in analog, digital and mixed-signal domains (such as drivers, amplifiers, ADCs, etc.).
... Lead zirconate titanate (PZT) is widely used in the fields of microelectronics, sensors, actuators, transducers, harvesting devices, and semiconductors due to its outstanding piezoelectric and ferroelectric properties. [1][2][3][4][5] Rare-earth-doped modified PZT materials have attracted considerable research interest in recent years. [6][7][8][9][10][11] Rare-earth ions, with their unique ionic radius and different chemical valence states, can replace the original ions and create vacancies, leading to lattice distortion and, consequently, affecting the performance of PZT films. ...
In this study, Pb(Zr0.54Ti0.46)O3 films were prepared by the sol-gel method with Sm doping concentrations of 0, 0.5, 1, 1.5, 2, and 3 mol. %. Their surface morphology, density, crystal structure, piezoelectric, dielectric, and ferroelectric properties were characterized. The results indicated that, unlike Sm-doped lead zirconate titanate (PZT) ceramics, all Sm-PZT films exhibit a significant increase in the grain size compared to undoped PZT films. Moreover, Sm doping affected their crystal orientation and significantly enhanced their piezoelectric coefficient d33 and remnant polarization (Pr). Notably, the Sm-PZT film with a doping concentration of 1.5 mol. % exhibited optimal (100) orientation, achieving a high piezoelectric coefficient d33 of 279.87 pm/V, 4.55 times that of the non-doped PZT films.
... Piezoelectric materials are widely used in ultrasonic transducers for medical diagnostic and wearable health monitoring, such as abdominal, endoscopy, ophthalmology, breast scans, and so on. [1][2][3][4] Moreover, 1-3 piezoelectric composites possess relatively high thickness electromechanical coupling factor (k t ) and customizable acoustic impedance (Z), which are conducive for improving the bandwidth, resolution, and signal-to-noise ratio of transducers, in comparison with piezoelectric single crystals and ceramics. 5-7 Among 1-3 piezoelectric composites, Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PIN-PMN-PT) single crystal-based 1-3 piezoelectric composites have outstanding piezoelectric properties, large thickness electromechanical coupling factor (k t ), and large coercive field (E c ), which are beneficial in terms of improving the sensitivity, bandwidth, source level, and reliability of transducers. ...
Alternating current polarization (ACP) has been demonstrated to enhance the performance of 1-3 piezoelectric single crystal composites (PSCCs), compared to direct current polarization (DCP). However, the scaling effect and temperature stability of PSCCs under different polarization modes, which are of significance to practical applications, have rarely been studied. Here, we compared and analyzed the thickness and temperature-dependent properties of PSCCs under ACP and DCP. The results indicated that ACP PSCCs have improved piezoelectric, electromechanical coupling, and dielectric properties. There were scaling effects for PSCCs with thickness below 400 μm. Compared to high-thickness PSCCs, the piezoelectric coefficient (d33), free dielectric constant ( ε 33 T ε 0) as well as thickness electromechanical coupling factor (kt) of low-thickness samples were inferior and the corresponding performance enhancements under ACP were also relatively low. In contrast, the clamped dielectric constant ( ε 33 S ε 0) did not show significant thickness correlation. As for temperature stability, all performances of PSCCs improved with increase in temperature and the performance enhancement with temperature change was not dependent on the polarization conditions. This work provides reference significance of selecting appropriate polarization for PSCCs, thus benefiting the design and preparation for transducers.