Chaorui Qiu

Urinary stone disease is a common urological condition with increasing incidence, particularly in developed countries. Laser lithotripsy (LL) has become a preferred minimally invasive treatment due to its high precision and low tissue damage. Recent studies suggest that cavitation plays a critical role in stone damage during LL, and three-dimensional passive cavitation mapping (3D-PCM) has emerged as a promising tool for detecting these events. However, clinical translation of 3D-PCM remains challenging due to limitations in imaging depth, field of view (FOV), and procedural compatibility. Here, we present a large-FOV dual-modality imaging system (3D-PCM and B-mode ultrasound) based on a large-aperture planar ultrasound array. Through array optimization and model-based reconstruction, our system achieves an expanded FOV of ~40*40mm^2 at a clinically relevant imaging depth of ~110mm, while maintaining high spatial resolution of ~0.6 mm laterally and ~0.4 mm axially. In vivo experiments in a porcine model demonstrate that the reconstructed cavitation distribution correlates well with stone damage. Our technology has the potential to provide real-time treatment feedback during LL without disrupting the standard workflow.

To enhance the performance of medical ultrasonic transducers, we optimized the cutting angle of length orientation for the [011]-oriented Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystal (SC) B-mode resonator to maximize the longitudinal vibration (k′33) while suppressing transverse vibration (k31) via anisotropic structural engineering. Experimental results demonstrate that a 60° length orientation along the [100]c direction achieves a peak k′33 value of 77.8%, corroborating theoretical predictions. This orientation of resonator’s length concurrently delivers a low acoustic impedance (Z′33) of 27.6 MRayl, a broad 3 dB bandwidth of 77.1%, and excellent transmit (TP = 3.24 × 10−4 m⋅N−1/2) and receive (RP = 3.77 × 10−11 m⋅N−1/2) efficiencies. The synergy of high electromechanical coupling and reduced clamped dielectric permittivity (ε33S/ε0 < 600) renders this configuration ideal for large-aperture, high-frequency ultrasonic transducers. This work underscores the critical role of crystallographic orientation in tailoring anisotropic electromechanical properties, establishing guidelines of material design for developing high-performance transducers.

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.

A fully-sampled two-dimensional (2D) matrix array ultrasonic transducer is essential for fast and accurate three-dimensional (3D) volumetric ultrasound imaging. However, these arrays, usually consisting of thousands of elements, not only face challenges of poor performance and complex wiring due to high-density elements and small element sizes but also put high requirements for electronic systems. Current commercially available fully-sampled matrix arrays, dividing the aperture into four fixed sub-apertures to reduce system channels through multiplexing are widely used. However, the fixed sub-aperture configuration limits imaging flexibility and the gaps between sub-apertures lead to reduced imaging quality. In this study, we propose a high-performance multiplexed matrix array by the design of 1-3 piezocomposite and gapless sub-aperture configuration, as well as optimized matching layer materials. Furthermore, we introduce a sub-aperture volumetric imaging method based on the designed matrix array, enabling high-quality and flexible 3D ultrasound imaging with a low-cost 256-channel system. The influence of imaging parameters, including the number of sub-apertures and steering angle on imaging quality was investigated by simulation, in vitro, and in vivo imaging experiments. The fabricated matrix array has a center frequency of 3.4 MHz and a -6dB bandwidth above 70%. The proposed sub-aperture volumetric imaging method demonstrated a 10% improvement in spatial resolution, a 19% increase in signal-to-noise ratio, and a 57.7% increase in contrast-to-noise ratio compared with the fixed sub-aperture array imaging method. This study provides a new strategy for high-quality volumetric ultrasound imaging with a low-cost system.

Relaxor-lead titanate (PbTiO₃) crystals, which exhibit extremely high piezoelectricity, are believed to possess high electro-optic (EO) coefficients. However, the optical transparency of relaxor-PbTiO₃crystals is severely reduced as a result of light scattering and reflection by domain walls, limiting electro-optic applications. Through synergistic design of a ferroelectric phase, crystal orientation, and poling technique, we successfully removed all light-scattering domain walls and achieved an extremely high transmittance of 99.6% in antireflection film–coated crystals, with an ultrahigh EO coefficientr₃₃of 900 picometers per volt (pm V⁻¹), >30 times as high as that of conventionally used EO crystals. Using these crystals, we fabricated ultracompact EO Q-switches that require very low driving voltages, with superior performance to that of commercial Q-switches. Development of these materials is important for the portability and low driving voltage of EO devices.

Supplying wireless power is a challenging technical problem of great importance for implantable biomedical devices. Here, we introduce a novel implantable piezoelectric ultrasound energy–harvesting device based on Sm-doped Pb(Mg _1/3 Nb _2/3 )O ₃ -PbTiO ₃ (Sm-PMN-PT) single crystal. The output power density of this device can reach up to 1.1 W/cm ² in vitro, which is 18 times higher than the previous record (60 mW/cm ² ). After being implanted in the rat brain, under 1-MHz ultrasound with a safe intensity of 212 mW/cm ² , the as-developed device can produce an instantaneous effective output power of 280 μW, which can immediately activate the periaqueductal gray brain area. The rat electrophysiological experiments under anesthesia and behavioral experiments demonstrate that our wireless-powered device is well qualified for deep brain stimulation and analgesia applications. These encouraging results provide new insights into the development of implantable devices in the future.

Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound–optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications^{1,2,3,4,5,6,7}. However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d₃₃ (greater than 2,100 picocoulombs per newton), an excellent electromechanical coupling factor k₃₃ (about 94 per cent) and a large electro-optical coefficient γ₃₃ (approximately 220 picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO₃. We find that increasing the domain size leads to a higher d₃₃ value for the [001]-oriented rhombohedral PMN-PT crystals, challenging the conventional wisdom that decreasing the domain size always results in higher piezoelectricity^8,9,10. This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectric domain engineering, and we expect the transparent ferroelectric crystals reported here to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices.

Relaxor-PbTiO₃ crystals possess ultrahigh piezoelectricity when compared with state-of-the-art Pb(Zr,Ti)O₃ ceramics. Recently, even higher piezoelectricity is observed in alternating current electric-field-poled (AC-poled) crystals. This poling technique may benefit many piezoelectric materials and corresponding applications. The scaling effect is quite important for piezoelectric applications, since the operational frequency of devices is associated with the dimension of piezoelectric elements. Here, we investigated the thickness dependence of dielectric and piezoelectric properties for AC-poled relaxor-PbTiO₃ crystals. Compared with the traditional poling method, the piezoelectric coefficient (d₃₃) and dielectric permittivity (ɛ^T₃₃/ɛ₀) were found to be increased by 20%-30% via alternating current electric field poling (AC-poling). A weak scaling effect was observed for the samples with thickness above 200 μm. While, for 100-μm samples, the dielectric permittivity was only enhanced by 6%, and a clear degradation of properties was observed when the cycle of alternating current electric field is beyond three. These features are thought to be associated with the impacts of surface damages for thin samples. Of particular interest is that the coercive field was found to decrease during AC-poling, which should be considered for the design of piezoelectric devices. This work provides important information for AC-poled relaxor-PbTiO₃ crystals and will benefit the piezoelectric applications using these crystals.