Piezoelectric ceramics are currently of considerable interest for their capabilities of converting compressive/tensile stresses to an electric charge, or vice versa. Because ceramics cannot be cast and machined easily, additive manufacturing (AM) processes (3D printing technology) open an effective pathway in geometrical flexibility. However, the piezoelectric properties limit the application of printed ceramics. This work demonstrates that a piezoelectric-composite slurry with BaTiO 3 nanoparticles (100nm) can be 3D printed using Mask-Image-Projection-based Stereolithography (MIP-SL) technology. After a post-process, the density of 5.64g/cm 3 was obtained, which corresponds to 93.7% of the density of bulk BaTiO 3 (6.02 g/cm 3 ). The printed 1 Zeyu Chen and Xuan Song contribute equally to this paper 2 ceramic exhibits a piezoelectric constant and relative permittivity of 160 pCN -1 and 1350respectively. An ultrasonic transducer with printing focused piezoelectric element was fabricated to realize the energy focusing and ultrasonic sensing. A 6.28MHz ultrasonic scan was achieved by the transducer and successfully visualized the structure of a porcine eyeball.

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Characterizing the viscoelastic properties of thin-layer tissues with micro-level thickness has long remained challenging. Recently, several micro-elastography techniques have been developed to improve the spatial resolution. However, most of these techniques have not considered the medium boundary conditions when evaluating the viscoelastic properties of thin-layer tissues such as arteries and corneas; this might lead to estimation bias or errors. This paper aims to integrate the Lamb wave model with our previously developed ultrasonic micro-elastography imaging system for obtaining accurate viscoelastic properties in thin-layer tissues. A 4.5-MHz ring transducer was used to generate an acoustic radiation force for inducing tissue displacements to produce guided wave, and the wave propagation was detected using a confocally aligned 40-MHz needle transducer. The phase velocity and attenuation were obtained from k-space by both the impulse and the harmonic methods. The measured phase velocity was fit using the Lamb wave model with the Kelvin-Voigt model. Phantom experiments were conducted using 7% and 12% gelatin and 1.5% agar phantoms with different thicknesses (2, 3, and 4 mm). Biological experiments were performed on porcine cornea and rabbit carotid artery ex vivo. Thin-layer phantoms with different thicknesses were confirmed to have the same elasticity; this was consistent with the estimates of bulk phantoms from mechanical tests and the shear wave rheological model. The trend of the measured attenuations was also confirmed with the viscosity results obtained using the Lamb wave model. Through the impulse and harmonic methods, the shear viscoelasticity values were estimated to be 8.2 kPa for $0.9~\text {Pa}{\cdot} \text {s}$ and 9.6 kPa for $0.8~\text {Pa}{\cdot} \text {s}$ in the cornea and 27.9 kPa for $0.1~\text {Pa}\cdot \text {s}$ and 26.5 kPa for $0.1~\text {Pa}\cdot \text {s}$ in the artery.

In clinical decision making, in addition to anatomical information, biomechanical properties of soft tissues may provide additional clues for disease diagnosis. Given the fact that most of diseases are originated from micron sized structures, an elastography imaging system of fine resolution (~100 µm) and deep penetration depth capable of providing both qualitative and quantitative measurements of biomechanical properties is desired. Here, we report a newly developed multi-functional ultrasonic micro-elastography imaging system in which acoustic radiation force impulse imaging (ARFI) and shear wave elasticity imaging (SWEI) are implemented. To accomplish this, the 4.5 MHz/40 MHz transducer were used as the excitation/detection source, respectively. The imaging system was tested with tissue-mimicking phantoms and an ex vivo chicken liver through 2D/3D imaging. The measured lateral/axial elastography resolution and field of view are 223.7 ± 20.1/109.8 ± 6.9 µm and 1.5 mm for ARFI, 543.6 ± 39.3/117.6 ± 8.7 µm and 2 mm for SWEI, respectively. These results demonstrate that the promising capability of this high resolution elastography imaging system for characterizing tissue biomechanical properties at microscale level and its translational potential into clinical practice.