In this article, a PZT/Epoxy 1-3 piezoelectric composite based on picosecond laser etching technology is developed for the fabrication of high-frequency ultrasonic transducer. The design, fabrication, theoretical analysis, and performance of the piezocomposite and transducer are presented and discussed. According to the test results, the area of the PZT pillar is 20.5 μm × 20.5 μm, the average width of the kerf is 4.5 μm, and the thickness of the piezocomposite is 38 μm. The fabricated 1-3 piezocomposite has a resonant frequency of 46.5 MHz, a parallel resonant frequency of 65 MHz, and an electromechanical coupling coefficient of 0.73. According to the wires phantom imaging, its imaging resolution can reach 50 μm. This study shows that the proposed picosecond laser micromachining technique can be applied in the fabrication of high frequency 1-3 piezocomposite and transducer.

The quantitative measurement of acoustic properties is indispensable for many applications. The realization of devices for the evaluation of acoustic properties with higher accuracy and lower error is of great importance. Moreover, the ability to obtain the high-frequency acoustic characteristics of materials is also highly desirable. In this research, the pulse echo method is applied to measure a material’s acoustic parameters, using a miniature transducer with a center frequency of 42.9 MHz. For this method, only one transducer is needed, and the measurement system is simple. Acoustic parameter calculation methods for three types of materials are studied, and the corresponding experiments are conducted. The experimental results show that the sound velocity of water is 1508.8 m s ⁻¹ , and its attenuation coefficient is 0.981 dB mm ⁻¹ ; the results for liquid paraffin give results of 1386.8 m s ⁻¹ and 2.35 dB mm ⁻¹ , respectively. With reference to polymer materials, thermoplastic polyurethane (TPU) thin film has a sound velocity of 1987.2 m s ⁻¹ and an attenuation of 37.1 dB mm ⁻¹ , and polyimide thin film has a sound velocity of 2142.3 m s ⁻¹ and an attenuation of 25 dB mm ⁻¹ . In terms of ceramics, the sound velocity of PZT-5H 3203HD is 4804.2 m s ⁻¹ , and its attenuation is 1.71 dB mm ⁻¹ ; 96% alumina ceramic has a sound velocity of 9924.9 m s ⁻¹ and its attenuation 1.18 dB mm ⁻¹ . All results pertaining to sound velocity agree well with those reported in previous works. The measured attenuation coefficients at high frequency are also in good agreement with the experimental data. All experimental results validate the feasibility, effectiveness, convenience, and accuracy of this method.

High-speed mechanical rotation scanning is the main imaging method of current high-frequency internal ultrasound. Due to uneven drag on the catheter driveshaft leading to changes in the rotational speed, Nonuniform rotational deformity (NURD) is critically limited for the quantitative analysis of internal ultrasound use. To date there have been no techniques shown that provide effective and dynamic modulation of NURD. In this work, a micro structured high-frequency rotary ultrasonic encoder with cylinder gratings was developed, which can dynamically fix the NURD and get high quality restored image. Accordingly, a prototyped micro rotary 50-MHZ ultrasonic encoder with a miniature diameter of 3 mm and a selection of resolutions up to 64 pulses per revolution, which should be the smallest and highest frequency rotary ultrasonic encoder ever reported, was demonstrated based on an endoscopic ultrasound system. The miniature high-frequency rotary ultrasonic encoder shows great potential for ultrasonic endoscopy, OCT, and other mechanical scanning imaging.

Endoscopic ultrasound (EUS) has the ability to image tissue in and beyond the wall of the gastrointestinal (GI) tract, assisting in the early diagnosis of digestive diseases. However, traditional EUS based on flexible endoscopes could make the operation procedure traumatic and intolerable to patients; moreover, certain areas such as most of the small intestine are generally hard to image due to the limited accessibility. To perform endoluminal US imaging in hard-to-reach GI tract, this study proposes a novel magnetically-actuated ultrasound capsule endoscope (MUSCE). Firstly, the MUSCE consisting of a rotatory magnetic-acoustic head and a stable soft tether is designed, featuring small dimensions, low cost, and active locomotion. Next, the magnetic force-modulated torque actuation principle and the corresponding control strategy and US image reconstruction algorithm are analyzed, enabling simultaneous active motion and B-scan ultrasonic imaging. Finally, the effectiveness of the MUSCE is validated by locomotion and imaging tests. Results demonstrate that the designed MUSCE could perform active motion (maximum speed of $\sim$ 13.8 mm/s) and B-scan US imaging (resolution of $\sim$84.2 $\mu$m) in tubular environments with mitigated discomfort, providing a potential solution for clinical applications.

Ultrasound-guided interventional biopsy is becoming an increasingly popular and valuable tool in the clinic. Conventionally, low-frequency (1-5 MHz) ultrasound probes are employed on the patient’s body surface for guiding interventional procedures, leading to low imaging resolution and low puncture accuracy. Several efforts have been made to achieve precise punctures, such as inserting a miniaturized high-frequency phased-array transducer into the patient’s body. However, the interventional devices (introducer biopsy needles) are all separate from those ultrasound probes, which will cause additional damage and operation complexity. Therefore, in this work, a miniature higher frequency phased-array probe integrated with a 0.4 mm intervention working channel is developed, which had 48 array elements and an outer diameter of only 3 mm. The center frequency and -6 dB bandwidth of this probe are measured as 26.2 MHz and 59.6%, respectively. For evaluating its guiding performance, the wire-phantom, ex vivo tissue, and tissue-mimicking phantom experiments were tested. According to the experiments, the axial imaging resolution and lateral resolution can be calculated as 88 and 278 μm at a distance of 2mm far away, respectively, and the effective detecting depth is 12 mm. All these results show that our proposed ultrasound transducer and method can adapt to the works in high-precision interventional guidance.