Existing three-dimensional (3D) intravascular ultrasound (IVUS) systems that combine two electromagnetic (EM) motors to drive catheters are bulky and require considerable efforts to eliminate EM interference (EMI). Herein, we propose a new scanning method to realize 3D IVUS imaging using a helical ultrasonic motor to overcome the aforementioned issues. The ultrasonic motor with compact dimensions (7-mm outer diameter and 30-mm longitudinal length), lightweight (20.5 g), and free of EMI exhibits great application potential in mobile imaging devices. In particular, it can simultaneously perform rotary and linear motions, facilitating precise 3D scanning of an imaging catheter. Experimental results show that the signal-to-noise ratio (SNR) of raw images obtained using the ultrasonic motor is 5.3 dB better than that of an EM motor. Moreover, the proposed imaging device exhibits the maximum rotary speed of 12.3 revolutions per second and the positioning accuracy of 2.6 µm at a driving voltage of 240 Vp-p. 3D wire phantom imaging and 3D tube phantom imaging are performed to evaluate the performance of the imaging device. Finally, the in vitro imaging of a porcine coronary artery demonstrates that the layered architecture of the vessel can be precisely identified while significantly increasing the SNR of the raw images.

This work presents a laminated piezoelectric (PZT) motor to achieve high force density, high strength, and compact structure. The oscillator consists of vibration units and a driving foot. Each of the vibration units is formed by symmetrically bonding two PZT ceramics on a carbon fiber-reinforced plastic (CFRP) layer to improve its strength. The oscillator works in hybrid mode of the first longitudinal vibration (L1) and second bending vibration (B2). The finite-element method is adopted to tune the resonance frequencies of the two modes, and the vibration characteristics are experimentally analyzed. The strength test shows that the presence of the CFRP layer can increase the overall strength of the oscillator by 28% compared with a pure PZT motor. To evaluate the performance, the load characteristics of the fabricated prototype (with a size of 39 × 10 × 4.6 mm3 and weight of 10.6 g) are tested on a designed testbed. The single-phase driving method is used to drive the motor, and the best performance is obtained at the B2-mode frequency. The maximum thrust force, no-load speed, and output power reach 17 N, 335 mm s−1, and 775 mW, respectively, at a drive voltage of 100 Vp. Meanwhile, a thrust density of 1604 N kg−1 and an output power density of 73.11 W kg−1 are achieved. The thrust density is much higher than that of the other motors that operate in the same modes.

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The structure and performance of ultrasonic motors have gradually improved with the emergence of new materials, techniques, and structural forms. Therefore, the application scope of this technology is also expanding, especially in the field of high-end equipment. This paper conducts a review of research on the application status and progress at the frontier of research on ultrasonic motors. A summary and classification of both the status of application and cutting-edge research progress are presented, including the use of ultrasonic motors in aerospace, precision, biomedical and optical engineering and the influence on ultrasonic motor design resulting from the breakthrough in advanced processing and preparation technology, structural and functional integration technology, low voltage drives and open-loop control systems. Moreover, the performance of products developed with the aid of ultrasonic motors and representative devices are compared; and state of the art ultrasonic motor designs are discussed and summarized. Finally, potential future research efforts and prospects are highlighted.