Progress, Challenges, and Prospects of Miniature Ultrasonic Motors

Miniature ultrasonic motors (MUSMs), as a class of piezoelectric actuators based on advanced materials, have attracted considerable interest due to their millisecond-scale response time, milli-Newton output force, high-speed operation, and sub-micrometer-level resolution. These characteristics make MUSMs suitable for emerging applications, such as motion platforms, miniature robotics, portable cameras, and biomedical devices. This work provides a detailed overview of MUSMs, including their configurations, operational principles, design strategies, and functionalities. The performance of various MUSMs, including beam-type, plate-type, disk-type, tube-type, rod-type, spherical/hemispherical, and spiral-type stators, is analyzed and compared. Their distinct advantages and limitations are highlighted. Key challenges faced by MUSMs in practical applications, covering technical, material, and design aspects, are identified and discussed. Finally, potential avenues for the advancement of MUSMs are proposed, including the development of novel piezoelectric materials, innovative structural designs, and new applications in fields such as aerospace applications, wearable devices, and advanced imaging systems. This review aims to provide a comprehensive understanding of the advancements in MUSMs and to highlight the need for further research, thereby contributing to the progress in potential application areas.