A tiny ultrasonic motor used in an OCT endoscope

To minimize the micro-motor and simplify its fabrication for the demand in research and application, A cuboidal micro-ultrasonic motor with truncated edge was developed on the basis of a cylindrical micro-ultrasonic motor reported previously. Structure and working principle of the micro-motor and the method of polarization on the piezoelectric plate are introduced in this paper. The frequency of bending vibration mode were simulated by using a finite element analysis. Since the distribution of polarization electric field was not uniform, the influence of polarization voltage on piezoelectricity coefficient was taken into consideration, and the optimal length of truncated edge was calculated. The motor was fabricated and measured. The no-load rotation speed is 2460 rpm and stall torque is about 3.5 mum, when the driving voltage is 65 V_p-p. The cuboidal micro-ultrasonic motors have been utilized in a prototype of optical coherence tomography endoscope. The chicken esophagus and trachea in vitro were examined. The axial resolution is 25 mum and the lateral resolution is 30 mum. This motor has shown good performance, which has potential applied values.