In our research group, we previously developed a coiled stator ultrasound motor (CS-USM) for medical applications such as intravascular ultrasound (IVUS) devices. However, wave propagation on acoustic waveguides has not been investigated sufficiently in previous studies. In this study, we analyze the propagation velocity of elastic waves from the simulated the vibration displacement mode profile along a straight line acoustic waveguide via three-dimensional finite element method (FEM). Concerning results, elastic waves with vibration displacement along the thickness direction show dispersion characteristics corresponding to the a0 and a1 mode plate waves (Lamb waves) in the acoustic waveguide. Our theoretical hypotheses of the propagation velocities were closely borne out by experimental results. We further find that the dispersion characteristic is affected by the width of the acoustic waveguide. We believe that our findings can contribute to improved CS-USM designs for practical application.

We previously fabricated a piezoelectric transducer from a lead zirconate titanate (PZT) polycrystalline film deposited on a Ti substrate by a hydrothermal synthesis method. However, the hydrothermal synthesis required a long deposition time to achieve the necessary film thickness. In this study, we confirmed that the thickness of the PZT polycrystalline film increased when the solution was stirred at 245 rpm during synthesis, and that the optimum deposition time was 5 h.

No abstract

For the purpose of performing radial scanning by rotating ultrasound beam in intravascular ultrasound imaging system for diagnosing the state of thrombus and stenosis in a blood vessel such as the coronary arteries of the heart, we are developing micro Coiled Stator UltraSound Motor (CS-USM). Three types of coiled stators with materials of titanium, stainless steel or copper were prepared. These coiled stators were 5 wound acoustic waveguide with 0.5 mm width and 0.1 mm thickness. Size of coiled stator is 0.9 mm diameter and 3 mm length. PZT ceramic vibrator or hydrothermal PZT film vibrator was employed. When two vibrators-type inner rotor CS-USM having stainless steel coiled stator were driven by voltage of 30Vpp at 311 kHz, rotational speed was 3500 rpm, torque was 0.34μNm. Maximum rotational speed of one vibrator-type inner rotor CS-USM having hydrothermal PZT film was 1100 rpm. Maximum rotational speed of one vibrator-type inner rotor CS-USM with titanium or stainless steel coiled stator was 2400 rpm. Rotational speed of the one vibrator-type inner rotor CS-USM with copper coiled stator driven by same conditions was 3200rpm. Maximum rotational speed of two vibrator-type outer rotor CS-USM with stainless steel coiled stator and PZT ceramic vibrators was 1400 rpm.