Papers by Author: Yan Hong Chen

Abstract: Most of the ultrasonic surgical or therapeutic devices apply the outside body designs with only the vibration tip contacting and delivering energy to the tissue. For inside body applications, a miniaturized 421 kHz piezoelectric transducer with OD 2 mm and length 10.35 mm based on longitudinal vibration mode was developed in this paper. The transducer is a one-wavelength design with a stepped horn to focus the energy. The theoretical analyses on mechanical, electrical and acoustic properties were performed using finite element analysis (FEA) and equivalent circuit (EC) model, which showed consistent results. The Qm and keff were found to be 393 and 0.21, respectively. The maximum acoustic output power was observed to be 27 mW at 10 V input when the depth of immersion is 1/4 wavelength. Ultrasonic streaming was also observed when the whole transducer was immersed in the water and the input power level was in the order of 0.6 W.

Abstract: A piezoelectric microactuator for minimally invasive surgery procedures was developed using the piezoelectric tube actuator. The tube was fabricated by electrophoretic deposition of a doped PZT powders on the graphite rod substrate and co-sintering. The obtained tube shows maximum strain 0.045% in 31 mode and coercive field 1.5 kV/mm under static condition. Under dynamic condition, bending and longitudinal vibration modes can be identified from impedance spectrum and simulation. Theoretical analysis indicates that the displacement of the two modes depends on the geometry, material property, driving condition and damping conditions. The developed device uses bending mode to create rotation mechanical motion, and longitudinal mode to produce ultrasonic energy to soften and break up the target into fragments.

Abstract: In the present work, the FGM monomorph actuator was developed and applied in the impedance pump. The actuator was fabricated using electrophoretic deposition (EPD). Two starting materials, pure PZT and doped PZT, were mixed to form four different compositions. The actuator was then fabricated by sequential deposition of the four compositions layer by layer on the substrate and followed by sintering to full density. The actuator shows both piezoelectric property and microstructural gradient across the layers. The actuator is able to achieve a bending displacement of nearly 2 mm at resonant frequency. It has been successfully applied to the impedance pump as the actuating component. The pumping action comes from the periodic compression by the actuator to induce a net flow. Maximum flow was observed at the resonant frequency of the actuator. A flow rate of about 9 ml/min was generated.

Abstract: Rotary and linear ultrasonic motors were developed in the present paper using metal-PZT composite piezoelectric stator transducer configuration. The transducer consists of a concentric PZT tube and a metal tube, which structurally improve the reliability of the stator transducer. The developed transducer can provide a free vibration velocity of 0.9 m/s under 100 Vp-p at the resonant state. The rotary motor and linear motor use the developed transducer as the driving component, which produces the rotational motion to drive the motor. The rotary motor is able to achieve about 700 rpm no-load speed, above 2 mNm torque, maximum 70 mW output power and 50% efficiency under driving voltage of 80 Vp-p. The linear motor produces rotational motion and linear motion simultaneously. The linear speed of 5 mm/s can be achieved under the driving voltage of 50 Vp-p under no-load state. Under the loaded state, maximum 8 N load has been observed to be moved by the motor at a speed of 0.6 m/s. The maximum output power and efficiency of the linear motor are 9 mW and 11%, respectively.

Abstract: In the present work, investigation of the functional property of piezoelectric graded monomorph actuator systems is presented. The functional graded actuators were fabricated by electrophoretic deposition (EPD) using pure PZT and doped PZT materials. Actuators developed have shown gradual gradient variation in microstructure. It is noted that trend in microstructural gradient does not represent similar trend in piezoelectric property gradient. The displacement of microstructural graded and both piezoelectric and microstructural graded actuators were measured. The results show that the gradient distribution of the piezoelectric properties is important to improve the electromechanical performance of the actuator.