Piezoelectric transducer design for an ultrasonic scalpel with enhanced dexterity for minimally invasive surgical robots

Ultrasonic scalpel offers the advantages of reliable and simultaneous vessel cutting and sealing and provide self-cleaning capacity with less thermal damage and smoke. However, the current long, straight, and rigid ultrasonic scalpels have limited degrees of freedom, which restricts the operation dexterity of the minimally invasive surgical robot. To address such problem, a novel design of a minimized piezoelectric transducer that can be integrated at the distal end of a multi-degrees of freedom robotic instrument, has been proposed and implemented in the work. This concept can take full advantage of ultrasonic scalpels while guaranteeing the dexterity of the sufficient robotic operation. By employing the electromechanical equivalent method, the initial dimensional parameters of the ultrasonic transducers have been calculated. The optimal transducer design has been achieved by utilizing the proposed optimization method, which is based on finite element method, design of experiment, response surface method, and multi-objective genetic algorithm. The transducer prototype was manufactured, and its dynamic characteristics were further investigated by using impedance analyzer. The results reveal that the actual features of the transducer closely match the finite element method-based simulation results. In-vitro experiments have been performed to show that the vibration amplitude and frequency can meet the requirements for dissection and coagulation of tissues.