HIFU transducer with controllable curvature

A method of controlling the focal length of concave ultrasonic transducers using a flexible surface with arrayed piezoelectric elements is proposed. The surface made of a silicon rubber has a different curvature depending on the air pressure of the inner space of the transducer housing. The acoustic fields of the transducer were measured and compared with the simulated ones. The ultrasonic field from the transducer converged with a different shape with the deflection of the surface. We confirmed the possibility that the focal point of the transducer could be easily controlled by the method.