Biaxial driving technique for ultrasound generation with ferroelectric materials

Over the years, ferroelectric materials have been used in a wide variety of applications in the health care field in applications such as thermal therapy, medical imaging and lithotripsy, just to mention some of them. One technical barrier in the transducer industry is that the refocusing or redirection properties of an ultrasound beam depends primarily on the “classical” solution of using a large number of independent transducer elements. High-density ultrasound transducer arrays often imply complexity from the electrical driving circuitry, mechanical constraints caused by the ultrasound probe size, and the need to handle heating of the device; all of which translates into high fabrication costs. Commonly used ultrasound transducers are driven by applying an electric field along the poling axis to maximize their mechanical response. More efficient operation of ultrasound transducers translates into less power consumption to obtain the desired effect and less heating into the system. This work is based on an emerging technique called biaxial driving that offers and enhancement of the mechanical response of an ultrasound transducer by using two phase-offset orthogonal electrical fields on the propagation and lateral directions. In addition to the efficiency enhancement, we hypothesize that the biaxial driving technique produces an added vibration mode due tothe application of the second electric field, which will allow a controlled acoustic pressure redistribution that can be exploited to produce a refocusing or steering of the ultrasound beam with a single element, or an array where fewer elements than conventional transducer arrays are needed. The objective of this research work is to demonstrate with numerical and experimental work that controlled steering of the ultrasound beam can be achieved by the application of a biaxial driving in singleelement ferroelectric transducers. A finite element analysis has been carried out to simulate and calculate the efficiency and the acoustic field response on different ferroelectric materials biaxially driven. [...