Efficient Driving of Piezoelectric Transducers Using a Biaxial Driving Technique

Abstract

Efficient driving of piezoelectric materials is desirable when operating transducers for biomedical applications such as high intensity focused ultrasound (HIFU) or ultrasound imaging. More efficient operation reduces the electric power required to produce the desired bioeffect or contrast. Our preliminary work [Cole et al. Journal of Physics: Condensed Matter. 2014;26(13):135901.] suggested that driving transducers by applying orthogonal electric fields can significantly reduce the coercivity that opposes ferroelectric switching. We present here the experimental validation of this biaxial driving technique using piezoelectric ceramics typically used in HIFU. A set of narrow-band transducers was fabricated with two sets of electrodes placed in an orthogonal configuration (following the propagation and the lateral mode). The geometry of the ceramic was chosen to have a resonance frequency similar for the propagation and the lateral mode. The average (± s.d.) resonance frequency of the samples was 465.1 (± 1.5) kHz. Experiments were conducted in which each pair of electrodes was driven independently and measurements of effective acoustic power were obtained using the radiation force method. The efficiency (acoustic/electric power) of the biaxial driving method was compared to the results obtained when driving the ceramic using electrodes placed only in the pole direction. Our results indicate that the biaxial method increases efficiency from 50% to 125% relative to the using a single electric field.

An integrated full-bridge Class-DE ultrasound transducer driver for HIFU applications

“…Some of transducers do not have Class-DE switching points, which means that they cannot be driven by Class-DE amplifiers. For instance,a transducer such as the one described in Table 2.3(Tx.3) [15]. 3…”

Biaxial ultrasound driving technique for small animal blood–brain barrier opening

“…The ultrasound waves are generated by the mechanical deformation of the piezoceramic under the effect of the inverse piezoelectric effect. A different ultrasound generation by the piezoceramic can be obtained by applying 'biaxial' driving (Cole et al 2014, Pichardo et al 2015, Delgado et al 2021. This approach involves two sets of electrodes to produce two orthogonal electric fields: the first set attaches to faces perpendicular to the poling axis (P-electrodes), and the second set attaches to faces parallel or lateral to the poling axis (lateral or L-electrodes).…”

“…This ring-type biaxial transducer presents opportunities for addressing steering and efficiency issues with a smaller footprint for a new generation of fully steerable phased arrays. The dimensions of biaxial transducers achieved to date make them particularly suitable as single elements for small animal studies, or for assembly into an array format for clinical applications (Pichardo et al 2015, Delgado et al 2017, 2021.…”