High intensity focused ultrasound array transducers for sonochemistry applications

High power ultrasound has been employed to catalyze chemical processes for many years. This is typically based on the ability of the system to produce cavitation, through which high temperatures and pressures are released enabling acceleration of chemical reactions. The ultrasonic system used in sonochemistry is traditionally based on a distributed configuration of single frequency transducers. However, these designs can result in complex reactor design and significant power supply demands. In this work, high intensity focused ultrasound (HIFU) is consider as an alternative transduction solution due to its steering and focusing capabilities. Importantly, the steering ability can manipulate the cavitating field within reactor vessel. Three low frequency, high power array transducers have been fabricated, with operating frequencies of 210 kHz, 290 kHz and 420 kHz and each device comprising 16 array elements. Preliminary characterization of these devices, including electrical impedance and surface displacement measurements, correlates well with the predicted performance through PZFlex. A comparison of the ability of each device to generate a cavitating field, at a number of focal positions, was conducted using a hydrophone and conventional aluminum foil experiments.