Fig. 1.

(A) Scheme of the experimental setup comprised an irradiation chamber, a circular unfocused ultrasound transducer, and an adaptor filled with degassed water, connecting the irradiation chamber and the transducer. The adaptor length is designed to locate the sample in the far-field region providing stable pressure values. (B) Axial pressure as a function of distance from the transducer; the far-field was determined to start at a distance of ~140 mm. (C) Contour plot of the radial pressure distribution at the far field region (43.3 kPa per contour). The sample area is confined to 0.8 cm² at the center of the beam where an approximately homogeneous field is measured. Measurements of acoustic pressure are performed using an HNR-0500 needle hydrophone (Onda Corp., Sunnyvale, CA).