Fig. 3.

(a-c) Acoustic droplet vaporization (ADV) threshold of phase-shift nanoemulsions (PSNE) as a function of the focused ultrasound (FUS) peak negative pressure at 1 MHz (a), 2.5 MHz (b), and 5 MHz (c). Using the experimental set-up in Figure 1a, a PSNE suspension (10⁹ PSNE/mL) was interrogated with pulsed FUS (5 cycles, 4–8 MPa peak negative pressure and 100-Hz pulse repetition frequency), and acoustic cavitation emissions were simultaneously recorded with a broadband passive cavitation detector. PFP and PFH PSNEs were interrogated along with water (no PSNE) as a control. Results are depicted as the percentage of signals containing an acoustic cavitation event versus the peak negative pressure of the focused ultrasound. A total of 100 individual time traces were captured at each pressure step for post-processing. The ADV threshold was defined as the peak negative pressure that resulted in 10% of the signals containing acoustic cavitation events and was 5.6, 5.9 and 4.6 MPa at 1, 2.5 and 5 MHz, respectively. PFH = perfluorohexane; PFP = perfluropentane; PSNEs = phase-shift nanoemulsions.