Acoustic droplet vaporization with microfluidic droplets results in dissolved oxygen scavenging

Abstract

Acoustic droplet vaporization (ADV) is the ultrasound-mediated phase transitioning of liquid perfluoropentane (PFP) droplets into gas microbubbles resulting in dissolved oxygen scavenging from the surrounding fluid. The objective of this study was to determine how droplet diameter influences oxygen scavenging. Droplets of 12 μm and 6 μm diameters were manufactured using a microfluidic system, which were diluted in saline to obtain concentrations of 0.48 Χ 10-3 ± 0.12 Χ 10-3 ml/ml and 1.11 Χ 10-3 ± 0.13 Χ 10-3ml/ml, respectively. Samples were pumped through a 37 °C flow phantom at 10 ml/min. A 5 MHz transducer insonified droplets at 5 MPa for 20 cycles with a 500 Hz repetition frequency. Oxygen partial pressure (Po2) was measured with a distal sensor. Samples of 12 μm and 6 μm droplets had an average volume-weighted transition efficiency of 5.8% ± 4.5% and 5.3% ± 4.6%, respectively. The initial Po2 was 169 ± 7 mmHg for all samples. ADV with 12 μm and 6 μm droplets reduced the Po2 to 113 ± 21 mmHg and 101 ± 9 mmHg, respectively. An oxygen scavenging model based on the PFP phase transitioned volume yielded a final Po2 of 121 ± 27 mmHg for 12 μm droplets and 106 ± 29 mmHg for 6 μm droplets. There was no statistically significant difference (p > 0.05) between the experimentally measured and modeled Po2 values after ADV.