Measuring the Compressibility of Cellulose Nanofiber-Stabilized Microdroplets Using Acoustophoresis

Droplets with a liquid perfluoropentane core and a cellulose nanofiber shell have the potential to be used as drug carriers in ultrasound-mediated drug delivery. However, it is necessary to understand their mechanical properties to develop ultrasound imaging sequences that enable in vivo imaging of the vaporization process to ensure optimized drug delivery. In this work, the compressibility of droplets stabilized with cellulose nanofibers was estimated using acoustophoresis at three different acoustic pressures. Polyamide particles of known size and material properties were used for calibration. The droplet compressibility was then used to estimate the cellulose nanofiber bulk modulus and compare it to experimentally determined values. The results showed that the acoustic contrast factor for these droplets was negative, as the droplets relocated to pressure antinodes during ultrasonic actuation. The droplet compressibility was 6.6-6.8 x10(-10) Pa-1, which is higher than for water (4.4x10(-10) Pa-1) but lower than for pure perfluoropentane (2.7x10(-9) Pa-1). The compressibility was constant across different droplet diameters, which was consistent with the idea that the shell thickness depends on the droplet size, rather than being constant.

Automated summary

In this study, the compressibility of droplets stabilized with cellulose nanofibers was estimated using acoustophoresis, showing a constant value across different droplet diameters. The results revealed a negative acoustic contrast factor for the droplets, indicating their relocation to pressure antinodes during ultrasonic actuation. The compressibility of the droplets was found to be higher than that of water but lower than that of pure perfluoropentane.