Measuring the Compressibility of Cellulose Nanofiber-Stabilized Microdroplets Using Acoustophoresis

Area of Science:

• Biomaterials Science
• Acoustic Physics
• Drug Delivery Systems

Background:

• Cellulose nanofiber-shelled droplets containing perfluoropentane are promising for ultrasound-mediated drug delivery.
• Understanding droplet mechanical properties, specifically compressibility, is vital for developing effective in vivo ultrasound imaging and optimizing drug release.
• Acoustic manipulation techniques are essential for characterizing these novel drug carriers.

Purpose of the Study:

• To estimate the compressibility of cellulose nanofiber-stabilized droplets using acoustophoresis.
• To determine the bulk modulus of cellulose nanofibers by leveraging droplet compressibility.
• To compare the estimated bulk modulus with experimentally determined values for validation.

Main Methods:

• Acoustophoresis was employed to measure droplet compressibility at varying acoustic pressures.
• Polyamide particles with known properties served as calibration standards.
• The compressibility of droplets was calculated and used to derive the cellulose nanofiber bulk modulus.

Main Results:

• Droplets exhibited a negative acoustic contrast factor, migrating to pressure antinodes under ultrasonic actuation.
• The measured droplet compressibility ranged from 6.6-6.8 ×10^-10 Pa^-1, exceeding that of water but lower than pure perfluoropentane.
• Compressibility remained consistent across different droplet sizes, supporting a size-dependent shell thickness model.

Conclusions:

• The compressibility of cellulose nanofiber-shelled droplets was successfully quantified using acoustophoresis.
• The derived bulk modulus provides critical mechanical data for designing ultrasound-mediated drug delivery systems.
• Findings indicate that droplet compressibility is a key parameter for controlling vaporization and optimizing drug delivery efficiency.