Impact of Ultrasound on the Motion of Compact Particles and Acousto-responsive Microgels

TL;DR

This paper combines theoretical modeling and experimental DLS techniques to analyze how ultrasound affects the motion of silica particles and microgels, revealing insights into particle dynamics and potential biomedical applications.

Contribution

It introduces a new model integrating ultrasound effects into DLS analysis and demonstrates its application to microgels and silica particles under ultrasonic vibration.

Findings

Ultrasound does not interfere with silica particle size measurement.

Microgels respond to ultrasound with faster swelling/shrinking kinetics.

The model accurately extracts particle size and vibration parameters from DLS data.

Abstract

In this study, we investigate dynamic light scattering (DLS) from both randomly diffusing silica particles and acousto-responsive microgels in aqueous dispersions under ultrasonic vibration. Employing high-frequency ultrasound (US) with low amplitude ensures that the polymers remain intact without damage. We derive theoretical expressions for the homodyne autocorrelation function, incorporating the US term alongside the diffusion term. Subsequently, we successfully combine US with a conventional DLS system to experimentally characterize compact silica particles and microgels under the influence of US. Our model allows us to extract essential parameters, including particle size, frequency, and amplitude of particle vibration, based on the correlation function of the scattered light intensity. The studies involving non-responsive silica particles demonstrate that US does not disrupt size determination, establishing them as suitable reference systems. Microgels show the same swelling/shrinking behavior as that induced by temperature, but with significantly faster kinetics. The findings of this study have potential applications in various industrial and biomedical fields that benefit from the characterization of macromolecules subjected to US.