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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 30: Complex Fluids, Colloids, Micelles and Vesicles I

CPP 30.4: Vortrag

Dienstag, 10. März 2026, 15:00–15:15, ZEU/0260

Microsecond-Resolved Tracking of Ultrasound-Responsive Colloids: From Rigid Silica Probes to Acousto-Responsive Microgels — Parsa Kassaiyan, Regine von Klitzing, and •Amin Rahimzadeh — Technische Universität Darmstadt, Hochschulstrasse 8, 64289 Darmstadt, Germany

Dynamic Light Scattering (DLS) is a powerful tool for characterizing dispersed particles, providing access to their size, size distribution, and dynamical behavior. Here, we integrate high-frequency ultrasound excitation into a conventional DLS setup to resolve the microsecond-scale motion of colloidal particles subjected to intense acoustic fields. This enables simultaneous extraction of particle size and ultrasound-induced oscillation parameters such as vibration frequency, amplitude, and acoustic response, through analysis of the scattered-light intensity correlation function. Compact silica particles serve as robust reference probes: their size remains unaffected by ultrasound, allowing us to map local acoustic energy dissipation by tracking their oscillatory motion at varying distances from the ultrasound source. Building on this reference system, we investigate acousto-responsive PNIPAM microgels. We find that microgels undergo a pronounced ultrasound-induced volume phase transition, shrinking due to rapid dehydration driven by absorption of high-frequency acoustic energy. Our approach thus provides both microsecond-resolved characterization of particle dynamics and a direct pathway to understanding, and exploiting, the acousto-responsiveness of microgels.

Keywords: Dynamic light scattering; Ultrasound; Microgels