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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Poster: Active Matter, Soft Matter, Fluids (joint session DY/CPP)

CPP 25.7: Poster

Mittwoch, 19. März 2025, 10:00–12:00, P3

Reconfiguring hydrodynamic flow fields of active particles by light — Lisa Rohde, Tom-Hannes Hemann, Gordei Anchutkin, and •Frank Cichos — Molecular Nanophotonics Group, Peter Debye Institute for Soft Matter Physics, University Leipzig, Leipzig, Germany

Microscopic active particles propel themselves via localized energy conversion, generating hydrodynamic flow fields that govern their boundary interactions and collective behaviour. The long-range behaviour of the flow patterns classifies them as either pushers, which expel fluid along their swimming axis, or pullers, which draw fluid inward. In nature, some microorganisms can adaptively switch between pusher and puller modes in response to their environment. However, synthetic active particles are currently limited to a fixed pusher or puller configuration during fabrication, constraining our ability to study their dynamic responses to environmental cues. Here, we present a self-thermophoretic active particle that can reconfigure its flow field on demand during the experiment. This is achieved by illuminating the particle with an inhomogeneous light field shaped by a spatial light modulator. The illumination patterns create surface temperature fields inducing thermo-osmotic flow fields that propel the particle and shape the hydrodynamic interactions. By using gold nanoparticles, we trace and characterize the hydrodynamic flow field of the active particle. The ability to dynamically alter the propulsion characteristics will enable us to investigate and control their interactions and collective dynamics.

Keywords: active particles; hydrodynamic flow fields