Asymmetric bistability of chiral particle orientation in viscous shear flows

Author(s): Andreas Zöttl, Francesca Tesser, Daiki Matsunaga, Justine Laurent, Olivia du Roure, Anke Lindner
Abstract: The migration of helical particles in viscous shear flows plays a crucial role in chiral particle sorting. Attaching a nonchiral head to a helical particle leads to a rheotactic torque inducing particle reorientation. This phenomenon is responsible for bacterial rheotaxis observed for flagellated bacteria as Escherichia coli in shear flows. Here, we use a high-resolution microprinting technique to fabricate microparticles with controlled and tunable chiral shape consisting of a spherical head and helical tails of various pitch and handedness. By observing the fully time-resolved dynamics of these microparticles in microfluidic channel flow, we gain valuable insights into chirality-induced orientation dynamics. Our experimental model system allows us to examine the effects of particle elongation, chirality, and head heaviness for different flow rates on the orientation dynamics, while minimizing the influence of Brownian noise. Through our model experiments, we demonstrate the existence of asymmetric bistability of the particle orientation perpendicular to the flow direction. We quantitatively explain the particle equilibrium orientations as a function of particle properties, initial conditions and flow rates, as well as the time-dependence of the reorientation dynamics through a theoretical model. The model parameters are determined using boundary element simulations, and excellent agreement with experiments is obtained without any adjustable parameters. Our findings lead to a better understanding of chiral particle transport and bacterial rheotaxis and might allow the development of targeted delivery applications.
Organisation(s): Computational and Soft Matter Physics
External organisation(s): Université de recherche Paris Sciences et Lettres, Université Paris VI - Pierre-et-Marie-Curie, Technische Universität Wien, Osaka University
Journal: Proceedings of the National Academy of Sciences of the United States of America
Volume: 120
No. of pages: 8
ISSN: 0027-8424
DOI: https://doi.org/10.1073/pnas.2310939120
Publication date: 10-2023
Peer reviewed: Yes
Austrian Fields of Science 2012: 103043 Computational physics
Keywords
ASJC Scopus subject areas: General
Portal url: https://ucris.univie.ac.at/portal/en/publications/asymmetric-bistability-of-chiral-particle-orientation-in-viscous-shear-flows(59a73835-02f1-4cc7-bf0d-77d69cba909c).html