76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023;
Washington, DC
Session ZC36: Micro/Nano scale Flows: Multiphase
12:50 PM–2:47 PM,
Tuesday, November 21, 2023
Room: 202B
Chair: Ulf Schiller, University of Delaware
Abstract: ZC36.00001 : Strcutural phase transitions induced by active anisotropic impurities present in 2D colloidal crystals
12:50 PM–1:03 PM
Abstract
Presenter:
Jacob John
(University of Calgary)
Authors:
Jacob John
(University of Calgary)
Giovanniantonio Natale
(University of Calgary)
Active particles, both living and non-living, undergo self-propulsion by consuming chemical energy from their environment. Active motion at complex fluid-fluid interfaces is a ubiquitous phenomenon in nature. Their motion constantly induces active stresses on their environment. Biological active matter such as bacterial cells are capable of adapting to mechanical signals in their changing environment. Hence it is important to understand how active motion affects and gets influenced by its complex environment. 2D colloidal crystals with active particles as impurities can be considered as simplified models to understand the mechanics of complex interfaces in the presence of active particles. In this work, we report the dynamics, rheology and phase behavior of 2D colloidal crystals formed using spherical polystyrene (PS) particles at oil-water interfaces in the presence of active PS-Platinum Janus particles. The particle dynamics is studied using video microscopy and image analysis. The rheological behavior of the interface is investigated using interfacial shear rheology and microrheology. These interfaces exhibit a viscoelastic solid-like behavior in linear regimes and reversible structural rearrangements at large strains. However, with an increase in the number of active particles, the crystal loses its spatial order and forms multiple domains of crystals separated by grain boundaries, even in the absence of activity. In the presence of activity, the overall crystal becomes more dynamic with a heterogeneous spatial distribution of disorder. Particle tracking microrheology and interfacial shear rheology quantify the phase transition to the liquid-like behavior of the interface due to the presence of active impurities. We show how local perturbations can have long-range effects on the dynamics of particles in 2D colloidal crystals and their overall viscoelasticity. The correlations between microstructure and dynamics from our experiments can provide insights into the behavior of a broad range of complex systems such as, motion of particles at oil-water interfaces in Pickering emulsion microreactors and the motion of molecular motors on cell membranes.