Dynamics of Chiral Fluids

Over the last few decades, active matter has been a fast-growing area of research. One of the main reasons is that most biological systems fall into this class of materials - they represent an interacting

collection of microscopic constituents doing mechanical work, typically by converting chemical energy into kinetic energy. Some examples include flocks of birds whose dynamics shows features of

interacting polar active particles, growing and moving cell colonies that can be described as active nematics, as well as crystals formed by starfish embryos that exhibit properties of chiral solids. The

recent creation of novel artificial microspinner systems and independent discoveries in biological organisms has generated great interest in the study of chiral fluids, which break the invariance under

parity and time-reversal that is typically present in equilibrium materials. The out-of-equilibrium nature of such chiral fluids gives rise to a range of unconventional properties, including antisymmetric 'odd' contributions to the viscosity tensor and non-reciprocal responses.

Motivated by these exciting developments, the focus of this project is to investigate the theory of chiral fluids within three interconnected objectives. First, we will develop analytical methods for odd

viscoelastic fluids in two and three dimensions and use them to characterise effects that different boundary conditions have on odd flows. This can then be compared with simulations and experiments

of different systems to investigate what role odd viscoelasticity plays in chiral fluids. Second, motivated by work of experimental collaborators, we will study chiral fluids in microchannels. Specifically, we will

study the impact of confining channel geometries on the dynamics of odd fluids and odd fluid mixtures. Finally, even simple fluids on two dimensional curved surfaces exhibit non-trivially different behaviour to

those on flat surfaces, and such more complex geometries are abundant in biological systems. We will therefore investigate the interplay of curvature and chiral fluid properties using both microscopic models and hydrodynamic equations.

This research aims to provide an improved interdisciplinary understanding of the properties of chiral fluids, as well as their implications for the dynamics of biological cells and the design of novel

experimental chiral fluid systems. Indeed, chiral symmetry breaking is crucial for developing organisms to establish their left-right body axis, a process in which active fluid flows have previously been

implicated. Additionally, developing a deeper mechanistic understanding of chiral fluid flows paves the way for the bio-inspired design of chiral materials in the future. This project falls within the EPSRC Biophysics and Soft Matter research area.