Chiral cilia carpets on curved surfaces

Swimming behaviour of organisms in low Reynold's number fluid environments facilitated by cilia has been widely studied in biological physics. Motile cilia are structurally chiral slender protein appendages whose geometric and dynamical characteristics allow them to facilitate cell motility and fluid transport. Systems of many cilia can organise and respond to external stimuli to provide important functions for microorganisms, including directed motion and taxis. Interestingly, this ciliar coordination is not necessarily actively regulated by the organism at the level of the individual cilia, but can instead be described as an emergent phenomenon arising from the hydrodynamic interactions between the cilia. An example of such emergent coordination in cilia carpets was recently studied by F. Meng, R. Bennett, N. Uchida, and R. Golestanian ("Conditions for metachronal coordination in arrays of model cilia", PNAS, 2021). There, it was shown that self-organised beating of cilia arrayed on a flat surface can be understood from the hydrodynamic interactions between them. My research aims to investigate the role of cilia carpets for microswimmer motility by considering their self-organisation on a curved surface that is immersed and moving through the surrounding fluid. Specifically, in this configuration, I want to identify self-organisation and synchronisation mechanisms of ciliary beating, and how the resulting coordination can facilitate controlled swimming. This research is relevant to the study of the motility of ciliates - a large class of marine microorganisms that are characterised by the presence of many cilia on their body surface. These include starfish (Patiria miniata), whose chiral swimming dynamics facilitate the formation of hydrodynamically stablised active crystals recently studied by T. H, Tan, A. Mietke, et al. ("Odd dynamics of living chiral crystals", Nature, 2022). This work will provide a theoretical framework to investigate the dynamical properties of these embryos that underpin chiral swimming and active crystal formation. Collaboration with biophysics experimentalists and measurement of the motion of ciliate cells would allow predictions of the theory to be tested. This project falls within the EPSRC Biophysics and Soft Matter Physics research area and will be conducted under the supervision of Dr Alexander Mietke.