Dr James Cass_Computational modelling of morphology-function relationships in ciliated microswimmers

Abstract: Flagellated protists exhibit diverse morphologies and behaviours, from helical swimming to surface-bound filter feeding. Understanding how variations in cell body and flagellar architecture translate into distinct ecological functions requires general, efficient tools for solving the Stokes equations with complex time-dependent boundaries. I will present MicroSwimmers.jl - a fast, composable framework implemented in Julia for simulating three-dimensional microswimmers with complex, time-dependent geometries, based on the boundary-element regularised Stokeslet method. The separation of force and quadrature discretisations prioritises computational efficiency without sacrificing accurate enforcement of boundary conditions. Using simplified morphological models, I will demonstrate how changes in flagellar arrangement, body shape, and proximity to boundaries lead to qualitative changes in swimming trajectories, flow fields, and prey–swimmer interactions. These examples illustrate how morphology acts as a control parameter shaping emergent function, and how low-Reynolds-number hydrodynamics provides a rich testbed for studying complex systems driven by geometry rather than inertia.