WAVES IN MOTILE CILIA

Motile cilia are active filaments present on the surface of various human organs (e.g. the lung and brain epithelia), where they perform crucial functions by driving surface flows. Structurally, they are conserved across the eukaryotes. Cilia can affect each other, for example leading to phase locking of their beating, by the forces they exert on each other through the fluid and in some cases through the cell cytoskeleton. Some beautiful physics has been developed by various teams in the last decade to understand how the details of beating on each cilium can lead to specific phase locking, and to the emergence of collective waves. In recent work we have explored the role of external flows, both oscillatory and constant, and their role in development. Analogies can be drawn between these flows and the effect of external magnetic fields in magnetic systems. We present both experimental results, and numerical explorations of a simple class of ”rower” models of motile cilia.