Ciliary Pumps*

Motile cilia are microscopic hair-like structures that play important roles in fluid transport and pumping. However, the relationship between the pumping rates and the cilia organization in flow channels is not quantitatively understood.  Here, we develop a computational model aimed at analyzing the transport rate and pumping efficiency of ciliated channels as a function of the cilia organization. Specifically, we use the Brinkman-Stokes equations to model flow through an oscillating porous medium that emulates the ciliary motion. We find a trade-off between the performance of cilia that line the channel walls and that of long cilia that cover the channel. The latter generate weaker flows at zero pressure gradients but outperform short cilia in the presence of adverse pressure gradients. This quantitative framework suggests that different cilia structures and organizations bring distinct advantages to the pumping organs depending on their surrounding and function.