  Motile cilia are used by many eukaryotic cells to transport flow.
Cilia-driven flows are important to many physiological functions, yet a deep
understanding of the interplay between the mechanical structure of cilia and
their physiological functions in healthy and diseased conditions remains
elusive. For developing such understanding, one needs a quantitative framework
for assessing cilia performance and robustness when subject to perturbations in
the cilia apparatus. Here, we link cilia design (beating patterns) to function
(flow transport) in the context of experimentally- and theoretically-derived
cilia models. We particularly examine the optimality and robustness of cilia
design. Optimality refers to efficiency of flow transport, while robustness is
defined as low sensitivity to variations in the design parameters. We find that
suboptimal designs can be more robust than optimal ones. That is, designing for
the most efficient cilium does not guarantee robustness. These findings have
significant implications on the understanding of cilia design in artificial and
biological systems.
