The Best Performing Cilium: E cient or Robust?

Motile cilia are used by many eukaryotic cells to transport ow. Cilia-driven ows 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 ( ow transport) in the context of experimentallyand theoretically-derived cilia models. We particularly examine the optimality and robustness of cilia design. Optimality refers to e ciency of ow transport, while robustness is de ned as low sensitivity to variations in the design parameters. We nd that suboptimal designs can be more robust than optimal ones. That is, designing for the most e cient cilium does not guarantee robustness. These ndings have signi cant implications on the understanding of cilia design in arti cial and biological systems.