Experimental investigations of metachronal synchronization in 2D cilia arrays

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Recent experimental evidence is consistent with the hypothesis of orbit flexibility and hydrodynamic coupling as a possible origin of flagellar synchronization. At the same time, synchronization of an isolated cilium pair is not sufficient to guarantee metachronism of an ensemble, highlighting the need to understand better the link between local and global coordination. The observation of metachronal waves (MWs) in the green alga Volvox carteri shows that large scale flagellar coordination is possible even in weakly coupled systems. However, details of the cause-and-effect relationship between defects and consistency of coupling are not well studied under defined conditions. Progress hinges on the identification of suitable experimental systems to study MWs and test the intuition developed from theory under more defined boundary conditions, a goal which remains unfulfilled. Herein, such an experimental system is introduced with an artificial ciliated surface that allows self-organized synchronization in MWs with internal feedback of cilia beat and local flow conditions according the geometric clutch hypothesis of Lindemann, published in 2004. Therefore, the flexible cilia serve simultaneously as flow sensors and actuators. The aim of the project is to study the influence of external flow and surface defects on coordination in chains of such cilia. In addition, the model is used to investigate the resultant transport within such ciliated surfaces using 3D Micro-PIV to address the unknown of nutrient transport influenced by such coordination in nature.