Spontaneous Synchronization of Beating Cilia: An Experimental Proof Using Vision-Based Control

Mohamed Elshalakani,Christoph Brücker

doi:10.3390/fluids3020030

Abstract

This article investigates the formation of spontaneous coordination in a row of flexible 2D flaps (artificial cilia) in a chamber filled with a high viscous liquid (Re = 0.12). Each flap is driven individually to oscillate by a rotary motor with the root of the flap attached to its spindle axle. A computer-vision control loop tracks the flap tips online and toggles the axle rotation direction when the tips reach a pre-defined maximum excursion. This is a vision-controlled implementation of the so-called “geometric clutch” hypothesis. When running the control loop with the flaps in an inviscid reference situation (air), they remain in their individual phases for a long term. Then, the flaps are studied in the chamber filled with a highly viscous liquid, and the same control loop is started. The flexible flaps now undergo bending due to hydrodynamic coupling and come, after a maximum of 15 beats, into a synchronous metachronal coordination. The study proves in a macroscopic lab experiment that viscous coupling is sufficient to achieve spontaneous synchronization, even for a symmetric cilia shape and beat pattern.

Highlights

A wide range of biological systems use synchronization in their movement patterns [1,2], ranging from small-scale unicellular organisms to larger scale sperms and microswimmers [3,4]
The results suggested that hydrodynamic interactions are sufficient to achieve spontaneous synchronization
Previous numerical models of the cilia beating patterns have simulated the spontaneous Previous numerical models of the cilia beating patterns have simulated the spontaneous emergence emergence of metachronal waves due to hydrodynamic interactions [18,21]. Included in these of metachronal waves due to hydrodynamic interactions [18,21]. Included in these theoretical models theoretical models is often the geometrical clutch hypothesis, which was introduced by Lindemann is often the geometrical clutch hypothesis, which was introduced by Lindemann [22,23] to explain

Summary

Introduction

A wide range of biological systems use synchronization in their movement patterns [1,2], ranging from small-scale unicellular organisms to larger scale sperms and microswimmers [3,4]. Motile cilia are found in many different tissues, from the brain [5] to the lung and the oviduct, and in many organisms, from Chlamydomonas [6] and Volvox [7,8] algae to Paramecium. It is the beat coordination of the invidiual cilia in the array that plays an essential role in the locomotion of sperm, the cleaning of breathing air, and the movement of oocytes in the fallopian tube [9,10,11,12].

Objectives

Methods

Results

Conclusion