Hydrodynamic synchronization of colloidal oscillators used as a model of cilia and flagella

Orateur : Nicolas BRUOT (Institut Lumière Matière, Lyon, France)

Synchronization of driven oscillators is a key aspect of flow generation in artificial and biological systems at the micro scale. Flow can be driven efficiently by filaments undergoing periodic motion. These filaments are typically colloidal-scale and semi-flexible. They have therefore many degrees of freedom and are subject to thermal noise. The question of synchronization can however be addressed by simpler systems, such as individual driven spheres, in which the multiple degrees of freedom of the complex systems are coarse-grained into a few control parameters which can be tuned and understood theoretically, also making it easier to account for the hydrodynamic interaction. I will show results on two model oscillators : colloids driven by optical tweezers (a) back and forth along a nearly one-dimensional path, and (b) along circular trajectories. In the first model, I will show that the state of synchronization is controlled by the shape of the driving potential. The second model displays a rich physics : two different mechanisms lead to the synchronization, and configurations of six oscillators can synchronize in metachronal waves.

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