Okinawa Institute of Science and Technology Graduate University, Onna-son, Okinawa, 904-0495, Japan.
Small. 2020 Mar;16(9):e1903872. doi: 10.1002/smll.201903872. Epub 2019 Nov 20.
Fluid-structure interactions lie at the heart of the complex, and often highly coordinated, motions of actively driven microscale biological systems (e.g., translating cilia, flagella, and motile cells). Due to the highly viscoelastic nature of most relevant biological fluids and the small length scales involved, the viscous and inertial forces in such flows are dominated by elasticity. However, elastic effects are often overlooked in studies seeking to address phenomena like the synchronization of beating cilia. In this study, unique microfluidic experiments are presented to demonstrate that inertia-free viscoelastic flows can lead to highly regular beating of an immersed (passive) flexible structure, herein named "purely-elastic" fluid-structure interaction. It is also shown how two such flexible structures can achieve an extraordinary degree of synchronization, with a correlation coefficient approaching unity. The synchronization is a result of the generation of localized elastic stresses in the fluid that effectively link the two objects. These purely elastic interactions may be important to consider toward developing a complete understanding of the motions of microscale biological systems.
流固相互作用是主动驱动的微观生物系统（例如，正在运动的纤毛、鞭毛和游动细胞）复杂且通常高度协调的运动的核心。由于大多数相关生物流体具有高度黏弹性，并且涉及的长度尺度很小，因此此类流中的黏性力和惯性力主要由弹性主导。然而，在研究旨在解决诸如纤毛拍打同步等现象的过程中，弹性效应通常被忽视。在这项研究中，提出了独特的微流控实验来证明无惯性黏弹性流可以导致浸入式（被动）柔性结构的高度规则拍打，在此称为“纯弹性”流固相互作用。还展示了如何使两个这样的柔性结构实现非凡程度的同步，相关系数接近 1。同步是由于在流体中产生局部弹性应力，从而有效地将两个物体连接起来。这些纯弹性相互作用对于全面了解微观生物系统的运动可能很重要。
