Zernike Institute for Advanced Materials, University of Groningen, 9747AG Groningen, The Netherlands.
Department of Mechanical Engineering and Institute for Complex Molecular Systems, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Soft Matter. 2022 May 25;18(20):3902-3909. doi: 10.1039/d1sm01680f.
Motile cilia can produce net fluid flows at low Reynolds number because of their asymmetric motion and metachrony of collective beating. Mimicking this with artificial cilia can find application in microfluidic devices for fluid transport and mixing. Here, we study the metachronal beating of nonidentical, magnetically-programmed artificial cilia whose individual non-reciprocal motion and collective metachronal beating pattern can be independently controlled. We use a finite element method that accounts for magnetic forces, cilia deformation and fluid flow in a fully coupled manner. Mimicking biological cilia, we study magnetic cilia subject to a full range of metachronal driving patterns, including antiplectic, symplectic, laeoplectic and diaplectic waves. We analyse the induced primary flow, secondary flow and mixing rate as a function of the phase lag between cilia and explore the underlying physical mechanism. Our results show that shielding effects between neighboring cilia lead to a primary flow that is larger for antiplectic than for symplectic metachronal waves. The secondary flow can be fully explained by the propagation direction of the metachronal wave. Finally, we show that the mixing rate can be strongly enhanced by laeoplectic and diaplectic metachrony resulting in large velocity gradients and vortex-like flow patterns.
纤毛的不对称运动和同步拍动可以在低雷诺数下产生净流动，这使得模仿纤毛的运动在微流控装置中的流体输运和混合方面有很好的应用。在这里，我们研究了非对称、可编程的磁性人工纤毛的同步拍动，其个体的非往复运动和集体的同步拍动模式可以独立控制。我们使用有限元方法来全面考虑磁力、纤毛变形和流体流动。模仿生物纤毛，我们研究了受各种同步拍动驱动模式影响的磁性纤毛，包括反拍动、正拍动、交错拍动和对心拍动波。我们分析了诱导的主流、二次流和混合率作为纤毛相位差的函数，并探讨了潜在的物理机制。我们的结果表明，相邻纤毛之间的屏蔽效应导致反拍动的主流比正拍动的主流更大。二次流可以完全用同步拍动波的传播方向来解释。最后，我们表明交错拍动和对心拍动可以大大提高混合率，从而产生大的速度梯度和涡旋状的流动模式。
