Metachronal waves in magnetic micro-robotic paddles for artificial cilia (dataset)

Biological cilia generate fluid movement within viscosity-dominated environments using beating motions that break time-reversal symmetry. This creates a metachronal wave, which enhances flow efficiency. Artificially mimicking this behaviour could improve microfluidic point-of-care devices, since viscosity-dominated fluid dynamics impede fluid flow and mixing of reagents, limiting potential for multiplexing diagnostic tests. However, current biomimicry schemes require either variation in the hydrodynamic response across a cilia array or a complex magnetic anisotropy configuration to synchronise the actuation sequence with the driving field. Here, we show that simple modifications to the structural design introduce phase differences between individual actuators, leading to the spontaneous formation of metachronal waves. This generates flow speeds of up to 16 μm/s as far as 675 μm above the actuator plane. By introducing metachronal waves through lithographic structuring, large scale manufacture becomes feasible. Additionally, by demonstrating that metachronal waves emerge from non-uniformity in internal structural mechanics, we offer fresh insight into the mechanics of cilia coordination.

生物纤毛（biological cilia）通过打破时间反演对称性（time-reversal symmetry）的摆动运动，在粘性主导环境中产生流体流动。这一过程会形成异时波（metachronal wave），从而提升流动效率。人工复刻这一行为可优化微流体即时检测设备，因为粘性主导的流体动力学特性会阻碍流体流动与试剂混合，进而限制了多重诊断检测的应用潜力。然而，当前的仿生方案要么需要纤毛阵列的流体动力学响应存在差异，要么需要复杂的磁各向异性（magnetic anisotropy）结构，才能将驱动序列与驱动场同步。本研究表明，仅需对结构设计进行简单修改，即可在各执行器之间引入相位差，进而自发形成异时波。该结构可在执行器平面上方最远675 μm处产生最高达16 μm/s的流动速度。通过光刻结构构建异时波，大规模制造成为可能。此外，本研究证实异时波源于内部结构力学的不均匀性，为纤毛协调机制的力学研究提供了全新视角。