Cilia and flagella are fundamental units of motion in cellular biology. These beating, hair-like organelles share a common basic structure but maintain widely varying functions in systems ranging from the isolated flagella of swimming algae to the dense ciliary carpets that pump fluid in the brains of mammals. Experiments and models have begun to elucidate the inner workings of single cilia as complex nonlinear oscillators, and the variety of hydrodynamical phenomena that result from beating dynamics. These results have shed light on complex locomotion strategies observed in single-celled microorganisms and collective phenomena observed in microbial suspensions. In animal systems, dense ciliary arrays exhibit a variety of emergent phenomena, including active filtration, noise robustness and metachronal waves. Surprising phenomena have been observed in neuronally controlled ciliary arrays, demonstrating the need for new physical models of cilia that include central control, defect dynamics and topology. We review the emergent physics of cilia across scales, starting from the microscale dynamics of single cilia, and then proceeding to microorganisms and animal systems.

纤毛和鞭毛是细胞生物学中运动的基本单位。这些搏动的，毛发状的细胞器具有相同的基本结构，但在从游泳藻类的孤立鞭毛到向哺乳动物的脑中泵入液体的致密的睫毛地毯等系统中，其功能保持着广泛变化。实验和模型已经开始阐明单个纤毛作为复杂的非线性振荡器的内部工作原理，以及由跳动动力学引起的各种流体动力学现象。这些结果揭示了在单细胞微生物中观察到的复杂运动策略以及在微生物悬浮液中观察到的集体现象。在动物系统中，密集的睫状体阵列表现出各种新兴现象，包括主动过滤，噪声鲁棒性和历时波。在神经控制的睫毛阵列中观察到令人惊讶的现象，表明需要新的纤毛物理模型，包括中央控制，缺损动力学和拓扑结构。我们从单个纤毛的微观动力学开始，再到微生物和动物系统，回顾了不同尺度的纤毛的新兴物理学。