Coordinated motion of multiple cilia.
Progressive waves are generated by coordinated motion of multiple
cilia, which is used to transfer fluid or tiny particles, or are used to propel a microscopic
organism itself. An example of the former is the ejection of microscopic waste from human tracheae,
and of the latter is the swimming of unicellular organisms, such as paramecium. By imitating these
ciliary motions, actuators with many artificial cilia have been fabricated by micromachining.