Concurrent Actuation and Sensing in Fluid by Cilia‐Like Transducers

Motile cilia are miniature, hair‐like organelles whose beating moves fluid in various organisms and the human body. Motile cilia are also able to sense many mechanical or fluidic cues. Inspired by the motile cilia in nature, a type of artificial cilia that can both actuate and sense is investigated. These artificial cilia can operate their sensing and actuation individually to sense the flow speed and collaboratively transport objects. More importantly, they can also sense the viscosity of the fluid and the distance from the wall by beating and feeling their own motion. In the latter function, two different sensing modes (modes 1 and 2) are proposed for low and high Reynolds numbers. They are investigated through both computational fluid dynamics and experiments. It is found that mode 1 can sense a wall distance up to 3 times the body length of the cilium, while mode 2 can sense up to 2 times. Such sensing of distance can be further converted into the ability to compute the morphology of the boundary inside the fluid. This work can be useful for small‐scale soft robots that work inside fluid and other flow control applications.