Credit: © 2007 ACS

Cilia, which are the flexible hair-like structures lining the walls of our stomach and lungs, are important in maintaining the movement of fluids. Now, researchers at the University of North Carolina and West Virginia University in the USA have produced magnetic nanorod arrays that can move like cilia when placed in a magnetic field.

Using a template, Richard Superfine and colleagues1 combined an iron oxide-based ferrofluid with a polymer matrix to form arrays of rods with the same width and aspect ratio as cilia — about 200 nm in diameter and 10 mm long. An appropriately positioned magnetic field causes the rods to either move back-and-forth or rotate, an effect that is thought to result from field gradients.

The nanorods sweep over a wide distance at a rate of approximately 15 Hz, which is close to the frequency of cilia found in the human lung airway. These structures can be used to study the mechanics of fluid flow in the many ciliated systems in our body and are potentially useful in various sensing, photonic and microfluidic applications.