Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0900043106 (2009)

Microfluidic systems use networks of tiny chambers and channels to mix small volumes of solution. Controlling these systems often requires cumbersome pumps and valves that are much larger than the microfluidic devices themselves.

The problem struck a chord with Mark Burns and his colleagues at the University of Michigan in Ann Arbor. So the team attached a microfluidic device to a series of resonant acoustic cavities that respond to different frequencies (pictured). When resonant, each cavity applies a specific output pressure to the microfluidic system. The pressure applied — and thus the movement of fluids along channels — can be controlled using a simple melody. The authors hope that their tiny tunes will lead to more compact control systems for microfluidics.