Activating microfluidic devices using electro-mechanical switches can be a tricky, complicated business. Now a team at the University of Michigan developed a pneumatic system that is precisely activated by different audible sound frequencies. By using one pneumatic unit that can pump different channels depending on audio frequency, microfluidic devices using this approach can potentially be made a lot simpler and smaller.
The system developed by Burns [Mark Burns, professor and chair of the Department of Chemical Engineering and a professor in the Department of Biomedical Engineering], chemical engineering doctoral student Sean Langelier, and their collaborators replaces these air hoses, valves and electrical connections with what are called resonance cavities. The resonance cavities are tubes of specific lengths that amplify particular musical notes.
These cavities are connected on one end to channels in the microfluidic device, and on the other end to a speaker, which is connected to a computer. The computer generates the notes, or chords. The resonance cavities amplify those notes and the sound waves push air through a hole in the resonance cavity to their assigned channel. The air then nudges the droplets in the microfluidic device along.
“Each resonance cavity on the device is designed to amplify a specific tone and turn it into a useful pressure,” Langelier said. “If I play one note, one droplet moves. If I play a three-note chord, three move, and so on. And because the cavities don’t communicate with each other, I can vary the strength of the individual notes within the chords to move a given drop faster or slower.”
Burns describes the set-up as the reverse of a bell choir. Rather than ringing a bell to create sound waves in the air, which are heard as music, this system uses music to create sound waves in the device, which in turn, move the experimental droplets.
Here’s a demo video showing different channels and how one would mix and manipulate them:
Here’s one more if this is your kind of music:
More from the University of Michigan: Music is the engine of new U-M lab-on-a-chip device…
Abstract in PNAS: Acoustically driven programmable liquid motion using resonance cavities