A lab-on-a-chip, or microfluidic device, integrates multiple lab functions onto one chip just millimeters or centimeters in size. The devices allow researchers to experiment on tiny sample sizes and to perform multiple experiments simultaneously on the same material. The goal is that they could lead to instant home tests for illnesses, food contaminants and toxic gases.
To do an experiment in a microfluidic device, researchers often use dozens of air hoses, valves and electrical connections between the chip and a computer to move, mix and split pin-prick drops of fluid in the device's microscopic channels and divots.
"You'd really like to see something the size of an iPhone that you could sneeze onto and it would tell you if you have the flu. What hasn't been developed for such a small system is the pneumatics--the mechanisms for moving
chemicals and samples around on the device," says says Mark Burns, professor and chair of the Department of Chemical Engineering and professor in the Department of Biomedical Engineering.The U-M researchers use sound waves to drive a unique pneumatic system that does not require electromechanical valves. Instead, musical notes produce the air pressure to control droplets in the device.
The system replaces 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 along in the microfluidic device.
"Each resonance cavity on the device is designed to amplify a specific tone and turn it into a useful pressure," explains Sean Langelier, a chemical engineering doctoral student. "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."
The new system is still external to the chip, but the researchers are working to make it smaller and incorporate it on a microfluidic device.
A paper, titled "Acoustically-driven programmable liquid motion using resonance cavities," will be published online in the Proceedings of the National Academy of Sciences.
Source: University of Michigan