Researchers at the University of Michigan have succeeded in developing a chip used to conduct experiments on fluids which is driven by sound rather than electromechanical valves. This approach could be a big step forward in reducing costs and complexity in areas ranging from chemical analysis to environmental monitoring.
Labs-on-a-chip and their current limitations
A lab-on-a-chip (LOC) is a device that integrates several laboratory functions on a single chip, including analysis and manipulation of tiny drops of liquid each less than a thousand billionth of a liter in volume.
The main advantage in using this approach resides mainly in the greatly reduced amounts of the sample needed, which in turn brings to lower costs in terms of production and a lower overall power consumption. The other main advantage is the faster analysis and response time, mainly due to the shorter distances as well as a higher surface-to-volume ratio in the droplets.
However, today's LOCs suffer a big limitation in that they need to rely on a number of external and relatively big air hoses and valves in order to move, mix and split the tiny drops directing them into the many microscopic channels: as a consequence, this technology is unable to scale down in size to meet the requirements for some potentially very interesting applications.
"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," Prof. Mark Burns, who is part of the research group, explained.
The music-driven LOC
The team found a clever solution to the problem, choosing to use sound waves instead of electromechanical valves to control the droplets. In the system, air hoses, valves and electrical connections are replaced with so-called resonance cavities, tubes of specific lengths that, like an organ, amplify particular musical notes. The cavities are connected on one end to channels in the microfluidic device, and to a speaker on the other end.
Each resonance cavity on the device is designed to amplify a specific tone and turn it into a useful pressure, and so movement of a droplet can be achieved simply by playing a certain note. More than one droplet can be moved at the same time by playing chords instead of a single note and, since the cavities are not interconnected, playing one note louder will make the connected droplet move further away independently of the others.
The new system is still external to the chip, but has the advantage of using a single off-chip connection, compared to the several hundreds previously needed on standard labs-on-a-chip. The researchers are working on miniaturizing the system in order to implement their solution on an actual LOC.
Looking at the future, this technology has the potential to scale down considerably by means of nanotechnology, making it possible to obtain single-cell analysis and nano-sensors much closer to reality.
See the UM video here.