Sound-wave chip might shrink the lab

"We hope this technology will become a valuable part of laboratory equipment," says Ivo Leibacher. (Credit: Ivo Leibacher/ETH Zurich)

One of the biggest hurdles to miniaturizing laboratory experiments is figuring out how to manipulate minuscule amounts of liquid or individual cells on a chip.

Ivo Leibacher and Peter Reichert, doctoral students at the Institute of Mechanical Systems at ETH Zurich, developed a system to move tiny droplets. The concept is based on acoustophoresis, which uses a stationary ultrasonic wave to move aqueous droplets through a carrier liquid of oil on a silicon-glass chip.

The droplets, which have a diameter of 50 to 250 micrometers, cannot mix with the carrier liquid, nor can they evaporate.

“On this scale, the droplets are very stable because they are held together by the surface tension,” Leibacher explains.

illustration of ultrasonic chip
With ultrasound, represented by curved red and blue lines, researchers move micro-droplets for sorting and analysis. (Credit: ETH Zurich / Ivo Leibacher)

How it works

When the stationary ultrasonic waves are applied, the droplets move in the node of the wave. This means researchers can place two different droplets in both sides of the channel to merge them in a controlled manner.

Changing the frequency, on the other hand, guides targeted drops with, for example, a light signal into a branched-off channel.


By separating them in this way, they can be sorted and analyzed after the end of the experiment.

“One of the advantages of our technology is its high biocompatibility and versatility,” says Reichert.

Previous methods in which researchers manipulated individual cells on a tiny scale resulted in cases of cells being damaged. This method can be used for cells as well as for DNA, reagents, and chemicals.

“We hope this technology will become a valuable part of laboratory equipment, allowing for experiments in high throughput with minimal consumption,” says Leibacher.

The researchers, who describe the technology in the journal Lab on a Chip, have filed a patent application for the method.

Source: ETH Zurich