Precise, gentle and efficient cell separation from a device the size of a cell phone may be possible thanks to tilt-angle standing surface acoustic waves, according to a team of engineers.
"For biological testing we often need to do cell separation before analysis," said Tony Jun Huang, professor of engineering science and mechanics. "But if the separation process affects the integrity of the cells, damages them in any way, the diagnosis often won't work well."
Tilted-angle standing surface acoustic waves can separate cells using very small amounts of energy. Unlike conventional separation methods that centrifuge for 10 minutes at 3000 revolutions per minute, the surface acoustic waves can separate cells in a much gentler way. The power intensity and frequency used in this study are similar to that used in ultrasonic imaging, which has proven to be extremely safe, even for fetuses. Also, each cell experiences the acoustic wave for only a fraction of a second, rather than 10 minutes.
"The tilted-angle standing surface acoustic waves method has the least disturbance or disruption to the living cells being separated compared to other available methods so far," said Ming Dao, principal research scientist, materials science and engineering, Massachusetts Institute of Technology. "It adds to the portfolio of latest technology developments for separating such things as rare circulating tumor cells in the blood."
Previous work by Huang showed that acoustic tweezers work by setting up a standing surface acoustic wave. If two sound sources are placed opposite each other and each emits the same wavelength of sound, there will be a location where the opposing sounds cancel each other. Because sound waves have pressure, they can push very small objects, so a cell or nanoparticle will move with the sound wave until it reaches the location where there is no longer movement.
If the sound sources are at right angles to each other, an evenly spaced set
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