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New “sound wave” knife is so accurate, surgeons can detach a single cancer cell with it

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Sound waves in music

Scientists at the University of Michigan have developed a new knife that uses high-amplitude sound waves, instead of a knife blade, to cut tissue.  The new sound-based knife, which can focus sound waves to finer points than ever before,  is magnitudes more accurate than previous technologies.  It can cut an area of tissue, using pressure rather than heat, that measures as little as 75 by 400 micrometer allowing researchers to remove a single ovarian cancer cell and cut a 150 micrometer hole through the middle of an artificial kidney stone. In fact, the beam is so finely focused, painless surgery may be possible by simply avoiding nerve fibers. Researchers who developed the new therapeutic ultrasound approach say its use could be ground-breaking.

“We believe this could be used as an invisible knife for noninvasive surgery. Nothing pokes into your body, just the ultrasound beam. And it is so tightly focused you can disrupt individual cells.”

The device generates the sound waves using a pulsed laser beam.  The pulsed laser is beamed through a lens coated with carbon nanotubes and a rubbery material called polydimethylsiloxane. The light is absorbed into the carbon nanotube layer and converted into heat which is boosted by the rubbery polydimethylsiloxane material (which absorbs the generated heat) via rapid thermal expansion (i.e. it vibrates).  The lens further focuses the sound wave to a very confined area.

“A major drawback of current strongly focused ultrasound technology is a bulky focal spot, which is on the order of several millimeters. A few centimeters is typical. Therefore, it can be difficult to treat tissue objects in a high-precision manner, for targeting delicate vasculature, thin tissue layer and cellular texture. We can enhance the focal accuracy 100-fold.”

The sound waves generated by the knife are 10,000 times higher than a human can hear.

Sources: University of Michigan