Sound printing research named in top 10 scientific discoveries of the year by Québec Science magazine
There was a moment, after many trials and errors, that a team of engineering researchers at Concordia University realized they had achieved something remarkable.
It may not have looked like much from the outside: a few clicks on a computer screen, the whir of a 3D printer and a few bubbles solidifying in a plastic dish filled with liquid.
But this — at precisely 7:27 pm on April 27, 2018 — was the first time in the world that anyone had successfully printed a 3D object using sound waves.
"We were jumping, honestly, because we couldn't believe that," said Muthukumaran Packirisamy, professor of engineering and director of the optical-bio microsystems lab at Concordia.
"It was a great moment for us … we had a lot of fun and parties after that!"
The team is now celebrating once again as its research, published last April in the journal Nature Communications, is being honoured as one of the top 10 scientific discoveries of the year by Québec Science magazine.
It's a technology Packirisamy's team believes could be used in the future for everything from repairing spacecraft and nuclear reactors, to printing medical devices directly into a patient's body.
Direct sound printing works through a process called cavitation, explained Mohsen Habibi, a research associate at the lab.
Ultrasound waves are used to trigger a series of tiny chemical reactions, lasting only a matter of nanoseconds. The reactions produce immense amounts of pressure and heat, causing bubbles to form in the print material, then solidify.
"Those bubbles create polymerization basically, so they solidify the liquid resin into solid," said Habibi.
As those bubbles form and solidify, the 3D object takes shape, layer by layer, in whatever design the team wants.
So far, they've printed everything from delicate honeycomb patterns, to gears and propellers and even the outlines of human ears and noses.
High intensity focused ultrasound (HIFU) has already been used in medical procedures to destroy tissues, such as for tumour ablations.
"This is the first time that we use this sonic chemistry of the ultrasonic waves to create things," said Packirisamy.
He said sound printing can produce objects as thin as 100 microns — about the width of a human hair — and could work with a variety of materials such as plastic, metal, ceramic or biomaterials.
While 3D printing in itself is not new, Packirisamy said direct sound printing offers some advantages over existing technologies, many of which use lasers to manipulate the build material so the object can take shape.
"Sound can penetrate through barriers where light cannot," said Packirisamy.
This opens the potential for 3D printing an object directly into a hard-to-reach place, such as the engine of an airplane or under the skin of a surgical patient.
If a polymer or synthetic tissue were injected into the patient's body, the sound printer could be used outside the body to form the material into the necessary shape, he said.
Everything from stents to — eventually — synthetic organs, could be printed, according to Packirisamy.
"Also we can do the repairing of inside bio-organs. That's a future possibility," he said.
The team tested this theory by sending ultrasound waves through a 15 mm layer of pig tissue. They succeeded in printing a small 3D maple leaf on the other side.
While it all sounds a little sci-fi, PhD student Shervin Foroughi said theoretically it could allow patients to avoid undergoing open surgery.
"It enables surgeons to do minimally invasive surgeries and … it will reduce the recovery time for the patients," he said.
Top 10 discovery
It's in part because of these potential societal impacts that the research was named one of the top 10 scientific discoveries of the year by Québec Science magazine.
"It's amazing, it's something that could have many applications in multiple industries. Obviously in hospitals, but also in aerospace and many industries," said Mélissa Guillemette, editor in chief of Québec Science magazine, on CBC's All in a Weekend.
"It's something that had a lot of impact in the scientific community," she said. "A lot of people were amazed by this work."
For Pakirisamy, the magazine's honours were unexpected but welcome, adding that the team now feels a renewed sense of purpose to further their work.
"It is a really defining moment for us," he said.
"It gives a new momentum and new drive for us to take the technology and apply it to society in a much more meaningful way."
ABOUT THE AUTHOR
Ainslie MacLellan is a journalist at CBC Montreal. Follow her on Twitter: @CBCAinslie.
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