The team’s breakthrough came late at night.
After a full year of equations, circuit boards, experimentation and debugging sessions, they were all in the lab together when it finally happened — a small polystyrene particle hovered into the air.
Then it moved.
First in a straight line, then in a square pattern.
And it was guided only by carefully orchestrated sound waves they had created.
“The moment we saw an actual particle go from hanging in mid-air to moving around was phenomenal to say the least,” says team member Kieran D’Sena, who graduated last week from the Engineering Physics and Biomedical Engineering program at McMaster University. “Seeing it actually work right in front of us was a pretty incredible feeling.”
This summer, the students behind this feat of engineering will travel to China to present their acoustic levitation research at the International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS2026), taking their capstone project to a global showcase of student innovation.
An invisible cage of sound
But what is acoustic levitation?
Imagine you have two sets of tiny speakers facing each other, explains the group. One set of speakers is placed on the top and one set is placed on the bottom. These speakers vibrate way too fast for us to hear, but they push air back and forth quickly.
This exchange of air creates zones between the speakers. Some zones have a lot of air packed tightly together, while others have little air. By precisely timing each speaker using fast electronics that operate at extremely high frequencies on a micro scale, the group can control where those zones appear.
This manipulation creates what the group calls an “invisible cage.”
“If we create a low-pressure zone completely surrounded by high-pressure zones, anything placed inside gets pushed in from all sides and just floats there” explains team member Alicia Agostini, who recently finished her degree in Engineering Physics and Biomedical Engineering. “That’s acoustic levitation.”
The real fun, however, starts when it comes to timing manipulation.
The system that the team built allows them to adjust the timing electronically, with no moving parts at all. This allows them to freely manipulate a particle within a 3D space.
Massive impact on the micro scale
This technique can have serious implications on the micro-assembly of small and delicate parts, specifically in the field of medical microrobotics and miniaturization, explains capstone supervisor and assistant professor in Computing and Software Onaizah Onaizah.
To navigate through narrow and complex pathways inside the body, such as blood vessels, airways and the gastrointestinal tract, robots need to be extremely small but still capable of doing useful tasks. But the things that traditional robotic systems rely on — onboard motors, batteries and electronics — are impractical at such a small scale, which means these microrobots need to be controlled wirelessly from outside the body.
The traditional way to manipulate these tiny objects, like surgical tools or miniature biomedical devices, is with magnetics. The idea is you generate a magnetic field and use it to push or pull a small object wherever you want it to go.
The problem with this method is that magnetic force experiences a steep drop off the further away the object is from the magnet, so you’re limited to either very small work areas or large work areas that consume lots of power.
By contrast, the team’s acoustic actuation system demonstrated stable levitation across much larger working volumes, all in mid-air and completely contactless.
That kind of reach, explains the team, opens up a lot of possibilities for targeted drug delivery, guiding ingestible micro-devices through the body or doing delicate micro-assembly work where any physical contact would risk damaging or contaminating the material you’re working with.
The success this group was able to have, says Onaizah, was truly outstanding.
“My original project proposal involved a combination of acoustic and magnetic actuation, but the team successfully achieved 3D control of levitated polystyrene beads, and potentially other particles, using acoustic actuation alone,” says Onaizah.
“This is an incredibly impressive achievement that demonstrates a high level of independent thinking and innovation.”
Going global
Now, just a few months after presenting their work at McMaster Engineering’s Capstone Expo, the team is ready to take it global when they attend MARSS2026 in China at the end of July.
“When the acceptance came through there was a real moment of disbelief,” recalls team member Liam Fitzhenry, a graduate of the Electrical and Biomedical Engineering program. “And then it sank in that we’d be presenting our work at an international conference, and that feeling pretty quickly turned into excitement.”
MARSS2026, the flagship forum to discuss microrobotics manipulation and automation and small-scale robotics, is supported by the IEEE Robotics and Automation Society and the IEEE Nanotechnology Council. Four papers from Onaizah’s HEART Lab will be presented at the conference, three of which will be presented by undergraduate students who have worked in the lab.
“For most of us, this will be our first time presenting research to an international academic audience, so this is a rare opportunity for us to develop our communications skills outside the classroom,” says Luca Scanga, who recently finished his degree in Engineering Physics and Biomedical Engineering.
“It’s hard to put a value on that when you’re still a student, but it tends to matter a lot down the road.”