'Battery-free, quiet, and inherently private' — These 3D-printed metal tags could change home and office tracking, turning penny-sized discs into smart devices using ultrasonic tech for maintenance-free monitoring without charging
The tags use ultrasonic sound to record everyday actions
by https://www.techradar.com/uk/author/wayne-williams · TechRadarNews By Wayne Williams published 28 April 2026
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- Battery-free metal tags generate ultrasonic signals when objects move nearby
- Different disk shapes create unique sound signatures that identify tracked actions
- Simulation tools produced hundreds of tag designs for varied real-world tracking uses
Researchers at Georgia Tech have built tiny metal tags that record everyday actions without needing batteries, charging cables, or wired power - instead relying on simple motion and sound rather than electronics inside each tag.
Most smart home sensors rely on batteries or wall power, which requires maintenance over time. These tags work differently, using mechanical contact to generate a brief ultrasonic signal whenever something moves.
Each tag sits on a small 3D-printed base attached to a fixed surface such as a cabinet frame. A matching tab sits on the moving object. When that object opens or closes, the tab strikes the metal disk and creates a short ultrasonic pulse.
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Each frequency a unique identifier
That pulse is too high in frequency for people to hear, but nearby microphones can detect it. A wearable device records the signal and logs what happened, such as opening a drawer or closing a door.
Shape plays a key role in how the tags work, since different cutouts along the metal edge produce different ultrasonic frequencies.
Each frequency acts like a unique identifier, allowing a lot of tags to operate in the same area without problems.
“Those unique fingerprints can be used for smart home sensing, or what we call ‘activity recognition,’” said Yibo Fu, a robotics Ph.D. student who led development of the tags.
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