Two Teams Trap First Complete Sound Rainbows on Chips
Get the Health newsletter
Daily health & science — research, biotech, public health, the studies worth knowing. Free.
- Riyi Zheng's team at South China University of Technology trapped a full phonon rainbow on a silicon chip, while Yafeng Chen's team at Tongji University created one in an aluminium device — the most complete elastic rainbows achieved to date.
- Both teams used microscopic patterns such as tiny triangular pillars to steer phonons, effectively mimicking how electromagnetic fields constrain electrons in thin materials.
- Zheng's team demonstrated the rainbow could route an incoming elastic wave through only one specific frequency 'patch,' showing the effect isn't just visual but functional.
- Chen's team imaged their rainbow by illuminating ultrasonic sound with a laser and recording the vibrations; Chen said watching the waves 'smoothly separate and localise at their exactly predicted locations' was 'an incredible experience.'
- Kosmas Tsakmakidis at the National and Kapodistrian University of Athens called the technique 'conceptually beautiful,' comparing the patterned geometry to embedding magnetic and electric fields designed specifically for sound.
- Sebastien Guenneau at Imperial College London said the results could enable vibration filters, ultrasonic routers, sensitive mechanical sensors, and energy harvesters, and could open new avenues for exploring quantum effects and Einstein's special relativity in material settings.
- Henning Schomerus at Lancaster University cautioned applications are unlikely to be immediate — existing devices need to be made smaller and trap more vibrational energy — and Chen said his group is already pursuing ultra-compact on-chip acoustic devices.
Why it matters: Both studies were published in Physical Review Letters, giving the field of phononics its first reproducible method for trapping and sorting phonons across full material regions rather than tiny corners. For device engineers, the work supplies a concrete blueprint for on-chip vibration filters, ultrasonic routers, and mechanical sensors, while Schomerus's caveat — that current devices must shrink and capture more vibrational energy — defines the near-term engineering bottleneck Chen's team is already attacking.
Ask SkimNews
