Built using modern nanofabrication and nanophotonics techniques, the ultraprecise ultrasound sensor on a silicon chip could revolutionize medical devices and spatial imaging used in unmanned vehicles, say the researchers.
"We've developed a near perfect ultrasound detector, hitting the limits of what the technology is capable of achieving," says Professor Warwick Bowen, from UQ's Precision Sensing Initiative and the Australian Centre for Engineered Quantum Systems. "This is a major step forward, since accurate ultrasound measurement is critical for a range of applications."
Such applications include medical ultrasound, as well as high-resolution biomedical imaging to detect tumors and other anomalies. It's also commonly used for spatial applications, such as in the sonar imaging of underwater objects or in the navigation of unmanned aerial vehicles.
Improving these applications requires smaller, higher-precision sensors, which, say the researchers, is exactly what they've been able to develop.
Based on cavity optomechanical ultrasound sensing, where dual optical and mechanical resonances enhance the ultrasound signal, the sensor achieves noise equivalent pressures of 8–300µPa Hz -1/2 at kilohertz to megahertz frequencies in a microscale silicon-chip-based device with a greater than 120-dB dynamic range. Its sensitivity far exceeds similar sensors that use an optical resonance alone and, normalized to the sensing area, surpasses previous air-coupled ultrasound sensors by several orders of magnitude, say the researchers.
"We're now able to measure ultrasound waves that apply tiny forces – comparable to the gravitational force on a virus – and we can do this with sensors smaller than a millimeter across," says Bowen.
The accuracy of the technology, says research leader Dr Sahar Basiri-Esfahani, could change how scientists understand biology.
"We'll soon have the ability to listen to the sound emitted by living bacteria and cells," says Basiri-Esfahani. "This could fundamentally improve our understanding of how these small biological systems function. A deeper understanding of these biological systems may lead to new treatments, so we're looking forward to seeing what future applications emerge."