This Trampoline-Like Sensor Turns Sound Into High-Precision Distance Measurements Through Materials

Physicists at Delft University of Technology have built a novel sensor, shaped like a trampoline, which can measure distances through materials — like water or the human body — with incredible accuracy, based on how the material sounds.

"It only requires inserting a laser, and nothing else. There’s no need for complex feedback loops or for tuning certain parameters to get our tech to operate properly. This makes it a very simple and low-power technology, that is much easier to miniaturize on a microchip," claims corresponding author Richard Norte of the sensor the team has developed. "Once this happens, we could really put these microchip sensors anywhere, given their small size."

The prototype chip, dubbed a mechanical overtone frequency comb, houses a thin sheet of ceramic material shaped like a trampoline — and just like a trampoline it's used to bounce. Rather than kids at a party, though, this trampoline bounces laser light — using a pattern of holes to create a signature signal which can be used for distance measurements based on the material's vibrations in the presence of sound waves.

The project is based on two otherwise-unrelated concepts, frequency combs and optical trapping. "The interesting thing is that both of these concepts are typically related to light, but these fields do not have any real overlap," Norte explains. "We have uniquely combined them to create an easy-to-use microchip technology based on sound waves. This ease of use could have significant implications for how we measure the world around us.

“Optical frequency combs are used in labs around the world for very precise measurements of time," Norte continues, "and to measure distances. They are so important to measurements in general that their invention was given a Nobel Prize in 2005.

"We have made an acoustic version of a frequency comb, made out of sound vibrations in the membrane instead of light. Acoustic frequency combs could for instance make position measurements in opaque materials, through which vibrations can propagate better than light waves. This technology could for example be used for precision measurements underwater to monitor the Earth’s climate, for medical imaging, and for applications in quantum technologies."

The team's work has been published under open-access terms in the journal Nature Communications.

Main article image courtesy of Sciencebrush.