Ultrasound technology has been in wide use for decades, helping submarines navigate and letting doctors non-invasively peer inside patients, but it might be about to get a whole lot more powerful. Researchers have developed an "ultra" ultrasound sensor that is so sensitive it can hear air molecules moving around or the vibrations of individual cells.

In a normal ultrasound device, the emitter and receiver is made of piezoelectric crystals. That means they vibrate when a current is applied to them, which creates high frequency sound waves beyond the range of human hearing. Those sound waves pass through air, water or soft tissue and will bounce back at different rates as they hit more solid surfaces. When they return to the crystals, the process works in reverse – the vibrations generate current, and computers can decipher that information to create an image, giving, for example, a clear view of a fetus in the womb.

But, of course, there are limits to how sensitive those devices can get. To push through this, researchers at the University of Queensland used a completely different setup to make their ultra ultrasound sensors. The receiver in this case is a tiny silica disk, 148 microns wide and 1.8 microns thick, and behind that is a laser. As sound waves hit the disk in different places, the surface distorts ever so slightly, and the laser can read those disturbances to produce a much more precise image.

"It's based on new capability we have developed using laser light to measure nanoscale mechanical motion – at the level of attometers (a thousandth of the width of an atomic nucleus)," Professor Warwick Bowen, corresponding author of the study, explains to New Atlas. "This capability was developed to enable new quantum technologies. Here we use it, instead, for ultrasound sensing. The ultrasonic wave drives mechanical vibrations of a microscale structure on a silicon chip, which we then read out with laser light."

According to Bowen, these new sensors are about a hundred times more precise than existing technologies. The device can measure ultrasound waves that apply forces so tiny they're on the scale of gravity's effect on a virus, and it can actually hear air molecules randomly moving around. In a more practical sense, this ultra ultrasound could soon be used to listen to individual cells and bacteria.

"Short term, the sensors could provide a new way to study the health and function of cells," says Bowen. "Living cells vibrate as they function. Listening to these vibrations can provide signals, not only about whether the cell is alive or dead, but also about whether it is healthy or sick, whether it's normal or cancerous, or just about what processes are going on inside. Our sensors provide a way to directly listen to these vibrations at the single cell level."

Eventually, the technology could also be put to use improving navigation for aerial and underwater vehicles, and in the longer term, unlock a whole new range of medical imaging possibilities, such as monitoring the movements of individual cells through the body.

The research was published in the journal Nature Communications.