This miniaturized, battery-free sensor could offer uses in medical devices. [Image courtesy of ETH Zurich]
A new type of mechanical sensor developed by researchers in Switzerland could eliminate the need for batteries in this type of technology.
The reach of these battery-free sensors could extend to medical devices, too.
Marc Serra-Garcia and ETH Zurich geophysics professor Johan Robertsson led a team of researchers developing the technology. The creators applied for a patent and presented the principle in the journal Advanced Functional Materials.
“The sensor works purely mechanically and doesn’t require an external energy source. It simply utilises the vibrational energy contained in sound waves,” Robertsson said in a post on the ETH Zurich website.
Sound waves emitted from spoken words or particular tones or noises cause the sensor to vibrate. The energy from the vibrations generates a tiny electrical pulse that switches on an electronic device that has been switched off. The team already patented its prototype, which can distinguish between the spoken words “three and “four.” “Four” has more sound energy that resonates with the sensor than “three,” the researchers say. This causes the sensor to vibrate, while “three” does not, meaning it could switch on a device or trigger further processes.
New variants of the technology could distinguish between up to 12 different words. Those include standard commands like “on,” “off,” “up” and “down.” The new versions are also much smaller than the palm-sized prototype — about the size of a thumbnail. The researchers want to miniaturize them even more, too.
Using metamaterial to create the sensor with potential for medical applications
The researchers say the sensor is a metamaterial. Instead of the material used giving the sensor its special properties, the structure does.
“Our sensor consists purely of silicone and contains neither toxic heavy metals nor any rare earths, as conventional electronic sensors do,” Serra-Garcia says.
The sensor features dozens of identical or similarly structured plates connected to one another by tiny bars. These connecting bars act as springs. The research team used computer modeling and algorithms to develop the design and attach them to one another. Springs in the sensor determine whether a sound source triggers the energy release.
Among the potential applications for battery-free sensors are medical devices. The team specifically singled out cochlear implants for hearing loss. Such implants require a permanent power supply for signal processing from batteries. With a power supply located behind the ear, they can’t connect to large battery packs because of the lack of space. Wearers have to replace the batteries every 12 hours.
Additionally, the team sees the potential for the technology in continuous eye pressure monitoring, due to the lack of space in the eye itself for a device with a battery.
“There’s a great deal of interest in zero-energy sensors in industry, too,” Serra-Garcia said.
Serra-Garcia and his team at AMOLF, a public research institute in the Netherlands, are working to refine the sensors. They hope to launch a solid prototype by 2027.
“If we haven’t managed to attract anyone’s interest by then, we might found our own start-up,” he said.
Filed Under: Batteries