Researchers have developed a sensor that utilizes energy from sound waves to control electronic devices. This could one day save millions of batteries.

The sensor works purely mechanically and doesn’t require an external energy source. It simply utilizes the vibrational energy contained in sound waves. Whenever a certain word is spoken or a particular tone or noise is generated, the sound waves emitted — and only these — cause the sensor to vibrate. This energy is then sufficient to generate a tiny electrical pulse that switches on an electronic device that has been switched off.

The prototype can distinguish between the spoken words “three” and “four.” Because the word “four” has more sound energy that resonates with the sensor compared to the word “three,” it causes the sensor to vibrate, whereas “three” does not. That means the word “four” could switch on a device or trigger further processes. Nothing would happen with “three.”

The sensor comprises dozens of identical or similarly structured plates that are connected to each other via tiny bars. These connecting bars act like springs. The researchers used computer modeling and algorithms to develop the special design of these micro-structured plates and work out how to attach them to each other. It is the springs that determine whether or not a particular sound source sets the sensor in motion. (Image credit: ETH Zurich)

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