Building Technologies

A sound replacement for sensor batteries

10 April 2024
A prototype of the sound-sensitive sensor which requires no external power source and is activated by sound waves produced by specific noises, Source: Astrid Robertsson/ETH Zürich

An alternative to the batteries required to power sensors in infrastructure monitoring systems or medical wearables is being advanced by researchers from ETH Zürich (Switzerland), EPFL (Switzerland) and AMOLF (The Netherlands).

The battery-free sensor reacts to sound waves, such as particular spoken words, producing enough vibrational energy to power an electronic device. The silicon-based component is intended to reduce battery waste as it activates cochlear implants or other medical devices or monitors buildings through vibration sensing for faults.

The phononic sensor described in Advanced Functional Materials relies on passive speech recognition and is activated whenever a certain word is spoken, or a particular tone or noise is generated. These specific sound waves cause the silicon-based sensor to vibrate sufficiently so that it generates a tiny electrical pulse to switch on an electronic device.

Using computer modeling and algorithms, the structure of the metamaterial-based sensor was designed with a lattice of identical silicon resonators connected by tiny bars that function as springs. These springs determine whether a particular sound sets the sensor in motion.

A potential use case for these battery-​free sensors is in earthquake or building monitoring, as they could register when a building develops a crack according to the right sound or wave energy. In the medical realm, the devices might be used to power cochlear implants and eliminate the need for frequent battery replacement.

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