A pliable, multi-purpose acoustic sensor has been developed by researchers at the University of Colorado Boulder (UC Boulder) and Northwestern University (NU) that can be worn like a Band-Aid on the skin to monitor the heart and recognize spoken words. The researchers believe that the device could one day be used to monitor a wide range of bodily functions, while also allowing the wearer to control robots or drones via voice command.

Weighing in at under one-hundredth of an ounce (3 g) and able to continually monitor physiological data via sound signals from the body, the sensor can be attached to almost any body surface.

"This device has a very low mass density and can be used for cardiovascular monitoring, speech recognition and human-machine interfaces in daily life," said CU Boulder Assistant Professor Jae-Woong Jeong. "It is very comfortable and convenient – you can think of it as a tiny, wearable stethoscope."

Designed to pick up the acoustic signatures of the various mechanical waves that continuously move through the human body due to normal activities such as the opening and closing of heart valves, the reverberations of the vocal cords, or even peristaltic movement in the gastrointestinal tract, the device is also able to use its inbuilt electrodes to monitor electrocardiogram (ECG) and electromyogram (EMG) signals from the heart.

Currently the prototype is hard-wired for data acquisition tests, but the researchers state that it could be readily adapted to deliver wireless signals via an appropriate radio frequency link, which would allow it to be used in remote areas or loud situations. This could see it used, for example, on the battlefield to transmit low-noise cardiac signals to distant medical facilities or high-quality speech commands to operate remote-control weapons or vehicles.

As part of proving the concept of voice commands via vibration capture, the researchers used a test subject to control a Pac-Man game by modulating their vocal cords for the words "up," "down," "left", and "right."

Other acoustic devices have been developed to monitor the heart and gastrointestinal tract. But instruments like the MIT ingestible unit only monitor for as long as they travel through the body, while other systems such as Empa's wearable ECG monitor are just too bulky to be worn in complete comfort.

"While other skin electronics devices have been developed by researchers, what has not been demonstrated before is the mechanical-acoustic coupling of our device to the body through the skin," said Jeong. "Our goal is to make this device practical enough to use in our daily lives."

The (very) short video below shows a researcher demonstrating attaching the prototype.

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