Tiny gadget captures every whoosh, thump and gurgle inside the body

It looks like a small Band-Aid, but it’s powerful enough to allow a doctor to monitor the heart rate of a patient remotely or to enable someone to control a robot with voice commands.

The “tiny, wearable stethoscope” was created by Jae-Woong Jeong, assistant professor of electrical, computer and energy engineering, along with colleagues from Northwestern University.

The soft, stretchable acoustic sensor captures physiological sound signals from the body, has physical properties well-matched with human skin and can be mounted on nearly any surface of the body, Jeong said. The sensor weighs less than one-hundredth of an ounce and can gather continuous physiological data.

“This device has a very low mass density and can be used for cardiovascular monitoring, speech recognition and human-machine interfaces in daily life,” Jeong said.

The new device can pick up mechanical waves that propagate through tissues and fluids in the human body due to natural physiological activity, revealing characteristic acoustical signatures of individual events. They include the opening and closing of heart valves, vibrations of the vocal cords and even movements in gastrointestinal tracts.

The sensor can also integrate electrodes that can record electrocardiogram signals that measure the electrical activity of the heart as well electromyogram signals that measure the electrical activity of muscles at rest and during contraction.

Military personnel or civilians could use vocal cord vibration signals to control robots, vehicles or drones. The speech recognition capabilities of the sensor might also improve communication for people with speech impairments, Jeong said.

As part of the study, the team used the device to measure cardiac acoustic responses and electrocardiogram activity—including the detection of heart murmurs—in a group of elderly volunteers at Camp Lowell Cardiology, a private medical clinic in Tucson, Arizona. The researchers also were able to detect the acoustical signals of blood clots in a related lab experiment, Jeong said.

The researchers showed that vocal cord vibrations gathered when the device is on a user’s throat can be used to control video games and other machines. As part of the study, a test subject was able to control a Pac-Man game using vocal cord vibrations for the words “up,” “down,” “left” and “right.”

“While other skin electronic 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,” Jeong said. “Our goal is to make this device practical enough to use in our daily lives.”

A paper on the subject was published Nov.16 in Science Advances, a sister journal of Science. The other two co-corresponding authors are Professors Yonggang Huang and John Rogers of Northwestern University. Additional partners on the project include the Eulji University College of Medicine in Korea and the University of Arizona.