Stretchable sensor placed on skin to help monitor heart, recognize speech

Credit: University of Colorado Boulder

University of Colorado Boulder (UC) and Northwestern University have developed an acoustic sensor to be placed on the skin that is able to measure the human body’s vibrations, allowing researchers to monitor the heart’s health and recognize speech.

The research, published in Science Advances on November 16, 2016, is authored by CU Boulder Assistant Professor Jae-Woong Jeong from the Department of Electrical, Computer and Energy Engineering, along with co-corresponding authors Professors Yonggang Huang and John Rogers of Northwestern.

According to Mr. Jeong, the physical properties of the sensor are well-matched with the human skin, and can be placed on almost any part of the body. The soft stretchable device, which resembles a Band-Aid, weighs less than a hundredth of an ounce, and is able to capture continuous physiological data signals from the body.

The tiny sensor is encapsulated by a sticky, flexible polymer which can stretch to follow skin deformation, said first author Yuhao Liu, adding that the device measured vibrations of the body acoustics using a commercial accelerometer, and allowed for evaporation of human sweat.

“The device has a very low mass density and can be used for cardiovascular monitoring, speech recognition and human-machine interfaces in daily life,” said Mr. Jeong. “It is very comfortable and convenient – you can think of it as a tiny, wearable stethoscope.”

Simpson Querrey Professor of Materials Science and Engineering John Rogers, who is also the director of Northwestern’s Center of Bio-Integrated Electronics, maintained that the skin-like characteristics of the wearable device provided unique means for ‘listening in’ to the sounds of the body’s vital organs such as the lungs and heart.

Further elaborating upon these sounds, the researchers claimed that the device could help reveal unique acoustical signatures of individual physiological events by sensing mechanical waves that propagate through tissues and fluids in the human body. These sounds are produced by natural physiological activity including opening and closing of heart valves, vibrations of the vocal cords and even movements in gastrointestinal tracts.

Apart from sensing sounds, the sensor can also integrate electrodes that record electrocardiogram (ECG) signals (which measure the heart’s electrical activity) and electromyogram (EMG) signals (that measure electrical activity of muscles at rest and during contraction).

Mr. Jeong added that even though the sensor was currently wired to an external data acquisition system, it could easily be converted into a wireless device, which could then be used in remote, noisy applications, including battlefields, to produce distinct silent cardiology or speech signals to be analyzed in real time at distant medical facilities.

“Using the data from these sensors, a doctor at a hospital far away from a patient would be able to make a fast, accurate diagnosis,” said Jeong.

He added that the vocal cord vibration signals, detected by the sensor, could be used by military personnel or civilians to control robots, vehicles or drones. “The speech recognition capabilities of the sensor also have implications for improving communication for people suffering from speech impairments,” he said.

In addition, researchers demonstrated that video games and other machines could also be controlled using data from vocal cord vibrations gathered from the device placed on one’s throat. 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 conducting the study, the team used the sensor to measure cardiac acoustic responses and ECG activity, including detection of heart murmurs, in a group of elderly volunteers at Camp Lowell Cardiology, a private medical clinic in Tucson, Arizona collaborating with project partner University of Arizona.

“The researchers were also able to detect the acoustical signals of blood clots in a related lab experiment,” said Jeong.

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

More information can be found at: University of Colorado Boulder.

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