Wearable Acoustic Sensor Monitors Heart Health, Detects Speech Signals

A tiny, wearable acoustic sensor developed by researchers can be used to monitor heart health and recognize spoken words. (Credit: Northwestern University, University of Colorado Boulder)

Researchers have developed a small, soft, and wearable acoustic sensor that can measure vibrations in the human body, monitor the heart health, and detect spoken words. The new electronic device was developed by scientists from the University of Colorado Boulder and Northwestern University.

Jae-Woong Jeong, CU Boulder Assistant Professor and one of three lead study authors, explained that the new, stretchable device captures the body’s physiological sound signals and possesses physical properties that are well-matched with human skin. It can be placed on almost any surface of the body. The sensor looks like a small band-aid and can collect continuous physiological data. It weighs less than one-hundredth of an ounce.

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

Jae-Woong Jeong, Department of Electrical, Computer and Energy Engineering

A paper on this topic was reported in Science Advances, a sister journal of Science. Professors Yonggang Huang and John Rogers of Northwestern are the other two co-corresponding authors of the study.

Listening in on the body

“The thin, soft, skin-like characteristics of these advanced wearable devices provide unique capabilities for ‘listening in’ to the intrinsic sounds of vital organs of the body, including the lungs and heart, with important consequences in continuous monitoring of physiological health,” said Rogers, the Simpson Querrey Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery. He is also the director of Center for Bio-Integrated Electronics of Northwestern University.

According to research team, the sensor can detect mechanical waves propagating through fluids and tissues in the human body, because of the natural physiological activity. This exposes the typical acoustical signatures of individual events that include the vibrations of the vocal cords, opening and closing of heart valves, and movements in gastrointestinal tracts.

Also, the device can integrate electrodes that can record electromyogram (EMG) signals, which calculate the electrical activity of muscles during contraction and at rest as well as electrocardiogram (ECG) signals, which calculate the heart’s electrical activity.

Jeong informed that though the sensor device was connected to an exterior data acquisition system for the tests, it can be easily transformed into a wireless device. Such devices can be useful in remote, noisy places such as battlefields, and produce quiet and high-quality speech or cardiology signals that can be read in real time at remotely located 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.

Jae-Woong Jeong, Department of Electrical, Computer and Energy Engineering

Talking to machines

Jeong added that military personnel or civilians could also use vocal cord vibration signals to control vehicles, drones, or robots. In addition, the sensor’s speech recognition capabilities have implications for enhancing communication for patients suffering from speech impairments.

As part of the project, the device was used to measure ECG activity and cardiac acoustic responses, including the detection of heart murmurs, in a group of elderly volunteers at Camp Lowell Cardiology. Camp Lowell Cardiology is a private medical clinic located in Tucson, Arizona which teamed up with the University of Arizona, a project partner. Jeong explained that the team was also able to identify the acoustical signals of blood clots in a related laboratory experiment.

Assistant Professor Jianliang Xiao; doctoral student Raza Qazi of electrical engineering; and doctoral student Zhanan Zou of mechanical engineering were other co-authors of the Science Advances paper.

The flexible, sticky polymer covering the small sensor is stretchable enough to follow the deformation of skin, informed the first study author Yuhao Liu, who works at Lam Research, headquartered in Fremont, California and earned his doctorate at the University of Illinois-Urbana Champaign. The sensor includes a small commercial accelerometer to determine the vibration of the body acoustics and permits the evaporation of human sweat.

Additionally, the team demonstrated that when the device is placed on a throat, the vocal cord vibrations that were collected can be used to control other machines, including video games. As part of the research, a test subject used vocal cord vibrations for the words “left”, “right” and “up” and “down.” and was able to control a Pac-Man game.  

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. Our goal is to make this device practical enough to use in our daily lives.

Jae-Woong Jeong, Department of Electrical, Computer and Energy Engineering

The Eulji University College of Medicine in Korea was also a part of the study.

Comments

  1. Elaine Buck Elaine Buck United Kingdom says:

    what other applications can this sensor be used for?  can it be used for condition monitoring in testing/verification for other sectors - like automotive? or O&G?

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