Researchers identify optimal placement of armband electrodes
Researchers have taken a step forward in developing a new armband that can track the electrical activity of the heart without the use of bulky wires or gels that stick to the skin.
Specifically, the researchers determined the ideal placement of the three electrodes in the armband design, and how tight the design would need to be to best detect electrical signals from the heart.
The discovery is the latest in a multi-institutional effort to develop an armband that measures electrocardiogram, or ECG, values that can be used to track heart rate through ECG lead wires. The researchers eventually envisioned a device that could wear an arm cuff throughout the day. Energy from body heat or exercise will power the device.
"This study is the first step in identifying all the component parts of the armband to make it a reality," said lead author Braden M. Li, a doctoral student at NC State's Wilson School of Textiles. "We identified the ideal electrode locations to collect the heart. signal and found the effect of armband pressure on ECG quality."
The researchers studied electrode placement in various locations on the volunteers' left upper arm in order to determine the optimal placement of the three electrodes used to track the electrical activity of the heart. They determined the best placement of electrodes from 50 different combinations.
The electrodes are often "wet," or used with a gel substance in ECG devices, so researchers are designing a device that uses dry electrodes, which have the potential to be part of a wearable device that can be used for extended periods of time. They also measured pressure and heart signals on three different sizes of wristbands to see how tightly they were worn.
"If there isn't enough pressure on the wristband, then we won't be able to get the same quality of data that we need," said lead author Jesse S. Jur, professor of textile engineering, chemistry and science.
To prototype the armband, the researchers printed electrodes onto a plastic film using a screen-printing method that has been discovered in Jur's lab. They then heated and pressed the electrodes onto polyester and spandex fabrics.
"Screen printing is a very traditional process for textile manufacturing," said M.Li. "We hope to find a way that can be easily translated into a textile manufacturing process."
The work is part of a multi-institutional research effort funded by the National Science Foundation and conducted by the Advanced Self-Powered Systems Center for Integrated Sensors and Technologies (ASSIST) based on engineering research. Researchers at the center are working to develop wearable devices that can be powered by the body's own thermal or mechanical energy. For the armbands, they're looking at how to get the best heart signal with the least amount of energy.
The researchers designed the armband with three electrodes instead of 12 so that the wearer could power it. While increasing the number of wires, which capture the heart's electrical signals more precisely, they're working on a design that anyone of any size can easily wear.
"Part of the goal of the ASSIST center is to design self-powered wearable electronics," Jur said. "We've been balancing the power required for sensor systems, data processing, and communications to match the energy you're likely to get from your body."
The research was published in the IEEE Sensors Journal. The National Science Foundation funded this work.