Wearable Sensor Smooths Path to Long-Term EKG, EMG Monitoring

Image credit: Yong Zhu. Click to enlarge.

Researchers from North Carolina State University have developed a new, wearable sensor that uses silver nanowires to monitor electrophysiological signals, such as electrocardiography (EKG) or electromyography (EMG). The new sensor is as accurate as the “wet electrode” sensors used in hospitals, but can be used for long-term monitoring and is more accurate than existing sensors when a patient is moving.

Long-term monitoring of electrophysiological signals can be used to track patient health or assist in medical research, and may also be used in the development of new powered prosthetics that respond to a patient’s muscular signals.

The silver nanowire sensors conform to a patient’s skin, creating close contact. Image credit: Yong Zhu. Click to enlarge.
The silver nanowire sensors conform to a patient’s skin, creating close contact. Image credit: Yong Zhu. Click to enlarge.

Electrophysiological sensors used in hospitals, such as EKGs, use wet electrodes that rely on an electrolytic gel between the sensor and the patient’s skin to improve the sensor’s ability to pick up the body’s electrical signals. However, this technology poses problems for long-term monitoring, because the gel dries up – irritating the patient’s skin and making the sensor less accurate.

The new nanowire sensor is comparable to the wet sensors in terms of signal quality, but is a “dry” electrode – it doesn’t use a gel layer, so doesn’t pose the same problems that wet sensors do.

“People have developed other dry electrodes in the past few years, and some have demonstrated the potential to rival the wet electrodes, but our new electrode has better signal quality than most – if not all – of the existing dry electrodes. It is more accurate,” says Dr. Yong Zhu, an associate professor of mechanical and aerospace engineering at NC State and senior author of a paper describing the work. “In addition, our electrode is mechanically robust, because the nanowires are inlaid in the polymer.”

The sensors stem from Zhu’s earlier work to create highly conductive and elastic conductors made from silver nanowires, and consist of one layer of nanowires in a stretchable polymer.

The new sensor is also more accurate than existing technologies at monitoring electrophysiological signals when a patient is in motion.

“The silver nanowire sensors conform to a patient’s skin, creating close contact,” Zhu says. “And, because the nanowires are so flexible, the sensor maintains that close contact even when the patient moves. The nanowires are also highly conductive, which is key to the high signal quality.”

The new sensors are also compatible with standard EKG- and EMG-reading devices.

“I think these sensors are essentially ready for use,” Zhu says “The raw materials of the sensor are comparable in cost to existing wet sensors, but we are still exploring ways of improving the manufacturing process to reduce the overall cost.”

An uncorrected proof of the paper, “Wearable Silver Nanowire Dry Electrodes for Electrophysiological Sensing,” was published online Jan. 14 in RSC Advances, immediately after acceptance. Lead author of the paper is Amanda Myers, a Ph.D. student at NC State. The paper was co-authored by Dr. Helen Huang, an associate professor in the joint biomedical engineering program at NC State and the University of North Carolina at Chapel Hill.

The work was supported by the National Science Foundation through the ASSIST Engineering Research Center at NC State, under grant number EEC-1160483.

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Note to Editors: The study abstract follows.

“Wearable Silver Nanowire Dry Electrodes for Electrophysiological Sensing”

Authors: Amanda C. Myers and Yong Zhu, North Carolina State University; He Huang, North Carolina State University and University of North Carolina at Chapel Hill

Published: Online Jan. 14, RSC Advances

DOI: 10.1039/C4RA15101A

Abstract: We present wearable dry electrodes made of silver nanowires for electrophysiological sensing such as electrocardiography and electromyography. The dry electrodes perform as well as the Ag/AgCl wet electrodes when the subject is resting and show less motion artifacts, as a result of the intimate, conformal contact with the skin. The nanowire electrodes show no signs of skin irritation, which is desirable for long-term health monitoring.

20 responses on “Wearable Sensor Smooths Path to Long-Term EKG, EMG Monitoring

  1. Anders Bjorlin says:

    Looks fantastic, when it is possible to have it for implementation we like to have it in our service BodyKom 3.0 ECG Remote Monitoring with our new low energy sensor with imbedded communication globally connected to BodyKom Server for high level diagnouse, patented method for transmission of bodyclose diagnose data. Best Regards Anders

  2. John Di Cristina says:

    I work for Maxim Integrated, a semiconductor company that makes integrated circuits and I am part of a group that is focused on the wearable medical market. My group is building proof of concept hardware designs that are complete systems such as a cardiac monitoring shirt that can use dry electrodes. I’d like to speak to someone to find out more about the electrodes and if NCSU is open to a collaboration where we can road test the electrodes in a real application.

    1. Suave Lobodzinski says:

      Hi, I just run into your post. Would be interested to find-out what type of wearable solution Maxim is working. I can share with you the state-of-the-art developments in the field of dry electrodes.
      Suave

  3. Mark Mastroianni says:

    My name is Mark Mastroianni and my focus is commercializing new innovative materials in both consumer electronics and medical device industries. It is clear from the article and comments above that you have discovered something very special. Let me know if there is a NC State industry relations team we can work with to reach a broad license/commercialize this material.

  4. Reid Wender says:

    Triad Semiconductor, http://www.triadsemi.com, and I develop EMG custom ICs. If you would like to discuss integrating multiple EMG sensor channels (Instr Amplifier, Gain, 50/60Hz Notch Filter, and high resolution ADC) into a single custom IC we would welcome the opportunity to talk. We are located in Winston-Salem and Raliegh NC.

  5. Sean Lorenz says:

    This is excellent! I am building a hospital band wearable demo and would to use this if possible. Any way to get access to a test electrode?

  6. Darren Starwynn says:

    This looks really valuable. Like other responders I am a researcher developing wearable devices. I would like to communicate with you about the type of pulse information it can pick up, and how to compare that to some pulse qualities I am researching. How could I get in touch with you to communicate about working with you or testing your electrode for this purpose?

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