Researchers have created heart monitoring sensors that conform to the skin, are comfortable, and can be worn while people are moving. The sensors have performance comparable to sensors already on the market, and the new technology can be made using existing manufacturing processes.

“Medical patients are often asked to wear devices to record electrocardiogram (ECG) data that can be used to diagnose an illness, monitor the progression of recovery or disease, and so on,” says Kirstie Queener, first author of a paper on the work. “However, this process can take hours – or even days – and the existing technology poses some challenges. For example, existing sensors must be held in place using an adhesive that can irritate patient skin. Existing technologies also require gel to be applied to the patient so the electrode can get a clear signal, and the signal degrades as the gel dries.

“Our goal was to create a polymer electrode that is comfortable to wear, adheres to the patient’s skin, and can get an accurate reading without using gels or adhesives,” says Queener, who is a Ph.D. candidate in the Lampe Joint Department of Biomedical Engineering at North Carolina State University and the University of North Carolina at Chapel Hill.

For this project, the researchers worked with a polymer called POMaC, which has all the desirable mechanical properties needed for this application but lacked the electrical properties necessary to make it a functional electrode. To resolve this, the researchers incorporated two additional elements into the POMaC – a conductive polymer and a surfactant – while still in liquid form.

This mixture can then be applied via screen printing, or cast in molds, depending on the shape of the electrode needed for a given application. The material can then be “cured,” or heated, until it becomes an elastic solid.

“The final product is a conductive matrix, which makes it highly functional as an electrode that can pick up ECG signals,” says Queener. “It’s also shaped to our specifications, is adhesive enough to stick to the skin, can bear the weight of the wires necessary to transmit readings to the device recording the ECG, and can be peeled off later without yanking your hair out.”

In proof-of-concept testing, the new electrodes performed comparably to existing ECG monitoring technologies.

“We actually tested the new electrodes using two different technologies: a commercial ECG device like the ones used in many health care settings or for long-term monitoring at home; and an experimental patch we’re developing that transmits ECG data wirelessly,” says Michael Daniele, corresponding author of the paper. “It worked well with both devices, which underscores the versatility – and utility – of these electrodes.” Daniele is a professor of electrical and computer engineering at NC State and a professor in the Lampe Joint Department of Biomedical Engineering at NC State and UNC.

“We developed this engineered electrode material for use in ECG applications,” Queener says. “But the nature of the material means it could also be used in a variety of other technologies.”

“We’re currently exploring a range of additional biomonitoring applications and are in the process of preserving our intellectual property rights on the material,” says Daniele. “The electrodes are made from conventional materials using scalable manufacturing techniques, so we’re optimistic that this will be a practical, cost-effective means of improving health monitoring technologies.

“We’d love to work with private sector partners to explore potential applications and opportunities to scale up production of this electrode material.”

The paper, “Self-Adhesive Conductive Elastomers for Gel-Free Biopotential Recording,” is published open access in the journal Advanced Electronic Materials. The paper was co-authored by Alec Brewer, a Ph.D. student at NC State; Alper Bozkurt, the McPherson Family Distinguished Professor in Engineering Entrepreneurship in the Department of Electrical and Computer Engineering at NC State; Koji Sode, the William R. Kenan Jr. Distinguished Professor in the Lampe Joint Department of Biomedical Engineering; He Sun and Jack Twiddy, postdoctoral researchers in the Lampe Joint Department; and Vladimir Pozdin, an assistant professor of electrical engineering at Florida International University.

This work was done with support from the National Science Foundation under grants 2231012 and 2037328; the National Institutes of Health under grant 1R01CA297854-01; and the National Institute on Disability, Independent Living, and Rehabilitation Research under grant 90REGE0017-01. The work was also supported by NC State’s Center for Advanced Self-Powered Systems of Integrated Sensors and Technologies (ASSIST), which was created with funding from NSF under grant 1160483.