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System Integration

Breathable electronics could lead to functional long-term wearable technology

North Carolina State University engineering researchers have created ultrathin, stretchable electronic material that is gas permeable and is designed specifically for use in biomedical or long-term wearable technologies. See video.

By Matt Shipman May 5, 2020
This sleeve incorporates the new electronic material, allowing it to function as a video game controller. Courtesy: North Carolina State University

North Carolina State University engineering researchers have created ultrathin, stretchable electronic material that is gas permeable, allowing the material to “breathe.” The material was designed specifically for use in biomedical or wearable technologies, since the gas permeability allows sweat and volatile organic compounds to evaporate away from the skin, making it more comfortable for users – especially for long-term wear.

“The gas permeability is the big advance over earlier stretchable electronics,” said Yong Zhu, co-corresponding author of a paper on the work and a professor of mechanical and aerospace engineering at North Carolina State University. “But the method we used for creating the material is also important because it’s a simple process that would be easy to scale up.”

The researchers used a technique called the breath figure method to create a stretchable polymer film featuring an even distribution of holes. The film is coated by dipping it in a solution that contains silver nanowires. The researchers then heat-press the material to seal the nanowires in place.

“The resulting film shows an excellent combination of electric conductivity, optical transmittance and water-vapor permeability,” Zhu said. “And because the silver nanowires are embedded just below the surface of the polymer, the material also exhibits excellent stability in the presence of sweat and after long-term wear.”

“The end result is extremely thin – only a few micrometers thick,” said Shanshan Yao, co-author of the paper and a former postdoctoral researcher at NC State who is now on faculty at Stony Brook University. “This allows for better contact with the skin, giving the electronics a better signal-to-noise ratio. And gas permeability of wearable electronics is important for more than just comfort,” Yao said. “If a wearable device is not gas permeable, it can also cause skin irritation.”

To demonstrate the material’s potential for use in wearable electronics, the researchers developed and tested prototypes for two representative applications.

The first prototype consisted of skin-mountable, dry electrodes for use as electrophysiologic sensors. These have multiple potential applications, such as measuring electrocardiography (ECG) and electromyography (EMG) signals.

“These sensors were able to record signals with excellent quality, on par with commercially available electrodes,” Zhu said.

The second prototype demonstrated textile-integrated touch sensing for human-machine interfaces. The authors used a wearable textile sleeve integrated with the porous electrodes to play computer games such as Tetris. See video courtesy of NC State below:

Courtesy: North Carolina State University

“If we want to develop wearable sensors or user interfaces that can be worn for a significant period of time, we need gas-permeable electronic materials,” Zhu said. “So this is a significant step forward.”

– Edited by Chris Vavra, associate editor, Control Engineering, CFE Media and Technology, cvavra@cfemedia.com.


Matt Shipman
Author Bio: Matt Shipman, research communications lead, North Carolina State University