Breathable Electronic Material Makes Wearables More Comfortable and DurableMay 04, 2020 by Luke James
Engineers at North Carolina State University (NC State) have developed a breathable electronic material that is stretchable and ultrathin, allowing gas to permeate through it.
It is thought that the team’s development could make biomedical or wearable technologies more comfortable for users by allowing sweat and other organic compounds to evaporate through it, away from the skin.
The team’s research and findings were published on April 29 in the journal ACS Nano. The research describes how the material was created and how its electrode exhibits excellent stability with the presence of sweat and after longterm wear.
A ‘Big Advance’ Over Other Stretchable Electronics
Yong Zhu, a co-corresponding author of a paper on the work, said that the material’s gas permeability is a “big advance over earlier stretchable electronics,” and went on to add that what’s just as significant is the material’s production method---a “simple process that would be easy to scale up.”
According to NC State, the researchers used what’s known as the ‘breath figure’ method—a method used to form porous films from water droplet templates—to create a stretchable polymer film featuring an even distribution of holes. Breath figures are formed by water microdroplets condensed on a cool surface from warm, humid air like breath. The film is then coated by dipping it in a solution that contains silver nanowires (AgNWs). Finally, the material is heat-pressed to seal the nanowires.
The resulting film has a transmittance of 61%, the sheet resistance of 7.3 Ω/sq, and water vapor permeability of 23 mg cm−2 h−1, “…an excellent combination of electric conductivity, optical transmittance, and water-vapor permeability,” Zhu said in a statement. “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 a film that is extremely thin—only a few micrometers thick. The NC State team says that this allows for better contact with the skin, resulting in a better signal-to-noise ratio for more accurate reading and low skin-electrode impedance.
A sleeve developed by researchers that incorporates electronic fabric. Image credited to Yong Zhu, NC University
Demonstrating the Material’s Potential
To demonstrate the material’s potential for use in wearable devices, the researchers developed two prototypes—skin-mountable biopotential sensing for healthcare and textile-integrated touch sensing for human-machine interfaces.
The first prototype (for biopotential sensing) consisted of skin-mountable, dry electrodes for use as electrophysiologic sensors that could be used in the healthcare field for electrocardiography (ECG) and electromyography (EMG).
Extending the Endurance of Wearable Sensors
The second prototype (textile-integrated touch sensing) was gas permeable and demonstrated the material’s potential for touch sensing for human-machine interfaces. For proof of concept, the researchers used a wearables textile sleeve integrated with porous electrodes to play computer games.
“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.”
The significance of gas permeability may be great for the purpose of improving comfort, but its importance goes beyond this by preventing skin irritation in those wearing it.