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A Korea Advanced Institute of Science and Technology (KAIST) research team has developed a textile-based wearable display module technology that is washable and that does not require an external power source. The team fabricated its wearable display modules on real textiles that integrated polymer solar cells (PSCs) with OLEDs.
Both PSCs and OLEDs are vulnerable to external moisture and oxygen. Conventional encapsulation barriers, sufficient for normal environments, deteriorate in aqueous environments, limiting the use of PSCs and OLEDs for wearable displays that must operate even on rainy days or after washing.
To address this issue, the team used atomic layer deposition (ALD) and spin coating to create a washable encapsulation barrier that could protect the device from water using a silicon dioxide (SiO2)-polymer composite capping layer. It found that the chemical stability imparted by the reaction between SiO2 and aluminum oxide (Al2O3) could prevent the phase transitions that cause the barrier to degrade.
Schematic and photo of a washable, wearable display module. Courtesy of KAIST.
The researchers showed that textile-based wearable display modules that included PSCs and OLEDs and used the proposed encapsulation barrier preserved their physical and chemical properties, exhibiting little change in characteristics even after 20 washings with 10-min cycles. The encapsulated device operated stably with a low curvature radius of 3 mm and demonstrated high reliability. Further, the device showed no deterioration in properties over a 30-day period, even after being subjected to both bending stress and washing.
Wearable display module technology that is washable and self-powered. Courtesy of KAIST.
The technology uses a less stressful textile, compared to conventional wearable electronic devices that use traditional plastic substrates. Since PSCs can provide stable power without an external power source, use of the KAIST technology for a self-powered, wearable electronic device could save energy.
The researchers believe that their technology could accelerate the commercialization of wearable electronic devices. Professor Kyung Cheol Choi said, “I could say that this research realized a truly washable, wearable electronic module in the sense that it uses daily wearable textiles instead of the plastic used in conventional wearable electronic devices. Saving energy with PSCs, it can be self-powered, using nature-friendly solar energy, and washed. I believe that it has paved the way for a ‘true-meaning wearable display’ that can be formed on textile, beyond the attachable form of wearable technology.”
The research was published in Energy and Environmental Science (http://dx.doi.org/10.1039/c8ee03271h).
The washing process of the wearable display module. Courtesy of KAIST.READ MORE