Truly wearable displays are self-powered and washable

When we think about clothes, they are usually formed with textiles and have to be both wearable and washable for daily use; however, smart clothing has had a problem with its power sources and moisture permeability, which causes the devices to malfunction.

This problem has now been overcome by researchers from the Korea Advanced Institute of Science and Technology (KAIST), who developed a textile-based wearable display module technology that is washable and does not require an external power source. The research was led by Professor Kyung Cheol Choi, whose team fabricated their wearing display modules on real textiles that integrated polymer solar cells (PSCs) with organic light-emitting diodes (OLEDs).

PSCs have been one of the most promising candidates for a next-generation power source, especially for wearable and optoelectronic applications because they can provide stable power without an external power source, while OLEDs can be driven with milliwatts. However, both are very vulnerable to external moisture and oxygen and require an encapsulation barrier in order to maintain their reliability. The conventional encapsulation barrier is sufficient for normal environments; however, it loses its characteristics in aqueous environments, such as water. It thus limits the commercialisation of wearing displays that must operate even on rainy days or after washing.

To tackle this issue, the KAIST team employed a washable encapsulation barrier that can protect the device without losing its characteristics after washing through atomic layer deposition (ALD) and spin coating. With this encapsulation technology, the team confirmed that textile-based wearable display modules including PSCs and OLEDs, as well as the proposed encapsulation barrier, exhibited little change in characteristics even after 20 washes with 10-minute cycles. The encapsulated device operated stably and reliably, with a low curvature radius of 3 mm, and the technology exhibited no deterioration in properties over 30 days even after being subjected to both bending stress and washing.

Since it uses a less stressful textile, compared to conventional wearable electronic devices that use traditional plastic substrates, the technology can accelerate the commercialisation of wearing electronic devices. Importantly, the wearable electronic device saves energy through its self-powered system. It has been described in the journal Energy and Environmental Science.

“I could say that this research realised 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,” Prof Choi said. “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.”

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