Stretchy power! Wearables get flexible energy storage in new breakthrough

Photographs of the MSC array integrated with two LEDs circuit POSTECH

The growing popularity of wearable technology has highlighted a critical need for power sources that can match the flexibility and movement of these innovative devices. Researchers have made a significant leap forward in addressing this challenge with the development of a small-scale energy storage device capable of stretching, twisting, folding, and wrinkling. This exciting advancement, published in the journal npj Flexible Electronics, paves the way for truly adaptable and comfortable wearables.

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Photographs of the MSC array integrated with two LEDs circuits under various mechanical deformations. Credits: POSTECH

The challenge: Brittle electrodes vs. deformable needs

The rise of wearables, from fitness trackers to smart clothing, has necessitated a shift in how we store energy. Traditional batteries, while effective, often lack the flexibility required for these soft electronic devices. Micro supercapacitors (MSCs) have emerged as a promising alternative due to their high power density, rapid charging capabilities, and long lifespan. However, a major hurdle remained: the fabrication of electrodes.

Conventionally, electrodes are made from brittle materials like gold, which significantly limit the device’s ability to deform without compromising performance. Conversely, while eutectic gallium-indium liquid metal (EGaIn) offers superior conductivity and deformability, its high surface tension makes fine patterning, a crucial step in creating efficient electrodes, extremely difficult.

Fabrication process for deformable micro-supercapacitors. Credits: POSTECH

A laser-sharp solution: Patterning the way for flexible power

The research team, led by Professor Jin Kon Kim and Dr. Keon-Woo Kim from Pohang University of Science and Technology (POSTECH) in collaboration with Dr. Chanwoo Yang and Researcher Seong Ju Park from the Korea Institute of Industrial Technology (KITECH), devised a solution using laser technology. Their innovation lies in the successful laser patterning of both EGaIn and graphene, an active material, on a stretchable substrate made of polystyrene-block-poly(ethylene-co-butylene)-block-polystyrene copolymer (SEBS).

This laser ablation technique offered several advantages. Notably, it ensured the underlying SEBS substrate remained undamaged, preserving the device’s overall flexibility. Additionally, tests revealed that the areal capacitance, a measure of the device’s energy storage capacity per unit area, remained unchanged even after undergoing 1,000 stretching cycles. Furthermore, the researchers observed stable operation under various mechanical deformations, including stretching, folding, twisting, and wrinkling.

Implications for wearable tech

This breakthrough holds immense potential for the future of wearable technology. As Professor Jin Kon Kim aptly stated, “The use of laser-patterned liquid metal electrodes represents a significant step forward in the development of truly deformable energy storage solutions.” This innovation paves the way for the creation of comfortable and adaptable wearables that can seamlessly integrate into our dynamic lifestyles.