Prof. Sungwon Lee shows his hand with the tiny micro supercapacitor stuck on the skin near his wrist. (Credit: DGIST)

Researchers have fabricated tiny energy storage devices that can effectively power flexible and wearable skin sensors along with other electronic devices, paving the way toward remote medical monitoring and diagnoses and wearable devices.

A key for success is spraying a specific amount of graphene ink onto flexible substrates at a specific angle and temperature. Graphene is a promising material for improving their energy storage, as graphene electrodes are highly porous and so provide a larger surface area for the necessary electrostatic reactions to occur. They sprayed 10 ml of graphene ink at a 45° angle and 80 °C temperature onto a flexible substrate. This led to the formation of porous, multilayered electrodes.

The micro supercapacitor is 23 μm thin and retains its mechanical stability after 10,000 bends. It can store around 8.4 μF of charge per square centimeter and has a power density of about 1.13 kW per kg. The team demonstrated that it could be used in wearable devices that adhere to the skin.

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