Researchers at Osaka Prefecture University in Japan developed a wearable and wireless electrocardiogram monitor that employs kirigami, an ancient art of folding and cutting paper, to ensure better skin contact, stretchability, and breathability. The kirigami design lets the researchers minimize the size of their sensor and the technology allows for long-term vitals measurements with wireless data transmission to a smartphone app. Consisting of a film made of polyethylene terephthalate that the researchers printed with silver electrodes, the sensor includes ingenious cuts that allow it to better conform to the ever-undulating surface of the body.
Wearables typically stick to the skin, but this creates challenges. Our skin sweats, and applying a non-breathable film to it is a recipe for a sweaty and uncomfortable mess. Moreover, our bodies include various lumps and bumps that are difficult for a simple sheet to conform and adhere to, particularly for slightly stiff materials such as polyethylene terephthalate (PET).
To address these issues, the Japanese researchers turned to the ancient art of kirigami, which shares similarities with its sister practice of origami. Origami typically involves folding paper to create interesting shapes and structures, whereas kirigami also involves introducing cuts to a material, expanding the range of possibilities.
The Osaka Prefecture University team introduced slits into the PET film, providing the manifold benefits of increased flexibility, improved conformability with the surface of the body, and a substantial reduction in size of the sensor. Another benefit is the breathability of the porous membrane, which allows sweat to escape from the skin.
“In terms of wearability, by applying kirigami structure in a PET film, due to PET deformation and bending, the film can be stretchable, so that the film can follow skin and body movement like a bandage,” said Kuniharu Takei, a researcher involved in the study. “In addition, since kirigami structure has physical holes in a PET film, skin can be easily breathed through the holes [sic].”
So far, the kirigami sensor has shown promise as an ECG monitor, enabling measurements during a range of activities including vigorous exercise. However, the researchers hope to expand the capabilities of the device by introducing additional sensors that can measure various physiological parameters through skin contact.
Study in Applied Physics Reviews: Wireless, minimized, stretchable, and breathable electrocardiogram sensor system