The designs of kirigami – a variant of origami which utilizes paper cutting in addition to folding – are being used in ways that may revolutionize flexible-film electronics.

At Toyohashi University of Technology in Japan, a research team at the Electronics-Inspired Interdisciplinary Research Institute (EIIRIS) has developed a kirigami-based, ultra-stretchable bioprobe. Its design reduces the force induced on organs, enabling minimally-invasive biological signal recording.

A kirigami-based, ultrastretchable bioprobe placed over biological tissue. Image credit: Toyohashi University of Technology.A kirigami-based, ultrastretchable bioprobe placed over biological tissue. Image credit: Toyohashi University of Technology.Properties like high stretchability and deformability widen the range of applications for flexible-film electronics, such as sensors, actuators and energy harvesters. This is especially relevant for three-dimensional, soft biological samples such as organs and tissues with large and rapid changes in their surface area and volume – for example, a beating heart. Conventional elastomer-based stretchable devices, however, require a large strain-force to be stretched – making them invasive and unsafe for soft biological sample applications.

That’s where the kirigami design comes in, as Ph.D. candidate Yusuke Morikawa explains. “The remarkable feature of kirigami is that rigid and unstretchable materials can be rendered more stretchable,” he says. “The stretching mechanism is based on an out-of-plane bending of the thin film rather than stretching of the material. Therefore, the strain-stress characteristic is extremely low compared to that of elastomer-based stretchable devices.” Morikawa is first author of a paper on the research, published in the journal Advanced Healthcare Materials.

The research team’s leader, Prof. Takeshi Kawano, says that the idea for the approach came when he saw his son playing with origami and kirigami. He noted that the kirigami designs imparted high stretchability to the paper being used. “Our preliminary studies on kirigami-based parylene films by microelectromechanical systems technology exhibited high stretchability of 1,100 percent,” he says. The stretchability of those parylene films are illustrated in the video.

The kirigami-based bioprobes are capable of recording biological signals from the cortical surface and beating heart of a mouse, adds Kawano. The devices may also find applications in probing tissues and organs that exhibit time-dependent changes in surface and volume due to growth or disease – and ultimately lead to a new understanding of the mechanisms governing growth and diseases like Alzheimer's.