Ultrastretchable and Deformable Electronic Bioprobes

A research team in the Department of Electrical and Electronic Information Engineering and the Electronics-Inspired Interdisciplinary Research Institute (EIIRIS) at Toyohashi University of Technology has developed an ultra-stretchable bioprobe that can greatly improve flexible film electronics. They use a technique that enables one to follow the shape of spherical and large deformable biological samples such as heart and brain tissues. In addition, its low strain-force characteristic reduces the force induced on organs, thereby enabling minimally invasive biological signal recording.

What do you call this technique they are implementing?

Kirigami-based bioprobes

High stretchability and deformability are potential properties to boost the applications of flexible film electronics including actuators, sensors and energy harvesters. Particularly, they have significant potential for applications related to 3D soft biological samples such as tissues and organs that display large and fast changes in their surface area and volume (for instance - a beating heart). However, conventional elastomer-based stretchable devices need a large strain-force to stretch it that arises from an intrinsic material feature.

This makes it difficult to follow the deformation of soft biological tissues, thus stopping natural deformation and growth. For device applications relating to soft biological samples, it is very vital to decrease the strain-force characteristic of the stretchable devices to attain low invasiveness and safe measurements.

A research team in the Department of Electrical and Electronic Information Engineering and the EIIRIS at Toyohashi University of Technology has created an ultra-stretchable bioprobe employing Kirigami designs.

Fabricated 'Kirigami' parylene film. Credit: Toyohashi University Of Technology.

Although the film is composed of biocompatible parylene for the device substrate and metal layers of platinum (Pt)/titanium (Ti), which are unstretchable materials, the film shows a high stretchability by patterning slits as a “Kirigami” design.

"The remarkable feature of Kirigami is that rigid and unstretchable materials can be rendered more stretchable compared to other elastomer-based stretchable materials. 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.", explains the first author of the article, Ph.D. candidate Yusuke Morikawa.


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