Where Art Meets Science: Kirigami For Stretchable Electronics

Kirigami, a variation on the more well-known origami in which paper is both folded and cut, allows the creation of remarkably intricate works of art. Now, however, scientists are putting the technique to use for more than just aesthetics. They’ve discovered that cutting a conductive nanocomposite in a similar fashion allows it to stretch up to 370% without loss of electrical performance. This may be just the breakthrough needed to develop practical and functional wearable electronics.

Kirigami: this simple exmaple of kirigami demonstrates the way cuts and folds can alter the physical properties of a 2D material. Image by Bharath Kishore.Kirigami: this simple exmaple of kirigami demonstrates the way cuts and folds can alter the physical properties of a 2D material. Image by Bharath Kishore.

Without knowing it, we probably all practiced the art of kirigami as children – the most common example is the creation of paper snowflakes. Serious practitioners, in contrast, can produce astoundingly detailed pieces, with cuts so fine it’s difficult to fathom the steadiness of the hands needed to create them. The scientists at the University of Michigan involved in this research went one step further though, removing human hands from the equation and taking advantage of the nanofabrication tools at their disposal. Employing photolithography, a technique in widespread use in the electronics industry, they were able to produce patterns on the order of hundreds of microns – approximately the diameter of a human hair. One of the primary advantages of photolithography, and the reason it is so prized in the fabrication of integrated circuits and the like, is the ease with which it can be scaled up to produce millions of patterns in parallel. The ability to scale up is crucial as often laboratory prototypes of microscale electronics can be completely impractical or prohibitively expensive to commercialize.

With the means to create ultra-small repeating patterns of cuts in hand, the scientists then set about selecting a nanocomposite that was both conductive enough to perform well in electronic devices and uniform over large areas. They settled on everyone’s favorite material-of-the-moment, graphene. More specifically, multiple layers of graphene oxide, a material with many of the excellent electronic properties of graphene, but that is easier and less costly to produce over large areas.

Flexible electronics: this foldable keyoard is just one example of a practical application for stretchable electronic materials. Image by Geographer for Micro Innovations.Flexible electronics: this foldable keyoard is just one example of a practical application for stretchable electronic materials. Image by Geographer for Micro Innovations.

The results were astounding. The graphene-based material in its unaltered state was able to withstand a strain of just 4% before failure. In contrast, nanocomposite structures with even a very simple pattern of cut lines could stretch by 70% without mechanical failure even after cycling a thousand times. The obvious practical application of such research is the development of flexible electrodes for stretchable electronics – imagine a solar panel that you can wear like a headband to power your iPod while you run, for just one example. To create electrodes with this strategy, the team turned to an even simpler material, tracing paper. They infiltrated the paper with carbon nanotubes to produce a highly conductive network. Their theory was that even upon stretching, the nanotubes would retain sufficient contact to maintain high electrical conductivity. The experiment was a complete success with the paper able to stretch by a whopping 290% without significant loss of electrical properties.

Rapid advances in the field of stretchable and flexible electronics, organic electronic materials, and low profile power supplies means that the integration of electronic devices further into our everyday life is inevitable. We are already tethered to our smartphones, but soon we will also be finding devices built right into our clothing, our windows, our coffee mugs – everywhere. The internet of things is no longer a concept, but a reality, and it is fascinating that an ancient art like Japanese paper cutting is finding new life in a thoroughly modern application.

Via Nature Materials.