The most fundamental component to all electronics is the conductor. Now, research engineers have developed a stretchable conductor they say could pave the way for flexible electronics.
Designing a conductor that stretches is a challenging feat. Current stretchable technology has low expansion rates and are not as effective as traditional conductors. An engineering team at the University of Michigan discovered that using a Japanese cutting and folding technique called kirigami allows the conductors to perform steadily once stretched.
"The kirigami method allows us to design the deformability of the conductive sheets, whereas before it was (a) very Edisonian process with a lot of misses and not a lot of hits," said engineering professor Nicholas Kotov.
It’s difficult to predict how a material will behave when it’s stretched significantly. But if the tears are strategically placed, the material can recover from those movements. Using the kirigami art technique, the team created an initial prototype made of tracing paper covered in carbon nanotubes. The simple layout featured cuts that made the conductor resemble a cheese grater.
A glowing plasma was created after the paper electrode was placed in a glass tube filled with argon. Electrons were set free and started bumping into the argon atoms as a result of the voltage. This reaction caused the atoms to emit light and according to Kotov, arrays of these electrodes could come in handy and control a stretchable plasma screen’s pixels.
In order to get an idea of how different design choices would affect the stretchable conductor, the team enlisted the help of a chemical engineering professor and her collaborators to perform computer simulations.
"At first, computer simulation gave us intuition on what kinds of behaviors were to be expected from different cut patterns," said Pablo Damasceno, who holds a PhD in applied physics. Damasceno and his colleagues then examined the relationship between things like the curvature of the cuts and how it impacted the stretchiness of the material.
The microscopic kirigami was produced by using graphene oxide to create unique “paper.” The material was then layered with a flexible plastic. The most challenging part was making cuts that measured merely a few tenths of a millimeter. This was accomplished by first coating the paper with a material that can be removed with the help of a laser’s light. The dashes were burnt out of that material, transforming it into a mask for etching.
The researchers summoned a plasma of electrons and oxygen ions to break down the paper beneath the mask. This step allowed for tidy rows of microscopic dashes to develop. As the researchers anticipated, the material stretched without compromising conductivity. Their results were recently published in the journal Nature Materials. For more information, visit the University of Michigan’s website.