If you've ever toyed with the petals of a rose, you'll know that they're pleasingly stretchy. Now, their material properties are being aped to produce a new breed of stretchable electronics.
The idea of flexible circuitry continues to appeal, and it's easy to understand why: a rollable tablet or bendable phone would be a joy to cary and use. But while screens are increasingly bendy, electronic circuity refuses to flex because it's typically built on rigid silicon substrates. Attempts to make things more compliant have instead used elastic substrates — but creating the right circuitry on them has proven to be complex, because normal printed circuits break when they stretch.
Now, a team from Hong Kong Polytechnic University has taken the rather romantic rose as a source of inspiration. The team has used the surface topology of the rose petal to create a material that allows standard printed circuits to flex without breaking. Taking real petal as a mould, they have created elastomer layers that exhibit the same kind of surface detail as the petal — a series of microscale craters, whose "sharp ridges act as crack-stopping edges," the researchers write. In rose petals, that stops them from tearing, but it can benefit flexible electronics, too. They continue:
"[W]hen conducting materials such as metal thin films are deposited on top, the sharp ridges can effectively stop the propagation of microcracks in the conducting layer formed under large strains. As a consequence, the electrical resistance of the conducting layer shows remarkable stability in large-strain deformation. "
Indeed, the electrical properties of the printed circuits remained consistent until the samples were stretched to lengths 40 per cent greater than their original size, and continued to function until that figure reached 90 per cent. That means that more conventional circuit printing can be used on the new material — making the prospect of flexible circuits easier and considerably cheaper. [Advanced Science via Materials Views]