Blisters, wrinkles useful at last

BOSTON:A STICKER PEELING off a window could provide a useful model for fabricating "bendy" electronics, according to research at Massachusetts Institute of Technology.

It can prove troublesome to incorporate electronic circuits into flexible items like clothing, gloves or electronic paper - when the material twists the wires can become damaged.

But the MIT team has come up with an easy way to blister the film and partially separate it from the flexing material underneath, reducing the risk of wire fatigue or fracture.

To do this, they studied the delamination and wrinkling that happens when adhering layers expand at different rates as they heat up - like the way a sticker blisters from a car window in sunlight - or else when the layers are compressed.

In controlled experiments the team stretched and compressed surfaces with thin films attached to them, then measured the dimensions of resulting blisters.

They used the model to predict how blisters form and evolve, and to work out how parameters such as adhesion and film thickness affect the formation of such blips between layers. And they argue that by controlling those parameters and intentionally engineering blisters into the circuits, wires could ultimately be protected from damage when the underlying material twists or stretches.

The idea for the project struck when applied mathematician Pedro Reis saw pieces of tape stuck to a window on a lab door at MIT.

"It's something that's around you all the time - but if you look at it a different way you can see something new," says Reis, a senior author on the study on Macroscopic Delamination of Thin Films from Elastic Substrates, published online last month in the Proceedings of the National Academy of Sciences.