No more loose plasters as scientists reveal kirigami-inspired design

27 Mar 2018

The kirigami design. Image courtesy of researchers/MIT

We can soon look forward to the end of plasters that refuse to cling on to elbows and knees, thanks to a team of MIT scientists.

We’ve all been in the situation where a scratch on the knee sees us seeking the holy grail of plasters: one that doesn’t fall off after five minutes because the adhesive can’t cope with a little movement.

But now, a team of MIT engineers has conjured up a new design that can stick to all of our injured regions and maintain its hold even after 100 bending cycles.

Future Human

According to MIT News, the new plaster design is based on the Japanese paper-folding art known as kirigami, which allows for slits to expand, thereby creating a greater amount of surface area on the affected region.

After attaching the design to a volunteer’s knee, the slits opened at the centre where the bending was most pronounced, but the slits at the outer regions of the plaster remained closed, creating a strong bond.

Detailing its findings in the journal Soft Matter, the team said that, while designs similar to kirigami have been used to create a more stretchable surface, this is the first instance to find that it also improves adhesiveness.

It was fabricated by pouring a rubber solution called liquid elastomer into 3D-printed moulds and, once cooled, they were studded with rows of offset slits.

They are then coated with what is essentially the same adhesive coating put on to traditional plasters, finding that it was able to withstand prolonged bending because its energy release rate – a quantity to evaluate detaching – varied throughout the plaster.

From left: A standard film versus the new kirigami design. GIF: MIT News

Can act as a heat pad

With the base knowledge of this research, the team believes that the design could act as a blueprint for future designs that could identify the best pattern of cuts based on its three adhesive properties: shear lag, partial debonding and inhomogeneous deformation.

“These three parameters will help guide the design of soft, advanced materials,” said Ruike Zhao, who was involved in the research.

“You can always design other patterns, just like folk art. There are so many solutions that we can think of. Just follow the mechanical guidance for an optimised design, and you can achieve a lot of things.”

The film was also tested for its use as a heat pad and, when applied with a three-volt power supply, it was able to provide almost 38C in temperature.

Having already secured a patent for the design and a collaboration with a Chinese medical supply company, Ruike said the next step is to keep finding new materials that the plaster concept could work for.

“The current films are purely elastomers,” Ruike said. “We want to change the film material to gels, which can directly diffuse medicine into the skin. That’s our next step.”

Colm Gorey was a senior journalist with Silicon Republic