Japanese paper cutting art inspires scientists to develop better bandages

Boston: MIT scientists have developed a flexible, sticky bandage - using a Japanese paper-cutting art form called kirigami - that can be applied to tricky places like scraped up knees and elbows.

The thin, adhesive film can stick to highly deformable regions of the body, such as the knee and elbow, and maintain its hold even after 100 bending cycles.

The key to the film's clinginess is a pattern of slits that the researchers have cut into the film.

Researchers from Massachusetts Institute of Technology (MIT) in the US attached the "kirigami film" to a volunteer's knee and found that each time she bent her knee, the film's slits opened at the centre, in the region of the knee with the most pronounced bending, while the slits at the edges remained closed, allowing the film to remain bonded to the skin.

The kirigami cuts give the film not only stretch, but also better grip: The cuts that open release tension that would otherwise cause the entire film to peel away from the skin.

To demonstrate potential applications, the group fabricated a kirigami-patterned adhesive bandage, as well as a heat pad consisting of a kirigami film threaded with heating wires.

With the application of a three-volt power supply, the pad maintains a steady temperature of 100 degrees Celsius.

The group has also engineered a wearable electronic film outfitted with light-emitting diodes. All three films can function and stick to the skin, even after 100 knee bends.

Kirigami-patterned adhesives may enable a whole swath of products, from everyday medical bandages to wearable and soft electronics, said Ruike Zhao from MIT.

"Currently in the soft electronics field, people mostly attach devices to regions with small deformations, but not in areas with large deformations such as joint regions, because they would detach," said Zhao, lead author of the study published in the journal Soft Matter.

"I think kirigami film is one solution to this problem commonly found in adhesives and soft electronics," he said.

Adhesives bandages are very commonly used in our daily life, said Zhao.

"But when you try to attach them to places that encounter large, inhomogenous bending motion, like elbows and knees, they usually detach," Zhao said.

Originally an Asian folk art, kirigami is the practice of cutting intricate patterns into paper and folding this paper, much like origami, to create beautiful, elaborate three-dimensional structures.

More recently, some scientists have been exploring kirigami as a way to develop new, functional materials.

"In most cases, people make cuts in a structure to make it stretchable," Zhao said.

"But we are the first group to find, with a systematic mechanism study, that a kirigami design can improve a material's adhesion," he said.

The researchers fabricated thin kirigami films by pouring a liquid elastomer, or rubber solution, into 3D-printed molds.

Each mold was printed with rows of offset grooves of various spacings, which the researchers then filled with the rubber solution.

Once cured and lifted out of the molds, the thin elastomer layers were studded with rows of offset slits.

The film can be made from a wide range of materials, from soft polymers to hard metal sheets, researchers said.