Paper-folding art inspires better bandages

Cutting kirigami-style slits in stretchy films could make for bandages, heat pads, and wearable electronics that adhere to flexible surfaces.

Ruike Zhao, a postdoc in MIT’s Department of Mechanical Engineering, says kirigami-patterned adhesives may enable a whole swath of products, from everyday medical bandages to wearable and soft electronics. Image courtesy of researchers
Ruike Zhao, a postdoc in MIT’s Department of Mechanical Engineering, says kirigami-patterned adhesives may enable a whole swath of products, from everyday medical bandages to wearable and soft electronics. Image courtesy of researchers

Adhesives like these bandages are very commonly used in our daily life, but when you try to attach them to places that encounter large, inhomogenous bending motion, like elbows and knees, they usually detach. In order to develop better bandages, MIT engineers have developed a stickier-like solution, as a thin, lightweight, elastic-like film.

The adhesive film can stick to very deformable locales of the body, for example, the knee and elbow, and keep up its hold even after 100 twisting cycles. The way to the film’s clinginess is an example of openings that the specialists have cut into the film, like the cuts made in a paper-collapsing work of art known as kirigami.

The specialists attached the “kirigami film” to a volunteer’s knee and found that each time she bowed her knee, the film’s openings opened at the inside, in the locale of the knee with the most articulated twisting, while the openings at the edges stayed shut, enabling the film to remain attached to the skin. The kirigami cuts give the film extends, as well as better hold: The cuts that open discharge pressure that would somehow or another reason the whole film to peel far from the skin.

To show potential applications, the gathering manufactured a kirigami-designed cement swathe, and in addition, a warmth cushion comprising of a kirigami film strung with warming wires. With the use of a 3-volt control supply, the cushion keeps up a relentless temperature of 100 degrees Fahrenheit. The gathering has likewise built a wearable electronic film furnished with light-emanating diodes. Every one of the three movies can capacity and adhere to the skin, even after 100 knee twists.

Small, “kirigami” slits in polymer film enable the material to stick to the skin, even after 100 knee bends, compared to the same film without slits, which debonds after just one bending cycle.
Small, “kirigami” slits in polymer film enable the material to stick to the skin, even after 100 knee bends, compared to the same film without slits, which debonds after just one bending cycle.

Ruike Zhao, a postdoc in MIT’s Department of Mechanical Engineering, says kirigami-patterned adhesives may enable a whole swath of products, from everyday medical bandages to wearable and soft electronics.

“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,” Ruike says. “I think kirigami film is one solution to this problem commonly found in adhesives and soft electronics.”

Ruike is the lead author of a paper published online this month in the journal Soft Matter. Her co-authors are graduate students Shaoting Lin and Hyunwoo Yuk, along with Xuanhe Zhao, the Noyce Career Development Professor in MIT’s Department of Mechanical Engineering.

The team thought about kirigami as a potential solution. Initially an Asian people craftsmanship, kirigami is the act of cutting perplexing examples into paper and collapsing this paper, much like origami, to make wonderful, expound three-dimensional structures. All the more as of late, a few researchers have been investigating kirigami as an approach to grow new, practical materials.

“As a rule, individuals make slices in a structure to make it stretchable,” Ruike says. “Yet, we are the principal gathering to discover, with an orderly instrument think about, that a kirigami configuration can enhance a material’s grip.”

The scientists created thin kirigami films by pouring a fluid elastomer, or elastic arrangement, into 3-D-printed molds. Each form was printed with lines of counterbalance furrows of different spacings, which the scientists at that point loaded with the elastic arrangement. Once cured and lifted out of the molds, the thin elastomer layers were studded with columns of balance openings. The scientists say the film can be produced using an extensive variety of materials, from delicate polymers to hard metal sheets.

Ruike connected a thin­­­ cement covering, like what is connected to gauzes, to each film before appending it to a volunteer’s knee. She observed each film’s capacity to adhere to the knee after rehashed bowing, contrasted and an elastomer film that had no kirigami designs. After only one cycle, the plain, ceaseless film immediately confined, while the kirigami film kept up its hold, even after 100 knee twists.

To find out why kirigami cuts enhance a material’s adhesive properties, the researchers first bonded a kirigami film to a polymer surface, then subjected the material to stretch tests.

They gauged the measure of extending a kirigami film can experience before peeling far from the polymer surface — an estimation they used to figure the material’s basic “vitality discharge rate,” an amount to assess disconnecting.

They found that this vitality discharge rate fluctuated all through a solitary film: When they pulled the film from either end like an accordion, the openings toward the center showed a higher vitality discharge rate and were first to peel open under less extent. Conversely, the openings at either end of the film kept on adhering to the hidden surface and stayed shut.

Through these experiments, Ruike identified three main parameters that give kirigami films their adhesive properties: shear-lag, in which shear deformation of the film can reduce the strain on other parts of the film; partial debonding, in which the film segments around an open slit maintain a partial bond to the underlying surface.

Depending on the application, Ruike says researchers can use the team’s findings as a design blueprint to identify the best pattern of cuts and the optimal balance of the three parameters, for a given application.

“These three parameters will help guide the design of soft, advanced materials,” Ruike says. “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 optimized design, and you can achieve a lot of things.”

Ruike and her colleagues have filed a patent on their technique and are continuing to collaborate with the medical supply company, which is currently making plans to manufacture medicine patches made from kirigami films.

“They make this pain-relieving pad that’s pretty popular in China — even my parents use it,” Ruike says. “So it’s super exciting.”