Adhesives used for common pain-relieving bandages often do not stick properly when attached to places that encounter large, inhomogenous bending motion, like elbows and knees. To solve this problem, kirigami was considered as a possible solution. Originally an Asian folk art, kirigami is the practice of cutting intricate patterns into paper and folding this paper, much like origami, to create three-dimensional structures. More recently, some scientists have been exploring kirigami as a way to develop new functional materials.
A thin, lightweight, rubber-like adhesive film was developed that can stick to highly deformable regions of the body, such as the knee and elbow, and maintain its hold after 100 bending cycles. The key to the film's clinginess is a pattern of slits that the researchers have cut into the film, similar to the cuts made in kirigami.
When placed on the knee, the film slits open at the center 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.
A kirigami-patterned adhesive bandage, as well as a heat pad consisting of a kirigami film threaded with heating wires, also was developed. With the application of a 3-Volt power supply, the pad maintains a steady temperature of 100 °F. The bandage can function and stick to the skin even after 100 knee bends. Kirigami-patterned adhesives may enable products such as everyday medical bandages, and wearable and soft electronics.
Three main parameters give kirigami films their adhesive properties: shear-lag, in which shear deformation of 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; and inhomogenous deformation, in which a film can maintain its overall adhesion, even as parts of its underlying surface may bend and stretch more than others.
Future work involves changing the elastomer film to gel material, which could directly diffuse medicine into the skin.