Cutting Patterns Give Kirigami Materials New Mechanical Properties

Researchers at The University of Osaka have developed a new kirigami structure that twists when stretched. Their work shows how carefully designed cut patterns can change the mechanical behaviour of sheet materials. The research highlights how geometry, rather than material composition, creates new functional properties. This approach could support future developments in soft robotics, actuators and other lightweight engineering applications.

Kirigami, a variation of the traditional Japanese art of origami, creates three-dimensional forms by combining folds with strategically placed cuts. Many people know it from pop-up cards. However, engineers also use kirigami to transform flat materials into structures with unusual mechanical properties.

Geometry Determines Performance

Many engineered materials rely on their chemical composition for their performance. Kirigami structures work differently. Their geometry determines many of their mechanical properties. Designers can introduce precise cuts into flat sheets to create lightweight structures with characteristics that conventional manufacturing cannot easily achieve.

Previous studies mainly examined kirigami patterns with cuts placed parallel or perpendicular to the direction of the applied force. The University of Osaka team explored a different approach. They introduced periodic inclined laser cuts into polyester sheets, rolled the sheets into cylinders and then tested their mechanical performance.

The experiments showed that the angle of the cuts strongly influenced how the structures responded to stretching.

Chiral Structures Convert Tension Into Rotation

The new kirigami patterns exhibit chirality, a geometric property that prevents a structure from matching its mirror image. Human hands provide a familiar example because the left and right hand have the same overall shape but cannot overlap exactly.

Lead author Isamu Hashiguchi explained that the team characterised the mechanical properties of the cylindrical kirigami structures according to their chiral geometry. During testing, stretching the cylinders caused them to twist and rotate. As a result, the structures converted tensile force into rotational movement.

This tension-to-rotation coupling could support applications that require controlled movement without conventional mechanical components. Flexible twisting elements could therefore become useful building blocks for soft robots and compact actuators that perform precise movements.

Auxetic Properties Expand Design Possibilities

The researchers also found that some of the chiral kirigami structures behave as auxetic materials. Unlike conventional materials, auxetic materials expand sideways when stretched instead of becoming thinner.

Designers already use auxetic materials in medical stents that support blood vessels, the oesophagus and bronchial tubes. By combining auxetic behaviour with controlled rotation, the new kirigami structures could support future developments in medical devices, robotics and adaptive engineering systems.

The study demonstrates how designers can significantly change mechanical performance by modifying cutting patterns alone. This strategy offers new opportunities to develop lightweight, flexible and programmable material systems.

Source: The University of Osaka
Photo: Cottonbro