A group of engineers recently took a novel approach to materials research by doing just this and employing the ancient Japanese art of kirigami in an effort to create shape-shifting metamaterials. Kirigami involves both cutting and folding sheets of paper to obtain three-dimensional shapes.
The option to make cuts gives kirigami better flexibility for geometries than its cousin origami (which only allows folding), as it can create complex 3D shapes from a single two-dimensional sheet. This property was the starting point for the metamaterials research.
Making Metamaterials
Metamaterials are materials that are engineered to have properties that don’t occur naturally. For example, metamaterials can be designed to manipulate electromagnetic waves in precise ways not possible with conventional materials.
However, the engineers from the University of Bristol had a different idea in mind: they wanted to create a mechanical metamaterial that could change its own shape.
"Mechanical metamaterials exhibit unusual properties through the shape and deformation of their engineered subunits,” said Fabrizio Scarpa, a co-author on the research. “Our research presents a new investigation of the kinematics of a family of cellular metamaterials based on kirigami design principles. This technique allows us to create cellular structures with engineered cuts and folds that produce large shape and volume changes and with extremely directional, tuneable mechanical properties."
The team’s metamaterial was produced with polyether ether ketone (PEEK) film, a thermoplastic polymer with good formability. The film was cut, corrugated and folded into an open honeycomb configuration. By manipulating the pattern of cuts, one can introduce holes or channels into the honeycomb. This allows different sensing and electronic systems to be integrated in the structure, resulting in a smart shape-shifting material.
A material that can change its shape and mechanical properties at will has a wide range of potential applications, including robotics, morphing structures for airframes and spacecraft and smart, adaptive antennas. Robin Neville, the PhD student who led the research, is confident that his team has made significant strides towards these possibilities.
"By combining analytical models and numerical simulations we have demonstrated how these kirigami cellular metamaterials can change their deformation characteristics,” Neville said. “We have also shown the potential of using these classes of mechanical metamaterials for shape change applications like morphing structures."
To learn more about the kirigami metamaterial, you can read the team’s paper in Scientific Reports .
For more shape-shifting material news, read about this breakthrough in shape-changing materials .