Ill-fitting joint sockets, contact dermatitis and sebaceous cysts are just a few of the problems plaguing prosthetic patients. They are all a result of the pressure that their prosthetic devices place on the soft tissues of their bodies.
Now researchers at Tel Aviv University, FOM Institute AMOLF and Leiden University in the Netherlands have devised a new way to create mechanical “metamaterials” — composites of synthetic materials that have structures and properties that are not usually found in natural materials — that can be programmed to deform in complex and unique ways.
These materials are a “breakthrough” and could lead to future applications in soft robotics and wearable technologies — and also to more close-fitting, comfortable and user-friendly prosthetics, the researchers said. The research was published last week in the journal Nature.
Dr. Yair Shokef of TAU’s School of Mechanical Engineering and Prof. Martin van Hecke of Leiden University and AMOLF, the Netherlands, proved their point through a three-dimensional printing of a metamaterial cube.
They developed a cube composed of 10x10x10 centimeter building blocks. A smiley-face pattern emerged on the side of the cube when it was compressed. This demonstrated that any pattern can be produced on the cube’s surface.
“We started with a series of flexible building blocks, or bricks, that had deformation properties that varied with their position,” said Shokef. “The blocks were able to change their shape when we applied pressure. From there, we were able to develop a new design principle to enable these bricks to be oriented and assembled into a larger metamaterial with machine-like functionalities.”
When it is submitted to spatially patterned compression in one direction, the metamaterial assumes predictable and spatially patterned dents and protrusions in other directions.
“A pattern of specific bulges appears when our seemingly normal cube is compressed,” said Shokef. “Using metamaterials, we can ‘program’ the material’s behavior by carefully designing its spatial structure.”
The deformation within the cube “results in a specific pattern on the sides of the cube,” Shokef said. “We can carefully combine the building blocks in a way that any desired pattern can appear on the sides of a compressed cube. We can also use the cube to analyze these patterns.”
There are many applications on the horizon for this new basic research. “This type of programmable ‘machine material’ could be ideal for prostheses or wearable technology in which a close fit with the body is important,” Shokef said. “If we can make the building blocks even more complex or produce these from other materials, the possibilities really are endless.”