New Method Makes Designing a Metamaterial Cell Easy

Massachusetts Institute of Technology, Cambridge, MA

Researchers from MIT and the Institute of Science and Technology Austria have created a technique to include many different building blocks of cellular metamaterials into one, unified graph-based representation. They used this representation to create a user-friendly interface that an engineer can utilize to quickly and easily model metamaterials, edit the structures, and simulate their properties. (Image: Courtesy of the researchers)

Researchers from MIT and the Institute of Science and Technology Austria have developed a computational technique that makes it easier to quickly design a metamaterial cell from smaller building blocks like interconnected beams or thin plates, and then evaluate the resulting metamaterial’s properties.

Their approach, like a specialized computer-aided design (CAD) system for metamaterials, allows an engineer to quickly model even very complex metamaterials and experiment with designs that may have otherwise taken days to develop. The user-friendly interface also enables the user to explore the entire space of potential metamaterial shapes, since all building blocks are at their disposal.

“We came up with a representation that can cover all of the different shapes engineers have traditionally shown interest in. Because you can build them all the same way, that means you can switch between them more fluidly,” said MIT electrical engineering and computer science graduate student Liane Makatura, co-lead author of a paper on this technique.

When a scientist develops a cellular metamaterial, she typically begins by choosing a representation that will be used to describe her potential designs. This choice determines the set of shapes that will be available for exploration.

The team took a step back and closely examined different metamaterials. They saw that the shapes that comprise the overall structure could be easily represented by lower-dimensional shapes, and they also noticed that cellular metamaterials often have symmetries, so only a small part of the structure needs to be represented. The rest can be built by rotating and mirroring that initial piece.

“By combining those two observations, we arrived at this idea that cellular metamaterials could be well-represented as a graph structure,” she said.

With their graph-based representation, a user builds a metamaterial skeleton using building blocks that are created by vertices and edges. Then the user employs a function over that line to specify the thickness of the beam, which can be varied so one part of the beam is thicker than another.

The process for surfaces is similar — the user marks the most important features with vertices and then chooses a solver that infers the rest of the surface.

These easy-to-use solvers even allow users to quickly construct a highly complex type of metamaterial, called a triply periodic minimal surface (TPMS). These structures are incredibly powerful, but the usual process to develop them is arduous and prone to failure.

“With our representation, you can also start combining these shapes. Perhaps a unit cell containing both a TPMS structure and a beam structure could give you interesting properties. But so far, those combinations really haven’t been explored to any degree,” she said.

At the end of the process, the system outputs the entire graph-based procedure, showing every operation the user took to reach the final structure — all the vertices, edges, solvers, transformations, and thickening operations.

Within the user interface, designers can preview the current structure at any point in the building procedure and directly predict certain properties, such as its stiffness. Then, the user can iteratively tweak some parameters and evaluate it again until a suitable design is reached.

The researchers used their system to recreate structures that spanned many unique classes of metamaterials. Once they had designed the skeletons, each metamaterial structure took only seconds to generate.

They also created automated exploration algorithms, giving each a set of rules and then turning it loose in their system. In one test, an algorithm returned more than 1,000 potential truss-based structures in about an hour.

In addition, the researchers conducted a user-study with 10 individuals who had little prior experience modeling metamaterials. The users were able to successfully model all six structures they were given, and most agreed that the procedural graph representation made the process easier.

In the future, the researchers want to enhance their technique by incorporating more complex skeleton thickening procedures, continue exploring the use of automatic generation algorithms, and, in the long term, use this system for inverse design.

For more information, contact Abby Abazorius at This email address is being protected from spambots. You need JavaScript enabled to view it.; 617-253-2709.