While most solid materials expand with heat, a new 3D-printed structure built by Massachusetts Institute of Technology (MIT) engineers is designed to shrink. The metamaterial may enable heat-resistant circuit boards.

The tiny, star-shaped structures feature interconnected beams, or trusses. The structures, each about the size of a sugar cube, quickly shrink when heated to about 540 °F.

Each structure’s trusses are made from typical materials that expand with heat. The trusses, when arranged in certain architectures, pull the structure inward like a Hoberman sphere — a collapsible toy ball made from interconnecting lattices and joints.

The internal beams were made from the elastic material, while the outer trusses were composed of stiff copper. The counter-intuitive materials could support new computer chips that warp and deform when heated for long periods of time.

Nicholas X. Fang, an associate professor of mechanical engineering at MIT, and researchers developed a computational model to characterize the relationships between the interconnecting beams, the spaces between the beams, and the direction and degree to which they expand with heat.

The team can control how much a structure will shrink by tuning two main “knobs” in the model: the dimensions of the individual beams, and their relative stiffness, which is directly related to a material’s rate of heat expansion.


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