This '4D' printing method could make packing for outer space much easier

These tiny objects made with 3D printers can dramatically expand when exposed to heat.

Scientists have created a pair of compact, unfurling structures that could pave the way for innovations in biomedical devices or space exploration, where payloads can cost tens of thousands of dollars per pound.

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A team at the Georgia Institute of Technology crafted these objects using "tensegrity" -- a structural system of floating rods in compression and cables in continuous tension. Researchers crafted the rods and cables, called "struts," from shape memory polymers that unfold when heated.

"Tensegrity structures are extremely lightweight while also being very strong," Glaucio Paulino, an engineering professor at Georgia Tech and co-author of a new study, said in a press release.

A "tensegrity" object. Credit: georgia tech

"That's the reason there's a heavy amount of interest right now in researching the use of tensegrity structures for outer space exploration," Paulino added. "The goal is to find a way to deploy a large object that initially takes up little space."

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This method is what some people in the scientific community would call "4D printing," in which a 3D-printed structure changes shape after a print, Tech Crunch noted. The fourth dimension is time, in this case.

The Georgia Tech team published their findings last week in the journal Scientific Reports.

Researchers made the struts from 3D printers. To allow the struts to be temporarily folded flat, the team designed the struts to be hollow, with a narrow opening spanning the length of the tubes. Attachment points at the end of each strut connect the tubes to a network of elastic cables, which were also made with 3D printers.

Next, the struts were heated to 65 degrees Celsius, or 149 degrees Fahrenheit. This allowed researchers to partially flatten and fold the struts into a shape resembling the letter "W." Once they cooled, the structures retained their temporary shape.

"We believe that you could build something like an antenna that initially is compressed and takes up little space, but once it's heated, say just from the heat of the sun, would fully expand," Jerry Qi, a coauthor of the report and engineering professor at Georgia Tech, said in the press release.

Credit: georgia tech

The concept of tensegrity -- a mashup of "tensional integrity" -- has been used as the structural basis in several high-profile projects, including a large pedestrian bridge in Brisbane, Australia, and stadium roofs, including the Georgia Dome stadium in Atlanta and the Olympic Gymnastics Arena in Seoul, South Korea.

Beyond space exploration, these new 4D printed structures might also be used to create shape-changing soft robots, the researchers said.

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