Mechanical & Fluid Systems
Researchers at Georgia Tech 3D printed an object made with tensegrity, a structural system of floating rods in compression and cables in continuous tension. (Credit: Rob Felt)

A team of researchers from the Georgia Institute of Technology has developed a way to use 3D printers to create objects capable of shape change. The objects use tensegrity, a structural system of floating rods in compression and cables in continuous tension. The researchers fabricated the struts from shape memory polymers that unfold when heated. The technology could someday be used in applications ranging from space missions to biomedical devices.

“Tensegrity structures are extremely lightweight while also being very strong,” said Glaucio Paulino, a professor at 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. The goal is to find a way to deploy a large object that initially takes up little space.”

The researchers used 3D printers to create the struts that make up one of the primary components of the tensegrity structure. To enable the struts to be temporarily folded flat, the researchers designed them to be hollow with a narrow opening that runs the length of the tube. Each strut has an attachment point on each end to connect to a network of elastic cables, which are also made with 3D printers.

Once the struts were heated to 65 °C, the researchers could partially flatten and fold them into a shape resembling the letter W. The cooled structures then retain the temporary shape. With all cables attached, the objects can be reheated to initiate the transformation into tensegrity structures.

“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,” said Georgia Tech professor Jerry Qi.

A key component of making 3D printed objects that can transform into tensegrity structures was controlling the rate and sequence of expansion. The shape memory polymers enable the researchers to fine-tune how quickly each strut expands by adjusting the temperature at which the expansion occurs. That enables structures to be designed with struts that expand sequentially.

The researchers envision that the new 3D printed structures could be used for super lightweight structures needed for space exploration, or even shape-change soft robots.

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