A team of researchers from the Georgia Institute of Technology has developed a way to use 3D printers to create objects capable of dramatic expansion. The technology could someday be used in applications ranging from space missions to biomedical devices. The new 3D-printed 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.
“Tensegrity structures are extremely lightweight while also being very strong,” said Georgia Tech professor Glaucio Paulino. “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 Jerry Qi, another Georgia Tech professor who worked on the project.
A key component of making 3D printed objects that can transform into tensegrity structures is controlling the rate and sequence of expansion. The shape memory polymers enabled the researchers to fine-tune how quickly each strut expanded by adjusting the temperature at which the expansion occured. The fine-tuning process enables structures to be designed with struts that expand sequentially.
“For bigger and more complicated structures, if you don’t control the sequence that these struts expand, it tangles and you have a mess,” Paulino said. “By controlling the temperature at which each strut expands, we can have a phased deployment and avoid this entanglement.”
The term “tensegrity” comes from a combination of the words tensional and integrity. The concept has been used as the structural basis for several notable projects through the years, including a large pedestrian bridge in Brisbane, Australia, and stadium roofs such as the Georgia Dome stadium in Atlanta. The researchers envision that the new 3D printed structures could be used in super lightweight structures needed for space exploration, or even for shape-change soft robots.
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