Lawrence Livermore National Laboratory, is in Livermore California.
Researchers from the laboratory, add hollow gas-filled “micro-balloons” into silicone-based ink, the researchers engineered the material so it can be compressed or “programmed” at an elevated temperature, remaining in that state as it cools. When reheated, the gas in the micro-balloons expands, causing the structures to return to their original shape. When combined with 3D printing, this shape memory behavior is often referred to as “4D printing,” with the fourth dimension being time.
“The impressive part was how well the structures could recover their shape after they were reheated,” said LLNL researcher Amanda Wu, the lead author. “We didn’t see a distorted structure, we saw a fully recovered structure. Because the silicone network is completely cross-linked, it holds the part together, so the structure recovers its original shape in a predictable, repeatable way.”
In the beginning, the process was an accelerated aging test to see if the material would be useful. 4D printing took on a pretty large compression set and that made them think if it was permanent. We weren’t really thrilled about that, but researchers tried to see if it could recover its shape when heated. They tested it and it was a successful experiment.