Scientists at Delft University of Technology (TU Delft) in the Netherlands have created a new way to print flat structures which self-fold into complex shapes according to a pre-planned sequence. The research has many applications, including the potential to improve bone transplants, the university said.
Essentially a combination of the Japanese paper-folding art of origami and 3D printing, the technique created by Amir Zadpoor and his team of researchers is means of creating shape-shifting constructs without the high costs or manual labour usually associated with this process.
Zadpoor’s team used an Ultimaker, one of the most popular 3D printers, and PLA, the most common printing material available. “At about 17 Euro’s per kilo, it’s dirt cheap”, said Zadpoor. “Nevertheless, we created some of the most complex shape-shifting ever reported with it.” The process is also fully automated and requires no manual labour whatsoever.
Zadpoor’s team achieved this by creating a technique in which they simultaneously printed and stretched the material in certain spots. “The stretching is stored inside the material as a memory”, PhD researcher Teunis van Manen explained. “When heated up, the memory is released and the material wants to go back to its original state.”
The researchers also alternated the thickness and the alignment of the filaments in the material.
“What makes the team’s shape-shifting objects so advanced is the fact that they self-fold according to a pre-planned sequence,” TU Delft wrote about the project.
“If the goal is to create complex shapes, and it is, some parts should fold sooner than others”, Zadpoor explained. “Therefore, we needed to program time delays into the material. This is called sequential shape-shifting.”
This approach marks an important step in the development of better bone implants for two reasons, the researchers explained. Firstly, it makes it possible to create prosthetics with a porous interior which allows a patient’s own stem cells to move into the structure of the implant and attach themselves to the interior surface area, instead of just coating the exterior. This will result in a stronger, more durable implant.
“We call these ‘instructive surfaces’, because they apply certain forces to the stem cells, prompting them to develop into the cells we want them to be”’, said PhD researcher Shahram Janbaz. “A pillar shape, for instance, may encourage stem cells to become bone cells.”
It is impossible to create such instructive surfaces on the inside of a 3D structure. “This is why we decided we needed to start from a flat surface,” said Zadpoor.
Other applications for the research include printed electronics (“by using this technique, it may be possible to incorporate printed, 2D-electronics into a 3D shape,” Zadpoor said) and flat-pack furniture. “Shape-shifting could definitely turn many of our existing 2D worlds into 3D worlds’, he said. “We are already being contacted by people who are interested in working with it.”
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