MIT scientists have created shape-memory structures that can return to their original shape when exposed to a certain temperature
Researchers from Massachusetts Institute of Technology (MIT) in collaboration with Singaporean University have created new kind of 3D printed structures. These structures have a remarkable ability to ‘remember’ their original shapes.
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The shapes of these 3D printable structures can be changed by twisting, stretching or bending them but on temporality basis. When exposed to heat, they return to their original shape in a matter of seconds.
These shape-memory structures can be created in varying sizes, from as small as the diameter of human hair to one-tenth as big as existing printable structures. These shape-memory structures hold promise for supporting a wide range of fields, including solar panel industry and medical field.
“Our method not only enables 4-D printing at the micron-scale, but also suggests recipes to print shape-memory polymers that can be stretched 10 times larger than those printed by commercial 3-D printers,” said Qi Kevin Ge from Singapore University of Technology and Design (SUTD).
“This will advance 4-D printing into a wide variety of practical applications, including biomedical devices, deployable aerospace structures, and shape-changing photovoltaic solar cells.”
Researchers have used shape-memory polymers for printing these three-dimensional structures. Shape-memory polymers are smart materials that can bounce back from a deformed state to their original shape induced by an external stimulus (trigger), such as heat, light or electricity. These soft and flexible materials have already been utilized for making 3D shape-memory structures.
To improve their efficiency, MIT researchers used an innovative 3-D printing process called microstereolithography, which is based on light. The process design structures with more fine details than conventional 3D printers and reduce their size to a great extent. Size restriction ensures how fast the material can recover its original shape and also contributes to boost the effectiveness of the proces.
“We’re printing with light, layer by layer. It’s almost like how dentists form replicas of teeth and fill cavities, except that we’re doing it with high-resolution lenses that come from the semiconductor industry, which give us intricate parts, with dimensions comparable to the diameter of a human hair.” Nicholas X. Fang, professor of mechanical engineering at MIT said.
Researchers have created a variety of structures, including coils, flowers, and the miniature Eiffel tower using this technology. These structures could be stretched to three times their original length without breaking and sprang back to their original shapes within seconds when heated at specific temperature, within the range of 40 C to 180 C.
“Because we’re using our own printers that offer much smaller pixel size, we’re seeing much faster response, on the order of seconds,” said Fang. “If we can push to even smaller dimensions, we may also be able to push their response time, to milliseconds.”