3D printed structures could create shape-shifting solar panels

mit shape changing 3d print
© Qi (Kevin) Ge

Researchers are constantly trying to find ways to maximize the amount the sun's energy that a solar panel captures. Some approaches include putting coatings on the panels that harness more of the light spectrum, while others focus on tracking the sun's rays throughout the day.

Traditional solar tracking technology is very expensive and consists of heavy mechanical actuators that turn the solar panels, which means it's not used as often as the flat solar panels. Engineers at MIT and Singapore University of Technology and Design (SUTD) think that a new 3D printing breakthrough will change all that.

The researchers have created a 3D printed structure that "remembers" its original shape. The material can be bent, twisted, stretched and formed into complex shapes like flowers and even a replica of the Eiffel Tower that snap back to their original shape when heated to a certain temperature. The material can also be printed at the micron scale which allows for very precise shapes and designs.

The creation of polymers that can shift their shape when exposed to different temperatures could open up a world of amazing applications from drug delivery devices that only release medication when the wearer has a fever to flexible, lightweight actuators that turn solar panels to track the sun.

The researchers are calling this new technology 4-D printing because the material changes shape over the fourth dimension of time.

“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, an assistant professor at 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.”

The structures can be bent and shaped and then essentially frozen in that configuration at room temperature, but when heated to between 104 to 356 degrees Fahrenheit, the material becomes more rubbery and snaps back to its original state. The ability to print the polymer in fine detail means that the transition can happen very quickly.

“The reality is that, if you’re able to make it to much smaller dimensions, these materials can actually respond very quickly, within seconds,” said Nicholas X. Fang, associate professor of mechanical engineering at MIT. “For example, a flower can release pollen in milliseconds. It can only do that because its actuation mechanisms are at the micron scale.”

The team used a special type of 3D printing called microstereolithography that uses light to etch patterns on the polymers as they're layered, in this case very fine layers. They had to find the right blend of polymers to be both flexible and strong, which turned out to be a one with long-chain polymers that have strands like spaghetti and one with shorter chain polymers that act like a scaffold.

The team printed the polymers into designs like coils, flowers and the miniature Eiffel Tower and they each could be stretched to three times their original length and, when heated to the right temperature snap back to their original length and shape.

If this material can be combined with solar cells, we could see a new type of solar technology that captures more of the sun and can be used in far more places.

3D printed structures could create shape-shifting solar panels
The structures return to their original shape after being bent, twisted or stretched.

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