Standard 3D printing requires a bulky, pricey machine, but what if you could fit that technology in your pocket? Researchers have harnessed a familiar instrument—the pen—to create a first-of-its-kind process that transforms flat ink drawings into 3D objects when the drawings are dipped into a special solution. The advance could create everything from furniture to solar panels with the ease of 2D printing.
“This work is very elegant,” says Michael Dickey, a chemical engineer at North Carolina State University who was not involved with the new research. “You could draw something in 2D, ship it, and then transform it into 3D, and being able to use a pen to do that is just very cool.”
To make the advance, Sumin Lee and Seo Woo Song, bioengineers at Seoul National University, and colleagues started with a pen that looks like a dry-erase marker. They filled the implement with one of two inks. One, colored red in the video above, contained a compound called a surfactant, which makes the ink less adhesive. The other, colored black, has no surfactant. This ink “anchors” the drawing to the surface it is drawn on—in this case, a rock—to help stabilize the red ink as it transforms into its 3D shape.
When the researchers dip the drawing—in this case, a flower—in water, the black ink stays put. But the red ink film floats up, thanks to a phenomenon called capillary-induced peeling, in which the water penetrates between the less-sticky ink and the rock. The ink is hydrophobic—it repels water—so the less-sticky ink floats to the surface in a 3D shape thanks to the tension between film and water.
But the scientists hit a snag when they tried to remove the finished product from the water: The delicate 3D film wouldn’t stay in shape. So they tweaked the chemistry of both inks by adding iron microparticles and dipped the drawing into a solution containing potassium persulfate instead of plain water. The potassium persulfate reacts with the iron to coat and strengthen the 3D object after 3 minutes of submersion, the researchers report today in Science Advances.
The researchers say the ink could work within existing technology that mass-produces printed objects like the roll-to-roll systems that print newspapers. Items would be mass-printed in 2D, then dipped in a bath of the potassium persulfate solution to transform them into 3D. That could allow engineers to fabricate everything from wine glasses to kitchen tables as flat objects using existing, efficient modes of manufacturing.
The team concedes that the technology needs work. To be used to create electrical objects such as solar panels, for example, it needs to be able to carry conducting components.
Jennifer Lewis, an engineer at Harvard University who was not involved with this research, agrees. If the ink film could carry electronic circuits, ”that would be powerful,” she says. Still, she says, the team’s approach is an important advance for the field of 3D printing.
Beyond manufacturing, there’s just something irresistible about putting pen to paper, says Jiyun Kim, a materials scientist at Ulsan National Institute of Science and Technology. “People still love to draw things by hand,” she says; it’s fun to watch your drawings come to life. “I think this technology has artistic value, too.”