New method leaves older ways of 3-D printing in its goopy wake

Speedy process creates objects using oxygen, UV light and liquid resin

Little Eiffel Tower

TOWERING MOVE  A little Eiffel Tower rises from goopy resin in just one hour, thanks to a new 3-D printing method that manipulates ultraviolet light and oxygen to create detailed objects. 

Lars Sahl

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Researchers have created a versatile method for producing three-dimensional objects from a puddle of goo in mere minutes — faster than current 3-D printers by orders of magnitude.

The technique, reported online March 16 in Science, manipulates a liquid resin, ultraviolet light and oxygen to create objects with precision down to less than a tenth of a millimeter. It could be used to manufacture products such as engine parts and medical devices.

“They really thought about the chemical process,” says chemist Lee Cronin of the University of Glasgow in Scotland, who was not involved with the study. The speed and chemical tricks will “definitely move the field forward,” he says.

Scientists have been using 3-D printers since the 1980s to manufacture custom pieces, layer by layer (SN: 3/9/13, p. 20). Some, like this new one, even use pools of resin and UV light in the manufacturing process. But speed has always been a problem, says polymer chemist Joseph DeSimone of the University of North Carolina at Chapel Hill.  “I know of mushrooms that grow faster than 3-D printers print,” he says.

Inspired by the movie Terminator 2: Judgment Day, in which the main villain forms from a puddle of liquid metal, DeSimone and colleagues turned to a group of goopy resins to come up with a chemical solution. When shot with UV light, these resins form chains, creating a hard polymer. But if oxygen seeps into the resin pool, researchers can say “Hasta la vista” to chain growth. (The gassy element prevents polymers from forming.)

DeSimone and colleagues created a resin chamber that has a windowpane on the bottom. The windowpane lets in UV light and also oxygen, much like new contact lenses. So the bottom layer of the resin pool is full of oxygen and no polymerization can happen there, regardless of UV light exposure. Scientists refer to this region as the “dead zone.” UV light shot up through the window, however, can reach a sweet spot further into the resin, past the dead zone.

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WHOLE NEW BALL GAME   With a dunk into a pool of liquid resin, a new method can quickly draw out detailed 3-D objects like this ball. The method works by carefully managing the resin’s exposure to ultraviolet light, which causes the resin to form a solid polymer, and limiting its exposure to oxygen, which prevents the resin from forming polymers. Both the light and the oxygen enter the resin pool from below.

Carbon3D, Inc.

DeSimone and colleagues lowered a metal plate into that sweet spot of the resin pool, just above the dead zone. By projecting a stream of UV light patterns that represent an object, polymers can start linking up on the metal plate within the sweet spot. Then the researchers slowly raise the plate, allowing for more resin to enter the sweet spot and solidify based on the projected UV patterns.

The result looks like a scene from a science fiction movie: a solid, detailed object rising from a shallow puddle of ooze. The researchers created complex structures, like a model of the Eiffel Tower. And the structures could form quickly, some as fast as 500 millimeters per hour, the authors report. Typical 3-D printer speeds are just several millimeters per hour.

“The ability to obtain high print speeds —such as the 100 mm/hour over large areas while still preserving high-resolution complex geometries —is really impressive” says materials engineer Joshua Pearce of Michigan Technological University in Houghton. This could create a new paradigm for manufacturing, he says.

The new 3-D printing technology could hit the market by mid-year. It’s unclear how much it will cost.

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