Engineers say they've turned to chemistry to speed up and smooth out the process of 3D printing, creating objects that rise out of a liquid bath like the Terminator 2 shape-shifting robot from the 1991 film emerging from a pool of liquid metal.

Researchers at Carbon3D, the company behind the new technology, admit to being inspired by that very scene to develop a technique that can create 3D objects in minutes instead of hours.

Current 3D printers create objects one horizontal layer at a time, either mechanically or by shining ultraviolet light into a batch of liquid resin, which hardens a layer and is then pulled up so the next layer can be created.

Complex structures can take hours or even a full day to be created.

"We think that popular 3D printing is actually misnamed — it's really just 2D printing over and over again," says Joseph DeSimone, one of Carbon3D's co-founders, who is also a professor of chemistry at North Carolina State and the University of North Carolina.

"The strides in that area have mostly been driven by mechanical engineers figuring out how to make things layer by layer to precisely create an object," he says. "We're two chemists and a physicist, so we came in with a different perspective."

Carbon3D calls its 3D printing "continuous liquid interface production technology," or CLIP.

In its printer, the liquid-resin hardening process is continual, rather than happening in fits and starts, one layer at a time.

Its resin container has a bottom made of a material permeable to oxygen, which inhibits the solidification of the resin in a "dead zone" layer just microns thick.

In that dead zone, the resin remains in a liquid state even with ultraviolet light shining onto it, so solidification takes place just above it.

With liquid always present beneath the forming object, the printer can pull the object upward continuously without having to wait for new liquid resin to flow in under it for another layer.

"When you operate this way you can go really fast," says DeSimone.

Printing can take mere minutes for some objects, depending on their size and level of required detail, he says.

The faster process also opens the way for materials not suitable for traditional 3D printing methods, including some that are rubbery and flexible, he says.

Carbon3D co-founder Edward Samulski, also a UNC professor, noted that the basic principle of using oxygen to keep a polymer from forming is something he and DeSimone often saw in their classrooms.

"We all teach this in our undergraduate courses," he says. "It illustrates what 1937 Nobel Laureate Albert Szent-Gyorgyi said: 'Discovery consists of seeing what everybody has seen and thinking what nobody has thought.' "

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