Fast new 3D printing method creates objects as big as an adult human


Chemists Joseph DeSimone and Chad Mirkin have known each other for decades. They’re such good friends that they’ve even vacationed together on the North Carolina coast. But now, Mirkin is doing his best to put DeSimone, CEO of a well-known 3D printing company, out of work. Today, Mirkin and his colleagues at Northwestern University in Evanston, Illinois, announced they’ve created a 3D printer that builds the largest ever objects to date at high speeds—an advance that could revolutionize the manufacturing of car and airplane parts, and undermine DeSimone’s business, called Carbon.

Still, DeSimone says, “I love seeing the innovation in this field.” And he’s not worried about competition; when it comes to making finished products for customers, he says, the size of the printer is “just the beginning.” Mirkin’s technology has a long way to go to prove its worth on the market. Nevertheless, Michael McAlpine, a chemist at the University of Minnesota in Minneapolis, who was not involved with the work, describes it as “a pretty significant advance.”

3D printing got its start in the early 1980s. Today, the most common version uses light to cure a liquid plastic resin, layer by layer, into a solid. After the first layer is cured and pulled away from the printer, the projector illuminates the pattern onto a new layer that cures and joins to the first. 3D printers are precise enough to create far more intricate designs than most traditional manufacturing processes. Yet, early 3D printing was slow, often taking the better part of a day to manufacture objects the size of a coffee cup. Another problem was that the interfaces between the layers were structurally weak, making finished objects fragile.

A key advance came in 2015 when DeSimone, then at the University of North Carolina in Chapel Hill, and his colleagues reported in Science the creation of a 3D printing variation known as continuous liquid interface production (CLIP). The approach shines ultraviolet light through a window into a space filled by liquid resin. The window also allows oxygen to diffuse into the liquid, where it creates a thin “dead zone” that resists curing. Above this zone, the light cures the resin into a solid. A robotic attachment slowly pulls the growing solid out of the resin, allowing additional material to cure and adhere without interfaces; the resulting object is structurally far more robust than those made with previous methods.

Since publishing the results, DeSimone and his Redwood, California–based company have raised more than $680 million and forged production agreements with a host of companies, including Adidas, Ford, and Riddell, for the manufacture of everything from car parts and shoes to dental implants and football helmets.

Still, even CLIP has limitations. One problem is that the curing process releases heat, which can cause printed parts to warp and crack. To effectively dissipate this heat, objects can be no larger than 41.4 centimeters by 25.9 centimeters at the cross section.

Now, Mirkin’s team reports that by circulating a liquid coolant beneath the liquid resin, and later passing it through a cooling unit, they can pull heat directly from these growing printed objects. That allowed researchers to print 3D objects the size of a human adult in just a few hours, they write today in Science.

Mirkin notes that this technique can create objects nearly 1 square meter in cross section and more than 4 meters high by positioning light from four projectors side by side, a process they refer to as “tiling.” In the future, he says, adding additional projectors will let them print even bigger objects. “Tiling, with our technology, is theoretically unlimited,” Mirkin says.

Mirkin and his colleagues have launched a company called Azul 3D to commercialize the printing technology. The company is refining prototypes and expects to begin to sell printers in 18 months.

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