With a trick of chemistry, researchers have sped up, and smoothed, the process of three-dimensional (3D) printing, producing objects in minutes instead of hours.
3D printers typically build one horizontal layer at time. Some do so by depositing droplets of building material as if they were laying tiny bricks. Others create their products by shining ultraviolet rays up into a bath of liquid resin. The light solidifies the resin, and the partial product is pulled upwards one notch to repeat the process for the next layer below. Objects appear to materialize out of the bath, just as the shape-shifting robot in the 1991 science-fiction film Terminator 2 formed out of liquid metal.
But both types of processes can take several hours or even a day to produce a complex structure.
A team led by Joseph DeSimone, a chemist at the University of North Carolina at Chapel Hill, has now refined the liquid-resin process to make it go continuously rather than in fits and starts. They made the bottom of the container that holds the resin bath from a material that is permeable to oxygen. Because oxygen inhibits the solidification of resin, it creates a ‘dead zone’ — a layer just tens of microns thick at the bottom of the container — where the resin stays liquid even when ultraviolet rays are shining on it. The solidification reaction happens instead just above the dead zone. Because liquid is always present below the slowly forming object, the researchers can pull it up in a continuous manner, rather than waiting for new liquid resin to flow in.
“When you operate this way you can go really fast,” says DeSimone. Depending on the object's size and the level of detail required, printing can take mere minutes. The faster process also makes it possible to use materials that were not suitable for traditional 3D printing methods, including some that are rubbery and flexible. The results appeared online in Science on 16 March1.
“I think the speed is impressive,” says Lee Cronin, a chemist at the University of Glasgow, UK, who was not involved in the study.
DeSimone and his colleagues have formed a start-up company in Redwood City, California, called Carbon3D. The company aims at releasing a commercial printer within the year, says Rob Schoeben, the company's chief marketing and strategy officer. Some of the applications could include building custom 'microfluidic chips' to use in chemistry experiments, DeSimone says. “We’re really excited about what designers and engineers around the world are going to do with it.”
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