Continuous liquid interface production of 3D objects

Solid objects can be printed from liquid resin in mere minutes.

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.

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.


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