[Top] Schematic diagram of the CLIP setup. [Bottom] A model of the Eiffel Tower emerges from the CLIP resin bath. [Images: Tumbleston et al., Science, doi: 10.1126/science.aaa2397; Lars Sahl]
Additive manufacturing—colloquially known as 3-D printing—usually tops the list of transformative technologies set to sweep away conventional, centralized processes and assumptions about industrial production. But 3-D printing has an Achilles’ heel: it can be painfully slow, with complex items only a few centimeters long taking hours to produce—hardly the stuff of Star Trek’s replicators.
Now, a team led by Joseph DeSimone of the University of North Carolina, Chapel Hill, USA, and colleagues has unveiled what the researchers are calling a “fundamentally new approach” to 3-D printing, with manufacturing speeds potentially 25 to 100 times those of systems on the market today (Science, doi: 10.1126/science.aaa2397). And DeSimone and his colleagues are moving aggressively forward to commercialize the new technology.
Current 3-D printing technologies, such as laser sintering and fused deposition modeling, work by building up an object, layer by layer, in a stepwise fashion according to a preset scheme. At present, creating macroscopic objects of much interest through these techniques can take hours, a timeline that has proved a stumbling block for adoption of the technology in mass production.
To speed up 3-D printing, DeSimone and his colleagues focused on modifying the kinetics of an established technique, stereolithography, under which parts are built up through sequential curing of polymer resin layers using an ultraviolet laser. The new process—called continuous liquid interface production (CLIP)—draws up a support plate, anchored to the growing object, from a resin-containing bath, with a UV light source continually projecting cross-sectional images of the target object that are cured into the resin as the object is steadily built up and drawn out of the bath.
The key to the process is the UV-transparent window through which the images are projected at the bottom of the resin bath. The window is oxygen permeable, and the thin layer of oxygen-enriched resin that collects above the window creates a permanent liquid “dead zone” (in which solidification cannot occur) beneath the steadily growing part. The presence of this dead zone allows the object to grow continuously by solidification immediately above the liquid—in contrast to conventional bottom-up stereolithography, in which, according to the paper, “UV exposure, resin renewal, and part movement must be conducted in separate and discrete steps.”
The dead-zone advantage, according to the team, allows the creation of objects at rates as high as 100 millimeters per hour, far outstripping conventional rates. The process is graphically depicted in a time-lapse video, in which a detailed scale model of the Eiffel Tower emerges from a blue resin bath in a manner reminiscent of a magician extracting large objects from an impossibly small box:
The UNC team says that CLIP should be feasible with a wide range of materials, including elastomers, silicones, nylon-like materials, ceramics and biodegradables. Indeed, DeSimone envisions a future in which the speed of the process and the range of applicable materials could allow for while-you-wait printing of personalized medical devices, a project on which several of his grad students are actively working. “It would not be impossible within coming years,” DeSimone maintains, “to enable personalized coronary stents, dental implants or prosthetics to be 3-D printed on demand in a medical setting.”
DeSimone himself, meanwhile, is on academic sabbatical, proactively working to move the technology to market through a company called Carbon3D Inc., in which he serves as CEO. The unveiling of the new technology in Science has been accompanied by an active publicity campaign. Indeed, in what is perhaps a sign of the times, publication of the paper was timed to coincide with a talk given by DeSimone at the kickoff of this year’s TEDActive conference in British Columbia, Canada.