As 2018 begins, 3D printing—which only a few years ago was a relatively new technology—has reached the mainstream. However, researchers continue to explore the ways to improve the technology and the process of 3D printing, as well as vary the range of materials that can be used.
To the former end, researchers at the Lawrence Livermore National Laboratory (LLNL) have found an alternative to the typical layer-based additive manufacturing (AD) process by using a combination of technologies—including lasers and hologram-like images—that significantly speeds the process from hours or days to mere minutes.
Called volumetric 3D printing, the new process flashes laser-generated, hologram-like images onto photosensitive resin, printing a 3D shape all at the same time rather than pulling it together layer by layer, said Maxim Shusteff, a researcher at the lab who worked on the project.
“The fact that you can do fully 3D parts all in one step really does overcome an important problem in additive manufacturing,” he said.
By using laser-generated, hologram-like 3D images flashed into photosensitive resin, researchers at Lawrence Livermore National Laboratory, along with academic collaborators, have discovered they can build complex 3D parts in a fraction of the time of traditional layer-by-layer printing. With this process, researchers have printed beams, planes, struts at arbitrary angles, lattices, and complex and uniquely curved objects in a matter of seconds. (Source: LLNL)
Volumetric 3D printing creates parts by overlapping three laser beams that define an object’s geometry from three different directions, Shusteff explained. This creates a hologram-like 3D image suspended in the vat of resin.
In the process, researchers keep the laser light, which is at a higher intensity where the beams intersect, on for about 10 seconds, which enough time to cure the object. The excess resin is then drained out of the vat, with the fully formed 3D part left over.
“It’s a demonstration of what the next generation of additive manufacturing may be,” said LLNL engineer Chris Spadaccini, the head of Livermore Lab’s 3D-printing research. “Most 3D printing and additive manufacturing technologies consist of either a one-dimensional or two-dimensional unit operation. This moves fabrication to a fully 3D operation, which has not been done before.”
Indeed, the approach allows for 3D-printed parts to be built significantly faster than other polymer-based methods and almost all of the commercial methods used today, he said. Moreover, the costs of the method are low and it’s flexible, fast, and geometrically versatile, opening up a significant new research direction for rapid 3D printing, Spadaccini said.
“The potential impact on throughput could be enormous and if you can do it well, you can still have a lot of complexity,” he said.
The team used the process to print beams, planes, struts at random angles, lattices, and complex and uniquely curved objects, Shusteff said. Their work showed that volumetric printing does not have the same constraints as layering techniques, which has difficulty with spanning structures that might sag without support, he said.
“This might be the only way to do AM that doesn’t require layering,” Shusteff said. “If you can get away from layering, you have a chance to get rid of ridges and directional properties. Because all features within the parts are formed at the same time, they don’t have surface issues.”
Volumetric 3D printing also could allow for the fabrication of extra-soft materials such as hydrogels, which would otherwise be damaged or destroyed by fluid motion, researchers said. It also is the only additive manufacturing technique that works better in zero gravity, expanding the possibility of space-based production, they said.
Researchers published a paper about their work in the journal Science Advances. In addition to scientists at LLNL, researchers at the University of Rochester, UC Berkeley, and MIT also collaborated on the research.
While the process is indeed impressive—and could be made even faster with a higher-power light source—it does have its limitations, Shusteff said.
Because each laser beam moves through space without changing, there are restrictions on part resolution and on the kinds of geometries that can be formed, according to researchers. This means that extremely complex structures would require lots of intersecting laser beams and would limit the process, they said.
Researchers also aim to fine-tune the polymer chemistry and engineering of the process to ensure a high rate of success when printing, Spadaccini said.
“If you leave the light on too long it will start to cure everywhere, so there’s a timing game,” he said. “A lot of the science and engineering is figuring out how long you can keep it on and at what intensity, and how that couples with the chemistry.”
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years.