New 3D Printer Uses Ray of Light to Shape Complex Objects

A 3D printing technique from UC Berkeley shapes objects all at once rather than layer by layer, allowing for more complex and smooth objects.

A new light-based 3D-printing approach and machine can fabricate complex objects in minutes that are smoother and more flexible than what’s currently possible. Dubbed the “replicator”—a reference to the Star Trek television program—and developed by researchers at UC Berkeley, the printer uses a ray of light to transform liquids into objects all at once rather than layer by layer, which is how typical 3D printers create objects. The replicator was a device on the famous program that would materialize any object on demand.

UC Berkeley researchers used a new light-based 3D-printing technique to add a handle onto a screwdriver shaft. The technique builds objects all at once rather than layer by layer, allowing for more diversity of object design and fabrication. (Image source: Stephen McNally/UC Berkeley)

Encasing Existing Objects

In addition to creating brand new objects, the printer also can encase an existing object with new materials, which is difficult to do with current 3D printers and methods, researchers said in a UC Berkeley news release.

The team—led by Hayden Taylor, assistant professor of mechanical engineering at UC Berkeley—believes its work has the potential to transform the design and fabrication of numerous products, from prosthetics to eyeglass lenses to running shoes, he said.

“The fact that you could take a metallic component or something from another manufacturing process and add on customizable geometry, I think that may change the way products are designed,” Taylor said, adding that the technique can lead to mass customization of objects.

No More Stair-Step Effect

A layer-by-layer approach to building objects leads to what researchers refer to as a “stair-step” effect along the edges. It’s also not very conducive to fabricating flexible objects because bendable materials likely deform with this type of process and is limited in the type of shapes that can be easily fabricated. For example, arches would need supports to maintain their shape in traditional 3D-printing methods.

The 3D printer developed by the UC Berkeley team is unique in that it uses a viscous liquid that reacts to changing patterns of light shined on it as it rotates in a vial. The team developed a computer algorithm to calculate the exact patterns of light needed to shape a specific object, Taylor said.

“Basically, you’ve got an off-the-shelf video projector, which I literally brought in from home, and then you plug it into a laptop and use it to project a series of computed images, while a motor turns a cylinder that has a 3D printing resin in it,” he explained.

Barriers Are Not High

Taylor acknowledged that the process has specific parameters in terms of how the resin is formulated, for example, but basically relies on how researchers compute the images that are going to be projected. “The barrier to creating a very simple version of this tool is not that high,” he said.

The resin the team used in the printer is composed of liquid polymers mixed with photosensitive molecules and dissolved oxygen Light activates the photosensitive compound, which depletes the oxygen, leaving polymers to form cross-links that turn the resin from liquid to solid in the regions where the oxygen has been used.

Researchers used the printer to create a series of objects—up to four inches in diameter—from a tiny model of Rodin’s “The Thinker” statue to a customized jawbone model. The team published a paper on their work in the journal Science.

The technology has other benefits besides it fabrication flexibility, researchers said. It generates almost no material waste, and uncured material is 100 percent reusable.

The objects also don’t have to be transparent, which the team demonstrated by using a dye that transmits light at the curing wavelength but absorbs most other wavelengths to create objects that appear opaque.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

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