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From Hologram to Reality, 3D Printing with Light

Posted by Lisa Harvey,

Today’s post is from guest blogger, Nicole Mosher. Nicole works on the technical articles team and sees many cutting-edge research projects in her role. This week, she’s sharing one of her recent favorites.

3D printing is a relatively new technology that has captured users’ interest. The process is simple but can be time-consuming; it requires layering filaments upon each other to create a 3D structure. These filaments are typically polymers, but can also be metals, glass, paper, wood or even gel. The result is a 3D object, often with rough edges created by the layering technique.

But what if, instead of creating an object by applying layer after layer of filaments, you could make one materialize like a hologram, turning liquid into a solid object? What if you could print perfectly smooth objects, objects that encased existing items, or structures that flex and bend?

That was a challenge new research from Lawrence Livermore National Laboratory and the University of California Berkeley took on. The team’s work was published in the academic journal, Science.

 

Image Credit: UC Berkeley

 

This new approach creates a visual display that is the stuff of sci-fi films. The printer has fittingly been named “The Replicator” after the Star Trek device which could materialize items out of thin air. The Replicator, however, materializes objects out of a jar of liquid instead.

According to The Washington Post, “The new approach — known as Computer Axial Lithography (CAL) — carves an object out of a synthetic resin that solidifies when it comes into contact with particular patterns and intensities of light.”

Building an entire object at once 

According to the researchers, the Replicator is several orders of magnitude faster than layer-by-layer methods. Ironically, The Replicator’s inspiration begins with a technology we’d be least likely to associate with haste—a computed tomography (CT) scanner.

CT scanners take quite some time to create the detailed 3D images that doctors rely on for treatments like pinpoint-precise radiation therapy in cancer patients. They take hours, partially because they are building these images piecemeal out of a multitude of 2D images to create complex images of the human body.

 

UC Berkeley. (A) Images taken from each angle, similar to CT scan. (B) System diagram of Replicator. (C) Time-lapse shows object completed in less than one minute. (D-F) Various 3D versions after uncured materials are washed away. Image Credit: Taylor et al.

 

The Replicator reverses this process. An image of a 3D object is uploaded to a computer program, which breaks the image down into 2D slivers. Much like an old-fashioned film, these slivers are strung together into a video sequence, resulting in footage of the object rotating.

This film is then projected through a vial of photo-sensitive gel, which rotates as well. The rotations occur in sync so that the images align to create what appears to be a hologram of the object. The projection systems are controlled via custom MATLAB scripts and programmed to output patterned images using the relevant color wavelength and intensity determined by the architectural makeup of the object.

 

Image Credit: UC Berkeley

 

It is here that light plays a role in the building process. The projected rotating image is effectively a blueprint. As photons pass through the rotating vial, they collide with each other at certain points, hardening at each point of collision. Where photons pass through the gel unobstructed, no hardening occurs.

“As the container rotates, the pattern that’s projected changes, so over time the amount of light that each point receives can be controlled,” Dr. Hayden Taylor, assistant professor at the University of California at Berkeley explained to The Guardian, “Spots that receive a lot of light solidify, while those that do not remain liquid.”

So, for instance, using an image of a teacup, photons would collide and harden at the areas where the handle and body of the cup should be, and nowhere else. Once the liquid was drained from the vial, the object remains behind.

Advantages over current 3D printing technology 

For now, the Replicator has only been used to create small-scale objects. In the images above, the Replicator created a miniature version of Rodin’s sculpture, The Thinker, standing just four centimeters tall. The replica showcases some of the features that were previously unavailable with 3D printing: It is entirely smooth because of the lack of layering during construction eliminates stair-like ridges.

Even more impressive, “[The Replicator creates] almost no material waste and the uncured material is 100 percent reusable,” according to Hossein Heidari, UC Berkeley graduate student and co-author of the paper.

Unlike traditional 3D printers, the Replicator can encase existing objects during the building process, as well as build structurally diverse objects like bendable objects, or structures that normally require arches. Building from all angles simultaneously eliminates many of the product design obstacles in previous 3D printers.

 

Image Credit: Taylor et al. UC Berkeley

 

The UC Berkeley researchers goal for the CAL approach is to create custom objects for commercial purposes. The approach could be particularly beneficial for producing prosthetics or dental devices. Taylor also believes it quite possible to scale this printing method to create larger objects in the near future.

The CAL methodology may just be the next breakthrough in 3D printing. To learn more, check out the video below: