It’s been a few years that volumetric 3D printing is gaining traction, but we have decided to keep a more serious look at the technology ever since some organizations have started commercializing their process. The reason for this choice seemed obvious to us; as explained in this exclusive dossier dedicated to volumetric 3D printing (from research to commercialization), there are many additive manufacturing technologies which promise a lot and deliver little.
That being said, a recently newly developed process is intriguing and ambitions to fabricate a non-crystalline, often transparent amorphous solid which is increasingly found in specialized applications such as fiber optics, consumer electronics and microfluidics for “lab-on-a-chip” devices: glass.
So far, other approaches to manufacturing glass are proven to be costly and slow (as is the case with traditional glassmaking techniques); or often deliver results in rough textures, making them unsuitable for smooth lenses (as is the case with 3D printing).
To provide a better solution to these hurdles and most importantly, in an effort to produce delicate, layer-less optics that can be built in seconds or minutes, researchers from Lawrence Livermore National Laboratory and the University of California, Berkeley have developed a new laser-based Volumetric Additive Manufacturing (VAM) approach— that could 3D-print microscopic objects in silica glass.
Nicknamed “the Replicator” after the fictional device in “Star Trek” that can instantly fabricate nearly any object, the Computed Axial Lithography (CAL) technology of this research team is inspired by computed tomography (CT) imaging methods.
In case you do not know, CAL works by computing projections from many angles through a digital model of a target object, optimizing these projections computationally, and then delivering them into a rotating volume of photosensitive resin using a digital light projector. Over time, the projected light patterns reconstruct, or build up, a 3D light dose distribution in the material, curing the object at points exceeding a light threshold while the vat of resin spins. The fully formed object materializes in mere seconds—far faster than traditional layer-by-layer 3D printing techniques—and then the vat is drained to retrieve the part.
By combining a new microscale VAM technique called micro-CAL, which uses a laser instead of an LED source, with a nanocomposite glass resin, one can obtain the production of sturdy, complex microstructure glass objects with a surface roughness of just six nanometers with features down to a minimum of 50 microns.
The team compared the breaking strength of micro CAL-built glass to objects of the same size made by a more conventional layer-based printing process, and found the breaking loads of CAL-printed structures were more tightly clustered together, meaning that researchers could have more confidence in in the breaking load of a CAL-printed components over conventional techniques, a press report reads.
“You can imagine trying to create these small micro-optics and complex microarchitectures using standard fabrication techniques; it’s really not possible,” LLNL co-author Caitlyn Krikorian Cook said. “And being able to print it ready-to-use without having to do polishing techniques saves a significant amount of time. If you can eliminate polishing steps after forming the optics—with low roughness—you can print a part ready for use.”
Real world applications could include micro-optics in high-quality cameras, consumer electronics, biomedical imaging, chemical sensors, virtual reality headsets, advanced microscopes and microfluidics with challenging 3D geometries such as “lab on a chip” applications, where microscopic channels are needed for medical diagnostics, fundamental scientific studies, nanomaterial manufacturing and drug screening. Plus, the benign properties of glass lend themselves well to biomaterials, or in cases of high temperature or chemical resistance, Cook added.
“The challenge with printing glass is that the larger the part, the more significant the shrinkage stresses are when going from a green state to burning out the binder between the silica particles into a brown part to fusing the particles together into a fully dense glass part. Cracking problems typically arise in larger prints due to these shrinkage stresses,” Cook said. “Our teams at LLNL are developing custom formulations to produce larger optics and glass printed parts that will not crack during the de-binding and sintering processes.”
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