Fig. 1 Jason Laurea/LLNLL
A new 3D-printing technique developed at Lawrence Livermore could let technicians print glass that incorporates different refractive indices in a single flat optic, making finishing cheaper and easier.

Lab Scientists Successfully Print Glass Optics

Researchers at Lawrence Livermore National Laboratory (LLNL) have successfully 3D printed optical-quality glasses, on par with commercial glass products currently on the market. They have produced small test pieces from Lab-developed ink with properties “within range of commercial optical grade glasses.” 

Because the refractive index of glass is sensitive to its thermal history, it can be difficult to ensure that glass printed from molten glass phase will result in the desired optical performance. The LLNL team overcame these difficulties by having the printer deposit the material in paste form and then heating the entire print to form the glass, giving it a uniform refractive index and eliminating optical distortion that would degrade the optics.

“Components printed from molten glass often show texture from the 3D printing process, and even if you were to polish the surface, you would still see evidence of the printing process within the bulk material,” says LLNL chemical engineer Rebecca Dylla-Spears, the project’s principal investigator. “Using paste lets us obtain the uniform index needed for optics. Now we can take these components and do something interesting.”

LLNL researchers (shown are LLNL chemical engineer and project lead Rebecca Dylla-Spears and LLNL materials engineer Du Nguyen ) have used 3D printing to make transparent glass components using a “slurry” of silica particles extruded through a direct-ink writing process.

The custom inks, aimed at forming silica and silica-titania glasses, let researchers tune the glass’ optical, thermal, and mechanical properties. Although the researchers printed small, simple-shaped optics as proof of concept, the technique eventually could be applied to any device that uses glass optics; it could potentially create optics made with geometric structures and with compositional changes unattainable by conventional manufacturing methods. For example, gradient refractive index lenses could be polished flat, replacing more expensive polishing techniques used for traditional curved lenses.

“Additive manufacturing gives us a new degree of freedom to combine optical materials in ways we could not do before,” says Dylla-Spears. “It opens up designs that haven’t existed in the past, allowing for design of both the optic shape and properties within the material.”

The LLNL team is now mixing and patterning different material compositions in hopes of getting control over material properties and making gradient refractive index lenses. LLNL has filed a patent on the technique and already is receiving interest from large-scale glass manufacturers.

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