Glass Inks for Three-Dimensional Printed Fiber Preforms and Telescope Optics

Project Overview

Access to glass with tailored composition unlocks a new degree of freedom for designers and could impact the size, weight, and power (SWaP) of national security-related optical systems, including telescopes and fiber lasers. Lawrence Livermore National Laboratory (LLNL) has established itself as a pioneer in the field of three-dimensional (3d) printed glasses, developing a two-stage process first to print a low-density silica structure by the direct ink writing (DIW) 3D-printing technique, and then to sinter the printed structure to fully dense glass via heat treatment. Our approaches for this in DIW additively manufactured glasses study covered (1) investigations into the mass transport mechanisms of common dopants in DIW-produced glass; (2) formulation of printable high index inks glass compositions; (3) preparation of gradient index (GRIN) optic with high index inks; (4) development of printable oxopolymer glass inks; (5) production of fiber preforms (particle based); and (6) a study of the impact of low viscosity UV-curable glass inks on component homogeneity. Through study of these individual aspects, we gained understanding of the process from inks' compositions to 3D printing and heat treatment challenges for 3D printed glass. This effort has firmly established LLNL as the leader in 3D printing of multi-composition glasses optics and to encourage future business from LLNL's national security sponsors. The project generated intellectual property associated with graded optical component fabrication and design and advanced LLNL's core competencies in Laser & Optical Science & Technology as well as Advanced Materials and Manufacturing.

Our glass 3D printing efforts focused on demonstrating that homogeneous glass was possible using DIW and then in developing glass ink precursors that would result in higher refractive index (n) glass for printing high index change (Δn) GRIN optics. Ink formulations were successful in yielding uniform composition optics with higher index than fused silica (n_silica + 0.1) while maintaining optical quality homogeneity. The project produced successful GRIN optics with up to Δn <0.05 for a 1 cm diameter lens. We were unable to expand the GRIN optics to cover the full 0.1 span during this project. This is largely due to the recently discovered phenomenon in our existing DIW mixing system that mixing two materials with rapid time-varying changes in flow rates significantly alters the resulting material homogeneity, even when the same two inks printed with constant flow rates yields homogeneous material. Therefore, a new LDRD effort will pursue resolving this challenge--Agile Mixing Platform Engineered for Transient Compositional Printing (AMPLE 22-ERD-012). Separately, the project also developed multiple, printable Nd-doped silica formulations and methods by which to consolidate them to form glass preforms. Due to bubble formation during fiber draw at high temperature, no fibers had been formed by the conclusion of the project. Efforts to reduce foaming yielded a substantial reduction in bubbles generated during fiber pulls, but work remains to eliminate gases that may be trapped interstitially during the printing process.

Mission Impact

This project strengthens LLNL's core competencies in Laser and Optical Science and Technology as well as in Advanced Materials and Manufacturing. We have driven development of 3D-printed, tailored composition glass optics and firmly established LLNL as the leader in this arena. The effort results in new silica-based DIW ink formulations for glasses and in greater understanding of the thermal and chemical processing techniques required for improving printed glass quality. We have produced 3D-printed optics such as fiber preforms and GRIN telescope elements that are anticipated to be enabling for future national security missions.

Publications, Presentations, and Patents

D. T. Nguyen et al., "3D Printing of Compositional Gradients Using the Microfluidic Circuit Analogy," Adv. Mater. Technol., vol. 4, no. 12, p. 1900784, Dec. 2019, doi: 10.1002/admt.201900784.

K. Sasan et al., "Additive Manufacturing of Optical Quality Germania-Silica Glasses," ACS Appl. Mater. Interfaces, vol. 12, no. 5, pp. 6736-6741, Feb. 2020, doi: 10.1021/acsami.9b21136.

R. Dylla-Spears et al., "3D printed gradient index glass optics," Sci. Adv., vol. 6, no. 47, p. eabc7429, 2020.

Dylla-Spears, R., Invited Perspective, "Preshaping clear glass at low temperatures," Science 2021, 372, 6538.

N. Dudukovic, R. Dylla-Spears, M. Ellis. System and method for direct electroless plating of 3D-printing glass for selective surface patterning. (Filed in September 2021.)