Lawrence Livermore National Laboratory

Sourabh Saha


Additive manufacturing (AM) generates complex, three-dimensional (3D) structures by controlling the geometry and material properties of individual building blocks. The two-photon polymerization (TPP) technique enables this level of control over sub-micrometer building blocks. Although TPP enables fabricating features on a length scale not possible with other AM techniques, it remains a niche technique limited to academic and research laboratories. Users could not take full advantage of TPP's sub-micrometer geometric control to fabricate functional 3D structures due to its low processing rate and small set of materials. Thus, there was a compelling need to increase the material processing rate and to develop custom two-photon polymerization resists.

Our project set out to design and develop the materials and equipment necessary to implement a submicrometer-scale projection-stereolithography AM system based on parallel TPP with ultrashort laser pulses. We successfully generated a parallel projection technique to increase the material processing rate by up to 1,000 times to scale up nanoscale AM. We directly measured material properties of the nanoscale features generated by TPP to enhance understanding of TPP's processing-property relationship. Finally, we generated novel photoresists for this technique to broaden the design space.

Impact on Mission

This project strengthened Lawrence Livermore National Laboratory's advanced materials and manufacturing core competencies. Our results advanced the Laboratory's laser target fabrication efforts relevant to mission challenges in high-energy-density science and stockpile stewardship and the DOE's nuclear security goal. Our work expanded DOE's goal to develop key science, technology, and engineering capabilities that modernize the national security infrastructure.

Publications, Presentations, Etc.

Ladner, I., et al. 2017. "Design of High Resolution and High Force MEMS Tensile Testers for Direct Metrology of Additively Manufactured Submicron Features." American Society for Precision Engineering 32nd Annual Meeting. LLNL-ABS-728286.

——— . 2018. "MEMS Tensile Tester for Direct Metrology of Two-Photon Polymerization Stitching." 2018 Winter Topical Meeting Precision Engineering for Micro and Nanotechnology, Livermore, CA, February 2018. LLNL-ABS-742003.

——— . 2018. "Mechanical Characterization of Additively Manufactured Microstructures Using a Process Integrated MEMS Tensile Tester." Hilton Head Workshop 2018: A Solid-State Sensors, Actuators and Microsystems Workshop, Hilton Head Island, SC, June 2018. LLNL-PROC-748753.

——— . 2019. "Tensile Properties of Polymer Nanowires Fabricated Via Two-Photon Lithography. RSC Advances 9(49):28808-13. LLNL-JRNL-765187.

Nguyen, V., et al. 2017. "Loss of Dimensional Accuracy Due To Non-Uniform Shrinkage in Additively Manufactured Polymer Parts Fabricated by Two-Photon Lithography." EUSPEN Special Interest Group Meeting: Additive Manufacturing. LLNL-ABS-730141.

——— . 2018. "Dosage Compensation for Uniform Printing with Non-Uniform Beams in Projection Two-Photon Lithography." ASPE and EUSPEN Summer Topical Meeting - Advancing Precision in Additive Manufacturing, Berkeley, CA, July 2018. LLNL-CONF-754187.

——— . 2018. "Submicron Additive Manufacturing Based on Parallel Two-Photon Lithography." 2018 ASPE and EUSPEN Summer Topical Meeting, Berkeley, CA, July 2018. LLNL-ABS-741715.

——— . 2018. "Bitmap Generation for Digital Micromirrors Used in Parallel Two-Photon Lithography." SPIE Optical Engineering + Applications Conference, San Diego, CA, August 2018. LLNL-PRES-756705.

——— . 2018. "Scalable Submicron Additive Manufacturing Based on Parallel Two-Photon Lithography." 2018 MRS Spring Meeting and Exhibit, Phoenix, AZ, April 2018. LLNL-ABS-740672.

——— . 2018. "Parallel Two-Photon Lithography with Sub-Diffraction Voxel Shaping." Solid Freeform Fabrication 2018: Proceedings of the 29th Annual International Solid Freeform Fabrication Symposium, Austin, TX, August 2018. LLNL-ABS-749365.

Oakdale, J., et al., 2016. "Radiopaque Resins for Two Photon Polymerization." Nanoscribe User Mtg., Harvard University, Cambridge, MA, June 2016. LLNL-PRES-695322.

Saha, S. K., et al. 2018. "Parallel Two-Photon Lithography for 3D Printing of Millimeter Scale Parts with Submicron Features". SPIE Photonics West Exhibition 2018, San Francisco, CA, February 2018. LLNL-ABS-734909.

——— . 2018. "Radiopaque Resists for Two-Photon Lithography to Enable Submicron 3D Imaging of Polymer Parts Via X-ray Computed Tomography." ACS Applied Materials and Interfaces 10(1): 1164-1172. doi: 10.1021/acsami.7b12654. LLNL-JRNL-732780.

——— . 2019. "High-Speed Direct Laser Writing of Silver Nanostructures via Two-Photon Reduction." Advanced Engineering Materials 21(9):1900583. LLNL-JRNL-773864.

——— . 2019. "Scalable Submicrometer Additive Manufacturing." Science. 366(6461):105. LLNL-JRNL-770497.