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Refractive index matched polymeric and preceramic resins for height-scalable two-photon lithography
Magi Mettry1, Matthew A Worthington1, Brian Au2
1Materials Science Division, Lawrence Livermore National Laboratory 7000 East Ave. Livermore CA 94550-5507 USA oakdale1@llnl.gov.
RSC Advances
|April 28, 2022
Summary
Direct laser writing via two-photon polymerization (DLW-TPP) can now create taller 3D microstructures. New refractive index-matching methods enable fabricating complex nanoscale features in resins up to 2.5 mm high.
Area of Science:
- Materials Science
- Nanotechnology
- Additive Manufacturing
Background:
- Direct laser writing via two-photon polymerization (DLW-TPP) is a key nanofabrication technique for 3D structures.
- A major limitation of DLW-TPP is the restricted build height, typically under 1 mm, due to laser focusing constraints.
- Achieving precise refractive index matching between the photopolymer and surrounding medium is crucial for overcoming height limitations but lacks standardized methods.
Purpose of the Study:
- To develop and validate universal methods for creating refractive index-matched polymeric and preceramic resins for DLW-TPP.
- To investigate the impact of refractive index mismatch on voxel shape and printing fidelity.
- To extend DLW-TPP capabilities for fabricating taller 3D structures with nanoscale features, including novel preceramic materials.
Main Methods:
- Two universal approaches were tested: mixing commercially available resins and covalent modification of functional monomers to achieve refractive index matching.
- The performance of these index-matched resins was demonstrated by printing fine submicron features in 3D structures.
- The study explored the relationship between voxel shape and refractive index mismatch and applied index tuning to preceramic resins.
Main Results:
- Successfully fabricated 3D structures up to 2.5 mm in height with nanoscale features using refractive index-matched resins.
- Demonstrated the effectiveness of both resin mixing and covalent modification for achieving precise refractive index matching.
- Successfully printed 3D silicon oxycarbide structures from preceramic resists, overcoming the conventional height limitations of DLW-TPP.
Conclusions:
- Developed and validated practical methods for refractive index matching in DLW-TPP, significantly expanding achievable build heights.
- Showcased the material flexibility of DLW-TPP by successfully fabricating complex 3D structures from preceramic resins.
- This work removes a critical barrier in nanofabrication, enabling larger and more complex 3D micro- and nanostructures for diverse applications.
