Acrylate‐Epoxy Interpenetrating Polymer Networks for High‐Resolution 3D Lithography by Two‐Photon Polymerization

Multifunctional acrylate monomers are widely used in two‐photon polymerization (TPP) for fabricating 3D micro‐ and nanostructures. However, their limited mechanical properties, such as stiffness and adhesion, restrict high‐resolution 3D structuring and practical applications in complex environments. Epoxy‐based resins, known for their high Young's modulus, are introduced into TPP to address these limitations, though their cationic polymerization often reduces spatial resolution. In this study, we combine the high spatial resolution of acrylates with the mechanical strength of epoxy resins to form interpenetrating polymer networks (IPNs) via TPP. A photoinitiating system based on photoredox catalysis, including a copper complex, iodonium salt, and N‐vinylcarbazole, mixed with a triacrylate monomer and a cycloaliphatic epoxy resin, triggers both radical and cationic polymerization upon two‐photon excitation with a 780 nm femtosecond laser. The spatial resolution and mechanical properties of the resulting IPN structures are evaluated, focusing on the role of epoxy resin, the Young's modulus, and the deformation issue of the 3D polymerized structures. The results show significant improvements in mechanical performance while maintaining high spatial resolution. The fabricated 1D and 3D polymer structures exhibit feature sizes below 80 nm and periodicities down to 300 nm, demonstrating strong potential for advanced nanofabrication applications.