A unified multiscale 3D printer combining single-photon Tomographic Volumetric Additive Manufacturing and Two-Photon Polymerization

Abstract: Photopolymerization-based additive manufacturing enables cost-effective, high-speed fabrication of complex 3D structures but is constrained by a trade-off between resolution and printing speed. Single-photon polymerization ensures rapid polymerization of centimeter-scale structures with features on the order of tens of micrometers, whereas 2PP provides sub-micrometer features at sub-millimeter scales. Here, we introduce a hybrid unified 3D printer that leverages the complementary strengths of both printing mechanisms to bridge this scale-resolution gap. We propose integrating 2PP for high-resolution, localized spatial control with single-photon TVAM for enabling rapid, high-throughput 3D fabrication. In this approach, TVAM first forms millimeter-scale volumetric structures attached on a glass rod, via overprinting, which is then accessible for subsequent high-resolution 2PP. Without needing to change the photoresin or introducing intermediate post-processing steps, we demonstrate finely printed structures via 2PP using a tightly focused femtosecond laser beam, fabricated both inside and on the surface of the millimeter-scale 3D objects printed with TVAM. Here, TVAM contributes by generating a pre-polymerized volume that facilitates subsequent 2PP and by directly driving volumetric polymerization in designated regions within seconds. We experimentally demonstrate that this dual-mode strategy provides a scalable approach for rapidly fabricating millimeter-scale 3D structures featuring sub-micrometer details. For applications like bioscaffolds and tissue engineering, tens of micrometer-scale features are sufficient across the majority of the volume with higher resolution confined to localized functional regions. For optical component manufacturing, the distinct refractive indices of the 2PP and TVAM regions can be exploited for light propagation and other micro-optical functionalities.