Upconversion 3D printing enables single-immersion multi-material stereolithography

• DOI: 10.1016/j.apmt.2023.101854
• Publication Date: 2023-05-29T16:54:16Z
• Authors: Adilet Zhakeyev; Mansour Abdulrhman; Yuqi Zhang; Feng Li; Guanying Chen; Jose Marques-Hueso
• Keywords: Stereolithography; Digital Light Processing; Photon Upconversion

Photopolymer 3D printing techniques have a common limitation: the layers to be deposited in sequential order, which constrains multi-material fabrication where vats exchanged many times, addition repeating cleaning step for each vat change. In this work, we present technique that allows stereolithography by overcoming layer-by-layer limitation, enabling one single immersion per resin. This is enabled selective crosslinking of voxels at any depth and position inside (SLA) resin vat. The concept uses invisibility windows upconversion achieve volumetric crosslinking. enables through previously printed parts. A photopolymer developed, visible light photoinitiator (fluorinated diphenyl titanocene) with broad absorption an optical absorber (naphthalimide class dye, maximum 445 nm) are carefully matched emissions lanthanide-doped phosphors (both micron-sized customized core/shell/shell nanoparticles). lateral resolution formulation was found 134 ± 13 µm, improved 103 11 µm light-absorbing dye. vertical defined layer thickness achieved lowering build platform, set 100 µm. NIR used excitation enhanced penetration depths up 5.8 cm, allowed SLA interwoven multi-color samples, rigid/flexible (acrylate/elastomer) samples dielectric/metallic plated samples. opens myriad new possibilities, such as objects cavities different material, restoration broken artefacts, circuitry, insitu bioprinting, etc.