Multiscale Hybrid Fabrication: Volumetric Printing Meets Two-Photon Ablation

Multiscale printing of 3D perfusable geometries holds great potential for a range of applications, from microfluidic systems to organ-on-a-chip. However, the generation of freeform designs spanning from centimeter to micrometer features represents an unmet challenge for a single fabrication method and thus may require the convergence of two or more modalities. Leveraging the great advances in light-based printing, herein a hybrid strategy is introduced to tackle this challenge. By combining volumetric printing (VP) and high-resolution two-photon ablation (2PA), the possibility to create multiscale models with features ranging from mesoscale (VP) to microscale (2PA) is demonstrated. To successfully combine these two methods, micrometer-size defects generated during the VP process due to optical modulation instability and self-focusing phenomena are first eliminated. By optical tuning the refractive index of the photoresin, defect-free VP that can then be combined with 2PA is demonstrated. To facilitate the 2PA process and meet VP requirements, a purely protein-based photoclick photoresin combining gelatin-norbornene and gelatin-thiol is introduced. Finally, the possibility to generate complex organotypic 3D vasculature-like constructs with features ranging from approximate to 400 mu m of VP to approximate to 2 mu m of 2PA is demonstrated. This hybrid strategy opens new possibilities for multiscale printing, with particular potential for microfluidics and organ/tissue-on-a-chip technologies.