Xolography for linear volumetric 3D printing

The range of applications for additive manufacturing is expanding quickly, including mass production of athletic footwear parts¹, dental ceramics² and aerospace components³ as well as fabrication of microfluidics⁴, medical devices⁵, and artificial organs⁶. The light-induced additive manufacturing techniques⁷ used are particularly successful owing to their high spatial and temporal control, but such techniques still share the common motifs of pointwise or layered generation, as do stereolithography⁸, laser powder bed fusion⁹, and continuous liquid interface production¹⁰ and its successors^11,12. Volumetric 3D printing^13-20 is the next step onward from sequential additive manufacturing methods. Here we introduce xolography, a dual colour technique using photoswitchable photoinitiators to induce local polymerization inside a confined monomer volume upon linear excitation by intersecting light beams of different wavelengths. We demonstrate this concept with a volumetric printer designed to generate three-dimensional objects with complex structural features as well as mechanical and optical functions. Compared to state-of-the-art volumetric printing methods, our technique has a resolution about ten times higher than computed axial lithography without feedback optimization, and a volume generation rate four to five orders of magnitude higher than two-photon photopolymerization. We expect this technology to transform rapid volumetric production for objects at the nanoscopic to macroscopic length scales.