Electron beam processing of organic ice for low-toxicity submicrometer additive manufacturing

Two-photon lithography enables powerful nanoscale 3D printing. Unfortunately, it uses toxic photopolymers. We report a layer-by-layer digital process using condensed organic vapor thin films as the starting material. The process uses a focused electron beam to chemically cross-link the low-toxicity organic ice ito a solid and shares software and CAD databases with industrial 3D printing. Guided by electron-matter-interaction simulations, we control the cross-linking thickness between 250 nm and 2 mu m. The 3D prints contained up to 500 layers, and the voxel size is about 550-nm. In addition to more sustainable materials, our digital process complements twophoton lithography in three areas; (i) it is compatible with chemistry beyond photopolymers, (ii) we can print delicate suspended structures and tubes because our structures are not immersed in liquid resins that reside in cavities and destroy structures by interfacial forces, (iii) free-hanging structures are printed without sacrificial supports. Nanophotonics and microfluidics applications are demonstrated.