Deciphering the Photopolymerization-Induced Nanostructures and Interface Formation for Submicrometer Additive Manufacturing

Ultraviolet (UV) light-induced curing is widely used in additive manufacturing and coatings. However, the formation and heterogeneous distribution of nanostructures induced by UV‑curing remain unclear, especially in submicrometer films where nanoscale precision is critical. We employ a combination of UV-curing and X-ray scattering to gain access to the nanoscale kinetics during UV-curing inside the resin films used for additive manufacturing. We show that the heterogeneous distribution stems from monomer‑rich and oligomer‑rich nanodomains in solvent‑based UV‑curable resins. We further reveal how these nanodomains interact with subsequently deposited resin to form nanoscale buried interfaces using grazing incidence small-angle X-ray scattering. By introducing stressed-state and relaxed-state films based on substrate constraint, we explain the formation of buried frozen nanowrinkles in bilayer systems. Using relaxed-state films, we identify non‑diffused, diffused, and semi‑diffused interlayer interfaces from oligomer‑rich domain interactions. This work systematically elucidates the formation mechanisms and types of interlayer nanostructures in UV‑curing based submicrometer additive manufacturing, paving the way for polymer-based additive manufacturing with nanoscale precision resolution.