Three-dimensional direct-writing via photopolymerization based on triplet-triplet annihilation

3D direct-writing via photopolymerization based on two-photon absorption(TPA) can achieve excellent out-of-plane resolution.The key to this technology is a quadratic intensity dependence in photoexciting the TPA photosensitizers. Triplet-triplet annihilation(TTA) also has similar nonlinear light-intensity dependence. As a result, TTA can also generate spatially confined excitation near the beam focus. Combining the photopolymerization reaction with the TTA system composed of palladium porphyrin and diphenylanthracene, 3D direct-writing micro-fabrication based on photopolymerization and the TTAwas realized.The out-of-plane resolution can reach 10 μm under continuous-wave laser excitation. TTA-based 3D direct-writing technology does not need an expensive femtosecond pulsed laser, showing the potential of a next-generation 3D printing technology.