Chemical Optimization Strategy of Rapid Additive Manufacturing via Up‐Conversion Assisted Photopolymerization Based Direct Ink Writing

Abstract Light‐driven 3D printing can empower the liberty of creation and concretize the original creation in versatile conditions with plenty of choices in resolution or properties. However, photopolymerization‐based 3D printing inks are facing a trade‐off between requiring processing rate and satisfying performance, and a chemical optimization strategy is proposed to achieve the ink demands of rapid direct ink writing utilizing up‐conversion assisted photopolymerization. Since acylphosphonate can generate two reactive radicals and tertiary amine can reinitiate polymerization in oxygen inhibition, the yielded active species in limited irradiation of 3D printing are maximized to accelerate the polymerization by theoretically and experimentally interpreting the roles of up‐conversion particle, photoinitiators, and co‐initiator played in printing. High print speed in depositing and in situ curing (3.56 × 10⁴ mm³ h⁻¹) are realized, and the manufacturing time is shortened by multi‐resolution printing which is impressive compared to current 3D printing methods. The strategy is simultaneously compatible with rigid and elastomeric materials, and will surely contribute to other light‐driven 3D printing technologies for extensive applications.