Using two‐step absorption instead of two‐photon absorption in 3D laser nanoprinting reduces demands on necessary laser systems but still poses a challenge for chemistry. Photoresists consisting of a photoinitiator and a viscous monomer are hardened through photopolymerization with one or two different laser sources. Until now, the influence of the photoinitiator type on printing behavior has remained unclear, limiting the rational design of new materials. In this study, we demonstrate a direct connection between molecular design and printing performance, providing new insights that guide the targeted development of novel photoinitiators. One essential parameter in designing new photoinitiators is the laser power required to initiate photopolymerization, which varies with molecular size, regioisomeric substitution, and substituent type. Screenings in this and a previous study about two‐step absorption show that, thus far, the only applicable molecules for this specific 3D printing technique are 1,2‐diketones, primarily benzil derivatives. These compounds are mainly synthesized using a Sonogashira cross‐coupling reaction followed by an oxidation of the resulting triple bond. The photoinitiators introduced in this work can be referred to as two‐step, one‐color systems, allowing 3D structures to be printed using only a single 405 nm laser source.
Vranic et al. (Thu,) studied this question.