Two‐Photon Printing of Base‐Catalyzed Resins Involving Thiol‐Michael Network Formation

Two‐photon printing is accomplished using a photobase generator, 2‐(2‐nitrophenyl)‐propyloxycarbony tetramethyl guanidine, to locally catalyze thiol‐ene coupling between multifunctional monomers while mitigating chain‐growth polymerization with free radical scavengers. Microstructures printed from base‐catalyzed resins exhibit higher resolution (linewidths < 400 nm) and lower print error (<3%) than analogous microstructures printed using a photosensitive, free radical initiator. Further, Raman spectroscopy reveals that resins polymerized using the photobase generator in the presence of free radical scavengers exhibit higher selectivity of thiol‐ene coupling over radical polymerization, resulting in stiffer, more uniform polymer networks. The base‐catalyzed resins are capable of producing 3D microstructures printed with high accuracy and minimal post‐processing defects. A direct comparison between free radical and base‐initiated resins highlights the need for mindful consideration of how chemical reaction pathway influences printability and network end‐properties when designing resins.