Radical inhibition in tomographic volumetric 3D printing for thiol-Ene photoresists: From Photorheology to printability

The introduction of tomographic volumetric 3D printing is revolutionizing the manufacturing and bioprinting landscape by enabling the rapid creation of complex three-dimensional (biological) structures with high precision down to 20 μm. Despite the recognized role of radical inhibition in volumetric 3D printing, a study of inhibition has remained elusive. Here, A comprehensive framework is presented to study the role of the widely reported radical inhibitor TEMPO in the volumetric 3D printability of a thiol-ene photocrosslinkable photoresist composed of triallyl isocyanurate (TTT) and pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). Through photorheological measurements, kinetic modeling, FTIR spectroscopy, and validation via volumetric 3D printing, the relationship between inhibitor concentrations, the evolution of the shear moduli as well as the conversion as a function of light dose, and volumetric 3D printing is elucidated. The findings in this study provide a robust methodology for predicting optimal printing conditions of photoresists for tomographic volumetric 3D printing, obviating the need for extensive trial-and-error.