Influence of a non-reactive additive on the photocuring and 3D-VAT printing processes of PEGDA: Complementary studies

Abstract

Photopolymerization processes are currently-one of the key methods for obtaining functional materials, and the possibility of applying this processes to additive technologies opens up new opportunities, especially for the medical market. 3D-VAT printing, including techniques such as digital light processing (DLP) and stereolithography (SLA), makes it possible to obtain materials with the desired geometry, high optical resolution and rapid layer-by-layer production time, which was not previously possible with classical techniques used in biomedicine. Therefore, understanding the fundamental relationships between the components of photosensitive compositions, including the initiator, monomer/oligomer and additives, is crucial to the applicational success of bioprinting. Hence, this paper investigates the effect of a non-reactive additive to the bioresin on the photopolymerization process both in situ and in 3D-VAT printing. The following components were selected as the model system for the study: poly(ethylene glycol) diacrylate (PEGDA), lithium phenyl-2,4,6-trimethylbenzoylphosphinate (TPO-Li), and as an unreactive ingredient – water, in varying amounts. This paper presents a comprehensive research procedure using different techniques: real-time FTIR, photo-DSC and photo-rheology, to precisely quantify the relationship: kinetic of the photopolymerization process/shrinkage of the material vs the amount of non-reactive additive. The possibility of using the investigated bioresins to create three-dimensional materials was also studied. The materials, obtained by 3D-VAT printing using DLP technology, were compared in terms of the achieved optical resolution and polymer shrinkage.