Green Light Vat-Photopolymerisation for 3D Printing Hydrogels with Complex Lattice Structures

Abstract

Moving beyond UV curing systems opens new potential application spaces such as biological, portable printing solutions, as well as innovative chemistries and material properties. A novel visible light printer is proposed for the first time using green Digital Light Processing (gDLP) at a wavelength of 514 nm. Green LED lights are integrated into a commercial desktop DLP printer to 3D print hydrogels with complex designs at high resolution. A workflow process is presented to develop and optimize formulations for gDLP, resulting in two novel in-house photoresin formulations made specifically for green light printing. These formulations comprise ${\mathrm{PEGDA}}_{700}$ with and without acrylamide, using a type II photoinitiating system of Eosin Y, triethylamine, and N-vinylpyrrolidone. The photoresins are optimized to achieve highly vascularized lattice prints by modulating layer light exposure, chemical components, and photoinitiator concentrations. The gDLP successfully printed hydrogels with a layer height of 50 $\mu m$ and feature dimensions as small as 0.3 mm by adjusting light duration per layer. 3D printed hydrogels using both formulations are tested for varying design complexity, including ISO/ASTM standards, and evaluated with optical imaging, SEM, and mechanical testing. This study highlights gDLP technology's potential for diverse applications in tissue engineering and sustainable materials.