Vat Photopolymerization

Vat Photopolymerization (VPP), a process which utilizes light to induce controlled polymerization, is the most mature of the Additive Manufacturing processes. VPP currently has four generations in terms of overall throughput innovations: stereolithography (SLA), digital light processing (DLP), continuous DLP (CDLP), and, most recently, volumetric DLP (VDLP). The DLP “generations” all utilize a spatial light modulator to induce area-wise, and later volumetric photopolymerization, rather than point-by-point laser scanning entailed in SLA. In addition to the “generational” throughput innovations, there have been important sub-generational innovations such as scanning DLP, which includes a hybrid of pattern projection and lateral scanning of the pattern projection to allow for high-resolution fabrication for larger area parts. Lastly, there have been cross-generational innovations such as multimaterial Vat Photopolymerization, which has been demonstrated in SLA, DLP, and CDLP methods. This section will explore the evolution of VPP from the point-by-point scanning methods (SLA and 2 photon polymerization) to the most recent continuous and volumetric methods. This chapter will focus primarily on each VPP generation’s respective process working principles, equations, and material considerations.