From Prototyping to High-Tech Industries: Current State and Prospects of Vat Photopolymerization

Vat photopolymerization (VPP) technologies, including stereolithography (SLA), digital light processing (DLP), and liquid crystal display (LCD) printing, have moved beyond rapid prototyping to become a full-fledged platform for the digital manufacturing of functional products over the past decade. The layer-by-layer curing of liquid photosensitive compositions under ultraviolet (UV) or near-UV radiation is the fundamental principle of these methods. This provides high spatial resolution, good surface quality, and broad geometric freedom. This review systematizes and critically analyzes current data on photopolymer 3D printing. The mechanisms of radical and cationic photopolymerization, theoretical models of curing, and rheological behavior are discussed. Typical defects arising during printing and postprocessing are analyzed. Particular attention is paid to the evolution of materials: from traditional acrylate resins to thermosetting engineering composites, elastomers, ceramic and metal suspensions, carbon nanocomposites, biocompatible hydrogels, and recyclable photopolymers with dynamic covalent bonds. Technological innovations, including multi-material printing, grayscale DLP printing, high-speed methods, and the integration of artificial intelligence algorithms, are also considered. Further progress in VPP is shown to depend on the combined optimization of resin composition, rheology, optical properties, exposure parameters, and postprocessing regimes. The key limitations remain the light scattering and absorption in filled systems, volumetric shrinkage and residual stresses, defect formation, insufficient standardization, and the fragmented nature of the available property data. Visible-range photoinitiators, closed-loop recycling, multi-material 4D printing and digital quality management are identified as promising directions.