Multi-material VAT photopolymerization toward integrated functional devices

VAT photopolymerization (VPP) has emerged as a leading additive manufacturing platform for the fabrication of complex three-dimensional structures with high spatial resolution and throughput. Extending VPP toward multi-material fabrication enables the spatial encoding of distinct chemical compositions and functional properties within a single printed object, opening new opportunities in soft robotics, bioelectronics, tissue engineering, smart materials, and, more broadly, integrated functional devices. This review examines the principal strategies developed for multi-material VPP, which can be broadly classified into hardware-driven approaches, including VAT-switching systems and dynamic resin delivery platforms, and chemistry-driven single-VAT approaches based on orthogonal photopolymerization. For each strategy, we discuss the underlying working principles, material requirements, representative implementations, and key limitations, including cross-contamination, interfacial incompatibility, and restricted wavelength orthogonality. Hybrid and process-driven methodologies, including extrusion–light integration, magnetic field-assisted printing, and temperature-modulated photopolymerization, are also explored as complementary routes toward enhanced functional complexity. Finally, we discuss the remaining challenges and future perspectives for translating multi-material VPP from laboratory-scale demonstrations into scalable and industrially relevant manufacturing platforms.