Towards sustainable and intelligent multi-material additive manufacturing: a critical review of emerging trends, tools, and challenges

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Multi-material additive manufacturing (MMAM) prints dissimilar materials within a single build cycle, tailoring strength, conductivity, and biological response at the location-specific level and opening routes to more sustainable, consolidated products. The field, however, remains fragmented across process technologies, design tools, simulation frameworks, and certification pathways. This paper presents a critical and systematic review of MMAM organized across nine thematic domains, synthesizing 428 studies (2015 – 2026) selected through a systematic five-database search. Seven process families are classified and compared quantitatively across ten metrics covering multi-material capability, resolution, bonding mechanisms, and limitations. Design tools and digital frameworks are assessed together with material strategies and interface control: reported dissimilar-metal joints typically retain about 60–75% of the weaker constituent's tensile strength, underscoring interface integrity as the central design constraint. Multiscale simulation and predictive-modeling approaches are evaluated, and sustainability is examined through MMAM-specific life-cycle assessment, where cradle-to-gate evidence indicates up to 53% environmental-impact reduction for hybrid manufacturing routes. Hybrid manufacturing and post-processing strategies, the ISO/ASTM standards landscape, including proposed qualification criteria for biomedical and aerospace applications, and emerging applications in soft robotics, biomedical implants, aerospace structures, and electrochemical energy devices are reviewed. Critical gaps persist in standardization, computational design, and end-of-life recyclability. Future research priorities are mapped over short-, medium-, and long-term horizons, with closed-loop digital twins, interface-centred qualification, and circularity infrastructure as the defining challenges.