Recent Advances in Additively Manufactured Auxetic Metamaterials

Mechanical metamaterials achieve unusual mechanical responses through carefully designed architectures rather than relying solely on the intrinsic properties of constituent materials. Among them, auxetic metamaterials, which exhibit a negative Poisson’s ratio, have attracted increasing attention because of their distinctive deformation mechanisms and potential advantages in lightweight design, energy absorption (EA), impact resistance, and biomedical devices. Additive manufacturing (AM) provides an effective route for fabricating complex auxetic architectures with controllable geometry; however, the realized mechanical performance is strongly affected by structural topology, material selection, printing process, loading mode, and measurement method. This review provides a structured overview of recent advances in additively manufactured auxetic metamaterials. Representative auxetic configurations are first summarized, including reentrant, chiral, rotating-unit, origami- and kirigami-inspired, perforated, textile, and emerging hybrid structures. The main AM routes used for auxetic metamaterials are then discussed, with attention to both their fabrication advantages and process-related limitations. Particular emphasis is placed on the relationship among architecture, manufacturing route, and mechanical performance, including Poisson’s ratio, lightweight characteristics, EA, impact resistance, programmability, and biomedical adaptability. In addition, comparability issues among different studies are discussed, including differences in strain range, loading mode, material system, specimen scale, measurement method, and validation method. Finally, current challenges and future research directions are outlined, with a focus on manufacturing fidelity, standardized testing, fatigue and damage tolerance, multi-material and functionally graded design, and application-oriented validation.