The concept of metamaterial is a new frontier of science, encompassing physics, materials science and engineering [1]. In a broad sense, the term “metamaterial” indicates an engineered material with effective properties arising from a tailored design of its architecture, either at the nano/microscale or at the macroscale. The architecture is conceived to attain exotic properties that may not be found in nature, opening new and unforeseen opportunities especially for mechanical and acoustic applications. Furthermore, recent studies of special interest in this field are now targeting metamaterials with programmable properties in space and time, with the purpose of developing materials with multifunctional properties, including mechanical, acoustic, thermal, piezoelectric and optical. In this context, the mini-symposium aims to gather the most recent theoretical and computational studies on mechanical and acoustic metamaterials, with the purpose of stimulating a fruitful discussion among experts in this broad field. Topics covered include, but are not limited to: • Locally resonant metamaterials • Metasurfaces • Origami/kirigami-based designs • Bioinspired designs • Hierarchical designs • Multiphase metamaterials • Time-varying metamaterials • Topological metamaterials • Design, size/shape optimization, topology optimization • Fabrication processes REFERENCES [1] C. Lu, M. Hsieh, Z. Huang, C. Zhang, Y. Lin, Q. Shen, F. Chen, L. Zhang, “Architectural design and additive manufacturing of mechanical metamaterials: A review”, Engineering, Vol. 17, pp. 44-63, (2022).