Additively manufactured rigid-flexible metamaterials for advanced sound control

Additive manufacturing opens promising perspectives for realizing acoustic metamaterials to control sound in multiple application scenarios. Especially attractive are hybrid flexible-rigid 3D-printed metastructures as they combine the advantages of rigid designs (e.g., load-bearing performance) and an increased number of structural degrees of freedom owing to flexibility. Here, we discuss the potential of 3D-printed flexible plastics and resins for extending the absorption functionality of hybrid acoustic metasurfaces to broadband low-frequency regimes and achieving switchable absorption in flexible lattice acoustic metamaterials. Besides, we show how metamaterial patterns can control sound generated by flapping flexible wings. The proposed metastructures are studied numerically, manufactured by means of FDM or SLA 3D printing, and tested in the lab.