Additive manufacturing of metastructures at the micro- and nano-scale

The emergence of additive manufacturing techniques offers more opportunities for fabricating complex structures with designed properties that are challenging to achieve using traditional manufacturing methods. Micro-/nano-scale metastructures are among the most promising applications of additive manufacturing and are composed of meta-atoms at the subwavelength scale with artificial design, which enables the creation of materials and structures with tailored and programmable properties that go beyond the limitations of their natural and traditional counterparts. This review depicts the thriving intersection of state-of-the-art additive manufacturing and micro-/nano-scale metastructures, such as metamaterials, metasurfaces, etc., aiming to provide a comprehensive overview of current achievements and explore future potential. An array of additive manufacturing techniques are discussed, such as electrohydrodynamic printing, two-photon lithography, and aerosol jet printing, which are reshaping the fabrication of metastructures with unprecedented structural design and functional diversity. Furthermore, the selection of the materials based on fabrication principles and device functions is considered. The diverse applications based on different metastructures are highlighted. Finally, this review is concluded by discussing the current challenges and giving future perspectives.