Metasurface‐Enabled Holographic Lithography for Impact‐Absorbing Nano‐Architected Sheets

Abstract

Nano-architected materials represent a class of structural meta-materials that utilze nanoscale features to achieve unconventional material properties such as ultra-low density and high energy absorption. A dearth of fabrication methods capable of producing architected materials with sub-micron resolution over large areas in a scalable manner exists. We present a fabrication technique that employs holographic patterns generated by laser exposure of phase metasurface masks in negative-tone photoresists to produce 30 to 40 micrometer thick nano-architected sheets with 2.1 x 2.4 cm² lateral dimensions and approximately 500 nm wide struts organized in layered 3D brick-and-mortar-like patterns to result in approximately 50 to 70% porosity. Nanoindentation arrays over the entire sample area reveal the out-of-plane elastic modulus to vary between 300 MPa and 4 GPa, with irrecoverable post-elastic material deformation commencing via individual nano-strut buckling, densification within layers, shearing along perturbation perimeter, and tensile cracking. Laser induced particle impact tests (LIPIT) indicate specific inelastic energy dissipation of 0.51-2.61 MJ kg⁻¹, which is comparable to other high-impact energy absorbing composites and nanomaterials, such as Kevlar/polyvinyl butyral (PVB) composite, polystyrene, and pyrolized carbon nanolattices with 23% relative density. These results demonstrate that holographic lithography offers a promising platform for scalable manufacturing of nano-architected materials with impact resistant capabilities.