Designer Metasurfaces\nvia Nanocube Assembly at the\nAir–Water Interface

The advent of metasurfaces has revolutionized the design\nof optical\ninstruments, and recent advancements in fabrication techniques are\nfurther accelerating their practical applications. However, conventional\ntop-down fabrication of intricate nanostructures proves to be expensive\nand time-consuming, posing challenges for large-scale production.\nHere, we propose a cost-effective bottom-up approach to create nanostructure\narrays with arbitrarily complex meta-atoms displaying single nanoparticle\nlateral resolution over submillimeter areas, minimizing the need for\nadvanced and high-cost nanofabrication equipment. By utilizing air/water\ninterface assembly, we transfer nanoparticles onto templated polydimethylsiloxane\n(PDMS) irrespective of nanopattern density, shape, or size. We demonstrate\nthe robust assembly of nanocubes into meta-atoms with diverse configurations\ngenerally unachievable by conventional methods, including U, L, cross,\nS, T, gammadion, split-ring resonators, and Pancharatnam–Berry\nmetasurfaces with designer optical functionalities. We also show nanocube\nepitaxy at near ambient temperature to transform the meta-atoms into\ncomplex continuous nanostructures that can be swiftly transferred\nfrom PDMS to various substrates via contact printing. Our approach\npotentially offers a large-scale manufacturing alternative to top-down\nfabrication for metal nanostructuring, unlocking possibilities in\nthe realm of nanophotonics.