Direct printing of metasurfaces using formulated optical materials.

Optical metasurfaces represent a promising technology for compact, lightweight and multifunctional optical devices; yet, their practical implementation remains challenging because of the need for high-refractive-index (high-index) materials, complex fabrication processes and limited substrate compatibility. Conventional top-down approaches relying on deposition, electron-beam lithography and etching are expensive and typically restricted to rigid substrates, hindering scalability and integration with flexible platforms. Nanoimprint lithography is a cost-effective, high-throughput alternative for metasurface fabrication; nevertheless, the low refractive index of conventional imprint resins fundamentally limits device performance. Here, we describe the fabrication of optical metasurfaces using a printable high-index composite material known as nanoparticle-embedded resin (nanoPER). By embedding high-index nanoparticles into a curable resin matrix, nanoPER achieves an effective refractive index above 1.8 at the target wavelength and enables single-step replication of functional nanostructures on a wide range of substrates, including flexible and curved surfaces. The procedure focuses on TiO