Injection molding process for fabricating metalens with high aspect ratio nanostructures

Abstract

Injection molding process is one of the most productive techniques having potential to fabricate nanostructures rapidly and efficiently in large numbers. We have developed a high aspect ratio nanostructure replication process for metalens with multi height nanopillars by injection molding. The process that we have developed consists of three main steps: master mold replication, Ni stamper fabrication and injection molding. The master mold was surface-treated with a lowmolecular-weight fluorine material to produce replica of high aspect ratio nanopillars by imprinting. The composite process of conformal deposition to form base electrode layer and nickel electroplating realized the fabrication of a stout, void-free Ni stamper from the master mold replica. In injection molding for nanopillars with a high aspect ratio, the Ni stamper surface was treated by the surfactant to improve releasability and the thermoplastics temperature at the injection was controlled to adjust its flow rate. The influences of the Ni stamper surface treatment and the thermoplastics temperature on the final replication quality were investigated. It was found that the Ni stamper surface treatment improved the releasability and suppressed the elongation and inclination of the formed nanopillars. Also, the wellcontrolled thermoplastics temperature realized the high aspect ratio nanopillar replication. Finally, we have obtained a plastic metalens by injection molding, which replicates the mold properly. It shows that injection molding process has great potential for metasurface mass-production.