Low-cost, durable master molds for thermal-NIL, UV-NIL, and injection molding.

Abstract

Mold cost and mold lifetime are essential concerns for mass production of micro/nano-patterned surfaces by nanoimprint lithography or micro/nanoinjection molding. Master molds are typically produced by subtractive processing using wafer-based clean room techniques. For imprint lithography, polymer copies of such molds can often be employed, but the durability of such molds is quite limited. The conditions of high temperature and pressure for injection molding require use of the durable masters created in stainless steel, nickel or other robust materials, but such approaches are challenged by high cost of patterning these substrates and limited lifetime. Here we report the fabrication of durable crystalline zirconium dioxide (ZrO2) masters via a simple direct imprint technique. ZrO2 nanoparticles (NPs) were formulated into an ink and imprinted on a variety of substrates using a solvent-assisted patterning technique and subsequently annealed to increase the mechanical durability of the mold. The hardness and modulus values of the ZrO2 coatings reached 11 ± 2 GPa and 120 ± 10 GPa, respectively after annealing. The hard ZrO2 mold was then employed for precision patterning of polymer surfaces by thermal and UV nanoimprinting lithography (NIL) techniques, and by injection molding. High fidelity pattern transfer continued throughout 115,000 injection molding cycles, there was no evidence of delamination, breakage or wear in the ZrO2 mold. Our simple imprint patterning technique using ZrO2 NPs inks enable us to fabricate robust molds with excellent thermal and mechanical properties as easily as imprinting simple polymer replicas. This simple and low-cost approach to mold preparation can enable a large variety of high throughput or large area nano-replication technologies.