Direct imprinting of TiO2 patterns on highly curved substrates

In this paper, we demonstrate the fabrication of TiO2 patterns on both planar and various highly curved substrates via nanoimprint lithography followed by thermal treatment. First, a photocurable Ti-containing monomer is synthesized by reacting titanium (IV) ethoxide with 2-(methacryloyloxy)ethyl acetoacetate. The monomer is formulated with a visible light photoinitiator system to prepare a photocurable nanoimprint resin (TiO2-resin). Afterward, the resin is able to be patterned onto highly curved substrates using a soft mold via the double transfer technique. Resin patterns can be simply transformed to TiO2 patterns after thermal treatment. Refractive index of TiO2 can also be tuned by changing the calcination condition.