Room temperature imprint using crack-free monolithic SiO₂-PVA nanocomposite for fabricating microhole array on silica glass

This paper aims to fabricate microhole arrays onto a silica glass via a room temperature imprint and subsequent sintering by using a monolithic SiO₂-poly(vinyl alcohol) (PVA) nanocomposite as the silica glass precursor. The SiO₂-PVA suspension was prepared from fumed silica particles and PVA, followed by drying to obtain tailored SiO₂-PVA nanocomposites. The dependence of particle size of the fumed silica particles on pore size of the nanocomposite was examined. Nanocomposites prepared from 7 nm silica particles possessed suitable mesopores, whereas the corresponding nanocomposites prepared from 30 nm silica particles hardly possessed mesopores. The pore size of the nanocomposites increased as a function of decreasing pH of the SiO₂-PVA suspension. As a consequence, the crack-free monolithic SiO₂-PVA nanocomposite was obtained using 7 nm silica particles via the suspension at pH 3. Micropatterns were imprinted on the monolithic SiO₂-PVA nanocomposite at room temperature. The imprinted nanocomposite was sintered to a transparent silica glass at 1200°C in air. The fabricated sintered glass possessed the microhole array on their surface with aspect ratios identical to the mold.