Monolithic bridge structures were fabricated by using capillary-force lithography (CFL), which was developed for patterning polymers over a large area by combining essential features of nanoimprint lithography and capillarity. A patterned soft mold was placed on a spin-coated UV-curable resin on a substrate. The polymer then moved into the cavity of the mold by capillary action and then solidified after exposure to UV radiation. The uncured resin was forced to migrate into the cavity of a micropatterned PDMS mold by capillarity, and then exposed to UV radiation under a high-energy mercury lamp with intensity. A rotary pump was then turned on, decreasing the air pressure in the chamber. SEM images were taken with a high-resolution SEM at an acceleration voltage greater than 15 kV. It was observed that when the air pressure was rapidly reduced to a low vacuum, the top layer moved into the nanochannels with a meniscus at the interface between the nanoscale PUA and the base structure.
This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korean government (MOST) (R01-2007-000-20675-0), the King Abdullah University of Science and Technology (KAUST) program (No. KUK-F1-037-02), and the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (Grant KRF-J03000). This work was supported in part by the Center for Nanoscale Mechatronics & Manufacturing (Grant 08K1401-00210) and the Grant-in-Aid for Strategy Technology Development Programs from the Korean Ministry of Knowledge Economy (No.10030046).