The purpose of this research is to develop a fabrication technique of microstructures on nonplanar substrates, investigating so called, optical softlithography. In addition, PDMS roller stamps were duplicated from these structures on curved substrates as the mold, roll micro contact printing was performed successfully.
Micro structuring on nonplanar substrates has not been fully established yet, although several fabrication methods, such as laser direct writing and modified photolithography, were proposed. Moreover, those techniques require still expensive and complex processes. To overcome those drawbacks, optical softlithography using flexible photomasks was developed . Firstly, SU-8 micro structures were fabricated on concave substrates by optical softlithography using PDMS flexible photomasks. As a result, SU-8 structures with 2.5 μm line width and high aspect ratio over 7.9 were fabricated on a concave substrate. Also, experimental parameters for optical softlithography were investigated and established for further fabrications and applications. In addition, the tilting structures were confirmed due to the vertical UV exposure method.
Next, Based on these novel 3D patterning technologies, PDMS roller stamps were fabricated and roll micro contact printing was performed. The roll micro contact printing was investigated by using the customized roll micro contact printing apparatus and the flexible pressure sensor system. We expect this technique can provide various sized roller stamps with various micro patterns for μCP process as well as roll micro contact printing process.