Elaboration and characterization of nanoporous SU-8 template using PMMA as porogen

Abstract

We present here a simple and robust photolithography method to fabricate high-porosity SU-8 negative resist templates using positive Poly(methyl methacrylate) (PMMA) as the porogenic agent. We report on how these nanoporous structures are greatly affected by the volume fraction of each component in the precursor solution and by the amount of exposure, to be limited to grant sufficient access to PMMA chains during pore formation. Tuning the porosity of the SU-8 film, we could broadly tailor its effective refractive index (n) from n = 1.27 to 1.58, in the visible/near-infrared domain. By further using the interference lithography technique, we demonstrated various kinds of porous micro/nanostructured surfaces. A hydrophobic effect was demonstrated with a high water contact angle of 130°. Such porous SU-8 templates could enhance, at modest cost, the design room of polymer-based photonic architectures in many areas, such as sensing, microfluidic and optoelectronic device.