Preparation of PDMS membranes to permeate out Au-nanoparticles and permeation-blocking layers on the PDMS surface by photolithography

In this study, we demonstrate that a toluene solution containing Au nanoparticles could seep site-selectively out of a cross-linked poly(dimethylsiloxane) (PDMS) membrane whose surface was modified with a perfluoroalkylsilane adsorption film in accordance with a photomask shape. We first confirmed that Au nanoparticles passed through the cross-linked PDMS membrane by UV-Visible spectroscopy. The permeability of Au nanoparticles could be controlled by a feed ratio of a cross-linking reagent to liquid PDMS. By exposure to vacuum ultraviolet (VUV) light at 172 nm, silanol groups were generated on the PDMS surface due to photooxidation and then modified with a perfluoroalkylsilane adsorption film. The adsorption film worked as a permeation-blocking layer, and consequently we could let the nanoparticle solution seep out of the unexposed surface of the PDMS membrane into a solid surface.