In Situ Curing of Sliding SU-8 Droplet over a Microcontact Printed Pattern for Tunable Fabrication of a Polydimethylsiloxane Nanoslit

Abstract

A tunable process for polydimethylsiloxane (PDMS) nanoslit fabrication is developed for nanofluidic applications. A microcontact printing (mu CP) of a laterally spreading self assembled hexadecanethiol (HDT) layer, combined with in situ curing of a sliding SU-8 droplet, enables precise and independent tuning of a nanoslit-mold width and height using a single mu CP master mold. The SU-8 nanoslit-mold is replicated using a hard-soft composite PDMS to prevent channel collapse at low (<0.2) aspect ratio (height over width). The fluidic characteristics as well as dimensions of nanoslits fabricated with various conditions are analyzed using a fluorescein sample and AFM images. Finally, concentration polarization-based sample preconcentration is successfully demonstrated at the nanoslit boundary where an electric double-layer is overlapped.