Adhesive lift method for patterning arbitrary-shaped thin ion-selective films in micro/nanofluidic device

Micro/nanofluidic platforms with nanoporous films have been utilized as research tools for studying electrokinetic phenomena occurring not only in macro-scale systems such as electro-desalination but also in micro-scale systems such as bio-molecular preconcentrators. However, due to the limitations of fabrication techniques, studies with nanoporous films are mainly limited to vary the physicochemical properties of the films such as surface charge and pore size, despite the enormous effect of the membrane morphology on the phenomena that is to be expected. Therefore, we propose an economic and feasible nanofabrication method called the "adhesive lift method" for patterning thin arbitrarily-shaped nanoporous film to integrate it into micro/nanofluidic platforms. The conformal patterning of the nanoporous films (Nafion or poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (PEDOT:PSS) in this work) was accomplished with spin coating, oxygen plasma treatment and the "adhesive lift technique". Using the fabricated platforms, the initiation of ion concentration polarization along the film with various shapes was demonstrated. In particular, various electrokinetic characteristics of overlimiting conductance depending on the length scale of the microchannels were successfully demonstrated. Therefore, the presented adhesive lift method would provide platforms which can nearly mimic practical macro-scale fluidic systems so that the method would be very useful for studying various electrokinetic phenomena inside it.