Fabrication and Ionic Tansport through On-Chip Nanofluidic Channels

Abstract

In order to study the ionic transport through individual nanoscale channels, a reliable method of creating an on-chip nanofluidic channels should be found. Here, we present a simple method of utilizing conventional lithography techniques to fabricate fluidic channels with less than 100 nm channel height on SiO2 substrates. The nanoscale fluidic channels are defined by using double-layer over exposed poly-methylmethacrylate (PMMA) electron-beam resist as templates. Spin-coating a dilute low molecular weight PMMA (495k) on a high molecular weight PMMA (950k) creates a channel template that has a circular cross section. The tapered edges of the resist after exposure increases the step-coverage of subsequently sputtered SiO2 reducing lift-off probability. The widths of the channel was 3 m at the narrowest and 30 m at the widest. Support pillars were incorporated into channels with widths wider than 10 m to prevent channel collapse and removal during lift-off. Optical microscope observation confirmed fluidic transport through the nanochannels demonstrating complete removal of the PMMA template. Also, ionic transport through the Nanofluidic channel has been observed using Pt electrodes and showed dependence on ionic concentration.