Fabrication of 1D nanofluidic channels on glass substrate by wet etching and room-temperature bonding

In this paper, a simple and facile technique for fabricating one-dimensional (1D) glass nanofluidic chips was developed. Instead of using expensive nanolithography, the standard UV lithography and wet chemical etching technique was used to fabricate 1D nanochannels on a glass substrate. Smooth channel surfaces were obtained by adding HNO3 into conventional HF-NH4F etching solution. The calibrated etching rate of 3.6 nm min-1 was achieved using 1.5 x 10-2 mol L-1 HF-7.5 x 10-3 mol L-1 NH4F-7.5 x 10-3 mol L-1 HNO3 as etchant at 40 deg. C. Inter-day preparation gave a R.S.D. of 6.8% in channel depth. The substrate was bonded with a glass cover plate at room temperature. A minimum aspect ratio (depth to width) of 5.0 x 10-5 for the nanochannels was achieved. The channel depth before bonding was measured by an a-surface profilometer, and the depth uniformity of nanochannels after bonding was demonstrated by cross-section scanning electron microscopy (SEM) analysis. With this technique, we successfully fabricated a nanofluidic device integrating nanochannel with microchannels and demonstrated the ion enrichment-depletion phenomena