Microfabrication-free fused silica nanofluidic interface for on chip electrokinetic stacking of DNA

In this article, a simple but robust nanofluidic interface was introduced directly on a chip comprised of commercially available fused silica capillary with ready-made microchannel, and efficient on chip electrokinetic stacking of DNA was successfully demonstrated based on ion concentration polarization (ICP) effect. The nanofluidic interface was established by casting ion exchange polymer resin (Nafion) into a sub-microfracture (similar to 650 nm) prepared on the capillary manually. The width of the fracture was electrically measured with the aide of a mathematic fracture model and confirmed by scanning electronic microscope. Obvious ICP effect was observed both by online microscopic fluorescent imaging and post laser induced fluorescence detection. SYBR Green I labeled dsDNA was stacked at the nanofluidic interface inside the microchannel (cathode side) with a concentration factor of 10(3) within 15 s. As high as 800 V was applied through the interface without any damage. The main materials are all commercially available, and no advanced microfabrication facilities are involved in the preparation of the chip.