Supporting Information for

Microfabrication-free Fused Silica NanofluidicInterface for On Chip Electrokinetic Stacking ofDNA

Da-Wei Zhang,aHui-Qin Zhang,aLi Tian,a Lin Wang,aFang Fang,ab Kun Liuc and Zhi-Yong Wu*a

aResearch Center for Analytical Sciences, bChemistry department, cResearch Institute of Vacuum and Fluid, Northeastern University, Shenyang 110819, China

*Correspondence: Zhi-Yong Wu, Tel and Fax: +86 24 83687659,

  1. Filling of Nafion in the fracture

The filling of Nafion in the fracture may not necessarily complete as shown in Figure 1S.

Figure 1S.Partial filling of the fracture.(a) CCD image with negatively charged Fluorescence dye found in part of the fracture. (b) Schematic illustration of Nafion membrane formed in the fracture.

  1. Optimization of the Nafion concentration

Fig.2S shows the bright field CCD images and stacking performance of the interface formed by different concentrations of Nafion, and the general results are listed in Table 1S.

Fig. 2S. (a) The CCD images of the Nafion membrane formed in the fracture and on the fused silica capillary by 4 different concentrations as indicated. (b) beforeapplying voltage, (c) at 25 s with 250 V for Fluorescein 100μM.

Table 1 Summary of theperformance of Nafion membrane formed by different concentrations

Nafion concentration / Membrane thickness / Membrane uniformity / Preconcentration effect
0.5wt % / + / +++ / +
1.5wt % / ++ / ++ / ++
2.5wt % / +++ / ++ / ++
5.0wt % / ++++ / + / ++
  1. Stacking of Fluorescein

The movie clip shows the preconcentration of fluorescein solution. A solution of 100 μM fluorescein in 0.1×TBE buffer at pH 8.6 was filled in the main microchannel, vial A and vial C, while 0.1×TBE buffer was filled vial B. Applied voltages at the vials VA, VB, and VC were 0, 250, 0 V, respectively.

  1. Stacking of DNA

The movie clip shows the preconcentration of DNA, 0.6×SYBR Green I-tagged 3.2 μg/mL λ-DNA in 0.1×TBE buffer at pH 8.6 was filled the main microchannel, while 0.1×TBE buffer was filled vial B. Applied voltages at the vials VA, VB, and VC were 0, 200, 0 V, respectively.