A flow chamber was prepared by placing a custom-fabricated acrylic support on an acid-cleaned cover slip with a height of 100 μm formed by double-sided tape (16 ,17 (link)). The dimensions of the flow cell were approximately 5 × 10 × 0.1 mm (L × W × H). An NE-1000 syringe pump (New Era Pump Systems Inc., Wantagh, NY, USA) was used to control the buffer in the flow cell. After preparation, 40 μg/ml biotinylated bovine serum albumin were injected and incubated at room temperature for 10 min, followed by 20 μg/ml of Neutravidin in T50 solution (10 mM Tris, 50 mM NaCl, pH 8.0) with the same condition. Then, 1 μM of λ DNA overhang oligo (5′-p-GGGCGGCGACCT-Triethyleneglycol-biotin-3′) was loaded into the flow chamber and maintained at room temperature for 10 min. λ DNA, 200 U of T4 DNA ligase, and reaction buffer was added and incubated at room temperature for 30 min. After washing the residual enzyme mixture with 1 × TE (10 mM Tris, 1 mM EDTA, pH 8.0), the diluted TAMRA-polypyrrole solution flowed into the channels, resulting in visualization of the tethered DNA. Stained DNA molecules were visualized under a continuous flow of 1 × TE with the flow rate maintained at 100 μl/min.