Fig. 1. Schematic diagram of experimental set-up.

Fig. 2. DNA molecules enter the microchannel from the trans port and migrate inside (E = 3.75 × 10³ V·m^–1): (a) CCD photographs; (b) DNA molecular position.

Fig. 3. The velocity of DNA molecules entering and leaving the port (E = 3.75 × 10³ V·m^–1): (a) Entering the trans port; (b) leaving the cis port; and (c) velocity versus electric intensity.

Fig. 4. Reversed motion of DNA molecules within micro channel under different electric intensity: (a) E = 8.125 × 10³ V·m^–1; (b) E = 9.375 × 10³ V·m^–1; (c) percentage of DNA molecules with reversal motion direction in different regions of the cis port under different electric intensity.

Fig. 5. The motion of DNA molecules near the trans port: (a) Reciprocating along the axis; (b) rotating.

Fig. 6. The track of DNA molecules reciprocating near the trans port (E = 9.375 × 10³ V·m^–1).

Fig. 7. Aggregates of DNA molecules on the wall of microchannel near the trans port; (a) E = 7.5 × 10³ V·m^–1; (b) E = 1 × 10⁴ V·m^–1.

Fig. 8. Schematic diagram of buffer velocity distribution in microfluidic channel and the infromation of DNA: (a) Force; (b) velocity.

Fig. 9. Measured and theoretical velocities of DNA molecules at different positions on the same cross section of near the microchannel port.

Fig. 10. Schematic diagram of DNA molecules moving near the port of microchannel: (a) reversing near the cis port, and the reversed DNA molecule is easy to be adsorbed onto the inner wall, 7.5 × 10³ V·m^–1 ≤ E ≤ 1 × 10⁴ V·m^–1; (b) reversing near the trans port, E > 1 × 10 ⁴ V·m^–1.