DNA manipulation and retrieval from an aqueous solution with micromachined nanotweezers.

We have demonstrated DNA handling with micromachined nanotweezers that consist of a pair of opposing nanoprobes and integrated thermal expansion microactuators for changing the probe gap. The probe tips coated with a thin Al layer were dipped into a droplet of a solution containing lambda-DNA molecules labeled with fluorescence dye, and then an ac electric field was applied between probes for several seconds. DNA molecules were then captured between the probe tips and retrieved from the solution to the air. The DNA capture between the probe tips could be performed more successfully on the droplet surface than in the underwater region. We also conducted an observation of the retrieved DNA molecules by transmission electron microscope and found that the thickness of the retrieved DNA molecules under the condition of this experiment was approximately 21 nm when the time of the applied ac power (1 MHz, 20 Vpp) was 20 s.