Rapid DNA-DNA hybridization between surface-bound probe DNA and magnetically labeled complementary target DNA was achieved using current carrying line structures and oscillating external magnetic fields. Magnetic particles of 250 nm in diameter were focused and manipulated over on-chip U-shaped current lines using dc currents of 40 mA and oscillating magnetic fields of 1.4kAmrms with frequencies ranging from 0.1 to 20 Hz. The focusing process was both time and frequency dependent and, consequently, hybridization degree varied with focusing efficiency. Extensive label binding was observed in 5–25 min at 0.1–20 Hz. This technique has strong potential in commercial DNA chip development.

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See supplemental video of the ac field focusing of magnetic nanoparticles.

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