Real-Time Modulation of DNA Conductivity via Magnetic Fields Studied by C-AFM

The charge transport properties of DNA make it a promising candidate for molecular electronics, yet the in situ dynamic regulation of its conductivity remains challenging. In this study, a conductive atomic force microscopy (C-AFM) system integrated with magnetic field modulation was developed to investigate the real-time conductivity of λ-DNA on Au-coated mica substrates. The results demonstrate that DNA molecular height positively correlates with tunneling current, with single double-stranded DNA (dsDNA) exhibiting a median current of -1.27 pA in the height range of 300 ~ 600 pm, while multi-stranded intertwined DNA fibers showed significantly enhanced conductivity (median current: -3.71 pA). Under a direct current (DC) magnetic field of 15 mT, both DNA forms exhibited suppressed conductivity, attributed to the Lorentz force effect. In contrast, an alternating current (AC) magnetic field (25 MHz) at 3 mT enhanced conductivity, whereas a 6 mT field led to a reduction. These findings provide direct experimental evidence for the real-time magnetic modulation of the transverse tunneling conductance through DNA molecules and offer a noncontact strategy for tuning DNA-based nanoelectronic devices.