A pH-driven DNA sway rod is prepared by immobilizing thiolated DNA, mercaptohexanol, and cysteine on a gold electrode surface. As pH changes around the pI of cysteine, contrary electrostatic effect is produced between the negative DNA and amphoteric cysteine, which actuates reversible conformational transitions, such as sway of the DNA molecules, rodlike chain-to-globule, and so forth. The nanoscale motion can be detected by commonly used electrochemical technique and reversible electrochemical signal may be observed.