Fig. 6.

Carbon nanotube (CNT) devices allow for conductivity measurements in single molecules of DNA. In this platform, a CNT is connected into an electrical circuit (top). Then, high resolution electron beam lithography and oxygen ion plasma are used to cut a gap in the CNT that has a defined width and carboxylic acid end functionalization (center). A single, amine-modified DNA duplex of compatible length is then added and made to covalently bridge the gap by peptide coupling (bottom). Importantly, the DNA is functionalized with amines on both the 5′ and 3′ ends of just one of the strands in the duplex (shown here in blue) such that the noncovalent strand (green) may be easily exchanged for fully complementary or mismatched strands. DNA-mediated current can then be measured across this reconnected DNA–CNT device and compared to the current across the uncut CNT.