Development of Single-Molecule Electrophoretic Control Method For Single-Molecule Tunnel-Current based Nucleotide Identification by Nano-fluid integrated Nano-gap Devices

Single-molecule tunnel-current detection is promising for identification of biopolymers. Until now, by using nano-gap-electrode devices, we measured tunneling-current time-traces during its translocation of nucleotide molecules through a nano-gap-electrode and, based on the conductance-intensity, the base-sequence are assigned. From the assigned sequence, most of the signals are found to be the partial sequences, which would be due to partial translocation of sample, which may be influenced by random-flow such as Brownian motion. In order to obtain longer right-read signals, the control of translocation behavior is necessary for biopolymer sequencing. In this study, we developed the nano-fluid integrated nano-gap device, in which also a pair of silver/silver chloride electrode is located. When dc voltage is applied through the fluid, negatively charged nucleotide translocate through the gap electrodes by electrophoresis. It is found that the fluid around nano-gap can strongly confine the nucleotide translocation route and molecular orientation so that integrated nano-fluidics straightly guide nucleotide molecules into the nano-gap electrode, resulting in frequent detections of longer-right read signals. This methodology would be useful for biopolymer electrical sensing.