Single-molecule Measurement and Its Application by Electric Impedance Spectroscopy Using Nanochannel

Recent advances in nanofluidic technologies have enabled fabrication of nanochannels with at least one dimension smaller than several hundred nanometers. Since this dimension is close to the sizes of biomolecules, such as DNA, proteins, and various types of nano-particles, it opens up new technological fields based on the analysis and manipulation of single molecules. This paper introduces the current state of knowledge regarding single-molecular level analysis and processing in nanochannels, particularly experimental findings in this area based on our research knowledge. While there have been many theoretical and molecular simulation studies, this paper considers experimental studies. We review our fundamental studies of ionic and electric double layer structures in a nanochannel. We then discuss the emerging challenge of electrical single-molecule detection and its possible applications of single-molecule sorter and a virus sensor, which are highlighted. Separation and separation-based analysis of biomolecules are important techniques in biotechnology. The ultimate resolution and sensitivity should be realized by a single-molecule system, because of the deterministic nature of one-by-one single-molecule detection, which is impossible to conduct by conventional stochastic separation processes. The concept of a single-molecule sorter that identifies individual single-molecules and separates them individually has been demonstrated to realize the ultimate level of resolution and sensitivity for future separation-based technology.