title: Nonequilibrium Ionic Response of Biased Mechanically Controllable Break Junction (MCBJ) Electrodes.
abstract: Novel experimental techniques allow for the manipulation and interrogation of biomolecules between metallic probes immersed in micro/nanofluidic channels. The behavior of ions in response to applied fields is a major issue in the use of these techniques in sensing applications. Here, we experimentally and theoretically elucidate the behavior of background currents in these systems. These large currents have a slowly decaying transient response, as well as noise that increases with ionic concentration. Using mechanically controllable break junctions (MCBJ), we study the ionic response in nanogaps with widths ranging from a few nanometers to millimeters. Moreover, we obtain an expression for the ionic current by solving time-dependent Nernst-Planck and Poisson equations. This expression shows that after turning on an applied voltage, ions rapidly respond to the strong fields near the electrode surface, screening the field in the process. Ions subsequently translocate in the weak electric field and slowly relax within the diffusion layer. Our theoretical results help to explain the short- and long-time behavior of the ionic response found in experiments, as well as the various length scales involved.
authors.affiliation: Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University , Toyonaka, Osaka 560-8531, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Doi
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University , Ibaraki, Osaka 567-0047, Japan.
authors.forename: Makusu
authors.initials: M
authors.lastname: Tsutsui
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University , Ibaraki, Osaka 567-0047, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Ohshiro
authors.affiliation: Theoretical Division, Los Alamos National Laboratory , Mail Stop B213, Los Alamos, New Mexico 87545, United States.
authors.forename: Chih-Chun
authors.initials: CC
authors.lastname: Chien
authors.affiliation: Department of Physics, Oregon State University , Corvallis, Oregon 97331, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Zwolak
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University , Ibaraki, Osaka 567-0047, Japan.
authors.forename: Masateru
authors.initials: M
authors.lastname: Taniguchi
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University , Ibaraki, Osaka 567-0047, Japan.
authors.forename: Tomoji
authors.initials: T
authors.lastname: Kawai
authors.affiliation: Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University , Toyonaka, Osaka 560-8531, Japan.
authors.forename: Satoyuki
authors.initials: S
authors.lastname: Kawano
authors.affiliation: Department of Physics, University of California , San Diego, La Jolla, California 92093, United States.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Di Ventra