title: Direction Dependence of Resistive-Pulse Amplitude in Conically Shaped Mesopores.
abstract: Conically shaped pores such as glass pipets as well as asymmetric pores in polymers became an important analytics tool used for the detection of molecules, viruses, and particles. Electrokinetic or pressure driven passage of single particles through a single pore causes a transient change of the transmembrane current, called a resistive-pulse, whose amplitude is the measure of the particle volume. The shape of the pulse reflects the pore topography, and in a conical pore, resistive pulses have a shape of a tick point. Passage of particles in both directions was reported to produce pulses of the same amplitude and shapes that are mirror images of each other. In this manuscript we identify conditions at which the amplitude of resistive-pulses in a conical mesopore is direction dependent. Neutral particles entering the pore from the larger entrance of a conical pore, called the base, block the current to a larger extent than the particles traveling in the opposite direction. Negatively charged particles on the other hand size larger when being transported in the direction from tip to base. The findings are explained via voltage-regulated ionic concentrations in the pore such that for one voltage polarity a weak depletion zone is formed, which increases the current blockage caused by a particle. For the opposite polarity, an enhancement of ionic concentrations was predicted. The findings reported here are of crucial importance for the resistive-pulse technique, which relates the current blockage with the size of the passing object.
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697, United States.|School of Mechanical Engineering and Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University , Nanjing 211189, China.
authors.forename: Yinghua
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: Oak Ridge National Laboratory , 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, United States.
authors.forename: Ivan
authors.initials: I
authors.lastname: Vlassiouk
authors.affiliation: School of Mechanical Engineering and Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, Southeast University , Nanjing 211189, China.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Physics and Astronomy, University of California , Irvine, California 92697, United States.|Department of Chemistry, University of California , Irvine, California 92697, United States.|Department of Biomedical Engineering, University of California , Irvine, California 92697, United States.
authors.forename: Zuzanna S
authors.initials: ZS
authors.lastname: Siwy