Improvement of scanning ion-conductance microscopy for bio-analytical application

• Main Author: Kim, Joonhui
• Other Authors: Cho Nam-Joon
• Format: Theses and Dissertations
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Materials::Biomaterials; DRNTU::Science::Physics::Weights and measures
• Online Access: http://hdl.handle.net/10356/73734
• Institution: Nanyang Technological University

Scanning ion-conductance microscopy (SICM) is an emerging microscope technique among the family of scanning probe microscopy (SPM). Since the invention of scanning tunneling microscopy (STM) in 1981, SPM has widened their capabilities and opened the understanding of small things. The most promising one of SPM family is atomic force microscopy (AFM). AFM has the virtue of operating in any environment, vacuum, air and even in liquid. AFM can profile almost all physical and chemical properties in small scale by functionalization of its probes. By virtue of versatile utility, AFM has been stabilized for many years since its invention in 1986 and becomes a standard tool for nanoscale research. Increasing demands of biological studies in sub-micrometer level, AFM reaches its limitation because of employing forces to the target materials. Also, even though AFM can be utilized in a liquid environment, a serious interaction between the probe and the medium hinders to find the optimal operating condition. SICM natively loosens the problem, and provides the solution for bio-analytical studies, currently. However, the history of SICM is quite young; there are still many unrevealed principles waiting. Even if the measuring ion-conductance began from the Faraday’s age, the ion-transport in a sub-micrometer channel has been actively studied by modern researchers. The pipette with an opening in sub-micrometer scale is a well-defined model system of the submicrometer channels. Hence, this dissertation explores the advantages of SPM techniques, and discusses the current limitations both of AFM and SICM, first. This thesis shows what aspect of AFM is superior to the high-resolution scanning electron microscope (SEM), then explains the needs of a special utility to study soft materials. Although this thesis mainly targets SICM, the most promising feature of AFM, i.e. gauging of mechanical properties is presented with the extended functionality of SICM. The second part dedicates to improving and understanding the microscopy. Assuming Nitz’s model based on Ohm’s law, the alternative circuit configuration is suggested to reduce the system impedance. Reduced impedance leads lower noise and increasing the response speed of the probe. Then, this dissertation is organized to provide a platform to analyze the ion-transport phenomena over the Ohm’s law based model as a future perspective. The Poisson-Nernst-Planck model is an extended model to elucidate the kinetics of charged particles in a continuous medium. The brief discussion of the Poisson-Nernst-Planck equation is included. The progress presented in this dissertation would contribute to unravel questions about small things.