Development of Nanofluidic Sample Preconcentration and Separation Platform Using Ion Concentration Polarization

Abstract

Ion concentration polarization (ICP) is an electrochemical phenomenon that takes place in membrane system or electrolyte-electrode interface. With advances on micro/nano fabrication method, ICP has been applied to various engineering fields since the year of 2000. Of many application fields, one of major application using ICP is on-chip sample preconcentration. This electrokinetic sample concentrator allows extremely high concentration factors as well as simple device configuration compared to previous developed method such as isotachophoresis and field amplification stacking. In addition, the concentration factor is independent of the size and hydrophobicity of target species, and it is not required special buffer and reagents. While this concentrator has many advantages in terms of biomolecules concentration, there are still many challenging problems to be resolved for incorporating as a part of integrated microTAS (Total Analysis Systems), which include low volume of concentrated sample, non-multiplexed detection and limitation of device structure, etc. In this dissertation, for high volume of concentrated sample and downstream integrations, I developed massively parallel concentration device enabling multiplexed detection. Various types of immunoassay including enzyme linked immunosorbent assay (ELISA) are performed for confirming the device performance. In addition, the integration of concentrator with additional microfluidic components was hampered by the conventional concentrator structure. Thus, in order to simplify the device structure, I demonstrated that the concentrator composed of only a straight microchannel, which can perform most of functions of the concentrator developed previously. In addition to sample accumulation, since ICP mechanism is able to block charged species, such as ions and proteins, the separation system for ions and cells was demonstrated by using ICP phenomenon. Given importance of integrated micro-TAS, it is expected that the proposed nanofluidic platforms in this dissertation would be useful in terms of development of sample preparation methods.