광전자유체역학을 이용한 입자의 연속적 분리와 봉입 및 광열 유동을 통한 액적 조작

Abstract

Manipulation methods of particles or droplets using light have drawn much attention among microfluidic techniques. It is because they can obtain very flexible manipulation strategies, requiring only simple fabrication processes. In this thesis, particle manipulation by optoelectrofluidic platform and droplet manipulation by optothermal flow are investigated. In part I, continuous separation and simultaneous encapsulation of particles based on a microchannel integrated optoelectrofluidic platform are investigated. We could obtain significantly increased separation efficiency than the previous continuous separation with optoelectrofluidics. It was possible due to flow fractionation at particle inlet and careful control of the force balance of particles near the light-driven virtual electrodes. After the separation, we encapsulated target samples into nano-liter size water droplets by injecting oil phase into the microchannel network. Our achievement successfully fulfilled both continuous separation and simultaneous encapsulation, which were not performed yet with the optoelectrofluidics. Therefore, we expect our platform would be used for multifunctional sample preparation processes in biological or chemical application. In part II, we demonstrate transporting, merging, and mixing of droplets by optothermal flows occurring in the oil medium. The optothermal flow is generated because of the thermal gradient caused on the heat absorption substrate and the interface between the oil and air. Bio-samples, including blood samples, were successfully manipulated with this method without thermal damages because this method only needs a small thermal gradient. As the density of the oil used is lower than that of water, sample droplets contact with the bottom substrate. The contact of the droplets and the substrate makes the system more applicable as the previously developed optoelectrofluidic techniques can be applied in the present system simultaneously. Then the system can be utilized to manipulate particles as well as droplets as a microfluidic platform.