| This thesis contributes to the investigation of the electric field induced phenomena in microfluidics and nanofluidics. In large scales, the surface charges are not obvious. However, it is the most prominent factor when scale shrinks down to micrometer or nanometer. The electric field induced phenomena consists of electric detection, electrokinetics (electrophoresis and electroosmosis) and dielectrophoresis. All of them are useful in detection, manipulation of fluid and manipulation of particles in micro/nano systems. In this thesis, the physical principles and governing equations of electric field induced phenomena are introduced and their applications are presented as well.;Based on the impedance analysis of the liquid system, a novel device called hybrid divider is built up. Hybrid divider consists of electric detection, signal analysis and fluid control is a building block for achieving multifunctional logic operations in microfluidic device. All 16 Boolean operations are constructed by three hybrid dividers. Electrokinetics originates from surface charge is dominant in confined space when electric field is applied. It could be applied to move particles and water solution in purpose. The advantages of electrokinetic phenomena are easy to implement, free of mechanical parts and good controllability. We demonstrated the precise liquid delivery for chemical reaction by a picoinjector whose precision could reach down to picoliter per second. Dielectrophoresis (DEP) is the induced dipole effect in non-uniform electric field. It is widely used in manipulating particles, cells and macromolecules. Different designs such as bottom-top electrodes and arc-shaped electrodes for AC DEP, waved structures and nanoslits for DC DEP are demonstrated for particle manipulations including focusing, trapping an separation. Compared to existing devices, our designs have improvements in easy fabrication, low cost, high efficiency and reusability. |
