| AC Electrokinetics is a very important phenomenon in the presence of non-uniform electric fields that is suited for direct manipulation of both particles and bulk fluid in the microfluidic system. Based on the parameters of the applied AC electric field such as voltage and frequency, as well as the properties of solution and the particles, for example, conductivity and permittivity, dominant forces in the microfluidic system may vary.;In this thesis, three examples of utilizing AC Electrokinetics in the microfluidic system for biomedical applications will be discussed. The first application was to use dielectrophoresis as a concentrator to form DNA attached carbon nanoparticles alignment between microelectrodes. The properties of this type of nanomaterial were investigated for further sensing applications. Then, the second example focused on cell manipulation in the microchannel, as self-rotation phenomenon of the pigment cells under positive dielectrophoretic force was observed, while there was no movement for non-pigment cells applied with the same dielectrophoresis parameters. The conditions and possible reasons for this phenomenon were investigated, the cell rotation speed was quantified and compared, based on which, manually induced rotation using non-pigment cells was proved successful. Last but not least, AC Electrothermal effect was utilized to facilitate the hybridization process of electrochemical biosensor arrays to overcome the disadvantages of enclosed sensor system and to further realize rapid pathogen identification. Optimized biosensor arrays showed promising performance including good specificity for a panel of target species, enhanced signal-to-noise ratio and improved limit-of-detection. Furthermore, preliminary clinical sample validation was conducted to confirm the feasibility of using this type of AC Electrokinetically facilitated biosensor arrays for future integration into a point-of-care device for molecular diagnostics. |
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