Microfluidic devices such as quartz crystal microbalances (QCM) and micromixers are often applied in Biochemistry and Biomedicine to mix different samples and biomolecular detection. At a micro- or nano-scale level, fluid flow is constantly in the state of laminar flow where pure diffusion is its primary mechanism of transporting specimens. However, the transportation through such mechanism consumes considerable time before reaching a point where transportation gets efficient. Thus it poses a restriction on the application of microfluidic devices to both medical mixing and bio-detecting. In this thesis, AC-electrokinetics is adopted to be integrated into microfluidic systems to enhance the mixing efficiency and reduce the detection time. AC-electrokinetics (ACEK) is used to manipulate micro-scale particles and disturb the fluid field in microfluidic systems. On the basis of different conductivities, applied voltages, AC-signal frequencies, and scales etc. AC-electrokinetics can be classified into Dielectrophoresis (DEP), Electrothermal effect (ETE) and AC-electroosmosis (ACEO). In this paper, we conduct the numerical simulations of the experiments on an Electrothermal-QCM chip and an ACEK-micromixer by commercial software “COMSOL Multiphysics”. In the end, the simulated results are compared with the experimental ones done by other students in our research group.