2-D Analysis of Enhancement of Analytes Adsorption Due to Flow Stirring   by Electrothermal Force in The Microcantilever Sensor
  Ac electrokinetic flows are commonly used for manipulating micron-scale particles in a biosensor system. At the solid-liquid state there are two kinds of processes in the reaction between analytes and ligands: the mass transport process and the chemical reaction process. The mass transport process is related to convection and diffusion. Total or partial limit of mass transport would retard the diffusion from the bulk fluid to the interface of reaction. This effect decreases the possibility of adsorption of analyte and ligand because the chemical reaction is faster than the diffusion. In order to solve this problem, we apply an ac electric field to induce a vortex field by the electrothermal effect, which helps in increasing the rate of diffusion. By using the finite element analysis software, COMSOL Multiphysics, we optimized several parameters of the microelectrode structures and the position of the reacting surface, i.e. the microcantilever, by a simplified 2-D model and a 3-D model. It is successful in accelerating the reacting rate of the molecule which is limited by mass transport. The factor of the efficiency is about 1.429 when the operating voltage is 15 Vrms peak-to-peak. In addition, the surface concentration of the complex on the microcantilever has been simulated. 
M.C. Wu, J.S. Chang, C.-K. Yang