Design and optimization tapered fiber with Negative Dielectrophoretic Effect for oil-in-water concentration sensor

This work presented the design and simulations of an integrated micro-electrodes into the tapered fiber aimed to improve the sensitivity of oil-in-water concentration with potential applications in predictive the low aqueous concentration. The designed sensor consisted of two part: a tapered fiber and a pair of micro-electrodes, which generated a non-uniform electric field so that the emulsified oil particles around the tapered fiber could be repelled by dielectrophoresis forces. Consequently, the evanescent wave field of the tapered fiber would change due to fluctuation of the refractive index. In addition, different parameters for the tapered fiber, such as tapered ratio (TR) and tapered length (TL), were investigated to optimize the sensing accuracy. To optimize these relevant parameters, we performed numerical simulations using COMSOL software based on the finite element method. The results indicated that the oil concentration measurement sensitivity of the proposed sensor was increased to be 26.2% higher than that of an identical tapered fiber sensor without DEP forces.