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A new microfluidic MEMS-based light modulator using magnetic fluid is introduced. The device has a planar structure that makes it suitable for being produced with conventional thin-film processes and for being used in flat-panel displays (FPDs). The optical reflectance from the device is modulated by applying an electric current into an electrode. The magnetic field produced by the current exerts a magnetic force on the magnetic fluid and drives it to cover the cell surface. The surface tension of the fluid provides a restoring force when the field is reduced. A permalloy based thin-film process developed for the manufacturing of inductive head for magnetic data storage devices was used for the device fabrication. The actuation of the fluid is completed in about 12 ms for both thin-to-thick and thick-to-thin fluid film switching by magnetic forces and surface tension forces, respectively. It was observed that the switching speed was almost independent of the driving current, and no considerable thermal effect has been observed when driven by a current up to 100 mA.