Patent ID: 8111465

Claim:
An electrofluidic device comprising: an electrically-conductive, polar fluid; a non-polar fluid that is immiscible with the polar fluid; a fluid vessel including a first region and a second region in fluid communication with the first region, the first and second regions containing the polar and non-polar fluids with the non-polar fluid occupying space within the fluid vessel that is not occupied by the polar fluid, the second region including a viewable area through which at least one of the polar and non-polar fluids is visible external to the fluid vessel, and the first region of the fluid vessel having a smaller surface area-to-volume ratio than the second region of the fluid vessel; a voltage source operable to selectively apply an electromechanical force to the polar fluid, the electromechanical force effective to transfer at least a portion of the polar fluid from the first region of the fluid vessel to the second region of the fluid vessel; a capacitor disposed on at least a portion of the second region of the fluid vessel and electrically coupled with the voltage source, the capacitor having a hydrophobic surface contacted by the polar fluid, the hydrophobic surface configured to provide a first principal radius of curvature of the polar fluid that is convex and that is smaller than a second principal radius of curvature of the polar fluid in the first region of the fluid vessel, such that a portion of the polar fluid will move from the second region of the fluid vessel into the first region of the fluid vessel when the electromechanical force is removed; and a duct in fluid communication with the first and second regions of the fluid vessel such that the non-polar fluid displaced from the second region moves through the duct from the second region of the fluid vessel to the first region of the fluid vessel; wherein the polar and non-polar fluids differ in at least one optical property such that, as the portion of the polar fluid is moved by the electromechanical force from the first region of the fluid vessel to the second region of the fluid vessel, a spectral property of light transferred through the viewable area changes, and the polar fluid moves to the first region of the fluid vessel when the electromechanical force is removed.