Patent ID: 7791813

Claim:
A microfluidic device comprising: a reservoir containing first and second fluids of different electric or magnetic properties, wherein the first and second fluids are immiscible such that an interface surface is formed between the first and second fluids; and a drive unit including at least two steering electrodes and operable to selectively displace the interface surface into at least two different positions via an electric or magnetic force, wherein: a voltage selectively applied to each steering electrode generates an electric force between that steering electrode and the first fluid, the selective application of the voltage to the at least two steering electrodes determines a tilt angle of the interface surface with respect to a tilt axis, each of the at least two different positions correspond to different tilt angles of the interface surface with respect to the tilt axis, and the first and second fluids have different optical properties, such that while in a first position, the interface surface is configured so that light transmitted by a source is directed to a display surface, and while in a second position, the interface surface is configured to redirect the transmitted light away from the display surface.