US Patent 7538934 Surface force driven suspended particle devices

An optical device employs a fluid host medium (30) including a polar liquid (31) and an apolar liquid (32). The optical device further employs one or more electro-optically sensitive flakes (40-42) disposed within fluid host medium (30). To facilitate a switching of the optical device among a plurality of optical states (e.g., varying degrees of light reflecting states, light absorbing states, light fluorescing states and/or light transmitting states), each flake (40-42) has one or more hydrophilic layers (44) interfacing with the polar liquid (31) and/or one or more hydrophobic layers (45) interfacing with the apolar liquid (32).