An electrophoretic display device includes a multiplicity of individual reservoirs containing a display medium between conductive substrates, at least one of which is transparent, wherein the display medium includes one or more set of colored particles in a dielectric fluid and has an electrical conductivity of about 10−11 to about 10−15 S/m, and wherein the multiplicity of individual reservoirs are defined by a unitary grid whose walls segregate the reservoirs. The grid may be formed via photolithography or from a master stamp derived from a mold of the grid pattern.