NOVELTY - The separator plate comprises a substrate (200) having a polymeric first flow field layer (202), and a polymeric second flow field layer (204). The substrate is disposed between the first and second flow field layers, is electrically nonconductive substrate, and has electrically conductive vias. The first flow field layer and/or second flow field layer: has polymeric reactant flow channels and an electrically conductive coating; and includes support ligaments and a microtruss structure providing the support ligaments. The reactant flow channels include first channel walls (210).    USE - The separator plate is useful for a fuel cell such as a polymer electrolyte membrane fuel cell and a micro-fuel cell, which is useful as a power source for electric vehicles, portable devices and traditional internal-combustion engine in modern automobiles.    ADVANTAGE - The cost effective separator plate can be manufactured with excellent stiffness and strength, improves durability and efficiency of the clean and compact fuel cell, and minimizes the tooling and production costs and development time of the fuel cell.    DETAILED DESCRIPTION - The separator plate comprises a substrate (200) having a polymeric first flow field layer (202), and a polymeric second flow field layer (204). The substrate is disposed between the first and second flow field layers, is electrically nonconductive substrate, and has electrically conductive vias. The first flow field layer and/or second flow field layer: has polymeric reactant flow channels and an electrically conductive coating; and includes support ligaments and a microtruss structure providing the support ligaments. The reactant flow channels include first channel walls (210) extending along a first direction, and second channel walls (212) extending along a second direction. The first and second channel walls interpenetrate each other at junctions, and co-operate with the substrate to form coolant channels. The support ligaments are disposed between one of the first and second channel walls and the substrate, and militate against a flexing of the first channel wall and/or second channel wall. The second flow field layer includes first channel walls and second channel walls that form reactant flow channels. A portion of the first channel walls and the second channel walls of the second flow field layer cooperates with the substrate to form coolant flow channels that are not present in communication with the reactant flow channels of the second flow field layer. The first flow field layer includes channel walls extending along a length of the first flow field layer that defines first reactant flow channels. An INDEPENDENT CLAIM is included for a fuel cell.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic fragmentary side cross-sectional elevation view of a separator plate.    Substrate (200)    First flow field layer (202)    Second flow field layer (204)    First channel walls (210)    Second channel walls. (212)