NOVELTY - Fabricating fuel cell component involves providing mask (102) having radiation transparent apertures (104), where apertures permits radiation beams (106) to be directed through them; providing radiation-sensitive material (108) having sensitivity to the beams; providing flow field layer; disposing material on flow field layer; and exposing material to radiation beams through apertures in the mask to form diffusion medium layer (114) with a micro-truss structure. The method further involves applying sacrificial release layer (148) to mask.    USE - For fabricating a fuel cell component (claimed); in fuel cell used as power source for electric vehicles and various other applications; and in modern automobiles.    ADVANTAGE - The method forms fuel cell that provides clean, efficient and environmentally responsible power source for electric vehicles and various other applications. The method optimizes fuel cell durability, minimizes tooling costs, minimizes production costs, and minimizes development time. The method militates against the non-uniformity and design constraints associated with the formation of components according to the known methods. The fabrication method permits low temperature processing to minimize thermal strains developed from a coefficient of thermal expansion (CTE) mismatch between different radiation-cured layers. A bonding mechanism allows for one of the radiation-cured layers to be formed in-situ onto an other of the radiation-cured layers, rather than forming the two radiation-cured layers independently before they are bonded together. The in-situ process eliminates the need for critical alignment between the different radiation-cured layers. A multi-functional and reusable handle wafer can also serve as a photomask used to pattern one of the radiation-cured layers. With respect to multi-tiered composite structures, an interlocking mechanism between the different radiation-cured layers absorbs thermal strain and provides a strong bond between the radiation-cured layers. The dimensions (member radius, spacing, thickness, density) of the radiation-cured layers can also be adjusted to optimal fuel cell performance.    DETAILED DESCRIPTION - Fabricating a fuel cell component involves providing a mask (102) having radiation transparent apertures (104), where the apertures permits radiation beams (106) to be directed through them; providing a radiation-sensitive material (108) having a sensitivity to the radiation beams; providing a flow field layer; disposing the radiation-sensitive material on the flow field layer; and exposing the radiation-sensitive material to the radiation beams through the radiation transparent apertures in the mask to form a diffusion medium layer (114) with a micro-truss structure. The method further involves applying a sacrificial release layer (148) to the mask, where the sacrificial release layer is transparent to the radiation beams; and applying the radiation-sensitive material to the sacrificial release layer. The method further involves removing the mask and the sacrificial release layer from the diffusion medium layer after the radiation-sensitive material is exposed to the radiation beams. The sacrificial release layer is removed by immersing the release layer and the mask in a solvent that dissolves the release layer and permits removal of the mask. The mask is a radiation transparent material coated with a radiation opaque material, where the radiation opaque material has holes defining the radiation transparent apertures of the mask. The radiation transparent material is glass and the radiation opaque material is a patterned chromium coating. The radiation-sensitive material is heated to minimize residual stress prior to being disposed on the flow field layer. The diffusion medium layer is bonded to the flow field layer during the formation of the diffusion medium layer. The flow field layer is formed on a substrate. When the substrate is a metal foil, the flow field layer includes radiation-cured reactant flow channels. The radiation-cured reactant flow channels include an adhesion promoter that enhances a bonding of the radiation-cured reactant flow channels to the metal foil. The method further involves coating at least one of the diffusion medium layer and the flow field layer with an electrically conductive coating.    DESCRIPTION OF DRAWING(S) - The figure shows modification to truss spacing dependent upon a location of a mask relative to a layer of radiation-sensitive material.    Mask (102)    Radiation transparent apertures (104)    Radiation beams (106)    Radiation-sensitive material (108)    Diffusion medium layer (114)    Sacrificial release layer (148)