1. A method of fabricating metal-fiber conductive structures on a porous substrate, the method comprising the steps of:(i) applying a coating compound comprising poly (4-vinylpyridine) (P4VP), Polyvinylpyrrolidone (PVP) and SU-8 dissolved in an organic alcohol solution to one or more surface of the porous substrate;
(ii) curing the porous substrate at a temperature of at least 130° C. such that the porous substrate is coated with a layer of said coating compound;
(iii) printing a jet of a transition metal salt catalyst solution onto one or more printing sides of the porous substrate to deposit a transition metal salt catalyst onto the one or more printing sides;
(iv) submerging the substrate in an electroless metal deposition solution to deposit the metal on the porous substrate, wherein the deposited metal induces the formation of one or more three-dimensional metal-fiber conductive structures within the porous substrate.