Galvanic process for making printed conductive metal markings for chipless RFID applications

A method for printing a conductive metal wire pattern on a substrate, comprising:

• printing a homogenous first salt solution comprising a first solvent and a first metal ion, the first metal ion selected from the group consisting of copper, aluminum, magnesium, manganese, zinc, chromium, lead, cadmium, cobalt, nickel, gold, silver, platinum, tin, iron, and mixtures thereof;
• printing a homogeneous second salt solution comprising a second solvent and a second metal ion configured to reduce the homogeneous first salt solution, the second metal ion selected from the group consisting of iron (II), lead (II), chromium (II), mercury (II), platinum (IV), palladium (IV), nickel (III), and cobalt (III);
• and
• forming a metal wire pattern by the galvanic reaction on the substrate of the printed homogeneous first and the homogeneous second salt solutions to precipitate the first metal ion as solid metal nanoparticles having a size of about 5 nm to about 7 nm on the substrate;
• wherein:
• additional energy is not required to anneal the metal nanoparticles together and create the conductive metal wire pattern;
• the second metal ion has a lower reduction potential than the first metal ion;
• the first and/or second salt solutions are printed directly onto the substrate;
• the substrate is selected from the group consisting of paper, glass art paper, bond paper, paperboard, Kraft paper, cardboard, semi-synthetic paper, and plastic sheets;
• the printing of the first salt solution and the second salt solution is performed using a heated printer that deposits the first salt solution and the second salt solution onto the substrate in a flowable state;
• and
• after mixing and reacting, the first solvent of the first salt solution and the second solvent of the second salt solution evaporate to form the metal wire pattern by depositing the reduced first metal ion nanoparticle on the substrate.