Inkjet catalyst printing and electroless copper deposition for low-cost patterned microwave passive devices on paper

A scalable, low-cost process for fabricating copper-based microwave components on flexible, paper-based substrates is demonstrated. An inkjet printer is used to deposit a catalyst-bearing solution (tailored for such printing) in a desired pattern on commercially-available, recyclable, non-toxic (Teslin®) paper. The catalystbearing paper is then immersed in an aqueous copper-bearing solution to allow for electroless deposition of a compact and conformal layer of copper in the inkjet-derived pattern. Meander monopole antennas comprised of such electroless-deposited copper patterns on paper exhibited comparable performance as for antennas synthesized via inkjet printing of a commercially-available silver nanoparticle ink. However, the solution-based patterning and electroless copper deposition process avoids nozzle-clogging problems and costs associated with noble metal particle-based inks. This process yields compact conductive copper layers without appreciable oxidation and without the need for an elevated temperature, post-deposition thermal treatment commonly required for noble metal particle-based ink processes. This low-cost copper patterning process is readily scalable on virtually any substrate and may be used to generate a variety of copper-based microwave devices on flexible, paper-based substrates.