High-resolution, low-resistance, flexible metal interconnects that are many centimeters long were additively manufactured on plastic substrates using a roll-to-roll compatible print and plate process. Connected networks of ink-receiving reservoirs and capillary microchannels were first roll-to-roll molded on plastic films. Silver ink was jetted into the easily-targeted ink-receiving reservoirs, and the connected microchannels were fed and coated with ink by capillary flow and drying. Subsequent electroless plating of copper into the silver-coated channels created solid, high aspect ratio conductive traces. Processing windows for uniform silver deposition were identified as a function of ambient humidity, ink flow time, and channel geometry. Plating conditions were also optimized to alleviate copper stress development and debonding and to allow conductor flexibility. Overall, the optimized print-and-plate process is promising for additively manufacturing micron-scale, high aspect ratio (>1), low-resistance (linear resistance ∼1 ω/cm) conductors embedded in plastic, addressing a long-standing fabrication challenge for flexible printed electronics.
Bibliographical noteFunding Information:
This work was supported by the National Science Foundation (NSF award no. CMMI-1634263). K.S.J. gratefully acknowledges support from the NSF Graduate Research Fellowship Program under grant no. (00039202). The authors thank Dr. Donghoon Song, Wieslaw Suszynski, Dr. Mike Manno, Dr. Nathan Mara, and Demetra Adrahtas for valuable discussion. Parts of this work were carried out in the Characterization Facility, University of Minnesota, which receives partial support from the NSF through the MRSEC program. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Coordinated Infrastructure Network (NNCI) under award number ECCS-1542202.