High-resolution, high-aspect ratio conductive wires embedded in plastic substrates

A novel method is presented to fabricate high-resolution, high-aspect ratio metal wires embedded in a plastic substrate for flexible electronics applications. In a sequential process, high-resolution channels connected to low-resolution reservoirs are first created in a thermosetting polymer by imprint lithography. A reactive Ag ink is then inkjet-printed into the reservoirs and wicked into the channels by capillary forces. These features serve as a seed layer for copper deposition inside the channels via electroless plating. Highly conductive wires (>50% bulk metal) with minimum line width and spacing of 2 and 4 μm, respectively, and an aspect ratio of 0.6 are obtained. The embedded wires exhibit good mechanical flexibility, with minimal degradation in electrical performance after thousands of bending cycles.