Seriography-Guided Reduction of Graphene Oxide Biopapers for Wearable Sensory Electronics

Novel nacre-mimic bio-nanocomposites, such as graphene-based laminates, are pushing the boundaries of strength and toughness as flexible engineering materials. Translating these material advances to functional flexible electronics requires methods for generating print-scalable microcircuits (conductive elements surrounded by dielectric) into these strong, tough, lightweight bio-nanocomposites. Here, a new paradigm for printing flexible electronics by employing facile, eco-friendly seriography to confine the reduction of graphene oxide biopapers reinforced by silk interlayers is presented. Well-defined, micropatterned regions on the biopaper are chemically reduced, generating a 10(6) increase in conductivity (up to 10(4) S m(-1)). Flexible, robust graphene-silk circuits are showcased in diverse applications such as resistive moisture sensors and capacitive proximity sensors. Unlike conductive (i.e., graphene- or Ag nanoparticle-loaded) inks printed onto substrates, seriography-guided reduction does not create mechanically weak interfaces between dissimilar materials and does not require the judicious formation of ink. The unimpaired functionality of printed-in graphene-silk microcircuits after thousands of punitive folding cycles and chemical attack by harsh solvents is demonstrated. This novel approach provides a low-cost, portable solution for printing micrometer-scale conductive features uniformly across large areas (>hundreds of cm(2)) in layered composites for applications including wearable health monitors, electronic skin, rollable antennas, and conformable displays.