Multilevel Nonvolatile Memcapacitance in Graphene‐Silk Fibroin Biocomposite Paper

The demand for flexible memory devices is growing due to the development of flexible neuromorphic electronics for wearable devices, soft robotics, and biologically‐inspired circuits. Described herein is a flexible memcapacitor based on a biocomposite paper composed of reduced graphene oxide (rGO) and silk fibroin (SF) via a gel‐film transformation process. The presented rGO‐SF/H3PO4‐polyvinyl alcohol (PVA)/rGO memory stack exhibits analog, reversible, and nonvolatile memcapacitance characteristics. Impressively, the stack has a broad range of high capacitance states so as to be tuned to at least four capacitive states by the operating voltages. This memcapacitive behavior is ascribed to an interfacial charge build‐up (capacitive double layer) modulated by the H+ migration, which is trapped/detrapped by the rGO‐SF paper depending on bias conditions. Further, the flexibility tests are conducted to confirm the applicability of the rGO‐SF/H3PO4‐PVA/rGO stack to flexible devices. Thus, the rGO‐SF papers can be used as electronic materials for capacitive memory in neuromorphic systems where operation at biocompatibility, low‐energy, and mechanical flexibility are important issues.