A flexible resistive switching device for logical operation applications in wearable systems

As an emerging micro/nano device, memristor integrates functions, such as memory, sensing, and computing, and has similar internal dynamics to synapses, showing great potential in neuromorphic computing and logical operations. In this work, a flexible memristor with Al/TiO_x/Al/polyethylene terephthalate structure was developed to investigate the synergistic effect from the oxygen vacancy, H₂O molecule, and NaCl. A forming-free resistive switching (RS) behavior observed in the flexible memristor can be ascribed to the migration and accumulation of the oxygen vacancy and Schottky emission of the interfaces. This forming-free RS is sensitive to the NaCl and H₂O molecule because the Na⁺ migration disturbs the oxygen vacancy filament and interplay between oxygen vacancy and H₂O molecules. The variation conductance modulated by the concentration of NaCl and H₂O molecules can represent the weight update incrementally that the online learning required. Therefore, the memristor has the potential to be used as a biosensor in human tissues or to realize the brain-like chip, which points out the research direction for the extension function of the memristor in wearable systems.