Hydrogel‐Enabled Electrochemical Modulation of 2D Single‐Crystalline VO ₂ Films for Flexible Neuromorphic Electronics

Electrolyte‐gated transistors (EGTs) based on strongly correlated oxides show great promise as artificial synaptic devices due to their ionic–electronic coupling, which allows for significant conductance modulation, low‐bias operation, and long‐lasting memory states. However, there has been limited exploration of platelet‐based two‐dimensional (2D) crystalline VO 2 channels that can simultaneously achieve nonvolatile conductance programming, array‐level addressability, and flexible neuromorphic functionality. In this study, we present hydrogel‐gated EGTs utilizing chemical‐vapor‐deposition‐grown 2D‐crystalline VO 2 platelet channels. These devices exhibit sub‐1 V conductance programming, nonvolatile state retention, and reversible write–retain–erase capabilities at both the single‐device and 4 × 6 array levels. Spectroscopic analyses provide strong evidence for proton‐coupled electrochemical modulation within the VO 2 channel. Building on this programmable correlated‐oxide platform, we demonstrate a variety of synaptic functions, including paired‐pulse facilitation, spike‐number‐dependent plasticity, spike‐rate‐dependent plasticity, long‐term potentiation/depression, and spike‐timing‐dependent plasticity. Furthermore, after being transferred to flexible substrates, the devices continue to exhibit robust analog potentiation/depression under tensile and compressive strain, as well as repeated bending. The experimentally determined synaptic weights also support stable handwritten‐digit recognition in a simulated neural network. These findings establish hydrogel‐gated 2D‐crystalline VO 2 EGTs as a mechanically compliant and array‐addressable correlated‐oxide platform for flexible neuromorphic electronics.