Biodegradable oxide synaptic transistors gated by a biopolymer electrolyte

Biodegradable oxide synaptic transistors were fabricated on a graphene coated PET substrate. An acid doped chitosan-based biopolymer electrolyte is used as the gate dielectric. With the acid doping, a high proton conductivity of ∼7.6 × 10−4 S cm−1 and a big electric-double-layer capacitance of ∼1.0 μF cm−2 are observed for the biopolymer electrolyte. The fabricated oxide synaptic transistor exhibits good transistor performances, such as a low operation voltage of 1.0 V, a high field-effect mobility of ∼5.4 cm2 V−1 s−1, a high on/off ratio of ∼3.1 × 106 and a low subthreshold swing of ∼80 mV decade−1. With the unique proton gating behaviors, synaptic functions, such as excitatory post-synaptic current, paired-pulse facilitation and synaptic filtering were mimicked. Furthermore, the proposed oxide synaptic transistor could be dissolved in water in a short time. We believe that the proposed biodegradable synaptic transistors could provide new opportunities for low cost, portable “green” neuromorphic electronics.