Nanogenerator-induced synaptic plasticity and metaplasticity of bio-realistic artificial synapses

A bio-realistic artificial synapse integrated with a nanogenerator (NG), which can be used in neuromorphic systems, is demonstrated for self-powered biomedical devices in this study. Biocompatible amorphous (Na0.5K0.5)NbO3 (NKN) films are grown on TiN/polyimide substrates to synthesize NKN memristors for use as artificial synapses. Various synaptic functions are realized in NKN memristors, which are driven by a pulse generator and an NG. The synaptic plasticity of the NKN memristor results from the oxygen vacancy movements and the changes in the shape of the oxygen vacancy filaments. As a further step toward developing more bio-realistic artificial synapses, various types of metaplasticity and their mechanisms in the NKN memristors are investigated. Moreover, the metaplasticity of spike-timing-dependent plasticity (a key characteristic of biological synapses) is realized in the NKN memristor with a priming stimulus given by the NKN NG.