Title: Nanogenerator-induced synaptic plasticity and metaplasticity of bio-realistic artificial synapses
Abstract: 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. An electronic component that mimics synapses in the brain has been created by a team in Korea. Mimicking the way the brain processes information in man-made devices could enable an entirely new way of computing that uses far less energy than conventional computers. Sahn Nahm from Korea University and co-workers created a circuit element known as a memristor that can switch between a high and low electrical resistance. They made it from (Na0.5K0.5)NbO3, or NKN, on a flexible substrate. NKN exhibits memristive properties due to the movement of oxygen vacancies and changes in shape of oxygen vacancy filaments. It is also piezoelectric, meaning that it generates an electrical current whenever it is moved, thus opening a route to self-powered biomedical devices. Bio-realistic flexible artificial synapses integrated with a nanogenerator were demonstrated for self-powered neuromorphic biomedical device applications. Biocompatible (Na0.5K0.5)NbO3 (NKN) was used in both memristors as an artificial synapse and a nanogenerator. Biological synaptic functions were produced in the NKN memristor driven by the NKN nanogenerator. Finally, metaplasticity was implemented in the integrated devices to facilitate bio-realistic functions in the artificial synapse.