Fig. 5: Self-healing neuromorphic elements—satellite weight adjusting resistive memories (SWARMs).

a Short-term plasticity. A pair of presynaptic action potentials (+1.5 V, pulse width = 20 ms, interval = 10 ms) triggers a pair of excitatory postsynaptic currents (EPSCs) with increasing amplitude. This phenomenon known as paired-pulse facilitation (PPF) reflects the number of residual carriers during the ion migration-relaxation kinetics (left). Reversal of polarity of the presynaptic action potentials (−1.5 V) result in paired-pulse depression (PPD) with the indices dependent on pulse width and interval of the presynaptic action potentials, similar to facilitation (right). PPF/D indices, defined as [\({\mathrm{PPF}}/{\mathrm{D}} = \left( {\frac{{{{A}}_2}}{{{{A}}_1}}} \right) \times 100{\mathrm{\% }}\))] is plotted as a function of inter-spike interval to demonstrate the decay process. b Long-term plasticity. Electrical characterizations of spike-timing-dependent plasticity (STDP) recorded on SWARMs at various stages of the damage and healing process. c Controlled long-term potentiation (LTP) and depression (LTD) achieved in SWARMs over 500 switching transitions by applying a series of potentiating (+1.5 V) and depressing (−1.5 V) presynaptic spikes. Each programming/erasing step consists of 10 spikes of pulse width 500 ms. The figure represents the cycle-to-cycle variations during programming and erasing. The error bars capture the device-to-device variations obtained from 20 devices. The LTP and LTD weight updates do indicate higher variations after damage, but the trend of the overall the weight update traces remain consistent even after severe mechanical damage to the ion gel dielectric.