Fig. 1 Schematic diagrams of electric-double-layer synaptic transistor (a) and biological synapse (b)

Fig. 2 Research on synaptic transistor on PI substrate (a) Image of In2O3 nanofiber synaptic transistor on PI substrate[29]; (b) Optical response of EPSC triggered by different light intensities[30]; (c) Relationship between amplitude of EPSC response to presynaptic peak (2.0 V, 25 ms) and gate pressure[31]; (d) Accuracy of simulated neural network for pattern recognition of MNIST small digit (8×8 pixels) database[29]; Colorful figures are available on website

Fig. 3 Research on synaptic transistor on PEN substrate[36] (a) Schematic diagram of a synaptic transistor constructed on a PEN substrate; (b) Variation trend of the postsynaptic current with the number of bending, and curvature radius at 0.8 cm during the test; (c) Schematic diagram of a pain perception model caused by UV stimulation; (d) Pain facilitation index increased with the increase of UV intensity; (e) Change of pain de-facilitation index with ΔT

Fig. 4 Research on synaptic transistor on PET substrate (a) Physical photograph of the construction of synaptic transistors on a PET substrate; (b) Change of current with time after 20 (4.0 V, 20 ms) pulses being applied to the gate of the synaptic transistor when VDS at 0.5 V [39]; (c) Schematic diagram of spatio-temporal signal integration and memory performed by heterogeneous synapses (with the introduction of noise signals during the transmission of the original signal); (d) Comparison of classification accuracy of two-gate heterogeneous synaptic transistor and single-gate homogeneous synaptic transistor networks[41]

Fig. 5 Research on synaptic transistor on mica substrate (a) Synaptic plasticity of synaptic transistors constructed on mica substrate[45]; (b) Optical photographs of flexible VO2 transistors constructed on mica substrate; (c) EPSC count chart to assess pain intensity; (d) Simulation identification accuracy of ideal devices and VO2 transistor devices[49]; EPSC: Excitatory post-synaptic current

Fig. 6 Research on synaptic transistor on paper substrate[52] (a) Schematic diagram of the chitosan /IZO synaptic transistor constructed on paper substrate; (b) Optical photographs of bent synaptic transistors on a paper substrate; (c, d) Simulated biological synaptic function on paper synaptic transistors

Fig. 7 Research on synaptic transistor on other self-support substrate (a) Organic synaptic transistor based on PDMS substrate and its excellent mechanical stability[54]; (b) Pain thresholds of independent artificial nociceptors at different modulation voltages; (c) Pain response currents of independent artificial nociceptors at different modulation voltages[56]

Fig. 8 Research on flexible neuron transistor (a) Schematic diagram of IZO-based neuron transistor measurement; (b) pH sensitivity of the device with different VG1[61]; (c) Change of the estimated recognition rate of pattern recognition with the number of training under three conditions according to different exposure time; (d) Classification test confusion matrix under three different conditions ("Good", "Yeah" and "OK") after different exposure time and number of iterations[62]