Fig. 3: Synaptic plasticity emulation upon light stimuli.
From: Azobenzene-based optoelectronic transistors for neurohybrid building blocks
a Schematics comparing an OPECT with a biological synapse: when a square voltage pulse was applied at the gate, it acted as an action potential which reached the pre-synaptic terminal. This voltage pulse favoured the injection of cations from the electrolyte solution to the PEDOT:PSS channel in a similar manner of the chemical transduction of the information occurring during the neurotransmitters release from the pre-synaptic terminal. This signalling resulted in the ionic current at the post-synaptic membrane with a consequent conductance variation and, thus, a modulation of the Ids current can be recorded on the PEDOT:PSS channel of the OPECT. b Channel conductance measurement while electrical pulses were applied at the gate and light stimulus was not applied and then light was switched on (black and blue solid lines, respectively). Inset: light induced conditioning (blue line) and extinction in dark (red line). c Channel conductance measured at different light intensity (100, 60 and 20% blue, red and orange solid lines, respectively) by changing the PW: (i) 500 ms, (ii) 1 s and (iii) 5 s. d Channel conductance variation (conditioning) depending on PW of gate voltage pulses (PW: 500 ms, numerical values: 4.2 ± 0.6, 12.5 ± 3.1, 9.5 ± 2.1; PW: 1 s, numerical values: 2.7 ± 0.7, 11.8 ± 8.4, 9.1 ± 1.3; PW: 5 s, numerical values: 4.5 ± 2.5, 7.9 ± 1.7, 12.5 ± 3.1). e PPF index (Supporting Fig. 24) plotted vs. Δt; the measurement was carried out by applying two consecutive square voltage pulses with Vgs = 300 mV, PW = 1 s, Δt = 100 ms, 500 ms, 1 s, 3 s, 5 s, 8 s and 11 s). f LTP of azo-OPECT showing 500 stable conductance states and long-term memory after the irradiation with 500 light pulses (λ = 365 nm, 100% of light intensity, 1 s light on, 1 s light off); the conductance remained constant after the removal of the light stimulus.
