Fig. 2: OPECT operation under light conditions and retina visual pathway mimicking.
From: Azobenzene-based optoelectronic transistors for neurohybrid building blocks
a, b Transfer-characteristic and output curves at different light intensity (100%, 60%, 20% blue, red and orange solid line respectively). c Gate and channel currents measured while alternating 60 s of dark condition (black dashed line) and 60 s of UV light (black solid line), Vds = −200 mV and Vgs = 0 V: (i) a rapid increase in the Igs (from 310 nA to 414 nA) was observed (blue solid line) followed by an immediate decrease with a complete recover of the initial values after removing the light stimulus, (black dotted solid line), while (ii) shows a rapid decrease of Ids observed during light stimulation (blue solid line) while a rapid increase occurred when the stimulus was removed (black dotted line). d Normalised charge at the gate calculated by integrating Igs current vs. time (light intensity 100%) (numerical values: 0.054 ± 0.023 µC/s, 0.044 ± 0.036 µC/s and 0.042 ± 0.042 µC/s, N = 5). e Normalised charge at the gate calculated on the first pulse by integrating Igs current vs. time during UV irradiation of azo-tz-PEDOT:PSS at different light intensity (20%, 60% and 100%) (Numerical Values: 0.020 ± 0.012 µC/s, 0.058 ± 0.040 µC/s, 0.051 ± 0.022 µC/s, N = 3). f Retina schematics and visual pathways. (i): OFF vertical pathways responsible to stream the information that drives light to the brain involving three main cell layers: the signal flows from the photoreceptors to bipolar cells (BCs) and from BCs to ganglion cells (GCs). The secondary lateral pathway adjusts the gain of the pre-synaptic and post-synaptic involving horizontal cells (HCs) back to photoreceptors and from amacrine cells (ACs) to BCs34. In dark conditions, photoreceptors are in depolarised state, and they continuously release glutamate. Contrariwise, the light induces hyperpolarization; (ii) proposed equivalent circuit which emulated the retina behaviour. g Artificial retina lateral and vertical OFF pathway emulation: (i) retina lateral pathway where the applied pulse was ramped up from 0 to 300 mV; (ii, iii) OFF vertical pathway: electrical train pulses application both in dark and light conditions, respectively.
