A Light‐Stimulus Flexible Synaptic Transistor Based on Ion‐Gel Side‐Gated Graphene for Neuromorphic Computing

Abstract

Optogenetic technology is to express the channel proteins that can be act on light for realizing the activity of neurons activated and inhibited. Here, inspired by optogenetics, a flexible side‐gate artificial synaptic transistor based on ion gel and graphene is demonstrated, where the long‐term remembering or forgetting could be activated by the 450 nm light stimulus. Taking advantage of in‐plane‐field tunable carrier transport in graphene and the high ionic motion of ion gels, various synaptic functions under flatting or bending conditions by electric stimuli are successfully mimicked, including inhibition postsynaptic current, excitatory postsynaptic current, and paired‐pulse facilitation. A light‐induced forgetting or remembering is demonstrated by long‐term synaptic plasticity under 20 s and 10 Hz positive or negative gate pulse stimulus in the dark and 4 min recovery with light illumination. Moreover, the light stimulus promotes the associative learning and remembering function, which is demonstrated by Pavlov's dog experiment with electrical pulses and light stimulus. Such light‐assisted learning and memory function on synaptic plasticity can be attributed to the photogenerated electrons trapping effects in our device. The authors’ results provide a feasible strategy for realizing flexible light–electrical‐stimulus synaptic transistors and developing the low‐energy flexible neuromorphic optoelectronic hardware platform.

Manufacturing of graphene based synaptic devices for optoelectronic applications

“…On one hand, electron-hole carrier pairs can be generated in graphene with light illumination. The electrons, for example, could be partially trapped at defective sites of graphene or nearby materials while the holes as counterpart could regulate the channel conductance to mimic synaptic plasticity [142]. On the other hand, electron-hole pairs are generated in materials (molecules, QDs, nanowire, 2D materials, or bulk materials) or traps near graphene (figure 8(a)).…”

“…The classical Pavlov conditioning has been demonstrated by graphene-based electrolyte-gate transistor with light modulation [142]. The LTP of the synaptic device can be regulated by a blue light stimulus owing to the effective trapping of photo-generated electrons in graphene (figure 13(a)).…”

A synaptic phototransistor for image processing and memory

“…This depolarization leads to excitation of postsynaptic neuron, which is the excitatory postsynaptic potential (EPSP). The current generated during this process is the excitatory postsynaptic current (EPSC), which represents the synaptic strength or synaptic weight [13]. External stimuli can adjust the synaptic weight and thus change the efficiency of synaptic transmission.…”