Biological synaptic function simulation using flexible electronic devices based on low-dimensional semiconductor materials is an emerging and rapidly evolving research field with promising applications in brain-like computers and artificial intelligence systems. In this work, we present the fabrication of solution compatible MoS2 thin-film transistors on the ultrathin polymethyl methacrylate substrates via layer-by-layer assembly followed by a one-step transfer printing method. The MoS2 transport channel is controlled by ionic liquid gating with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, resulting in excellent synaptic performances for emulating memory and perception synapse functions. To investigate the synaptic behaviors, we conduct a series of synaptic spike-dependent experiments and propose an advanced model that delineates the long-term plasticity and short-term plasticity with separate characteristic factors. These findings provide insights into the fundamental mechanisms of synaptic plasticity in electric double-layer devices and contribute to a better understanding of their synaptic performances. In addition, we examine the effects of bending conditions on synaptic plasticity and synaptic weights, unveiling the synergistic interplay between mechanical deformation and synaptic behaviors. Our experimental results, combined with the developed model, are in good agreement and shed light on the influence of mechanical flexibility on the synaptic properties of the devices. In summary, this study establishes a solid foundation for further development of flexible synaptic devices from both practical and theoretical perspectives.
Keywords: flexible synaptic transistors; ionic liquid; long-term plasticity; molybdenum disulfide; short-term plasticity.