Interfacial Ionic Dynamics And Spike-rate Dependent Plasticity Simulation In MEH-PPV/Polymer Electrolyte Devices

In recent years,the explosive growth of data collection and dissemination has put forward much higher requirements for the storage and running speed of computers.Neural network computing draws lessons from the operation mode of the human brain,which can process data in parallel with high efficiently,and thus has attracted worldwide attentions.This work constructed MEH-PPV/polymer electrolyte artificial synaptic cells with polymer membrane structure resembling human organinc environment,and simulated the spike-rate dependent plasticity?SRDP?,one of the basic learning models in neurobiology,by regulating the ionic dynamics between organic macromolecular interfaces.We first fabricated Pt/MEH-PPV/PEO-Li CF₃SO₃/Pt cell,in which,negative differential resistance?NDR?phenomena appeared during direct current sweep?DC sweep?and indicated a dynamic process of ionic doping,spatial charge accumulation and discharging,which was the basis for latter synaptic simulation.Conventional spike-rate dependentplasticity?SRDP?learning model was realized,that the cell responded to depression upon low-frequencystimulation and to potentiation upon high-frequency stimulation,both effect of which presented long-term memory.The microstructure of MEH-PPV/PEO-Li⁺ interface was then characterized.Crystalline PEO was found to be arranged orderly on MEH-PPV layer and Li⁺ migrated through the amorphous region within the chain foldarea,the model of which resembled the conduction of biological neurotransmitters a lot.We put forward a random ionic channel model accordingly,that the number as well as barriers of activated ionic channels would vary with pulse input,which meant the state variable of ionic flux got changed,and successfully explained the processing machenism of SRDP simulation in our MEH-PPV/polymer electrolyte cells.Pt/MEH-PPV/PEO-Nd?CF₃SO₃?₃/Pt cell which introducedheavy ion Nd³⁺as migration media was then designed and fabricated,containing a similar microstructure with MEH-PPV/PEO-Li+ device but without initially Nd³⁺ doping.SRDP protocol could be only achieved under triangular waves but not under square waves,representing a selectivity to the type of electric signals.The possibility of bidirectional signal transfer has been tested simplyby anti-connecting two individual cells.The threshold where synaptic weight transformed from depression to potentiation,was found to be removable,the sliding behavior of which consisted well with BCM theory.Moreover,the effective input for frequencyselectivity was around the voltage inducing a negative differential resistance influenced by theloading rate.