Bio‐Inspired Organic Synaptor with In Situ Ion‐Doped Ultrathin Polyelectrolyte Containing Acetylcholine‐Like Cation

Abstract An ion‐based synaptic transistor (synaptor) is designed to emulate a biological synapse using controlled ion movements. However, developing a solid‐state electrolyte that can facilitate ion movement while achieving large‐scale integration remains challenging. Here, a bio‐inspired organic synaptor (BioSyn) with an in situ ion‐doped polyelectrolyte (i‐IDOPE) is demonstrated. At the molecular scale, a polyelectrolyte containing the tert‐amine cation, inspired by the neurotransmitter acetylcholine is synthesized using initiated chemical vapor deposition (iCVD) with in situ doping, a one‐step vapor‐phase deposition used to fabricate solid‐state electrolytes. This method results in an ultrathin, but highly uniform and conformal solid‐state electrolyte layer compatible with large‐scale integration, a form that is not previously attainable. At a synapse scale, synapse functionality is replicated, including short‐term and long‐term synaptic plasticity (STSP and LTSP), along with a transformation from STSP to LTSP regulated by pre‐synaptic voltage spikes. On a system scale, a reflex in a peripheral nervous system is mimicked by mounting the BioSyns on various substrates such as rigid glass, flexible polyethylene naphthalate, and stretchable poly(styrene‐ethylene‐butylene‐styrene) for a decentralized processing unit. Finally, a classification accuracy of 90.6% is achieved through semi‐empirical simulations of MNIST pattern recognition, incorporating the measured LTSP characteristics from the BioSyns.