Tissue-like interfacing of planar electrochemical organic neuromorphic devices

Organic neuromorphic devices are rapidly developing as platforms for computing, automation and biointerfacing. Resembling short- and long-term synaptic plasticity is a key characteristic to create functional neuromorphic interfaces showcasing spiking activity and learning capabilities. This further enables these devices for coupling with biological systems, such as living neuronal cells and ultimately the brain. However, this would require electrochemical neuromorphic organic devices (ENODes) to interface gel-like electrolytes where neurotransmitter can freely diffuse. To this end, we investigated how planar ENODes (electrochemical transistors) with different geometries and based on different PEDOT:PSS formulations can feature short-and long-term plasticity when in contact with diverse tissue-like gel electrolytes containing catecholamine neurotransmitters. We find both the composition of the bulk electrolyte and gate material play a crucial role in diffusion and trapping of cations that ultimately modulate the conductance of the transistor channels. Our work on ENODe-gel coupling could pave the way to effective brain interfacing for computing and neuroelectronic applications.