Research Article: An Evolvable Organic Electrochemical Transistor for Neuromorphic Applications

Date Published: February 04, 2019

Publisher: John Wiley and Sons Inc.

Author(s): Jennifer Y. Gerasimov, Roger Gabrielsson, Robert Forchheimer, Eleni Stavrinidou, Daniel T. Simon, Magnus Berggren, Simone Fabiano.


An evolvable organic electrochemical transistor (OECT), operating in the hybrid accumulation–depletion mode is reported, which exhibits short‐term and long‐term memory functionalities. The transistor channel, formed by an electropolymerized conducting polymer, can be formed, modulated, and obliterated in situ and under operation. Enduring changes in channel conductance, analogous to long‐term potentiation and depression, are attained by electropolymerization and electrochemical overoxidation of the channel material, respectively. Transient changes in channel conductance, analogous to short‐term potentiation and depression, are accomplished by inducing nonequilibrium doping states within the transistor channel. By manipulating the input signal, the strength of the transistor response to a given stimulus can be modulated within a range that spans several orders of magnitude, producing behavior that is directly comparable to short‐ and long‐term neuroplasticity. The evolvable transistor is further incorporated into a simple circuit that mimics classical conditioning. It is forecasted that OECTs that can be physically and electronically modulated under operation will bring about a new paradigm of machine learning based on evolvable organic electronics.

Partial Text

Researchers have drawn analogies between computers and the mind since the age of the Turing machine.1 Unlike the binary logic of conventional silicon‐based circuitry, however, the brain relies on the adjustment of synaptic weights to integrate complex, parallel, and multidimensional stimuli to perform computations, which then instruct appropriate response actions.2

We report an evolvable organic electrochemical transistor that mimics the biological synapse, exhibiting short‐ and long‐term potentiation and depression. We fabricate the transistor channel on a set of prepatterned source and drain electrodes, producing the first synaptic device that can generate new synapses within its working environment similarly to how biological synapses establish, evolve, and operate.

Device Fabrication: Silicon substrates with a 1 µm thermally grown oxide layer were cleaned by sequential sonication in 2% Hellmanex, DI water, acetone, and isopropanol. Source and drain electrodes (2 nm Cr, 50 nm Au) were thermally evaporated on the substrate using an evaporation mask (Source–Drain Deposition Mask for Low Density OFETs, Osilla Ltd, UK).

The authors declare no conflict of interest.




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