Engineering Mixed Conductor Transport and Device Form Factor for Neuromorphic Applications

Materials processing and synthetic design serve as ideal avenues to control the transport properties of organic mixed ionic/electronic conductors (OMIECs). Small changes in chemistry can affect the materials electronic mobility, swelling, ion uptake and stability. Devices based on these materials have thus opened up new opportunities in bioelectronics, energy, and neuromorphic computing. Furthermore, volumetric/bulk transport and charging in organic mixed conductors opens up opportunities for less common device form factors that can result in scaled down and co-localized function in circuits. In this talk I will present on the engineering of OMIECs for artificial synapses, as well as recent efforts to improve artificial neurons by engineering highly non-linear responses. I will first present a non-volatile organic electrochemical transistor (OECT) based on a poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos)/ Polytetrahydrofuran (PTHF) composite. This device can continuously and reversibly change its conductance state at a write bias less than 0.8 V and the state retention time can be longer than 200 min without decoupling the write and read operation. By incorporating a pressure sensor and a photoresistor into the gate terminal of volatile and non-volatile OECTs, a neuromorphic circuit is demonstrated with the ability to associate two physical inputs (light and pressure), which may have implications for biomimetic devices like electronics-skin and neuroprosthetics. I will then discuss recent developments in simple co-localized OECTs for on-site amplification, as well as for fine tuning of gaussian (or anti-ambipolar) responses in vertical OECTs for simplified spiking circuits, which present an exciting pathway for fully integrated artificial neurons that can directly interface with biological systems.