CPOS Seminar: Ion-dependent properties of organic mixed conductors and electrochemical transistors.

Speaker: Dr. Matteo Cucchi, Ecole Polytechnique Federal Lausanne, NeuroX Institute  / Technische Universität Dresden, IAPP

Abstract: The interest in organic mixed ionic/electronic conductors (OMIECs) rose steadily in the last 15 years pushed by their potential in bioelectronic applications and neuromorphic computing. A peculiar ion-electron coupling is at the heart of it. Such an effect can be harnessed to produce organic electrochemical transistors (OECTs) with impressive figures of merits, as well as artificial synapses, neural networks, memories, biosensors etc.  Despite the great advances in device development and material design, our physical understanding of the basic mechanisms that underlie the operation of OMIECs and OECTs is only partial. OECTs are typically treated like traditional field-effect transistors, an approach that neglects the chemical interactions between polymer and ions. A number of extended models have been put forth, each of them capable of explaining segments of the missing knowledge.                                                                                      In my talk, I will propose a new way of looking at OECTs. For this, the traditional view of a field-effect transistors must be left behind and leave space to a more sophisticated picture where ions and electrons mix and interact. Basic thermodynamic axioms can be used to describe such a system and even obtain closed-form equation for the modelling. Experimental evidence, in form of electrical and thermal measurements, supports the theoretical model excellently.  Finally, I will show how this theoretical approach could theoretically lead to paradoxical effects, such as a bistability behavior never observed. We successfully designed a device to feature a bistable behavior and we found that this is the underlying mechanism behind a number of neuromorphic effects already observed but never explained, such as non-volatility and hysteresis.

Bio: Dr. Matteo Cucchi earned his Bachelor Degree in Material Science at the University of Rome Tor Vergata followed  by a Master degree in Organic and Molecular Electronics at the Technische Universitat Dresden (TUD). He then pursued a PhD in Prof. Karl Leo’s group at TUD.  His doctoral work focused on the development of biocompatible networks made of organic mixed ionic/electronic conductors (OMIECs) and resulted in the first demonstration of a biocompatible and implantable computational platform capable of distinguishing healthy and arrhythmic heartbeats using on-chip machine learning. In parallel, he developed a thermodynamics-based framework to better model, understand, and design OMIECs.  In 2022, he joined the group Prof. Lacour at EPFL, Lausanne, Switzerland, to pursue a post doc focused on the design, microfabrication and characterization of spinal implants to restore motor functions in paralysed mice.