Uncovering Ion-Electron Interactions in Organic Mixed Conductors

Informations projet

UMICs

N° de convention de subvention: 101022365

DOI

10.3030/101022365

Projet clôturé

Date de signature de la CE 2 Mars 2021

Date de début 10 Mai 2021

Date de fin 9 Mai 2023

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 224 933,76

Contribution de l’UE

€ 224 933,76

Coordonné par

THE CHANCELLOR MASTERS AND SCHOLARS OF THE UNIVERSITY OF CAMBRIDGE
United Kingdom

Periodic Reporting for period 1 - UMICs (Uncovering Ion-Electron Interactions in Organic Mixed Conductors)

Période du rapport: 2021-05-10 au 2023-05-09

Résumé du contexte et des objectifs généraux du projet

Organic mixed ionic-electronic conductors (OMIECs) have risen as a promising material choice for bioelectronic and biochemical devices due to their low impedance, soft mechanical properties, and ability to transduce ionic signals to electronic currents. The ion-electron interactions, which are unique to mixed conductors, have been exploited to produce high performance sensors and physiological recording devices. However, the fundamental interactions between ions and electrons that determine the performance of these materials is still poorly understood, impeding their translation from academic research to commercial use. The proposal addresses this gap in knowledge using state-of-the-art electronic and chemical analysis at the nanoscale to better understand the macroscale materials properties.

Our methodology focused on the kinetics of bioelectronic device operation. We found an accurate way to predict speed of operation by understanding how ion-electron interactions alter the transport properties in OMIECs. Furthermore, we discovered a new fundamental speed limit for switching bioelectronic devices from the OFF to the ON state. We show that the quickest path to overcoming this speed limit is to maximize the homogeneity of the OMIEC nanostructure. The fundamental insights resulting from this project inform the design of next-generation high-speed bioelectronic devices and materials, helping them advance beyond the lab into commercial and clinical applications.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

Using a newly developed optical microscopy methodology, we made two important discoveries regarding the kinetics of OMIEC operation. The results from the new method resulted in a more accurate interpretation of commonly used experimental technique to characterize ion transport enabling improved engineering of devices and benchmarking of materials. First, we found that charging and discharging rates are determined by the diffusion coefficient of charge paired ions and electrons. When paired, electronic charges move via diffusion due to large chemical energy required to charge the OMIEC, while ions followed the motion of electrons via drift which is must faster than ionic diffusion. The results are currently under review at an open access journal for eventual dissemination.

We used the optical microscopy to study a handful of OMIECs and found that the technique can differentiate between ionic and electronic limited motion. From this, we found that at very low electronic carrier concentrations, electronic motion is slower than ionic motion thereby limiting the operational speed of a device. We used diffraction-based transmission electron microscopy to image the nanoscale order of OMIECs, revealing that heterogenous order causes the slow electronic motion.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Organic mixed ionic-electronic conductors (OMIECs) have risen as a promising material choice for bioelectronic devices due to their low impedance, soft mechanical properties, and ability to transduce ionic signals to electronic currents. The ion-electron interactions, which are unique to mixed conductors, have been exploited to produce high performance sensors and electrophysiological recording devices. Our research has shown how these ion-electron interactions impact the performance of devices. We found that the switching kinetics of OMIEC devices is largely dependent of the ion-electron coupling. We propose several new ways to improve the speed of operation for bioelectronics, including controlling the materials microstructure and using optimised device operating parameters.

The insights from the research performed in this project will aid in the design of novel organic electronic materials for bioelectronic devices. With better materials, we expect organic bioelectronics to have great impact on the future of healthcare. Organic materials can be used to make bioelectrodes which cause much lower immune response compared to their metal counterparts. Additionally, the volumetric scaling of the charge capacity of OMIECs enables stimulation electrodes with orders of magnitude higher charge injection capacity that can operate at low frequencies down to 1 Hz. These properties of OMIECs open the path towards chronically stable implantable electronics, and the better understanding resulting from the project will directly help to translate these devices from research to clinical applications.

Relationship between microstructure and switching speed in conjugated polymers

Artist illustration of electrons and holes conducting in a conjugated polymer