The goal of this year’s project was to investigate n-type conducting polymers as interfacial layers in microbial electrochemistry applications. Specifically, we are interested in the advantages and disadvantages of this type of material over the well-known p-type conducting polymer PEDOT:PSS in serving as an electrode and interfacial layer for extracellular electron transfer (EET) for the electroactive bacteria Shewanella oneidensis MR-1. The application for such electrodes is to enhance energy conversion performed by microbes facilitated via charge transfer directly and indirectly from microbes to the external circuit. Examples of such energy conversion applications can be sensing of analytes, bioremediation, wastewater cleaning, green energy generation and biosynthesis.

We perform this project in two main branches: (1) focusing on the basic electrochemical performance, as well as bacterial attachment to electrode films in microbial electrochemical systems (MES), and (2) evaluation of operation of organic microbial electrochemical transistor (OMECT) where the channel and gate are coated by the n-type polymer. For 2, we collaborate with Linkoping University, who supply partially finished OECT devices. In addition, we collaborate with a researcher in Tokyo University of Science to investigate the nanoscopic interfacial water layer at both p-type and n-type polymers, with the involvement of our student.

So far, we have found several interesting results related to the investigated topic, and reported them at the Spring Meeting of Japan Society of Applied Physics in 2024 March.

Currently, we are still performing experiments on the above topics, and expect to summarize our findings in two scientific publications in AY2025. The future aim of this technology is to find a well-matching material for bacterial electronics applications that allows electrical control of biological sensing and energy conversion utilizing non-harmful bacteria.