Ultra-thin, Low-Noise Organic Transistor Integrated Devices for Minimally Invasive Brain Activity Measurement System

I will introduce process technologies for high mobility, low noise, and uniform characteristics of organic thin-film transistors that utilize the softness of organic materials, as well as a brain activity measurement system that utilizes these organic nanotechnologies.<br/><br/>In recent years, the flexibility and lightweight properties of organic electronics have attracted attention, and bio-applications, such as wearable applications, have been gaining momentum. In addition to high electrical characteristics, such applications require the simultaneous fulfillment of various properties such as uniformity of characteristics and biocompatibility that allow for large-scale integration. Organic transistors, in particular, have inherently non-uniform characteristics, and this trend will become more apparent over time.<br/><br/>In this study, we have realized organic thin-film transistors with high mobility (μ&gt;1 cm²/Vs) and low noise on polymer films less than 1 micrometer thick by using photosensitive materials and self-assembled monolayers as gate insulator films [1,2] and have successfully reduced the variation in threshold voltage (V_th) less than 4%. This implies a V_th variation of 10-70 mV for a drive voltage of 2V. [3].<br/><br/>By highly integrating this organic thin-film transistor with biocompatible materials [4], we have developed an ultra-thin-film measurement device that can minimally invasively measure minute cellular action potentials in living organisms [5-10]. In this presentation, we will introduce a scalp EEG measurement system that measures from outside the skull and a brain measurement system that measures from inside the brain in an extremely minimally invasive manner.<br/><br/>Furthermore, with the aim of expanding the application of ultra-thin film organic devices to a wider range of areas, we are currently conducting research and development of organic electrochemical transistors capable of controlling high currents [11].<br/><br/>These results were obtained in collaboration with Dr. Koki Taguchi, Associate Professor Takafumi Uemura, Associate Professor Teppei Araki, and other members of the SANKEN research group at Osaka University, and Dr. A. Petritz, Dr. B. Stadlober, and other research group members at JOANNEUM RESEARCH, Austria. This work was supported in part by JST Moon Shot Type R&D Project (JPMJMS2012), Grant-in-Aid for Scientific Research (22H00588), and Research Grant (S) from Tateishi Science and Technology Foundation.<br/><br/>[1] M. Kondo, et. al, ACS Appl. Mater. Interfaces 11, 41561 (2019).<br/>[2] M. Sugiyama, et. al, Organic Electronics 96, 106219 (2021).<br/>[3] K. Taguchi, et.al, Advanced Materials 33, 2104446 (2021).<br/>[4] T. Araki, et al. Advanced Healthcare Materials 8, 201900130 (2019).<br/>[5] M. Sugiyama, et. al, Nature Electronics 2, 351 (2019).<br/>[6] M. Kondo, et.al, Science Advances 6, eaay609 (2020).<br/>[7] T. Araki, et.al, Advanced Materials 32, 1902684 (2020).<br/>[8] A. Petritz, et.al, Nature Communications 12, 2399 (2021).<br/>[9] T. Araki, et.al, Advanced Materials Technologies 2200362 (2022).<br/>[10] K. Li, et.al, Science Advances 8, eabm4349 (2022).<br/>[11] T. Araki, et.al, Advanced Science (2022) in press.