Ultrathin Metal based Transparent Flexible Microelectrode Array for Electro-Optical Neural Recording and Temperature Sensing
Hongki Kang a, Woongki Hong a, Jee-Woong Lee b, Eun Kyung Gu a, Yujin Hwang a, Duhee Kim a, Junhee Lee a, Anna Rostedt Punga b
a Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno-Jungang-Daero, Daegu, Korea, Republic of
b Uppsala University, Sweden, Uppsala, Sweden
Proceedings of Neural Interfaces and Artificial Senses (NIAS)
Online, Spain, 2021 September 22nd - 23rd
Organizers: Tiago Costa and Georgios Spyropoulos
Oral, Hongki Kang, presentation 016
DOI: https://doi.org/10.29363/nanoge.nias.2021.016
Publication date: 13th September 2021

Electro-optical neural interfacing technologies have been applied to offer both high temporal and high spatial resolution neural recording and stimulation. Optical neural stimulations such as optogenetics, photothermal stimulation have been successfully applied to various brain models. For the hybrid neural interface technologies, we must build optically transparent, mechanically flexible microelectrode arrays that can measure the neural signals without significant interference by light during the optical stimulations. While wide bandgap electrodes such as indium tin oxide have been traditionally used as the transparent electrodes, the mechanical brittleness of the material limits its application to in vivoor physically demanding environments. In this work, we developed ultrathin (<10 nm) metallic electrodes as the transparent and flexible microelectrode array. We used a biocompatible polyelectrolyte multilayer as the nucleation inducing seed layer for the ultrathin electrodes for enhanced electrical conductivity (<8 Ω/sq) while achieving high optical transmittance (>77%). In addition, we found that the strong electrostatic force formed by the charged polyelectrolytes altered the electrode-electrolyte interfaces of the electrode and significantly reduced the impedance and the baseline noise of the electrodes. Lastly, with the promising capability of the transparent neural electrodes, we also confirmed that the microelectrodes can be also used as reliable transparent temperature sensors.

This work was supported in part by the DGIST R&D Programs of the Ministry of Science and ICT (19-CoE-BT-03, 21-IJRP-01) and in part by an Ideas Grant from the National Health and Medical Research Council (NHMRC) of Australia (APP1188414).

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