Session: 03-07-01: Material Processing of Flexible/Emerging Electronics, Sensors, and Devices I

Paper Number: 100161

100161 - Porous Graphene-Based Neural Electrode for Highly Efficient Peripheral Nerve Stimulation 

Recent research has explored the development of a neural electrode that is able to record the biosignals of an individual neuron while delivering a sufficient amount of electrical charge for neural stimulation. Conventional neural electrodes are mostly based on metals such as platinum (Pt), gold (Au), and iridium oxide (IrOx). However, the low charge Storage capacity (CSC) (i.e., Pt has CSC below 1.2 mC cm^-2), limited charge injection capacity (CIC) (0.05–0.26 mC cm^-2), high impedance, poor electrochemical properties, and low electrochemical stability of conventional metal-based electrodes have limited the use of metal-based electrodes for highly efficient stimulation. The limited CIC and CSC of conventional metal-based electrodes emanate from their low surface area, which is detrimental to their electrochemical performance. Various methods have been used to improve the electrochemical properties and charge storage capacity (CSC) of metal-based electrodes by coating techniques to make composite materials such as Pt- iridium oxide, Pt- titanium nitride, and Pt-PEDOT. However, the CSC of these composite materials is limited to less than 80 mC cm^-2. The surface area and thereby CSC of neural electrodes have also been enhanced up to 50 mC cm^-2 by making three-dimensional (3D) materials with porous structures such as nanoporous Pt, nanoporous metal oxides, nanoporous metal nitrides, and laser-induced porous graphene. Notably, fabricating electrodes based on composite and porous structures requires a complicated and costly manufacturing process. Here, we present a nerve electrode based on 3D porous graphene derived from transparent fluorinated polyimide (fPI-3DPG) via a direct laser scribing method with high CSC for highly efficient neural stimulation. The CSC of fPI-3DPG electrodes is around one order of magnitude higher than 3DPG derived from polyimide (PI-3DPG), more than one order of magnitude higher than carbon-based materials (i.e., porous diamond and CNTs), more than two orders of magnitude higher than graphene-based materials such as single layer graphene (SLG) and doped-SLG. The fPI-3DPG is synthesized using a scalable, low-cost, and single-step laser photothermal approach, which makes heterogeneous micro/meso/macroporous graphene structures with enhanced specific surface area, thereby enhancing its electrochemical performance. The superior specific surface area and abundant micropores of the fPI-3DPG facilitate the accessibility of electrolyte and ion penetration into the electrode together with enabling the accumulation of more electrons in the interconnected pores with an ultrahigh CSC. The fPI-3DPG electrodes have high stimulation cycles endurance under one million stimulation cycles as well as mechanical flexibility and reliability under 10,000 cycles of bending. Our laser manufacturing method enables the fabrication of a highly flexible fPI-3DPG electrode to conformably contact with the lobster’s nerve for neural stimulation. The synergistic effects of ultrahigh charge storage capacity of fPI-3DPG, and high transparency of fPI film and graphene show future potential for integrating imaging-based identification of peripheral nerve with simultaneous highly efficient neural stimulation.

Presenting Author: Shirin Movaghgharnezhad George Mason University

Presenting Author Biography: I am Shirin Movaghgharnezhad, a Ph.D. candidate in the Mechanical Engineering Department at George Mason University. I joined Dr. Kang’s research group in Fall 2019 as a graduate research assistant. My research is focused on the laser-based manufacturing of micro-/nano-structured graphene as multifunctional materials for optoelectronics, electrochemical sensing, and bioelectrodes for wearable health applications. I expect to graduate in Fall 2022.

Authors:

Shirin Movaghgharnezhad George Mason University
Hyojin Kim Korea Research Institute of Chemical Technology
Byoung Ga Kim Korea Research Institute of Chemical Technology
Pilgyu Kang George Mason University