Wafer-Scale Graphene-Based Soft Electrode Array with Optogenetic Compatibility

Abstract

This paper reports on the characterization of a microfabricated wafer-scale, graphene-based, soft implant for spinal cord applications. Graphene is used because of its high transparency and good conductivity, making it suitable for optogenetic applications. Moreover it has a high mechanical strength and is potentially biocompatible. The implant consists of multi-layered chemical vapor deposited graphene, in the form of electrodes and tracks, encapsulated between 2 layers of silicone. Methods such as Raman spectroscopy, optical transmittance, and electrical measurements combined with bending tests and in-vitro experiments, using phosphate-buffered saline (PBS) solution, were employed to characterize the device. The results have shown high bendability and no critical damage of the graphene after immersing the device in PBS solution up to 7 days. To the authors' best knowledge, this is the first work that presents a soft and fully scalable optogenetics-compatible graphene-based spinal cord electrode array.

Surface modification of multilayer graphene electrodes by local printing of platinum nanoparticles using spark ablation for neural interfacing

“…10 Recently developed multilayer CVD graphene electrodes, using a transfer-free fabrication process, reported an increase in CSC and impedance reduction due to an increase in the quantum capacitance as a result of using multiple graphene layers. 11,12 However, increasing the number of layers has only impact on the quantum capacitance up to a threshold of 6 layers, 10 while each added layer reduces the graphene's optical transparency. 11,13 Moreover, scaling down the electrode size is necessary to selectively record signals from targeted neurons.…”

Surface modification of multilayer graphene neural electrodes by local printing of platinum nanoparticles using spark ablation†

“…However, undoped monolayer graphene suffers from low sheet conductivity 9 and a low charge storage capacity (CSC) due to the dominance of its small quantum capacitance 10 . Multilayer CVD graphene electrodes have been recently reported using a transferfree fabrication process 11,12 . Although using multiple layers of graphene increases the quantum capacitance and consequently reduces the impedance and leads to higher CSC 11 , increasing the number of layers has only impact on the quantum capacitance up to a threshold of 6 layers 10 , while each added layer reduces the graphene's optical transparency 11,13 .…”