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Nuan Chen1 2 Baiwen Luo2 Nitish Thakor2 Seeram Ramakrishna1

1, Department of Mechanical Engineering, National University of Singapore, Singapore, , Singapore
2, Singapore Institute for Neurotechnology (SINAPSE), National University of Singapore, Singapore, , Singapore

During the past decades, neural electrodes have been developed as promising interface technology for direct communication with the neural tissues for diagnosis of the nervous disorders and treatment of the injury. Considering the significant material mismatch between the external implant and native tissue, a thin coating is employed on the electrode sites as an intermediate layer to bridge the difference. However, great challenges still exist regarding the long-term performance of the electrode coating in vivo.
In this study, a tubular electrode coating made of poly(3,4-ethylenedioxythiophene) (PEDOT) and carbon nanotube (CNT) was designed, targeted to long-term neural recording. The PEDOT-CNT nanotube coating was fabricated and showed compatibility with flexible polyimide electrode. The coating exhibited a 3D network-like structure made of hollow tube with an outer diameter of ~700nm and wall thickness of ~90nm. The electroactivity of the PEDOT-CNT coating was investigated using electrochemical impedance spectroscopy and cyclic voltammetry. The coated electrode sites showed significantly decreased impedance and increase charge storage capacity compared to bared site, which would allow more charge transfer at the interface and increase the sensitivity during neural recording. To test the mechanical adhesion of the PEDOT-CNT nanotube coating, ultrasonic treatment was employed in the study. The PEDOT-CNT nanotube could sustain 20min sonication with less than 20% delamination area while the PEDOT-PSS nanotube showed more than 60% delamination area after 5min treatment. The incorporation of CNT significantly reinforced the nanotube structure and improved the mechanical durability against sonication which would address the delamination issue of PEDOT coating and support chronic recording. We have also studies the different deposition condition and their effects on the morphology, electrical property and mechanical property of the coating. In vitro culture of neurons showed positive neuron attachment and neurite extension on PEDOT-CNT nanotube immobilized with poly-lysine and laminin.

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