Chronic intracortical neural recordings using microelectrode arrays coated with PEDOT–TFB

Abstract

Microelectrode arrays have been extensively utilized to record extracellular neuronal activity for brain-machine interface applications. Poly(3,4-ethylenedioxythiophene) (PEDOT) has gained interest because of its unique electrochemical characteristics and its excellent intrinsic electrical conductivity. However, the long-term stability of the PEDOT film, especially for chronic neural applications, is unclear. In this manuscript, we report for the first time the use of highly stable PEDOT doped with tetrafluoroborate (TFB) for long-term neural recordings. We show that PEDOT-TFB coated microelectrodes on average register more units compared to control gold microelectrodes for at least first four weeks post implantation. We collected the in vivo impedance data over a wide frequency spectrum and developed an equivalent circuit model which helped us determine certain parameters to distinguish between PEDOT-TFB microelectrodes with and without long-term activity. Our findings suggest that PEDOT-TFB is a chronically stable coating for neural recording microelectrodes. As such, PEDOT-TFB could facilitate chronic recordings with ultra-small and high-density neural arrays.

Electrodeposited PEDOT:Nafion Composite for Neural Recording and Stimulation

“…Among the variety of materials available, poly(3,4‐ethylene dioxythiophene) (PEDOT) is the most widely used CP in the neurosciences due to its superior electrochemical properties, enhanced stability, and established biocompatibility . Apart from a limited number of reports on the use of alternative dopants for PEDOT, including smaller monoanionic counter‐ions such as perchlorate or tetrafluoroborate, the most used dopant is polystyrene‐sulfonate (PSS), thus yielding PEDOT:PSS . It was reported that PEDOT:PSS is better suited than IrOx as a coating material for safe and efficient neural stimulation .…”

64-Channel Carbon Fiber Electrode Arrays for Chronic Electrophysiology

“…While successful, this technique is difficult to scale to high-channel-count arrays. To get around this problem, we turned to chemical treatment of the tips, first etching the tips using sulfuric acid in order to roughen the tip surface and increase the surface area 28,29 , then electroplating the tips with PEDOT-TFB, which was previously shown to reduce impedance 30,31 (Fig. 1e).…”

“…The recording sites were prepared by cutting the array bundles to the desired length for implantation (~1mm for the visual cortex implants described here) using serrated scissors (Fine Science Tools, 14058-11), then dipping the tips into 99% sulfuric acid (Sigma, 339741-500ML) for 5 minutes, then (after washing any remaining acid off with water), by electroplating with PEDOT-TFB 30,31 by applying a 2nA current via a 10V power supply in series with a 5000MΩ resistor (Digikey, SM102035007FE-ND), for 1 minute (for a total charge delivery of 120nC) per electrode 25 . The electroplating solution consisted of 0.01M EDOT (Sigma, 483028-10G) and 0.1M tetrabutylammonium tetrafluoroborate (TFB) (Sigma, 86896-25G) in acetonitrile (Sigma, 360457-500ML).…”

“…Here we demonstrate the design of 64-channel CFEAs and a method for bulk preparation of the recording sites. The tips were prepared by etching with sulfuric acid in order to increase surface area 28,29 , followed by electroplating with PEDOT-TFB 30,31 , resulting in a dramatically decreased impedance. Recordings in rat visual cortex demonstrate the feasibility of recording neural signals with this method.…”

Organic bioelectronics in medicine

“…It has also been shown that whilst PEDOT:pTS seems to lose some charge storage capacity during ethylene oxide sterilization and under continued biphasic current‐controlled stimulation, the charge storage capacity is still significantly higher in the PEDOT:pTS‐coated electrodes compared to the uncoated Pt electrodes. Further, and most importantly, using conducting polymer coatings, it is possible to keep impedance low whilst decreasing the size of stimulation electrodes .…”