Development and Characterization of PEDOT:PSS/Alginate Soft Microelectrodes for Application in Neuroprosthetics

Abstract

Reducing the mechanical mismatch between the stiffness of a neural implant and the softness of the neural tissue is still an open challenge in neuroprosthetics. The emergence of conductive hydrogels in the last few years has considerably widened the spectrum of possibilities to tackle this issue. Nevertheless, despite the advancements in this field, further improvements in the fabrication of conductive hydrogel-based electrodes are still required. In this work, we report the fabrication of a conductive hydrogel-based microelectrode array for neural recording using a hybrid material composed of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate), and alginate. The mechanical properties of the conductive hydrogel have been investigated using imaging techniques, while the electrode arrays have been electrochemically characterized at each fabrication step, and successfully validated both in vitro and in vivo. The presence of the conductive hydrogel, selectively electrodeposited onto the platinum microelectrodes, allowed achieving superior electrochemical characteristics, leading to a lower electrical noise during recordings. These findings represent an advancement in the design of soft conductive electrodes for neuroprosthetic applications.

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

“…This method creates a three-dimensional analog of the two-dimensional electrode surface. These coatings are collectively referred to as hydrogel polymer coatings, with PEDOT:PSS as the most well-known of these (Nyberg et al, 2002; Ferlauto et al, 2018). These polymers conduct electronic current and have the property of absorbing the surrounding electrolyte (e.g., body fluid) that allows for a capacitive interface between ions and electrons to form on a molecular scale throughout the polymer chains.…”

Wafer‐Scale Fabrication of Conducting Polymer Hydrogels for Microelectrodes and Flexible Bioelectronics

“…CPH have been suggested as suitable candidates for interfacial modification since they can combine both electrochemical and biochemical qualities in one material . In recent years, a wide range of different CPHs have been suggested as interesting candidates for neural probes and many studies have investigated the micropatterning of CPHs, for example, via photolithography, inkjet printing, mold casting, or electrodeposition . Alternatively, it is possible to coat the entire device with the hydrogel and subsequently deposit the conducting polymer into the hydrogel matrix, so that a conducting network is formed at the electrode surfaces only .…”

“…In an ideal scenario, the CPH can then be coated onto selected electrode sites, for example, as a drug‐release system, while other electrodes remain available for alternative functionalizations. A possible method for micropatterning CPHs, based on a phytic acid gelated polyaniline hydrogel by inkjet printing or spray coating, has been reported by Pan et al Other reported techniques include mold casting, photolithography, or electrodeposition . Several CPHs used for neural interfaces are based on dip coating the hydrogel onto the entire surface of the device followed by the deposition of the CP selectively at the electrode site .…”

All‐Printed Electrocorticography Array for In Vivo Neural Recordings

“…Impedance spectroscopy was performed between 10 Hz and 1 MHz with an AC voltage of 50 mV. CV was obtained by sweeping a cyclic potential at a speed of 50 mV s −1 between −0.6 and 0.8 V. For each electrode, the average response over five cycles was calculated …”