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.
Highlights
In neuroprosthetics, the realization of a performing interface between an implant and the soft tissue is of primary importance for both the preservation of the neuronal environment, and the correct functioning of the device (Lacour et al, 2016)
Soft electrodes consisting of a first layer of PEDOT:PSS and a second layer of CA have been electrodeposited on top of the Pt electrodes (Figures 1B,C)
The use of CA as a soft coating of microelectrode arrays (MEAs) is an attractive strategy to both reduce the mechanical mismatch at the electrodetissue interface and improve the electrochemical properties of microelectrodes (Green et al, 2012, 2016; Goding et al, 2017)
Summary
The realization of a performing interface between an implant and the soft tissue is of primary importance for both the preservation of the neuronal environment, and the correct functioning of the device (Lacour et al, 2016). CPs and CNTs are versatile carbon-based materials already exploited in the fabrication of several neuroprosthetic devices (Antognazza et al, 2015; Khodagholy et al, 2015; Feyen et al, 2016; Xiang et al, 2016; Ferlauto et al, 2018) Their incorporation in the active sites of recording or PEDOT:PSS/Alginate Soft Microelectrodes for Application in Neuroprosthetics stimulating neural devices is known to lower the impedance and the stiffness of metal electrodes, to allow both electronic and ionic charge transport, and to promote cell adhesion and proliferation (Abidian et al, 2010; Harris et al, 2013; Balint et al, 2014; Martin and Malliaras, 2016; Rivnay et al, 2016; Simon et al, 2016). Their tunable mechanical properties, high water content, high porosity, and soft consistency mimic the ones of living tissues; this makes hydrogels extremely attractive for neural prostheses
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