Abstract
We report on the superior electrochemical properties, in-vivo performance and long term stability under electrical stimulation of a new electrode material fabricated from lithographically patterned glassy carbon. For a direct comparison with conventional metal electrodes, similar ultra-flexible, micro-electrocorticography (μ-ECoG) arrays with platinum (Pt) or glassy carbon (GC) electrodes were manufactured. The GC microelectrodes have more than 70% wider electrochemical window and 70% higher CTC (charge transfer capacity) than Pt microelectrodes of similar geometry. Moreover, we demonstrate that the GC microelectrodes can withstand at least 5 million pulses at 0.45 mC/cm2 charge density with less than 7.5% impedance change, while the Pt microelectrodes delaminated after 1 million pulses. Additionally, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was selectively electrodeposited on both sets of devices to specifically reduce their impedances for smaller diameters (<60 μm). We observed that PEDOT-PSS adhered significantly better to GC than Pt, and allowed drastic reduction of electrode size while maintaining same amount of delivered current. The electrode arrays biocompatibility was demonstrated through in-vitro cell viability experiments, while acute in vivo characterization was performed in rats and showed that GC microelectrode arrays recorded somatosensory evoked potentials (SEP) with an almost twice SNR (signal-to-noise ratio) when compared to the Pt ones.
Highlights
Improves the signal-to-noise ratio (SNR) and allows for miniaturization), wider electrochemical windows that prevent faradaic reactions, and higher charge injection capabilities that enable more efficient electrical stimulation of the nervous tissue[15,16,17,18,19,20,21,22,23,24]
We report on a new class of neural prostheses, fabricated with Glassy carbon (GC) electrodes housed in an ultra-flexible, thin-film polyimide substrate that is able to leverage the superior electrochemical stability of glassy carbon along with the improved biocompatibility of thin-film devices
We present the superior recording and stimulating capabilities of a new neural electrode material, glassy carbon, with respect to traditional noble metal (Pt) electrodes integrated into thin-film devices
Summary
Improves the signal-to-noise ratio (SNR) and allows for miniaturization), wider electrochemical windows that prevent faradaic reactions, and higher charge injection capabilities that enable more efficient electrical stimulation of the nervous tissue[15,16,17,18,19,20,21,22,23,24]. We compare GC and Pt as substrates for Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS), a highly conductive polymer with great chemical stability that is often used[16,18,22,23,35,36,37,38,39,40] to improve electrochemical performances when electrode miniaturization[41] and high-density spatial arrays are required We believe that these wide spectra of in vitro and in vivo results demonstrate that GC electrodes offer a new and compelling material for neural recording and stimulation
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