Transparent and flexible ECoG electrode arrays based on silver nanowire networks for neural recordings

Abstract

This work explored hybrid films of silver nanowires (AgNWs) with indium-doped zinc oxide (IZO) for developing high-performance and low-cost electrocorticography (ECoG) electrodes.The hybrid films achieved a sheet resistance of 6 Ω/sq while maintaining a transparency of ≈60% at 550 nm. Electrodes with 500 μm diameter were fabricated with these films and reached an impedance of 20 kΩ at 1 kHz and a charge storage capacity of 3.2 mC/cm 2 , a 2× and 320× improvement over IZO electrodes, respectively. Characterization of light-induced artifacts was performed showing that small light intensities (<14 mW/mm 2 ) elicit electrical potential variation in the magnitude order of baseline noise. The validation of electrodes in vivo was achieved by recording electrical neural activity from the surface of rat cortex under anaesthesia. Moreover, the presence of the films did not cause obstruction of light during fluorescence microscopy.The presented film and electrode characterization studies highlighted the capabilities of this hybrid structure to fabricate transparent and flexible electrodes that are able to combine the superior temporal resolution of extracellular electrophysiology with the spatial resolution offered by optical imaging.

Opto‐E‐Dura: A Soft, Stretchable ECoG Array for Multimodal, Multiscale Neuroscience

“…[ 12 ] Optical imaging approaches, such as wide‐field and 2‐photon calcium imaging, enable cell type and pathway‐specificity, as well as long term stability through targeted expression of indicators. [ 21,22 ] However, they typically have low temporal resolution, require a trade‐off between field of view, resolution and temporal sampling rate, [ 23 ] and do not provide an absolute measurement because they are derived from changes in fluorescence.…”

Hybrid electrical and optical neural interfaces

“…Neto et al used combination of silver nanowires (AgNWs) and indium-doped zinc oxide (IZO) as their transparent material (figure 1(j)) [38]. Its performance showed 60% transparency and electrical impedance of 20 kΩ with an electrode size of 500 µm in diameter.…”