Biology subjects

Fortunato, E.

Publications and source records attributed to Fortunato, E..

3 recordsLinked to original sources

bioRxiv2023

Patterned Metal Grids for Flexible and Transparent Neural Microelectrode Arrays

Flexible and transparent microelectrodes can provide large-scale neural recordings with temporal and spatial resolution when used alongside functional calcium imaging. Patterned metal grids defined by direct laser writing (DWL) are a promising approach for these electrodes, as they resort to standard microfabrication processes and materials, allowing the possibility of mass production. For these reasons, a study exploring transparent grid-based electrodes using DWL for measuring electrocorticography signal was performed. Patterned metal grids with 1 m of linewidth and 22 m of spacing between lines showed a sheet resistance of 6 {Omega}/sq and a transmittance of 81% at 550 nm. The grids were transferred to a 5 m Parylene-C membrane using an optimized procedure that involves an oxygen plasma pre-treatment. This procedure ensures mechanical robustness and stability of the grids. Finally, a flexible and transparent prototype was fabricated with a microelectrode array composed by 16 electrodes with 500 m of diameter. These microelectrodes shown an impedance of 10 k{Omega} at 1 kHz in saline solution and they are highly conformal facilitating in vivo implantation and the recording of neural activity in the mouse cerebellum surface. To conclude, patterned metal grids based-electrodes exhibit a promising performance compared to transparent conductive oxides or graphene. Moreover, the introduction of DLW enables easy and fast manipulation of grid shape and dimensions without the need of physical masks, while keeping large scale compatibility, which is important for tools used in neuroscience community.

neuroscience↗

bioRxiv2020

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

This work explored hybrid films of silver nanowires (AgNWs) with indium-zinc oxide (IZO) for developing high-performance and low-cost electrocorticography (ECoG) electrodes. The transparent hybrid films achieved a sheet resistance of 6 {Omega}/sq enabling electrodes with 500 m diameter to reach an impedance of 20 k{Omega} at 1 kHz and a charge storage capacity of 3.2 mC/cm2, an improvement in properties over IZO electrodes, whose performance is on par with the classical tin doped indium oxide (ITO). Characterization of light-induced artifacts was performed showing that light intensities <14 mW/mm2 elicit minimal electrical potential variation, which falls within the magnitude 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 hybrid films did not cause distortion of light during fluorescence microscopy. This study highlighted the capabilities of the hybrid structure of AgNWs with IZO, that can be fabricated with industrially-established processes at low cost, to be used for transparent ECoG electrodes, offering a new way to record neural electrical activity on a large and fast scale with direct visualization of neurons.

neuroscience↗

bioRxiv2018

Does impedance matter when recording spikes with polytrodes?

Extracellular microelectrodes have been widely used to measure brain activity, yet there are still basic questions about the requirements for a good extracellular microelectrode. One common source of confusion is how an electrodes impedance affects the amplitude of extracellular spikes and background noise.\n\nHere we discuss how an electrodes impedance affects data quality in extracellular recordings, which is crucial for both the detection of spikes and their assignment to the correct neurons. This study employs commercial polytrodes containing 32 electrodes (177 m2) arranged in a dense array. This allowed us to directly compare, side-by-side, the same extracellular signals measured by modified low impedance (~100 kOhm) microelectrodes with unmodified high impedance (~1 MOhm) microelectrodes. We begin with an evaluation of existing protocols to lower the impedance of the electrodes. The poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT-PSS) electrodeposition protocol is a simple, stable, and reliable method for decreasing the impedance of a microelectrode up to tenfold. We next record in vivo using polytrodes that are modified in a chess board pattern, such that the signal of one neuron is detected by multiple coated and non-coated electrodes. The performance of the coated and non-coated electrodes is then compared on measures of background noise and amplitude of the detected action potentials.\n\nIf the proper recording system is used, then the impedance of a microelectrode within the range of standard polytrodes (~ 0.1 to 2 MOhm) does not significantly affect data quality and spike sorting. This study should encourage neuroscientists to stop worrying about one more unknown.

neuroscience↗