Transient electrical behavior of an electrode/electrolyte interface based on a surface micro-structured with gold mushroom shapes

Abstract

The transient electrical behavior of an electrode/electrolyte interface based on an electrode micro-structured with gold protruding mushroom shapes is measured and modeled. The application of a voltage pulse train with changing frequency generates a corresponding train of current pulses with an offset current that approaches a saturation limit exponentially. The transient behavior of the electrical current was accurately reproduced using the Nernst-Planck-Poisson model and the geometric parameters of the mushroom shape. Spatiotemporal patterns of the electric field demonstrate that the current transient is caused by a slow kinetics of charges accumulating at the gold/electrolyte interface and under the micro-mushroom cap. The accumulation of charges establishes an internal electrical potential that drives a Faradic current through the mushroom/electrolyte interface. The aim of this work is to understand how this charge dynamics in the vicinity of the three-dimensional electrode surfaces is established and how it can be minimized to prevent damage to cells and tissues under electrical stimulation.

LEGO-like Assembly of Fibrous Modules for Display Textiles

“…Figure a shows that both the current and luminance values of the devices (parallel contact mode) increased with increasing applied bias. With the pixel (contact) area of ∼9 mm 2 , the device showed current levels in the range of 5–7 mA (current density: ∼55 mA/cm 2 ) at V pp = ± 2.5 V. The current profile showed a good response to an external AC bias with a frequency f = 1 Hz, and at the rising edge of the voltage pulse, a current spike with a relaxation time of 18 ms induced by capacitive and Faradaic components was measured (Supporting Information, Figure S3). , When the voltage polarity was changed, a downward current spike also appeared, which was attributed to the displacement current with an opposite redox reaction. The maximum luminance was measured at V pp = ± 3.0 V, and by varying the applied voltage, we could tune the luminance of the light-emitting pixel as desired.…”

Gold‐Mushroom Microelectrode Arrays and the Quest for Intracellular‐Like Recordings: Perspectives and Outlooks

“…This can be further simplified by connecting a resistor in parallel with the capacitors. With the resistor, accounting for the Faradaic contribution of charge transfer between the microelectrode's surface and the electrolyte, as this is the dominant process for the charges accumulating at the mushroom cap and the interface with the electrolyte [65] and the capacitor modeling the EDL interface.…”

“…In the literature of neuronal recordings with GMμEAs, the majority of reports uses a high density configuration for the microelectrodes arrays. This implies a pitch between each GMμEs of 8-20 µm, [7,14,15,[31][32][33]43,65] with only a single paper reporting the use of larger pitchs lengths (100 µm). [59] Thus, the impact of a higher or lower density in the signal acquisition stands poorly explored.…”