The noise and impedance of microelectrodes

Abstract

Objective. While the positive correlation between impedance and noise of microelectrodes is well known, their quantitative relationship is too rarely described. Knowledge of this relationship provides useful information for both microsystems engineers and electrophysiologists. Approach. We discuss the physical basis of noise in recordings with microelectrodes, and compare measurements of impedance spectra to noise of microelectrodes. Main results. Microelectrode recordings intrinsically include thermal noise, v t = 4 k B T ∫ Re ( Z ) d f 1 / 2 , with the real component of impedance integrated over the recording frequency band. Impedance spectroscopy allows the quantitative prediction of thermal noise. Optimization of microelectrode noise should also consider the contribution of amplifier noise. These measures enable a quantitative evaluation of microelectrodes’ recording quality which is more informative than common but limited comparisons based on the impedance magnitude at 1 kHz. Significance. Improved understanding of the origin of microelectrode noise will support efforts to produce smaller yet low noise microelectrodes, capable of recording from higher numbers of neurons. This tutorial is relevant for single microelectrodes, tetrodes, neural probes and microelectrode arrays, whether used in vitro or in vivo.

Polymer Skulls With Integrated Transparent Electrode Arrays for Cortex‐Wide Opto‐Electrophysiological Recordings

“…This series resistance could be reduced by making the PEDOT:PSS interconnects thicker or wider; however, this would reduce device transparency, and a channel series resistance of ≈20 kΩ is sufficient for recording ECoG signals with minimal thermal noise. [ 38 ] Thus, the elevated sheet resistance of these channels was determined to be an acceptable tradeoff to optimize transparency. Higher impedances at low frequencies are typical of electrode–electrolyte interfaces, [ 39 ] and the impedance approaches 200 kΩ at 1 Hz for our PEDOT:PSS microelectrodes.…”

Microelectrode Arrays for Simultaneous Electrophysiology and Advanced Optical Microscopy

“…The adoption of microelectrode array (MEA) technology in electrophysiology has played a pivotal role in supporting the study resistance in an electrolyte also reduces thermal noise, a major source of noise in electrical recordings. [13] As a result, PE-DOT:PSS electrodes lead to recordings with high signal-to-noise ratio (SNR) and to effective neural stimulation [6,9,14] while being biocompatible and promoting neuron attachment and growth. [15] In addition to electrophysiology, optical microscopy is an indispensable tool for neuroscience research due to its high spatial resolution and ability to target biomarkers selectively.…”

“…Their lower equivalent resistance in an electrolyte also reduces thermal noise, a major source of noise in electrical recordings. [ 13 ] As a result, PEDOT:PSS electrodes lead to recordings with high signal‐to‐noise ratio (SNR) and to effective neural stimulation [ 6,9,14 ] while being biocompatible and promoting neuron attachment and growth. [ 15 ]…”

A mesh microelectrode array for non-invasive electrophysiology within neural organoids

“…Each well can support a single organoid on a central spider-web-like mesh with a diameter of 2 mm and 61 microelectrodes. The 30-μm-diameter TiN microelectrodes enable low noise recordings 22 (2-3 μV rms ) and are suitable for electrical stimulation. 23 Each mesh has four concentric ring filaments (radii of 0.25, 0.5, 0.75 and 1 mm) containing 8, 12, 16 and 24 electrodes, and one electrode at the center of the mesh.…”