Fully desktop fabricated flexible graphene electrocorticography (ECoG) arrays

Abstract

Flexible Electrocorticography (ECoG) electrode arrays that conform to the cortical surface and record surface field potentials from multiple brain regions provide unique insights into how computations occurring in distributed brain regions mediate behavior. Specialized microfabrication methods are required to produce flexible ECoG devices with high-density electrode arrays. However, these fabrication methods are challenging for scientists without access to cleanroom fabrication equipment. Here we present a fully desktop fabricated flexible graphene ECoG array. First, we synthesized a stable, conductive ink via liquid exfoliation of Graphene in Cyrene. Next, we established a stencil-printing process for patterning the graphene ink via laser-cut stencils on flexible polyimide substrates. Benchtop tests indicate that the graphene electrodes have good conductivity of ~ 1.1 × 103 S·cm-1, flexibility to maintain their electrical connection under static bending, and electrochemical stability in a 15-day accelerated corrosion test. Chronically implanted graphene ECoG devices remain fully functional for up to 180 days, with average in vivo impedances of 24.72 ± 95.23 kΩ at 1 kHz. The ECoG device can measure spontaneous surface field potentials from mice under awake and anesthetized states and sensory stimulus-evoked responses. The stencil-printing fabrication process can be used to create Graphene ECoG devices with customized electrode layouts within 24 hours using commonly available laboratory equipment.

Electrolyte engineering in organic electrochemical transistors for advanced electrophysiology

“…This empowers scientists to underpin diverse heart rhythm abnormalities [5,6] and decode intercellular and intracellular messages [7,8] , leading to the establishment of platforms for early diagnosis and treatments of cardiovascular and neurodegenerative diseases [9,10] . Most electrophysiological techniques, e.g., electrocardiograms (ECGs) [11][12][13] , electroencephalograms (EEGs) [14,15] , electrocorticography (ECoG) [16,17] , etc., capture signals by situating bioelectrodes on the tissue surface [18] . Conventional electrodes, typically termed "passive electrodes" [19] , have their own sets of challenges.…”

Carbon Nanotube-Based Printed All-Organic Microelectrode Arrays for Neural Stimulation and Recording

“…To date, numerous studies on carbon-based electrodes have emerged, including wearable electrodes for skin surface application [12], EEG recording within the ear [1], implantable electrodes for neural recording [13,14] and stimulation [15,16], facilitation of nerve regeneration [17], ECoG recording on brain surfaces [2], and electrophysiological investigation involving cultured neural cells [18,19]. Specifically, MEAs offer a high spatial resolution as well as remarkable sensitivity during neural recording and stimulation in both in vivo and in vitro environments [3], including on the brain surfaces [20][21][22][23][24][25][26] and in the brain tissue [27][28][29][30].…”

“…Various materials have been investigated for MEAs placed on the brain surface, including metal electrodes modified with organic materials for insulation [20], those utilizing organic materials to enhance electrical properties [21,22], as well as electrodes composed entirely of organic materials such as polypyrrole [23], poly (3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) [24,31,32], and graphene [25,26]. Similarly, metal MEAs intended for insertion into brain tissue have been modified with organic materials to improve insulation [27] or electrical properties [28,29], and some MEAs possess components for both surface placement and tissue insertion [30].…”

Liquid Metal-Based Electrode Array for Neural Signal Recording

“…To overcome this restriction, flexible electronics have become a prospective technology distinguished by their compliant mechanical performance, which includes the ability to withstand bending, twisting, and expansion [11][12][13][14]. One common strategy is to print or spray the conductive materials on a soft substrate such as polydimethylsiloxane (PDMS) [15], polyimide (PI) [16], or polyamide (PA) [17]. Silicon nanowires [18], carbon nanotubes [19], graphene [17,20], and Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) [21] have been used for the fabrication of brain electrodes recently.…”

“…One common strategy is to print or spray the conductive materials on a soft substrate such as polydimethylsiloxane (PDMS) [15], polyimide (PI) [16], or polyamide (PA) [17]. Silicon nanowires [18], carbon nanotubes [19], graphene [17,20], and Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) [21] have been used for the fabrication of brain electrodes recently. However, the electronic conductivity of these materials (for example, graphene is ~5.2 × 10 3 S/m, and PEDOT:PSS is ~2.8 × 10 3 S/m) is much lower than that of the metal materials (such as Pt ~9.4 × 10 6 S/m, Ag ~6.8 × 10 7 S/m, and Au ~4.3 × 10 7 S/m).…”