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Hu J, Hossain RF, Navabi ZS, Tillery A, Laroque M, Donaldson PD, Swisher SL, Kodandaramaiah SB. Fully desktop fabricated flexible graphene electrocorticography (ECoG) arrays. J Neural Eng 2023; 20:10.1088/1741-2552/acae08. [PMID: 36548995 PMCID: PMC10027363 DOI: 10.1088/1741-2552/acae08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 12/22/2022] [Indexed: 12/24/2022]
Abstract
Objective: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.Results: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 × 103S cm-1, flexibility to maintain their electrical connection under static bending, and electrochemical stability in a 15 d accelerated corrosion test. Chronically implanted graphene ECoG devices remain fully functional for up to 180 d, with averagein vivoimpedances 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.Significance:The stencil-printing fabrication process can be used to create Graphene ECoG devices with customized electrode layouts within 24 h using commonly available laboratory equipment.
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Affiliation(s)
- Jia Hu
- Department of Mechanical Engineering, University of Minnesota Twin Cities
| | | | - Zahra S. Navabi
- Department of Mechanical Engineering, University of Minnesota Twin Cities
| | | | - Michael Laroque
- Department of Mechanical Engineering, University of Minnesota Twin Cities
| | - Preston D. Donaldson
- Department of Electrical and Computer Engineering, University of Minnesota Twin Cities
| | - Sarah L. Swisher
- Department of Electrical and Computer Engineering, University of Minnesota Twin Cities
| | - Suhasa B. Kodandaramaiah
- Department of Mechanical Engineering, University of Minnesota Twin Cities
- Department of Biomedical Engineering, University of Minnesota Twin Cities
- Department of Neuroscience, University of Minnesota Twin Cities
- Send manuscript correspondence to: Suhasa B. Kodandaramaiah, Department of Mechanical Engineering, University of Minnesota, Twin Cities, Address: 111 Church St SE, Room 303, Minneapolis, MN 55455,
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Liu X, Bibineyshvili Y, Robles DA, Boreland AJ, Margolis DJ, Shreiber DI, Zahn JD. Fabrication of a Multilayer Implantable Cortical Microelectrode Probe to Improve Recording Potential. JOURNAL OF MICROELECTROMECHANICAL SYSTEMS : A JOINT IEEE AND ASME PUBLICATION ON MICROSTRUCTURES, MICROACTUATORS, MICROSENSORS, AND MICROSYSTEMS 2021; 30:569-581. [PMID: 34539168 PMCID: PMC8445332 DOI: 10.1109/jmems.2021.3092230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Intracortical neural probes are a key enabling technology for acquiring high fidelity neural signals within the cortex. They are viewed as a crucial component of brain-computer interfaces (BCIs) in order to record electrical activities from neurons within the brain. Smaller, more flexible, polymer-based probes have been investigated for their potential to limit the acute and chronic neural tissue response. Conventional methods of patterning electrodes and connecting traces on a single supporting layer can limit the number of recording sites which can be defined, particularly when designing narrower probes. We present a novel strategy of increasing the number of recording sites without proportionally increasing the size of the probe by using a multilayer fabrication process to vertically layer recording traces on multiple Parylene support layers, allowing more recording traces to be defined on a smaller probe width. Using this approach, we are able to define 16 electrodes on 4 supporting layers (4 electrodes per layer), each with a 30 μm diameter recording window and 5 μm wide connecting trace defined by conventional LWUV lithography, on an 80 μm wide by 9 μm thick microprobe. Prior to in vitro and in vivo validation, the multilayer probes are electrically characterized via impedance spectroscopy and evaluating crosstalk between adjacent layers. Demonstration of acute in vitro recordings in a cerebral organoid model and in vivo recordings in a murine model indicate the probe's capability for single unit recordings. This work demonstrates the ability to fabricate smaller, more compliant neural probes without sacrificing electrode density.
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Affiliation(s)
- Xin Liu
- Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854 USA
| | - Yelena Bibineyshvili
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854 USA
| | - Denise A Robles
- Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854 USA
| | - Andrew J Boreland
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854 USA
| | - David J Margolis
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854 USA
| | - David I Shreiber
- Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854 USA
| | - Jeffrey D Zahn
- Department of Biomedical Engineering, Rutgers University, Piscataway, NJ 08854 USA
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Zia M, Chung B, Sober S, Bakir MS. Flexible Multielectrode Arrays With 2-D and 3-D Contacts for In Vivo Electromyography Recording. IEEE TRANSACTIONS ON COMPONENTS, PACKAGING, AND MANUFACTURING TECHNOLOGY 2020; 10:197-202. [PMID: 32280561 PMCID: PMC7150534 DOI: 10.1109/tcpmt.2019.2963556] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We present a system for recording in vivo electromyographic (EMG) signals from songbirds using hybrid polyimide-polydimethylsiloxane (PDMS) flexible multielectrode arrays (MEAs). 2-D electrodes with a diameter of 200, 125, and 50 μm and a center-to-center pitch of 300, 200, and 100 μm, respectively, were fabricated. 3-D MEAs were fabricated using a photoresist reflow process to obtain hemispherical domes utilized to form the 3-D electrodes. Biocompatibility and flexibility of the arrays were ensured by using polyimide and PDMS as the materials of choice for the arrays. EMG activity was recorded from the expiratory muscle group of anesthetized songbirds using the fabricated 2-D and 3-D arrays. Air pressure data were also recorded simultaneously from the air sac of the songbird. Together, EMG recordings and air pressure measurements can be used to characterize how the nervous system controls breathing and other motor behaviors. Such technologies can in turn provide unique insights into motor control in a range of species, including humans. An improvement of over 7× in the signal-to-noise ratio (SNR) is observed with the utilization of 3-D MEAs in comparison to 2-D MEAs.
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Affiliation(s)
- Muneeb Zia
- Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA
| | - Bryce Chung
- Department of Biology, Emory University, Atlanta, GA 30322 USA
| | - Samuel Sober
- Department of Biology, Emory University, Atlanta, GA 30322 USA
| | - Muhannad S Bakir
- Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA
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Baek C, Seo JM. Investigation of using Cyclic Olefin Copolymer as Neural Electrode. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:5129-5132. [PMID: 31947013 DOI: 10.1109/embc.2019.8857390] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cyclic olefin copolymer (COC) is a polymer that has recently been attracting attention in optics and microfluidic applications due to its high solvent resistance, biocompatibility, thermoplasticity, and optical transparency. It also has very low water absorption rate, which makes COC a very good candidate for packaging material for implantable neural prosthetic devices. In this study, we investigated the possibilities of fabricating COC into a neural electrode. We started by heat-compressing COC pellets to form films. After oxygen plasma surface treatment, a thin layer of gold was deposited. Then, a standard photolithography technique was used to pattern the gold. Finally, the paths were insulated using an extra film of COC. The validity of the fabricated electrode was confirmed by metal contact test and soak testing in PBS solution for a week.
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Baek C, Kim J, Lee Y, Seo JM. Fabrication and Evaluation of Cyclic Olefin Copolymer Based Implantable Neural Electrode. IEEE Trans Biomed Eng 2020; 67:2542-2551. [PMID: 31905131 DOI: 10.1109/tbme.2020.2963992] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE The purpose of this paper is to establish fabrication method of cyclic olefin copolymer(COC)-based neural electrode. METHODS The fabrication started with preparing COC pellets into COC films by compression molding. Metal layers were deposited on the COC film and attached to a silicon wafer. Laser ablation was used to cut the outer edges and mark alignment keys. The metal layers were patterned using standard photolithography procedures. Finally, the isolated electrodes were laminated. To ensure that the resulting electrode is safe and suitable for long-term implants, in vitro biocompatibility test, impedance evaluation, accelerated soak test, and repeated bend test were conducted. RESULTS Cytotoxicity test and elution test confirmed the biocompatibility in vitro. The basic performance was not hindered compared to other polymer-based electrodes, and the longevity of the electrode was validated by accelerated soak test. However, repeated bend test revealed that the material might not be suitable for applications where constant bending is required. CONCLUSION The COC-based neural electrode was successfully fabricated. The material showed several merits such as biocompatibility, thermoplasticity, low water absorption rate, and high transparency, but should be limited to applications where repeated bending is not required. SIGNIFICANCE Electrical circuits in implantable prosthetic devices must be hermetically encapsulated for a long period of time. Material such as COC with extremely low water absorption rate could have a significant impact on the longevity of these devices.
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Dalrymple AN, Huynh M, Robles UA, Marroquin JB, Lee CD, Petrossians A, Whalen JJ, Li D, Parkington HC, Forsythe JS, Green RA, Poole-Warren LA, Shepherd RK, Fallon JB. Electrochemical and mechanical performance of reduced graphene oxide, conductive hydrogel, and electrodeposited Pt-Ir coated electrodes: an active in vitro study. J Neural Eng 2019; 17:016015. [PMID: 31652427 DOI: 10.1088/1741-2552/ab5163] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
OBJECTIVE To systematically compare the in vitro electrochemical and mechanical properties of several electrode coatings that have been reported to increase the efficacy of medical bionics devices by increasing the amount of charge that can be delivered safely to the target neural tissue. APPROACH Smooth platinum (Pt) ring and disc electrodes were coated with reduced graphene oxide, conductive hydrogel, or electrodeposited Pt-Ir. Electrodes with coatings were compared with uncoated smooth Pt electrodes before and after an in vitro accelerated aging protocol. The various coatings were compared mechanically using the adhesion-by-tape test. Electrodes were stimulated in saline for 24 hours/day 7 days/week for 21 d at 85 °C (1.6-year equivalence) at a constant charge density of 200 µC/cm2/phase. Electrodes were graded on surface corrosion and trace analysis of Pt in the electrolyte after aging. Electrochemical measurements performed before, during, and after aging included electrochemical impedance spectroscopy, cyclic voltammetry, and charge injection limit and impedance from voltage transient recordings. MAIN RESULTS All three coatings adhered well to smooth Pt and exhibited electrochemical advantage over smooth Pt electrodes prior to aging. After aging, graphene coated electrodes displayed a stimulation-induced increase in impedance and reduction in the charge injection limit (p < 0.001), alongside extensive corrosion and release of Pt into the electrolyte. In contrast, both conductive hydrogel and Pt-Ir coated electrodes had smaller impedances and larger charge injection limits than smooth Pt electrodes (p < 0.001) following aging regardless of the stimulus level and with little evidence of corrosion or Pt dissolution. SIGNIFICANCE This study rigorously tested the mechanical and electrochemical performance of electrode coatings in vitro and provided suitable candidates for future in vivo testing.
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Lee WR, Im C, Park HY, Seo JM, Kim JM. Fabrication of Convex PDMS-Parylene Microstructures for Conformal Contact of Planar Micro-Electrode Array. Polymers (Basel) 2019; 11:polym11091436. [PMID: 31480664 PMCID: PMC6780241 DOI: 10.3390/polym11091436] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 08/23/2019] [Accepted: 08/27/2019] [Indexed: 11/16/2022] Open
Abstract
Polymer-based micro-electrode arrays (MEAs) are gaining attention as an essential technology to understand brain connectivity and function in the field of neuroscience. However, polymer based MEAs may have several challenges such as difficulty in performing the etching process, difficulty of micro-pattern generation through the photolithography process, weak metal adhesion due to low surface energy, and air pocket entrapment over the electrode site. In order to compensate for the challenges, this paper proposes a novel MEA fabrication process that is performed sequentially with (1) silicon mold preparation; (2) PDMS replica molding, and (3) metal patterning and parylene insulation. The MEA fabricated through this process possesses four arms with electrode sites on the convex microstructures protruding about 20 μm from the outermost layer surface. The validity of the convex microstructure implementation is demonstrated through theoretical background. The electrochemical impedance magnitude is 204.4 ± 68.1 kΩ at 1 kHz. The feasibility of the MEA with convex microstructures was confirmed by identifying the oscillation in the beta frequency band (13–30 Hz) in the electrocorticography signal of a rat olfactory bulb during respiration. These results suggest that the MEA with convex microstructures is promising for applying to various neural recording and stimulation studies.
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Affiliation(s)
- Woo Ram Lee
- Dental Life Science Research Institute, Seoul National University Dental Hospital, Seoul 03080, Korea
- Department of Electrical and Computer Engineering, and Institute of Engineering, Seoul National University, Seoul 08826, Korea
- Inter-university Semiconductor Research Center, Seoul National University, Seoul 08826, Korea
| | - Changkyun Im
- Dental Life Science Research Institute, Seoul National University Dental Hospital, Seoul 03080, Korea
- Inter-university Semiconductor Research Center, Seoul National University, Seoul 08826, Korea
- Dental Research Institute, Seoul National University School of Dentistry, Seoul 03080, Korea
| | - Hae-Yong Park
- Department of Physiology, College of Medicine, Hallym University, Chuncheon 24252, Korea
| | - Jong-Mo Seo
- Department of Electrical and Computer Engineering, and Institute of Engineering, Seoul National University, Seoul 08826, Korea
- Inter-university Semiconductor Research Center, Seoul National University, Seoul 08826, Korea
| | - Jun-Min Kim
- Dental Life Science Research Institute, Seoul National University Dental Hospital, Seoul 03080, Korea.
- Inter-university Semiconductor Research Center, Seoul National University, Seoul 08826, Korea.
- Department of Electronic Communication Engineering, Gyeonggi University of Science Technology, Siheung 15073, Korea.
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