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Published May 15, 2025 | Version Published
Journal Article Open

Quantifying physical degradation alongside recording and stimulation performance of 980 intracortical microelectrodes chronically implanted in three humans for 956-2130 days

Creators

  • 1. ROR icon California Institute of Technology
  • 2. ROR icon University of Southern California
  • 3. ROR icon Johns Hopkins University
  • 4. ROR icon University of Utah
  • 5. ROR icon Newcastle University
  • 6. ROR icon Los Angeles Medical Center
  • 7. ROR icon Johns Hopkins University Applied Physics Laboratory
  • 8. ROR icon Case Western Reserve University
  • 9. ROR icon Rehabilitation Institute of Chicago
  • 10. ROR icon University of Colorado Hospital
  • 11. ROR icon The University of Texas Southwestern Medical Center
  • 12. ROR icon Rancho Los Amigos National Rehabilitation Center
  • 13. ROR icon West Virginia University

Abstract

The clinical success of brain computer interfaces (BCI) depends on overcoming both biological and material challenges to ensure a long-term stable connection for neural recording and stimulation. This study systematically quantified damage that microelectrodes sustained during chronical implantation in three people with tetraplegia for 956–2130 days. Using scanning electron microscopy (SEM), we imaged 980 microelectrodes from eleven Neuroport arrays tipped with platinum (Pt, n = 8) and sputtered iridium oxide film (SIROF, n = 3). Arrays were implanted/explanted from posterior parietal, motor and somatosensory cortices across three clinical sites (Caltech/UCLA, Caltech/USC, APL/Johns Hopkins). From the electron micrographs, we quantified and correlated physical damage with functional outcomes measured in vivo, prior to explant (recording quality, noise, impedance and stimulation ability).
 
Despite greater physical degradation, SIROF electrodes were twice as likely to record neural activity than Pt (measured by SNR). For SIROF, 1 kHz impedance significantly correlated with all physical damage metrics, recording metrics, and stimulation performance, suggesting a reliable measurement of in vivo degradation. We observed a new degradation type, primarily on stimulated electrodes (“pockmarked” vs “cracked”) electrodes; however, no significant degradation due to stimulation or amount of charge delivered. We hypothesize erosion of the silicon shank accelerates damage to the electrode / tissue interface, following damage to the tip metal.
 
These findings link quantitative measurements to the microelectrodes’ physical condition and their capacity to record/stimulate. These data could lead to improved manufacturing processes or novel electrode designs to improve long-term performance of BCIs, making them vitally important as multi-year clinical trials of BCIs are becoming more common.
 

Statement of significance:

Long-term performance stability of the electrode-tissue interface is essential for clinical viability of brain computer interface (BCI) devices; currently, materials degradation is a critical component for performance loss. Across three human participants, ten micro-electrode arrays (plus one control) were implanted for 956–2130 days. Using scanning electron microscopy (SEM), we analyzed degradation of 980 electrodes, comparing two types of commonly implanted electrode tip metals: Platinum (Pt) and Sputtered Iridium Oxide Film (SIROF). We correlated observed degradation with in vivo electrode performance: recording (signal-to-noise ratio, noise, impedance) and stimulation (evoked somatosensory percepts). We hypothesize penetration of the electrode tip by biotic processes leads to erosion of the supporting silicon core, which then accelerates further tip metal damage. These data could lead to improved manufacturing processes or novel electrode designs towards the goal of a stable BCI electrical interface, spanning a multi-decade participant lifetime.

Copyright and License

© 2025 The Authors. Published by Elsevier Inc. on behalf of Acta Materialia Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Acknowledgement

The authors would like to thank all the participants for their efforts and engagement in the clinical study. We also thank the clinical staff at Rancho Los Amigos, Casa Colina, USC, UCLA and JHH their work and dedication during the experimental sessions. We would also like thank the staff at the University of Utah and Caltech Imaging Centers for their expertise and assistance imaging the arrays. Big thanks to BSS, JBV, BMG, KK and AS for their assistance scoring the SEM images. This work was developed with variety of funding support for salary, resources, patient care costs, and specialized equipment; including internal research support from the Johns Hopkins University Applied Physics Laboratory (JHU/APL) and funding from the Defense Advanced Research Projects Agency (DARPA) under awards HR001120C0120, N66001–10-C-4056 and N66001–15-C-4017. The views, opinions and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.

Funding

This work was developed with variety of funding support for salary, resources, patient care costs, and specialized equipment; including internal research support from the Johns Hopkins University Applied Physics Laboratory (JHU/APL) and funding from the Defense Advanced Research Projects Agency (DARPA) under awards HR001120C0120, N66001–10-C-4056 and N66001–15-C-4017.

David Bjånes: Craig H. Neilson Foundation
Richard Andersen: Tianqiao and Chrissy Chen Brain-machine Interface Center
Boswell Foundation
NIH/NINDS Grant U01NS098975
NIH/NINDS Grant U01NS123127
NIH/NEI R01EY015545
NIH/NEI UG1EY032039
DARPA N66001–10-C-4056
Loren Rieth: DARPA/BTO HAPTIX: N66001–15-C-4017
NIH/NEI: 1UG3NS107688
Francesco Tenore: DARPA HR001120C0120
DARPA N66001–10-C-4056

Contributions

David A. Bjånes: Conceptualization, SEM Data Collection, End of Study Data Collection, Investigation, Funding acquisition, Formal analysis, Writing – Original Draft, Writing – Review & Editing. Spencer Kellis: Conceptualization, SEM Data Collection, End of Study Data Collection, Investigation, Formal analysis, Writing – Review & Editing. Robert Nickl: End of Study Data Collection. Brian Baker: SEM Data Collection, Resources. Tyson Aflalo: End of Study Data Collection. Luke Bashford: End of Study Data Collection. Srinivas Chivukula: End of Study Data Collection. Matthew S. Fifer: End of Study Data Collection. Luke E. Osborn: End of Study Data Collection. Breanne Christie: End of Study Data Collection, Writing – Review & Editing. Brock A. Wester: End of Study Data Collection. Pablo A. Celnik: End of Study Data Collection. Daniel Kramer: End of Study Data Collection. Kelsie Pejsa: Resources. Nathan E. Crone: Clinical. William S. Anderson: Clinical. Nadar Pouratian: Clinical. Brian Lee: Clinical. Charles Y. Liu: Clinical, Funding acquisition. Francesco V. Tenore: Conceptualization, Resources, Funding acquisition, Writing – Review & Editing. Loren Rieth: Conceptualization, SEM Data Collection, Investigation, Resources, Funding acquisition, Writing – Review & Editing. Richard A. Andersen: Conceptualization, Resources, Funding acquisition, Writing – Review & Editing.

Data Availability

The data analyzed in this paper will be available upon request.

Conflict of Interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Richard Andersen reports financial support was provided by National Institutes of Health.
Richard Andersen reports financial support was provided by Defense Advanced Research Projects Agency.
Richard Andersen reports financial support was provided by Tianqiao and Chrissy Chen Brain-machine Interface Center.
Richard Andersen reports a relationship with Blackrock Neurotech that includes: funding grants unrelated to this project.
Francesco Tenore reports financial support was provided by Defense Advanced Research Projects Agency.
David Bjanes reports financial support was provided by Craig H Neilsen Foundation.
Richard Andersen reports financial support was provided by James G Boswell Foundation.
Loren Rieth reports financial support was provided by Defense Advanced Research Projects Agency.
Loren Rieth reports financial support was provided by National Institutes of Health.
Nader Pouratian reports a relationship with Boston Scientific and Abbott Laboratories that includes: consulting or advisory.
Spencer Kellis reports a relationship with Blackrock Neurotech that includes: employment.
Loren Rieth reports a relationship with Blackrock Neurotech that includes: funding grants.
If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Additional details

Additional titles

Alternative title
Quantifying physical degradation alongside recording and stimulation performance of 980 intracortical microelectrodes chronically implanted in three humans for 956-2246 days

Identifiers

PMID
40037510
PMCID
PMC12282554

Related works

Describes
Journal Article: 40037510 (PMID)
Journal Article: PMC12282554 (PMCID)
Is new version of
Discussion Paper: 10.1101/2024.09.09.24313281 (DOI)

Funding

Johns Hopkins University Applied Physics Laboratory
Defense Advanced Research Projects Agency
HR001120C0120
Defense Advanced Research Projects Agency
N66001-10-C-4056
Defense Advanced Research Projects Agency
N66001-15-C-4017
Craig H Neilsen Foundation
California Institute of Technology Tianqiao and Chrissy Chen Institute for Neuroscience
James G Boswell Foundation
National Institute of Neurological Disorders and Stroke
U01NS098975
National Institute of Neurological Disorders and Stroke
U01NS123127
National Eye Institute
R01EY015545
National Eye Institute
UG1EY032039
National Eye Institute
1UG3NS107688

Dates

Submitted
2024-09-27
Updated
2025-02-07
Accepted
2025-02-11
Available
2025-03-02
Available online

Caltech Custom Metadata

Caltech groups
Tianqiao and Chrissy Chen Institute for Neuroscience , Division of Biology and Biological Engineering (BBE)
Publication Status
Published