Electrode impedance analysis of chronic tungsten microwire neural implants: Understanding abiotic vs. biotic contributions

Viswanath Sankar, Erin Patrick Robert Dieme, Justin C. Sanchez, Abhishek Prasad, Toshikazu Nishida

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Changes in biotic and abiotic factors can be reflected in the complex impedance spectrum of the microelectrodes chronically implanted into the neural tissue. The recording surface of the tungsten electrode in vivo undergoes abiotic changes due to recording site corrosion and insulation delamination as well as biotic changes due to tissue encapsulation as a result of the foreign body immune response. We reported earlier that large changes in electrode impedance measured at 1 kHz were correlated with poor electrode functional performance, quantified through electrophysiological recordings during the chronic lifetime of the electrode. There is a need to identity the factors that contribute to the chronic impedance variation. In this work, we use numerical simulation and regression to equivalent circuit models to evaluate both the abiotic and biotic contributions to the impedance response over chronic implant duration. COMSOL® simulation of abiotic electrode morphology changes provide a possible explanation for the decrease in the electrode impedance at long implant duration while biotic changes play an important role in the large increase in impedance observed initially.

Original languageEnglish (US)
Article number13
JournalFrontiers in Neuroengineering
Issue numberMAY
StatePublished - May 8 2014


  • Chronic neural implants
  • Corrosion
  • Electrode impedance
  • Finite element modeling
  • Insulation delamination

ASJC Scopus subject areas

  • Biomedical Engineering
  • Biophysics
  • Neuroscience (miscellaneous)


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