Safe direct current stimulation to expand capabilities of neural prostheses

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


While effective in treating some neurological disorders, neuroelectric prostheses are fundamentally limited because they must employ charge-balanced stimuli to avoid evolution of irreversible electrochemical reactions and their byproducts at the interface between metal electrodes and body fluids. Charge-balancing is typically achieved by using brief biphasic alternating current (AC) pulses, which typically excite nearby neural tissues but cannot efficiently inhibit them. In contrast, direct current (DC) applied via a metal electrode in contact with body fluids can excite, inhibit and modulate sensitivity of neurons; however, chronic DC stimulation is incompatible with biology because it violates charge injection limits that have long been considered unavoidable. In this paper, we describe the design and fabrication of a Safe DC Stimulator (SDCS) that overcomes this constraint. The SCDS drives DC ionic current into target tissue via salt-bridge micropipette electrodes by switching valves in phase with AC square waves applied to metal electrodes contained within the device. This approach achieves DC ionic flow through tissue while still adhering to charge-balancing constraints at each electrode-saline interface. We show the SDCS's ability to both inhibit and excite neural activity to achieve improved dynamic range during prosthetic stimulation of the vestibular part of the inner ear in chinchillas.

Original languageEnglish (US)
Article number6472080
Pages (from-to)319-328
Number of pages10
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number2
StatePublished - 2013


  • Balance
  • bilateral vestibular deficiency
  • direct current (dc)
  • implant
  • nerve block
  • neural inhibition
  • neural modulation
  • neural stimulation
  • safe direct current (SDC)
  • vestibular prosthesis

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biomedical Engineering
  • Computer Science Applications


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