Stimulation Electrode Materials and Electrochemical Testing Methods

Part of the Biological and Medical Physics, Biomedical Engineering book series (BIOMEDICAL)


Neuro-stimulation can be implemented using several design choices — bipolar vs. monopolar stimulation, current vs. voltage control, and active vs. passive recharge. To ensure proper function through the desired lifetime, electrodes are typically made of titanium, platinum, or iridium. The difference between the 3 metals is primarily based on their performance in reversible oxidation/reduction mechanisms, which can be illustrated using various electrochemical techniques.

In slow cyclic voltammetry analysis, a platinum electrode can reversibly consume and release 3 mC/cm2 of charge within the normal operating voltage range. However, for actual neuro-stimulation pulses, platinum can only safely inject 0.1 mC/cm2, as estimated from an electrode-potential graph. Compared to platinum, iridium can inject 10 times the amount of charge for both neuro-stimulation and cyclic voltammetry. The greater capability is due to both the greater number of available oxidation states and utilization of bulk porous oxide.

In AC impedance, a titanium electrode exhibits the same double-layer capacitance per area as that of platinum. However, titanium suffers from irreversible buildup of a high-impedance oxide layer, which prevents sustained charge-injection usage. The irreversible oxidation can be observed using the pulse-clamp technique.

This chapter also introduces computer simulations, specifically capacitive computer models, as a method for visualizing the current-distribution pattern. The simulation shows uniform current distribution despite prominent electrode topologies. A dissolution study performed with gold electrodes confirms that the current distribution is uniform during normal usage, but exhibits severe current crowding when charge injection is increased above the safe limit.


Electrode Potential Charge Injection Neural Stimulation Monopolar Stimulation Cathodic Pulse 
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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.Boston Scientific Neuromodulation CorporationValenciaUSA
  2. 2.Department of Electrical EngineeringUniversity of CaliforniaLos AngelesUSA

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