Does a coupling capacitor enhance the charge balance during neural stimulation? An empirical study

Area of Science:

• Biomedical Engineering
• Electrochemistry
• Medical Device Safety

Background:

• Coupling capacitors are essential components in medical devices, preventing direct current (DC) buildup at electrode-tissue interfaces.
• Their role in mitigating charge accumulation is well-established, but a potential side effect is often overlooked.

Purpose of the Study:

• To analytically and experimentally investigate the offset voltage introduced by coupling capacitors.
• To assess the contribution of coupling capacitors to passive charge balancing.
• To determine the safety implications of capacitor-induced offset voltages.

Main Methods:

• Analytical calculations of offset voltage.
• Experimental validation using bipolar-driven platinum electrodes in a saline environment.
• Assessment of passive charge balancing capabilities.

Main Results:

• Coupling capacitors were confirmed to introduce an offset voltage at the electrode-tissue interface.
• These capacitors showed minimal contribution to passive charge balancing.
• In specific scenarios, the induced offset voltage reached levels capable of initiating irreversible electrochemical reactions.

Conclusions:

• Coupling capacitors can generate hazardous offset voltages, posing risks of electrochemical damage.
• The passive charge balancing effect of coupling capacitors is negligible.
• Thorough analysis of offset voltage under all operating conditions is recommended when using coupling capacitors to ensure safety.