Medical & Biological Engineering & Computing

, Volume 50, Issue 4, pp 403–410 | Cite as

Safety of multi-channel stimulation implants: a single blocking capacitor per channel is not sufficient after single-fault failure

  • Antoine Nonclercq
  • Laurent Lonys
  • Anne Vanhoestenberghe
  • Andreas Demosthenous
  • Nick Donaldson
Original Article


One reason given for placing capacitors in series with stimulation electrodes is that they prevent direct current flow and therefore tissue damage under fault conditions. We show that this is not true for multiplexed multi-channel stimulators with one capacitor per channel. A test bench of two stimulation channels, two stimulation tripoles and a saline bath was used to measure the direct current flowing through the electrodes under two different single fault conditions. The electrodes were passively discharged between stimulation pulses. For the particular condition used (16 mA, 1 ms stimulation pulse at 20 Hz with electrodes placed 5 cm apart), the current ranged from 38 to 326 μA depending on the type of fault. The variation of the fault current with time, stimulation amplitude, stimulation frequency and distance between the electrodes is given. Possible additional methods to improve safety are discussed.


Blocking capacitor Electric stimulation Fault current Device safety Tissue damage Electrodes 



The authors thank Prof. Stéphane Godet and Benoit Haut for their help on this study.


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Copyright information

© International Federation for Medical and Biological Engineering 2012

Authors and Affiliations

  • Antoine Nonclercq
    • 1
  • Laurent Lonys
    • 1
  • Anne Vanhoestenberghe
    • 2
  • Andreas Demosthenous
    • 3
  • Nick Donaldson
    • 2
  1. 1.Biomedical Stimulation and Monitoring Research Group (BISTIMO)Université Libre de BruxellesBrusselsBelgium
  2. 2.Implanted Devices Group, Department of Medical Physics and BioengineeringLondonUK
  3. 3.Department of Electronic and Electrical EngineeringLondonUK

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