Action Potential Generator and Electrode Testing

Abstract: Design, validation and application of a test platform for electrode characterization and comparison is a problem today. Development of target specific electrodes is increasing, for example surface cloth electrodes, non-contact electrodes, and deep brain stimulation electrodes. Whenever these new designs are implemented, there is always a need for testing. How these tests should be performed to verify the function of the electrode in an environment like the one they are designed for is still not solved.In this thesis, a physical axon, the Paxon, is suggested as a possibility to overcome this issue. The intent of the Paxon was to generate an electric field that is similar to the external field created by a live axonal process when an action potential is propagating along its length, and to do this in a stable, repeatable manner. In order to meet these specifications, the Paxon was designed with a microcontroller to drive the sequence of events and control the output parameters. A chamber with gold wire nodes entering through the bottom was manufactured as a dimensional mimic to a myelinated 20 ?m diameter nerve axon segment. The chamber was flooded with normal saline solution mimicking the intervening tissues and to allow ionic coupling of electrodes to the electrical field produced in the chamber.The initial validation tests demonstrated that the timing is stable (196.4 ± 0.06 ms between trigger to action potential), as is the output “detected” amplitude (1.5 ± 0.05 mV with a gain of 40).Once the Paxon test platform was verified as functional for its intended application of testing electrodes for comparison, it was then used to compare a set of six electrodes (used as a set of three differential pairs) from a single manufacturer lot and batch number.With this approach, better assessment of the stability of the  manufactured electrode, as well as longer term stability, can be attained. As more electrodes of similar and differing types are tested, the data can be used for inter-electrode comparisons and eventually verification of newelectrode designed.