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Action Potential Generator and Electrode Testing
Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, Faculty of Science & Engineering.
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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 μm 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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. , 44 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1725
National Category
Medical Engineering
Identifiers
URN: urn:nbn:se:liu:diva-121088ISBN: 978-91-7685-974-2 (print)OAI: oai:DiVA.org:liu-121088DiVA: diva2:851645
Presentation
2015-09-25, IMT 1, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
Opponent
Supervisors
Note

The Series name Linköping Studies in Science and Technology Licentiate Thesis in the thesis is incorrect. The correct series name is Linköping Studies in Science and Technology. Thesis.

Available from: 2015-09-07 Created: 2015-09-07 Last updated: 2016-05-04Bibliographically approved
List of papers
1. A Physical Action Potential Generator: Design, Implementation and Evaluation
Open this publication in new window or tab >>A Physical Action Potential Generator: Design, Implementation and Evaluation
2015 (English)In: Frontiers in Neuroscience, ISSN 1662-4548, E-ISSN 1662-453X, Vol. 9, 1-11 p., 371Article in journal (Refereed) Epub ahead of print
Abstract [en]

The objective was to develop a physical action potential generator (Paxon) with the ability to generate a stable, repeatable, programmable, and physiological-like action potential. The Paxon has an equivalent of 40 nodes of Ranvier that were mimicked using resin embedded gold wires (Ø = 20 μm). These nodes were software controlled and the action potentials were initiated by a start trigger. Clinically used Ag-AgCl electrodes were coupled to the Paxon for functional testing. The Paxon’s action potential parameters were tunable using a second order mathematical equation to generate physiologically relevant output, which was accomplished by varying the number of nodes involved (1 to 40 in incremental steps of 1) and the node drive potential (0 to 2.8V in 0.7 mV steps), while keeping a fixed inter-nodal timing and test electrode configuration. A system noise floor of 0.07 ± 0.01 μV was calculated over 50 runs. A differential test electrode recorded a peak positive amplitude of 1.5 ± 0.05 mV (gain of 40x) at time 196.4 ± 0.06 ms, including a post trigger delay. The Paxon’s programmable action potential like signal has the possibility to be used as a validation test platform for medical surface electrodes and their attached systems.

Place, publisher, year, edition, pages
Frontiers Research Foundation, 2015
Keyword
Action potential, biomedical electrode, electronic nerve model, nodes of Ranvier, ulnar nerve
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-121086 (URN)10.3389/fnins.2015.00371 (DOI)
Note

Funding agencies| Linköping University; the Swedish Research Council (Grant No. 621-2013-6078)

At the time for thesis presentation publication was in status: Manuscript

Available from: 2015-09-07 Created: 2015-09-07 Last updated: 2016-08-04Bibliographically approved
2. Characterization of a Surface Ag-AgCl Electrode using the Paxon Test Platform
Open this publication in new window or tab >>Characterization of a Surface Ag-AgCl Electrode using the Paxon Test Platform
2015 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Evaluation of an electrode for intraelectrode differences using both a traditional gain-phase method and the Paxon test platform. The direct gain-phase measurements are useful to extract the transfer function of the electrode, as well as some other base parameters. The Paxon test platform is a complementary method that tests electrodes under conditions that are more realistic than the gel-to-gel connection used in the gain-phase method. Testing stability over time e.g. DC signal drift (worst set 6,31 ± 43,00 nV) over a one hour of measurement duration was carried out. The Paxon also lets tests be performed beyond what the gain-phase methods can measure, for example electrode rotation, which would uncover variations in the symmetry of the electrode. When tested, the symmetry properties of the electrode (test set variations, start to end, over rotations 0,90,180 and 270 degrees) resulted in a peak to peak variation in detected amplitude of 5.3 ±8.9 mV. Intraelectrode variations were detected and quantized with the Paxon test platform.

Keyword
Electrode testing, Characterization, Coupling Parameters. Stability test, Axon potential
National Category
Medical Engineering
Identifiers
urn:nbn:se:liu:diva-121087 (URN)
Available from: 2015-09-07 Created: 2015-09-07 Last updated: 2016-05-04Bibliographically approved

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