  Dr. John S. Newman, an expert and pioneer in electrochemical engineering,
studied the electrical characteristics of disk electrodes extensively since the
1960s. Newman and his colleagues published the results in a series of articles
in the Journal of the Electrochemical Society. This seminal series is
consistent and well-written, and has been cited by many in electrochemistry and
closely related fields. However, the articles, especially the later ones in the
series, enjoined less familiarity in other fields, including biomedical
engineering in which electrodes became widely used in neural stimulation. The
purpose of this review is therefore to summarize Newman's work on disk
electrodes together and provide a comprehensive understanding of the original
articles. The review mainly focuses on the behaviors of interest to neural
stimulation, namely the primary distribution, frequency dispersion, and the
current step and voltage step responses. More mathematical details are
supplemented to the original calculation to help the readers follow the
derivation more easily. Several adjustments are made to Newman's original
analyses. First, the equation sets are summarized into matrix form, which
demonstrates the underlying structure of the electrode-electrolyte system. This
formulation is helpful in showing the similarity and differences between
different inputs discussed. Also, the normalization factors to give
dimensionless variables have been slightly scaled by {\pi}/4 compared to the
original articles, which endows them the representation of physical quantities.
A consistent symbol naming system is used to refer to the results from
different articles. Finally, some preliminary analyses are presented on the
numeric accuracy of the solutions. The review will provide a comprehensive
understanding of the original articles, especially in the context of
neuroengineering applications.
