Electrochemical Properties of Sputtered Ruthenium Oxide Neural Stimulation and Recording Electrodes
Round 1
Reviewer 1 Report
The manuscript by B. Chakraborty studies the electrochemical properties of sputtered RuOx for Neural stimulation and recording. The main claim of the author is the sputtered RuOx film was found to be almost equally impeding in its oxidized and reduced state at 0.6 V and -0.6 V respectively, indicating the ease of stimulation by either cathodal or anodal currents for monophasic current stimulation protocols. The manuscript is well-written, and comprehensive and would be of broad interest to many Electrochem readers. The manuscript can be published after addressing the specific comments listed below:
Pg 2, ln53, author should consider adding a brief description of why they chose RuOx for their study
Pg 3, ln105, author may wish to clarify what is the thickness of the sputtered RuOx film. And is there an effect on electrochemical properties at different film thx
Pg 7, ln237, author should correct the discrepancy between Eq (1) and the text for the coefficient of the constant phase element
Pg7, ln246, the author should correct the discrepancy between the text and the figure. As such Fig. 5a shows the bode plot for PBS, model-ISF, and the model fit. Fig. 5b is the phase angle plot as a function of frequency so this must be changed in the text. Further, the authors should comment on why the model fit is not agreeing with measured results at low frequencies 10-1 to 10. What physicochemical process is not captured in the model at low frequencies?
Fig. 5a and c visually the model fit and measured data points look essentially identical I am not sure how the X2 is different for these two figures. It would be good to include some discussion around this area
Pg 8, ln260, author should correct the typo in the title Componenets to “Components”
Pg 8, ln266, author should consider using consistent abbreviation “model-ISF” instead of mISF
Pg 10, ln328 and 329, author should clarify what the abbreviation stands for.
Pg 12, ln 428, author should consider changing the potential from -0.5-0.5 V vs. Ag | AgCl to -0.5 to 0.5V vs. Ag | AgCl
Pg 12, ln 435, author should consider adding a reference for the cost of Ru vs. Iridium targets. The author should comment on why those chose sputter deposition for RuOx deposition, would it be more economical to deposit via electrodeposition? If not, what are the shortcomings of the electrodeposition approach?
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper presents an interesting study on the electrochemical properties of sputtered ruthenium oxide (RuOx) electrode coatings for use in neural stimulation and recording. The authors have conducted a thorough investigation of the charge-injection mechanism, contribution of different circuit components, reversibility of charge-injection, and impedance states during electrochemical stimulation of the RuOx film. The results show that the sputtered RuOx film is almost equally impeding in both its oxidized and reduced states, allowing reversibility during charge-injection. The paper is well-written and provides valuable insights into the potential use of sputtered RuOx as a candidate for neural stimulation and recording electrodes.
While this authors have conducted a comprehensive study of the electrochemical behavior of sputtered ruthenium oxide (RuOx) electrode coatings, some aspects of their work may raise questions for the readers. For example, the long-term stability of the RuOx film under repeated stimulation and recording conditions and the effects of different sputtering parameters on the electrochemical properties of the RuOx film. These additional studies could provide valuable insights into the potential use of sputtered RuOx as a candidate for neural stimulation and recording electrodes.
Furthermore, a suggestion to enhance the quality of the introduction section is to provide more rationality for choosing Ruthenium oxide as the material for the study. The authors should explain why ruthenium oxide is suitable for the research problem and how it compares to other materials in terms of properties and performance.
Finally, the authors found that “A decrease by ~5% of Cdl is observed at the -0.6 V potential. This is indicative of a higher electronic contribution towards double-layer capacitance as sociated with the completely oxidized state of the film at 0.6 V”, and have not elaborated on the underlying causes and implications of this phenomenon. The authors could offer more insights to support their finding.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
The author presented the electrochemical characterization of the ruthenium oxide electrodes, which were designed to be used for neural stimulation and recording. CV, EIS, et al. several electrochemical methods were applied to help analyze the electrochemical properties of the ruthenium oxide electrodes, with the conclusion that the faradic reaction is the major charge-injection contributor. However, almost most of the content has already been published. Moreover, the manuscript does not cover neural stimulation and recording at all.
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 3 Report
The authors did a good job of revising the manuscript responding to reviewers’ comments. However, 1) the method, water vapor plasma-assisted sputtering coating of RuOx, was published in “Atmaramani, R., et, al.. (2020).”, the electrochemical analysis (CV,EIS) utilizing the model-ISF, was published in “Chakraborty, B., et, al.. (2022)” and “Chakraborty, B., et, al.. (2021)”. Circuit component analysis in charge injection somehow can be considered new compared to the published material, but still, I do not think its novelty is good enough to make this manuscript be published as a separate new journal paper.
