Design and Control-Oriented Simulation of a Superelastic Nitinol Steerable Microcatheter Tip for Ischemic Stroke Thrombectomy
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsMy reviewer comments are below;
- The abstract contains excessive methodological and numerical detail (e.g., controller metrics, R², force values), making it dense and difficult to follow. It should be significantly shortened and focused on problem, method and important results etc.
- Introduction and literature review are excessively long and also poorly structured. Pages 1–4, leading to redundancy and lack of focus. This structure resembles a thesis format rather than a journal article. The sections should be merged and reduced, with a sharper emphasis on identifying the research gap. The authors could benefit from the previous works to improve the manuscript flow and scientific rigors of the manuscript. For example, Fused deposition modeling and characterization of heat shape memory poly (lactic) acid-based porous vascular scaffold, Design and Development of Shape Memory Polymer-Based Mechanical Thrombectomy Device, Mechanical analysis and biodegradation of oxides-based magneto-responsive shape memory polymers for material extrusion 3D printing of biomedical scaffolds
- The authors claimed their novelty, “integration of material characterization with control-oriented simulation” is not sufficiently convincing. Similar coupled modelling–control frameworks already exist in catheter robotics and SMA-based systems. The manuscript lacks clear differentiation from prior work, and no strong comparative analysis with state-of-the-art systems is at the end. There is no quantitative benchmarking against existing catheter systems, controllers, or simulation frameworks. For example, performance metrics (rise time, force limits, tracking error) are presented without comparison to previous works, which weakens the novelty.
- In Figure 1 (page 5), the polarization curve appears very generic with no reference. It is unclear whether it is experimental or adapted. In Figure 2 and Figure 4 (pages 6 & 9), these appear schematic/illustrative and may be AI-generated or adapted, but no source or design explanation is provided. Proper attribution or clarification is required. Similar concern applies to Figure 4, which looks like a conceptual illustration rather than a validated engineering design.
- Material properties are not clearly defined, e.g., elastic modulus values, transformation temperatures, constitutive model for Nitinol?
- The rationale for selecting Nitinol is generic, no comparison with alternative materials (e.g., polymers, composites) is provided.
- The factor of safety is not defined, despite claims of vessel safety. Simply comparing force to a threshold (0.2 N) is insufficient without structural safety margins.
- Modeling and equations lack rigor and validation depth. Some equations (e.g., Eq. 2 on page 7) appear incorrect or dimensionally inconsistent (κ = EI / (F·d) is not standard beam theory form).
- The electromechanical model is overly simplified and lacks validation against real actuator dynamics. The simulation is not validated experimentally at the system level (only material-level validation is provided).
- The conclusion (page 15) is largely descriptive and repeats general statements. It does not clearly summarize key numerical achievements (e.g., % improvement, comparison benchmarks, control advantages), reducing its impact.
- Language and grammar issues throughout. There are frequent grammatical and technical writing issues, such as, incorrect phrasing (“Abstract scanned electron microscopy” on page 4). Repetition sentences, and inconsistent technical terminology are present. The manuscript requires major language editing by a expert.
Language must be improved.
Author Response
Response to Reviewer 1
Comment 1:
The abstract contains excessive methodological and numerical detail…
Response:
Thank you for this valuable suggestion. The abstract has been completely rewritten to improve clarity and readability. Excessive numerical details and controller-specific metrics have been removed, and the abstract now focuses on the problem, methodology, key contributions, and overall impact.
Comment 2:
Introduction and literature review are excessively long…
Response:
We agree with the reviewer. The Introduction and Literature Review sections have been merged into a single concise section titled “Introduction and Literature Review.” Redundant content has been removed, and the section has been restructured to clearly highlight the research gap and motivation.
Comment 3:
Novelty is not sufficiently convincing…
Response:
This concern has been addressed by adding a dedicated subsection titled “Contribution and Novelty.” We clarified how this work differs from prior studies by emphasizing the direct integration of experimentally derived material behavior into a control-oriented simulation framework. Additionally, qualitative comparisons with existing systems have been included.
Comment 4:
Figures lack source/clarification…
Response:
All figures have been clarified:
Figure 1 represents experimentally obtained polarization data from the electrochemical corrosion tests conducted in this study.
Figures 2 and 4 are schematic representations developed by the authors to illustrate the experimental setup and conceptual catheter design, respectively.
SO:
- Figure 1 is now explicitly identified as experimental data obtained in this study.
- Figures 2 and 4 are clarified as author-generated schematic diagrams.
- Explanatory text has been added in the methodology section.
Comment 5:
Material properties are not clearly defined…
Response:
A new subsection titled “Material Properties and Constitutive Modeling” has been added. Key parameters such as elastic moduli, transformation stress, and strain limits are now clearly defined and incorporated into the modeling framework.
Comment 6:
Rationale for selecting Nitinol is generic…
Response:
A new subsection titled “Material Selection Rationale” has been introduced. This section provides a comparative discussion between Nitinol and alternative materials (e.g., polymers and composites), justifying its selection.
Comment 7:
Factor of safety is not defined…
Response:
A factor of safety (FoS) analysis has been introduced in the vessel safety section. The FoS is explicitly calculated and demonstrates that the system operates within a safe margin (>1.5) under all conditions.
Comment 8:
Equations lack rigor…
Response:
The relevant equation has been corrected and reformulated based on standard beam theory. The updated formulation is now dimensionally consistent and clearly derived.
Comment 9:
Modeling lacks validation depth…
Response:
A new subsection titled “Translational Validation and Experimental Feasibility” has been added. It clarifies current limitations and outlines future work, including hardware-in-the-loop and experimental validation.
Comment 10:
Conclusion is descriptive…
Response:
The conclusion has been fully rewritten to include clear quantitative results, performance metrics, and the broader impact of the study.
Comment 11:
Language and grammar issues…
Response:
The manuscript has undergone comprehensive language editing. Grammatical errors, redundancy, and inconsistencies have been corrected throughout.
Final Statement
We believe that these revisions have significantly strengthened the manuscript by improving its clarity, rigor, and practical relevance. We sincerely appreciate the reviewers’ constructive feedback, which has greatly enhanced the quality of this work.
We hope the revised manuscript meets the expectations for publication.
Sincerely,
The Authors
Reviewer 2 Report
Comments and Suggestions for AuthorsThis manuscript should be taken care of before publication. The major concerns are as follows:
1. Why are figures (e.g., experimental setup and catheter schematic on pages 6 and 9) not accompanied by sufficient quantitative explanation or parameter details?
2. Why does the manuscript rely heavily on descriptive discussion rather than rigorous quantitative analysis and uncertainty estimation?
3. Why does the manuscript rely heavily on descriptive discussion rather than rigorous quantitative analysis and uncertainty estimation?
4. Why is a classical cascade PI controller used instead of more advanced control strategies (e.g., MPC, adaptive control) given the nonlinear and time-varying nature of the system?
5. Some articles have significance regarding this: (a) Das, Poushali, et al. "Naturally derived carbon dots in situ confined self-healing and breathable hydrogel monolith for anomalous diffusion-driven phytomedicine release." ACS Applied Bio Materials 5.12 (2022): 5617-5633. (b) Ma, Xuesong, et al. "A water-soluble, long-wavelength fluorescent-emitting CDs with antibacterial properties derived from the Chinese herbal medicine emodin." Microchemical Journal (2026): 117786.
Author Response
Response to Reviewer 2
Comment 1:
Figures lack quantitative explanation…
Response:
A new subsection titled “Quantitative Parameters and Figure Clarification” has been added. All relevant parameters for Figures 2 and 4 are now explicitly listed to ensure reproducibility.
Comments 2 & 3:
Lack of quantitative analysis and uncertainty estimation…
Response:
We have added:
- A dedicated “Uncertainty and Statistical Analysis” subsection
- Reporting of mean ± standard deviation
- Coefficient of variation (CV)
- Measurement uncertainty propagation
Additionally, quantitative discussion has been strengthened in the Results section.
Comment 4:
Why use PI controller instead of advanced methods?
Response:
A new subsection titled “Justification for Control Strategy Selection” has been added. It explains the choice of PI control in terms of real-time feasibility, robustness, and clinical applicability, while also outlining future work using advanced control methods (e.g., MPC).
Comment 5:
Suggested references…
Response:
The recommended references have been incorporated into the literature review, with discussion linking them to broader trends in smart biomaterials and biomedical systems.
Final Statement
We believe that these revisions have significantly strengthened the manuscript by improving its clarity, rigor, and practical relevance. We sincerely appreciate the reviewers’ constructive feedback, which has greatly enhanced the quality of this work.
We hope the revised manuscript meets the expectations for publication.
Sincerely,
The Authors
Reviewer 3 Report
Comments and Suggestions for AuthorsThis manuscript presents a combined experimental–computational framework for a superelastic Nitinol-based steerable microcatheter, integrating material characterization with control-oriented simulation to improve thrombectomy navigation and safety. The authors demonstrate promising in silico performance, including accurate curvature tracking, low wall-contact forces (<0.12 N), and strong model–experiment agreement (R² ≈ 0.98), suggesting feasibility for safe endovascular steering. However, despite the technical integration, the study remains largely simulation-driven with limited translational validation.A key conceptual inconsistency lies in the statement that vessel safety is ensured because simulated wall forces remain below a “clinical threshold of 0.2 N,” despite no justification, citation consistency, or patient-specific variability analysis for this threshold; moreover, translating such a fixed limit directly from simulation to clinical safety is not physiologically robust or universally valid. Suggestions for improvement: 1) add translational validation: include at least in vitro testing in vascular phantoms with pulsatile flow or bench-top navigation experiments to substantiate simulation claims. 2)explicitly derive key equations, justify parameter choices, and include sensitivity analyses (e.g., vessel stiffness, friction, anatomical variability)., 3) streamline sections (especially Results/Discussion), remove redundancy, 4) provide a clearer comparison table versus existing steerable/robotic catheter systems. Overall, the study has potential but currently reads as a strong engineering simulation paper.
Author Response
Response to Reviewer 3
General Comment:
The study is largely simulation-driven with limited translational validation…
Response:
We acknowledge this important point. A new subsection titled “Translational Validation and Experimental Feasibility” has been added. It outlines planned in vitro validation using vascular phantoms and pulsatile flow systems, bridging simulation and clinical application.
Comment on Safety Threshold (0.2 N):
Response:
We clarified that the 0.2 N value is a reference from literature, not a universal limit. A discussion has been added emphasizing patient-specific variability and supported by the introduction of a factor of safety framework.
Comment on Equations and Parameters:
Response:
Equations have been corrected and clarified, and parameter definitions have been expanded. Additional explanation has been added to improve transparency.
Comment on Sensitivity Analysis:
Response:
A new explaining “Sensitivity Analysis” has been added. It evaluates the influence of vessel stiffness, friction, and actuation force, demonstrating system robustness.
Comment on Redundancy:
Response:
The Results and Discussion sections have been streamlined, and repetitive statements have been removed to improve clarity and readability.
Comment on Comparison with Existing Systems:
Response:
A new comparison table has been added, benchmarking the proposed system against conventional and robotic catheter systems in terms of performance, safety, and integration.
Final Statement
We believe that these revisions have significantly strengthened the manuscript by improving its clarity, rigor, and practical relevance. We sincerely appreciate the reviewers’ constructive feedback, which has greatly enhanced the quality of this work.
We hope the revised manuscript meets the expectations for publication.
Sincerely,
The Authors
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThis can be published in its present form.
Reviewer 3 Report
Comments and Suggestions for AuthorsSufficient response
