How 3D Printing Technology Makes Cities Smarter: A Review, Thematic Analysis, and Perspectives
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe author has put in a lot of effort to read and represent the 3D-printing work in smart cities and for that he should be lauded. The paper has categorised the literature and summarised the work in the areasHowever, at the same time, I cannot recommend the paper for publication yet. I believe that the author needs to take another step to synthesize real insights from the hard work that they conducted.
I believe the following action points could help to make the contribution more clear and useful to other readers:
1. The first table is unwielding. Rather than spanning 5 pages, the table should be at most 1 page in landscape. The titles matter not but what is more important is what we learn from the paper. The table should have categories as columns the main take-aways (aka section titles in this DTs, AI/ML, Industry 4.0, Manufacturing, Monitoring, Repair) and as rows the papers but just as year and source. We don't need to know the journal, field, and title as a colum. Instead, the paper rows can be grouped by field. The table then uses check marks to indicate which areas these papers cover. That way we get a better sense of what is happening.
2. The author presents a framework but does not explain it. The framework is essentially in the titles of the sections which is unfortunate. Instead of jumping right into these sections, the author should take the time to synthesize table 1 (improved with the 1. point) to explain these keywords their interconnection and their importance for 3D-printing in Smart cities (and create a figure that encompasses all those titles).
3. The author present the digital twins after the building in Figure 4. Argubly, digital twins are especially useful to already have them active in the building process. The figure needs more thinking how to represent the actual use of digital twins. Figures 5-7 are adaptations instead of original designs. I would encourage the author to not only adapt but the reframe these figures in the context of the proposed framework. For instance, don't present the plantoid robot but explain how 3D-printed robots can improve smart cities. Figure 5 is too Industry 4.0 centred. Adapt it more clearly to smart cities. Figure 7 looks like a specific WAAM implementation - please make the figure more generic and open it up for interaction with the other aspects of the framework.
4. The conclusion is unfornuately the weakest point of the paper. Instead of giving a quick rundown of the framework and the main take-aways, the process of the review is reiterated without any additional insights. This is where the framework should be briefly highlighted again, explain why "academics, practitioners, and policy-makers" should care and how they can apply this framework in their own work.
This list may seem a bit discouraging but I really think that the starting point of this review is valuable and important to publish. However, I believe that in its current version it is falling short of its potential. I encourage the author to address these 4 points that all fall within the reasonable and possible to vastly improve the manuscript.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsPlease check and improve the paper to make it more readable, for example in line 13, I suggest to change from “smart city” to "for smart cities" for consistency, in line 98 "when the 3D printing were involved" please change to "when 3D printing was involved", in line 222 "DT general support the 3D city simulations" should be "DT generally supports 3D city simulations.". In table 1 please ensure alignment is consistent. Check for extra spaces and adjust column widths if necessary. In figures 4 and 5 improve figure captions by including a brief summary of their relevance to the section. Consider expanding the section to detail the PRISMA process (e.g., search strategy and databases usage) to make the study more clear. I have no idea in relation to this paper what is its effect, if you can explain more or can you correct it properly on a few such points are like in what way recycled materials is boosting the sustainability of 3D printing, talk about smart concrete or nanomaterials in the future trends. Expand upon how machine learning algorithms can improve 3D-printing processes, infrastructure repairing and self-healing system
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article discusses the key advantages, application areas, and challenges of 3D printing technology in smart cities, which is a relevant topic. The integration of 3D printing with other technologies, such as artificial intelligence, digital twins, and machine learning, is innovative, and it proposes a roadmap for future research and practical applications. Overall, the paper has scientific research value, and the direction discussed is forward-looking.
1. In section 3.5, mentioned on lines 435-441, the paper correctly points out the necessity of interdisciplinary collaboration but only touches on the surface with the case of interdisciplinary collaboration. It would be beneficial to add case studies briefly describing how collaboration specifically impacts project success, including challenges encountered, solutions, and final outcomes.
2. In the section "Smart 3D Printing Materials for Smart Cities" (3.4), on lines 326-331, further addition of PZT sensor case studies could be beneficial to fully demonstrate the comparison between 3D printed PZT sensors and traditional sensors.
3. In Chapter 3, various challenges for future research and practical applications of 3D printing in smart cities are pointed out. It is suggested to further sort out the challenges faced and ideas for dealing with them.
4. On lines 107-108, it is recommended to further explain the significances of 0.0524 kilograms of carbon dioxide equivalent per kilogram.
5. On lines 64-71, it is suggested to add a chart showing the data changes in this section to increase readability and intuitiveness.
6. On lines 248-254, it is pointed out that 3D printing has completely changed the built environment within the framework of industry. It is recommended to further add actual cases or examples.
7. In the Methodology section, line 133, "keyword" should be changed to "keywords" as there are multiple keywords in the paper.
8. In the section "Wire Arc Additive Manufacturing (WAAM) for Smart Cities" (3.6), line 448, "use" should be changed to "uses".
Comments on the Quality of English Language
The English could be improved to more clearly express the research.
Author Response
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Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThis review paper presents how 3D printing innovation makes cities smarter by improving infrastructure, resource management, and community participation. The paper is well-structured. The research aim and tasks stated by the authors are straightforward and ultimately achieved. The methodology, using PRISMA principles, for selecting papers for the analysis is well-explained and can be duplicated. The author structured a paper to the following chapters: Introduction – Methodology – Review analysis and discussion – Conclusion.
However, the following comments can be mentioned:
1. It is recommended to explain and justify the mentioned fields of study (subchapter 3.1; Table 1).
2. It is unclear the following phrase: “…DT mainly serves with process of simulation stage before printing actual buildings as depicted in Fig. 4” (lines 212-214). At the same time, Fig. 4 presents a DT location after 3D printer.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe author has responded very well to the feedback of the first round of reviewers. Overall, the publication read well but I feel that concept are introduced without explanation. For instance, digital twins are not explained and the discussion moves immediately to applications in 3D printing. It would be beneficial to have a short definition. For example, this paper discusses smart city twins: https://www.mdpi.com/2072-4292/14/13/3095 . Digital twins also should be converted critically: https://link.springer.com/article/10.1007/s13347-021-00484-1
I am no expert in the other field but for each of the 10 sections a short definition with a reference like I suggested for Digital twins would help the reader to situate the technology.
Lastly, each section seems to have different depth which is not a problem a priori. However, I noticed that it affects the review character in some places. I believe that it would be good to ensure that each section covers the following points and expand the manuscript to ensure that everything is covered:
1. Definition
2. History/development
3. Applications
4. Advantages
5. Weakness/limitations
6. Cristal evaluation.
Currently, this information is there in some sections but not others. A more regular structure will help the reader to find information and make the review more relevant to practitioners.
Once these points are addressed, the work is ready to be published for me.
Author Response
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Author Response File: 
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