Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds

Harry Felton; Robert Hughes; Andrea Diaz-Gaxiola

doi:10.1371/journal.pone.0245206

Peer Review History

Original SubmissionJuly 31, 2020
18 Sep 2020 Decision Letter - Zhan Li, Editor PONE-D-20-23937 Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds PLOS ONE Dear Dr. Hughes, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Nov 02 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Zhan Li, PhD Academic Editor PLOS ONE Journal Requirements: When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2.Thank you for stating the following in the Acknowledgments Section of your manuscript: [The authors would like to acknowledge the training & pump-priming funding award through BristolBridge (grant number EP/ M027546/1) under the Engineering and Physical Sciences Research Council (EPSRC) Bridging the Gaps between the Engineering and Physical Sciences and Antimicrobial Resistance cross-council AMR initiative, as well as pump-priming awarded by the Civil, Aerospace & Mechanical Engineering (CAME) School, University of Bristol. Harry Felton’s work reported in this paper has been undertaken as part of the Twinning of digital-physical models during prototyping project at the University of Bristol, which is funded by the EPSRC [grant number EP/R032696/1]. Andrea Diaz Gaxiola’s work has been funded by ONACYT, MEXICO (http://www.conacyt.gob.mx/).] We note that you have provided funding information that is not currently declared in your Funding Statement. However, funding information should not appear in the Acknowledgments section or other areas of your manuscript. We will only publish funding information present in the Funding Statement section of the online submission form. Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows: [The author(s) received no specific funding for this work.] Please include your amended statements within your cover letter; we will change the online submission form on your behalf. 3. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Partly Reviewer #2: Partly ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: The authors presented a 3D printing process for the development of interconnecting microchannel scaffolds with a resolution down to 100 micron and a nearly negligible cost. The work is interesting, the 3D printed microchannel devices showed a good promise towards real-world applications, but before I can consider recommending publication in PLOS One I would suggest the authors to address the following issues: 1. To keep the manuscript written in a concise way, the authors may consider removing some of the figures in the manuscript. For example, Fig 1 is a typical process that is not necessarily placed in the introduction section of the manuscript; fig 2 describes the results of a previous work of others and therefore, the figure shall not be used in this manuscript; fig 2-5 may be put together and some of the information can be put in the supplementary. 2. I would suggest the authors not to use words like "novel" "significantly" "drastically" repeatedly. 3. The authors demonstrated several 3D printed device prototypes and discussed their printed microchannel characterisations in a detailed manner. In this perspective, the readers can easily evaluate the 3D printing results. However, it is not possible to determine whether the printed devices perform well as there lacked control experiments of microchannel devices fabricated via other means in this work or there are no references to the studies of others to allow the readers to compare the device performance. I would suggest the authors to consider put more efforts on the discussion of the device performance. Reviewer #2: The paper presented a microfluidic device fabrication paradigm based on 3D printing technology. The modularized design and manufacturing of the channel scaffolds accelerated the realization of microfluidic systems with low-cost. Through the authors giving thorough descriptions of every detail of the printing settings, this manuscript's major issue is the lack of sound analysis on explaining the reason for choosing fabrication parameters. Some other technical comments: 1. The descriptions on the 3d printing technology, 3d printer, and the slicing software in this work is trivial since the layer manufacturing has already been employed in the microfluidic and microelectronics fields with a lot of achievements, referring to ref. [1]. The manuscript should be shortened with a concise introduction of the settings related to mold design and fabrication. 2. In an FDM, process planning, which includes slicing and print path planning, is vital in determining print quality. Instead of listing all the printer settings, to improve the printing quality (section 2.2.2), the authors are suggested to further investigating the key parameters (like slicing height, line width, infill pattern, et al.) that affect the material deposition. Many works related to the print quality improvement of FDM has been overlooked, such as ref. [2,3]. Furthermore, the qualitative evaluation results listed in Table 2 seems meaningless for other practitioners or other print parts. The quantified analysis of the reason for unsuccessful printing should be made. 3. What are the advantages of this work over other 3d printed microfluidic devices, such as ref? [4]. To the best of my understanding, the device fabricated by the method of this work is simply two dimensional (the height is constant). Can the method be extended to a more complex device with variable height? Moreover, the authors may show some comparisons with others’ works. The 3d printed microfluidic device is an exciting topic, and the low-cost one is desperately needed in the academic sector. The author presented a complete process in realizing the fast fabrication of the device. However, the current manuscript is more like an introduction to instructing practitioners to design and manufacture the microfluidic device step-by-step. The manuscript has too much trivial information related to the print settings, which could be shortened, while lacks sufficient explanations on the key factors that affect the deposition accuracy or print surface quality. More quantified analysis related to the relationship between print parameters and the accuracy of the fabricated part should be added. The effectiveness of more demonstrations of the device can also be validated. Based on the above concerns, I suggest a major revision of this paper. Reference: [1] R. D. Sochol et al., “3D printed microfluidics and microelectronics,” Microelectronic Engineering, vol. 189. pp. 52–68, 2018. [2] A. Dey and N. Yodo, “A systematic survey of FDM process parameter optimization and their influence on part characteristics,” J. Manuf. Mater. Process., vol. 3, no. 3, p. 64, 2019. [3] G. Q. Jin, W. D. Li, and L. Gao, “An adaptive process planning approach of rapid prototyping and manufacturing,” Robot. Comput. Integr. Manuf., vol. 29, no. 1, pp. 23–38, 2013. [4] S. Tsuda et al., “Customizable 3D printed ‘Plug and Play’ millifluidic devices for programmable fluidics,” PLoS One, vol. 10, no. 11, pp. 1–13, 2015. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0245206.r001
Revision 1
12 Nov 2020 Author Response Please see attached response to reviewers comments document which is highlighted for easy reading. Reviewer #1: The authors presented a 3D printing process for the development of interconnecting microchannel scaffolds with a resolution down to 100 micron and a nearly negligible cost. The work is interesting, the 3D printed microchannel devices showed a good promise towards real-world applications, but before I can consider recommending publication in PLOS One I would suggest the authors to address the following issues: The authors would like to thank Reviewer 1 for their helpful comments and suggestions. 1. To keep the manuscript written in a concise way, the authors may consider removing some of the figures in the manuscript… …For example, Fig 1 is a typical process that is not necessarily placed in the introduction section of the manuscript; Figure 1 has been removed and all references to it deleted. The authors now reference suitable literature for the process. …fig 2 describes the results of a previous work of others and therefore, the figure shall not be used in this manuscript; The authors have noticed that the wording in the manuscript relating to Figure 2 (now Fig.1) may have caused confusion. All of the images in Figure 2 were produced by the authors themselves and corroborate the work of others as referenced in the manuscript. The figure itself is important for successfully communicating these motivations and correctly framing the work so has been kept. However, the authors have made clearer in the manuscript that the work is original and not from the work of others. …fig 2-5 may be put together and some of the information can be put in the supplementary. Thank you for your recommendation. The authors have removed Figure 5 and now include it in the supplementary material (see S.8). We have also greatly simplified the description of print failures in the main manuscript. However, the authors feel that the remaining figures (originally figures 2-4, now 1-3) are individually important and more informative when separated in their respective positions, as they each discuss different aspects of the work. The authors therefore feel that combining them would result in an overly large and complicated figure that would confuse more than enhance the reading of the manuscript. This approach appears consistent with other PLOS One papers. 2. I would suggest the authors not to use words like "novel" "significantly" "drastically" repeatedly. Thank you for your suggestion. We acknowledge the overuse of certain words and have altered the manuscript to eliminate excessive occurrences of “novel” and “significantly”. On inspection, there were no uses of the word “drastically” in the original manuscript. 3. The authors demonstrated several 3D printed device prototypes and discussed their printed microchannel characterisations in a detailed manner. In this perspective, the readers can easily evaluate the 3D printing results. However, it is not possible to determine whether the printed devices perform well as there lacked control experiments of microchannel devices fabricated via other means in this work or there are no references to the studies of others to allow the readers to compare the device performance. I would suggest the authors to consider put more efforts on the discussion of the device performance. This is a very helpful point. Thank you. Due to the current restrictions in place due to COVID, additional control experiments have not been possible at this time. The authors have taken the opportunity to further examine and compare the devices to the performance of similar devices fabricated using other methods obtained from the literature and have discussed their performance more thoroughly, specifically in relation to the polydispersity of droplets from droplet generators. We have also now included a discussion to highlight the key advantages and compared to other works. The authors believe that this satisfies the concerns and helps to further validate the approach. Reviewer #2: The paper presented a microfluidic device fabrication paradigm based on 3D printing technology. The modularized design and manufacturing of the channel scaffolds accelerated the realization of microfluidic systems with low-cost. Through the authors giving thorough descriptions of every detail of the printing settings, this manuscript's major issue is the lack of sound analysis on explaining the reason for choosing fabrication parameters. Some other technical comments: The authors would like to thank Reviewer 2 for their valuable suggestions and comments. Please see more detailed comments below regarding the analysis of the parameters chosen. 1. The descriptions on the 3d printing technology, 3d printer, and the slicing software in this work is trivial since the layer manufacturing has already been employed in the microfluidic and microelectronics fields with a lot of achievements, referring to ref. [1]. The manuscript should be shortened with a concise introduction of the settings related to mold design and fabrication. The introduction to this section has now been made more concise, and discusses other work, however, the authors feel it is important to specify the printer being used, along with the material, as this can have a significant effect on the results of the testing. Changing to a printer with a dual-geared feed, for example, would improve the control over material feed rate and would therefore change the statistics around print success. However, testing has now been completed with alternative brands of PLA – with minor modifications to print settings – and this has been made clear in the text. 2. In an FDM, process planning, which includes slicing and print path planning, is vital in determining print quality. Instead of listing all the printer settings, to improve the printing quality (section 2.2.2), the authors are suggested to further investigating the key parameters (like slicing height, line width, infill pattern, et al.) that affect the material deposition. Many works related to the print quality improvement of FDM has been overlooked, such as ref. [2,3]. The authors are not sure what the reviewer is referencing here. The print settings, in this instance at least, are the same as print parameters (slicing height – or layer height – and line width are both specified in Table 1). Infill pattern is not appropriate for discussion within the paper as the prints are either single line width or shell prints only. Having read the references provided, they discuss the effect of print parameters on parts of a much larger scale – several mm in each direction rather than µm - and thus are not directly applicable to this work. We would like to thank you for raising the points surrounding print path planning as we have omitted this from the original paper. As such we have added a paragraph discussing why we have not manually – or with an original piece of code – planned out print paths, instead allowing Cura to do this for us. In brief, our reasons for doing this were to allow non-expert users (the target for this technology in many instances) to quickly adopt the process. We hope that these changes satisfy the reviewers concerns. …Furthermore, the qualitative evaluation results listed in Table 2 seems meaningless for other practitioners or other print parts. The quantified analysis of the reason for unsuccessful printing should be made. Once again, thank you to the reviewer for their comments. Based on their feedback the authors have added a section analysing the size distribution of the 3D printed moulds to define the groupings more clearly as a replacement for Table 2, providing a quantitative distribution instead of a qualitative grouping. In short, 500 scaffolds were printed over the two channel sizes and measured, producing lognormal distributions for the channel widths produced. The raw sizing data is provided in the supplementary data (S.7). The failure mechanisms have also been quantitively described using the same data set as the distributions now use; albeit with the caveat that this is highly variable depending on the print bed levelling and filament feed control. Clearer definitions of the context we have used the terms “Print Success” and “Useable Print” in are also provided. This work has been presented for the 350 µm and 100 µm channels. With regards to the applicability to other print parts, the methods, settings, and statistics presented in the paper directly relate to the designs discussed therein. However, the authors expect future work to consider further designs and, through making the methods publicly available, fully support others investigating the methods applicability to other designs. 3. What are the advantages of this work over other 3d printed microfluidic devices, such as ref? [4]. To the best of my understanding, the device fabricated by the method of this work is simply two dimensional (the height is constant). Can the method be extended to a more complex device with variable height? Moreover, the authors may show some comparisons with others’ works. Thank you for your questions. The devices fabricated using this method are indeed 2D at the moment, as are many microfluidic devices being used at present, however, the authors believe that more complex 3D designs would indeed be possible with some alterations to the fabrication process. This will be the focus of subsequent work by the authors. The authors see the major advantages this process has over other 3D-printed devices as being the very rapid printing and fabrication time (~<5mins), the very low cost per device, the reduction in channel resolution (100um) for FDM prints, and the method reliability (in part due to the above 2 points and the ability to print sections independently so whole prints do not have to be thrown out if errors occur). In addition, this method uses minimal additional resources (i.e. oxygen plasma treatment or chemicals such a dichloromethane used in the reference mentioned by the reviewer) to fabricate the final devices, besides a method of heating, which are readily available. To clarify the above, the authors have now included a discussion section to summarise the advantages of the work as well as compare to other approaches. We have also (as recommended by Reviewer 1) made a critical assessment and comparison of the polydispersity of droplets produced by the droplet generation devices fabricated using this method, and compared them to others’ works in order to evaluate the efficiency of the technique. We hope and believe that these additions will satisfy the reviewers concerns. The 3d printed microfluidic device is an exciting topic, and the low-cost one is desperately needed in the academic sector. The author presented a complete process in realizing the fast fabrication of the device. However, the current manuscript is more like an introduction to instructing practitioners to design and manufacture the microfluidic device step-by-step. The manuscript has too much trivial information related to the print settings, which could be shortened, while lacks sufficient explanations on the key factors that affect the deposition accuracy or print surface quality. More quantified analysis related to the relationship between print parameters and the accuracy of the fabricated part should be added… Thank you for your feedback. As discussed in relation to comments by Reviewer 1 and your previous comment, the authors have re-edited the sections relating to print settings to eliminate trivial or overly verbose explanations in an effort to make the manuscript more concise and direct. However, this paper is meant to be instructive for non-expert users, and as such we believe that the information presented to allow a practitioner to undertake each step is important. In addition to this, and as previously stated, the machine used will have a considerable effect on the quality of the printed artefacts. As such, a detailed quantified analysis of the effect of print settings for this specific printer did not seem as valuable as detailing the performance of the fabricated channels – something we have now done in more detail – for this introductory work. It is also important to understand that there are ~500 settings that can be changed in Cura, many of which will affect the parts being printed. To thoroughly discuss the important settings would require a substantial investigation with a considerably different focus. As the paper originally presented, we have listed some of the key print settings/parameters with a brief explanation to provide context to the results included. We hope this is satisfactory. However, based on your feedback, we have added a sizing analysis for the settings used to demonstrate more clearly what is being achieved and act as a line in the sand for anyone who may replicate the procedure. Future papers are planned that aim to investigate the effect individual settings/groups of settings have on the print quality and success in more depth. With regards to print surface quality, this is not a concern using this method (as shown by Fig.5) due to the smoothing effect of the thermal bonding process. As such the channel surface quality and repeatability of channel dimensions are both improved (Fig.7). …The effectiveness of more demonstrations of the device can also be validated… The authors have included additional droplet sizing evaluation, such that the devices’ performance has now been further analysed and validated against other literature resources with similar purpose, such as droplet generators, that have been fabricated through other methods. Based on the above concerns, I suggest a major revision of this paper. Additional Changes: In addition to the above changes, the authors have also made a number of minor alterations to certain wording and phrasing in order to improve clarity and make the manuscript more concise. The authors have also included additional droplet generation data and microscope images in Fig.9 to support the analysis of droplet polydispersity in the text. Thank you again for you time and consideration of our manuscript. We appreciate all of the suggestions and believe these have greatly improved the quality of the paper. Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0245206.r002
18 Dec 2020 Decision Letter - Zhan Li, Editor PONE-D-20-23937R1 Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds PLOS ONE Dear Dr. Hughes, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Feb 01 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Zhan Li, PhD Academic Editor PLOS ONE [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: I Don't Know ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: Thank the authors for the revision of this manuscript. The authors have addressed my previous querries and concerns. I therefore recommand publication in Plos One. Reviewer #2: The authors have made significant improvements in the revised version of the manuscript. Most of my concerns have alleviated. The 3d-printing-based microfluidic device fabrication method introduced in the paper substantially lowers the barrier for undergraduate students and other industry practitioners with low cost and easy-to-implement processes. The authors elaborate on all the 3d modeling, printer setting, and fabrication parameters. Before considering for publication, some minor issues are expected to be resolved: 1. Page 2, Figure 1, I cannot find figure 1(g), which is introduced in the caption of Figure 1. 2. Table 1, the unit of the build plate temperature is wrong. 3. Make sure all the literature is correctly referenced (e.g., Line 213). ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0245206.r003
Revision 2
21 Dec 2020 Author Response Reviewer #1: Thank the authors for the revision of this manuscript. The authors have addressed my previous querries and concerns. I therefore recommand publication in Plos One. Thank you very much for your feedback and your constructive comments. They were greatly appreciated. Reviewer #2: The authors have made significant improvements in the revised version of the manuscript. Most of my concerns have alleviated. The 3d-printing-based microfluidic device fabrication method introduced in the paper substantially lowers the barrier for undergraduate students and other industry practitioners with low cost and easy-to-implement processes. The authors elaborate on all the 3d modeling, printer setting, and fabrication parameters. Before considering for publication, some minor issues are expected to be resolved: We would like to thank the reviewer for their comments and attention to detail. We have corrected these issues. 1. Page 2, Figure 1, I cannot find figure 1(g), which is introduced in the caption of Figure 1. Thank you very much for noticing this. This has been corrected. 2. Table 1, the unit of the build plate temperature is wrong. Again, we thank you for pointing this out. This has been corrected. 3. Make sure all the literature is correctly referenced (e.g., Line 213). Thank you. We have corrected this issue. Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0245206.r004
23 Dec 2020 Decision Letter - Zhan Li, Editor PONE-D-20-23937R2 Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds PLOS ONE Dear Dr. Hughes, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Feb 06 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Zhan Li, PhD Academic Editor PLOS ONE Additional Editor Comments (if provided): There are still some errors and typos as pointed out by the reviewer, which are not yet corrected, e.g., "...Images e-g) show characteristic ridges of 101 channels manufactured using SLA moulds printed at an angle to the substrate plane to improve print resolution..." in the caption of Fig. 1. [Note: HTML markup is below. Please do not edit.] [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0245206.r005
Revision 3
23 Dec 2020 Author Response Reviewer #1: Thank the authors for the revision of this manuscript. The authors have addressed my previous querries and concerns. I therefore recommand publication in Plos One. Thank you very much for your feedback and your constructive comments. They were greatly appreciated. Reviewer #2: The authors have made significant improvements in the revised version of the manuscript. Most of my concerns have alleviated. The 3d-printing-based microfluidic device fabrication method introduced in the paper substantially lowers the barrier for undergraduate students and other industry practitioners with low cost and easy-to-implement processes. The authors elaborate on all the 3d modeling, printer setting, and fabrication parameters. Before considering for publication, some minor issues are expected to be resolved: We would like to thank the reviewer for their comments and attention to detail. We have corrected these issues. 1. Page 2, Figure 1, I cannot find figure 1(g), which is introduced in the caption of Figure 1. Thank you very much for noticing this, and to the editor for highlighting this again. This was an issue with the figure itself not the caption. We have therefore uploaded a corrected figure with the correct lettering to remedy this issue. 2. Table 1, the unit of the build plate temperature is wrong. Again, we thank you for pointing this out. This has been corrected. 3. Make sure all the literature is correctly referenced (e.g., Line 213). Thank you. We have corrected this issue. The authors have also conducted a final proof-read the manuscript as recommended by the editor, and have corrected a number of minor errors and typos shown in the tracked changes version of the manuscript. We therefore believe we have corrected all outstanding issues raised by the reviewers and the editor. Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0245206.r006
26 Dec 2020 Decision Letter - Zhan Li, Editor Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds PONE-D-20-23937R3 Dear Dr. Hughes, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Zhan Li, PhD Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0245206.r007
Formally Accepted
18 Jan 2021 Acceptance Letter - Zhan Li, Editor PONE-D-20-23937R3 Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds Dear Dr. Hughes: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Zhan Li Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0245206.r008

Open letter on the publication of peer review reports

PLOS recognizes the benefits of transparency in the peer review process. Therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. Reviewers remain anonymous, unless they choose to reveal their names.

We encourage other journals to join us in this initiative. We hope that our action inspires the community, including researchers, research funders, and research institutions, to recognize the benefits of published peer review reports for all parts of the research system.

Learn more at ASAPbio .