Investigation of Multidimensional Fractionation in Microchannels Combining a Numerical DEM-LBM Approach with Optical Measurements

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors of this manuscript have undertaken a comprehensive study of three distinct microfluidic particle separation systems, namely deterministic lateral displacement (DLD), serpentine channels,  and multi-orifice flow fraction (MOFF) channels. However, several major concerns have been identified during the review, which necessitate careful consideration and revision before recommending publication.

 

1.      Introduction and Structure:

The integration of numerical analysis and experimental approaches is a common methodology. Considering this, the introductory sections preceding the Results need simplification for improved clarity and focus.

2.      DLD Section:

The absence of experimental results in the DLD portion raises concerns, particularly as the authors previously explored numerical investigations of DLD extensively in Ref. 1. The manuscript fails to clearly communicate the novelty of the current findings in this context. It is recommended that the authors consider omitting the DLD section unless substantial new insights can be presented.

3.      Serpentine Channels Section:

A significant overlap is observed between the current manuscript and the authors’ previous work (Ref. 3) regarding serpentine channels. The reviewer notes similarities in figures, such as Fig.9 in the present work resembling Fig.7 in Ref.3. Similarly, Figure10 a, b, c, d in this work resembling Fig. 15, 18, 16, 19 in Ref. 3. This raises concerns about potential data reuse, necessitating clarification from the authors regarding the novel contributions presented in the current manuscript.

4.      MOFF Channel Section

The MOFF channel section lacks crucial experimental details, such as channel dimensions, supplier and product ID of fluorescent PS beads, and particle suspension formulation (e.g., concentration). Additionally, the absence of scale bars in Figs. 11 and 12 diminishes the clarity of the presented data. Addressing these shortcomings is essential to enhance the reproducibility and completeness of the experimental results.

 

In conclusion, the manuscript holds promise but requires significant revisions to address the outlined concerns. Clear communication of novel findings, eliminating redundant content, and providing comprehensive experimental details will substantially improve the manuscript’s quality.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In the described research work the authors describe a methodology to analyze the particle fractionation in various microchannel designs, that were shown previously to have the capability of separating particles. The claimed novelty of the work is that it combines experimental and computational approaches to extract information on the performance of the various designs. My comments are as follows:

1. The major claim of the work is that the experimental and computational methods can be used in a complementary manner. However some of the statements in the introduction seem to contradict this assertion. As an example, for the experimental methods one of the drawbacks listed is the inability to perform “the observation of particle and flow phenomena … (especially over channel height”. In the same time for the computational methods one of the downsides listed is that they are “often not able to observe the whole system”. This seems to indicate that the methods have similar limitations, rather than being complementary.

2. It is not clear if the fluid-structure interaction is considered in the problem. Do the particles modify the flow structure, or the flow fields are assumed known?

3. Is the computational modeling performed using a particular software package? If yes provide details on it.

4. I am assuming that the particles are considered as spherical. If that is the case, what part of their interaction with the system is affected by their rotational motion?

5. On figure 8 the details have to be magnified as the font is very small. Also it is not clear what the subplots (i), (ii) and (iii) are supposed to represent.

6. In Figure 9, it is not clear what is the meaning/significance of the numbers listed under (a), (b), (c), and (d).

7. The conclusion, that the particle fractionation depends on the density of particles is puzzling. Are the particles interacting with each other? Is this related with the point (2) above and a consequence of fluid-structure interactions? Please clarify.

8. In the experimental data shown (e.g. Figure 9) the particles streams are already focused based on size. It is important to show though the evolution of the streams closer to the entry point of the microchannels to see how the process of particle fractionation develops. This is particularly important as one of the issues discussed in the paper is the lack of a complete understanding of the particle fractionation.

Comments on the Quality of English Language

The use of English language is mostly fine. Some of the figure captions tend to be too long and in a few cases confusing. Particularly when specifying colors for various parts of a graph, use a legend instead as part of the figure, rather than a word description.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The issues and comments raised regarding the previous version of the manuscript have been addressed successfully.