Dielectrophoretic Particle Chromatography: From Batch Processing to Semi-Continuous High-Throughput Separation
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
The manuscript focuses on the advances in frequency-modulated dielectrophoretic particle chromatography (DPC) and the Printed circuit board based dielectrophoresis (PCB) systems capable of demonstrating both high throughput and selective separation which are projects of the priority program SPP 2045, aiming to enhance technological approaches for the separation of fine particles. The manuscript not only reports the latest developments, but also assesses the capability of PCB setups to trap polystyrene particles (PS) of different sizes and declares the feasibility of such systems to trap particles as small as 200 nm. Given its novelty and the inspiration it may provide, the manuscript is recommended to address the following comments:
1. In some cases, the abbreviations are used before or without the introduction of the full names. For example, PS for polystyrene in line 11, PCB for Printed circuit board in line 32 and PDMS for polydimethylsiloxane in figure 1. This problem should be solved.
2. Line 18: the electrokinetic-based separation processes such as Electrophoresis whose applications in separating particles based on their charges are explained at https://doi.org/10.1002/elps.201900236 should also be mentioned.
3. Equation (1): the period sign should be removed.
4. Equation (3): the relative permittivity and the permittivity of the vacuum; as well as their relation to , introduced in line 49, should be defined.
5. Figure 1: The figure is overwhelmingly complex. Using terms like "front", "right-hand side," and "upper" to describe the positions makes it even more puzzling. The authors should present the items in separate panels and address them in the text accordingly.
6. The authors should provide a table comparing the conventional values of the operating parameters, such as the voltages, the frequencies, the flow rates etc., in DPC and PCB dielectrophoresis.
7. Lines 111 & 112: The possibility of Joule heating and its effect on DPC should be discussed.
8. Authors should compare the intensity of Joule heating in the DPC and PCB dielectrophoresis.
9. Line 225: What is the ionic strength of the background solution? Correspondingly, how much is the Debye length? To what extent does adjusting the ionic strength of the background solution (determining the thickness of the electric double layer) influence/improve the trapping efficiency of the smaller particles?
10. According to the operating voltages, applicability of the processes for separation/trapping of bioparticles without the denaturation issues should be discussed.
Comments on the Quality of English Language
Given its novelty and the inspiration it may provide, the manuscript is recommended to be published after addressing the following comments
Author Response
Please find our response attached.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authors
The paper titled "Dielectrophoretic Particle Chromatography: From Batch Processing to Semi-Continuous High Throughput Separation" by Giesler et al. presents the development of a microfluidic device for particle separation, utilizing dielectrophoretic force. The concept and experimental data make a valuable contribution to the existing knowledge in this field. Nevertheless, there are some issues that need to be addressed.
Figure 1 is confusing, and the authors should improve the setup explanations, possibly with schematic drawings. Additionally, PDMS is not defined.
The title implies progress from batch to semi-continuous high-throughput separation, but lacks a comparison with the previous batch process. A more comprehensive background introduction and quantification of "high throughput" in this semi-continuous separation are recommended.
Section 2.4: “After 300 seconds, the flow rate is adjusted to 10 mL/min to expedite the cleaning of the setup from previously trapped particles.”
The duration required for this cleaning process and whether increasing experiment time reduces trapping efficiency need clarification.
Section 3: “the 200 nm particles could be efficiently retained inside the channel at 1 mL/min and at reduced efficiency at higher flow rates.”
The assertion seems subjective to me. Why it is deemed effective with a trapping efficiency of 60% or lower.
Are there any limitations on the material properties of the particles, such as size/density ratio, shape, maximum size/density limit?
Author Response
Please find our response attached.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for Authors
The authors have provided very reasonable responses to all of my queries, and have revised the paper accordingly. I'm now happy to recommend acceptance.
