Innovative Ultrasonic Spray Methods for Indoor Disinfection

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this manuscript the authors proposed the different methods for improving the dispersion of disinfectant aerosols to overcome existing problems in using standard and widely used methods such as hydraulic and pneumatic. The proposed ultrasonic techniques are found to be more effective in generating appropriate aerosol size distributions for sanitizing purpose. The presented combined cavitation and multistage techniques have been demonstrated by developing and testing prototype devices having various designs (different operating frequency and productivity).

Generally, this is interesting paper since the technology of fine aerosol generating and dispersion  of disinfectant liquids are important issue.

The manuscript is well structured, in the introduction part most important previous studies and challenges have been analyzed.  The methodology part is reasonably described and the obtained conclusions are rationally supported by the results.

From my point of view, there is no new science presented in the study, it is rather technological improvement and the major contribution of the paper are the results obtained during the experimental phase of testing the devices developed for spraying disinfectant liquids. However, I believe it could be interesting and useful for the wider community.

Please find below several comments which can be addressed to improve the overall paper before publishing.

Lines 281-282: “The calculation of the distribution of the sound pressure level inside the tubular emitter was carried out in the ANSYS program.” I suggest to add brief explanation and information about parameters used in calculations.

It is stated “ Innovative specialized ultrasonic atomizers are introduced, capable of producing aerosols with the required droplet size and efficiency from disinfectant liquids of varying viscosities, including those containing silver nanoparticles”.  It seems that the presented results are related to the water droplet under different conditions, but there are no other liquids tested? Are there any results or experiments using silver nanoparticles, different  viscosities etc…if so, authors should briefly add few sentences to explain this statement.

Figure 14 and Figure 15: Although the dependence is clear, it would be interesting if the authors can provide some kind of error assessment.

It would be interesting to briefly describe the procedure and conditions during particle size distribution measurements.

I suggest authors to carefully check typing and technical errors, for example:

Figure 10. Please check number 4 missing

Line 22: “..in some caseshe emergence of…”

Line 33: “.. prevention,

Line 36, Line 84,

Line 202: “….surface through 12 through holes..”

Line 335: “..spraying is about 10...20 ml/s

Author Response

The authors thank the respected Reviewer for his attention to our work, his time and valuable comments. We have tried to answer the questions and correct the text according to the Reviewer's comments.

1. Lines 281-282: “The calculation of the distribution of the sound pressure level inside the tubular emitter was carried out in the ANSYS program.” I suggest to add brief explanation and information about parameters used in calculations.

            Thank you very much for your question. The Harmonic Acoustics module of harmonic acoustic analysis was used in the calculations. The volume of the calculation area was limited by the inner surface of the tubular radiator. Boundary conditions were set at the ends of the calculation area: radiation boundary. The following air parameters were used in the calculations: sound speed – 343 m/s; density – 1.2 kg/m³. The corresponding information was added to the article. (p. 10).

2. It is stated “Innovative specialized ultrasonic atomizers are introduced, capable of producing aerosols with the required droplet size and efficiency from disinfectant liquids of varying viscosities, including those containing silver nanoparticles”.  It seems that the presented results are related to the water droplet under different conditions, but there are no other liquids tested? Are there any results or experiments using silver nanoparticles, different  viscosities etc…if so, authors should briefly add few sentences to explain this statement.

            Indeed, the abstract looks too brief, which causes misunderstanding of the meaning of the work. The work summarizes the results of the authors for 15 years related to the development of ultrasonic atomizers based on various spraying methods, including completely new ones that have no analogues. Spraying of liquids is required for various purposes, but we focused on the purposes of air and surface disinfection. In this sense, it is important to create devices capable of spraying liquids with various physicochemical properties, viscosity, surface tension, suspensions (for example, with silver particles). In this work, we did not dwell on the detailed characteristics of the operation of devices with different liquids, since this is not included in our goals - a review of ultrasonic spraying devices. However, in the text of the article, we mentioned that ultrasonic spraying methods and the described devices allow spraying liquids even of high viscosity (for example, suspensions), which is important for disinfection purposes. We changed the abstract.

Abstract: This study explores the challenges associated with dispersing disinfectant liquids for sanitizing individuals, indoor spaces, vehicles, and outdoor areas. Among the various approaches, fine aerosol sprays with a high particle surface area emerge as a particularly promising solution. Ultrasonic spraying, which leverages diverse mechanisms of ultrasound interaction with liquids, offers several distinct advantages. Notably, it enables the production of fine aerosols from liquids with a broad range of physical and chemical properties, including variations in purity, viscosity, and surface tension. This capability is especially critical for disinfectant liquids and suspensions, which often exhibit low surface tension and/or high viscosity. The article provides a comprehensive review of ultrasonic spraying methods and technologies developed by the authors' team in recent years. It highlights innovative ultrasonic sprayers, including the latest designs, which are capable of generating aerosols with precise dispersion characteristics and high productivity from disinfectant liquids in a wide range of physical and chemical properties.

3. Figure 14 and Figure 15: Although the dependence is clear, it would be interesting if the authors can provide some kind of error assessment.

            Thank you for your valuable comment. We have added standard error bars to the figures.

4. It would be interesting to briefly describe the procedure and conditions during particle size distribution measurements.

            Thank you for your question. Particle size measurements in all experiments were performed using a Malvern SprayTec particle analyzer. The analyzer operates on the principle of laser diffraction. The Spraytec analyzer measures particle dispersion with a frequency of up to 10 kHz in the range from 0.1 to 2000 µm. The laser beam of the particle analyzer was located at a distance of 50 mm from the end of the sprayer during measurements. Settled tap water was used as the sprayed liquid. The corresponding information was added to the article, at the beginning of section 3.1

I suggest authors to carefully check typing and technical errors, for example:

Figure 10. Please check number 4 missing

Line 22: “..in some caseshe emergence of…”

Line 33: “.. prevention,

Line 36, Line 84,

Line 202: “….surface through 12 through holes..”

Line 335: “..spraying is about 10...20 ml/s

We have completely rewritten the Introduction following the Reviewers' wishes and also checked the text for errors. Corrected spelling, grammar and stylistic errors are highlighted in green in the text.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors please find my comments in the attached PDF file.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

I have provided my comments in the attached pdf file to the authors

Author Response

The authors thank the respected Reviewer for his attention to our work, his time and valuable comments. We have tried to answer the questions and correct the text according to the Reviewer's comments.

1) The authors should clarify whether this is a review paper or an original research article, as the current presentation is confusing regarding whether the data is original or sourced from secondary research.

This article summarizes more than 15 years of the authors' experience in developing ultrasonic atomizers. All atomizers designs and results were obtained by the authors personally. This phrase has been added to the end of the Introduction section. The abstract has also been corrected for better understanding.

2) Though the manuscript is interesting, however it does not follow any format of the manuscript. This may lead to confusion for readers regarding the nature of the research

We would like to clarify that our manuscript should not be considered solely as an Original Research Article. While it introduces two innovative ultrasonic spraying methods and devices, a substantial portion of the manuscript is dedicated to a review of our team's research over the past 15 years. This synthesis aims to contextualize the evolution of our work and highlight the advancements achieved through the new methods. Thus, the manuscript is best viewed as a review + original research hybrid, providing both a comprehensive overview of our contributions to the field and detailed insights into our latest developments. We hope this explanation will help you evaluate the manuscript within its intended scope.

The abstract has been corrected to more accurately reflect the nature of the article.

 

3) A dedicated methodology section is necessary to clearly outline how the data was generated. The authors should present a detailed experimental design for testing the efficiency of these instruments.

Since our article does not follow the format of a standard research article (see answer to p. 2), such a section is hardly appropriate. The operating principles and characteristics of the developed devices for ultrasonic liquid spraying are described. However, information on measuring instruments for monitoring the dispersion of the resulting aerosol is added.

All particle size measurements were conducted with a Malvern SprayTec particle analyzer. The analyzer operates on the principle of laser diffraction. The SprayTec analyzer measures particle dispersion at frequencies up to 10 kHz, within a range of 0.1 to 2000 μm. The laser beam of the particle analyzer was located at a distance of 50 mm from the end of the sprayer during measurements. Settled tap water was used as the sprayed liquid.

 

4) The abstract is currently too brief and should be expanded to include context for the study. The authors need to provide background information that highlights the research gaps leading to the development of this study.

            Thank you, this is a very valuable comment. The abstract has been corrected and supplemented.

Abstract: This study explores the challenges associated with dispersing disinfectant liquids for sanitizing individuals, indoor spaces, vehicles, and outdoor areas. Among the various approaches, fine aerosol sprays with a high particle surface area emerge as a particularly promising solution. Ultrasonic spraying, which leverages diverse mechanisms of ultrasound interaction with liquids, offers several distinct advantages. Notably, it enables the production of fine aerosols from liquids with a broad range of physical and chemical properties, including variations in purity, viscosity, and surface tension. This capability is especially critical for disinfectant liquids and suspensions, which often exhibit low surface tension and/or high viscosity. The article provides a comprehensive review of ultrasonic spraying methods and technologies developed by the authors' team in recent years. It highlights innovative ultrasonic sprayers, including the latest designs, which are capable of generating aerosols with precise dispersion characteristics and high productivity from disinfectant liquids.

 

5) The keywords should be revised for better relevance and specificity.

            The keywords have also been revised. They now look like this:

Keywords: pathogens; ultrasound-based disinfection; ultrasonic atomization; advanced aerosol technologies; innovative spraying devices.

 

6) The authors need to clarify whether the disinfection efforts target a specific virus or if they apply to other microbes as well. Please revise the title accordingly to reflect to the exact content of the manuscript

            Disinfection aerosols, as a rule, do not have a selective effect on specific viruses or bacteria, therefore, the title and text of the article do not mention those specific bacteria and viruses that can be destroyed by aerosols sprayed by ultrasonic means. It seems that the title of the article, just reflects the content of the manuscript, but the keywords (there was only the word "virus" can be misleading). The keywords have been revised. In the text of the article, where viruses are mentioned, bacteria are now also mentioned, which will more accurately reflect the meaning of disinfection measures.

 

7) Please check for typo errors in lines 21 to 23 of the introduction

            8) The sentence in lines 20 to 24 of the introduction is too lengthy; it should be broken into shorter sentences for clarity.

            9) There is a typo error in line 29 that needs correction.

            10) Spelling mistakes are present in line 33 and should be addressed.

            11) Corrections are needed for line 36.

In response to your comments 7-11: The Introduction has been completely rewritten, taking into account the comments of the Reviewers and checked for errors. Thank you for your careful reading of our text! Corrected errors in the text are highlighted in green (except for the Introduction and Conclusion, which have been completely rewritten)

 

12) The introduction is confusing and hard to follow. The authors are advised to reorganize it, providing background information from general to specific, while clearly highlighting the main research gaps. The rationale statement at the end should be expanded to be clearer and more comprehensive.

 

The introduction has been rewritten taking into account your comments.

 

13) In the results and discussion section, the authors should compare their findings with those from similar studies. https://doi.org/10.3390/su16062233

           

14) The authors are advised to add some up to date references to support their claim. https://doi.org/10.1016/j.scitotenv.2022.160322

 

Thank you, we have studied the articles you suggested and added links to the Introduction

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

 

General Comments: The work proposes ultrasonic atomization as an improved method for indoor disinfection. Traditional spraying methods suffer from limitations such as large droplet size, uneven coverage, and waste. Ultrasonic atomization offers greater control over droplet size and compatibility with various disinfectants. The authors present several innovative ultrasonic atomizer designs, including wearable devices and acoustic-dynamic methods. Experimental results demonstrate the effectiveness of these methods in producing fine aerosols with potential benefits for disinfection efficiency and safety. Specific comments for a major revision are provided below.

Major Comments:

1. Introduction Section: While a good overview of the problem is presented in the introduction, the readers will benefit from a more focused text. This could be done by more clearly stating the specific gap in knowledge that ultrasonic atomization addresses and its advantages over existing methods. While generally clear language is used in the introduction, there are some instances of awkward phrasing or grammatical errors. The authors should carefully proofread the manuscript before submitting it again. To effectively connect the discussion of viruses to the need for effective disinfection methods, the first paragraph should be revised. It should also clearly state the limitations of hydraulic and pneumatic spraying, such as uneven coverage, waste, and inhalation risks, and how these limitations impact disinfection efficacy. The specific advantages of ultrasonic atomization in addressing these limitations, particularly for disinfectants with varying viscosities and those containing silver nanoparticles, should be emphasized.
2. Methodology Section:
• In Section 2.1, please provide more context for Figure 1. Explain the function of each component in more detail. Clarify the purpose and importance of controlling the spray surface shape and size.
• In Section 2.2, please provide more details about the design and operation of the wearable atomizers (Figures 5 and 6). Explain how the flexural-oscillating disk works and why it is advantageous for these applications. Clarify the role of the fan in Figure 6.
• In Section 2.3, please provide a more thorough explanation of the underlying physics of multi-stage spraying and the cavitation combined method. Clarify how these methods address the limitations of traditional ultrasonic atomization.
3. Results and Discussion Section:
• In Section 3.1, please expand the discussion of Figure 12. Analyze the differences in droplet size distribution between ultrasonic and hydraulic atomization. Explain the implications of these differences for disinfection effectiveness.
• In Section 3.2, please provide more context for Figure 13. Explain the experimental setup and conditions in more detail. Discuss the significance of the observed droplet size reduction at different stages of the multi-stage spraying process.
• In Section 3.3 (Figure 15), please label the axes clearly and include units. Discuss the relationship between ultrasound amplitude, hydraulic pressure, and droplet size in more detail. Explain the practical implications of these findings for optimizing disinfection protocols.

4.      Other Figures: Please ensure a consistent style across all figures by using the same font size and style for all text.

• In Figure 2, please improve the clarity of this figure by using different colors or line styles to distinguish between the liquid spread and the channels. Add arrows to indicate the direction of liquid flow.
• In Figures 7 and 10, these schematic diagrams are helpful but could be improved with clearer labels and annotations. Consider using arrows to show the movement of droplets and the direction of forces.
4. Conclusions Section: To enhance the effectiveness of your conclusions, be more specific by summarizing the key findings of your study and their implications for the field of disinfection. Highlight the potential impact of your work on improving disinfection practices and public health. Reconnect your findings back to the research question and the advantages of your proposed methods. Additionally, discuss the potential limitations of your study and suggest directions for future research.

Author Response

The authors thank the respected Reviewer for his attention to our work, his time and valuable comments. We have tried to answer the questions and correct the text according to the Reviewer's comments.

 

1. Introduction Section:While a good overview of the problem is presented in the introduction, the readers will benefit from a more focused text. This could be done by more clearly stating the specific gap in knowledge that ultrasonic atomization addresses and its advantages over existing methods. While generally clear language is used in the introduction, there are some instances of awkward phrasing or grammatical errors. The authors should carefully proofread the manuscript before submitting it again. To effectively connect the discussion of viruses to the need for effective disinfection methods, the first paragraph should be revised. It should also clearly state the limitations of hydraulic and pneumatic spraying, such as uneven coverage, waste, and inhalation risks, and how these limitations impact disinfection efficacy. The specific advantages of ultrasonic atomization in addressing these limitations, particularly for disinfectants with varying viscosities and those containing silver nanoparticles, should be emphasized.

 

The introduction has been rewritten based on your comments.The new version provides a clear articulation of the knowledge gap, limitations of existing methods, and the advantages of ultrasonic atomization while setting up the study's purpose.

 

 

1. Methodology Section:

• In Section 2.1, please provide more context for Figure 1. Explain the function of each component in more detail. Clarify the purpose and importance of controlling the spray surface shape and size.

 

Thank you very much for your valuable comment. For Figure 1, we have added the following description to the text of the article:

 

The design scheme of the ultrasonic atomizer developed by the authors is based on the half-wave Langevin transform. It consists of a concentrator 1, a spray surface 2, piezoceramic elements 3, and a reflective pad 4. The type of conversion of electrical energy into mechanical vibrations is piezoelectric. Inside, in the center of the Langevin converter, a through channel 5 is made for feeding the sprayed liquid to the spray surface 2. The atomizer is installed in a housing 7, in the rear flange 7 of which there are places for connecting the liquid supply systems 8 and for inputting an electric cable 9 (for exciting vibrations of the piezoelectric elements).

 

We also formulated the goal – the importance of controlling the shape and size of the spray surface. We added the following text:

When liquid is fed from the hole 5, it spreads on the surface 2 in a thin layer. Ultrasonic vibrations generate standing capillary waves on the liquid surface. Droplets detach from the crests of these waves and are ejected with an initial velocity perpendicular to the surface. Therefore, by changing the shape of the spray surface (for example, making it a cone with a different angle at the top), we can change the direction of droplet separation and, accordingly, the width of the spray torch, making it wider or narrower.

The number of capillary waves per unit area of the spray surface is finite, depending on the frequency of ultrasonic vibrations [15]. At a given frequency (which determines the size of the droplets), the spray performance is dictated by the area of the spray surface. The larger the surface area, the higher the spray performance.

 

• In Section 2.2, please provide more details about the design and operation of the wearable atomizers (Figures 5 and 6). Explain how the flexural-oscillating disk works and why it is advantageous for these applications. Clarify the role of the fan in Figure 6.

 

Thanks for your comment. We've added additional description to the article (p.7,8).

Using a disk enables a nearly unrestricted increase in the spray surface area by exciting bending oscillations in higher-order modes. In turn, the use of a disk allows for a virtually unlimited increase in the area of the spray surface due to the excitation of bending oscillations at higher modes. This also reduces the disk's thickness, positively impacting the sprayer's mass and size characteristics. In general, the operation of the disk is similar to the oscillations of a membrane with free edges with central excitation of oscillations. The distribution of oscillations over the surface of such a disk is described by Bessel functions of the corresponding order (equal to the oscillation mode of the disk). The resonant frequency of the sprayer is 40 kHz. Liquid is delivered to the spray surface through 12 holes positioned at the disk's zero-oscillation points. The principle of constructing the oscillating system of the atomizer is similar to that shown in Fig. 1.

As shown in Figure 6, the sprayer includes a pistol-type handle (9). On the handle there is a button 10 for starting the spraying. In this case, electric oscillations of ultrasonic frequency are supplied from the generator to the piezoelectric elements of the sprayer and the sprayed liquid is simultaneously supplied to the spray surface 4, through channels 6. The electric oscillation generator operates from a 12 V battery and can be placed in a portable backpack behind the operator (together with a volume with a disinfectant solution).

Also added a description of the role of the fan in Figure 6. Directly in the caption to Figure 6 we indicated that “4 – fan for cooling the piezoelectric transducer of the atomizer”

 

• In Section 2.3, please provide a more thorough explanation of the underlying physics of multi-stage spraying and the cavitation combined method. Clarify how these methods address the limitations of traditional ultrasonic atomization.

 

Thank you for your comment. We have tried to expand the description of the basic physics of spraying methods. For multi-stage spraying we have added (p.9):

Primary droplets, produced at high rates, move with velocity under the influence of the ultrasonic field. Ultrasonic action causes successive droplet fragmentation each time they interact with a power antinode in the standing wave.

For the combined method we added (p.11):

Under the influence of excess pressure, the cavitating liquid flows out of the pressure hole in the form of large drops, inside which there are one or more cavitation bubbles. The higher the hydraulic pressure, the greater the flow rate and, accordingly, the spraying performance. Cavitation bubble collapse generates pressure pulses that expand the droplet until until the surface tension limit is reached, causing the large droplet to break up into smaller ones. The size of these fragments (new drops) depends significantly on the size of the cavitation bubbles, which, in turn, is determined by the parameters of the ultrasonic action.

The advantages of the methods were also described (p.11):

The proposed method has the following advantages:

• increased spraying performance, corresponding to hydraulic, vortex, etc. atomizers and significantly exceeding the performance of ultrasonic atomizers with similar technical parameters;
• production of small-diameter droplets facilitated by ultrasonic cavitation;
• droplet diameter, smaller than droplets created by hydraulic and vortex atomizers with similar pressures and flow rates;
• the possibility of using low-frequency ultrasonic vibrations to form small droplets (in known ultrasonic atomizers, to obtain droplets of a similar size, operating frequencies several times higher are required).

 

1. Results and Discussion Section:

• In Section 3.1, please expand the discussion of Figure 12. Analyze the differences in droplet size distribution between ultrasonic and hydraulic atomization. Explain the implications of these differences for disinfection effectiveness.

 

Added a corresponding explanation to the discussion of Figure 12:

Ultrasonic spraying produces higher droplet dispersion, increasing the contact surface area with microorganisms, enhancing disinfection efficiency, and reducing disinfectant usage. A narrower droplet size distribution ensures uniform surface coverage, preventing areas with excessive or insufficient disinfectant application, thereby improving disinfection quality and minimizing risks such as the formation of hazardous aerosol clouds.

 

• In Section 3.2, please provide more context for Figure 13. Explain the experimental setup and conditions in more detail. Discuss the significance of the observed droplet size reduction at different stages of the multi-stage spraying process.

At the beginning of section 3.1 we described in more detail the experimental setup and the means for measuring droplet dispersion:

All particle size measurements were conducted with a Malvern SprayTec particle analyzer. The analyzer operates on the principle of laser diffraction. The SprayTec analyzer measures particle dispersion at frequencies up to 10 kHz, within a range of 0.1 to 2000 μm. The laser beam of the particle analyzer was located at a distance of 50 mm from the end of the sprayer during measurements. Settled tap water was used as the sprayed liquid.

In section 3.2 we wrote more about the operating principles of the multi-stage ultrasonic atomizer.

Droplets are destroyed in a standing ultrasonic wave when passing through a series of antinodes (stages). The size reduction is maximum when passing through the first and second stages, then the reduction is not so significant. At the same time, by the third stage, the particle size distribution becomes narrower. As noted above, high dispersion and narrow particle size distribution are favorable conditions for effective disinfection. On the other hand, this method is not limited in productivity – it is determined by the productivity of the aerosol generation method supplied to the device input.

• In Section 3.3 (Figure 15), please label the axes clearly and include units. Discuss the relationship between ultrasound amplitude, hydraulic pressure, and droplet size in more detail. Explain the practical implications of these findings for optimizing disinfection protocols.

We have changed Figure 15, dividing it into two for different values. We have described the essence of the method in more detail above, in paragraph 2.2.2. We have added explanations after the figure.

To implement this method, it is important that the ultrasound amplitude be sufficient to create cavitation. For higher hydraulic pressure values, it turns out that such amplitude must be higher. When providing the cavitation spray mode, we obtain a truly fine aerosol, which is ideal for disinfection tasks. The higher the hydraulic pressure, the higher the ultrasound amplitude required to switch to the cavitation mode, and the higher the aerosol dispersion, as shown in Figure 15.

4. Other Figures: Please ensure a consistent style across all figures by using the same font size and style for all text.

• In Figure 2, please improve the clarity of this figure by using different colors or line styles to distinguish between the liquid spread and the channels. Add arrows to indicate the direction of liquid flow.

Thank you for your comment. We have changed the drawing according to your recommendations.

• In Figures 7 and 10, these schematic diagrams are helpful but could be improved with clearer labels and annotations. Consider using arrows to show the movement of droplets and the direction of forces.

Thank you for your comment. We have tried to correct the drawings. We hope they have become clearer.

 

1. Conclusions Section: To enhance the effectiveness of your conclusions, be more specific by summarizing the key findings of your study and their implications for the field of disinfection. Highlight the potential impact of your work on improving disinfection practices and public health. Reconnect your findings back to the research question and the advantages of your proposed methods. Additionally, discuss the potential limitations of your study and suggest directions for future research.

The Conclusions section has been rewritten in accordance with your comments.The new version is more specific, aligns with the research question, and highlights the study's contributions, implications, limitations, and potential future directions.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I have reviewed the revised manuscript and happy that the authors has addressed the reviewer comments and incorporated the provided suggestions. However, please consider some of my observations as follow

1.      I still question whether the paper is a review or an original article. The authors describe it as a hybrid, but I believe it should be classified as one or the other to avoid confusion for readers. This I leave to the journal and editor if they have option for publishing hybrid manuscript.

2.     Remove the bullet points from the introduction and make it a proper introduction. Read some literature for reference

3.     The authors has not addressed the methodology related comment. I suggest the author to provide a dedicated section for methodology and mention all the details how the data has been collected with proper references and according to the academic procedures and protocols.

4.     Additionally, I recommend that the authors proofread the manuscript before it is published online.

Thank you.

Author Response

1. I still question whether the paper is a review or an original article. The authors describe it as a hybrid, but I believe it should be classified as one or the other to avoid confusion for readers. This I leave to the journal and editor if they have option for publishing hybrid manuscript.

Apparently, you are right, and we just need to follow the standard form of the "original article". Then the subject of our research is ultrasonic nebulizers of various mechanisms of action (including our innovative recent development). Then, as you correctly noted, the Methodology section is absolutely necessary. In it, we will describe the methods of studying our ultrasonic nebulizers in detail.

2. Remove the bullet points from the introduction and make it a proper introduction. Read some literature for reference.

Done. Now this passage of the Introduction looks like this:

One of its key benefits is the ability to control droplet size by adjusting the frequency of ultrasonic vibrations, with droplet diameters ranging from 90 µm at 25 kHz to 10 µm at 200 kHz for water. This method is also highly energy-efficient, achieving fine atomization at lower energy costs compared to hydraulic and pneumatic systems. Additionally, ultrasonic atomization is compatible with a wide range of liquids, including those with varying viscosity, low surface tension, or complex compositions, such as disinfectants containing silver nanoparticles. This compatibility ensures uniform nanoparticle distribution within droplets and prevents agglomeration. Finally, ultrasonic atomization minimizes health and environmental risks by avoiding the production of hazardous ultrafine aerosol clouds and reducing waste from excessively large droplets, thus enhancing both safety and efficiency.

3. The authors has not addressed the methodology related comment. I suggest the author to provide a dedicated section for methodology and mention all the details how the data has been collected with proper references and according to the academic procedures and protocols.

We have added the Methodology section to describe the methods and measurement tools used in the description of ultrasonic nebulizers.

Thanks to the respected Reviewer, it really has become much clearer.

4. Additionally, I recommend that the authors proofread the manuscript before it is published online.

Thank you, we carefully proofread our text using a professional editor. We corrected a number of inaccuracies and errors.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Considerable improvements have been made in the revision. A final recommendation of a minor revision should allow the authors to convert the text in bullet points of lines 352-360, 480-491 and 499-504 into prose format.

Author Response

Considerable improvements have been made in the revision. A final recommendation of a minor revision should allow the authors to convert the text in bullet points of lines 352-360, 480-491 and 499-504 into prose format.

Thank you, we fixed it. We replaced the list text with plain text.

352-360:

The proposed method offers several notable advantages. It provides increased spraying performance comparable to hydraulic and vortex atomizers, while significantly surpassing the performance of conventional ultrasonic atomizers with similar technical specifications. Additionally, it facilitates the production of small-diameter droplets through ultrasonic cavitation, resulting in droplets smaller than those produced by hydraulic or vortex atomizers under similar pressure and flow rate conditions. Another benefit is the ability to use low-frequency ultrasonic vibrations to generate small droplets, whereas conventional ultrasonic atomizers require significantly higher frequencies to achieve similar results.

480-491:

This work makes several key contributions. It advances droplet 480-491 generation technology by enabling ultrasonic atomizers to precisely control droplet sizes, allowing customization for various disinfection needs, ranging from personal hygiene to large-scale applications. The developed systems also enhance compatibility, efficiently atomizing high-viscosity liquids and two-phase disinfectant solutions, including those with silver nanoparticles, while ensuring uniform application without agglomeration. Additionally, innovative atomizer designs were introduced, featuring enhanced performance, controlled droplet size, and improved efficiency. Finally, the approach offers significant environmental and health benefits by reducing aerosol exposure risks and optimizing disinfectant use, leading to safer and more sustainable disinfection practices.

499 – 504:

Future research should aim to enhance aerosol production rates by developing hybrid designs that combine ultrasonic and hydraulic mechanisms. It should also explore novel materials and geometries to improve the energy efficiency and overall performance of these systems. Another important direction is the creation of automated, adaptive systems that can adjust in real time to varying liquid properties and disinfection conditions. Addressing these challenges will enable ultrasonic spraying technologies to become a cornerstone of modern disinfection strategies, contributing to public health protection and supporting sustainable hygiene practices globally.

Author Response File: Author Response.pdf