Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dopamine, as a biology molecule, plays significant role in keeping health. In this work, the authors systematically investigated the effect of 3D print parameters on the sensor performance. The work should be improved before acceptance.

For sensors, the selectivity toward target molecule is important. Shall the author investigate this effect.

The response time should be provided.

The stability of the sensor should be given. Could it be reused after several days or months?

Author Response

 Reply latter

 

Review 1

 

For sensors, the selectivity toward target molecule is important. Shall the author investigate this effect.

 

Thank you for your comments and suggestions. The selectivity toward a specific target molecule was not investigated in this study, as the main objective was not the development of a selective dopamine sensor, but rather to demonstrate that the investigation and optimization of 3D printing parameters are essential to improve the performance of 3D-printed electrochemical devices. Instead, different electroactive molecules were evaluated to demonstrate the electrochemical response and the potential applicability of the proposed 3D-printed PLA/CB device for electroanalytical purposes. A systematic investigation of selectivity, including interference studies and applications in complex matrices, will be addressed in future studies.

 

The response time should be provided.

 

Thank you for your comments and suggestions. In the present study, the main objective was to investigate the influence of 3D printing parameters on the electrochemical performance of PLA/CB electrodes. Therefore, the response time of the device was not evaluated, as this parameter is more directly related to specific sensing applications and measurement conditions. The investigation of response time will be addressed in future studies focused on the application of the device to specific electroanalytical targets.

 

The stability of the sensor should be given. Could it be reuse after several days or months?

 

Thank you for your comments and suggestions. The long-term stability and reusability of the sensor over several days or months were not evaluated in the present study, as the main objective was to investigate the influence of 3D printing parameters on the electrochemical performance of the PLA/CB electrodes. The assessment of temporal stability and reuse is strongly dependent on the optimization of post-printing surface treatments and electrode activation procedures, which are currently under investigation. Therefore, a systematic stability study will be addressed in a subsequent stage of this work and in future studies.

 

Review 2

 

The title should be revised to reflect the content

 

Thank you for your comments and suggestions. The title has been revised to describe the work better. We emphasize that the proposed study focuses on evaluating the influence of FDM 3D printing parameters on the development of electrochemical sensors. The applications of the electrodes will be highlighted in subsequent studies.

 

More discussions about the experimental results should be added in the content

 

Thank you for your comments and suggestions. The manuscript was carefully revised, and additional discussion of the experimental results was incorporated throughout the text.

 

How about the usage of other kinds of conductive filament as the electrode materials?

 

Thank you for your comments and suggestions. The use of different types of conductive filaments is an important aspect that may significantly influence the electrochemical performance of 3D-printed electrodes. In the present study, a PLA/carbon black (PLA/CB) filament was selected because it is a conductive material currently available in our laboratory and is widely used in the literature, allowing a more direct comparison with previously reported results. It is important to emphasize that the main objective of this study was to investigate the influence of 3D printing parameters on the electrochemical behavior of printed sensors, rather than to compare different conductive materials. Therefore, to maintain a controlled and consistent evaluation of the printing-related effects, the composition of the conductive filament was kept constant throughout the study. Nevertheless, we fully agree with the reviewer that extending this investigation to other conductive filaments, such as graphene-based materials or customdeveloped filaments, is highly relevant. Ongoing studies in our research group are focused on evaluating alternative commercial conductive filaments, including graphene-based systems, and developing laboratory-made conductive filaments. These studies will allow for a deeper understanding of the combined effects of material composition and printing parameters on electrochemical performance and will be the subject of future publications.

 

How about the applications to other typical electroative model, such as metal ions?

 

Thank you for your comments and suggestions. In the present study, the main focus was to evaluate the effect of 3D printing parameters on the electrochemical performance of PLA/CB electrodes. Therefore, applications involving other electroactive models, such as metal ions, were not investigated. The evaluation of

 

the proposed device for different classes of analytes, including metal ions, will be addressed in future studies focused on specific applications.

 

Review 3

 

What percentage of the prints are filled?

 

Thank you for your comments and suggestions. The information was inserted in section 2.3.

 

Did the authors evaluate different impression orientations? Some authors have observed that this is also a parameter that affects the conductivity and resistivity of the sensors.

 

Thank you for your comments and suggestions. Several studies have reported that printing orientation may affect the conductivity and resistivity of printed sensors owing to variations in interlayer contact and filament alignment. In the present study, different printing orientations were not evaluated. The electrodes were fabricated using vertical printing orientation, following the methodology previously reported by Patel et al., which has been widely adopted in the literature. This choice was made to ensure reproducibility and consistency with the established fabrication protocols. It is important to emphasize that the main objective of this study was to investigate the influence of 3D printing parameters that are more likely to vary between different printing systems and setups, such as printing temperature, layer height, and printing speed. In contrast, the printing orientation was kept constant because it is a user-defined parameter that can be easily controlled and reproduced across different equipment.

 

The authors present the discussion in terms of area resistivity (kΩ cm2), but do not provide the electroactive areas of the sensors. I recommended presenting is this data, as well as the cyclic voltammograms of the redox probe used.

 

Thank you for your comments and suggestions. In the present study, the electroactive surface areas were not calculated for each of the printing parameters investigated. This choice was made because the main objective of this work was to propose and validate a fully 3D-printed electrochemical device and to demonstrate that the optimization of printing parameters is essential to improve the overall electrochemical performance of the device, particularly in terms of charge transfer behavior. Studies focused on surface treatment and activation strategies are currently under evaluation, and these approaches will allow a more reliable determination of the electroactive area, which will be addressed in future work.

 

Regarding the cyclic voltammograms of the redox probe, these data have now been included in the manuscript. A new subsection was added in which the cyclic voltammetric responses of the [Fe(CN)₆]³⁻/⁴⁻ redox probe are presented and

 

discussed in detail, providing additional insight into the electrochemical behavior of the proposed sensor.

 

In other works involving 3D-printed devices, it is common to observe polishing on sandpaper with a smaller grain size, and the authors used only 320 grit? Doesn’t that give a surface that’s too rought?

 

Thank you for your comments and suggestions. We agree that polishing using only 320-grit sandpaper results in a surface that is excessively rough and highly scratched. In the revised procedure, the polishing step was optimized by employing a sequential polishing process using 320-grit sandpaper followed by 1200-grit sandpaper. While the 320 grit was used to remove surface irregularities and ensure electrode exposure, the subsequent polishing with 1200 grit significantly reduced surface roughness and improved surface homogeneity. This optimized polishing protocol has now been clarified and inserted into the experimental section of the manuscript.

 

In line 198, the authors should correct the linear range of the analytical curve of dopamine (0.5 – 100 uM).

 

Thank you for your comments and suggestions. The values for the linear response range have been corrected in the text.

 

In other works reported in literature, it is evident that designs similar to the one used by the authors can affect electrical resistance (10.1021/acs.analchem.4c02127, 10.1016/j.electacta.2023.142166). Conductive tracks that are too long increase resistance, affecting the electrochemical profile of the redox probe. Have the authors observed similar phenomena? Have you tested other designs? I recommended discussing these issues in the basis of these articles.

 

Thank you for your comments and suggestions. We fully agree that the length of the

 

conductive path strongly influences electrical resistance and, consequently, the electrochemical response of 3D-printed sensors, as reported in the cited studies. In our experiments, we observed that conductive paths longer than approximately 15 mm lead to increased resistance and affect the redox probe response, in agreement with the literature. However, a systematic evaluation of different conductive track lengths and electrode designs was not performed due to limitations of the electrochemical cell configuration, which is not suitable for shorter conductive paths. Therefore, the electrode geometry was kept constant to ensure reproducible and reliable measurements. Despite these constraints, the conductive path length used in this work provides an adequate electrochemical response, comparable to similar studies. A more comprehensive investigation of electrode design effects will be addressed in future studies. 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This is an interesting paper dealing with the 3D printing of electrode and its application in electrochemical sensing with dopamine as the model. Various printing parameters have been checked to prove the electrochemical performances, and the  optimal conditions were selected. The paper can be accepted for publication with major revision.

1. The title should be revised to reflect the content.
2. More discussions about the experimental results should be added in the content.
3. How about the usage of other kinds of conductive filaments as the electrode materials?
4. How about the applications to other typical electroactive model, such as metal ions?

Author Response

 Reply latter

 

Review 1

 

For sensors, the selectivity toward target molecule is important. Shall the author investigate this effect.

 

Thank you for your comments and suggestions. The selectivity toward a specific target molecule was not investigated in this study, as the main objective was not the development of a selective dopamine sensor, but rather to demonstrate that the investigation and optimization of 3D printing parameters are essential to improve the performance of 3D-printed electrochemical devices. Instead, different electroactive molecules were evaluated to demonstrate the electrochemical response and the potential applicability of the proposed 3D-printed PLA/CB device for electroanalytical purposes. A systematic investigation of selectivity, including interference studies and applications in complex matrices, will be addressed in future studies.

 

The response time should be provided.

 

Thank you for your comments and suggestions. In the present study, the main objective was to investigate the influence of 3D printing parameters on the electrochemical performance of PLA/CB electrodes. Therefore, the response time of the device was not evaluated, as this parameter is more directly related to specific sensing applications and measurement conditions. The investigation of response time will be addressed in future studies focused on the application of the device to specific electroanalytical targets.

 

The stability of the sensor should be given. Could it be reuse after several days or months?

 

Thank you for your comments and suggestions. The long-term stability and reusability of the sensor over several days or months were not evaluated in the present study, as the main objective was to investigate the influence of 3D printing parameters on the electrochemical performance of the PLA/CB electrodes. The assessment of temporal stability and reuse is strongly dependent on the optimization of post-printing surface treatments and electrode activation procedures, which are currently under investigation. Therefore, a systematic stability study will be addressed in a subsequent stage of this work and in future studies.

 

Review 2

 

The title should be revised to reflect the content

 

Thank you for your comments and suggestions. The title has been revised to describe the work better. We emphasize that the proposed study focuses on evaluating the influence of FDM 3D printing parameters on the development of electrochemical sensors. The applications of the electrodes will be highlighted in subsequent studies.

 

More discussions about the experimental results should be added in the content

 

Thank you for your comments and suggestions. The manuscript was carefully revised, and additional discussion of the experimental results was incorporated throughout the text.

 

How about the usage of other kinds of conductive filament as the electrode materials?

 

Thank you for your comments and suggestions. The use of different types of conductive filaments is an important aspect that may significantly influence the electrochemical performance of 3D-printed electrodes. In the present study, a PLA/carbon black (PLA/CB) filament was selected because it is a conductive material currently available in our laboratory and is widely used in the literature, allowing a more direct comparison with previously reported results. It is important to emphasize that the main objective of this study was to investigate the influence of 3D printing parameters on the electrochemical behavior of printed sensors, rather than to compare different conductive materials. Therefore, to maintain a controlled and consistent evaluation of the printing-related effects, the composition of the conductive filament was kept constant throughout the study. Nevertheless, we fully agree with the reviewer that extending this investigation to other conductive filaments, such as graphene-based materials or customdeveloped filaments, is highly relevant. Ongoing studies in our research group are focused on evaluating alternative commercial conductive filaments, including graphene-based systems, and developing laboratory-made conductive filaments. These studies will allow for a deeper understanding of the combined effects of material composition and printing parameters on electrochemical performance and will be the subject of future publications.

 

How about the applications to other typical electroative model, such as metal ions?

 

Thank you for your comments and suggestions. In the present study, the main focus was to evaluate the effect of 3D printing parameters on the electrochemical performance of PLA/CB electrodes. Therefore, applications involving other electroactive models, such as metal ions, were not investigated. The evaluation of

 

the proposed device for different classes of analytes, including metal ions, will be addressed in future studies focused on specific applications.

 

Review 3

 

What percentage of the prints are filled?

 

Thank you for your comments and suggestions. The information was inserted in section 2.3.

 

Did the authors evaluate different impression orientations? Some authors have observed that this is also a parameter that affects the conductivity and resistivity of the sensors.

 

Thank you for your comments and suggestions. Several studies have reported that printing orientation may affect the conductivity and resistivity of printed sensors owing to variations in interlayer contact and filament alignment. In the present study, different printing orientations were not evaluated. The electrodes were fabricated using vertical printing orientation, following the methodology previously reported by Patel et al., which has been widely adopted in the literature. This choice was made to ensure reproducibility and consistency with the established fabrication protocols. It is important to emphasize that the main objective of this study was to investigate the influence of 3D printing parameters that are more likely to vary between different printing systems and setups, such as printing temperature, layer height, and printing speed. In contrast, the printing orientation was kept constant because it is a user-defined parameter that can be easily controlled and reproduced across different equipment.

 

The authors present the discussion in terms of area resistivity (kΩ cm2), but do not provide the electroactive areas of the sensors. I recommended presenting is this data, as well as the cyclic voltammograms of the redox probe used.

 

Thank you for your comments and suggestions. In the present study, the electroactive surface areas were not calculated for each of the printing parameters investigated. This choice was made because the main objective of this work was to propose and validate a fully 3D-printed electrochemical device and to demonstrate that the optimization of printing parameters is essential to improve the overall electrochemical performance of the device, particularly in terms of charge transfer behavior. Studies focused on surface treatment and activation strategies are currently under evaluation, and these approaches will allow a more reliable determination of the electroactive area, which will be addressed in future work.

 

Regarding the cyclic voltammograms of the redox probe, these data have now been included in the manuscript. A new subsection was added in which the cyclic voltammetric responses of the [Fe(CN)₆]³⁻/⁴⁻ redox probe are presented and

 

discussed in detail, providing additional insight into the electrochemical behavior of the proposed sensor.

 

In other works involving 3D-printed devices, it is common to observe polishing on sandpaper with a smaller grain size, and the authors used only 320 grit? Doesn’t that give a surface that’s too rought?

 

Thank you for your comments and suggestions. We agree that polishing using only 320-grit sandpaper results in a surface that is excessively rough and highly scratched. In the revised procedure, the polishing step was optimized by employing a sequential polishing process using 320-grit sandpaper followed by 1200-grit sandpaper. While the 320 grit was used to remove surface irregularities and ensure electrode exposure, the subsequent polishing with 1200 grit significantly reduced surface roughness and improved surface homogeneity. This optimized polishing protocol has now been clarified and inserted into the experimental section of the manuscript.

 

In line 198, the authors should correct the linear range of the analytical curve of dopamine (0.5 – 100 uM).

 

Thank you for your comments and suggestions. The values for the linear response range have been corrected in the text.

 

In other works reported in literature, it is evident that designs similar to the one used by the authors can affect electrical resistance (10.1021/acs.analchem.4c02127, 10.1016/j.electacta.2023.142166). Conductive tracks that are too long increase resistance, affecting the electrochemical profile of the redox probe. Have the authors observed similar phenomena? Have you tested other designs? I recommended discussing these issues in the basis of these articles.

 

Thank you for your comments and suggestions. We fully agree that the length of the

 

conductive path strongly influences electrical resistance and, consequently, the electrochemical response of 3D-printed sensors, as reported in the cited studies. In our experiments, we observed that conductive paths longer than approximately 15 mm lead to increased resistance and affect the redox probe response, in agreement with the literature. However, a systematic evaluation of different conductive track lengths and electrode designs was not performed due to limitations of the electrochemical cell configuration, which is not suitable for shorter conductive paths. Therefore, the electrode geometry was kept constant to ensure reproducible and reliable measurements. Despite these constraints, the conductive path length used in this work provides an adequate electrochemical response, comparable to similar studies. A more comprehensive investigation of electrode design effects will be addressed in future studies. 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The “Critical Role of 3D Printing Parameters in the Performance of Electrochemical Sensors” manuscript presents an interesting research design considering the influence of printing parameters for 3D electrochemical sensors. Some points could be improved and answered, such as:

1. What percentage of the prints are filled?
2. Did the authors evaluate different impression orientations? Some authors have observed that this is also a parameter that affects the conductivity and resistivity of the sensors.
3. The authors present the discussion in terms of area resistivity (kΩ cm2), but do not provide the electroactive areas of the sensors. I recommend presenting this data, as well as the cyclic voltammograms of the redox probe used.
4. In other works involving 3D-printed devices, it is common to observe polishing on sandpaper with a smaller grain size, and the authors used only 320 grit? Doesn't that give a surface that's too rough?
5. In line 198, the authors should correct the linear range of the analytical curve for dopamine (0.5-100 µM).
6. In other works reported in the literature, it is evident that designs similar to the one used by the authors can affect electrical resistance (10.1021/acs.analchem.4c02127, 10.1016/j.electacta.2023.142166). Conductive tracks that are too long increase resistance, affecting the electrochemical profile of the redox probe. Have the authors observed similar phenomena? Have you tested other designs? I recommend discussing these issues on the basis of these articles.

Author Response

 Reply latter

 

Review 1

 

For sensors, the selectivity toward target molecule is important. Shall the author investigate this effect.

 

Thank you for your comments and suggestions. The selectivity toward a specific target molecule was not investigated in this study, as the main objective was not the development of a selective dopamine sensor, but rather to demonstrate that the investigation and optimization of 3D printing parameters are essential to improve the performance of 3D-printed electrochemical devices. Instead, different electroactive molecules were evaluated to demonstrate the electrochemical response and the potential applicability of the proposed 3D-printed PLA/CB device for electroanalytical purposes. A systematic investigation of selectivity, including interference studies and applications in complex matrices, will be addressed in future studies.

 

The response time should be provided.

 

Thank you for your comments and suggestions. In the present study, the main objective was to investigate the influence of 3D printing parameters on the electrochemical performance of PLA/CB electrodes. Therefore, the response time of the device was not evaluated, as this parameter is more directly related to specific sensing applications and measurement conditions. The investigation of response time will be addressed in future studies focused on the application of the device to specific electroanalytical targets.

 

The stability of the sensor should be given. Could it be reuse after several days or months?

 

Thank you for your comments and suggestions. The long-term stability and reusability of the sensor over several days or months were not evaluated in the present study, as the main objective was to investigate the influence of 3D printing parameters on the electrochemical performance of the PLA/CB electrodes. The assessment of temporal stability and reuse is strongly dependent on the optimization of post-printing surface treatments and electrode activation procedures, which are currently under investigation. Therefore, a systematic stability study will be addressed in a subsequent stage of this work and in future studies.

 

Review 2

 

The title should be revised to reflect the content

 

Thank you for your comments and suggestions. The title has been revised to describe the work better. We emphasize that the proposed study focuses on evaluating the influence of FDM 3D printing parameters on the development of electrochemical sensors. The applications of the electrodes will be highlighted in subsequent studies.

 

More discussions about the experimental results should be added in the content

 

Thank you for your comments and suggestions. The manuscript was carefully revised, and additional discussion of the experimental results was incorporated throughout the text.

 

How about the usage of other kinds of conductive filament as the electrode materials?

 

Thank you for your comments and suggestions. The use of different types of conductive filaments is an important aspect that may significantly influence the electrochemical performance of 3D-printed electrodes. In the present study, a PLA/carbon black (PLA/CB) filament was selected because it is a conductive material currently available in our laboratory and is widely used in the literature, allowing a more direct comparison with previously reported results. It is important to emphasize that the main objective of this study was to investigate the influence of 3D printing parameters on the electrochemical behavior of printed sensors, rather than to compare different conductive materials. Therefore, to maintain a controlled and consistent evaluation of the printing-related effects, the composition of the conductive filament was kept constant throughout the study. Nevertheless, we fully agree with the reviewer that extending this investigation to other conductive filaments, such as graphene-based materials or customdeveloped filaments, is highly relevant. Ongoing studies in our research group are focused on evaluating alternative commercial conductive filaments, including graphene-based systems, and developing laboratory-made conductive filaments. These studies will allow for a deeper understanding of the combined effects of material composition and printing parameters on electrochemical performance and will be the subject of future publications.

 

How about the applications to other typical electroative model, such as metal ions?

 

Thank you for your comments and suggestions. In the present study, the main focus was to evaluate the effect of 3D printing parameters on the electrochemical performance of PLA/CB electrodes. Therefore, applications involving other electroactive models, such as metal ions, were not investigated. The evaluation of

 

the proposed device for different classes of analytes, including metal ions, will be addressed in future studies focused on specific applications.

 

Review 3

 

What percentage of the prints are filled?

 

Thank you for your comments and suggestions. The information was inserted in section 2.3.

 

Did the authors evaluate different impression orientations? Some authors have observed that this is also a parameter that affects the conductivity and resistivity of the sensors.

 

Thank you for your comments and suggestions. Several studies have reported that printing orientation may affect the conductivity and resistivity of printed sensors owing to variations in interlayer contact and filament alignment. In the present study, different printing orientations were not evaluated. The electrodes were fabricated using vertical printing orientation, following the methodology previously reported by Patel et al., which has been widely adopted in the literature. This choice was made to ensure reproducibility and consistency with the established fabrication protocols. It is important to emphasize that the main objective of this study was to investigate the influence of 3D printing parameters that are more likely to vary between different printing systems and setups, such as printing temperature, layer height, and printing speed. In contrast, the printing orientation was kept constant because it is a user-defined parameter that can be easily controlled and reproduced across different equipment.

 

The authors present the discussion in terms of area resistivity (kΩ cm2), but do not provide the electroactive areas of the sensors. I recommended presenting is this data, as well as the cyclic voltammograms of the redox probe used.

 

Thank you for your comments and suggestions. In the present study, the electroactive surface areas were not calculated for each of the printing parameters investigated. This choice was made because the main objective of this work was to propose and validate a fully 3D-printed electrochemical device and to demonstrate that the optimization of printing parameters is essential to improve the overall electrochemical performance of the device, particularly in terms of charge transfer behavior. Studies focused on surface treatment and activation strategies are currently under evaluation, and these approaches will allow a more reliable determination of the electroactive area, which will be addressed in future work.

 

Regarding the cyclic voltammograms of the redox probe, these data have now been included in the manuscript. A new subsection was added in which the cyclic voltammetric responses of the [Fe(CN)₆]³⁻/⁴⁻ redox probe are presented and

 

discussed in detail, providing additional insight into the electrochemical behavior of the proposed sensor.

 

In other works involving 3D-printed devices, it is common to observe polishing on sandpaper with a smaller grain size, and the authors used only 320 grit? Doesn’t that give a surface that’s too rought?

 

Thank you for your comments and suggestions. We agree that polishing using only 320-grit sandpaper results in a surface that is excessively rough and highly scratched. In the revised procedure, the polishing step was optimized by employing a sequential polishing process using 320-grit sandpaper followed by 1200-grit sandpaper. While the 320 grit was used to remove surface irregularities and ensure electrode exposure, the subsequent polishing with 1200 grit significantly reduced surface roughness and improved surface homogeneity. This optimized polishing protocol has now been clarified and inserted into the experimental section of the manuscript.

 

In line 198, the authors should correct the linear range of the analytical curve of dopamine (0.5 – 100 uM).

 

Thank you for your comments and suggestions. The values for the linear response range have been corrected in the text.

 

In other works reported in literature, it is evident that designs similar to the one used by the authors can affect electrical resistance (10.1021/acs.analchem.4c02127, 10.1016/j.electacta.2023.142166). Conductive tracks that are too long increase resistance, affecting the electrochemical profile of the redox probe. Have the authors observed similar phenomena? Have you tested other designs? I recommended discussing these issues in the basis of these articles.

 

Thank you for your comments and suggestions. We fully agree that the length of the

 

conductive path strongly influences electrical resistance and, consequently, the electrochemical response of 3D-printed sensors, as reported in the cited studies. In our experiments, we observed that conductive paths longer than approximately 15 mm lead to increased resistance and affect the redox probe response, in agreement with the literature. However, a systematic evaluation of different conductive track lengths and electrode designs was not performed due to limitations of the electrochemical cell configuration, which is not suitable for shorter conductive paths. Therefore, the electrode geometry was kept constant to ensure reproducible and reliable measurements. Despite these constraints, the conductive path length used in this work provides an adequate electrochemical response, comparable to similar studies. A more comprehensive investigation of electrode design effects will be addressed in future studies. 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accept