Accelerated Life Tests for Time-Dependent Response Characterization of Functionalized Piezoelectric Microcantilever-Based Gas Sensors

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I have read the paper. It is very short and doesn’t seem to contain any electronics. It is a resonator sensor connected to a network analyzer, to which chemicals are added to shift the frequency. This isn’t an electronic nose as it requires an array of sensors, sampling system and pattern recognition to be considered such a device. There are no details on the device at all, the experimental method is very crude. It then has a couple of plots of frequency shift and a failure diagram. I don’t understand why it has been submitted to this journal.

Comments on the Quality of English Language

N/A

Author Response

Comment: I have read the paper. It is very short and doesn’t seem to contain any electronics. It is a resonator sensor connected to a network analyzer, to which chemicals are added to shift the frequency. This isn’t an electronic nose as it requires an array of sensors, sampling system and pattern recognition to be considered such a device. There are no details on the device at all, the experimental method is very crude. It then has a couple of plots of frequency shift and a failure diagram. I don’t understand why it has been submitted to this journal.

Response: Thank you for sharing your opinion. We appreciate your perspective. We acknowledge that the paper may not focus solely on electronics. However, it was submitted for the special issue "Electronic Nose: From Fundamental Research to Applications," which seeks original studies highlighting gas-sensing materials and electronic nose devices. The accelerated test study to characterize new gas-sensing materials for food applications aligns perfectly with the aims of this special issue. We hope you share this view.

We have also included a depiction of the schematics used in the electronic nose which forms the basis of this study.

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents a novel and comprehensive study on the application of accelerated life testing and Weibull analysis to characterize the performance and reliability of piezoelectric microcantilever-based gas sensors. The findings have significant implications for improving food freshness detection techniques. However, there are a few areas that require minor revisions to enhance clarity, reproducibility, and impact.

• 1. The introduction provides a solid background on the significance of food freshness detection. Expanding the section with more recent studies, especially those related to similar or competitive technologies in VOC detection, would enhance contextual understanding.

• 2. Provide more details about the PD-MC fabrication and functionalization process. This would help other researchers in replicating the study.
• 3. Justify the choice of cadaverine concentrations above the standard and how these relate to real-world scenarios.
• 4. Clarify the implications of the non-linear response behavior observed at high concentrations and how this impacts practical applications or sensor design.

Author Response

The manuscript presents a novel and comprehensive study on the application of accelerated life testing and Weibull analysis to characterize the performance and reliability of piezoelectric microcantilever-based gas sensors. The findings have significant implications for improving food freshness detection techniques. However, a few areas require minor revisions to enhance clarity, reproducibility, and impact.

1. The introduction provides a solid background on the significance of food freshness detection. Expanding the section with more recent studies, especially those related to similar or competitive technologies in VOC detection, would enhance contextual understanding.

 

Thank you for your comment. We have now included a section with applications of e-noses within food via VOC detection.

 

2. Provide more details about the PD-MC fabrication and functionalization process. This would help other researchers in replicating the study.

 

We have now included a section in the methodology part which describes the cantilever fabrication and the functionalization process.

 

3. Justify the choice of cadaverine concentrations above the standard and how these relate to real-world scenarios.

 

We have now included a section in the methodology explaining the concept of accelerated lifetime tests, and how they relate to real-world scenarios.

 

 

4. Clarify the implications of the non-linear response behavior observed at high concentrations and how this impacts practical applications or sensor design.

 

Since the concentration at which the response becomes nonlinear is above real-world scenarios, the device's performance is not compromised by the nonlinear behavior. We have added this sentence to the manuscript.

 

We have included the following section in the conclusion (lines 340-346):

It can, therefore, be inferred that the non-linear behavior observed at high concentrations undermines the proportional relationship between adsorption-dependent changes in resonance frequency. This adds complexity to accurately quantifying analyte concentrations. It is therefore crucial to operate the device below the established upper limits of detection or develop response models considering these non-linearities. This will further enhance sensor accuracy, as previously suggested in our studies.

Reviewer 3 Report

Comments and Suggestions for Authors

In the manuscript the authors analyse a method to use accelerated life test into a Weibull distribution analysis to extract the expected time to failure. The manuscript is not very clear in some parts and typos are present in the overall manuscript. 

Equation 2 is wrong (the value reported are not in accordance with those in the text) as well as the time extracted (the value calculated is different from the one reported).

Parameters and goodness of fit are not reported neither for weibull curves nor for the equation 2.

A validation of the values obtained by a real experiment should be provided. 

For the above reasons the manuscript should not be considered for publication and, in the case, a strongly modified version of the work should be resubmitted. 

 

Author Response

In the manuscript, the authors analyze a method for using accelerated life tests in a Weibull distribution analysis to extract the expected time to failure. The manuscript is not very clear in some parts, and typos are present in the overall manuscript.

Thank you for your comments. We have now corrected the typos and improved the text clarity.

Equation 2 is wrong (the values reported are not in accordance with those in the text), as well as the time extracted (the value calculated is different from the one reported).

You are so right. We have re-calculated and reported the correct values now.

Parameters and goodness of fit are not reported neither for weibull curves nor for the equation 2.

The goodness of fit to the Weibull 1-parameter was tested with the Kolmogorov-Smirnov method and found to be within the 95% confidence limits.

A validation of the values obtained by a real experiment should be provided.

The results were validated by exposing the sample to 33 mg/kg cadaverine concentration, and saturation happens after about 80 minutes, confirming the model trend. This information is now included in the manuscript.

For the above reasons the manuscript should not be considered for publication and, in the case, a strongly modified version of the work should be resubmitted.

We have now included the significant changes and hope you consider the manuscript for publication.

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

The reviewer appreciates the efforts in improving the manuscript and strengthening the reliability of the results obtained. There are two points that, in the reviewer's opinion, should be further improved.

1) in the case of electronic noses, sensor arrays are considered rather than single selective sensors since ORNs can be considered broad selective receptors. The analogy with artificial olfaction should be described better, especially considering the topic of collection.

2) A brief explanation about the method used to obtain the reference concentration samples should be included (How was the cadaverine concentration obtained? A full description of the procedure should be reported)

Author Response

Reviewer 1:

The reviewer appreciates the efforts in improving the manuscript and strengthening the reliability of the results obtained. There are two points that, in the reviewer's opinion, should be further improved.

Thank you for your comment. We have endeavored to provide adequate responses addressing the requested improvements.

 

1. In the case of electronic noses, sensor arrays are considered rather than single selective sensors since ORNs can be considered broad selective receptors. The analogy with artificial olfaction should be described better, especially considering the topic of collection.

We have now included in the introduction the following statement (Lines 70-75):

It is important to note that the measured concentration of cadaverine is influenced by the temperature, humidity, and microbial flora associated with its production. To address this, a humidity and temperature sensor has been integrated into the overall sensor system. However, this study primarily focuses on investigating the time-dependent response characteristics of the functionalized PD-MC sensor in measuring cadaverine.

We would also like to inform the reviewer that we have a multicantilever platform composed of 3 cantilevers, each functionalized with functional material tailored to specific volatile gas biomarkers of meat and fish freshness. In this regard, the Total Biogenic Amine count (TBA-count) i.e. a lumpsum estimated concentration of the different biogenic amines, is considered contrary to one i.e. cadaverine. Since tailoring of the functional material for the other bioamines is still underway, it will be reported in subsequent publications. Below is an image of the three multicantilever array system.

Fig.1.  Multicantilever platform comnposed of an array of  3 PD-MCs. Each is functionalised a tailored functional material for a VOC in meat and fish samples, thereby enabling the use of the Total Biogenic Amine count. This will in turn account for the broad selective nature of ORNs.

 

2. A brief explanation about the method used to obtain the reference concentration samples should be included (How was the cadaverine concentration obtained? A full description of the procedure should be reported)

We have included a brief and referenced procedure from our previous studies, detailing the determination of the correlation between synthetic cadaverine used and measured cadaverine concentration in mg/kg real meat and fish samples, in relation to the measured change in resonance frequency. This is detailed in lines 175-186.

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

the authors amended the manuscript that is now worth to be published in its current form