# Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology

Pierre Groc, Guy Cathébras, Vincent Kerzérho, Adrian Laborde, Fabien Soulier, Pierre Temple-Boyer, Jérôme Launay, Serge Bernard

<figure><img src="image_1.png" /></figure>

## To cite this version:

Pierre Groc, Guy Cathébras, Vincent Kerzérho, Adrian Laborde, Fabien Soulier, et al., Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology. Proceedings, 2024, 97 (1), pp.94. 10.3390/proceed-ings2024097094. lirmm-04612308

HAL Id: lirmm-04612308

https://hal-lirmm.ccsd.cnrs.fr/lirmm-04612308

Submitted on 14 Jun 2024

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology

Pierre Groc, Guy Cathébras, Vincent Kerzérho, Adrian Laborde, Fabien

Soulier, Pierre Temple-Boyer, Jérôme Launay, Serge Bernard

► To cite this version:

Pierre Groc, Guy Cathébras, Vincent Kerzérho, Adrian Laborde, Fabien Soulier, et al. Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology. Eurosensors XXXV, Sep 2023, Lecce, Italy. pp.94, 10.3390/proceedings2024097094. lirmm-04612308

HAL Id: lirmm-04612308

https://hal-lirmm.ccsd.cnrs.fr/lirmm-04612308v1

Submitted on 14 Jun 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_3.png" /></figure>

Abstract

# Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology †

Pierre Groc <fnref n="1" />, Guy Cathébras <fnref n="1" />, Vincent Kerzerho <fnref n="1" />, Adrian Laborde <fnref n="2" />, Fabien Soulier <fnref n="1" />, Pierre Temple-Boyer <fnref n="2" />, Jérôme Launay <fnref n="2" />,* and Serge Bernard <fnref n="1" />

**Abstract:** This work presents the design of a multisensor platform for the in situ monitoring of physico-chemical parameters in seawater. As a result, we propose an 8.5 × 8.5 mm<fnref n="2" /> silicon chip that integrates a MOSFET and two ISFETs (Metal Oxide Semiconductor and Ion-Sensitive Field-Effect Transistor) and four microelectrodes (two Ag electrodes and two Pt electrodes). The device allows measurements to be taken in liquid phase of temperature, pH, nitrate concentrations and conductivity. These silicon transducers could be integrated with conditioning electronics to achieve an autonomous environmental sensor device.

**Keywords:** ISFET sensor; multisensory; in situ

<figure><img src="image_4.png" /></figure>

check for
updates

**Citation:** Groc, P.; Cathébras, G.; Kerzerho, V.; Laborde, A.; Soulier, F.; Temple-Boyer, P.; Launay, J.; Bernard, S. Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology. *Proceedings 2024*, 97, 94. https://doi.org/10.3390/proceedings2024097094

Academic Editors: Pietro Siciliano and Luca Francioso

Published: 25 March 2024

<figure><img src="image_5.png" /></figure>

**Copyright:** © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## 1. Introduction

Knowledge of our oceans is limited, in particular by the lack of local measurement data, but also by the lack of global data that could help in our understanding of the relationship between biological variations and associated physico-chemical parameters. New methods of measurement and data processing have emerged, in particular with the explosion of deep learning and the use of satellite imagery for the extrapolation of surface measurements [1]. A large number of in situ measurement solutions have also been deployed, by increasing the number of measurement campaigns to cover large areas. However, these approaches are limited by cost and human effort. For example, autonomous measurement devices such as seabird probes [2] are efficient but expensive and require expert operators to deploy.

In this paper, we propose a system that combines integration and robustness for marine environments, allowing high-frequency and long-term measurements.

## 2. Materials and Methods

Our FET-based transducers were integrated into the 8.5 × 8.5 mm<fnref n="2" /> platform developed in silicon technology (Figure 1). Two IS-FETs (Figure 1, mark A) were designed to perform pH and ion-concentration measurements. To achieve these IS-FETs, we deposited specific fluoropolysiloxane-based ion-sensitive layers by drop-casting to deal with nitrate NO₃⁻ ion analysis. A MOSFET reference device (mark B) was also integrated for temperature-drift compensation. Finally, two silver/silver chloride (Ag/AgCl) pseudo-reference microelectrodes and two platinum (Pt) microelectrodes were also integrated (mark C). The Ag/AgCl electrodes were used as reference electrodes for the IS-FET gate voltage in the liquid phase, and the Pt electrodes were used for conductivity analysis and for impedance spectroscopy

<footnote n="1">¹ LIRMM, University of Montpellier, CNRS, 34095 Montpellier, France; pierre.groc@lirmm.fr (P.G.); guy.cathebras@lirmm.fr (G.C.); vincent.kerzerho@lirmm.fr (V.K.); fabien.soulier@lirmm.fr (F.S.); serge.bernard@lirmm.fr (S.B.)</footnote>

<footnote n="2">² LAAS-CNRS, 31400 Toulouse, France; adrian.laborde@laas.fr (A.L.); pierre.temple-boyer@laas.fr (P.T.-B.)</footnote>

<footnote>* Correspondence: jlaunay@laas.fr; Tel.: +335-61-33-68-09</footnote>

<footnote>† Presented at the XXXV EUROSENSORS Conference, Lecce, Italy, 10–13 September 2023.</footnote>
<figure><img src="image_2.png" /></figure>

Abstract

# Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology †

Pierre Groc <fnref n="1" />, Guy Cathébras <fnref n="1" />, Vincent Kerzerho <fnref n="1" />, Adrian Laborde <fnref n="2" />, Fabien Soulier <fnref n="1" />, Pierre Temple-Boyer <fnref n="2" />, Jérôme Launay <fnref n="2" />,* and Serge Bernard <fnref n="1" />

**Abstract:** This work presents the design of a multisensor platform for the in situ monitoring of physico-chemical parameters in seawater. As a result, we propose an 8.5 × 8.5 mm<fnref n="2" /> silicon chip that integrates a MOSFET and two ISFETs (Metal Oxide Semiconductor and Ion-Sensitive Field-Effect Transistor) and four microelectrodes (two Ag electrodes and two Pt electrodes). The device allows measurements to be taken in liquid phase of temperature, pH, nitrate concentrations and conductivity. These silicon transducers could be integrated with conditioning electronics to achieve an autonomous environmental sensor device.

**Keywords:** ISFET sensor; multisensory; in situ

<figure><img src="image_3.png" /></figure>

check for
updates

**Citation:** Groc, P.; Cathébras, G.; Kerzerho, V.; Laborde, A.; Soulier, F.; Temple-Boyer, P.; Launay, J.; Bernard, S. Multi-Micro-Sensor Platform for Monitoring Toxic Algal Blooms and Pollution in Coastal Marine Waters: Transducer Integration in Micro-Technology. *Proceedings 2024*, 97, 94. https://doi.org/10.3390/proceedings2024097094

Academic Editors: Pietro Siciliano and Luca Francioso

Published: 25 March 2024

<figure><img src="image_4.png" /></figure>

**Copyright:** © 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## 1. Introduction

Knowledge of our oceans is limited, in particular by the lack of local measurement data, but also by the lack of global data that could help in our understanding of the relationship between biological variations and associated physico-chemical parameters. New methods of measurement and data processing have emerged, in particular with the explosion of deep learning and the use of satellite imagery for the extrapolation of surface measurements [1]. A large number of in situ measurement solutions have also been deployed, by increasing the number of measurement campaigns to cover large areas. However, these approaches are limited by cost and human effort. For example, autonomous measurement devices such as seabird probes [2] are efficient but expensive and require expert operators to deploy.

In this paper, we propose a system that combines integration and robustness for marine environments, allowing high-frequency and long-term measurements.

## 2. Materials and Methods

Our FET-based transducers were integrated into the 8.5 × 8.5 mm<fnref n="2" /> platform developed in silicon technology (Figure 1). Two IS-FETs (Figure 1, mark A) were designed to perform pH and ion-concentration measurements. To achieve these IS-FETs, we deposited specific fluoropolysiloxane-based ion-sensitive layers by drop-casting to deal with nitrate NO₃⁻ ion analysis. A MOSFET reference device (mark B) was also integrated for temperature-drift compensation. Finally, two silver/silver chloride (Ag/AgCl) pseudo-reference microelectrodes and two platinum (Pt) microelectrodes were also integrated (mark C). The Ag/AgCl electrodes were used as reference electrodes for the IS-FET gate voltage in the liquid phase, and the Pt electrodes were used for conductivity analysis and for impedance spectroscopy

<footnote n="1">¹ LIRMM, University of Montpellier, CNRS, 34095 Montpellier, France; pierre.groc@lirmm.fr (P.G.); guy.cathebras@lirmm.fr (G.C.); vincent.kerzerho@lirmm.fr (V.K.); fabien.soulier@lirmm.fr (F.S.); serge.bernard@lirmm.fr (S.B.)</footnote>

<footnote n="2">² LAAS-CNRS, 31400 Toulouse, France; adrian.laborde@laas.fr (A.L.); pierre.temple-boyer@laas.fr (P.T.-B.)</footnote>

<footnote>* Correspondence: jlaunay@laas.fr; Tel.: +335-61-33-68-09</footnote>

<footnote>† Presented at the XXXV EUROSENSORS Conference, Lecce, Italy, 10–13 September 2023.</footnote>
in the liquid phase. The chip characteristics were measured with a parameter analyzer (HP 4142B).

<figure><img src="image_6.png" /><figcaption>**Figure 1.** Crab-chip with (A) ISFETs, (B) MOSFET, and (C) electrodes.</figcaption></figure>

**3. Results and Discussion**

The first results validated the fabrication process. We measured a MOSFET threshold voltage of 0.6 V, as expected. The MOSFET also had the expected temperature sensitivity of 0.22 mV/°C (Figure 2). This is very important because having a high sensitivity to temperature will allow the MOSFET to be used as a thermal compensator for pH measurements.

<figure><img src="image_7.png" /><figcaption>**Figure 2.** Temperature measurement with a MOSFET.</figcaption></figure>

For the IS-FET, we obtained a pH sensitivity of 46 mV per pH unit [3] (Figure 3). The curve for detecting the variation in nitrate concentration in a solution (Figure 4) gave a sensitivity estimated to 50 mV/pNO₃. In addition, these measurements were replicated on the same components, but also on components from other production series, or from the same series. These sensitivities will allow the easy detection of pH or nitrate in an aqueous solution, so that variations in these chemicals can be monitored.

<figure><img src="image_8.png" /><figcaption>**Figure 3.** pH measurement with an ISFET.</figcaption></figure>
in the liquid phase. The chip characteristics were measured with a parameter analyzer (HP 4142B).

<figure><img src="image_5.png" /><figcaption>**Figure 1.** Crab-chip with (A) ISFETs, (B) MOSFET, and (C) electrodes.</figcaption></figure>

**3. Results and Discussion**

The first results validated the fabrication process. We measured a MOSFET threshold voltage of 0.6 V, as expected. The MOSFET also had the expected temperature sensitivity of 0.22 mV/°C (Figure 2). This is very important because having a high sensitivity to temperature will allow the MOSFET to be used as a thermal compensator for pH measurements.

<figure><img src="image_6.png" /><figcaption>**Figure 2.** Temperature measurement with a MOSFET.</figcaption></figure>

For the IS-FET, we obtained a pH sensitivity of 46 mV per pH unit [3] (Figure 3). The curve for detecting the variation in nitrate concentration in a solution (Figure 4) gave a sensitivity estimated to 50 mV/pNO3. In addition, these measurements were replicated on the same components, but also on components from other production series, or from the same series. These sensitivities will allow the easy detection of pH or nitrate in an aqueous solution, so that variations in these chemicals can be monitored.

<figure><img src="image_7.png" /><figcaption>**Figure 3.** pH measurement with an ISFET.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Figure 4.** Measurement of nitrate concentration.</figcaption></figure>

**Author Contributions:** P.G. Conceptualization, methodology, validation, investigation, formal analysis, writing—original draft preparation. S.B. Conceptualization, supervision, writing, project administration, funding acquisition. J.L. Conceptualization, supervision, writing—review and editing. F.S. Conceptualization, supervision, writing—review and editing. V.K. Conceptualization, supervision, writing—review and editing. A.L. Technical support. P.T.-B. Conceptualization, supervision, writing—review and editing. G.C. Conceptualization. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by NUMEV, the University of Montpellier's Laboratory of Excellence. Grant numbers 2019-27-SOULIER and 2021-1-15 SOULIER.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available upon request from the corresponding author.

**Acknowledgments:** The technological realizations and associated research works were partly supported by the French RENATECH network.

**Conflicts of Interest:** The authors declare no conflicts of interest.

## References

1. Land Peter, E.; Shutler Jamie, D.; Findlay, H.; Girard-Ardhuin, F.; Sabia, R.; Reul, N.; Piolle, J.-F.; Chapron, B.; Quilfen, Y.; Salisbury, J.E.; et al. Salinity from Space Unlocks Satellite-Based Assessment of Ocean Acidification. *Environ. Sci. Technol.* **2015**, *49*, 1987–1994. [CrossRef] [PubMed]

2. Seabird Pobes. Available online: https://www.seabird.com/ph-sensors/sbe-18-ph-sensor/family?productCategoryId=54627869929 (accessed on 28 March 2023).

3. Miao, Y.; Guan, J.; Chen, J. Ion sensitive field effect transducer-based biosensors. *Biotechnol. Adv.* **2003**, *21*, 527–534.

**Disclaimer/Publisher's Note:** The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.
<figure><img src="image_8.png" /><figcaption>**Figure 4.** Measurement of nitrate concentration.</figcaption></figure>

**Author Contributions:** P.G. Conceptualization, methodology, validation, investigation, formal analysis, writing—original draft preparation. S.B. Conceptualization, supervision, writing, project administration, funding acquisition. J.L. Conceptualization, supervision, writing—review and editing. F.S. Conceptualization, supervision, writing—review and editing. V.K. Conceptualization, supervision, writing—review and editing. A.L. Technical support. P.T.-B. Conceptualization, supervision, writing—review and editing. G.C. Conceptualization. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by NUMEV, the University of Montpellier's Laboratory of Excellence. Grant numbers 2019-27-SOULIER and 2021-1-15 SOULIER.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available upon request from the corresponding author.

**Acknowledgments:** The technological realizations and associated research works were partly supported by the French RENATECH network.

**Conflicts of Interest:** The authors declare no conflicts of interest.

## References

1. Land Peter, E.; Shutler Jamie, D.; Findlay, H.; Girard-Ardhuin, F.; Sabia, R.; Reul, N.; Piolle, J.-F.; Chapron, B.; Quilfen, Y.; Salisbury, J.E.; et al. Salinity from Space Unlocks Satellite-Based Assessment of Ocean Acidification. *Environ. Sci. Technol.* **2015**, *49*, 1987–1994. [CrossRef] [PubMed]

2. Seabird Pobes. Available online: https://www.seabird.com/ph-sensors/sbe-18-ph-sensor/family?productCategoryId=54627869929 (accessed on 28 March 2023).

3. Miao, Y.; Guan, J.; Chen, J. Ion sensitive field effect transducer-based biosensors. *Biotechnol. Adv.* **2003**, *21*, 527–534.

**Disclaimer/Publisher's Note:** The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.