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The findings presented in this paper demonstrate the effectiveness of a new method for analyzing the electroacoustic response of Love wave acoustic sensors to assess the mechanical and dielectric properties of liquid samples. The Love wave sensor was modified by applying a solution of extracellular polymeric substances (EPS) using a self-assembled monolayer technique. The mechanical parameters of the EPS-modified sensors, such as insertion losses and phase, were found to be slightly affected by turbidity, even at high levels, while allowing a chemical detection by mass loading effect. On the other hand, the sensor electrical parameters such as capacitance and resistance showed a positive correlation with increasing turbidity. The experimental chemical detection also showed changes in the mechanical parameters (wave amplitude and phase) of the EPS-modified sensor in response to different concentrations of mercury (Hg 2+ ), ranging from 10E−10 M to 10E−2 M. Furthermore, the study utilized response surface methodology to analyze the nonlinear behavior of the sensor under combined factors of turbidity and mercury concentration. Through this approach, a mathematical model was developed to simulate measurements of capacitance and resistance, considering both turbidity and mercury concentration as variables. This study demonstrated that integrating an EPS-Love wave sensor enables the simultaneous detection of mercury concentration and assessment of water turbidity via changes in capacitance and resistance, underscoring the sensor’s promise for high-performance environmental monitoring.

The present study aimed to develop and characterize new heavy metal sensors functionalized by extracellular polymeric substances (EPSs) isolated from a Tunisian thermophilic microalga strain Graesiella sp. The elaborated sensor showed a highly homogeneous character and revealed a microstructural lamellar arrangement, high crystalline nature, and several functional groups. Electrochemical impedance spectroscopy (EIS) and acoustic wave sensing were used as sensing techniques to explore the ability of microalgae-EPS-functionalized sensors to detect cadmium and mercury as heavy metals. For impedimetric measurements, a two-dipole circuit was adopted and showed good-fitted results with a low total error. The acoustic sensor platforms showed good compatibility with EPS in adjacent water. For both EPS-functionalized sensors, metal ions (Cd2+, Hg2+) were successfully detected in the concentration range from 10−10 M to 10−4 M. Impedimetric sensor was more sensitive to Cd2+ at low concentrations before saturation at 10−7 M, while the acoustic sensor exhibited more sensitivity to Hg2+ over the full range. The results highlight a new potential alternative to use microalgae EPSs as a sensitive coating material for the detection of heavy metals. However, its use in a real liquid medium requires further investigation of its selectivity in the presence of other compounds.

This paper presents an extended work on the Finite Element Method (FEM) simulation of Love Wave (LW) sensors in a liquid medium. Two models are proposed to simulate the multiphysical response of the sensor. Both are extensively described in terms of principle, composition and behavior, making their applications easily reproducible by the sensor community. The first model is a Representative Volume Element (RVE) simulating the transducer and the second focuses on the sensor’s longitudinal (OXZ) cut which simulates the multiphysical responses of the device. Sensitivity of the LW device to variations in the rheological and dielectric properties of liquids is estimated and then compared to a large set of measurements issued from LW sensors presenting different technological characteristics. This integral approach allows for a deeper insight into the multiphysical behavior of the LW sensor. This article also explores the advantages and drawbacks of each model. Both are in good accordance with the measurements and could be used for various applications, for which a non-exhaustive list is proposed in the conclusion.

This paper presents an experimental platform allowing in situ measurement in an aqueous medium using an acoustic Love wave sensor. The aim of this platform, which includes the sensor, a test cell for electrical connections, a microfluidic chip, and a readout electronic circuit, is to realize a first estimation of water quality without transportation of water samples from the field to the laboratory as a medium-term objective. In the first step, to validate the ability of such a platform to operate in the field and in Amazonian water, an isolated and difficult-to-access location, namely, the floodplain Logo Do Curuaï in the Brazilian Amazon, was chosen. The ability of such a platform to be transported, installed on site, and used is discussed in terms of user friendliness and versatility. The response of the Love wave sensor to in situ water samples is estimated according to the physical parameters of Amazonian water. Finally, the very good quality of the acoustic response is established, potential further improvements are discussed, and the paper is concluded.