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The present work is dedicated to the development of a lab-on-chip (LOC) device for water toxicity environmental analysis and more especially herbicide detection. The final goal is focused on the functional integration of three-electrode electrochemical microcells (ElecCell) and organic photodetectors (OPD) in order to perform simultaneously electrochemical and optical detection in the frame of algal metabolism monitoring. Considering three different algae, ie. Chlamydomonas reinhardtii, Pseudokirchneriella subcapitata and Chlorella vulgaris while dealing with photosynthesis, the multi-microsensor platform enables to measure the variations of microalgae fluorescence as well as oxygen production. It is applied to study the Diuron herbicide influences on algal metabolism, evidencing fluorescence enhancement and oxygen production inhibition for concentrations as low as few tens of nanomoles. These results are performed with unconcentrated and six time concentrated algae solutions respectively, to estimate the ability of this dual-sensor system to conduct measurements without any sample preparation. Thus, according to the obtained results, the proposed LOC device is fully adapted to the electrochemical/optical dual detection for on-site pollutant analysis, ie. without sample pre-treatment.

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The present work was dedicated to the development of a lab-on-chip device for water toxicity analysis and more particularly herbicide detection in water. It consists in a portable system for on-site detection composed of three-electrode electrochemical microcells, integrated on a fluidic platform constructed on a glass substrate. The final goal is to yield a system that gives the possibility of conducting double, complementary detection: electrochemical and optical and therefore all materials used for the fabrication of the lab-on-chip platform were selected in order to obtain a device compatible with optical technology. The basic detection principle consisted in electrochemically monitoring disturbances in metabolic photosynthetic activities of algae induced by the presence of Diuron herbicide. Algal response, evaluated through oxygen (O2) monitoring through photosynthesis was different for each herbicide concentration in the examined sample. A concentration-dependent inhibition effect of the herbicide on photosynthesis was demonstrated. Herbicide detection was achieved through a range (blank - 1 µM Diuron herbicide solution) covering the limit of maximum acceptable concentration imposed by Canadian government (0.64 µM), using a halogen white light source for the stimulation of algal photosynthetic apparatus. Superior sensitivity results (limit of detection of around 0.1 µM) were obtained with an organic light emitting diode (OLED), having an emission spectrum adapted to algal absorption spectrum and assembled on the final system.

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An autonomous electrochemical biosensor with three electrodes integrated on the same silicon chip dedicated to the detection of herbicides in water was fabricated by means of silicon-based microfabrication technology. Platinum (Pt), platinum black (Pt Bl), tungsten/tungsten oxide (W/WO3) and iridium oxide (Pt/IrO2) working ultramicroelectrodes were developed. Ag/AgCl and Pt electrodes were used as reference and counter-integrated electrodes respectively. Physical vapor deposition (PVD) and electrodeposition were used for thin film deposition. The ultramicroelectrodes were employed for the detection of O2, H2O2 and pH related ions H3O(+)/OH(-), species taking part in photosynthetic and metabolic activities of algae. By measuring the variations in consumption-production rates of these electroactive species by algae, the quantity of herbicides present at trace level in the solution can be estimated. Fabricated ultramicroelectrodes were electrochemically characterized and calibrated. Pt Black ultramicroelectrodes exhibited the greatest sensitivity regarding O2 and H2O2 detection while Pt/IrO2 ultramicroelectrodes were more sensitive for pH measurement compared to W/WO3 ultramicroelectrodes for pH measurement. Bioassays were then conducted to detect traces of Diuron herbicide in water samples by evaluating disturbances in photosynthetic and metabolic activities of algae caused by this herbicide.

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In this work, we report on ElecFET (Electrochemical Field Effect Transistor) devices potentially of interest for the detection of different molecules in solution. ElecFET are electrochemical microsensors in liquid phase, based on two elements: (i) a pH-sensitive chemical field effect transistor (pH-ChemFET) and (ii) a metallic microelectrode deposited around the sensitive gate. The coexistence of these two elements combines (i) potentiometric and (ii) amperometric detection effects at the microscale. Design, fabrication and experimental validation of ElecFETs based on silicon and polymer micro-technologies, are reported. We first demonstrate the detection of hydrogen peroxide (H(2)O(2)) in solution, showing a sensitivity of 5 mV/mM in the [10-100 mM] concentration range. The ElecFET concept is then extended to the detection of glucose and lactate in the [1-30 mM] and [1-6 mM] concentration range respectively. The sensitivities are between 2-6 mV/mM and 8-20 mV/mM respectively.

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Microfluidic devices are currently being used in many types of biochemical microsystems for liquid phase analysis in the frame of medical applications. This paper presents a new technique for the realization of microfluidic channels using SU-8, a commonly used epoxy-based negative photo-resist. These microchannels were fabricated by a single stepper UV-photolithography process. By changing the process parameters, e.g. the optical focus depth and the UV exposure dose, well-defined, covered microchannels with various dimensions and aspect ratios were realized and proven to be effective for the fluid transport by capillarity. This technique can easily be used for the fabrication of microfluidic devices in the microanalysis and lab-on-chip applications realm.

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Silicon oxynitride (SiO(X)N(Y)) thin films were deposited by plasma-enhanced chemical vapour deposition technique (PECVD) from silane (SiH4), nitrous oxide (N2O), ammonia (NH3) and nitrogen (N2) mixture. Spectroscopic ellipsometry (SE), in the range of wavelengths 450-900 nm, was used to define the film thickness and therefore the deposition rate, as well as the refractive index as a function of the N2O gaseous flow. While considering the (Si3N4, SiO2, H2 or void) heterogeneous mixture, Maxwell Garnett (MG) theory allows to fit the SE measurements and to define the volume fraction of the different phases. Finally, Rutherford Backscattering Spectrometry (RBS) results showed that x = O/Si ratio increases gradually with increasing the N2O flow, allowing the correlation of the SiO(X)N(Y) films main parameters.

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We developed silicon nitride cantilevers integrating a probe tip and a wave guide that is prolonged on the silicon holder with one or two guides. A micro-system is bonded to a photodetector. The resulting hybrid system enables us to obtain simultaneously topographic and optical near-field images. Examples of images obtained on a longitudinal cross-section of an optical fibre are shown.