PhD Defense of Timothée ALLENET

 Development of an optofluidic micro-sensor for remote measurements of radionuclides
The use of nuclear energy for electricity production presents an important concern with radiotoxic waste management for present and future generations. In view of this fact, the chemists’ community has been searching for solutions to treat and recycle nuclear fuel. The miniaturization of chemical processes is extensively sought out nowerdays, in an attempt to reduce laboratory acivity risks, delays and costs. The researched analytical innovation requires subsequent development of appropriate analysis tools. In this respect, the work presented here addresses the development of co-integrated optofluidic micro-systems on borosilicate glass, compatible with nuclear effluent analysis constraints. A spectrometric sensor is designed, fabricated, interfaced and characterized in a nuclear environement. An optical waveguide and a microfluidic channel are designed adjacent to one another in order to obtain wide-spectrum absorption spectroscopy measurements by light/fluid evanescent interaction. Both ion-exchange technology and wet-etching technologies were used to create the optical and fluidic planar functions. The device is assembled by direct molecular bonding with an optimized protocole which withstands surface energies γ > 2,5 J/m². Sensor optical and fluidic functions are interfaced with fiber optics and fluid capillaries in order for the chip to be used within a “plug-and-play” detection chain. Spectral measurements of a plutonium(VI) in nitric acid solution have allowed to verify the technological solution’s compatibility with harsh acid manipulation and irradiation resistance. The system put together for the detection of plutonium(VI)  displays a detection limit of 1.6x10-2 mol/L for a probed volume below 1 nano-liter, inside a 21 micro-liter channel. A new sensor design is studied in the thesis work perspectives in order to optimize sensor detection limit and channel volume and reach industrial tools analytical performances with nano-liter sample volumes.