Description du sujet de thèse

This thesis topic is part of the ANR CHROMIC project involving the PPSM and LuMIn laboratories at ENS Paris-Saclay. The aim of this project is to develop new microfluidic chips functionalised by mechanofluorochromic materials, i.e. materials whose fluorescence emission is sensitive to mechanical forces. The aim is then to use these new devices to measure the force exerted on a single microalga passing through the circuit and finally to link the force applied in the microfluidic circuit to the increase in the extraction yield of the compounds produced by the microalga. The PhD student recruited will be involved in the first three stages of the project. First, mechanofluorochromic coatings will be prepared from polydiacetylene-fluorophore dyads. Polydiacetylenes are a family of polymers known to change from a non-fluorescent blue phase to a weakly fluorescent red phase when mechanical force is applied to them. As part of this thesis work, the polydiacetylene will be coupled to a fluorophore that will be chosen to exhibit energy transfer with the blue phase of the polydiacetylene only, which will lead to a mechanofluorochromic response with better contrast. Several types of fluorophores will be evaluated, with criteria including ease of synthesis, sensitivity to mechanical forces, brightness and biocompatibility. In addition, different types of grafting will be explored to obtain thin layers on the surface of glass or PDMS. In a second step, the response of these mechanofluorochromic coatings to friction forces will be calibrated using an AFM coupled to a fluorescence microscope: the AFM tip used in contact mode allows a variable and controlled force to be applied, and the associated variation in fluorescence emission is recorded simultaneously. In a third step, the grafting reaction will be adapted and optimised to functionalise the interior of microfluidic channels with multiple size restrictions: when microalgae pass through the restrictions, they exert a frictional force on the channel walls, triggering the mechanofluorochromic reaction. The grafting will be optimised to enable efficient, parallelised fluorescence detection of the passage of microalgae. The ultimate goal will be to correlate the measurements taken on the microalgae with those taken by AFM coupled with fluorescence microscopy. This thesis topic is thus part of the development of a completely new approach to measuring forces at the single-cell level.

Contexte de travail

This PhD thesis is part of a funded ANR project, CHROMIC, that implies PPSM and LuMIn laboratories in ENS Paris-Saclay

Contraintes et risques

chemical risk