In the context of climate change and increasing energy needs of the world population, the global interest for sustainable sources to produce energy is growing. One promising resource for biofuel production is microalgae, although their industrial use is limited by the lack of efficient harvesting techniques. Assisted flotation represents a promising harvesting technique that consists in air dispersed into microbubbles rising through a microalgae suspension. As a result, microalgae cells get attached to gaz-liquid interfaces and are carried out and accumulated on the surface, without being damaged. Flotation is thus a relatively rapid operation that needs low space, has moderate operational costs, and that could thus overcome the bottleneck of feasible microalgal biofuel production. However, the efficiency of this method is limited by the fact that the interaction between the bubbles and the cells is generally repulsive, due to the negative surface charge of the cells and the bubbles in water, and the low hydrophobicity of the algal cells. The goal of this project is to improve the efficiency of flotation, in order to better exploit the potential of the microalgal bioressource. Fundamental knowledge at the molecular and cellular scales will be acquired on the cell wall of microalgae and on the molecular mechanisms underlying its adhesion to gaz/liquid interfaces, using advanced force spectroscopy techniques such as optical tweezers and FluidFM technology. These data will then be further used to identify adhesive components promoting cell aggregation at the cells interface, and functionalize them at the surface of bubbles, thus improving flotation efficiency without altering the cells. Finally the overall evaluation of the efficiency of the functionalized bubbles for microalgae flotation will be evaluated and compared to other harvesting techniques. The results obtained in this project will allow to generate fundamental knowledge on the cell wall of microalgae and on the molecular mechanisms underlying their adhesion to gaz-liquid interfaces. These are not the only benefits of this project, as it will also provide a new technological solution to measure the interactions between fluid and biological interfaces, as well as a way to increase the efficiency of flotation process. Therefore, understanding the biophysics of microalgae flotation will open up new strategies to transform the microalgal biomass into 3rd generation biofuels.