Thèse Technologies Microfluidiques Durables pour un Biocarburant Bas-Carbone Issu de Microalgues H/F Doctorat.Gouv.Fr

Établissement : Université de Toulouse École doctorale : MEGEP - Mécanique, Energétique, Génie civil, Procédés Laboratoire de recherche : ICA - Institut Clément Ader Direction de la thèse : Pascale MAGAUD ORCID 0000000163199457 Début de la thèse : 2027-09-01 Date limite de candidature : 2026-11-23T23:59:59 Les microalgues constituent une ressource renouvelable particulièrement prometteuse pour la production de biocarburants. Toutefois, leur culture demeure difficilement viable sur le plan économique en raison de la consommation énergétique élevée des photobioréacteurs conventionnels, nécessaire pour assurer une distribution homogène de la lumière, des échanges gazeux efficaces et un mélange suffisant du milieu de culture. La réduction de cette consommation énergétique constitue ainsi un enjeu majeur pour améliorer la viabilité économique et la durabilité environnementale de la production de microalgues.
Cette thèse vise à développer une plateforme microfluidique intégrée permettant la culture et la récolte en continu de microalgues Chlorella vulgaris, avec une consommation énergétique réduite. La plateforme reposera sur trois composantes complémentaires : un photobioréacteur miniaturisé, un dispositif microfluidique de tri et un système automatisé de suivi. En combinant fonctionnement continu, contrôle précis des conditions de culture et réduction de la consommation énergétique, cette approche vise à contribuer au développement de procédés de production de microalgues plus durables et économiquement viables.
Microfluidic systems offer strong potential for controlled irradiation operations. The rapid development of micro-photoreactors for the production of photo-induced microorganisms clearly illustrates this potential. Several micro-photoreactor designs for the production of photo-induced microorganisms have been reported in the literature, including the spiral tubular reactor developed by Aillet (Aillet et al., 2013, doi:10.1016/j.cep.2012.10.017). Building on this work, the miniaturized photobioreactor proposed in this project for microalgae cultivation will consist of a spiral channel with a rectangular cross-section.
Microfluidic technologies also offers innovative approaches for cell sorting (Abbas et al. 2014). Proof of concept studies have demonstrated the feasibility of sorting microalgae according to their lipid content using microfluidic systems based on electrophoretic separation (Han et al. 2019, doi:10.1039/C9LC00850K) or inertial focusing (Capet et al. 2026). Building on these approaches, we aim to develop a continuous microfluidic sorting device based on inertial focusing and/or acoustofluidic phenomena to selectively separate microalgae according to their lipid content. Coupling this sorting device with the miniaturized photobioreactor would enable the continuous harvesting of microalgae at the end of their growth phase, while allowing the remaining cells to be recycled into the photobioreactor for further cultivation. Such an integrated system could provide the basis for a continuous and resource-efficient microalgae production process.
Microalgae have long attracted interest for the production of phar maceutical compounds and high value nutrients. More recently, they have also emerged as a renewable feedstock for biofuel production, achieving a high biomass yield without requiring arable land or freshwater for their culture in comparison with traditional crops. Microalgae are currently cultivated in photobioreactors designed to continuously ensure the key conditions required for their growth, including uniform light and nutrient distribution, efficient gas exchange (CO and O), and temperature control within the optimal growth range. However, the high energy consumption associated with conventional photobioreactors leads to high operating costs, making commercial production of microalgae still largely unprofitable. Microfluidic technologies could help overcome this technological barrier. The high surface-to-volume ratio of microchannels enables efficient and homogeneous delivery of light and CO, while the low energy requirements associated with maintaining laminar flow make microfluidic systems particularly attractive for algal culture. The objective of this project is therefore to design and experimentally characterize a miniaturized photobioreactor for the cultivation of Chlorella vulgaris. The system will be designed with a view to parallelization, enabling multiple microfluidic cultivation units to be operated simultaneously in order to achieve large-scale microalgal production while maintaining the advantages of a controlled microscale environment. WP1 - First prototype sizing (Toulouse) : Numerical simulations using the commercial software ANSYS/FLUENT will be performed to optimize the geometry and dimensions of first photobioreactor and microalgae sorting device prototypes.
WP2 - Prototype fabrication (Toulouse) : The prototypes will be fabricated using xurography enabling rapide and cost-effective prototyping and iterative design. CO2-permeable PDMS sheets will be used to facilitate gas exchange while ensuring optical access for light delivery.
WP3 - Monitoring methods (Bologna) : Particle tracking and AI-based image processing methods will be developed to continously monitor biomass growth within the microphotobioreactor as well as to quantify the sorting efficiency of the microfluidic sorting device.
WP4 - Optimized prototype design and operating conditions (Bologna/Toulouse) : The optimal operating condition (light intensity, CO supply, flow rate) will be determined based on two key objectives : maximizing the algal growth rate while minimizing the energy required for fluid pumping. The photobioreactor and sorting device prototypes will then be adapted and optimized to operate under the identified conditions.