Flows for Algae Growth: Uncovering the multi-scale dynamics of living suspensions

ongoing

Photosynthetic microalgae hold promise for the sustainable production of high-value products, bioplastics and biofuels. In bioreactors, suspensions of living, soft, and motile cells form an entirely new kind of fluids, which physiologically respond to the environment and the flow conditions. Fundamental knowledge of the flow dynamics of living suspensions is now urgently needed to develop new flow technologies for bioreactors. This project lays out an ambitious multi-scale experimental plan to establish the foundations of the fluid dynamics of living suspensions by revisiting three textbook aspects of flow: (1) turbulence, (2) the dynamics at solid and free interfaces and (3) the response to shear. This endeavour faces a new paradigm in complex flows, where fluid dynamics and cell physiology on different length scales, are deeply entwined. I will tackle this problem with a unique set of multi-scale experiments combining advanced flow diagnostics and rheology tools with new microfluidics and 3-D cell tracking recently developed in my group. These experiments will yield the first tracking measurements of living microalgae in a turbulent flow, and reveal what happens when motile cells on the small scale meet the turbulence cascade. Tracking experiments will provide new insight into the interactions of microalgae with free and textured surfaces, and, combined with rheology, show how shear flow affects cell motility and inversely how motility affects the response to shear of the suspension. Together, these experiments will uncover the interrelations between flow, cell physiology and growth, and determine how cell motility can be leveraged to optimize the turbulent mixing conditions in bioreactors, avoid biofilm formation and mediate cell harvesting.