Scientific background

Think of embryonic development as an out-of-equilibrium hydrodynamic problem: what makes a living material spontaneously flow in a sufficiently well-controlled manner to shape functional organs?

Embryonic tissues are composed of layers of cohesive cells which are reminiscent of classic air-liquid foams; yet, a foam at thermal equilibrium will not spontaneously flow. The origin of such time-reversal symmetry breaking lies in molecular motors, which break detailed balance by converting biochemical energy into forces. Recent work [ref. 1 & video] highlighted the role of motor-driven stochastic activity in a solid-to-fluid transition during the zebrafish embryonic development. But how can such molecular-motor forces scale up to generate flows at the embryonic scale?

To address such question, we will use a combination of analytical theories & numerical tools to predict under which conditions an active cellular material will flow (viscous response) or resist deformation (elastic response). Up to now, most cell-based material models assume that deviations from mechanical equilibrium are Boltzmann-distributed; however, we have recently shown that motor-driven active fluctuations can drive exotic features, reminiscent of a Casimir effects, which drastically deviate from expectations based on a Boltzmann-statistics [2].