My research focus on the mechanics and flow of complex materials between fluid and solid, such as particulate media (granular materials, yield-stress fluid, dense suspensions) or biological systems (plants).
Plants are sessile organisms without nerves. As such, they have developed specific mechanisms to carry information rapidly throughout their body in response to mechanical stimuli. Recently, it has been suggested that the first stage of this long-distance signaling could be the propagation of hydraulic signals induced by the mechanical deformation of the plant tissue (bending), but the physical origin of this hydro-mechanical coupling remains a conundrum. Here, we address this issue by combining experiments on natural tree branches and soft biomimetic beams with modeling. We reveal a generic non-linear mechanism responsible for the generation of hydraulic pulses induced by bending in poroelastic branches. Our study gives a physical basis for long-distance communication in plants based on fast hydraulic signals.
Louf et al, Proc. Natl. Acad. Sci. USA 114, 11034-11039 (2017) pdf
The sudden and severe increase in the viscosity of certain suspensions above an onset stress is one of the most spectacular phenomena observed in complex fluids. This shear thickening, which has major implications for industry, is a long-standing puzzle in soft-matter physics. Recently, a frictional transition was conjectured to cause this phenomenon. Using experimental concepts from granular physics, we provide direct evidence that such suspensions are frictionless under low confining pressure, which is key to understanding their shear-thickening behavior.
Clavaud et al, Proc. Natl. Acad. Sci. USA 114, 5147-5152 (2017) pdf
Gravity perception plays a key role in how plants develop and adapt to environmental changes. However, more than a century after the pioneering work of Darwin, little is known on the sensing mechanism. Using a centrifugal device combined with growth kinematics imaging, we show that shoot gravitropism is stimulated by sensing inclination not gravitational force or acceleration as previously believed.
Chauvet et al. Scientific Reports 6, 35431 (2016) pdf
Impacts in granular materials and dense suspensions have been extensively studied over the past decade, motivated by application in astrophysics, ballistics, or by the simple quest to understand their complex rheology. Here we show that impact dynamics in these systems critically depends on the coupling between the granular pile dilatancy and the interstitial fluid pressure generated by the impact, a mechanism relevant from dry powders to shear-thickening suspensions.
Jerome et al. Phys. Rev. Lett. 117, 098003 (2016) pdf