Ludovic Keiser
A central focus of our research lies in the dynamics of fluid flow within vascular networks, with particular emphasis on plant xylem hydraulics under drought conditions. We investigate how air embolisms form and propagate in the vascular conduits of leaves, a process that can compromise water transport and ultimately lead to plant death.
To unravel this phenomenon, we develop biomimetic microfluidic models of xylem networks using soft, pervaporating PDMS channels. These systems replicate the hierarchical architecture and compliance of real veins and allow precise control over geometric and physical parameters. Through ultra-fast imaging, confocal microscopy, and interferometric pressure mapping, we reveal how embolisms propagate intermittently via a jerky, stop-and-go dynamics driven by elastocapillary effects at micrometric constrictions that mimic pit membranes.
In 2022, we established how a single constriction induces sudden embolism jumps due to nonlinear pressure build-up and release (Keiser et al., JFM 2022). Building on this, we demonstrated in 2024 how networks of constrictions generate hierarchical and intermittent embolism propagation, mirroring observations in real Adiantum leaves (Keiser et al., JRSI 2024). We recently extended this work by coupling real-time pressure measurements and channel deformations, shedding light on the interplay between capillarity, compliance, and hydrodynamic resistance in complex vascular structures (Gauci et al., arXiv 2024).
On the theoretical side, we have introduced minimal models to capture nonlinear feedback between internal pressure and front dynamics in compliant networks, revealing history-dependent behaviors that cannot be explained by local thresholds alone (Jami et al., arXiv 2025).
This interdisciplinary work, developed in close collaboration with plant physiologists, aims to provide quantitative insights into drought-induced hydraulic failure in leaves and inform traits-based predictions of plant vulnerability.
If you are interested in this subject — for a discussion, a collaboration, or for a job opportunity — do not hesitate to contact us.
We also investigate how interfacial phenomena in confined geometries can induce nonlinear transport behaviors, with implications for droplet microfluidics, sorting mechanisms, and porous media flows.
Our core interest lies in understanding how the motion of bubbles, droplets, or capsules is governed by tiny film interfaces—often mere microns thick. These films are sensitive to confinement and minute changes in geometry, giving rise to sharp transitions in velocity and morphology.
These investigations combine asymptotic theory, direct numerical simulations, and microfluidic experiments, aiming to understand and potentially harness nonlinear effects for on-chip functions like deformability-based sorting or passive valves.
I also explore how nonlinear friction at fluid interfaces can drive the spontaneous formation of patterns or even cause the blow-up and fragmentation of interfaces. In confined or highly anisotropic geometries, interfacial stresses — often localized in thin lubrication films, gutters or small menisci — can amplify perturbations and lead to complex, sometimes violent, instability dynamics.
In our group, we leverage such nonlinearities to uncover new interfacial phenomena. Examples include: