Microfluidic experiments allow a precise control and a direct visualization of flows, reactions and transport mechanisms at the microscale. Microfluidic devices are being used increasingly in the field of geosciences, engineering, biology, and medicine.
Because of the complexity and heterogeneity of large-scale systems, a mechanistic understanding of the processes at small scales is often needed to further develop integrated predictive modeling approaches from the micro to the macroscale. Moreover, the equations of continuum (large) scale models should be rooted in a correct description of pore scale processes.
I am using microfluidic experiments to:
- get new insights into microscale processes and propose new modeling approaches,
- to compare experimental results with numerical models that are in development,
- to upscale the results at the macroscale.
I couple microfluidic experiments with high resolution imaging techniques and numerical simulations to understand complex fluids microdynamics. My research cuts across different domains: to understand blood flows in the microcirculation, to measure ionic currents through carbon nanotubes for selective ion transport, and to improve the knowledge of the pore-scale processes associated with the sequestration of CO2 into the subsurface.
Multiphase and reactive transport in porous media: microfluidics experiments
My research aims at understand the underlying physics in multi-phase flow in porous media. I am currently focusing on the experimental study of immiscible two-phase flow in two-dimensional etched-silicon micromodels. The inherent instabilities existing in two-phase flows play a key role, especially in the processes of EOR or CO2 geological sequestration. In particular, a quantitative study of the morphology of the instabilities and of the velocity fields of the fluids in the vicinity of the interfaces is needed. For that purpose, we use image processing methods and PIV (Particle Image Velocimetry) measurements. This experimental work is compared with numerical simulations.
I am interested in understanding and quantifying trapping mechanisms during the process of CO2 sequestration, for that I investigated snap-off mechanims by comparing numerical simulations and experiments.
Single phase flow in sandstone micromodel
fluid: water seeded with microparticles
Micro-PIV measurements (Particle Image Velocimetry): exact velocity distribution at the pore-scale
Two-phase flows in sandstone micromodel
We investigate flow instabilities during two-phase flows in porous media. Micro-PIV measurements allow us to get new insights onto fluid flow velocity fields at the pore-scale.
Flow of Red Blood Cells in microchannels
My PhD research dealt with the study of blood flows in the cerebral microcirculation, which have implication in various pathologies impacting the microvascular architecture: hypertension, diabetes, Alzheimer, cancer... In the microcirculation, vessel sizes are similar to the size of a red blood cell. Thus, the dynamics of blood flows is particular at this scale. At microvascular bifurcations, a non homogeneous distribution of red blood cells and plasma is observed. This research attempts to clarify these distribution mechanisms. A microfluidic device has been developed in order to investigate flows of concentrated suspension of red blood cells. I first studied the metrological aspects specific to concentrated suspensions. Thus, various techniques have been developed and validated for the measurement of velocity fields, concentration and flow rates. In particular the dual-slit technique allows the measurement of red blood cells velocity profiles in microchannels with high resolution and accuracy (Roman et al, Microvasc. Res., 2012). With the dual-slit technique we are now able to measure the slip velocity of red blood cells at channel walls, which is not possible with micro-PIV techniques. The techniques developed now allow to explore different regimes depending on the size of the microchannels and to perform a parametric study of the phase separation effect at microvascular bifurcations.
In particular, this work has brought methodological protocols for the study of biological objects in microfluidics and quantitative results on the dynamics of blood flows. Movies here
Flow of Red Blood Cells at a microbifurcation
Microdevices integrating individual carbon nanotube
Nanofluidics is the study of fluids confined into structures for which the dimensions are in the order of the size of large biomolecules such as proteins or DNA. This is also the size of the electrical double layer present on each surface immersed in an aqueous solution. There is an interest in developing a wide range of devices that will benefit from the unique behavior of liquids under confinement. We are especially interested in the study of the confinement of ionic bio-channels inside a carbon nanotube for selective ion transport. For that purpose, we develop a microfluidic device incorporating carbon nanotubes. At the same time, the confinement of ionic bio-channels inside carbon nanotube is investigated. This microdevice will allow the characterization of the ion transport through carbon nanotubes with and without incorporated ionic bio-channels.