Mathieu Joanicot

Microfluidic bypass for efficient passive regulation of droplet traffic at a junction

We propose a simple design for microfabricated junctions that allows an equal and regular distribution of droplets between the two outlets of a T junction. It relies on establishing a connection between the two outlets shortly after the junction to provide short-time memory to the device and induce perfect alternation in the choice of the outlet. We experimentally demonstrate the benefits of this simple passive device by a direct comparison to junctions without bypasses.

In situ Raman imaging of interdiffusion in a microchannel

This letter presents an experimental setup to probe the interdiffusion of various miscible and nonreacting liquids. A Raman confocal microscope allows us to image the local concentrations of two coflowing liquids in a microchannel. These steady-state measurements provide precise quantitative information about the kinetics of the interdiffusion process. For all the pairs of fluids investigated, we found this process to follow a classical diffusive scaling law with a interdiffusion coefficient D that depends on both liquids.

Microevaporators for Kinetic Exploration of Phase Diagrams

We use pervaporation-based microfluidic devices to concentrate species in aqueous solutions with spatial and temporal control of the process. Using experiments and modeling, we quantitatively describe the advection-diffusion behavior of the concentration field of various solutions (electrolytes, colloids, etc.) and demonstrate the potential of these devices as universal tools for the kinetic exploration of the phases and textures that form upon concentration.

Processing of temperature field in chemical microreactors with infrared thermography

This work is devoted to the first analysis of temperature fields related to chemical microfluidic reactors. The heat transport around and inside a microchannel is both convective and diffusive with spatial distribution of source terms and strong conductive effects in the channel surrounding. With simplified assumptions, it is shown that Infrared thermography and processing methods of the temperature frames allow to estimate important fields for the chemical engineers, such as the heating source distribution of the chemical reaction along the channel. A validation experiment of a temperature field processing method is proposed with Joule effect as calibrated source term and non reactive fluids. From such previous experiment, a Peclet field is estimated and used in a further step in order to study an acid-base flow configuration

Un rheometre sur puce microfluidique

Nous avons mis au point un rheometre sur une puce microfluidique. Ce dispositif est base sur l’etude des ecoulements paralleles. Les valeurs mesurees pour des fluides newtoniens et non newtoniens sont en bon accord avec les mesures obtenues grâce a un rheometre classique. Ce dispositif permettra une approche haut debit des problemes de formulations.

Investigating Kinetics of Temperature-Dependent Processes Using Microfluidics

We have developed an original microfluidic system to study fast kinetics of temperature-dependent processes in an emulsion. Using flow focusing geometries, aqueous droplets are continuously formed in an oil flow. These droplets, acting as microreactors (100 nL), contain the solution to be investigated, and are formed at high temperature. They flow in a microchannel to a cooled area through a controlled temperature gradient (typically from 60 to 10°C in a few seconds). Along the microchannel, the distance being equivalent to the time thanks to the use of droplets, the kinetics of the process can be followed (from 10 to 300 s). In particular, the microdevice has been used to study the kinetics of crystal nucleation of a solute dispersed in water after a temperature quench.Copyright