High Pressure Microfluidics for Studying Supercritical Fluids Microflows Properties

The recent development of microfluidic devices offers several advantages over conventional macroscale processes: enhancement of mass and heat transfer, reproducibility, potential for sensor integration for in situ reaction monitoring, rapid screening of parameters, and low reagent consumption during optimization. Developing microreactors which are pressure & temperature resistant (e.g. 10 < p < 25 MPa and 0 < T < 300°C) is of great interest since it addresses part of the limitations of conventional microsystems, such as their limited number of compatible solvents and chemistries, and working conditions. Coupling these robust tools to the specific properties of supercritical fluids - SCFs (high diffusivity, gas-like viscosity, liquid-like densities) opens new ways for accessing expanded synthesis space and for characterizing and studying supercritical fluids processes, generally limited to the use of “blind” stainless steel devices We have developed microreactors that allow for characterizing supercritical fluids and multiphase (liquid/SCFs) flows within microchannels. High speed CCD camera visualization is used to observe and screen different flow regimes, typically from dripping to jetting (Figure 1). The obtained phase diagram can be tuned only by varying pressure and temperature, thanks to SCFs properties. Additionally, Confocal Raman Micro spectroscopy was used to obtain useful information about physical and chemical behavior of a supercritical reacting media during process optimization. Further applications of Supercritical Microfluidics flows approach will be presented for the synthesis and the process of nanomaterials.