NanoµLab (FR7.7)

The micro/nanofluidic facility at ISTO offers high-resolution imaging and metrology techniques for micro-nanofluidic experiments. The experimental platform is equipped with several microscopes, high-resolution cameras, flow controllers as well as temperature controllers. A Raman micro-spectrometer coupled with a high-resolution microscope (Fig. 1) is used to measure the Raman spectra of microscopic samples, in situ and in real-time, i.e. allowing to monitor the chemical evolution of a system at the sub-micrometer scale. Besides, the platform allows for high-resolution measurements of velocity fields, with a resolution of 1 µm vector grid, using micro-Particle Image Velocimetry (PIV) and tracking velocimetry techniques. In parallel, computational microfluidics also known as pore-scale modelling is developed.

Micro-nanofluidic devices, also called micromodels or Geological lab-on-a-chip are a two-dimensional representation of a porous medium that allows for direct visualization of flows, reactions, and transport mechanisms at the pore-scale. The samples under study are fluid inclusions (to study liquid-air, solid-liquid and solid-air interfaces) and micro-nanofluidics devices under very well-controlled environment.

Thanks to the platform we are studying geological porous media at the pore-scale with a focus on physico-chemical processes: fluid-rock interactions, interfacial processes, multiphase flow, dissolution/precipitation processes, phase changes. Pore-scale numerical modelling is used mostly to simulate flow and transport in images of the samples to characterize its continuum scale properties (e.g. permeability and reactive surface area). The fields of application are unlimited from volcanology, to water resources, to energy storage. Any study on the physico-chemical behavior of porous media addressed by measuring pore scale properties can be achieved.

The platform includes:

• Upright microscope Nikon Eclipse Ni-U coupled to an Andor Raman spectrometer Shamrock 500i with Newton CCD detector, excitation wavelength: 532nm.

• Upright microscope Leica DM 2500M

• Inverted microscope Nikon Eclipse Ti2-U

• sCMOS camera, Andor Neo 5.5 coupled with the microscopes.

• A wide range of objectives for the microscopes from X4 to X100 with various numerical apertures.

• Limkam heating-cooling stages: Memmert HPP108 environmental chamber, two RH-controlling thermostated water bath devices (Jubalo F32 and FP50).

• Syringe pump KD scientific legato 180.

• Elveflow OB1-MK3 flow controller (up to 8 bars) coupled with Microfluidic Flow Sensors (0.4 to 7 μL/min).

• Open source multiphase and reactive transport model packages.

Chemical room to prepare samples

The originality of our platform lies in the high-resolution measurements optically, dynamically, chemically, and in real time. For example, we were able to measure velocity fields induced by fluid-fluid interactions for a system analog to sCO₂/brine in porous formation using the micro-PIV setup [1]. Thanks to the platform, for the first time, we investigated experimentally the magnitude of the interfacial momentum transfer force for different flow conditions [1].

Our novel and unique "homemade" Raman micro-spectrometer coupled with the optical microscope offers the advantage of simultaneously having access to high-performance microscopic observation and local structural and chemical analysis at the micrometer scale by the recording of Raman spectra. In addition, ISTO benefits from the expertise of CEMHTI (UPR3079) on in-situ spectroscopy techniques.

Recently, we have shown that pore-scale modellling can help to correlate the hydrological conditions to the geochemical observations during experiments in a microfluidic flow-through reactor. Indeed, experimental pore-scale images were used to simulate the flow in the microfluidic reactor [2].

We offer support on analysis of Raman spectra, micro-PIV data and Computational Fluid Dynamics.

[1] Roman, S.; Soulaine, C. & Kovscek, A. R., Pore-scale visualization and characterization of viscous dissipation in porous media, Journal of Colloid and Interface Science, 2020, 558, 269 - 279

[2] Poonoosamy, J., Soulaine, C., Burmeister A., Deissmann, G., Bosbach D. & Roman, S., Microfluidic flow-through reactor and 3D Raman imaging for in situ assessment of mineral reactivity in porous and fractured porous media, Lab on a Chip, 2020, 20, 2562-2571