Extreme conditions, i.e. high pressures, high temperature (HP/HT) or harsh chemical environments are extremely difficult to study and to observe undisturbed in the field and to replicate in the laboratory. Yet, numerous industrial and environmental applications largely depend on the ability to process reactive media in a wide range of conditions or to characterize HP/HT environmental samples. For instance, the use of the deep geological underground for energy or waste storage, ocean and deep-sea studies and applications or space exploration science and industry necessitates to characterise thermodynamics, hydrodynamics and (bio)(geo)chemical effects under unconventional conditions. Other examples include the development of multi-steps chemical and material synthesis, which require either harsh chemical conditions or a HP/HT environment. In the field of HP and HT processes, several HP reactors (autoclave, batch stainless steel reactors), and observation cells (e.g. Diamond Anvil Cells) already enable work in controlled pressure and temperature conditions. Unfortunately, they lack in (i) design flexibility, (ii) reactive flows processes monitoring and most importantly (iii) optical access for in situ characterization.
Without these desirable properties, current devices limit the range of application fields and make extreme condition experimentation, complicated and perceived as restricted to specialists. The limitation is particularly acute in several research fields where fast-screening for the generation of large experimental databases. However, microfluidics is a key enabling technology (KET) that could offer alternative experimental solutions combining fast-screening for flow-based processes and in situ characterisation. Many industrial and academic research facilities have now integrated microfluidics as a standard tool with increased efficiency thanks to smaller sample volumes, faster turnaround times, and lower test costs. With the ability to provide process intensification at lower cost, the market of microfluidics has grown exponentially over the last 20 years. Formerly limited to the normal conditions of pressure and temperature, the use of microreactors was recently extended to a larger range of conditions thanks to mass-production of silicon-Pyrex and glass microfabrication technologies.
This recent development has attracted an amazing number of new users from untapped industrial and academic fields, including environmental applications: Geological underground use, petroleum industry, deep-sea research, geology, HP microbiology, flow processes, materials sciences, and space exploration. Nevertheless, commercially available microdevices can only reach conditions up to 100 bar and 300°C, do not provide optimal chemical inertness or do not exhibit the large range of transparency necessary for in situ analysis, thus limiting the development of cost-effective fast-screening in situ. Extending the range of microfluidics to HP/HT extreme experimental conditions could change its operating window to make microfluidics available for a wider range of applications for which no solution currently exist. One of the main caveat of commercially available polymer or glass-based microdevices is their small transparency range (300 < (nm) < 1500 for Pyrex) that prevent optical access for in-situ characterisation as well as their high reactivity to harsh chemicals.
The SALAMI project aims at opening the global microfluidics market to HP/HT extreme conditions and in-situ experimentation thanks to a new family of microfluidics devices based on inert and highly transparent sapphire and diamond chips. Sapphire and diamond are ideal materials for extreme conditions experimentation because of both their exceptional thermo-mechanical robustness and (bio)chemical inertness, as well as the large transparency window they exhibit. Thus, they provide microfluidic tools compatible with multiple spectroscopy characterization techniques (UV-Vis, FTIR, Raman, X-Rays).
SALAMI aims to develop a family of microfluidic devices based on the preliminary demonstration made by the PI during the course of his ERC BIG MAC project. These microfluidic reactors are highly disruptive because they are both uniquely transparent and resistant to harsh chemical conditions. SALAMI will extent the frontiers of microfluidics with market-ready extreme plug-and-play and user-friendly lab-on-a chip for lab-scale and field-based non-specialist applications. New fabrication techniques will be tested to reduce production costs and to broaden the choice of construction materials and geometries for tailored use in industry and academia to address the current limitations of commercially available microdevices, and also create opportunities in unexplored paths.
