Labs on a Chip for Chemistry. Principles and Characteristics

The concept of labs-on-a-chip dates back to the early 1990s, but developments have been teeming and shaking up the biotech sector since the 2000s, as evidenced by the evolution in the number of articles whose subject contains the keyword "microfluidics", which refers to both the science and design of labs-on-a-chip and at least one of whose characteristic dimensions is of the order of a few tens of micrometers, in the Thomson ISI Web of Knowledge database. This number of articles has risen from 28 in 1998 to over 2,200 in 2017 alone (survey conducted in July 2018). Since then, labs-on-a-chip have become ubiquitous in many fields: in medicine, energy, green chemistry, cosmetics, the food industry..., but what are the real benefits of this technology for chemistry? What are their specific features? How are they developed?

Microfluidics has attracted the interest of the chemical industry, motivated largely by applications in analysis, synthesis and process intensification. For example, such downscaling is relevant in the nuclear field, or for industries manufacturing toxic or explosive products, as it would enable :

• Reduce waste production (reagents, laboratory consumables, decontamination solution, etc.);

• automate unit operations in chemical processes;

• reduce radiological and chemical exposure of personnel ;

• reduce costs (e.g. by transferring analyses from shielded enclosures to glove boxes).

Mainly used in the physico-chemistry of complex fluids on systems operating in near-ambient conditions, microfluidics is also of interest for conducting experiments under more severe conditions (high pressure, high temperature), representative of the industrial operating conditions encountered in various applications, ranging from oil exploration/production, through refining and petrochemicals, to biomass processing, biofuel synthesis...

This paradigm shift in organic chemistry is helping to improve :

• productivity ;

• selectivity. For reactions carried out in a two-phase medium, the absence of mixing is exploited at the end of the reaction: the product extraction and purification stage is eliminated, and the products are located exclusively in one of the two phases.

• thermal control linked to the surface/volume ratio and the possibility of positioning sensors as close as possible to the reaction;

• risk management.

High-throughput screening of operating conditions is also of interest to chemists in all fields. This...