Cellulose microfluidics

Microfluidics is a fast-growing field due to numerous applications for the biological and chemical study of small liquid volumes. Nowadays, microfluidic chips are mainly made of plastics and silicone. In order to reduce the use of petrol-based materials, paper-based microfluidics is an interesting alternative that was launched in 2007 with the ambition of developing low cost bio-medical testing devices. The principle lies in the imbibition of tracks made of blotting paper that serve as channels to convey fluids. These devices can be obtained either by delimiting hydrophobic barriers in the paper sheet structure by photolithography, inkjet printing or wax printing, or by cutting fine paper strips and enclosing them in between two transparent adhesives layers. The major drawback of such techniques is that the liquids are transported through the inter-fibre pore spaces rather than in channels with well-defined dimensions. This can hinder the circulation of fluids and sometimes alter the relevancy of the results when it comes to bio medical testing.

The idea of this project is to use microfibrillated cellulose (MFC) to produce 100% cellulose made microfluidic chips with real channels directly stamped in the material. The device would consist of two MFC films, the one being embossed to create channels, to other one being laminated over the first one to seal the microfluidic circuit.

MFC films were proven dense and impermeable which would enable to retain liquids over time inside the device. Moreover, MFC films are permeable to gases, a property that could be exploited for the development of atmospheric sensors for instance.

Besides the production of microfluidic MFC chips to validate the process, the properties of the obtained material are studied in the project, in particular the kinetics of vapour fluxes through the layers, in order to evaluate the rate of liquid loss due to evaporation. This step involves the mathematical modelling of the diffusion kinetics through the MFCs.