Y. Fouillet, R. Den Dulk, O. Fuchs, F. Boizot, M. Menneteau, F. Navarro
Keywords: microfluidics, digital microfluidics, lab on a chip
Summary:Companion diagnostics are an indispensable part of personalized medicine, providing information that is essential for the safe and effective use of a corresponding therapeutic drug. Such devices need to be robust, transportable and easy to use. Depending on the application, the bio-fluidic protocol can be complex with multiple operations in series and in parallel. This paper reports an automated platform using a digital microfluidic approach in order to ease the integration of such complex protocols. As an example application, we have integrated a commercial diagnostic kit (PLT VASP/P2Y12®, Diagnostica Stago, Biocytex, Asnières, France), which is used for monitoring patients under the administration of anti-coagulation drugs by measuring the platelet responsiveness to ADP via the P2Y12 platelet receptor. Starting from a 15 µL sample of whole blood, the kit runs 3 tests in parallel, each consisting of four mixing and incubation steps and one dilution step. Finally, the result is quantified by a flow cytometry. The integration of the fluidic protocol requires a combination of elementary functions such as volume dispensing, splitting, successive mixing and dilution. A challenge for the integration of the VASP assay is that the fluidic system needs to manage different reaction volumes (5, 10, 15, 20 and 200 µL) in the same disposable fluidic cartridge. This has been achieved by defining collapsible chambers using a hyper-elastic silicone membrane that is inserted between a fluidic layer and a pneumatic layer. The thin membrane is pneumatically deformed to fill and empty the chambers completely. Elementary volumes of fluid can thus flow between adjacent chambers through a small channel by switching the pneumatic pressure under the chambers (Figure1). The instrument contains no wetted parts because all fluidic operations are performed by pneumatic actuation only. Furthermore, thanks to the high elasticity of the membrane, the required pressure for the actuation can be very low, which allows the pneumatic system to be miniaturized easily. All the elementary fluidic operations shown in Figure 2 were studied by observation of fluorescently dyed water and then successfully validated with blood and reagents. The fluidic architecture shown in Figure 3 contains 5 inlet wells that are manually filled with sample and reagents. Excellent reproducibility (CV < 3%) of dispensing operation from the wells was evaluated by fluorescence imaging. Volume displacement from chamber to chamber, mixing and dilution operations appear to be very fast because of the hemispherical shape of the chamber combined with the use of a hyper-elastic membranes that allow a short pneumatic response. First experiments with VASP protocol (Figure 4) will be presented and advantages of our approach compared to other digital microfluidic technologies such as EWOD  or PDMS  will be discussed.  Y. Fouillet and J. L. Achard, C. R. Phys., 2004, 5.  E.C. Jensen, A.M. Stockto,, T.N. Chiesl, J.Kim, A. Bera and A. Mathies, Lab Chip, 2013, 13 288-296.