Mathematical model and numerical simulations for paper-based electromigrative separations

RAÚL URTEAGA; SCHAUMBURG, FEDERICO; KLER, PABLO A.; FRANCK, NICOLAS; BERLI, CLAUDIO L. A.

Córdoba

Congreso; II Brazil - Argentine Microfluidics Congress V Congreso de Microfluídica Argentina; 2019

Microfluidic paper-based analytical devices are nowadays a well established technology. Nevertheless, several aspects related to transport of chemical species in the porous substrate are still to be improved to reach higher levels of analytical precision, efficiency and portability. In this context, numerical simulations of fluid and mass transport in microfluidic paper-based analytical devices are essential for better understanding different phenomena that are relevant in this particular porous matrix. Among these transport phenomena, advective, diffusive and dispersive mechanisms have been already addressed in previous works. This work focuses on the electrophoretic transport of species and the fluid transport associated to electroosmotic flow in paper-based microfluidic devices. Consequently, we present a transport model for ionic and ionizable compounds under the effect of an externally applied electric field. The model includes the effects of porosity, tortuosity, and permeability of paper substrates on the fluxes of ionic compounds and the solvent velocity profile due to the electroosmotic flow. The model was implemented and validated with experimental data, and then tested with several numerical prototypes running different electrophoretic techniques for the separation of analytesof bioanalytical interest. Numerical prototypes were implemented using an upgrade of electroMicroTransport, an open source toolbox for the well known finite volume library OpenFOAM®. This upgraded version enables us to evaluate the effect of the parameters describing paper substrates (porosity, tortuosity, permeability and electrokinetic potential) on the transport of ionic species. The proposed model and the code upgrade for electroMicroTransport enabled us to numerically develop and test a novel paper-based device for detection of electrolytic risk for nephrolithiasis notably decreasing the developing time for arriving to a functional device. Finally, experimental results obtained with the developed device showed good qualitative agreement with numerical predictions, and, more important, effectively working as detector of electrolytic risk conditions for nephrolithiasis.