Design keys for paper-based concentration gradient generators

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

Journal of Chromatography A

Elsevier BV

Lugar: Amsterdam; Año: 2018

0021-9673

The generation of concentration gradients is an essential operation for several analytical processes implemented on microfluidic paper-based analytical devices. The dynamic gradient formation is based on the transverse dispersion of chemical species across co-flowing streams. In paper channels, this transverse flux of molecules is dominated by mechanical dispersion, which is substantially different than molecular diffusion, which is the mechanism acting in conventional microchannels. Therefore, the design of gradient generators on paper requires strategies different from those used in traditional microfluidics. This work considers the foundations of transverse dispersion in porous substrates to investigate the optimal design of microfluidic paper-based concentration gradient generators (uPGGs) by computer simulations. A set of novel and versatile uPGGs were designed in the format of numerical prototypes. Then virtual experiments were run to explore the ranges of operation and the overall performance of such devices. Finally, some basic design rules for the easy fabrication of physical prototypes are proposed. Apart from optimizing mixers, diluters and uPGGs, the results of this investigation are relevant to attain highly controlled concentration fields on paper-based devices.