Rapid and even spreading of complex fluids over a large area in porous substrates

Rapid and even spreading of complex fluids over a large area on substrates like paper is required for chemical and biological sensing applications. Non-Newtonian flow behaviour and presence of multi-phase components poses a significant challenge to uniform flow in porous media. Specially in case of blood, for bio-sensing applications, fast spread on a large area is required to avoid coagulation and non-uniform component spread.
In this work we have developed a filter paper based device to resolve this spreading challenge. We sandwich the filter paper between a matrix of nanofibrous membrane backed by polyethylene terephatalate (PET) sheets, forming a multi-scale pore network: one within the filter paper and the other between the PET sheet and the filter paper. By doing so, we decrease the overall resistance to flow while maintaining the same capillary suction pressure to obtain a quick, uniform spread of dyed liquids, milk solutions and whole blood. The device design and concepts used here can be used in paper microfluidic applications and to develop devices for Dried Blood Spot analysis that utilize this fast flow while maintaining even spreading over a large area.