Sandwich device ensures rapid and even spreading of biofluids for analysis

Biological fluids, such as blood, exhibit non-Newtonian flow behavior, which makes them difficult to be distributed quickly and evenly for use in sensing applications. Many methods of overcoming this problem rely on altering the fluid properties, impacting the results of diagnostic and pharmaceutical studies. Agrawal et al. developed a microfluidic device capable of evenly and quickly pumping liquids onto filter papers for analysis.

The authors created a three-layer sandwich design, which consists of a filter paper and a cellulose sheet separated by a nanofiber mesh. The mesh was prepared by electrospinning a polymer solution of porcine gelatin and a biocompatible polyester, creating a network of materials that enhances capillary pumping. A careful arrangement of pore sizes enables changes in pressure that create a suction force, driving the fluid toward the filter paper at higher speeds than the paper can achieve on its own.

In testing the device’s effectiveness on water, blood samples and a milk solution, the group found an increase in permeability in their device compared to the native filter paper, as well as a more uniform spreading for the non-Newtonian liquid samples.

“With the above design, whole blood – irrespective of its hematocrit volume – can be used in any lateral flow diagnostic devices,” said author Prasoon Kumar.

The group hopes their proposed technique can be incorporated into current immunoassay testing kits to improve sensitivity and enhance flow at a low cost. The device’s ability to ensure even spreading can also enhance the reliability of dried blood spot analyses, which are used widely in the pharmaceutical industry.

Source: “Rapid and even spreading of complex fluids over a large area in porous substrates,” by Prashant Agrawal, Hemant Kumar, and Prasoon Kumar, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0019939 .