This is a major upgrade to the field of microfluidics, in which we expand the field to include microsystems fabricated with porous media in which fluid motion is driven by capillarity. The pores can be on the micrometer or the nanometer scale. The porous media may be natural (e.g., paper), synthetic (e.g., nitrocellulose membranes), or microfabricated (e.g., post arrays).
This 3D rendering is of a conceptual design for a "Microfluidics 2.0" device that conducts a multi-step chemical assay. A two-dimensional network of porous channels directs different reagents across a detection region that is imaged through a lens cast into the device casing. To conduct the test, a user adds the fluid sample to one of the channels, and then submerges the four channel legs into a water-filled trough. The volumes and timed deliveries of each reagent are controlled by "programing" the geometry and chemistry of the device. This is an example of staged reagent delivery.
Some simple one-dimensional porous devices have been used in research tools and commercial products for decades (e.g., paper chromatography and lateral flow immunoassays). New and much more sophisticated devices and systems are now made possible by forming porous materials in complex shapes in 2 and 3 dimensions. Because fluid flow can be controlled precisely without the need for either positive displacement of pressure-driven pumps, the movement of the fluids (sample and all the reagents) is programmed by the structure of simple, inexpensive, single-use pieces of paper. Just add the sample, and perhaps some water, and the paper does the rest.
Read more details at this website and at its links to detailed published reports, commercial manufacturers, and other sites.