In diagnostics in the developing world, ease of use, simple storage and cost per test are critical, and few things are cheaper and simpler than color-based tests printed on slips of paper. Boston-based not-for-profit Diagnostics for All uses patterned paper technology to create printed paper-based assays for the 60% of the world's population that is out of reach of urban hospitals and medical infrastructure.
Diagnostics for All's patterned paper technology uses a water-repellant "ink" to print channels and assay wells on a piece of paper about the size of a postage stamp, with reagents in the wells. Biological samples, such as blood, urine or sweat, wick through the paper to the wells and the user compares the color changes with the reference scale on the paper.
Researchers in Washington could have made the manufacture of paper diagnostics even easier and cheaper, by using a simple industrial solvent, divinyl sulfone, to make ordinary paper "sticky" to molecules from sugars to DNA. The upside of divinyl sulfone is that it is cheap, easily available and known to chemists.
The advantages of paper diagnostics are that the materials are cheap and easily obtained, and the diagnostics are simple to manufacture. The tests can be distributed easily without a cold chain in place, even by mail. No sample preparation is needed, and the results can be read and interpreted without the need for extra devices by people without extensive medical training. And once the test is completed, the paper can just be burned.