More than 300,000 children in Africa are born with sickle cell disease each year. Although there are inexpensive treatments, many of these children die because they haven’t been diagnosed. Now, researchers led by Harvard University’s George M. Whitesides have developed a rapid, low-cost method for diagnosing sickle cell disease in resource-challenged areas (Proc. Natl. Acad. Sci. USA 2014, DOI: 10.1073/pnas.1414739111). Unlike standard sickle cell diagnostics, such as hemoglobin electrophoresis and high-performance liquid chromatography, the new method requires only simple equipment, such as a battery-powered centrifuge. The test makes use of mixtures of polymers that form immiscible phases in water. These polymers are able to separate particles by density. Upon centrifugation, the high-density red blood cells that characterize sickle cell disease sink to the bottom of a thin tube filled with the polymer mixture, where they are visible. No special medical training is required to make the diagnosis. The test, which takes about 12 minutes to perform and costs around 50 cents, requires 5 μL of blood, which can be obtained from a finger stick.