BREAKING DOWN A WASTE CALLED BILIRUBIN often overtaxes newborns’ livers—it builds up, causing jaundice. A baby might need to spend several days under a bili light—a blue light that alters bilirubin to make it water-soluble (and thus excretable). Yet many developing-world hospitals do not have this equipment because of its high cost (more than $5,000). In response, Duke University engineering students invented the BlueRay (here, in experimental use in Honduras), which uses light-emitting diodes instead of more costly bulbs and will sell for about $500.