A team headed by Joseph Wang at the University of California, Santa Barbara, has developed a chemical biosensor to measure increasing lactate levels in the sweat of athletes. The sensor comes in the form of a wearable tattoo,containing an enzyme that oxidizes the lactate releasing electrons in the process. These electrons can then drive thin film electronics in the tattoo giving an indication when the athelete is about to “hit the wall”. Collin Barras, from New Scientist wrote this piece.
Link to the journal article.