Because human sweat contains many of the same biomarkers as blood, it can be used as a substitute in certain instances. However, analysing sweat using a skin patch doesn't hurt like a needle, and the results can be obtained far quicker. For fitness purposes, the patch could give an early warning that it's time for the wearer to hydrate, and with additional research, Rogers envisions a more sophisticated purpose, such as real-time monitoring of how the body adjusts during military training, or even to screen people for diseases such as diabetes or cystic fibrosis. The patch’s functionality is simple: stick the patch on your skin and start moving. Tiny channels collect the wearer’s perspiration and route it to different compartments where it interacts with chemicals that change color to reflect sweat loss, the perspiration acidity level, and concentrations of chloride, glucose and lactate. Designed for one-time use, it can even send its findings to your smartphone.