Like other biofluids, sweat contains a wealth of information about what’s going on inside the body. However, collecting the fluid for analysis, usually by dripping or absorbing it from the skin’s surface, can be time-consuming and messy. Now, researchers have developed a bandage-like biosensor that both collects and—in conjunction with a smart phone—analyzes sweat. The device, which could someday help diagnose diseases, is reported in ACS’ journal Analytical Chemistry.