Battery-free sticker delivers real-time vitamin C readings from sweat

Researchers at the University of California San Diego have developed a battery-free, flexible electronic sticker that measures vitamin C levels from fingertip sweat by attaching to the outside of any drinking cup. The sticker collects microscopic sweat through a porous hydrogel pad and uses a built-in biofuel cell to convert sweat chemicals into electricity, powering a vitamin C sensor and a Bluetooth low energy circuit board. This enables real-time, wireless transmission of vitamin C data to nearby devices without the need for batteries or external power sources. This innovation offers a low-cost, noninvasive alternative to traditional vitamin C testing, which typically requires blood draws and expensive equipment. The sticker’s ability to harvest power from the high density of sweat glands on fingertips allows continuous operation for hours, making it suitable for disposable, widespread use, especially in communities with limited medical access. Demonstrations showed accurate tracking of vitamin C changes after supplement or orange juice intake, highlighting its potential for effortless, frequent health monitoring integrated into everyday objects. Future developments aim to expand the