A wearable device powered by sweat offers a unique solution for continuous, personalized health monitoring, making it as simple as putting on a Band-Aid. Engineers at the University of California San Diego have created an electronic finger wrap that checks essential chemical levels, including glucose, vitamins, and medications, using the sweat from the fingertip that also powers the device.
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A wearable item that draws energy from sweat could make ongoing, personalized health monitoring as easy as using a Band-Aid. Engineers from the University of California San Diego have invented an electronic finger wrap that tracks critical chemical levels—like glucose, vitamins, and drugs—utilizing the sweat from the fingertip, which provides the energy needed for operation.
This innovation was detailed in a study published on September 3 in Nature Electronics by Joseph Wang’s research group, a professor within the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at UC San Diego.
The finger wrap fits tightly around the finger and harnesses an unexpected power source: fingertip sweat. Despite their small size, fingertips are highly efficient at producing sweat, boasting over a thousand sweat glands that can generate between 100 and 1,000 times more sweat than various other body regions, even when at rest. Consequently, this continuous release of perspiration—without needing physical activity—provides a dependable energy source to fuel the device, even during rest or sleep.
The device comprises several electronic elements printed on thin, flexible, and stretchable polymer material. Its design allows it to fit the shape of the finger while retaining enough durability to endure regular bending, stretching, and movement. “It combines advanced energy harvesting and storage components, with multiple biosensors housed in a fluidic microchannel, along with an appropriate electronic controller, all situated at the fingertip,” explained Wang.
At the core of its functionality are biofuel cells located at the point of contact with the fingertip. These cells are specifically designed to gather and convert the chemicals in sweat into electrical energy. This energy is then stored in a pair of stretchable batteries made from silver chloride and zinc, which energize a set of four sensors, each responsible for monitoring a particular biomarker: glucose, vitamin C, lactate, and levodopa—a medication for Parkinson’s disease. As sweat travels through tiny paper microfluidic channels to these sensors, the device assesses the levels of each biomarker while simultaneously drawing energy from the sweat it analyzes. A compact chip processes the sensor data and sends it wirelessly via Bluetooth low energy to a specially designed smartphone or laptop application.
“This is automatic health monitoring right at your fingertips,” stated Shichao Ding, a postdoctoral researcher and one of the study’s co-first authors within Wang’s team at the UC San Diego Jacobs School of Engineering. “Whether resting or asleep, the device continues to harness energy while monitoring biomarker levels.”
In practical trials, a participant wore the device throughout the day, tracking glucose levels during meals, lactate levels while working at a desk and exercising, vitamin C levels during orange juice consumption, and levodopa levels after eating fava beans, a natural source of this compound.
Ding and fellow co-first author Tamoghna Saha highlight that this device can be tailored to meet individual health requirements by identifying various biomarker sets. The team is also developing a closed-loop system capable of not only monitoring biomarkers but also delivering treatments based on the data collected. For instances like diabetes, such a device could continuously track glucose levels and automatically release insulin as required, subsequently evaluating the treatment’s effectiveness through further biomarker monitoring.
“The ultimate aim is to integrate autonomous power, sensing, and treatment into a single device,” Ding remarked.
