Finger Wrap Monitors Health

Medical Design Briefs INSIDER

This finger wrap is powered by the wearer's fingertip sweat — and also monitors levels of glucose, lactate, vitamin C, and levodopa in that same sweat. (Credit: Shichao Ding)

A sweat-powered wearable has the potential to make continuous, personalized health monitoring as effortless as wearing a Band-Aid. An electronic finger wrap monitors vital chemical levels — such as glucose, vitamins, and even drugs — present in the same fingertip sweat from which it derives its energy.

The device, which wraps snugly around the finger, draws power from an unlikely source — the fingertip’s sweat. Fingertips, despite their small size, are among the body’s most prolific sweat producers, each packed with over a thousand sweat glands. These glands can produce 100 to 1000 times more sweat than most other areas of the body, even during rest. This constant trickle of natural perspiration — without any stimuli or physical activity — offers a reliable energy source, fueling the device even during periods of inactivity or sleep.

The device is constructed from several electronic components printed onto a thin, flexible and stretchable polymer material. Its design allows it to conform to the finger while being durable enough to withstand repeated bending, stretching and movement. “It is based on a remarkable integration of energy harvesting and storage components, with multiple biosensors in a fluidic microchannel, along with the corresponding electronic controller, all at the fingertip,” said Wang.

Central to its operation are biofuel cells that are positioned where the device contacts the fingertip. These cells have been specially engineered to efficiently collect and convert chemicals in sweat into electricity. This electricity is stored in a pair of stretchable, silver chloride-zinc batteries, which power a suite of sensors — four in total — each tasked with monitoring a specific biomarker: glucose, vitamin C, lactate and levodopa, a drug used for treating Parkinson’s disease.

As sweat is wicked through tiny paper microfluidic channels to these sensors, the device analyzes the biomarker levels, all while drawing energy it needs from the very sweat it’s sampling. A small chip processes signals from the sensors and wirelessly transmits the data via Bluetooth low energy to a custom-designed smartphone or laptop application.

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