By Jocelyn Solis-Moreira

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Reviewed by Chris Melore

Research led by Professor Joseph Wang, University of California-San Diego

Sep 13, 2024

FACT CHECKED

SAN DIEGO — Instead of waiting weeks for test results, what if you could have all your health information at your fingertips? Scientists in California have taken this question literally, as they have created an electronic device capable of 24-hour monitoring of glucose, lactate, and vitamin C levels. The wearable device wraps like a snug bandage on your finger and is powered by your fingertips’ sweat.

Out of all the areas on the human body, sweat is mainly secreted through the fingertips. They contain over a thousand sweat glands, producing 100 to 1,000 times more sweat than other areas, even when a person is not exercising. Scientists sought to take advantage of this natural sweat producer, converting sweat into a constant energy source for its new device, as discussed in their latest study in Nature Electronics. The sweat-powered wearable allows for continuous monitoring even during sleep and periods of inactivity.

“This is automatic health monitoring at your fingertips,” says study co-author Shichao Ding, a postdoctoral researcher at the University of California-San Diego’s Jacobs School of Engineering, in a media release.

How it works

The design is like a bandage. It is made of polymer material, which gives the device a thin, stretchable, and flexible design. Despite its sleek design, the sweat-powered device is made up of several electronic components. It contains biofuel cells placed where the device touches the fingertips. Each cell is made to collect and convert the chemicals in sweat into electricity. The electricity is kept in a pair of stretchable, silver chloride-zinc batteries. These batteries contain four sensors for surveilling glucose, vitamins, and certain drugs.

Fingertip sweat is absorbed through tiny paper microfluidic channels connected to the biometric sensors. The device analyzes the biomarker levels while simultaneously converting sweat into energy to fuel the device. A small chip takes the signals from the sensors and sends them via Bluetooth to an app.

“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,” says Joseph Wang, a professor at UC San Diego and co-author of the study.

Health data at your fingertips

So far, the researchers have successfully monitored glucose, vitamin C, and lactate levels. They have also detected levels of levodopa, a drug used for treating Parkinson’s disease. One person spent the entire day with the device on their finger, and the device captured lactate levels while sitting at a desk and during exercise, vitamin C levels when they drank orange juice, and levodopa levels after eating fava beans. These beans are a natural source of the compound.

The bandage-like device shows we’re one step closer to a world of personalized medicine. If doctors have biomarker information readily available, the device can make diagnoses of ailments and treatments more customizable. For example, people with diabetes could keep track of their glucose levels and insert insulin as needed.

“Autonomous power, sensing, and treatment all in one device—that’s the ultimate goal,” Ding concludes.

Paper Summary

Methodology

This study developed a fingertip-wearable microgrid system to monitor various metabolites in sweat, such as glucose, vitamin C, lactate, and levodopa. The system was powered by bioenergy harvested from sweat through biofuel cells (BFCs) and stored in small, flexible batteries. The device included sensors that analyzed sweat to measure key biomarkers in real time. The sweat was collected using an osmotic pump, which naturally pulled sweat to the sensors. The fingertip microgrid combines low-power electronics with wireless transmission, allowing continuous health monitoring without the need for bulky batteries or external energy sources.

Key Results

The study found that the fingertip device worked by using sweat to generate energy and monitor different chemicals in the body. When someone wore the device, it collected sweat and used that sweat to power tiny sensors. The sensors could detect important health markers like blood sugar (glucose), vitamin C, and others. The device was able to send this information to a phone or computer wirelessly. Overall, the device successfully tracked changes in these chemicals over time, showing that it could help monitor health in a simple, easy-to-use way.

Study Limitations

First, the study relies on sweat for energy, which may not be consistently available during periods of low perspiration. This could limit the device’s effectiveness in cooler environments or during sedentary activities. Additionally, while the system can detect certain biomarkers, the range of detectable substances is still limited. Future iterations of the device may need to integrate more sensors or improve the existing ones to detect a broader range of health indicators. The system also requires further testing in real-world conditions to confirm its reliability over long periods of use.

Discussion & Takeaways

This study demonstrates the potential for a self-powered wearable device that can continuously monitor health markers. By using sweat as both a power source and a medium for detecting chemicals in the body, the system could help people track their health in real time without needing bulky batteries or frequent recharging. The findings suggest that such devices could be useful for everyday health monitoring, particularly for people with conditions like diabetes, where regular tracking of glucose levels is important. However, improvements in device durability and sensor capabilities will be needed to make it widely practical.

Funding & Disclosures

The research was conducted by a collaborative team from the University of California, San Diego, and Samsung Electronics. Some of the researchers have affiliations with the university’s Department of Nanoengineering and the Department of Electrical and Computer Engineering. The study was funded by internal grants from the university and external support from Samsung. There are no disclosures of potential conflicts of interest from the researchers involved.