Imagine checking your vitamin levels just by holding your morning coffee or orange juice—no needles, no batteries, and no extra effort.
Engineers at the University of California San Diego have created a small electronic sticker that can do exactly that.
The device sticks to the outside of a cup, collects tiny amounts of sweat from your fingertips, and uses that sweat to power itself while measuring your vitamin C levels. Within minutes, it sends the results wirelessly to a nearby device such as a laptop.
The new technology, described in Biosensors and Bioelectronics, could make health monitoring effortless and affordable.
“By turning everyday objects like cups or bottles into smart sensors, people can gain real-time insights into their health and wellness without changing a thing about their daily routine,” said Professor Patrick Mercier, one of the study’s senior authors.
He describes the concept as part of a new wave of “unawareables”—devices so unobtrusive that people forget they are even using them.
Vitamin C plays a vital role in maintaining a healthy immune system, repairing body tissues, and helping the body absorb iron. However, testing for it currently requires a blood draw and lab analysis, which can cost around $50 per test in the United States. These hurdles make frequent monitoring difficult, especially for people at risk of malnutrition or vitamin deficiencies.
The new sticker is made from a flexible, adhesive sheet that combines multiple technologies.
A porous hydrogel pad collects fingertip sweat, while a tiny biofuel cell underneath converts the chemical energy in that sweat into electricity. This powers a miniature circuit board and a built-in vitamin C sensor.
The sensor detects vitamin levels in the sweat, and the circuit board transmits the results using Bluetooth low energy.
One key advantage is that the device does not need physical activity to work. Fingertips contain thousands of sweat glands—up to a thousand times more than most other areas of the body—producing a steady flow of perspiration even when we are at rest. That natural moisture provides a continuous power source for the sensor.
Because it runs entirely on sweat, the sticker doesn’t require batteries and could be produced at very low cost—potentially just a few cents each. This could make it ideal for disposable or single-use health monitoring in clinics, homes, or developing regions.
The research team, led by Mercier and Professor Joseph Wang, tested the sticker by attaching it to disposable cups. It accurately tracked changes in vitamin C levels after participants drank orange juice or took supplements. The device even kept running for more than two hours using only sweat energy.
“This is an elegant step toward effortless, continuous monitoring of personal health,” said Wang. The team now plans to expand the technology to detect more nutrients and molecules, allowing cups, bottles, or even utensils to become simple, invisible health sensors.
