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Scientists dreamed up a disposable tattoo made of pencil and paper that could monitor blood glucose, observe sleep patterns, and deliver medication. It sounds made up, right? Well, they built it, and it works.
Their invention could bring crucial health services to poor and remote areas of the world and make home health care easier and more affordable.
Study authors explain that by using widely available copy paper and pencils composed of 93% graphite, health care workers could save costs and production time over available biomedical sensors.
“The conventional approach for developing an on-skin biomedical electronic device is usually complex and often expensive to produce,” said Zheng Yan, an assistant professor at the University of Missouri. “In contrast, our approach is low-cost and very simple.”
This no-frills approach to monitoring the body’s many health signals could be used in several ways. Different tattoo designs could check a patient’s temperature, monitor muscle responses, and test the pH balance of sweat, for example.
How It Works
The reason these simple tattoos work comes down to electricity. Pencils are made with different combinations of wax, clay, and graphite. And it’s that graphite that makes the difference.
Researchers found that pencils made with 90% graphite or more can conduct electricity. And they found the ideal ratio of graphite to be 93%.
These drawings work best when used with a spray-on adhesive, Yan said. That holds them tight against the skin.
With the ability to conduct electricity, these specially-designed tattoos can be turned into antennas and circuits that transmit specific information to aid health care workers in diagnosing and monitoring patients.
Why Simple Paper and Pencil May Be Best
Besides the low cost, a paper-and-pencil monitor could have other advantages for health care.
For one, it’s painless. An important goal of diabetes control is keeping blood sugar within a healthy range, says MedicineNet medical author Melissa Conrad Stöppler, MD. To do this, people with diabetes must prick their fingertip for a blood test before and after meals, as well as before bed, she says.
In contrast, a home-application tattoo wouldn’t require any drawn blood.
Another big advantage is for the environment. The paper-based sensors are biodegradable and easily dissolve in water. That has the potential to ease landfills of the burden of some broken and outdated medical equipment.
Indeed, as part of their paper published in the Proceedings of the National Academy of Sciences, researchers demonstrate how their tattoos can dissolve in water after a few minutes of stirring.
Another useful advantage is how flexible these devices could potentially be. The researchers provide a variety of possible monitoring applications, including:
- skin temperatures
- alpha, beta, and theta rhythms
- instantaneous heart rates
- respiratory rates
- sweat pH
- uric acid
For the future, Yan says his research group would continue developing and testing their devices for monitoring electrical and biochemical signals, as well as body temperature.