Finger-prick blood tests are currently an unpleasant necessity for diabetics. Perhaps before too long, however, the blood glucose information gathered in those tests could be attained using something much more fun and painless than a lancet – a temporary tattoo.

Developed by a team led by University of California, San Diego grad student Amay Bandodkar, the flexible prototype device consists of precisely-patterned electrodes printed on temporary tattoo paper.

After the tattoo is applied to the patient, a "very mild" electrical current is also applied to their skin. This causes sodium ions in the fluid between their skin cells to migrate toward the electrodes. Those ions carry glucose molecules from the fluid with them. Using a built-in sensor, the tattoo then measures the strength of the electrical charge produced by that glucose. As a result, it's able to ascertain the glucose levels in the patient's bloodstream.

In lab tests, tattoos were applied to non-diabetic test subjects who then ate a carbohydrate-rich meal. Afterwards, the tattoos detected a spike in their glucose levels just as accurately as a traditional finger-prick test.

Although the tattoo currently doesn't provide a numerical readout of those levels, a separate device is being developed for that very purpose. The team is also working on making the tattoos more durable, as they currently last for about a day once applied to the skin – fortunately, they're very inexpensive.

A paper on the research was recently published in the journal Analytical Chemistry. Bandodkar's team is working in the lab of Prof. Joseph Wang, who has already developed a lactate-measuring temporary tattoo.

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