Diabetics often prick their fingers up to eight times a day to check their blood sugar. Researchers have long looked for a solution that provides constant monitoring without being so invasive, and researchers at the University of California San Diego have come up with a new needle-free design that could turn out to be less painful, yet just as effective, as the finger-prick method.

The UCSD team printed electrodes onto standard temporary tattoo paper and paired it with a sensor. After each meal, the electrodes generate a current for about 10 minutes. The current draws the glucose—a type of sugar that diabetics have trouble breaking down—up near the skin's surface, allowing the device to read the glucose levels. The glucose is carried by sodium ions, which have a positive charge. By measuring how strong the charge is just under the skin, the sensor estimates how much glucose is in the bloodstream.

The researchers tested the device on seven non-diabetic people and found that the tattoo's glucose measurements were consistent with the traditional finger-prick testing method. Amay Bandodkar, a nanoengineering graduate student at UCSD, who worked on the study, said in a news release that each temporary tattoo would work for up to a day, and would cost users only a few cents per tattoo.