A team of researchers led by University of California, San Diego grad student Amay Bandodkar are developing a temporary tattoo that can be used by diabetics to monitor their blood glucose levels. These tattoos would represent a painless and more fun way for diabetics to do so without having to prick themselves.
Once the tattoo is applied to the patient, a mild electrical current is passed to their skin. This causes glucose-carrying sodium ions to move towards the electrodes. The tattoo's built-in sensor then measures the strength of the electrical charge produced by the glucose, rendering it able to measure glucose levels in the patient's bloodstream.
This temporary tattoo doesn't provide a numerical read-out of glucose levels, with a separate device currently being developed for that purpose.