Tattoo offers needle-free way to monitor sugar levels

In a promising step forward in non-invasive glucose-testing for diabetes patients, researchers have developed a temporary tattoo that both extracts and measures the level of glucose in the fluid in between skin cells.

"The readout instrument for patients will eventually have Bluetooth capabilities to send this information directly to the patient's doctor in real-time or store data in the cloud," said Indian-origin graduate student Amay Bandodkar, who along with his colleagues at the University of California, San Diego, made the breakthrough.

The researchers have described their flexible device -- which consists of carefully patterned electrodes printed on temporary tattoo paper -- in their report in the journal Analytical Chemistry.

A very mild electrical current applied to the skin for 10 minutes forces sodium ions in the fluid between skin cells to migrate toward the tattoo's electrodes.

These ions carry glucose molecules that are also found in the fluid.

A sensor built into the tattoo then measures the strength of the electrical charge produced by the glucose to determine a person's overall glucose levels.

The team applied the tattoo to seven men and women between ages 20 and 40 with no history of diabetes.

None of the volunteers reported feeling discomfort during the tattoo test and only a few people reported feeling a mild tingling in the first 10 seconds of the test.

According to Bandodkar, this "proof-of-concept" tattoo could pave the way for their research facility to explore other uses of the device, such as detecting other important metabolites in the body or delivering medicines through the skin.

The research team is also working on ways to make the tattoo last longer while keeping its overall cost down.

"Presently, the tattoo sensor can easily survive for a day. These are extremely inexpensive and can be replaced without much financial burden on the patient," Bandodkar said.

The sensor was developed and tested by Bandodkar and colleagues in professor Joseph Wang's lab at the nanoengineering department and the Center for Wearable Sensors at the Jacobs School of Engineering at UC San Diego.