South Koreans may soon be able to carry a device inside their own bodies in the form of a bespoke tattoo that automatically alerts them to potential health problems, if a science team's project bears fruit.

Designs drawn on the skin using "electronic tattoo ink" made of liquid metal and carbon nanotubes can help monitor heart rates and other vital health signs, according to South Korean researchers.

The technology is still in its early phases, but a team of scientists at the Korea Advanced Institute of Science and Technology (KAIST) hope that one day the technology could offer a personalised and non-intrusive way for individuals and doctors to monitor health conditions.

The tattoo can be linked to electrocardiogram (ECG) device to monitor heart activity.

The ink effectively works by creating an electric circuit on the skin. It can be linked to electrocardiogram (ECG) devices to monitor heart activity, sensors that analyse sweat, as well as acting as heaters for physiotherapy purposes.

"Compared to previous devices (e-tattoos) which are patch type, we can apply it directly to the skin… it's much more comfortable to the user," said Steve Park, a materials science and engineering professor at KAIST who co-led the team with Ph.D. candidate Lee Gun-hee.

To make the ink, the researchers used liquid-metal particles based on gallium, a soft, silvery metal also used in semiconductors or in thermometers as a non-toxic alternative to mercury. Platinum-decorated carbon nanotubes help conduct electricity while providing durability.

Park stressed that it is considered biocompatible, meaning it does not harm living tissue.

"When it is applied to the skin, even with rubbing the tattoo doesn't come off, which is not possible with just liquid metal," Park said. The ink does come off with soap, he added, and dries on the skin in less than 10 seconds.

However, the current technology is limited by the fact that it still requires wiring to acquire data, said Park.

"In the future, what we hope to do is connect a wireless chip integrated with this ink, so that we can communicate, or we can send signal back and forth between our body to an external device," he said.