Canadian researchers have developed a sensor, shaped like a smiley face, which could help doctors detect metabolic problems in patients by attaching it to their skins.

"We wanted a design that could conceal the electrodes," says Vinci Hung, doctoral candidate in physical & environmental Sciences at University of Toronto Scarborough, who helped create the new sensor. 

The new tattoo-based solid-contact ion-selective electrode (ISE) is made using standard screen printing techniques and commercially available transfer tattoo paper, the same kind of paper that usually carries tattoos of Spiderman or Disney princesses.

By using different sensing materials, the tattoos can also be modified to detect other components of sweat, such as sodium, potassium or magnesium, all of which are of potential interest to researchers in medicine and cosmetology.