By Damien Gayle | DailyMail.co.uk

Medical sensors concealed within temporary tattoos could be used by coaches to fine-tune their athletes’ training, a new study claims.

Researchers at University of California San Diego invented the sensor, which comes in a thin flexible transfer adorned with a cheerful smiley-face design.

’We wanted a design that could conceal the electrodes,’ says Vinci Hung, a PhD candidate in the University of Toronto Scarborough’s Department of Physical & Environmental Sciences, who worked as part of the team during a foreign exchange trip earlier this year.

The temporary tattoo hides medical sensors that can can detect changes in the skin’s pH levels caused by metabolic stress, which could be used by sports coaches and medical researchers

This graphic illustrates the screen-printing process used to create the transfer sensors on commercially available transfer tattoo paper

Sano Intelligence is in the testing phase of a smart tattoo that reads a wearer’s blood markers. The application would be particularly useful for diabetics, who need to keep strict control over their blood sugar levels and often have to resort to finger-prick tests to determine if those levels are within normal range. The Sano patch would not only allow them to forgo the pain of finger-pricks, but the constant hassle of dragging around testing devices and interrupting daily activities to draw their own blood.

And Boston-based MC10 announced earlier this year that it would soon release its own “stretchable electronics” patch, that can be applied internally to human organs, or externally to human skin, or clothing, depending on what needed to be monitored. The stick-on’s ability to remain flexible while reading vital signs means that it could effectively gauge the function of specific organs, track brain processes, and monitor more mainstream functions like heart rate, blood oxidation and body hydration.