Though traditionally the preserve of hipsters, sailors and tough guys, tattoos may soon be attracting a new horde of fans. Researchers at the Technical University of Munich in Germany have created permanent tattoos that change colour according to changes in a range of biomarkers such as blood glucose levels or pH levels that could be used to monitor health.
The team developed a series of colour-changing chemical sensors and placed them directly into the dermis, a roughly one-millimetre-thick layer of tissue that hosts nerves, blood vessels, and hair follicles and lies directly under the surface of a model skin patch made of pig skin. They were then able to estimate the concentrations of various chemicals in the skin using smartphone photos of the sensors.
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The first sensor they created was a pH indicator made from the dyes methyl red, bromothymol blue, and phenolphthalein. When injected into a model skin patch the resulting tattoo turned from yellow to blue when the pH was adjusted from five to nine.
They also created two other sensors to monitor the levels of glucose and albumin – a transport protein found in the blood. High glucose levels in the body are common in sufferers of diabetes, whereas a drop in albumin levels can indicate liver or kidney failure.
The glucose sensor changed from yellow to dark green depending on the concentration of glucose present, while the albumin sensed turned from yellow to green depending on the albumin levels.
The tattoos could provide a simple, low-cost means of monitoring patients’ health, the researchers say. Further development of the technique could lead to the production of more sensors that could monitor the levels of bacteria or viruses or levels of dehydration, they say.
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