Digital tattoo specifically refers to a 100-nanometer-wide sensor array implanted under the skin, just like tattoo dye. The sensor is encapsulated in an oil that ensures the entire unit holds together.
Within the implant, defined nanoparticles bind only to specific blood components, such as sodium and glucose. In the presence of an additive, the nanoparticles are uncharged and the presence of the target causes them to release ions, which appear as changing fluorescence. In the journal Integrative Biology, the researchers describe the process in detail.
The iPhone 4 add-on designed by Dubach uses the phone's camera to read color changes and then converts the results into measurable data. A plastic ring around the lens blocks ambient light, and a battery-powered blue LED light emits light that contrasts with the light from the sensor. The software utilizes the iPhone camera's built-in RGB filter to process light reflected from the sensor.
Blue LED lights were chosen because initial tests showed that while other colors of light were blocked by the iPhone's built-in optical filter, blue light exploited the iPhone's built-in RGB filter to accurately process data. . The blue LED light is powered by a 9-volt battery on the phone and works in conjunction with the sensor's red-shifted fluorescence, which allows red light to pass through the skin. Currently, the data collected by the iPhone still requires an auxiliary machine for processing, but Dubach said that using the iPhone to complete all work will become a reality in the near future, and related programs are also under development.
Clark hopes that nanoparticles and smartphones can be used to complete all the tasks that a clinical analyzer can do. This is an important step on the road to personalized medicine. If it becomes a reality, diabetics and athletes will be able to perform their own tests and obtain relevant statistics without the need for large and expensive medical equipment. Currently, digital tattoo testing is still in its early stages and has not yet been tested on humans. Experiments on mice show the technology's potential. It’s worth mentioning that mice have thinner skin than humans.