How does this tattoo work? For instance, it will be able to monitor the amount of lactate present, which is a kind of substance that can be found in sweat, and the levels get more concentrated as the amount of activity increases. There is a good reason for athletes and certain medical patients to keep an eye on lactate levels, and current testing will require an invasive blood test during an exercise session. Needless to say, having a “tattoo” (sensor) makes it less painful, and there will be an enzyme on the sensor itself which collects electrons from lactate, resulting in a tiny electric current. It might not amount to much, but when collected, it could be worth producing an accessory that will harness such power to juice up a depleted battery down the road.
It is said that the highest amount of energy which has been produced by a single person during the test ended up at 70 microWatts per square centimeter of skin, and there is further research being made to increase the efficiency of such a system.