Using miniaturized laser technology, a tiny sensor has been built at the Vienna University of Technology which can test the chemical composition of liquids, like oxygen in blood.
Just a drop is enough to test the chemical composition. Credit: TU Vienna.
The light is emitted by the laser (top), transported on the plasmonic waveguide (blue) and hits the detector (bottom right). How much of it is absorbed depends on the chemical composition of the liquid.