>Absorbed on the red pad are antibodies that bind to the Covid-19 virus. They are also attached to gold nanoparticles (tiny particles of gold actually appear re

>Absorbed on the red pad are antibodies that bind to the Covid-19 virus. They are also attached to gold nanoparticles (tiny particles of gold actually appear red), which allow us to see where the antibodies are on the device. Gold appearing red when in small-enough particles is used to make stained glass: https://en.wikipedia.org/wiki/Stained_glass#Red_glass https://en.wikipedia.org/wiki/Stained_glass#Red_glass