First, suitable antibodies are attached to the biochip, which can hold the virus in question. If the examined sample contains viruses, these are fixed there. Then another very special type of antibody comes into play: They can move freely, but have a nanoparticle made of gold. These antibodies bind to the fixed virus, so each virus is marked with a tiny piece of gold.
This marking is now allowed to grow – with the help of a silver solution. The silver atoms attach to the gold, and wherever there is a virus, a silver complex with a golden core forms. After a short time, this precious metal structure is so large that it creates an electrical contact between two electrodes. Suddenly electricity flows, a lamp lights up – and that is proof that there must have been a virus between the electrodes.