The effect of the back patch is based on the so-called Casimir effect (Hendrik Casimir 1949). This is a quantum physical effect that causes a force to act on two parallel, conductive plates, pressing them together. It was experimentally confirmed in 1956 by Yevgeny Lifschitz in the Soviet Union and in 1958 by Sparnaay in Eindhoven. A variation of the Casimir effect, the forward Casimir effect, or FCE for short, uses a special process to act on the material to be changed, which leads to structuring in the subatomic range. This new structure is then able to filter frequencies and thus enable the patch to work.