The Salmo Oncorhynchus (pink salmon from the Pacific) has rather curious habits. During the spawning period, the male parades in front of the coveted female by projecting his sperm in large quantities. Upon contact with water, the seed of the fish coagulates into millions of micro-droplets in suspension which then form a kind of screen in front of the female, making her invisible to other suitors. This very intriguing optical phenomenon was elucidated in 2018 by researchers from Murakami University: The spermatozoa of this salmon, perfectly spherical and transparent, capture light and then diffract it perpendicular to the focal point. The foreground (the female in this case) then completely disappears from view, the background remaining perfectly perceptible. A young English start-up was directly inspired by this flirt technique of fish to manufacture the first invisibility cloak in the world. The lenticular plastic film works on this same principle of focal diffraction, so it allows you to completely disappear into the background. The first applications are not envisaged for flirt, but in the military sector for camouflage. Man remains a wolf for man, not a salmon.

PS: This little April Fool's Day was imagined on the basis of articles which are totally true, not fake at all. On the one hand the research carried out by Tianjin University to produce a biodegradable plastic from salmon sperm, and on the other hand the launch by the start-up Invisibility Shield Co of an invisibility shield which is based on the principle lenticular films. More details here and here