Velcro
Swiss electrical engineer George de Mestral invented his first touch fastener when, in 1941, he went for a walk in the woods and wondered why Burdock seeds clung to his coat and dog. He discovered it could be turned into something useful. He patented it in 1955 and subsequently refined and developed its practical manufacture until its commercial introduction in the late 1950s.
Helicopter rotor
The use of a rotor for vertical flight has existed since 400 BC in the form of the bamboo-copter, an ancient Chinese toy. The bamboo-copter is spun by rolling a stick attached to a rotor. The spinning creates lift, and the toy flies when released. The philosopher Ge Hong's book the "Baopuzi" (Master Who Embraces Simplicity), written around 317, describes the apocryphal use of a possible rotor in aircraft: "Some have made flying cars [feiche 飛車] with wood from the inner part of the jujube tree, using ox-leather (straps) fastened to returning blades so as to set the machine in motion." Leonardo da Vinci designed a machine known as an "aerial screw" with a rotor based on a water screw. The Russian polymath Mikhail Lomonosov developed a rotor based on the Chinese toy. The French naturalist Christian de Launoy constructed his rotor out of turkey feathers. Sir George Cayley, inspired by the Chinese toy in his childhood, created multiple vertical flight machines with rotors made of tin sheets. Alphonse Pénaud would later develop the coaxial rotor model helicopter toys in 1870, powered by rubber bands. One of these toys, given as a gift by their father, would inspire the Wright brothers to pursue the dream of flight.