Nasa scientists have invented a bio-degradable drone made of fungus, bacteria and wasp saliva that would self-destruct if it crashes in an enemy territory to avoid detection.
The main body of the drone is composed of bio-degradable plastic made from a fungal material called mycelium.
After the main body was produced, the outer skin had to be made out of bacterial cellulose sheets, which were grown in a laboratory and takes on a sticky, leathery type consistency. It was then waterproofed, but this still had to allow for its immediate bio-degradability.
The solution was to coat the device in proteins, which had been cloned from paper wasps' saliva - the material they use to gel their nests together and waterproof them.
The drone would simply melt away the moment it crashed.
"No one would know if you have spilled some sugar water or if there had been an airplane there," Lynn Rothschild from NASA's Ames Research Center in California was quoted as saying in a New Scientist report.
The propellers, batteries and controls had to be separately sourced as "these are parts that cannot be replaced by biology", added Raman Nelakanti from the Stanford University in the US.
The drone completed its maiden flight at the International Genetically Engineered Machine competition in Boston, Massachusetts, recently.