Tuft University in U.S. has developed the world smallest electric motor known as molecular Electric Motor as it size resembles of a molecule. Earlier the 200 nm motor was the smallest but know it will be replaced by the 1 nm electric motor.
The researchers at the Tuft University took the help of a scanning tunneling microscope. The microscope provided electric charge to butyl methyl sulphide that was placed on copper plate. All the atoms work as interlocking such that when one molecule rotates the adjoining molecule to start rotating .You can compare the size to with a single strand of human hair which is 60000 nm wide.
This motor can find application in medicine to engineering.