Nike recently filed a patent for a power-lacing system for a sneaker. Originally seen in the movie Back to the Future II, the lacing system employs machinery that takes advantage of magnetic fields. In order to create a power-lacing system, a small motor must be incorporated into the shoe. This electric motor takes advantage of magnetism and electromagnetism. The way any electric motor works is by using an electromagnet situated between the north and south poles of two permanent magnets. The electromagnet (which in simplified form is a piece of iron wrapped in a wire) is then electrified, and north and south poles are created. The electromagnet then spins about the fixed center to align with the poles of the permanent magnets.
The magnet does not stop when it is immediately aligned because it has mass and acceleration, and therefore momentum. The magnet then passes the point at which it is perfectly aligned.
In order to maintain rotation, the current in the wire is then reversed, resulting in a switching of the poles. This is continued and the electric motor then continues to spin, turning electrical energy into mechanical energy. The magnet is attached to a drive shaft, which spins.