What are Albert Einstein's lesser-known inventions?

The vast majority of Albert Einstein's work was theoretical, and the only invention he ever patented was the Einstein refrigerator. He was also involved in the creation of the atomic bomb.

The Einstein refrigerator, which Einstein developed with physicist Leo Szilard, is a method of refrigeration powered by a flame burner, butane and ammonia. It uses much less energy than common methods of refrigeration and was patented by Einstein in 1930. Einstein did not work on the team that ultimately created the atom bomb, but his Theory of Relativity was crucial to its development. Szilard and Einstein wrote to President Roosevelt urging the creation of the bomb after Germany succeeded in splitting the atom.