Nature likes spirals: Whirlpools, hurricanes, the way sap flows up a plant, even the shape of a human heart. Inventor Jay Harmon used this archetypal shape from nature to design a “frozen whirlpool," useful as either the rotary part of a machine or as a pump. It can stir 10 million gallons of water with a couple of light bulbs worth of power. Today, Harmon’s design keeps hundreds of water storage tanks in the U.S. and other countries clean without the use of chlorine or other chemicals.