• Using nothing more than a puddle of resting water, the engine, which measures less than four inches on each side, can power LED lights and even drive a miniature car. Better yet, Sahin says, the engine costs less than $5 to build.
  • The key to Sahin's astonishing new invention is a new material that Sahin calls HYDRAs. HYDRAs are essentially thin, muscle-like plastic bands that contract and expand with tiny changes in humidity. A pinky finger-length HYDRA band can cycle through contraction and expansion more than a million times with only a slight, and almost negligible, degradation of the material.
  • Sahin also created a second engine with his HYDRAs—this one a turbine-style creation that uses the motion of bending HYDRAs to spin a wheel. Placed on top of a miniature car, the entire device slowly ekes forward—again, powered by nothing but evaporating water.

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