Tiny gadgets pick up energy for free
A few years ago, just to show that they could do it, Paul Wright and his mechanical engineering students mounted a temperature sensor under a staircase at the University of California, Berkeley and fed its readings into the stairwell's thermostat. It was not an especially difficult exercise—except that this sensor, which was about the size of a quarter, had no power cord or batteries. Instead, the device extracted the energy it needed from the vibrations that shook the wooden staircase as students clomped up and down between classes.
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