Shoes to power Smartphones

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-Several years ago, Massachusetts Institute of Technology researchers pioneered conversion of the energy we produce by walking, through energy-harvesting footwear. That energy is usually lost as heat.
Trouble is, footwear-embedded harvesters so far have failed to produce the wattage required to keep a cellphone or a smartphone juiced, according to Tom Krupenkin, a mechanical engineering professor at the University of Wisconsin-Madison.
Cellphones require 1 to 2 watts during phone calls, and smartphones need up to 7 watts for Internet browsing, according to Krupenkin.
Now he and a colleague last week said in the journal Nature Communications that they have developed an embedded energy harvester that can generate up to 20 watts of power.