All that rubbing of your backpack straps on your shoulders may be put to good use, now that researchers have designed a novel type of energy harvesting backpack. The pack has straps made of a piezoelectric material that can convert the mechanical strain on the straps into electrical energy that may power or recharge portable electronics.
The piezoelectric backpack straps are the latest innovation in the area of "energy harvesting," where otherwise-wasted, ambient energy is converted into electrical energy to prolong the life of electronics. Mechanical engineers Jonathan Granstrom and Joel Feenstra from Michigan Technological University, Henry Sodano from Arizona State University, and Kevin Farinholt from NanoSonic, Inc., have published their results in a recent issue of Smart Materials and Structures.
Source: Granstrom, Jonathan, Feenstra, Joel, Sodano, Henry A., and Farinholt, Kevin. “Energy harvesting from a backpack instrumented with piezoelectric shoulder straps. Smart Materials and Structures. 16 (2007) 1810-1820.